"CF Bike Shatters" - continued
jim beam
limited screen real estate - i'm starting a new thread.
peter cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>
>>> Find one to support your claim that carbon fibers aren't brittle
>>> & I'll read along.
>>
>> learn about yield before you /dare/ to lecture on deformation,
>> bullshitter.
>
> Oh please. Typical "jim beam" switcharoo. We're talking about
> fracture (see thread title).
you're confusing fracture of brittle materials with fracture of ductile
materials - the two mechanisms are completely different. but hey that
wouldn't be the first time that ignoring fundamentals suits your
argument, right?
> Carbon fibers are brittle.
in isolation, they are. so is any high strength material. but cfrp is
not. what's why we use it!
> They elongate
> only between 0.8 - 1.4% before fracture in tension. E-glass is >3x
> that, 6061 is ~20x that.
you're mixing apples with oranges. carbon fiber [and glass fiber] have
no deformation mechanism, no dislocation function. so they have no
ductility. so they are "brittle". again, this is not to be confused
with the behavior of their composites.
for glass and carbon, their stress/strain graphs are much extended -
what would be the hooke's law region of a ductile material.
> If you have a source (other than yourself)
> that says otherwise, I'm all ears.
go to a library!
you can also look at this:
http://www.flickr.com/photos/38636024@N00/1208725721/
the "x" points are the "failure" points for all the materials since
onset of yield is failure.
>
> If you take the often cited 6x ultimate yield strength of CF, derate
> it by the 4 plies (minimum, 0, 90 +-45) you need for isotropy, plus
> the ratio of fiber to epoxy, you come out with nothing special wrt
> overall strength.
eh? why do you need isotropy??? oh, you're trying to force an argument
where none exists. my bad.
> That's why there isn't much difference in CF vs Al
> handlebars and seatposts (except price).
incorrect. it's because it's relatively cheap fiber, relatively
imprecise manufacturing and a generous safety margin.
> It's only when you exploit
> anisotropy that CF makes sense, but then you're stuck with lack of
> impact resistance and brittle failure as a trade off.
but you have that kind of trade off with /any/ high strength material,
even steel. the higher the strength, the more brittle.
> CF is great for
> some apps, marginal for others and crappy for the rest. It's an
> engineering thing.
wow. condescension, massive over-generalization and naivety all in one.
Peter Cole
> the "CF Bike Shatters" thread is now too deep for me to follow on my
> limited screen real estate - i'm starting a new thread.
>
> peter cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>
>>>> Find one to support your claim that carbon fibers aren't brittle
>>>> & I'll read along.
>>>
>>> learn about yield before you /dare/ to lecture on deformation,
>>> bullshitter.
>>
>> Oh please. Typical "jim beam" switcharoo. We're talking about
>> fracture (see thread title).
>
> you're confusing fracture of brittle materials with fracture of ductile
> materials -
I'm not "confusing" them, I'm comparing them.
>> Carbon fibers are brittle.
>
> in isolation, they are. so is any high strength material. but cfrp is
> not. what's why we use it!
I don't know who "we" is.
You're absolutely wrong about CFRP. You can't discuss an inherently
anisotropic material without qualifying by fiber orientation (pretty
much my whole point).
A unidirectional fiber composite will have characteristics very much
like those of the reinforcing fiber when loaded on-axis. Off-axis, those
properties change rapidly, becoming essentially those of the matrix at
90 degrees.
>
>> They elongate
>> only between 0.8 - 1.4% before fracture in tension. E-glass is >3x
>> that, 6061 is ~20x that.
>
> you're mixing apples with oranges. carbon fiber [and glass fiber] have
> no deformation mechanism, no dislocation function. so they have no
> ductility. so they are "brittle". again, this is not to be confused
> with the behavior of their composites.
On-axis, the behavior of composite and fiber are very similar.
> for glass and carbon, their stress/strain graphs are much extended -
Extended from what?
> what would be the hooke's law region of a ductile material.
I give up, what?
>
>> If you have a source (other than yourself)
>> that says otherwise, I'm all ears.
>
> go to a library!
> you can also look at this:
> http://www.flickr.com/photos/38636024@N00/1208725721/
> the "x" points are the "failure" points for all the materials since
> onset of yield is failure.
Citing yourself again? Why am I not surprised. You're never going to
learn anything that way.
>> If you take the often cited 6x ultimate yield strength of CF, derate
>> it by the 4 plies (minimum, 0, 90 +-45) you need for isotropy, plus
>> the ratio of fiber to epoxy, you come out with nothing special wrt
>> overall strength.
>
> eh? why do you need isotropy??? oh, you're trying to force an argument
> where none exists. my bad.
No, I'm trying to compare "apples to apples" -- material suitability for
isotropic loading.
>> That's why there isn't much difference in CF vs Al
>> handlebars and seatposts (except price).
>
> incorrect. it's because it's relatively cheap fiber, relatively
> imprecise manufacturing and a generous safety margin.
How do you know what the safety margin is?
How do you know what the fiber is?
How do you know what the process is?
In the past, you've made the rather obvious point that it's silly to
talk about metals without knowing the specific alloy. Now, you're making
gross generalizations about a material which has much greater
parameterization.
As far as I know, no component or frame manufacturer publishes layup
schedules. If you have any, please share. You claimed that a "visit to a
bike shop" would allow one to learn this. I fail to see how visual
inspection of a composite part would reveal the layup schedule. At best,
you could perhaps get a little information on the outermost ply, often,
not even that.
>> It's only when you exploit
>> anisotropy that CF makes sense, but then you're stuck with lack of
>> impact resistance and brittle failure as a trade off.
>
> but you have that kind of trade off with /any/ high strength material,
> even steel. the higher the strength, the more brittle.
You're missing the point about anisotropy.
>> CF is great for
>> some apps, marginal for others and crappy for the rest. It's an
>> engineering thing.
>
> wow. condescension, massive over-generalization and naivety all in one.
No, just engineering basics. With CF bars and posts, you get (more
expensive) parts with similar weights. You also get susceptibility to
damage from clamping pressure and/or impact. Crappy (yet popular)
applications.
jim beam
> jim beam wrote:
>> the "CF Bike Shatters" thread is now too deep for me to follow on my
>> limited screen real estate - i'm starting a new thread.
>>
>> peter cole wrote:
>>> jim beam wrote:
>>>> Peter Cole wrote:
>>>
>>>>> Find one to support your claim that carbon fibers aren't brittle
>>>>> & I'll read along.
>>>>
>>>> learn about yield before you /dare/ to lecture on deformation,
>>>> bullshitter.
>>>
>>> Oh please. Typical "jim beam" switcharoo. We're talking about
>>> fracture (see thread title).
>>
>> you're confusing fracture of brittle materials with fracture of
>> ductile materials -
>
> I'm not "confusing" them, I'm comparing them.
but you are confusing them - you're not differentiating between ductile
and brittle - and that's pretty damned fundamental.
>
>
>>> Carbon fibers are brittle.
>>
>> in isolation, they are. so is any high strength material. but cfrp is
>> not. what's why we use it!
>
> I don't know who "we" is.
prick.
>
> You're absolutely wrong about CFRP. You can't discuss an inherently
> anisotropic material without qualifying by fiber orientation (pretty
> much my whole point).
eh? /you/ are defeating your own argument!!! first you b.s. about
"isotropic" cfrp, now you're admitting that it's inherently not!!!
>
> A unidirectional fiber composite will have characteristics very much
> like those of the reinforcing fiber when loaded on-axis. Off-axis, those
> properties change rapidly,
they don't just "change rapidly", they're completely different. that's
why it's anisotropic!!!
> becoming essentially those of the matrix at
> 90 degrees.
mince words whydontcha
>
>>
>>> They elongate
>>> only between 0.8 - 1.4% before fracture in tension. E-glass is >3x
>>> that, 6061 is ~20x that.
>>
>> you're mixing apples with oranges. carbon fiber [and glass fiber] have
>> no deformation mechanism, no dislocation function. so they have no
>> ductility. so they are "brittle". again, this is not to be confused
>> with the behavior of their composites.
>
> On-axis, the behavior of composite and fiber are very similar.
but composites rarely if ever use solely uniaxial layup. you're trying
to twist the facts again.
>
>
>> for glass and carbon, their stress/strain graphs are much extended -
>
> Extended from what?
compared to the ductile materials with which you're confused.
>
>> what would be the hooke's law region of a ductile material.
>
> I give up, what?
that wasn't a question. i missed the word "from" - which you'd have
spotted if you weren't so intent on being a prick.
>
>>
>>> If you have a source (other than yourself)
>>> that says otherwise, I'm all ears.
>>
>> go to a library!
>> you can also look at this:
>> http://www.flickr.com/photos/38636024@N00/1208725721/
>> the "x" points are the "failure" points for all the materials since
>> onset of yield is failure.
>
> Citing yourself again? Why am I not surprised. You're never going to
> learn anything that way.
prick. /you/ won't admit that you don't understand the difference
between ductile and brittle. if you won't open a book, then i have to
show you.
>
>
>>> If you take the often cited 6x ultimate yield strength of CF, derate
>>> it by the 4 plies (minimum, 0, 90 +-45) you need for isotropy, plus
>>> the ratio of fiber to epoxy, you come out with nothing special wrt
>>> overall strength.
>>
>> eh? why do you need isotropy??? oh, you're trying to force an
>> argument where none exists. my bad.
>
> No, I'm trying to compare "apples to apples" -- material suitability for
> isotropic loading.
aha! more fundamental misunderstanding - there's no such thing as
isotropic loading. that's why we have poisson's ratio.
>
>
>>> That's why there isn't much difference in CF vs Al
>>> handlebars and seatposts (except price).
>>
>> incorrect. it's because it's relatively cheap fiber, relatively
>> imprecise manufacturing and a generous safety margin.
>
> How do you know what the safety margin is?
> How do you know what the fiber is?
> How do you know what the process is?
are you denying the facts?
>
> In the past, you've made the rather obvious point that it's silly to
> talk about metals without knowing the specific alloy. Now, you're making
> gross generalizations about a material which has much greater
> parameterization.
principle apply, big guy.
>
> As far as I know, no component or frame manufacturer publishes layup
> schedules.
they don't quantify, but they do illustrate. you should look some time.
> If you have any, please share. You claimed that a "visit to a
> bike shop" would allow one to learn this.
campy carbon cranks. you can see the exterior layup pattern -
inconvenient for you to admit though this may be.
> I fail to see how visual
> inspection of a composite part would reveal the layup schedule.
er, because you can see the exterior through the clearcoat? but you wan
tto talk substrate? well, you'll have to look online, won't you.
> At best,
> you could perhaps get a little information on the outermost ply, often,
> not even that.
bingo.
>
>
>>> It's only when you exploit
>>> anisotropy that CF makes sense, but then you're stuck with lack of
>>> impact resistance and brittle failure as a trade off.
>>
>> but you have that kind of trade off with /any/ high strength material,
>> even steel. the higher the strength, the more brittle.
>
> You're missing the point about anisotropy.
no i'm not. and that's a spectacular statement from a guy that doesn't
understand the difference between ductile elongation and brittle fracture.
>
>
>>> CF is great for
>>> some apps, marginal for others and crappy for the rest. It's an
>>> engineering thing.
>>
>> wow. condescension, massive over-generalization and naivety all in one.
>
> No, just engineering basics. With CF bars and posts, you get (more
> expensive) parts with similar weights. You also get susceptibility to
> damage from clamping pressure and/or impact. Crappy (yet popular)
> applications.
so when planes have warning labels on them telling crew not to walk on
wings, that can be ignored? bullshit. carbon componentry has labels
saying "do not clamp", "do not exceed...", etc., that can be ignored?
bullshit.
twist all you want - you're still missing the basics.
Peter Cole
> Peter Cole wrote:
>> jim beam wrote:
>>> the "CF Bike Shatters" thread is now too deep for me to follow on my
>>> limited screen real estate - i'm starting a new thread.
>>>
>>> peter cole wrote:
>>>> jim beam wrote:
>>>>> Peter Cole wrote:
>>>>
>>>>>> Find one to support your claim that carbon fibers aren't brittle
>>>>>> & I'll read along.
>>>>>
>>>>> learn about yield before you /dare/ to lecture on deformation,
>>>>> bullshitter.
>>>>
>>>> Oh please. Typical "jim beam" switcharoo. We're talking about
>>>> fracture (see thread title).
>>>
>>> you're confusing fracture of brittle materials with fracture of
>>> ductile materials -
>>
>> I'm not "confusing" them, I'm comparing them.
>
> but you are confusing them - you're not differentiating between ductile
> and brittle - and that's pretty damned fundamental.
You can keep saying that, but I'm not.
>
>>
>>
>>>> Carbon fibers are brittle.
>>>
>>> in isolation, they are. so is any high strength material. but cfrp is
>>> not. what's why we use it!
>>
>> I don't know who "we" is.
>
> prick.
>
>>
>> You're absolutely wrong about CFRP. You can't discuss an inherently
>> anisotropic material without qualifying by fiber orientation (pretty
>> much my whole point).
>
> eh? /you/ are defeating your own argument!!! first you b.s. about
> "isotropic" cfrp, now you're admitting that it's inherently not!!!
Nonsense, read it again.
>
>>
>> A unidirectional fiber composite will have characteristics very much
>> like those of the reinforcing fiber when loaded on-axis. Off-axis,
>> those properties change rapidly,
>
> they don't just "change rapidly", they're completely different. that's
> why it's anisotropic!!!
>
>> becoming essentially those of the matrix at 90 degrees.
>
> mince words whydontcha
Nonsense, read it again.
>
>>
>>>
>>>> They elongate
>>>> only between 0.8 - 1.4% before fracture in tension. E-glass is >3x
>>>> that, 6061 is ~20x that.
>>>
>>> you're mixing apples with oranges. carbon fiber [and glass fiber] have
>>> no deformation mechanism, no dislocation function. so they have no
>>> ductility. so they are "brittle". again, this is not to be confused
>>> with the behavior of their composites.
>>
>> On-axis, the behavior of composite and fiber are very similar.
>
> but composites rarely if ever use solely uniaxial layup. you're trying
> to twist the facts again.
I simply stated a fact.
>>
>>
>>> for glass and carbon, their stress/strain graphs are much extended -
>>
>> Extended from what?
>
> compared to the ductile materials with which you're confused.
>
>>
>>> what would be the hooke's law region of a ductile material.
>>
>> I give up, what?
>
> that wasn't a question. i missed the word "from" - which you'd have
> spotted if you weren't so intent on being a prick.
Your statement is still incoherent.
>>
>>>
>>>> If you have a source (other than yourself)
>>>> that says otherwise, I'm all ears.
>>>
>>> go to a library!
>>> you can also look at this:
>>> http://www.flickr.com/photos/38636024@N00/1208725721/
>>> the "x" points are the "failure" points for all the materials since
>>> onset of yield is failure.
>>
>> Citing yourself again? Why am I not surprised. You're never going to
>> learn anything that way.
>
> prick. /you/ won't admit that you don't understand the difference
> between ductile and brittle. if you won't open a book, then i have to
> show you.
Your diagram has no useful information.
>>>> If you take the often cited 6x ultimate yield strength of CF, derate
>>>> it by the 4 plies (minimum, 0, 90 +-45) you need for isotropy, plus
>>>> the ratio of fiber to epoxy, you come out with nothing special wrt
>>>> overall strength.
>>>
>>> eh? why do you need isotropy??? oh, you're trying to force an
>>> argument where none exists. my bad.
>>
>> No, I'm trying to compare "apples to apples" -- material suitability
>> for isotropic loading.
>
> aha! more fundamental misunderstanding - there's no such thing as
> isotropic loading. that's why we have poisson's ratio.
Now who's mincing words?
>
>>
>>
>>>> That's why there isn't much difference in CF vs Al
>>>> handlebars and seatposts (except price).
>>>
>>> incorrect. it's because it's relatively cheap fiber, relatively
>>> imprecise manufacturing and a generous safety margin.
>>
>> How do you know what the safety margin is?
>> How do you know what the fiber is?
>> How do you know what the process is?
>
> are you denying the facts?
Show me a fact & I'll get back to you on that.
>
>>
>> In the past, you've made the rather obvious point that it's silly to
>> talk about metals without knowing the specific alloy. Now, you're
>> making gross generalizations about a material which has much greater
>> parameterization.
>
> principle apply, big guy.
That's informative!
>> As far as I know, no component or frame manufacturer publishes layup
>> schedules.
>
> they don't quantify, but they do illustrate. you should look some time.
I tried. Why don't you post some of the examples you've found?
>
>> If you have any, please share. You claimed that a "visit to a bike
>> shop" would allow one to learn this.
>
> campy carbon cranks. you can see the exterior layup pattern -
> inconvenient for you to admit though this may be.
>
>
>> I fail to see how visual inspection of a composite part would reveal
>> the layup schedule.
>
> er, because you can see the exterior through the clearcoat? but you wan
> tto talk substrate? well, you'll have to look online, won't you.
>
>
>> At best, you could perhaps get a little information on the outermost
>> ply, often, not even that.
>
> bingo.
That's your idea of a layup schedule?
>>>> It's only when you exploit
>>>> anisotropy that CF makes sense, but then you're stuck with lack of
>>>> impact resistance and brittle failure as a trade off.
>>>
>>> but you have that kind of trade off with /any/ high strength
>>> material, even steel. the higher the strength, the more brittle.
>>
>> You're missing the point about anisotropy.
>
> no i'm not. and that's a spectacular statement from a guy that doesn't
> understand the difference between ductile elongation and brittle fracture.
Repeating that doesn't make it true. You, on the other hand, seem to be
the only one on the planet who doesn't see that CFRP has low impact
resistance.
>>>> CF is great for
>>>> some apps, marginal for others and crappy for the rest. It's an
>>>> engineering thing.
>>>
>>> wow. condescension, massive over-generalization and naivety all in one.
>>
>> No, just engineering basics. With CF bars and posts, you get (more
>> expensive) parts with similar weights. You also get susceptibility to
>> damage from clamping pressure and/or impact. Crappy (yet popular)
>> applications.
>
> so when planes have warning labels on them telling crew not to walk on
> wings, that can be ignored? bullshit. carbon componentry has labels
> saying "do not clamp", "do not exceed...", etc., that can be ignored?
> bullshit.
Who said anything about ignoring labels? I was talking about the need
for labels.
> twist all you want - you're still missing the basics.
If you say so, but do try to scrape up a fact or two & perhaps we can go
from there.
Chalo
>
> you're confusing fracture of brittle materials with fracture of ductile
> materials - the two mechanisms are completely different.
> carbon fiber [and glass fiber] have
> no deformation mechanism, no dislocation function. so they have no
> ductility. so they are "brittle". again, this is not to be confused
> with the behavior of their composites.
>
> for glass and carbon, their stress/strain graphs are much extended -
By "extended", I presume you mean that CFRP and GRP can accept more
stress and strain before failure than structurally comparable metals
can. But since the mechanisms of failure are so different, I think
it's fair to compare the amount of work required to reach brittle
failure for advanced composites and structural metals. You'd have to
seek out an a terribly temperamental metal to find one that is even in
the same ballpark in terms of the small amount of work required to
fracture it. And that's really the practical measure of toughness,
isn't it?
I am surprised at your apparent suggestion (though you don't actually
come out and say so directly) that CFRP could have a significant
amount of ductility or toughness in any of its commonly used
formulations for bicycles. I understand that toughness was one of the
goals, realized or not, for nylon thermoplastic-based CFRP bike frames
and parts. Those constituted a fleeting market experiment, and are
now all gone. The CFRP frames and parts that remain are epoxy-based
and therefore subject to vitreous fracture of both fiber and matrix,
without any useful amount of plastic deformation to absorb transient
overloads or point impacts. In other words, they exhibit extremely
poor toughness.
Which is the point you're trying hard not to concede, right?
Chalo
jim beam
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>> the "CF Bike Shatters" thread is now too deep for me to follow on my
>>>> limited screen real estate - i'm starting a new thread.
>>>>
>>>> peter cole wrote:
>>>>> jim beam wrote:
>>>>>> Peter Cole wrote:
>>>>>
>>>>>>> Find one to support your claim that carbon fibers aren't brittle
>>>>>>> & I'll read along.
>>>>>>
>>>>>> learn about yield before you /dare/ to lecture on deformation,
>>>>>> bullshitter.
>>>>>
>>>>> Oh please. Typical "jim beam" switcharoo. We're talking about
>>>>> fracture (see thread title).
>>>>
>>>> you're confusing fracture of brittle materials with fracture of
>>>> ductile materials -
>>>
>>> I'm not "confusing" them, I'm comparing them.
>>
>> but you are confusing them - you're not differentiating between
>> ductile and brittle - and that's pretty damned fundamental.
>
>
> You can keep saying that, but I'm not.
"6061 elongation is 26%". that's plastic deformation.
"carbon fiber elongation is 1.5%". that's elastic deformation.
there's a fundamental difference an "engineer" should understand.
>
>>
>>>
>>>
>>>>> Carbon fibers are brittle.
>>>>
>>>> in isolation, they are. so is any high strength material. but cfrp is
>>>> not. what's why we use it!
>>>
>>> I don't know who "we" is.
>>
>> prick.
>>
>>>
>>> You're absolutely wrong about CFRP. You can't discuss an inherently
>>> anisotropic material without qualifying by fiber orientation (pretty
>>> much my whole point).
>>
>> eh? /you/ are defeating your own argument!!! first you b.s. about
>> "isotropic" cfrp, now you're admitting that it's inherently not!!!
>
> Nonsense, read it again.
evasive b.s.
>
>>
>>>
>>> A unidirectional fiber composite will have characteristics very much
>>> like those of the reinforcing fiber when loaded on-axis. Off-axis,
>>> those properties change rapidly,
>>
>> they don't just "change rapidly", they're completely different.
>> that's why it's anisotropic!!!
>>
>>> becoming essentially those of the matrix at 90 degrees.
>>
>> mince words whydontcha
>
> Nonsense, read it again.
more evasive b.s.
>
>>
>>>
>>>>
>>>>> They elongate
>>>>> only between 0.8 - 1.4% before fracture in tension. E-glass is >3x
>>>>> that, 6061 is ~20x that.
>>>>
>>>> you're mixing apples with oranges. carbon fiber [and glass fiber] have
>>>> no deformation mechanism, no dislocation function. so they have no
>>>> ductility. so they are "brittle". again, this is not to be confused
>>>> with the behavior of their composites.
>>>
>>> On-axis, the behavior of composite and fiber are very similar.
>>
>> but composites rarely if ever use solely uniaxial layup. you're
>> trying to twist the facts again.
>
> I simply stated a fact.
no, you twisted "facts" to state an untruth.
>
>>>
>>>
>>>> for glass and carbon, their stress/strain graphs are much extended -
>>>
>>> Extended from what?
>>
>> compared to the ductile materials with which you're confused.
>>
>>>
>>>> what would be the hooke's law region of a ductile material.
>>>
>>> I give up, what?
>>
>> that wasn't a question. i missed the word "from" - which you'd have
>> spotted if you weren't so intent on being a prick.
>
> Your statement is still incoherent.
eh? that you don't understand the difference between elastic and
plastic deformation?
>
>
>
>>>
>>>>
>>>>> If you have a source (other than yourself)
>>>>> that says otherwise, I'm all ears.
>>>>
>>>> go to a library!
>>>> you can also look at this:
>>>> http://www.flickr.com/photos/38636024@N00/1208725721/
>>>> the "x" points are the "failure" points for all the materials since
>>>> onset of yield is failure.
>>>
>>> Citing yourself again? Why am I not surprised. You're never going to
>>> learn anything that way.
>>
>> prick. /you/ won't admit that you don't understand the difference
>> between ductile and brittle. if you won't open a book, then i have to
>> show you.
>
> Your diagram has no useful information.
eh? it illustrates different deformation for different materials -
elastic and plastic. something you don't seem to understand.
>
>>>>> If you take the often cited 6x ultimate yield strength of CF, derate
>>>>> it by the 4 plies (minimum, 0, 90 +-45) you need for isotropy, plus
>>>>> the ratio of fiber to epoxy, you come out with nothing special wrt
>>>>> overall strength.
>>>>
>>>> eh? why do you need isotropy??? oh, you're trying to force an
>>>> argument where none exists. my bad.
>>>
>>> No, I'm trying to compare "apples to apples" -- material suitability
>>> for isotropic loading.
>>
>> aha! more fundamental misunderstanding - there's no such thing as
>> isotropic loading. that's why we have poisson's ratio.
>
> Now who's mincing words?
eh? you want me to be more direct? ok. you're an "engineer" that
doesn't know the fundamentals of deformation on loading. that's pretty
fucking weak.
that unmincing enough for you?
>
>
>>
>>>
>>>
>>>>> That's why there isn't much difference in CF vs Al
>>>>> handlebars and seatposts (except price).
>>>>
>>>> incorrect. it's because it's relatively cheap fiber, relatively
>>>> imprecise manufacturing and a generous safety margin.
>>>
>>> How do you know what the safety margin is?
>>> How do you know what the fiber is?
>>> How do you know what the process is?
>>
>> are you denying the facts?
>
> Show me a fact & I'll get back to you on that.
denial. prick.
>
>
>>
>>>
>>> In the past, you've made the rather obvious point that it's silly to
>>> talk about metals without knowing the specific alloy. Now, you're
>>> making gross generalizations about a material which has much greater
>>> parameterization.
>>
>> principle apply, big guy.
>
> That's informative!
from someone that doesn't know basic engineering principles like the
difference between elastic and plastic, that's a real dumb-ass statement.
>
>
>
>>> As far as I know, no component or frame manufacturer publishes layup
>>> schedules.
>>
>> they don't quantify, but they do illustrate. you should look some time.
>
> I tried. Why don't you post some of the examples you've found?
why do i have to do all the heavy lifting??? you're the prick
contesting the issue.
>
>
>>
>>> If you have any, please share. You claimed that a "visit to a bike
>>> shop" would allow one to learn this.
>>
>> campy carbon cranks. you can see the exterior layup pattern -
>> inconvenient for you to admit though this may be.
>>
>>
>>> I fail to see how visual inspection of a composite part would reveal
>>> the layup schedule.
>>
>> er, because you can see the exterior through the clearcoat? but you
>> wan tto talk substrate? well, you'll have to look online, won't you.
>>
>>
>>> At best, you could perhaps get a little information on the outermost
>>> ply, often, not even that.
>>
>> bingo.
>
> That's your idea of a layup schedule?
no. but you're my idea of an evasive prick.
>
>
>>>>> It's only when you exploit
>>>>> anisotropy that CF makes sense, but then you're stuck with lack of
>>>>> impact resistance and brittle failure as a trade off.
>>>>
>>>> but you have that kind of trade off with /any/ high strength
>>>> material, even steel. the higher the strength, the more brittle.
>>>
>>> You're missing the point about anisotropy.
>>
>> no i'm not. and that's a spectacular statement from a guy that
>> doesn't understand the difference between ductile elongation and
>> brittle fracture.
>
> Repeating that doesn't make it true.
no, being true makes it true. repeating denial can't make it untrue.
> You, on the other hand, seem to be
> the only one on the planet who doesn't see that CFRP has low impact
> resistance.
bullshit.
1. who the fuck wants their frame to be resistant to artillery fire.
2. "impact resistance" is a function of the fiber itself, the layup, the
fiber length, density, orientation and matrix - among other things.
"CFRP has low impact resistance" is such a BULLSHIT dumb-ass statement,
it beggars belief.
>
>>>>> CF is great for
>>>>> some apps, marginal for others and crappy for the rest. It's an
>>>>> engineering thing.
>>>>
>>>> wow. condescension, massive over-generalization and naivety all in
>>>> one.
>>>
>>> No, just engineering basics. With CF bars and posts, you get (more
>>> expensive) parts with similar weights. You also get susceptibility to
>>> damage from clamping pressure and/or impact. Crappy (yet popular)
>>> applications.
>>
>> so when planes have warning labels on them telling crew not to walk on
>> wings, that can be ignored? bullshit. carbon componentry has labels
>> saying "do not clamp", "do not exceed...", etc., that can be ignored?
>> bullshit.
>
> Who said anything about ignoring labels? I was talking about the need
> for labels.
so what would your labels say then? "er, this may be elastic or it may
be plastic - we really don't know"?
>
>> twist all you want - you're still missing the basics.
>
> If you say so,
damned right i say so!
> but do try to scrape up a fact or two & perhaps we can go
> from there.
i have. but you seem too intent on being a persistently ignorant prick
to absorb anything.
jim beam
> jim beam wrote:
>> you're confusing fracture of brittle materials with fracture of ductile
>> materials - the two mechanisms are completely different.
> ...
>> carbon fiber [and glass fiber] have
>> no deformation mechanism, no dislocation function. so they have no
>> ductility. so they are "brittle". again, this is not to be confused
>> with the behavior of their composites.
>>
>> for glass and carbon, their stress/strain graphs are much extended -
>
> By "extended", I presume you mean that CFRP and GRP can accept more
> stress and strain before failure than structurally comparable metals
> can.
need to be vary careful with that statement.
1. comparison of strain is debatable with a higher modulus material like
carbon - if the slope is steeper, stress has to rise more for a given
strain. but that greater stiffness on the other hand can be a
significant overall benefit.
2. metal structures like bikes are not used in their plastic zone, only
elastic. the elastic strain before onset of deformation is very limited.
> But since the mechanisms of failure are so different, I think
> it's fair to compare the amount of work required to reach brittle
> failure for advanced composites and structural metals.
disagree - because the mechanisms are different, we /cannot/ compare them.
> You'd have to
> seek out an a terribly temperamental metal to find one that is even in
> the same ballpark in terms of the small amount of work required to
> fracture it. And that's really the practical measure of toughness,
> isn't it?
well, composites do have a degree of toughness - because they're
composites, but bike frames are not made to be sustain damage - as the
definition of toughness means. frames need to /resist/ damage - and for
that, composites that can have much higher strength and much better
fatigue can be a huge benefit.
>
> I am surprised at your apparent suggestion (though you don't actually
> come out and say so directly) that CFRP could have a significant
> amount of ductility or toughness in any of its commonly used
> formulations for bicycles.
that's not what i say or mean. it can have greater strength - a limited
degree of toughness [but only really during failure] but definitely no
ductility.
> I understand that toughness was one of the
> goals, realized or not, for nylon thermoplastic-based CFRP bike frames
> and parts. Those constituted a fleeting market experiment, and are
> now all gone.
toughness is work to deform. metals can be tough. composites not so
much. and if they /do/ evidence their ability to absorb deformation,
it's essentially failed, metal or composite.
> The CFRP frames and parts that remain are epoxy-based
> and therefore subject to vitreous fracture of both fiber and matrix,
> without any useful amount of plastic deformation to absorb transient
> overloads or point impacts. In other words, they exhibit extremely
> poor toughness.
is wood brittle? [composites are modeled on wood.] it doesn't absorb
energy like a ductile metal does. true, energy absorption may be low,
but they still absorb work during failure so they don't just shatter
like glass. and many high strength metals aren't exactly tough either.
not in the habit of dropping cobalt drill bits are you?
>
> Which is the point you're trying hard not to concede, right?
no, i'm "trying" to illustrate that a blanket statement like "carbon is
brittle" is way too ignorant and simplistic. it doesn't address
fatigue. it doesn't address stiffness. it doesn't address strength.
if a material is superior on all these counts, you're further from the
point where failure is even an issue. and even if we /are/ talking
failure mode, we need to compare like with like - saying that 6061
elongates 26% and carbon only 1.5% completely misses the fundamental
point that 24.5% of the aluminum's deformation is plastic, not elastic!
and anything post-elastic is failure in these kinds of applications.
J. Clarke
However a bent metal frame can still get you home. A carbon frame
that has failed turns you into a pedestrian.
--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
jim beam
that depends. if it's completely fallen apart, obviously not. and if
it looks like it's about to fall apart, obviously not. however, while
is entirely "case by case", a carbon frame /can/ be ridden while
starting to fail. just be real slow and real careful. a friend rode an
mtb frame home with a bb that was starting to break loose. i've ridden
one of those crappy cracking chinese kestrel forks home. carbon rarely
completely vaporizes "jra" as some would have you believe - it's people
that ignore the warning signs that have the problems.
Chalo
>
> Chalo wrote:
> >
> > it's fair to compare the amount of work required to reach brittle
> > failure for advanced composites and structural metals.
>
> disagree - because the mechanisms are different, we /cannot/ compare them.
I think we can, because catastrophic failure is what we're most
concerned about. The sort of "failure" that lets you avoid a crash,
ride home, or even not know that your frame was damaged until your
mechanic tells you at tune-up time, is a different and preferable
category of failure than what composites display.
> > You'd have to
> > seek out an a terribly temperamental metal to find one that is even in
> > the same ballpark in terms of the small amount of work required to
> > fracture it. And that's really the practical measure of toughness,
> > isn't it?
>
> well, composites do have a degree of toughness - because they're
> composites, but bike frames are not made to be sustain damage - as the
> definition of toughness means.
I have seen many a peened, dented, and scratched top tube on commuter,
messenger, and city bikes demonstrating the principle that some bikes
_do_ need to sustain some damage and keep working.
> frames need to /resist/ damage - and for
> that, composites that can have much higher strength and much better
> fatigue can be a huge benefit.
A steel bike that must be rugged and tolerate impacts and abrasion on
bike racks etc. can simply be made a bit heavier than strictly
necessary for the required strength. If you do this with a CFRP
frame, you wind up with a frame that's stronger and stiffer, but no
more tolerant of dings and abrasions, than a lightweight CFRP frame.
That makes carbon-epoxy acceptable for a vanity bike or a racing bike,
but not so much for a transportational or working bike. And even a
racer or a weekend warrior who would like their bike to be able to
take a blow and keep rolling might want to use a more damage-tolerant
material.
Compare carbon-carbon brake rotors on race cars. They clearly
outperform cast iron rotors, and it would still be a bad idea to stick
them on everybody's Camry.
> is wood brittle? [composites are modeled on wood.] it doesn't absorb
> energy like a ductile metal does. true, energy absorption may be low,
> but they still absorb work during failure so they don't just shatter
> like glass. and many high strength metals aren't exactly tough either.
> not in the habit of dropping cobalt drill bits are you?
Wood is a pretty seriously compromised material for making bike
frames. So is M42 cobalt high-speed steel.
> and even if we /are/ talking
> failure mode, we need to compare like with like - saying that 6061
> elongates 26% and carbon only 1.5% completely misses the fundamental
> point that 24.5% of the aluminum's deformation is plastic, not elastic!
> and anything post-elastic is failure in these kinds of applications.
I just noticed that I had a post-elastic failure in my 29er's steel
seatpost-- the second such event in its short career. The
implication? I have to remember to order up another one sometime. In
the meantime I can continue to use this one. If my seatposts had been
made of CFRP, the situation might have been a bit more problematic.
Chalo
Ryan Cousineau
Chalo <chalo....@gmail.com> wrote:
> I just noticed that I had a post-elastic failure in my 29er's steel
> seatpost-- the second such event in its short career. The
> implication? I have to remember to order up another one sometime. In
> the meantime I can continue to use this one. If my seatposts had been
> made of CFRP, the situation might have been a bit more problematic.
If the seatpost had been made of CFRP (or if you're conservative, a CFRP
wrap over metal) would it have failed at all?
--
Ryan Cousineau rcou...@sfu.ca http://www.wiredcola.com/
"I don't want kids who are thinking about going into mathematics
to think that they have to take drugs to succeed." -Paul Erdos
Chalo
>
> Chalo<chalo.col...@gmail.com> wrote:
> >
> > I just noticed that I had a post-elastic failure in my 29er's steel
> > seatpost-- the second such event in its short career. The
> > implication? I have to remember to order up another one sometime. In
> > the meantime I can continue to use this one. If my seatposts had been
> > made of CFRP, the situation might have been a bit more problematic.
>
> If the seatpost had been made of CFRP (or if you're conservative, a CFRP
> wrap over metal) would it have failed at all?
That's a worthy question. The fact that this newly bent one is made
of heat-treated 4130 chromoly and weighs about twice what a weight-
weenie type seatpost weighs makes me think it might not be a good idea
to experiment.
The first post that bent was a welded, non-heat-treated chromoly
post. It didn't last long, and it bent very noticeably. The one I
just found to be bent was close enough to straight to make me wonder
if my eyes were fooling me. I used the straight edge of a machinist's
caliper as a reference to determine that the front edge was slightly
bowed and the rear edge slightly rippled.
I've ordered up another of the same kind of seatpost. If it bends
again, then I'll try a Thomson Elite post, the only commercial
seatpost I have used that I've never managed to bend. My hesitance to
use a Thomson is related to my refusal to use a CFRP post-- it's made
of a very high yield strength alloy that doesn't offer much margin
between bending and snapping off. If it doesn't bend, no problem. If
it does, well, that could become a problem.
Chalo
jim beam
> jim beam wrote:
>> Chalo wrote:
>>> But since the mechanisms of failure are so different, I think
>>> it's fair to compare the amount of work required to reach brittle
>>> failure for advanced composites and structural metals.
>> disagree - because the mechanisms are different, we /cannot/ compare them.
>
> I think we can, because catastrophic failure is what we're most
> concerned about.
but i think that's misplaced. the "headroom" on quality carbon is
substantial compared to traditional bike materials. there was a graph
on the reynolds for website comparing their fork strength to steel - it
was 3 times stronger for about half the weight iirc.
> The sort of "failure" that lets you avoid a crash,
> ride home, or even not know that your frame was damaged until your
> mechanic tells you at tune-up time, is a different and preferable
> category of failure than what composites display.
but a yielding metal tube can cause a crash just like a failing carbon
tube. a fatiguing metal tube can fail at stress much below normal
service. carbon fails much /above/ normal service.
>
>>> You'd have to
>>> seek out an a terribly temperamental metal to find one that is even in
>>> the same ballpark in terms of the small amount of work required to
>>> fracture it. And that's really the practical measure of toughness,
>>> isn't it?
>> well, composites do have a degree of toughness - because they're
>> composites, but bike frames are not made to be sustain damage - as the
>> definition of toughness means.
>
> I have seen many a peened, dented, and scratched top tube on commuter,
> messenger, and city bikes demonstrating the principle that some bikes
> _do_ need to sustain some damage and keep working.
my carbon commuter fork is not exactly pristine either. and peened,
dented scratched metal tubes can fatigue.
>
>> frames need to /resist/ damage - and for
>> that, composites that can have much higher strength and much better
>> fatigue can be a huge benefit.
>
> A steel bike that must be rugged and tolerate impacts and abrasion on
> bike racks etc. can simply be made a bit heavier than strictly
> necessary for the required strength. If you do this with a CFRP
> frame, you wind up with a frame that's stronger and stiffer, but no
> more tolerant of dings and abrasions, than a lightweight CFRP frame.
that's not true. can a tick piece of wood take more abuse than a thing
piece? the answer is "of course".
> That makes carbon-epoxy acceptable for a vanity bike or a racing bike,
> but not so much for a transportational or working bike. And even a
> racer or a weekend warrior who would like their bike to be able to
> take a blow and keep rolling might want to use a more damage-tolerant
> material.
/cost/ makes it inappropriate, not the material's properties.
>
> Compare carbon-carbon brake rotors on race cars. They clearly
> outperform cast iron rotors, and it would still be a bad idea to stick
> them on everybody's Camry.
no, they don't outperform for normal road cars. carbon brake disks only
really work well above a temperature that normal road cars only seldom
reach.
>
>> is wood brittle? [composites are modeled on wood.] it doesn't absorb
>> energy like a ductile metal does. true, energy absorption may be low,
>> but they still absorb work during failure so they don't just shatter
>> like glass. and many high strength metals aren't exactly tough either.
>> not in the habit of dropping cobalt drill bits are you?
>
> Wood is a pretty seriously compromised material for making bike
> frames. So is M42 cobalt high-speed steel.
but the point is, wood's not brittle. and metal can be. an
over-simplification like "metal good, composite bad" shows the speaker
to be completely under-informed.
>
>> and even if we /are/ talking
>> failure mode, we need to compare like with like - saying that 6061
>> elongates 26% and carbon only 1.5% completely misses the fundamental
>> point that 24.5% of the aluminum's deformation is plastic, not elastic!
>> and anything post-elastic is failure in these kinds of applications.
>
> I just noticed that I had a post-elastic failure in my 29er's steel
> seatpost-- the second such event in its short career. The
> implication? I have to remember to order up another one sometime. In
> the meantime I can continue to use this one. If my seatposts had been
> made of CFRP, the situation might have been a bit more problematic.
or not - it could be substantially stronger. unless there are numbers
and testing, failure of one material simply cannot imply failure of another!
jim beam
what is the extension? did you calculate the strength of the post vs.
the leverage the extension exerts? have you compared the strength of
say an easton carbon post and your steel post?
Tom "Johnny Sunset" Sherman
>
> By "extended", I presume you mean that CFRP and GRP can accept more
> stress and strain before failure than structurally comparable metals
> can. But since the mechanisms of failure are so different, I think
> it's fair to compare the amount of work required to reach brittle
> failure for advanced composites and structural metals. You'd have to
> seek out an a terribly temperamental metal to find one that is even in
> the same ballpark in terms of the small amount of work required to
Quenched plain carbon steel without tempering?
--
Tom Sherman - Holstein-Friesland Bovinia
--
Posted via a free Usenet account from http://www.teranews.com
Tom "Johnny Sunset" Sherman
> ...
> can a tick piece of wood take more abuse than a thing piece?...
Huh? Who knows?
jim beam
> "jim beam" wrote:
>> ...
>> can a tick piece of wood take more abuse than a thing piece?...
>
> Huh? Who knows?
>
yeah, ok. make that:
"can a tHick piece of wood take more abuse than a thin_ piece?"
thanks.
Ryan Cousineau
Chalo <chalo....@gmail.com> wrote:
> Ryan Cousineau wrote:
> >
> > Chalo<chalo.col...@gmail.com> wrote:
> > >
> > > I just noticed that I had a post-elastic failure in my 29er's steel
> > > seatpost-- the second such event in its short career. The
> > > implication? I have to remember to order up another one sometime. In
> > > the meantime I can continue to use this one. If my seatposts had been
> > > made of CFRP, the situation might have been a bit more problematic.
> >
> > If the seatpost had been made of CFRP (or if you're conservative, a CFRP
> > wrap over metal) would it have failed at all?
>
> That's a worthy question. The fact that this newly bent one is made
> of heat-treated 4130 chromoly and weighs about twice what a weight-
> weenie type seatpost weighs makes me think it might not be a good idea
> to experiment.
>
> The first post that bent was a welded, non-heat-treated chromoly
> post. It didn't last long, and it bent very noticeably. The one I
> just found to be bent was close enough to straight to make me wonder
> if my eyes were fooling me. I used the straight edge of a machinist's
> caliper as a reference to determine that the front edge was slightly
> bowed and the rear edge slightly rippled.
I'm not telling you anything new, but this sounds like you're chasing a
design issue with materials, inasmuch as you really want a shorter
seatpost extension or a larger-diameter seatpost. But I'm assuming that
would mean abandoning an expensive-to-replace frame.
> I've ordered up another of the same kind of seatpost. If it bends
> again, then I'll try a Thomson Elite post, the only commercial
> seatpost I have used that I've never managed to bend. My hesitance to
> use a Thomson is related to my refusal to use a CFRP post-- it's made
> of a very high yield strength alloy that doesn't offer much margin
> between bending and snapping off. If it doesn't bend, no problem. If
> it does, well, that could become a problem.
--
jim beam
> In article <1187987732....@q3g2000prf.googlegroups.com>,
> Chalo <chalo....@gmail.com> wrote:
>
>> Ryan Cousineau wrote:
>>> Chalo<chalo.col...@gmail.com> wrote:
>>>> I just noticed that I had a post-elastic failure in my 29er's steel
>>>> seatpost-- the second such event in its short career. The
>>>> implication? I have to remember to order up another one sometime. In
>>>> the meantime I can continue to use this one. If my seatposts had been
>>>> made of CFRP, the situation might have been a bit more problematic.
>>> If the seatpost had been made of CFRP (or if you're conservative, a CFRP
>>> wrap over metal) would it have failed at all?
>> That's a worthy question. The fact that this newly bent one is made
>> of heat-treated 4130 chromoly and weighs about twice what a weight-
>> weenie type seatpost weighs makes me think it might not be a good idea
>> to experiment.
>>
>> The first post that bent was a welded, non-heat-treated chromoly
>> post. It didn't last long, and it bent very noticeably. The one I
>> just found to be bent was close enough to straight to make me wonder
>> if my eyes were fooling me. I used the straight edge of a machinist's
>> caliper as a reference to determine that the front edge was slightly
>> bowed and the rear edge slightly rippled.
>
> I'm not telling you anything new, but this sounds like you're chasing a
> design issue with materials,
well said. it's ridiculously common unfortunately - not unique to chalo
by any means.
Chalo
LOL! I get it now!
Chalo
>
> Chalo wrote:
> >
> > Ryan Cousineau wrote:
>
> > > wrap over metal) would it have failed at all?
>
> > That's a worthy question. The fact that this newly bent one is made
> > of heat-treated 4130 chromoly and weighs about twice what a weight-
> > weenie type seatpost weighs makes me think it might not be a good idea
> > to experiment.
>
> > The first post that bent was a welded, non-heat-treated chromoly
> > post. It didn't last long, and it bent very noticeably. The one I
> > just found to be bent was close enough to straight to make me wonder
> > if my eyes were fooling me. I used the straight edge of a machinist's
> > caliper as a reference to determine that the front edge was slightly
> > bowed and the rear edge slightly rippled.
>
> I'm not telling you anything new, but this sounds like you're chasing a
> design issue with materials, inasmuch as you really want a shorter
> seatpost extension or a larger-diameter seatpost. But I'm assuming that
> would mean abandoning an expensive-to-replace frame.
Right. This post has an extension of 10" to the saddle rails and 15"
to the rear edge of the saddle, which is more than I'd otherwise opt
for. It's not the longest post in my stable by any means, but it's
the longest one I didn't make myself.
I have two basic problems with repeating my customary process of
making my own seatpost from solid or very thick-walled high strength
aluminum. First, that transfers the reliability issue from the post
itself to the crappy seat guts that I must use if I switch to a
straight seat pin. Second, I am fresh out of lathes at the moment.
I wish someone would offer the equivalent of the long-departed VG seat
guts, which were machined from billet aluminum and very stout.
Chalo
Peter Cole
Yes, that's obvious. Who said it wasn't?
You don't have to put quotes around engineer.
>
>
>>
>>>
>>>>
>>>>
>>>>>> Carbon fibers are brittle.
>>>>>
>>>>> in isolation, they are. so is any high strength material. but
>>>>> cfrp is
>>>>> not. what's why we use it!
>>>>
>>>> I don't know who "we" is.
>>>
>>> prick.
>>>
>>>>
>>>> You're absolutely wrong about CFRP. You can't discuss an inherently
>>>> anisotropic material without qualifying by fiber orientation (pretty
>>>> much my whole point).
>>>
>>> eh? /you/ are defeating your own argument!!! first you b.s. about
>>> "isotropic" cfrp, now you're admitting that it's inherently not!!!
>>
>> Nonsense, read it again.
>
> evasive b.s.
You can't discuss CFRP without layup schedule. Uniaxial CFRP has
impressive numbers -- in one direction.
>>
>>>
>>>>
>>>> A unidirectional fiber composite will have characteristics very much
>>>> like those of the reinforcing fiber when loaded on-axis. Off-axis,
>>>> those properties change rapidly,
>>>
>>> they don't just "change rapidly", they're completely different.
>>> that's why it's anisotropic!!!
>>>
>>>> becoming essentially those of the matrix at 90 degrees.
>>>
>>> mince words whydontcha
>>
>> Nonsense, read it again.
>
> more evasive b.s.
If you take the trouble to look at the stress-strain of uniaxial CFRP as
the load angle changes, all will become clear.
>
>>
>>>
>>>>
>>>>>
>>>>>> They elongate
>>>>>> only between 0.8 - 1.4% before fracture in tension. E-glass is >3x
>>>>>> that, 6061 is ~20x that.
>>>>>
>>>>> you're mixing apples with oranges. carbon fiber [and glass fiber]
>>>>> have
>>>>> no deformation mechanism, no dislocation function. so they have no
>>>>> ductility. so they are "brittle". again, this is not to be confused
>>>>> with the behavior of their composites.
>>>>
>>>> On-axis, the behavior of composite and fiber are very similar.
>>>
>>> but composites rarely if ever use solely uniaxial layup. you're
>>> trying to twist the facts again.
>>
>> I simply stated a fact.
>
> no, you twisted "facts" to state an untruth.
Composite will be as brittle as it is strong. Try to understand that.
>>
>>>>
>>>>
>>>>> for glass and carbon, their stress/strain graphs are much extended -
>>>>
>>>> Extended from what?
>>>
>>> compared to the ductile materials with which you're confused.
>>>
>>>>
>>>>> what would be the hooke's law region of a ductile material.
>>>>
>>>> I give up, what?
>>>
>>> that wasn't a question. i missed the word "from" - which you'd have
>>> spotted if you weren't so intent on being a prick.
>>
>> Your statement is still incoherent.
>
> eh? that you don't understand the difference between elastic and
> plastic deformation?
>
I certainly do, it's not so very hard to grasp.
>>
>>
>>
>>>>
>>>>>
>>>>>> If you have a source (other than yourself)
>>>>>> that says otherwise, I'm all ears.
>>>>>
>>>>> go to a library!
>>>>> you can also look at this:
>>>>> http://www.flickr.com/photos/38636024@N00/1208725721/
>>>>> the "x" points are the "failure" points for all the materials since
>>>>> onset of yield is failure.
>>>>
>>>> Citing yourself again? Why am I not surprised. You're never going to
>>>> learn anything that way.
>>>
>>> prick. /you/ won't admit that you don't understand the difference
>>> between ductile and brittle. if you won't open a book, then i have
>>> to show you.
>>
>> Your diagram has no useful information.
>
> eh? it illustrates different deformation for different materials -
> elastic and plastic. something you don't seem to understand.
It's not to scale, it attempts to depict fiber rather than composite. It
still doesn't explain why you disagree with the rest of the world about
CF composite being brittle.
>
>
>>
>>>>>> If you take the often cited 6x ultimate yield strength of CF, derate
>>>>>> it by the 4 plies (minimum, 0, 90 +-45) you need for isotropy, plus
>>>>>> the ratio of fiber to epoxy, you come out with nothing special wrt
>>>>>> overall strength.
>>>>>
>>>>> eh? why do you need isotropy??? oh, you're trying to force an
>>>>> argument where none exists. my bad.
>>>>
>>>> No, I'm trying to compare "apples to apples" -- material suitability
>>>> for isotropic loading.
>>>
>>> aha! more fundamental misunderstanding - there's no such thing as
>>> isotropic loading. that's why we have poisson's ratio.
>>
>> Now who's mincing words?
>
> eh? you want me to be more direct? ok. you're an "engineer" that
> doesn't know the fundamentals of deformation on loading. that's pretty
> fucking weak.
>
> that unmincing enough for you?
That's lovely (in sentiment) but unfortunately still incoherent.
>>
>>
>>>
>>>>
>>>>
>>>>>> That's why there isn't much difference in CF vs Al
>>>>>> handlebars and seatposts (except price).
>>>>>
>>>>> incorrect. it's because it's relatively cheap fiber, relatively
>>>>> imprecise manufacturing and a generous safety margin.
>>>>
>>>> How do you know what the safety margin is?
>>>> How do you know what the fiber is?
>>>> How do you know what the process is?
>>>
>>> are you denying the facts?
>>
>> Show me a fact & I'll get back to you on that.
>
> denial. prick.
I do hope you get help with your Tourette's, meanwhile, got any facts?
>>>>
>>>> In the past, you've made the rather obvious point that it's silly to
>>>> talk about metals without knowing the specific alloy. Now, you're
>>>> making gross generalizations about a material which has much greater
>>>> parameterization.
>>>
>>> principle apply, big guy.
>>
>> That's informative!
>
> from someone that doesn't know basic engineering principles like the
> difference between elastic and plastic, that's a real dumb-ass statement.
OK, what "principle"?
>
>
>>
>>
>>
>>>> As far as I know, no component or frame manufacturer publishes layup
>>>> schedules.
>>>
>>> they don't quantify, but they do illustrate. you should look some time.
>>
>> I tried. Why don't you post some of the examples you've found?
>
> why do i have to do all the heavy lifting??? you're the prick
> contesting the issue.
I didn't think you had any. Given that they're all proprietary, that
would have been impressive. So just go on in through-your-hat mode (I'm
much too polite to use the obvious term).
>>>
>>>> If you have any, please share. You claimed that a "visit to a bike
>>>> shop" would allow one to learn this.
>>>
>>> campy carbon cranks. you can see the exterior layup pattern -
>>> inconvenient for you to admit though this may be.
>>>
>>>
>>>> I fail to see how visual inspection of a composite part would reveal
>>>> the layup schedule.
>>>
>>> er, because you can see the exterior through the clearcoat? but you
>>> wan tto talk substrate? well, you'll have to look online, won't you.
Show me a link, & I'll be right over.
>>>
>>>
>>>> At best, you could perhaps get a little information on the outermost
>>>> ply, often, not even that.
>>>
>>> bingo.
>>
>> That's your idea of a layup schedule?
>
> no. but you're my idea of an evasive prick.
What about layup schedule (I already know your opinion of me)?
>
>>
>>
>>>>>> It's only when you exploit
>>>>>> anisotropy that CF makes sense, but then you're stuck with lack of
>>>>>> impact resistance and brittle failure as a trade off.
>>>>>
>>>>> but you have that kind of trade off with /any/ high strength
>>>>> material, even steel. the higher the strength, the more brittle.
>>>>
>>>> You're missing the point about anisotropy.
>>>
>>> no i'm not. and that's a spectacular statement from a guy that
>>> doesn't understand the difference between ductile elongation and
>>> brittle fracture.
>>
>> Repeating that doesn't make it true.
>
> no, being true makes it true. repeating denial can't make it untrue.
>
>
>> You, on the other hand, seem to be the only one on the planet who
>> doesn't see that CFRP has low impact resistance.
>
> bullshit.
>
> 1. who the fuck wants their frame to be resistant to artillery fire.
> 2. "impact resistance" is a function of the fiber itself, the layup, the
> fiber length, density, orientation and matrix - among other things.
> "CFRP has low impact resistance" is such a BULLSHIT dumb-ass statement,
> it beggars belief.
Then why does everyone believe it but you?
>>
>>>>>> CF is great for
>>>>>> some apps, marginal for others and crappy for the rest. It's an
>>>>>> engineering thing.
>>>>>
>>>>> wow. condescension, massive over-generalization and naivety all in
>>>>> one.
>>>>
>>>> No, just engineering basics. With CF bars and posts, you get (more
>>>> expensive) parts with similar weights. You also get susceptibility
>>>> to damage from clamping pressure and/or impact. Crappy (yet popular)
>>>> applications.
>>>
>>> so when planes have warning labels on them telling crew not to walk
>>> on wings, that can be ignored? bullshit. carbon componentry has
>>> labels saying "do not clamp", "do not exceed...", etc., that can be
>>> ignored? bullshit.
>>
>> Who said anything about ignoring labels? I was talking about the need
>> for labels.
>
> so what would your labels say then? "er, this may be elastic or it may
> be plastic - we really don't know"?
That does not even make a shred of sense.
>>
>>> twist all you want - you're still missing the basics.
>>
>> If you say so,
>
> damned right i say so!
>
> > but do try to scrape up a fact or two & perhaps we can go
>> from there.
>
> i have. but you seem too intent on being a persistently ignorant prick
> to absorb anything.
I have yet to see a fact, only "jim beam"-ish self-cites. Perhaps
they're the same in your world, but not in the much bigger world the
rest of us live in.
Peter Cole
> no, i'm "trying" to illustrate that a blanket statement like "carbon is
> brittle" is way too ignorant and simplistic. it doesn't address
> fatigue. it doesn't address stiffness. it doesn't address strength.
Of course not silly, it only addresses impact strength. I hope we've
cleared that up!
> and even if we /are/ talking
> failure mode, we need to compare like with like - saying that 6061
> elongates 26% and carbon only 1.5% completely misses the fundamental
> point that 24.5% of the aluminum's deformation is plastic, not elastic!
> and anything post-elastic is failure in these kinds of applications.
Yes, and one is "brittle" failure, the other isn't. And that is why CF
composite has lousy impact strength.
You are hopelessly confused between force and energy. You should have
read my first post more carefully.
Peter Cole
> J. Clarke wrote:
>> However a bent metal frame can still get you home. A carbon frame
>> that has failed turns you into a pedestrian.
Perhaps one with major dental bills.
>>
>
> that depends. if it's completely fallen apart, obviously not. and if
> it looks like it's about to fall apart, obviously not. however, while
> is entirely "case by case", a carbon frame /can/ be ridden while
> starting to fail. just be real slow and real careful. a friend rode an
> mtb frame home with a bb that was starting to break loose. i've ridden
> one of those crappy cracking chinese kestrel forks home. carbon rarely
> completely vaporizes "jra" as some would have you believe - it's people
> that ignore the warning signs that have the problems.
Warning!
A damaged carbon fiber part can fail suddenly, causing
serious injury or death. Inspect a carbon fiber part for
damage frequently. If you suspect a carbon fiber part is
damaged, replace the part before riding, or take the bike to
your dealer for service.
(warm words from Trek)
Peter Cole
> but the point is, wood's not brittle. and metal can be.
But CF always is!
Peter Cole
> what is the extension? did you calculate the strength of the post vs.
> the leverage the extension exerts? have you compared the strength of
> say an easton carbon post and your steel post?
How do you know the strength of an Easton carbon post?
Tim McNamara
Peter Cole <peter...@comcast.net> wrote:
Such frequent inspection is difficult if the carbon fiber part in
question is a steerer tube, of which we have had reports of JRA
failures. Fortunately we have had no reports of "carbon completely
vaporizing" to use jim's refutation-by-hyperbole breathlessness. Well,
we actually have lots of reports of that happening since it is a normal
part of combustion- but we have no reports of carbon fiber bicycle parts
vaporizing while JRA. Breaking, yes; vaporizing, no.
Of course, we could ask George Hincapie about the durability of Trek's
aluminum steerers. In the case of the OP, we still don't know what
happened: did he hit a pothole, break the frame and crash? Or did he
hit a pothole, crash and then break the frame? Since none of us here
have examined the bike, interviewed the rider and any witnesses, or
looked at the crash scene it is not possible for us to determine what
happened.
I think I will stick with products that don't need to be treated with
kid gloves and detailed inspections before every ride.
Tim McNamara
Peter Cole <peter...@comcast.net> wrote:
Whether wood is brittle depends on the species of wood and its
condition.
jim beam
anyone mistaking plastic elongation for plastic elongation /clearly/
doesn't find the distinction "obvious".
>
> You don't have to put quotes around engineer.
you do if it's a name someone calls themselves, but doesn't evidence
qualification.
>
>
>>
>>
>>>
>>>>
>>>>>
>>>>>
>>>>>>> Carbon fibers are brittle.
>>>>>>
>>>>>> in isolation, they are. so is any high strength material. but
>>>>>> cfrp is
>>>>>> not. what's why we use it!
>>>>>
>>>>> I don't know who "we" is.
>>>>
>>>> prick.
>>>>
>>>>>
>>>>> You're absolutely wrong about CFRP. You can't discuss an inherently
>>>>> anisotropic material without qualifying by fiber orientation
>>>>> (pretty much my whole point).
>>>>
>>>> eh? /you/ are defeating your own argument!!! first you b.s. about
>>>> "isotropic" cfrp, now you're admitting that it's inherently not!!!
>>>
>>> Nonsense, read it again.
>>
>> evasive b.s.
>
> You can't discuss CFRP without layup schedule. Uniaxial CFRP has
> impressive numbers -- in one direction.
"in one direction" indeed. so why bleat about isotropy as if it's a
base property? because you're bullshitting and trying to muddy the
water, that's why!
>
>
>>>
>>>>
>>>>>
>>>>> A unidirectional fiber composite will have characteristics very
>>>>> much like those of the reinforcing fiber when loaded on-axis.
>>>>> Off-axis, those properties change rapidly,
>>>>
>>>> they don't just "change rapidly", they're completely different.
>>>> that's why it's anisotropic!!!
>>>>
>>>>> becoming essentially those of the matrix at 90 degrees.
>>>>
>>>> mince words whydontcha
>>>
>>> Nonsense, read it again.
>>
>> more evasive b.s.
>
> If you take the trouble to look at the stress-strain of uniaxial CFRP as
> the load angle changes, all will become clear.
says the guy that bullshits about elongation while getting confused
between plastic and elastic deformation...
>
>
>>
>>>
>>>>
>>>>>
>>>>>>
>>>>>>> They elongate
>>>>>>> only between 0.8 - 1.4% before fracture in tension. E-glass is >3x
>>>>>>> that, 6061 is ~20x that.
>>>>>>
>>>>>> you're mixing apples with oranges. carbon fiber [and glass fiber]
>>>>>> have
>>>>>> no deformation mechanism, no dislocation function. so they have no
>>>>>> ductility. so they are "brittle". again, this is not to be confused
>>>>>> with the behavior of their composites.
>>>>>
>>>>> On-axis, the behavior of composite and fiber are very similar.
>>>>
>>>> but composites rarely if ever use solely uniaxial layup. you're
>>>> trying to twist the facts again.
>>>
>>> I simply stated a fact.
>>
>> no, you twisted "facts" to state an untruth.
>
> Composite will be as brittle as it is strong. Try to understand that.
!!! sure! there measured in the same units too aren't they!!!
>
>
>>>
>>>>>
>>>>>
>>>>>> for glass and carbon, their stress/strain graphs are much extended -
>>>>>
>>>>> Extended from what?
>>>>
>>>> compared to the ductile materials with which you're confused.
>>>>
>>>>>
>>>>>> what would be the hooke's law region of a ductile material.
>>>>>
>>>>> I give up, what?
>>>>
>>>> that wasn't a question. i missed the word "from" - which you'd have
>>>> spotted if you weren't so intent on being a prick.
>>>
>>> Your statement is still incoherent.
>>
>> eh? that you don't understand the difference between elastic and
>> plastic deformation?
>>
>
> I certainly do, it's not so very hard to grasp.
so why the painful confusion between plastic and elastic? stupidity?
or deliberate bullshit?
>
>
>>>
>>>
>>>
>>>>>
>>>>>>
>>>>>>> If you have a source (other than yourself)
>>>>>>> that says otherwise, I'm all ears.
>>>>>>
>>>>>> go to a library!
>>>>>> you can also look at this:
>>>>>> http://www.flickr.com/photos/38636024@N00/1208725721/
>>>>>> the "x" points are the "failure" points for all the materials
>>>>>> since onset of yield is failure.
>>>>>
>>>>> Citing yourself again? Why am I not surprised. You're never going
>>>>> to learn anything that way.
>>>>
>>>> prick. /you/ won't admit that you don't understand the difference
>>>> between ductile and brittle. if you won't open a book, then i have
>>>> to show you.
>>>
>>> Your diagram has no useful information.
>>
>> eh? it illustrates different deformation for different materials -
>> elastic and plastic. something you don't seem to understand.
>
> It's not to scale, it attempts to depict fiber rather than composite. It
> still doesn't explain why you disagree with the rest of the world about
> CF composite being brittle.
1. what part of the label stating "NOT TO SCALE" is confusing to you???
2. composites have properties intermediate between the fiber and the
matrix, depending on composition.
3. bullshit statements that "carbon is brittle" is as misleading as it
is wrong.
>
>
>>
>>
>>>
>>>>>>> If you take the often cited 6x ultimate yield strength of CF, derate
>>>>>>> it by the 4 plies (minimum, 0, 90 +-45) you need for isotropy, plus
>>>>>>> the ratio of fiber to epoxy, you come out with nothing special wrt
>>>>>>> overall strength.
>>>>>>
>>>>>> eh? why do you need isotropy??? oh, you're trying to force an
>>>>>> argument where none exists. my bad.
>>>>>
>>>>> No, I'm trying to compare "apples to apples" -- material
>>>>> suitability for isotropic loading.
>>>>
>>>> aha! more fundamental misunderstanding - there's no such thing as
>>>> isotropic loading. that's why we have poisson's ratio.
>>>
>>> Now who's mincing words?
>>
>> eh? you want me to be more direct? ok. you're an "engineer" that
>> doesn't know the fundamentals of deformation on loading. that's
>> pretty fucking weak.
>>
>> that unmincing enough for you?
>
> That's lovely (in sentiment) but unfortunately still incoherent.
/your/ confusion between elastic and plastic is incoherent buddy.
>
>
>>>
>>>
>>>>
>>>>>
>>>>>
>>>>>>> That's why there isn't much difference in CF vs Al
>>>>>>> handlebars and seatposts (except price).
>>>>>>
>>>>>> incorrect. it's because it's relatively cheap fiber, relatively
>>>>>> imprecise manufacturing and a generous safety margin.
>>>>>
>>>>> How do you know what the safety margin is?
>>>>> How do you know what the fiber is?
>>>>> How do you know what the process is?
>>>>
>>>> are you denying the facts?
>>>
>>> Show me a fact & I'll get back to you on that.
>>
>> denial. prick.
>
> I do hope you get help with your Tourette's, meanwhile, got any facts?
fuck you, prick. you've already got facts of principle. what you're
bleating about is numbers. but you're no stranger to deliberate
muddying of the water are you.
>
>
>>>>>
>>>>> In the past, you've made the rather obvious point that it's silly
>>>>> to talk about metals without knowing the specific alloy. Now,
>>>>> you're making gross generalizations about a material which has much
>>>>> greater parameterization.
>>>>
>>>> principle apply, big guy.
>>>
>>> That's informative!
>>
>> from someone that doesn't know basic engineering principles like the
>> difference between elastic and plastic, that's a real dumb-ass statement.
>
>
> OK, what "principle"?
er, how about we start with "elastic is not plastic"?
>
>
>>
>>
>>>
>>>
>>>
>>>>> As far as I know, no component or frame manufacturer publishes
>>>>> layup schedules.
>>>>
>>>> they don't quantify, but they do illustrate. you should look some
>>>> time.
>>>
>>> I tried. Why don't you post some of the examples you've found?
>>
>> why do i have to do all the heavy lifting??? you're the prick
>> contesting the issue.
>
> I didn't think you had any.
bullshit.
> Given that they're all proprietary,
bullshit! spectacular avoidance!!!
> that
> would have been impressive. So just go on in through-your-hat mode (I'm
> much too polite to use the obvious term).
oh, please, let me - you're a prick, "mr. engineer".
>
>
>>>>
>>>>> If you have any, please share. You claimed that a "visit to a bike
>>>>> shop" would allow one to learn this.
>>>>
>>>> campy carbon cranks. you can see the exterior layup pattern -
>>>> inconvenient for you to admit though this may be.
>>>>
>>>>
>>>>> I fail to see how visual inspection of a composite part would
>>>>> reveal the layup schedule.
>>>>
>>>> er, because you can see the exterior through the clearcoat? but you
>>>> wan tto talk substrate? well, you'll have to look online, won't you.
>
> Show me a link, & I'll be right over.
no, you get your deceitful ass on over to a shop.
>
>
>
>>>>
>>>>
>>>>> At best, you could perhaps get a little information on the
>>>>> outermost ply, often, not even that.
>>>>
>>>> bingo.
>>>
>>> That's your idea of a layup schedule?
>>
>> no. but you're my idea of an evasive prick.
>
> What about layup schedule (I already know your opinion of me)?
see above.
>
>
>
>>
>>>
>>>
>>>>>>> It's only when you exploit
>>>>>>> anisotropy that CF makes sense, but then you're stuck with lack of
>>>>>>> impact resistance and brittle failure as a trade off.
>>>>>>
>>>>>> but you have that kind of trade off with /any/ high strength
>>>>>> material, even steel. the higher the strength, the more brittle.
>>>>>
>>>>> You're missing the point about anisotropy.
>>>>
>>>> no i'm not. and that's a spectacular statement from a guy that
>>>> doesn't understand the difference between ductile elongation and
>>>> brittle fracture.
>>>
>>> Repeating that doesn't make it true.
>>
>> no, being true makes it true. repeating denial can't make it untrue.
>>
>>
>>> You, on the other hand, seem to be the only one on the planet who
>>> doesn't see that CFRP has low impact resistance.
>>
>> bullshit.
>>
>> 1. who the fuck wants their frame to be resistant to artillery fire.
>> 2. "impact resistance" is a function of the fiber itself, the layup,
>> the fiber length, density, orientation and matrix - among other
>> things. "CFRP has low impact resistance" is such a BULLSHIT dumb-ass
>> statement, it beggars belief.
>
> Then why does everyone believe it but you?
not everyone knows or cares. but that's why you muddy the water - so
you can keep on bullshitting.
>
>
>
>>>
>>>>>>> CF is great for
>>>>>>> some apps, marginal for others and crappy for the rest. It's an
>>>>>>> engineering thing.
>>>>>>
>>>>>> wow. condescension, massive over-generalization and naivety all
>>>>>> in one.
>>>>>
>>>>> No, just engineering basics. With CF bars and posts, you get (more
>>>>> expensive) parts with similar weights. You also get susceptibility
>>>>> to damage from clamping pressure and/or impact. Crappy (yet
>>>>> popular) applications.
>>>>
>>>> so when planes have warning labels on them telling crew not to walk
>>>> on wings, that can be ignored? bullshit. carbon componentry has
>>>> labels saying "do not clamp", "do not exceed...", etc., that can be
>>>> ignored? bullshit.
>>>
>>> Who said anything about ignoring labels? I was talking about the need
>>> for labels.
>>
>> so what would your labels say then? "er, this may be elastic or it
>> may be plastic - we really don't know"?
>
> That does not even make a shred of sense.
not knowing the distinction between the two deformation regimes you
mean? agreed - makes ZERO sense for anyone purporting to be an engineer.
>
>>>
>>>> twist all you want - you're still missing the basics.
>>>
>>> If you say so,
>>
>> damned right i say so!
>>
>> > but do try to scrape up a fact or two & perhaps we can go
>>> from there.
>>
>> i have. but you seem too intent on being a persistently ignorant
>> prick to absorb anything.
>
> I have yet to see a fact, only "jim beam"-ish self-cites. Perhaps
> they're the same in your world, but not in the much bigger world the
> rest of us live in.
that's such a crock. you don't know basic deformation theory and yet
base claims of denial on this fundamental ignorance. and when
confronted with fact, you deny. but all the while, you play to the
peanut gallery like you're the victim with this classic
passive-aggressive bullshit. you're a complete prick.
jim beam
and what's the warning from cannondale???
***
"This Manual contains many "Warnings" and "Cautions" concerning the
consequences of failure to maintain or
inspect your bicycle and of failure to follow safe cycling practices.
safety alert symbol and the word WARNING
indicates a potentially hazardous
The combination of the
situation which, if not avoided, could result in serious injury or death."
***
oh dear, aluminum. sounds like it's fatally brittle based on the legal b.s.
jim beam
er, i don't. within the context that you carefully snipped, what part
of "have you compared the strength of say an easton carbon post and your
steel post?" implies that i do? prick.
jim beam
bullshit.
jim beam
> jim beam wrote:
>
>> no, i'm "trying" to illustrate that a blanket statement like "carbon
>> is brittle" is way too ignorant and simplistic. it doesn't address
>> fatigue. it doesn't address stiffness. it doesn't address strength.
>
> Of course not silly, it only addresses impact strength. I hope we've
> cleared that up!
so, prick, just how much "impact" does a frame have to withstand to meet
your imaginary fear-factor? 0.45" hollow nose? 30mm incendiary? how
about 30mm du?
>
>
>> and even if we /are/ talking failure mode, we need to compare like
>> with like - saying that 6061 elongates 26% and carbon only 1.5%
>> completely misses the fundamental point that 24.5% of the aluminum's
>> deformation is plastic, not elastic!
>> and anything post-elastic is failure in these kinds of applications.
>
> Yes, and one is "brittle" failure, the other isn't. And that is why CF
> composite has lousy impact strength.
"impact" red herring bullshit. yield is what matters. if yield for
carbon is 3x yield for steel, who the fuck cares? prick.
>
> You are hopelessly confused between force and energy. You should have
> read my first post more carefully.
bullshit. coming from a prick that keeps bullshitting their way round
"brittleness" like they don't know a damned thing about it, you got some
hellish chutzpah.
Ted Bennett
jim beam <spamv...@bad.example.net> wrote:
Is that you, Ed Dolan?
--
Ted Bennett
Tim McNamara
<tedbennett-8A2AF...@earthlink.vsrv-sjc.supernews.net>,
Ted Bennett <tedbe...@earthlink.net> wrote:
> In article <-fCdnQ091PzMSE3b...@speakeasy.net>,
> jim beam <spamv...@bad.example.net> wrote:
>
> > Peter Cole wrote:
> > > jim beam wrote:
> > >> Peter Cole wrote: "6061 elongation is 26%". that's plastic
> > >> deformation. "carbon fiber elongation is 1.5%". that's elastic
> > >> deformation.
> > >>
> > >> there's a fundamental difference an "engineer" should
> > >> understand.
> > >
> > > Yes, that's obvious. Who said it wasn't?
> >
> > anyone mistaking plastic elongation for plastic elongation
> > /clearly/ doesn't find the distinction "obvious".
> >
> > > You don't have to put quotes around engineer.
> >
> > you do if it's a name someone calls themselves, but doesn't
> > evidence qualification.
OMG that is *so* f'in funny! Thanks, Ted, I wouldn't have seen this
without your help!
Peter Cole
From:
<http://www.exponent.com/about/docs/ISASI2006_paper.pdf>
Composites have design variables that are not available in metals. Some of
these variables are fiber orientation, fiber-to-matrix volume ratio, ply
thickness,
and ply stacking sequence, among others. With new variables come new
opportunities for manufacturing errors or imperfections. Some of these
imperfections are fiber waviness, poor adhesion between fibers and
matrix, poor
adhesion between plies, excessive voids in the matrix, and an improperly
cured
matrix, among others. Changes in design variables and accumulated
imperfections directly affect the failure of a composite.
For example, Figure 5 shows twenty failed composite specimens, four
groups of
five specimens, representing four different ply-wise fiber orientations.
Each
specimen was subjected to simple tensile loading. Despite the similarity in
loading, the failure in each specimen looks unique. Some of the failed
specimens have a shredded appearance with a very rough fracture surface;
some of the specimens have a smoother, angular appearance. Some specimens
even broke into three pieces, rather than two. The differences in the
appearance
of these failures are a result of two primary sources of variation among the
specimens. The first source of variation is the intentional variation in
design
variables, in this case, fiber orientation. The second source of
variation is the
accumulation of imperfections, as discussed above. The result is that these
composites, all of which failed in tension, appear very different from
each other.
As discussed above, typical aircraft composites are brittle rather than
ductile.
Ductile metal structures undergo relatively high levels of permanent
deformation
prior to final failure and this deformation provides information
regarding the
events preceding structural failure. As brittle structures, composites
exhibit
relatively little permanent deformation prior to final failure. The
metallic aircraft
discussed above and shown in Figure 3 provides a clear indication of
impact by a
foreign object. Impact evidence may not be as readily observed in a
composite
structure.
In fact, impact loading can cause damage to a composite without any visible
evidence on the surface. Consider an aircraft mechanic dropping a wrench on
the top surface of a wing. If the wing is made of aluminum, the impact
may leave
a dent, essentially recording the impact and providing some rudimentary
indication of the significance of the resultant damage. If the wing is a
brittle
composite, the impact of the wrench may produce local crushing of the
fibers and
matrix or it may not produce any damage on the surface at all. In either
case, the
level of damage below the surface of a composite can be much more extensive
than that indicated on the surface.
One common type of sub-surface damage from impact is delamination. A
delamination is a split between plies in a composite. The split can
propagate
along the interface at which neighboring plies were joined during
manufacturing,
or it can propagate along the fiber-matrix interface. Figure 11 shows a
couple
views of the cross-section of a composite plate after impact. As
indicated in the
figures, the impact caused extensive delamination among multiple plies. Such
damage can dramatically degrade the load bearing capability of the composite
even though the fibers may remain intact. Moreover, the damage, if
unnoticed,
can continue to propagate upon further loading of the composite.
Without visible evidence on the surface, delaminations must be identified by
cross-sectioning the composite in the location of the delamination or by
employing non-destructive techniques such as ultrasonics or x-ray
tomography.
If destructive techniques are employed, delaminations may be identified
visually.
In graphite-epoxy composites, delaminations can be identified by a dull,
whitish
appearance, relative to the shiny, black appearance of neighboring areas
free
from delamination.
Peter Cole
How do you compare strengths of two seatposts without knowing either
strength?
Peter Cole
It doesn't say that at all. You're just making things up. The complete
Cannondale manual is at:
<http://www.cannondale.com/asset/iu_files/techcenter/2006_cannondale_owners_manual_en.pdf>
(the part about frames & forks is on page 90).
Peter Cole
> that's such a crock. you don't know basic deformation theory and yet
> base claims of denial on this fundamental ignorance. and when
> confronted with fact, you deny. but all the while, you play to the
> peanut gallery like you're the victim with this classic
> passive-aggressive bullshit. you're a complete prick.
Let's drop all the infantile name calling and cut to the chase, shall
we? Your claim that CF composite is not brittle is contrary to every
source I have seen, to say that yours is a minority viewpoint would be
to give it too much credit. You're dead wrong and only resort to this
nonsense to try to bluff your way out. Nobody's buying it.
jim beam
bullshit - that was a direct cut and paste quote from their online pdf.
/your/ link in fact.
> The complete
> Cannondale manual is at:
> <http://www.cannondale.com/asset/iu_files/techcenter/2006_cannondale_owners_manual_en.pdf>
>
>
> (the part about frames & forks is on page 90).
yeah, and look on page 4, bullshitter, "general warning".
jim beam
what's your source? conan o'brien's mom?
carbon composites are not brittle like glass is brittle, which is what
you seem to want us to believe. "brittle" is defined by energy
absorption on fracture and the deformation mechanism.
jim beam
/i/ don't. the /user/ does. prick.
jim beam
that is a marketing piece designed to fear-monger their way into getting
more consulting business!!! "omg, the service tech /sneezed/ when
torquing that bolt - you need our special torque analysis consulting
services".
jeeze, trying to use that as authority on material properties is just
ridiculous. but you're a prick, so we'd expect stuff like that from you.
frkr...@gmail.com
>
> prick...
>
> ... prick.
>
> ... prick ...
>
> prick...
>
> ... prick.
>
> ... prick ...
>
> prick...
>
> ... prick.
>
> ... prick ...
That's the sign that jim beam's lost yet another technical
argument. ;-)
- Frank Krygowski
jim beam
J. Clarke
You aren't by any chance the idiot who talked the management at
Rolls-Royce into betting the company on carbon fiber fan blades, are
you?
--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
Ted Bennett
Ted Bennett
Tim McNamara <tim...@bitstream.net> wrote:
I did not write anything you quoted.
Ted Bennett
--
Ted Bennett
Tim McNamara
<tedbennett-01DFD...@earthlink.vsrv-sjc.supernews.net>,
Ted Bennett <tedbe...@earthlink.net> wrote:
Indeed. You'd think he'd get tired of disgracing himself, but the joy
of being a sock puppet is never having to admit you're wrong.
Tim McNamara
<tedbennett-17FA3...@earthlink.vsrv-sjc.supernews.net>,
Ted Bennett <tedbe...@earthlink.net> wrote:
> In article <timmcn-1F9FF8....@news.iphouse.com>,
> Tim McNamara <tim...@bitstream.net> wrote:
>
> > In article
> > <tedbennett-8A2AF...@earthlink.vsrv-sjc.supernews.net>,
> > Ted Bennett <tedbe...@earthlink.net> wrote:
> >
> > > In article <-fCdnQ091PzMSE3b...@speakeasy.net>,
> > > jim beam <spamv...@bad.example.net> wrote:
> > >
> > > > Peter Cole wrote:
> > > > > jim beam wrote:
> > > > >> Peter Cole wrote: "6061 elongation is 26%". that's plastic
> > > > >> deformation. "carbon fiber elongation is 1.5%". that's elastic
> > > > >> deformation.
> > > > >>
> > > > >> there's a fundamental difference an "engineer" should
> > > > >> understand.
> > > > >
> > > > > Yes, that's obvious. Who said it wasn't?
> > > >
> > > > anyone mistaking plastic elongation for plastic elongation
> > > > /clearly/ doesn't find the distinction "obvious".
> > > >
> > > > > You don't have to put quotes around engineer.
> > > >
> > > > you do if it's a name someone calls themselves, but doesn't
> > > > evidence qualification.
> >
> > OMG that is *so* f'in funny! Thanks, Ted, I wouldn't have seen this
> > without your help!
>
> I did not write anything you quoted.
True, I trimmed most of the post. It was just by way of thanking you
because jim beam lives in my killfile. I don't get to see such pearls
as this unless someone quotes it. This one was priceless!
Jay Beattie
I've used Exponent fka Failure Analysis. I was down there a while back
on a case involving a broken MTB frame. While I was getting a tour of
their facilities, I watched them do fatigue testing on a bunch of
products for Specialized -- stems and bars as I recall. It's
interesting to see in person the fatique testing one hears about. On
my case, the client wanted the full boat and got it -- including
rigging a similar frame with strain gagues and accelerometers (or
whatever the instrumentation was) and having a national class mountain
biker ride it over rough terrain with a back pack filled with
electronics to record the data. They wanted to see what real-world
stresses were. Anyway, fear mongering or not, Exponent is a heavy
hitter, and if a manufacturer does not pay attention to what they say
and something breaks because of it, good luck defending. You may not
think much of them as a source, but a lot of people in the
manufacturing world do.-- Jay Beattie
jim beam
um, what they do is perfectly fine - that's not what i'm saying. the
cited article was a sales pitch. it wasn't an authoritative case study.
n.d.t. is essential and what keeps the airplane industry flying. and
there are many providers of these services. that means competitive
"sales". hence fluffy articles that are aimed at those worried about
covering their ass.
Jambo
"jim beam" <spamv...@bad.example.net> wrote in message
news:9P6dnWD_mKCaqE_b...@speakeasy.net...
> Jay Beattie wrote:
>> Anyway, fear mongering or not, Exponent is a heavy
>> hitter, and if a manufacturer does not pay attention to what they say
>> and something breaks because of it, good luck defending. You may not
>> think much of them as a source, but a lot of people in the
>> manufacturing world do.-- Jay Beattie
>>
>
> um, what they do is perfectly fine - that's not what i'm saying. the
> cited article was a sales pitch. it wasn't an authoritative case study.
>
> n.d.t. is essential and what keeps the airplane industry flying. and
> there are many providers of these services. that means competitive
> "sales". hence fluffy articles that are aimed at those worried about
> covering their ass.
Low damage tolerance of CFRPs and CFPs, compared to other materials
(especially metals), are well established facts in the aerospace industry
for decades now. Large effort has been, and are still being expended, in
characterizing damage tolerance and early detection of damage because the
consequences of even low impact, low energy damage to carbon composites,
especially those that are not visible to the eye, are quite severe compared
to metals. There is a plethora of literature stating this fact, some
samples below:
http://pdf.aiaa.org/preview/1988/PV1988_2292.pdf
http://journalsip.astm.org/JOURNALS/COMPTECH/PAGES/143.htm
http://www.ingentaconnect.com/content/klu/jmsc/2006/00000041/00000020/00000208?crawler=true
http://www.scientific.net/0-87849-839-7/1/
It's NDI, not NDT, that is imperative in maintaining aircraft with both
metallic and composite components. The fact that there are many companies
providing this service specifically for carbon composites, and that much
research is ongoing on more reliable and earlier non-eyeball detection of
damage to CFRPs, are all indications of the necessity of these techniques
for assuring structural integrity of CFRPs. How much damage is caused by
how much impact? Damage to bike CRFP frames due to low energy, low
velocity impacts can be correlated with aerospace application studies and
findings using similar composites, and consequently the only way to
determine structural integrity of CRFP frames after impact or indentations
(without visible damage) is through NDI. A lot of hassle, expense and worry
just for a bicycle, where Al alloys already do a good job.
jim beam
> "jim beam" <spamv...@bad.example.net> wrote in message
> news:9P6dnWD_mKCaqE_b...@speakeasy.net...
>> Jay Beattie wrote:
>>> Anyway, fear mongering or not, Exponent is a heavy
>>> hitter, and if a manufacturer does not pay attention to what they say
>>> and something breaks because of it, good luck defending. You may not
>>> think much of them as a source, but a lot of people in the
>>> manufacturing world do.-- Jay Beattie
>>>
>> um, what they do is perfectly fine - that's not what i'm saying. the
>> cited article was a sales pitch. it wasn't an authoritative case study.
>>
>> n.d.t. is essential and what keeps the airplane industry flying. and
>> there are many providers of these services. that means competitive
>> "sales". hence fluffy articles that are aimed at those worried about
>> covering their ass.
>
> Low damage tolerance of CFRPs and CFPs, compared to other materials
> (especially metals), are well established facts in the aerospace industry
> for decades now.
language like "low damage tolerance" doesn't recognize that it's much
harder to damage in the first place. it also makes no recognition of
fatigue, a field in which composites are much superior.
> Large effort has been, and are still being expended, in
> characterizing damage tolerance and early detection of damage because the
> consequences of even low impact, low energy damage to carbon composites,
> especially those that are not visible to the eye, are quite severe compared
> to metals. There is a plethora of literature stating this fact, some
> samples below:
> http://pdf.aiaa.org/preview/1988/PV1988_2292.pdf
> http://journalsip.astm.org/JOURNALS/COMPTECH/PAGES/143.htm
> http://www.ingentaconnect.com/content/klu/jmsc/2006/00000041/00000020/00000208?crawler=true
> http://www.scientific.net/0-87849-839-7/1/
>
> It's NDI, not NDT,
depends who you talk with.
> that is imperative in maintaining aircraft with both
> metallic and composite components. The fact that there are many companies
> providing this service specifically for carbon composites, and that much
> research is ongoing on more reliable and earlier non-eyeball detection of
> damage to CFRPs, are all indications of the necessity of these techniques
> for assuring structural integrity of CFRPs. How much damage is caused by
> how much impact? Damage to bike CRFP frames due to low energy, low
> velocity impacts can be correlated with aerospace application studies and
> findings using similar composites, and consequently the only way to
> determine structural integrity of CRFP frames after impact or indentations
> (without visible damage) is through NDI. A lot of hassle, expense and worry
> just for a bicycle, where Al alloys already do a good job.
otoh:
1. the ndi/t industry for aerospace /started/ with the need to detect
and prevent fatigue in /metals/.
2. despite all the doomsdayers, carbon forks have shown no greater
failure rates than their metal counterparts.
3. for racing, cfrp offers a better specific modulus than any other
material.
bottom line, cfrp for bike forks have been so successful, almost /all/
bikes now use it. over a decade of of use, millions of rider miles,
etc. if there was a real problem, it would be manifest by now.
[isolated q.c. issues aside of course, but that's an issue for any
material, any application.]
Peter Cole
Oh, please -- now the "ad absurdum" approach. No one is claiming a CF
composite plate or tube is like a glass plate or tube, or that a CF bike
is like one made of glass. The comparison is to other materials commonly
used for bicycle/component manufacture -- steel, aluminum and
titanium. In comparison to those materials, CF is indeed brittle, and
has much lower impact resistance.
<http://www.substech.com/dokuwiki/doku.php?id=carbon_fiber_reinforced_polymer_composites>
The main disadvantage of carbon (graphite) fibers is catastrophic mode
of failure (carbon fibers are brittle).
Carbon Fiber Reinforced Polymers (CFRP) are characterized by the
following properties:
*
Light weight;
*
High strength-to-weight ratio;
*
Very High modulus elasticity-to-weight ratio;
*
High Fatigue strength;
*
Good corrosion resistance;
*
Very low coefficient of thermal expansion;
*
Low impact resistance;
*
High electric conductivity;
*
High cost.
<http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA036566>
"The studies with the carbon fiber composites reveal the brittle nature
of this material, particularly when compared to the glass fiber composites."
<http://en.wikipedia.org/wiki/Tensile_strength>
"Brittle materials such as concrete and carbon fiber do not have a yield
point, and do not strain-harden which means that the ultimate strength
and breaking strength are the same. A most unusual stress-strain curve
is shown in the figure below. Typical brittle materials do not show any
plastic deformation but fail while the deformation is elastic. One of
the characteristics of a brittle failure is that the two broken parts
can be reassembled to produce the same shape as the original component.
A typical stress strain curve for a brittle material will be linear."
<http://machinedesign.com/BDE/materials/bdemat3/bdemat3_2.html>
"The outstanding design properties of carbon fiber/resin matrix
composites are their high strength-to-weight and stiffness-to-weight
ratios. With proper selection and placement of fibers, the composites
can be stronger and stiffer than equivalent thickness steel parts and
weigh 40 to 70% less. Fatigue resistance of continuous-fiber composites
is excellent, and chemical resistance is better than that of
glass-reinforced systems, particularly in alkaline environments. Like
most rigid materials, however, carbon-fiber composites are relatively
brittle. The composites have no yield behavior, and resistance to impact
is low."
A rather good primer:
<http://www.advancedcomposites.com/technology.htm>
Says what I have been saying:
"The primary advantage of composite materials over more conventional
metallic or polymeric materials is their anisotropic mechanical
response. This resulting directionality is carefully used to advantage."
And:
"Figures 11. and 12. Illustrate how dramatically the properties of
plus/minus angle laminates change versus angle."
Also an overview of failure mechanisms.
Peter Cole
OK, how does he do it?
Peter Cole
Sure, the quote, but not your interpretation.
>
>
>> The complete Cannondale manual is at:
>> <http://www.cannondale.com/asset/iu_files/techcenter/2006_cannondale_owners_manual_en.pdf>
>>
>>
>> (the part about frames & forks is on page 90).
>
> yeah, and look on page 4, bullshitter, "general warning".
Says nothing about materials. There are sections (page 90) specifically
about frame & fork inspection. They warn against riding cracked frames
-- they don't raise the same kind of warnings Trek does. This does not
support your claim that Cannondale says aluminum frames are as brittle
and impact intolerant as Trek says its CF frames are.
Peter Cole
> Peter Cole wrote:
>> From:
>> <http://www.exponent.com/about/docs/ISASI2006_paper.pdf>
> that is a marketing piece designed to fear-monger their way into getting
> more consulting business!!! "omg, the service tech /sneezed/ when
> torquing that bolt - you need our special torque analysis consulting
> services".
>
> jeeze, trying to use that as authority on material properties is just
> ridiculous. but you're a prick, so we'd expect stuff like that from you.
You're missing the point, which was that CF impact damage often isn't
obvious, nor easily detected without special equipment.
Why don't you drop the "prick" stuff. It's infantile and nobody's
digging it.
Peter Cole
> Jay Beattie wrote:
>> I've used Exponent fka Failure Analysis. I was down there a while back
>> on a case involving a broken MTB frame. While I was getting a tour of
>> their facilities, I watched them do fatigue testing on a bunch of
>> products for Specialized -- stems and bars as I recall. It's
>> interesting to see in person the fatique testing one hears about. On
>> my case, the client wanted the full boat and got it -- including
>> rigging a similar frame with strain gagues and accelerometers (or
>> whatever the instrumentation was) and having a national class mountain
>> biker ride it over rough terrain with a back pack filled with
>> electronics to record the data. They wanted to see what real-world
>> stresses were. Anyway, fear mongering or not, Exponent is a heavy
>> hitter, and if a manufacturer does not pay attention to what they say
>> and something breaks because of it, good luck defending. You may not
>> think much of them as a source, but a lot of people in the
>> manufacturing world do.-- Jay Beattie
>>
>
> um, what they do is perfectly fine - that's not what i'm saying. the
> cited article was a sales pitch. it wasn't an authoritative case study.
>
> n.d.t. is essential and what keeps the airplane industry flying. and
> there are many providers of these services. that means competitive
> "sales". hence fluffy articles that are aimed at those worried about
> covering their ass.
Did you even read the article? Most of it was about determining the
cause of a failure from the evidence presented by the failed part, and
how that's a very different problem switching between metals and
composites. In the context of failure "forensics", it's necessary to
catalog the various failure modes, both sudden and gradual. You seem to
have a problem with anyone who even considers the possibility of CF failure.
It was anything but "fluffy".
Peter Cole
I think it's a perfectly valid question, given the increasing presence
of critical CF components, to ask whether or not it's practical for a
bike owner to detect damage. So far, the weight of evidence seems to
indicate that it's not. Material failure in a fork is a lot more serious
than a tennis racket or golf club.
Jambo
> Jambo wrote:
>> Low damage tolerance of CFRPs and CFPs, compared to other materials
>> (especially metals), are well established facts in the aerospace industry
>> for decades now.
>
> language like "low damage tolerance" doesn't recognize that it's much
> harder to damage in the first place. it also makes no recognition of
> fatigue, a field in which composites are much superior.
If you read some of the numerous articles over the last decade on the
subject, you can get a pretty good idea of what "low damage tolerance" is.
It refers to impact damage on the carbon composites from a different
direction to the component design loading - e.g. impact on a flat panel,
perpendicular to the plane of the panel. In terms of bike components, e.g.
forks, impact on the forks perpendicular to the legs, such as what happens
in the course of handling the bike. We're not talking about damage due to
loading of the component as designed - if the component has been designed
correctly, CFRPs do a very good job of taking up the load it's been made
for.
CFRPs do exhibit superior fatigue properties from metals, if designed
correctly. However, much work that's been done so far in the last few
decades address the fact that structural integrity of CFRPs are much easier
to compromise than metals due to impacts such as above; this is what makes
CFRPs easier to damage. There are whole industries spawned in CFRP
structural integrity because of CFRPs inherent low impact damage tolerance
to loads from different directions to intended.
>> It's NDI, not NDT,
>
> depends who you talk with.
Non-Destructive Inspection is what maintainers do with composites.
Non-Destructive Testing is what manufacturers do prior to introducing
components into service. I am talking about structural integrity monitoring
and inspection of CFRPs.
> 1. the ndi/t industry for aerospace /started/ with the need to detect and
> prevent fatigue in /metals/.
This is unrelated to the fact that CFRPs require much more rigorous
inspections than metals; in fact, NDI techniques for CFRPs are quite
different than those for metals.
> 2. despite all the doomsdayers, carbon forks have shown no greater failure
> rates than their metal counterparts.
Carbon fiber forks have been in service for much shorter, in much less
numbers than metal forks. Jury is still out on this.
> 3. for racing, cfrp offers a better specific modulus than any other
> material.
That's a weight weenie issue, and I don't want to get into that.
> bottom line, cfrp for bike forks have been so successful, almost /all/
> bikes now use it.
It's hard to see that "almost all bikes" use it. There are so many more
bikes with metal forks than carbon - a visit to any bike shop, and bike
manufacturer websites, show that most bikes on offer have metal forks.
> over a decade of of use, millions of rider miles,
"Millions of rider miles" is speculative.
> etc. if there was a real problem, it would be manifest by now.
If we had a database that's easily accessible by the public, of carbon fork
failures, then that statement might be more confidence inspiring. On the
other hand, failures of other carbon bike components such as handlebars and
seatposts have many testimonials - do a search on mtbr.com.
Peter Cole
> bottom line, cfrp for bike forks have been so successful, almost /all/
> bikes now use it. over a decade of of use, millions of rider miles,
> etc. if there was a real problem, it would be manifest by now.
> [isolated q.c. issues aside of course, but that's an issue for any
> material, any application.]
No numbers, of course, just "jim beam" "facts".
Check out <http://www.mtbr.com/reviews/Seatpost/product_22777.shtml> for
failures of Easton CT2 CF seat posts. Lots of failures. Easton's hardly
a fly-by-night company. Posts are an easier application than forks. Lots
of CF posts out there despite little "performance" gain and higher cost.
Dumb application for CF.
Check out <http://www.mtbr.com/reviews/Handlebar/product_21876.shtml>
for failures of Scott CF handlebars. Lots of failures. Even easier
application. Dumb application for CF.
Many fewer reviews of CF cranks, but more reports of snapped arms than
Al cranks.
Pay special attention to the prevalence of sudden catastrophic failures
(reported by actual victims). This is what CF does.
Where's the "headroom"? Where's the "2x lighter, 3x stronger"?
Michael Press
<ibydnT7_eJuZ5Ezb...@comcast.com>,
Peter Cole <peter...@comcast.net> wrote:
> Composites have design variables that are not available in metals. Some of
> these variables are fiber orientation, fiber-to-matrix volume ratio, ply
> thickness,
> and ply stacking sequence, among others. With new variables come new
> opportunities for manufacturing errors or imperfections. Some of these
> imperfections are fiber waviness, poor adhesion between fibers and
> matrix, poor
> adhesion between plies, excessive voids in the matrix, and an improperly
> cured
> matrix, among others. Changes in design variables and accumulated
> imperfections directly affect the failure of a composite.
This is studied under the topic of imperfection
instability. It is well understood, if not widely
understood. Successive optimizations in the design of
an elastic structure do not simply add to the
imperfection stability, but change the exponent for the
worse. Look up "box girder" and "box girder bridge".
It can also be viewed from the stand-point of failure
modes. If the structure fails in its principal mode,
what aspect of the structure now takes up the load?
--
Michael Press
Tim McNamara
wrote:
> "jim beam" <spamv...@bad.example.net> wrote in message
> news:WeqdnfpxWcGyVk_b...@speakeasy.net...
> > 2. despite all the doomsdayers, carbon forks have shown no greater
> > failure rates than their metal counterparts.
>
> Carbon fiber forks have been in service for much shorter, in much
> less numbers than metal forks. Jury is still out on this.
We have already had more reports in this newsgroup of failed CF steerer
tubes than steel steerer tubes, despite the short deployment time of
all-CF forks.
Tom "Johnny Sunset" Sherman
> ...
> anyone mistaking plastic elongation for plastic elongation /clearly/
> doesn't find the distinction "obvious".
Gee, truisms are false? I always thought that "plastic elongation" was
the same as "plastic elongation".
> ...ZERO....
HIS KEYBOARD DOES HAVE CAPITAL LETTERS!
--
Tom Sherman - Holstein-Friesland Bovinia
--
Posted via a free Usenet account from http://www.teranews.com
Tom "Johnny Sunset" Sherman
>> jim beam wrote:
>>
>>
>> But CF always is!
>
> bullshit.
That substance is ductile when wet, but becomes brittle when dry.
jim beam
ah, the peter cole approach: "keep trying to baffle them with bull".
since this is the fundamental intellectual hurdle you can't seem to
overcome, let's cut to the point - you go ahead and define "brittle".
and /please/ try not to deceive by citing anisotropy as evidence. thank
you.
jim beam
oh dear, funny how when something doesn't suit /you/ it doesn't seem to
count...
>
>>
>>
>>> The complete Cannondale manual is at:
>>> <http://www.cannondale.com/asset/iu_files/techcenter/2006_cannondale_owners_manual_en.pdf>
>>>
>>>
>>> (the part about frames & forks is on page 90).
>>
>> yeah, and look on page 4, bullshitter, "general warning".
>
> Says nothing about materials. There are sections (page 90) specifically
> about frame & fork inspection. They warn against riding cracked frames
> -- they don't raise the same kind of warnings Trek does. This does not
> support your claim that Cannondale says aluminum frames are as brittle
> and impact intolerant as Trek says its CF frames are.
s'funny, i don't see trek's legal department cited in any of the
materials lit i have. oh, it's because it's just legal bullshit, not
authoritative materials research!!! how damned inconvenient.
jim beam
> jim beam aka evan williams wrote:
>> ...
>> anyone mistaking plastic elongation for plastic elongation /clearly/
>> doesn't find the distinction "obvious".
>
> Gee, truisms are false? I always thought that "plastic elongation" was
> the same as "plastic elongation".
that's a typo. and you know it.
>
>> ...ZERO....
>
> HIS KEYBOARD DOES HAVE CAPITAL LETTERS!
>
genius.
jim beam
how do you keep trying to avoid the point and not think you're being a
prick?
jim beam
from over-zealous stem clamping, not from road force.
jim beam
> "jim beam" <spamv...@bad.example.net> wrote in message
> news:WeqdnfpxWcGyVk_b...@speakeasy.net...
>> Jambo wrote:
>>> Low damage tolerance of CFRPs and CFPs, compared to other materials
>>> (especially metals), are well established facts in the aerospace industry
>>> for decades now.
>> language like "low damage tolerance" doesn't recognize that it's much
>> harder to damage in the first place. it also makes no recognition of
>> fatigue, a field in which composites are much superior.
>
> If you read some of the numerous articles over the last decade on the
> subject, you can get a pretty good idea of what "low damage tolerance" is.
> It refers to impact damage on the carbon composites from a different
> direction to the component design loading - e.g. impact on a flat panel,
> perpendicular to the plane of the panel. In terms of bike components, e.g.
> forks, impact on the forks perpendicular to the legs, such as what happens
> in the course of handling the bike. We're not talking about damage due to
> loading of the component as designed - if the component has been designed
> correctly, CFRPs do a very good job of taking up the load it's been made
> for.
so what is it to be? does the witching word "carbon" somehow mean we
use different standards of evaluation? when i clamp a beer-can-thin
aluminum frame and dent the tube, that's ok, but clamping a carbon tube
might not be - just in case it's cracked but we really don't know???
>
> CFRPs do exhibit superior fatigue properties from metals, if designed
> correctly. However, much work that's been done so far in the last few
> decades address the fact that structural integrity of CFRPs are much easier
> to compromise than metals due to impacts such as above; this is what makes
> CFRPs easier to damage. There are whole industries spawned in CFRP
> structural integrity because of CFRPs inherent low impact damage tolerance
> to loads from different directions to intended.
so don't load them other than as intended! and enjoy the superior
fatigue resistance.
>
>>> It's NDI, not NDT,
>> depends who you talk with.
>
> Non-Destructive Inspection is what maintainers do with composites.
> Non-Destructive Testing is what manufacturers do prior to introducing
> components into service. I am talking about structural integrity monitoring
> and inspection of CFRPs.
which is simply uneconomic for bikes, regardless of material.
>
>> 1. the ndi/t industry for aerospace /started/ with the need to detect and
>> prevent fatigue in /metals/.
>
> This is unrelated to the fact that CFRPs require much more rigorous
> inspections than metals;
no it's not. you're bleating about cfrp as if it's flawed, yet you're
glossing over the need to extensively check and test metals. /and/ not
addressing the degree to which metals have much inferior fatigue and
thus greater /need/ for inspection.
> in fact, NDI techniques for CFRPs are quite
> different than those for metals.
indeed, but that's not the point.
>
>> 2. despite all the doomsdayers, carbon forks have shown no greater failure
>> rates than their metal counterparts.
>
> Carbon fiber forks have been in service for much shorter, in much less
> numbers than metal forks. Jury is still out on this.
how much longer does the jury have to be out?
>
>> 3. for racing, cfrp offers a better specific modulus than any other
>> material.
>
> That's a weight weenie issue, and I don't want to get into that.
>
>> bottom line, cfrp for bike forks have been so successful, almost /all/
>> bikes now use it.
>
> It's hard to see that "almost all bikes" use it. There are so many more
> bikes with metal forks than carbon - a visit to any bike shop, and bike
> manufacturer websites, show that most bikes on offer have metal forks.
>
>> over a decade of of use, millions of rider miles,
>
> "Millions of rider miles" is speculative.
yes, it's an under estimate. i personally have over 10k on a carbon
fork. find another 100 riders like me, that's 1M rider miles. now,
/how/ many people ride such a bike?
>
>> etc. if there was a real problem, it would be manifest by now.
>
> If we had a database that's easily accessible by the public, of carbon fork
> failures, then that statement might be more confidence inspiring. On the
> other hand, failures of other carbon bike components such as handlebars and
> seatposts have many testimonials - do a search on mtbr.com.
in theory, i'd agree, but since this is r.b.t., and the proles here
don't hesitate to bleat about /any/ imaginary problem they think they
find - disk brakes on mtb's for example - i think we'd have heard before
now if there was much to complain about.
jim beam
> jim beam wrote:
>> Peter Cole wrote:
>
>>> From:
>>> <http://www.exponent.com/about/docs/ISASI2006_paper.pdf>
>
>> that is a marketing piece designed to fear-monger their way into
>> getting more consulting business!!! "omg, the service tech /sneezed/
>> when torquing that bolt - you need our special torque analysis
>> consulting services".
>>
>> jeeze, trying to use that as authority on material properties is just
>> ridiculous. but you're a prick, so we'd expect stuff like that from you.
>
> You're missing the point, which was that CF impact damage often isn't
> obvious, nor easily detected without special equipment.
so how many aluminum cranks fatigue and break without the rider being
aware? frames? handlebars?
>
> Why don't you drop the "prick" stuff. It's infantile and nobody's
> digging it.
then stop being a prick!
Peter Cole
I've provided citations. Your turn.
>
> since this is the fundamental intellectual hurdle you can't seem to
> overcome, let's cut to the point - you go ahead and define "brittle".
It was defined above. Apparently you don't even read my posts.
> and /please/ try not to deceive by citing anisotropy as evidence. thank
> you.
It makes no sense to ignore anisotropy since that's a primary
characteristic.
Peter Cole
Your interpretation is not supported by your quote.
>
>
>>
>>>
>>>
>>>> The complete Cannondale manual is at:
>>>> <http://www.cannondale.com/asset/iu_files/techcenter/2006_cannondale_owners_manual_en.pdf>
>>>>
>>>>
>>>> (the part about frames & forks is on page 90).
>>>
>>> yeah, and look on page 4, bullshitter, "general warning".
>>
>> Says nothing about materials. There are sections (page 90)
>> specifically about frame & fork inspection. They warn against riding
>> cracked frames -- they don't raise the same kind of warnings Trek
>> does. This does not support your claim that Cannondale says aluminum
>> frames are as brittle and impact intolerant as Trek says its CF frames
>> are.
>
> s'funny, i don't see trek's legal department cited in any of the
> materials lit i have. oh, it's because it's just legal bullshit, not
> authoritative materials research!!! how damned inconvenient.
Yeah, I know, everything that you don't agree with is "bullshit". No
news there.
Peter Cole
Your point, your avoidance. Strength numbers are not published for seat
posts, nor is there any practical way for a user to estimate them. Your
turn. Put up or shut up.
Peter Cole
Burden of proof is on you.
Peter Cole
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>
>>>> From:
>>>> <http://www.exponent.com/about/docs/ISASI2006_paper.pdf>
>>
>>> that is a marketing piece designed to fear-monger their way into
>>> getting more consulting business!!! "omg, the service tech /sneezed/
>>> when torquing that bolt - you need our special torque analysis
>>> consulting services".
>>>
>>> jeeze, trying to use that as authority on material properties is just
>>> ridiculous. but you're a prick, so we'd expect stuff like that from
>>> you.
>>
>> You're missing the point, which was that CF impact damage often isn't
>> obvious, nor easily detected without special equipment.
>
> so how many aluminum cranks fatigue and break without the rider being
> aware? frames? handlebars?
Why don't you just address the point of the article -- namely that CF
composite is impossible to inspect without special equipment?
Metal components crack, but at least you have a chance of inspecting for
cracks.
>
>>
>> Why don't you drop the "prick" stuff. It's infantile and nobody's
>> digging it.
>
> then stop being a prick!
Grow up.
jim beam
yes i did, and there is no definition of brittle, only use of the term,
in context no less. but you won't define the term because it won't suit
your purpose of deceit.
>
>
>> and /please/ try not to deceive by citing anisotropy as evidence.
>> thank you.
>
> It makes no sense to ignore anisotropy since that's a primary
> characteristic.
but you're citing anisotropy as if it's somehow "evidence" of
brittleness. it's not.
jim beam
more bullshit. you attempted to deceive, and failed.
jim beam
no, a user bleats that a cfrp post is "weak". i ask whether they've
compared strength. so where the fuck do /i/ have an obligation to
test??? you're such a prick.
jim beam
eh? if the steer tube shows longitudinal cracking at the stem clamp,
where the two pieces being clamped meet, there's not much "proof"
required. prick.
jim beam
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>> Peter Cole wrote:
>>>
>>>>> From:
>>>>> <http://www.exponent.com/about/docs/ISASI2006_paper.pdf>
>>>
>>>> that is a marketing piece designed to fear-monger their way into
>>>> getting more consulting business!!! "omg, the service tech
>>>> /sneezed/ when torquing that bolt - you need our special torque
>>>> analysis consulting services".
>>>>
>>>> jeeze, trying to use that as authority on material properties is
>>>> just ridiculous. but you're a prick, so we'd expect stuff like that
>>>> from you.
>>>
>>> You're missing the point, which was that CF impact damage often isn't
>>> obvious, nor easily detected without special equipment.
>>
>> so how many aluminum cranks fatigue and break without the rider being
>> aware? frames? handlebars?
>
> Why don't you just address the point of the article -- namely that CF
> composite is impossible to inspect without special equipment?
unimpressive red herring bullshit. metal needs special equipment for
inspection. and even if visible cracks are evident to some people,
they're ignored by those who are not familiar with the signs. so it
amounts to exactly the same thing - /both/ need expert assessment.
>
> Metal components crack, but at least you have a chance of inspecting for
> cracks.
and you can hear carbon's audible warnings. or is that too inconvenient
to admit?
>
>>
>>>
>>> Why don't you drop the "prick" stuff. It's infantile and nobody's
>>> digging it.
>>
>> then stop being a prick!
>
> Grow up.
not being a prick is too difficult?
Tim McNamara
Peter Cole <peter...@comcast.net> wrote:
Especially since several of the reports have been of fractures at the
fork crown end, not the area where the stem is clamped onto the steerer,
which resulted in the fork separating from the bike. "Over-zealous stem
clamping" has nothing to do with it. Obviously jim has not been keeping
up with the times. He also remains happily oblivious to the rather
obvious fact that if CF lacks the material properties to withstand an
extra turn on a bolt in a clamp, it is overly susceptible to damage and
lacks an adequate margin of safety. I am indebted to him, however, for
corroborating my opinion that CF is simply not an appropriate material
for critical bicycle parts.
Jambo
> Jambo wrote:
>> If you read some of the numerous articles over the last decade on the
>> subject, you can get a pretty good idea of what "low damage tolerance"
>> is. It refers to impact damage on the carbon composites from a different
>> direction to the component design loading - e.g. impact on a flat panel,
>> perpendicular to the plane of the panel. In terms of bike components,
>> e.g. forks, impact on the forks perpendicular to the legs, such as what
>> happens in the course of handling the bike. We're not talking about
>> damage due to loading of the component as designed - if the component has
>> been designed correctly, CFRPs do a very good job of taking up the load
>> it's been made for.
>
> so what is it to be? does the witching word "carbon" somehow mean we use
> different standards of evaluation?
Yes, precisely. We've gone over the reasons for this previously. Let's
summarize. For impact loads in different directions other than duty loads
(e.g. dents in tubes):
1. In the elastic deformation range, carbon fiber composites and Al alloys
have similar stress/strain properties. No issues there.
2. In the plastic deformation range, CFCs fail catastrophically compared to
Al alloys - elongation to failure is at least a magnitude greater for Al
alloys (22-25% vs. 1.5%).
3. Inspection for non-duty damage (e.g. dents in the tube) is much more
critical for CFCs than metal alloys - this is because CFC properties are
much more significantly reduced due to their low tolerance for low impact
low velocity damage. All the research and literature on CFCs have been
stating this for decades.
4. Detection of non-duty damage to CFCs is much more difficult than for
metals - this is because it's quite likely for CFCs to sustain sub-surface
damage due to impact (resulting in adverse effects to properties) without
visible clues. Again, experience in the aerospace industry has shown this.
> when i clamp a beer-can-thin aluminum frame and dent the tube, that's ok,
> but clamping a carbon tube might not be - just in case it's cracked but we
> really don't know???
Exactly. When you've seen the dent in the "beer-can-thin" Al frame, you
will hopefully know better than to take it for a marathon mountain bike ride
(depending on where the dent is). You know it's been damaged. When you've
applied a clamping force on a carbon tube and either knowingly or
unknowingly over-loaded it, you will likely not know if it has sustained
sub-surface damage. It doesn't even have to be a clamping force - it could
just be an unintentional bump with a bike rack, or a whack of a tree branch
on the trail.
>>
>> CFRPs do exhibit superior fatigue properties from metals, if designed
>> correctly. However, much work that's been done so far in the last few
>> decades address the fact that structural integrity of CFRPs are much
>> easier to compromise than metals due to impacts such as above; this is
>> what makes CFRPs easier to damage. There are whole industries spawned in
>> CFRP structural integrity because of CFRPs inherent low impact damage
>> tolerance to loads from different directions to intended.
>
> so don't load them other than as intended! and enjoy the superior fatigue
> resistance.
Hopefully then you will have cleared all the trails you ride on of all
possible objects that can cause unintended loads on CFCs, such as stones,
rocks, tree branches, debris... and you will have also put a thick foam
around your CFC components to prevent any dings and impacts from handling
the bike during storage, transport, and any other unintended circumstances.
There is a cost to using CFC and its high fatigue resistance and high
strength to weight ratio, and that is eternal vigilance for damage. The
aircraft industry can tell you all about this.
>> Non-Destructive Inspection is what maintainers do with composites.
>> Non-Destructive Testing is what manufacturers do prior to introducing
>> components into service. I am talking about structural integrity
>> monitoring and inspection of CFRPs.
>
> which is simply uneconomic for bikes, regardless of material.
Exactly. However, NDI is the only way to assess the structural integrity of
CFRPs, barring those damage that have visible clues (which happen less often
than those without visible clues).
>>> 1. the ndi/t industry for aerospace /started/ with the need to detect
>>> and prevent fatigue in /metals/.
>>
>> This is unrelated to the fact that CFRPs require much more rigorous
>> inspections than metals;
>
> no it's not. you're bleating about cfrp as if it's flawed, yet you're
> glossing over the need to extensively check and test metals. /and/ not
> addressing the degree to which metals have much inferior fatigue and thus
> greater /need/ for inspection.
CFRP is flawed - there is a price to pay for its properties, and that is,
it's much more susceptible to low impact low velocity damage. It's terrific
for industries that can afford it, and most importantly, for those
industries that have the appropriate resources devoted to its structural
integrity assessment. This is why there are whole industries devoted
specifically to CFRP inspection and testing. The material has some critical
flaws, but some of its properties are so good that there are (and they're
worth having) huge research programs to characterize and address damage
tolerance of carbon composites.
You also need to be aware that Al alloys have calculable lives - aircraft ND
inspections are scheduled on the basis of the knowledge of how much of the
Al alloys' lives have been expended due to cyclic loads. With CFRPs, there
is no such thing as fatigue life, and therefore structural integrity and
damage monitoring are scheduled regularly, and more rigorously using more
intensive techniques than metal NDIs because damage can exist without
visible clues, and the consequences are much more catastrophic.
>> in fact, NDI techniques for CFRPs are quite different than those for
>> metals.
>
> indeed, but that's not the point.
It is. NDI for CFRPs are technologically more advanced than for metals - in
fact, research is still ongoing for better, more reliable indicators of CFRP
integrity (microwaves, thermographics, optical fibers). As in this
presentation, traditional NDI for example, will not detect weak bondlines
(http://64.233.167.104/search?q=cache:1S0nLgElcgwJ:https://www.niar.wichita.edu/NIARWorkshops/LinkClick.aspx%3Ffileticket%3DMXHrsvjn%252Fjc%253D%26tabid%3D104%26mid%3D579+ndi+for+CFRP&hl=en&ct=clnk&cd=9&gl=us).
This tells us that all this effort is required for CFRPs because of its low
damage tolerance and inherent difficulty in assessing/detecting damage..
>> Carbon fiber forks have been in service for much shorter, in much less
>> numbers than metal forks. Jury is still out on this.
>
> how much longer does the jury have to be out?
As long as the use of Al alloys and steel on bike frames.
>>> over a decade of of use, millions of rider miles,
>>
>> "Millions of rider miles" is speculative.
>
> yes, it's an under estimate. i personally have over 10k on a carbon fork.
> find another 100 riders like me, that's 1M rider miles. now, /how/ many
> people ride such a bike?
Good question. How many riders have put in 10k miles on their carbon fork?
In fact, seeing as most bikes on offer in markets around the world have
metal forks, how many riders use carbon forks?
>> If we had a database that's easily accessible by the public, of carbon
>> fork failures, then that statement might be more confidence inspiring.
>> On the other hand, failures of other carbon bike components such as
>> handlebars and seatposts have many testimonials - do a search on
>> mtbr.com.
>
> in theory, i'd agree, but since this is r.b.t., and the proles here don't
> hesitate to bleat about /any/ imaginary problem they think they find -
> disk brakes on mtb's for example - i think we'd have heard before now if
> there was much to complain about.
Like I said, go over to mtbr.com and see for yourself the testimonials (some
with pictures) of failures of carbon components on bikes.
Michael Press
<iMudnYLtfqUODk7b...@speakeasy.net>,
jim beam <spamv...@bad.example.net> wrote:
I use a torque wrench when tightening a stem
onto my steel steering-tubes.
--
Michael Press
Michael Press
<timmcn-371E1B....@news.iphouse.com>,
Tim McNamara <tim...@bitstream.net> wrote:
And the non-critical parts are ...
Rack?
--
Michael Press
J. Clarke
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>> Peter Cole wrote:
>>>
>>>>> From:
>>>>> <http://www.exponent.com/about/docs/ISASI2006_paper.pdf>
>>>
>>>> that is a marketing piece designed to fear-monger their way into
>>>> getting more consulting business!!! "omg, the service tech
>>>> /sneezed/ when torquing that bolt - you need our special torque
>>>> analysis consulting services".
>>>>
>>>> jeeze, trying to use that as authority on material properties is
>>>> just ridiculous. but you're a prick, so we'd expect stuff like
>>>> that from you.
>>>
>>> You're missing the point, which was that CF impact damage often
>>> isn't obvious, nor easily detected without special equipment.
>>
>> so how many aluminum cranks fatigue and break without the rider
>> being
>> aware? frames? handlebars?
>
> Why don't you just address the point of the article -- namely that
> CF
> composite is impossible to inspect without special equipment?
For a quick test on CF, all you need is a quarter. Tap it with the
edge of the quarter and listen to the sound. If it's sharp then you
probably don't have a problem, if it's dull then you probably have a
delam. This is about as effective and reliable as a visual
non-penetrant inspection for cracks in metal and is pretty much the
method that is used in the aircraft industry for inspection during
production and rework of composite parts. You can find specially made
hammers but a quarter works fine for a quick check.
> Metal components crack, but at least you have a chance of inspecting
> for cracks.
--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
Jambo
"J. Clarke" <jclarke...@cox.net> wrote in message
news:fb245...@news2.newsguy.com...
> For a quick test on CF, all you need is a quarter. Tap it with the
> edge of the quarter and listen to the sound. If it's sharp then you
> probably don't have a problem, if it's dull then you probably have a
> delam. This is about as effective and reliable as a visual
> non-penetrant inspection for cracks in metal
I've never heard nor seen this method adopted by any company, workshop,
airline, and military. You can be sure that any technician using this
method will not be in that job for very long. You'd best hope that the next
plane you fly with composite structural components haven't been checked by
someone using your quarter tap method.
> and is pretty much the
> method that is used in the aircraft industry for inspection during
> production and rework of composite parts.
Can you reference this process in any manual or procedure by any aircraft
company?
Tim McNamara
Michael Press <rub...@pacbell.net> wrote:
Water bottle cage? ;-)
By "critical" parts I mean the ones that can get you killed or hurt if
they fail castrophically: frame, fork, stem, handlebars, seatpost and
cranks in particular. Well, and wheels too- but IMHO carbon fiber rims
are about as smart as a box of rocks. But CF derailleur plates and such
might be OK.
Tom "Johnny Sunset" Sherman
> In article <rubrum-16C708....@newsclstr02.news.prodigy.com>,
> Michael Press <rub...@pacbell.net> wrote:
>> And the non-critical parts are ...
>>
>> Rack?
>
> Water bottle cage? ;-)
>
> By "critical" parts I mean the ones that can get you killed or hurt if
> they fail castrophically: frame, fork, stem, handlebars, seatpost and
> cranks in particular. Well, and wheels too- but IMHO carbon fiber rims
> are about as smart as a box of rocks. But CF derailleur plates and such
> might be OK.
A CFRP derailer [1] plate would be silly, since it would be easily
abraded by the chain.
[1] Brownian spelling.
--
Tom Sherman - Holstein-Friesland Bovinia
A Real Cyclist [TM] keeps at least one bicycle in the bedroom.
J. Clarke
> "J. Clarke" <jclarke...@cox.net> wrote in message
> news:fb245...@news2.newsguy.com...
>> For a quick test on CF, all you need is a quarter. Tap it with the
>> edge of the quarter and listen to the sound. If it's sharp then
>> you
>> probably don't have a problem, if it's dull then you probably have
>> a
>> delam. This is about as effective and reliable as a visual
>> non-penetrant inspection for cracks in metal
>
> I've never heard nor seen this method adopted by any company,
> workshop, airline, and military.
So? Have you comported your life in such a manner that you would
expect to see composite aircraft structures being nondestructively
tested?
> You can be sure that any technician
> using this method will not be in that job for very long.
Then I guess you better fire the inspectors at Airbus.
> You'd best
> hope that the next plane you fly with composite structural
> components
> haven't been checked by someone using your quarter tap method.
Why would one want to fly in an airplane that had not been properly
inspected?
>> and is pretty much the
>> method that is used in the aircraft industry for inspection during
>> production and rework of composite parts.
>
> Can you reference this process in any manual or procedure by any
> aircraft company?
Here's one from 2006 from the NTSB.
http://www.ntsb.gov/Recs/letters/2006/A06_27_28.pdf
One from Aircraft Maintenance Technology
http://www.amtonline.com/publication/article.jsp?pubId=1&id=2521
One from Boeing presented at Texas A&M (scroll down to near the end)
http://otrc.tamu.edu/Pages/Established%20NDE%20Technology.pdf.
Here's an expensive tool from Mitsui that automates the process.
http://www.wp632.com/
If you google "composite tap test" you'll find many other descriptions
of the process, patents for devices based on it, papers concerning its
application, etc.
It's a very well known process in the industry, it was taught to me in
1979 when I was first hired as an engineer at United Technologies
Hamilton Standard and I've seen it used by engineers and technicians
from Lockheed, Boeing, DeHavilland, Bell, the Navy, and the Air Force
that I can remember. I don't have the numbers for the manual but
you'll find it described either directly or by reference in the
overhaul manual for the Hamilton Standard 54460 and 24PF propeller
blades, spinners, and afterbodies, and in the overhaul manual for the
54H60 spinner and afterbody. It's also described in Burt Rutan's
plans for the VarieEze and LongEze aircraft.
Jambo
> Jambo wrote:
>> "J. Clarke" <jclarke...@cox.net> wrote in message
>> news:fb245...@news2.newsguy.com...
>>> For a quick test on CF, all you need is a quarter. Tap it with the
>>> edge of the quarter and listen to the sound. If it's sharp then
>>> you
>>> probably don't have a problem, if it's dull then you probably have
>>> a
>>> delam. This is about as effective and reliable as a visual
>>> non-penetrant inspection for cracks in metal
>>
>> I've never heard nor seen this method adopted by any company,
>> workshop, airline, and military.
> So? Have you comported your life in such a manner that you would
> expect to see composite aircraft structures being nondestructively
> tested?
Yes.
>> You can be sure that any technician
>> using this method will not be in that job for very long.
>
> Then I guess you better fire the inspectors at Airbus.
And any other airline and aircraft manufacturer that rely on this method for
NDI of their structural composite components. It's akin to kicking tires on
a car you're inspecting before buying.
>> You'd best
>> hope that the next plane you fly with composite structural
>> components
>> haven't been checked by someone using your quarter tap method.
>
> Why would one want to fly in an airplane that had not been properly
> inspected?
I'm glad you agree that quarter tapping isn't proper inspection.
>>> and is pretty much the
>>> method that is used in the aircraft industry for inspection during
>>> production and rework of composite parts.
>>
>> Can you reference this process in any manual or procedure by any
>> aircraft company?
>
> Here's one from 2006 from the NTSB.
> http://www.ntsb.gov/Recs/letters/2006/A06_27_28.pdf
Sure. The article refers to rudder skin damage, not a critical part. It
also notes that further inspection was required to determine the nature of
the damage. However, this method can't detect fiber breakages with no
delamination. Note that the recommendation did not include using tap
testing as the method for inspection.
> One from Aircraft Maintenance Technology
> http://www.amtonline.com/publication/article.jsp?pubId=1&id=2521
Which also implies that tap tests alone can't classify types of damage, and
further inspection is required.
> One from Boeing presented at Texas A&M (scroll down to near the end)
> http://otrc.tamu.edu/Pages/Established%20NDE%20Technology.pdf.
Which also states that this method is unreliable and subjective (relies on
people's hearing).
> Here's an expensive tool from Mitsui that automates the process.
> http://www.wp632.com/
>
> If you google "composite tap test" you'll find many other descriptions
> of the process, patents for devices based on it, papers concerning its
> application, etc.
As well as limitations of the technique.
> It's a very well known process in the industry, it was taught to me in
> 1979 when I was first hired as an engineer at United Technologies
> Hamilton Standard and I've seen it used by engineers and technicians
> from Lockheed, Boeing, DeHavilland, Bell, the Navy, and the Air Force
> that I can remember. I don't have the numbers for the manual but
> you'll find it described either directly or by reference in the
> overhaul manual for the Hamilton Standard 54460 and 24PF propeller
> blades, spinners, and afterbodies, and in the overhaul manual for the
> 54H60 spinner and afterbody. It's also described in Burt Rutan's
> plans for the VarieEze and LongEze aircraft.
What you're not mentiong is that this technique is not used to assess
damage, but merely to indicate potential of damage. When you also include
the fact that the subjective hearing test included in this technique
eliminates all possibilty of consistency across different technicians, you
will not find in any manuals the recommendation to use this technique for
aircraft critical structural parts.
So I guess your original statement is true, that it's a quick indicator of
damage, but it needs a caveat: the technique isn't reliable.
jim beam
i'm well aware of technique - you misunderstand what i mean. just
because something is carbon, doesn't mean it's suddenly got to withstand
different use parameters - which is essentially the red herring being
swallowed around here. a 100kg overload for steel doesn't mean that
carbon somehow experiences a 300kg overload. if [reynolds] forks are
anything to go by, a typical yield limit on quality carbon bike
componentry is ~3x that of steel the steel counterpart. but the load is
the same. that's a 3x safety margin on application!!!
>
>> when i clamp a beer-can-thin aluminum frame and dent the tube, that's ok,
>> but clamping a carbon tube might not be - just in case it's cracked but we
>> really don't know???
>
> Exactly. When you've seen the dent in the "beer-can-thin" Al frame, you
> will hopefully know better than to take it for a marathon mountain bike ride
> (depending on where the dent is). You know it's been damaged. When you've
> applied a clamping force on a carbon tube and either knowingly or
> unknowingly over-loaded it, you will likely not know if it has sustained
> sub-surface damage. It doesn't even have to be a clamping force - it could
> just be an unintentional bump with a bike rack, or a whack of a tree branch
> on the trail.
now that's just fud. if it takes 3x the load to cause damage...
>
>>> CFRPs do exhibit superior fatigue properties from metals, if designed
>>> correctly. However, much work that's been done so far in the last few
>>> decades address the fact that structural integrity of CFRPs are much
>>> easier to compromise than metals due to impacts such as above; this is
>>> what makes CFRPs easier to damage. There are whole industries spawned in
>>> CFRP structural integrity because of CFRPs inherent low impact damage
>>> tolerance to loads from different directions to intended.
>> so don't load them other than as intended! and enjoy the superior fatigue
>> resistance.
>
> Hopefully then you will have cleared all the trails you ride on of all
> possible objects that can cause unintended loads on CFCs, such as stones,
> rocks, tree branches, debris... and you will have also put a thick foam
> around your CFC components to prevent any dings and impacts from handling
> the bike during storage, transport, and any other unintended circumstances.
fud fud fud. millions upon millions of real life rider miles say this
is fud.
>
> There is a cost to using CFC and its high fatigue resistance and high
> strength to weight ratio, and that is eternal vigilance for damage. The
> aircraft industry can tell you all about this.
and the aerospace industry can tell me all about fatigue in metals too!!!
>
>>> Non-Destructive Inspection is what maintainers do with composites.
>>> Non-Destructive Testing is what manufacturers do prior to introducing
>>> components into service. I am talking about structural integrity
>>> monitoring and inspection of CFRPs.
>> which is simply uneconomic for bikes, regardless of material.
>
> Exactly. However, NDI is the only way to assess the structural integrity of
> CFRPs, barring those damage that have visible clues (which happen less often
> than those without visible clues).
so what about the non-visual breaks that occur in metals???
>
>>>> 1. the ndi/t industry for aerospace /started/ with the need to detect
>>>> and prevent fatigue in /metals/.
>>> This is unrelated to the fact that CFRPs require much more rigorous
>>> inspections than metals;
>> no it's not. you're bleating about cfrp as if it's flawed, yet you're
>> glossing over the need to extensively check and test metals. /and/ not
>> addressing the degree to which metals have much inferior fatigue and thus
>> greater /need/ for inspection.
>
> CFRP is flawed
here we go...
> - there is a price to pay for its properties, and that is,
> it's much more susceptible to low impact low velocity damage. It's terrific
> for industries that can afford it, and most importantly, for those
> industries that have the appropriate resources devoted to its structural
> integrity assessment. This is why there are whole industries devoted
> specifically to CFRP inspection and testing.
and those same industries extend their skills to metals. it's a total
logical disconnect to contend that testing is essential, because it's
used in aerospace, but metal bikes are exempt because, um, well, it's
not aerospace, so...
> The material has some critical
> flaws, but some of its properties are so good that there are (and they're
> worth having) huge research programs to characterize and address damage
> tolerance of carbon composites.
fudge...
>
> You also need to be aware that Al alloys have calculable lives - aircraft ND
> inspections are scheduled on the basis of the knowledge of how much of the
> Al alloys' lives have been expended due to cyclic loads.
indeed. time to FAILURE.
> With CFRPs, there
> is no such thing as fatigue life, and therefore structural integrity and
> damage monitoring are scheduled regularly, and more rigorously using more
> intensive techniques than metal NDIs because damage can exist without
> visible clues, and the consequences are much more catastrophic.
eh? you're saying that fatigue is ok because we know it's going to
fail, but cfrp is not because it doesn't??? that's stupid. inaccurate
and stupid. cfrp /does/ fatigue. but its fatigue life is much superior.
>
>>> in fact, NDI techniques for CFRPs are quite different than those for
>>> metals.
>> indeed, but that's not the point.
>
> It is. NDI for CFRPs are technologically more advanced than for metals - in
> fact, research is still ongoing for better, more reliable indicators of CFRP
> integrity (microwaves, thermographics, optical fibers). As in this
> presentation, traditional NDI for example, will not detect weak bondlines
> (http://64.233.167.104/search?q=cache:1S0nLgElcgwJ:https://www.niar.wichita.edu/NIARWorkshops/LinkClick.aspx%3Ffileticket%3DMXHrsvjn%252Fjc%253D%26tabid%3D104%26mid%3D579+ndi+for+CFRP&hl=en&ct=clnk&cd=9&gl=us).
> This tells us that all this effort is required for CFRPs because of its low
> damage tolerance and inherent difficulty in assessing/detecting damage..
testing is essential in /all/ aerospace applications, and techniques
/are/ indeed different for different materials. BUT BUT BUT, different
testing technique is /not/ evidence of greater risk!!! and "damage" to
cfrp is inflicted at much higher levels than for metals!!!
>
>>> Carbon fiber forks have been in service for much shorter, in much less
>>> numbers than metal forks. Jury is still out on this.
>> how much longer does the jury have to be out?
>
> As long as the use of Al alloys and steel on bike frames.
bull.
>
>
>>>> over a decade of of use, millions of rider miles,
>>> "Millions of rider miles" is speculative.
>> yes, it's an under estimate. i personally have over 10k on a carbon fork.
>> find another 100 riders like me, that's 1M rider miles. now, /how/ many
>> people ride such a bike?
>
> Good question. How many riders have put in 10k miles on their carbon fork?
millions. they've been on the market for over 10 years. and carbon, as
you've admitted yourself, has much superior fatigue characteristics.
> In fact, seeing as most bikes on offer in markets around the world have
> metal forks, how many riders use carbon forks?
in the sub $50 category. most bikes ~$500 up uses carbon these days.
www.performancebike.com
>
>>> If we had a database that's easily accessible by the public, of carbon
>>> fork failures, then that statement might be more confidence inspiring.
>>> On the other hand, failures of other carbon bike components such as
>>> handlebars and seatposts have many testimonials - do a search on
>>> mtbr.com.
>> in theory, i'd agree, but since this is r.b.t., and the proles here don't
>> hesitate to bleat about /any/ imaginary problem they think they find -
>> disk brakes on mtb's for example - i think we'd have heard before now if
>> there was much to complain about.
>
> Like I said, go over to mtbr.com and see for yourself the testimonials (some
> with pictures) of failures of carbon components on bikes.
there are two issues here.
1. you can find testimonials saying /anything/ on mtbr. look for phil
hubs and some clown has written about how they stink. and i have been
approached by a vendor to post mtbr endorsement of their products. can
you get a few people you know together to do the same? conclusion, you
can take that with a pinch of salt.
2. because some cheap-ass chinese factory is skimping on the material
quality and fakes testing certs for shipped product, doesn't mean that
cfrp as a material is inherently flawed. manufacturers screw up.
designers screw up. but that simply means they got it wrong. just like
the metal casting with voids and forging that's too thin, or spoke elbow
that's scratched up. i have personal experience of cfrp failure with a
kestrel fork - there was a bad batch when they first off-shored. but i
still ride carbon forks.
jim beam
1. you're /not/ going to pay to have a bike inspected to the same
standards as aerospace.
2. practical reality indicates that provided decent manufacturing
standards are used and product is not abused, this stuff works just fine.
jim beam
you must be a newbie. the r.b.t. m.o. is to all stand about in a circle
competing to be the biggest naysayer and doomsdayer on any technology
not at least 50 years old. shit, we still have people bleating about
bushingless chains!!!
jim beam
so you're deceived by fud? what a retard!
J. Clarke
Fine, you're right and all the major players in the aerospace industry
are wrong.
Peter Cole
I'm not sure this does much to prove your point. First, it was a large
honeycomb panel, delaminated by contamination from hydraulic fluid
(another composite weakness). Most importantly (to your argument):
"Further, it was determined that tap tests on the external surfaces of
the rudder likely would not have disclosed the disbonding of an internal
surface."
> One from Aircraft Maintenance Technology
> http://www.amtonline.com/publication/article.jsp?pubId=1&id=2521
"Familiarize yourself with the structure you are inspecting. A change in
the sound does not necessarily indicate a defect. For example, if
tapping different areas of the wing, you would get a slightly different
sound for areas that are sandwiched laminate, non-sandwiched laminate,
and transition areas between the two. Corrie Volinkaty, a technical
instructor for Cirrus, shares, "You will get slightly different sounds
as you transition between different areas of the aircraft depending on
the structure. The thing to remember is that a delamination will not be
just a different sound, it will be a dull sound or a thud. Knowing the
structure beneath is very helpful when performing tap tests."
Doesn't sound too practical for typical bike parts, perhaps it works OK
for large panels.
> One from Boeing presented at Texas A&M (scroll down to near the end)
> http://otrc.tamu.edu/Pages/Established%20NDE%20Technology.pdf.
"Disadvantages
• Somewhat unreliable
• Limited to defects 3 to 4
plies deep
• Limited to defects larger
than 1 inch diameter
• Results affected by
environmental noise
• Results affected by hearing
ability of inspector"
Again, doesn't sound too practical for inspecting bike parts.
> Here's an expensive tool from Mitsui that automates the process.
> http://www.wp632.com/
Not something likely to be found at the bike shop or home workshop.
> If you google "composite tap test" you'll find many other descriptions
> of the process, patents for devices based on it, papers concerning its
> application, etc.
It seems to have severe limitations even for part types and geometries
that are most favorable for it. It doesn't seem to be very helpful for
bike components.
Peter Cole
Cites, please.
>
>
>>
>>> when i clamp a beer-can-thin aluminum frame and dent the tube, that's
>>> ok, but clamping a carbon tube might not be - just in case it's
>>> cracked but we really don't know???
>>
>> Exactly. When you've seen the dent in the "beer-can-thin" Al frame,
>> you will hopefully know better than to take it for a marathon mountain
>> bike ride (depending on where the dent is). You know it's been
>> damaged. When you've applied a clamping force on a carbon tube and
>> either knowingly or unknowingly over-loaded it, you will likely not
>> know if it has sustained sub-surface damage. It doesn't even have to
>> be a clamping force - it could just be an unintentional bump with a
>> bike rack, or a whack of a tree branch on the trail.
>
> now that's just fud. if it takes 3x the load to cause damage...
Cites, please.
>
>
>>
>>>> CFRPs do exhibit superior fatigue properties from metals, if
>>>> designed correctly. However, much work that's been done so far in
>>>> the last few decades address the fact that structural integrity of
>>>> CFRPs are much easier to compromise than metals due to impacts such
>>>> as above; this is what makes CFRPs easier to damage. There are
>>>> whole industries spawned in CFRP structural integrity because of
>>>> CFRPs inherent low impact damage tolerance to loads from different
>>>> directions to intended.
>>> so don't load them other than as intended! and enjoy the superior
>>> fatigue resistance.
>>
>> Hopefully then you will have cleared all the trails you ride on of all
>> possible objects that can cause unintended loads on CFCs, such as
>> stones, rocks, tree branches, debris... and you will have also put a
>> thick foam around your CFC components to prevent any dings and impacts
>> from handling the bike during storage, transport, and any other
>> unintended circumstances.
>
> fud fud fud. millions upon millions of real life rider miles say this
> is fud.
Cites, please.
>
>
>>
>> There is a cost to using CFC and its high fatigue resistance and high
>> strength to weight ratio, and that is eternal vigilance for damage.
>> The aircraft industry can tell you all about this.
>
> and the aerospace industry can tell me all about fatigue in metals too!!!
So what?
>
>
>>
>>>> Non-Destructive Inspection is what maintainers do with composites.
>>>> Non-Destructive Testing is what manufacturers do prior to
>>>> introducing components into service. I am talking about structural
>>>> integrity monitoring and inspection of CFRPs.
>>> which is simply uneconomic for bikes, regardless of material.
>>
>> Exactly. However, NDI is the only way to assess the structural
>> integrity of CFRPs, barring those damage that have visible clues
>> (which happen less often than those without visible clues).
>
> so what about the non-visual breaks that occur in metals???
Examples?
>
>
>>
>>>>> 1. the ndi/t industry for aerospace /started/ with the need to
>>>>> detect and prevent fatigue in /metals/.
>>>> This is unrelated to the fact that CFRPs require much more rigorous
>>>> inspections than metals;
>>> no it's not. you're bleating about cfrp as if it's flawed, yet
>>> you're glossing over the need to extensively check and test metals.
>>> /and/ not addressing the degree to which metals have much inferior
>>> fatigue and thus greater /need/ for inspection.
>>
>> CFRP is flawed
>
> here we go...
>
>
>> - there is a price to pay for its properties, and that is, it's much
>> more susceptible to low impact low velocity damage. It's terrific for
>> industries that can afford it, and most importantly, for those
>> industries that have the appropriate resources devoted to its
>> structural integrity assessment. This is why there are whole
>> industries devoted specifically to CFRP inspection and testing.
>
> and those same industries extend their skills to metals. it's a total
> logical disconnect to contend that testing is essential, because it's
> used in aerospace, but metal bikes are exempt because, um, well, it's
> not aerospace, so...
It's because of the failure mode differences between the materials.
>
>
>> The material has some critical flaws, but some of its properties are
>> so good that there are (and they're worth having) huge research
>> programs to characterize and address damage tolerance of carbon
>> composites.
>
> fudge...
>
>
>>
>> You also need to be aware that Al alloys have calculable lives -
>> aircraft ND inspections are scheduled on the basis of the knowledge of
>> how much of the Al alloys' lives have been expended due to cyclic loads.
>
> indeed. time to FAILURE.
>
>
>> With CFRPs, there is no such thing as fatigue life, and therefore
>> structural integrity and damage monitoring are scheduled regularly,
>> and more rigorously using more intensive techniques than metal NDIs
>> because damage can exist without visible clues, and the consequences
>> are much more catastrophic.
>
> eh? you're saying that fatigue is ok because we know it's going to
> fail, but cfrp is not because it doesn't??? that's stupid. inaccurate
> and stupid. cfrp /does/ fatigue. but its fatigue life is much superior.
But less predictable, because it's generally the result of damage.
Aluminum fatigues with cracking, and crack growth rates have been
extensively researched and form the justification for maintenance schedules.
>
>>
>>>> in fact, NDI techniques for CFRPs are quite different than those for
>>>> metals.
>>> indeed, but that's not the point.
>>
>> It is. NDI for CFRPs are technologically more advanced than for
>> metals - in fact, research is still ongoing for better, more reliable
>> indicators of CFRP integrity (microwaves, thermographics, optical
>> fibers). As in this presentation, traditional NDI for example, will
>> not detect weak bondlines
>> (http://64.233.167.104/search?q=cache:1S0nLgElcgwJ:https://www.niar.wichita.edu/NIARWorkshops/LinkClick.aspx%3Ffileticket%3DMXHrsvjn%252Fjc%253D%26tabid%3D104%26mid%3D579+ndi+for+CFRP&hl=en&ct=clnk&cd=9&gl=us).
>> This tells us that all this effort is required for CFRPs because of
>> its low damage tolerance and inherent difficulty in
>> assessing/detecting damage..
>
> testing is essential in /all/ aerospace applications, and techniques
> /are/ indeed different for different materials. BUT BUT BUT, different
> testing technique is /not/ evidence of greater risk!!! and "damage" to
> cfrp is inflicted at much higher levels than for metals!!!
Not sure what kind of "damage" you're referring to. Fatigue
accumulation, yes, impact, no, corrosion, yes, solvents, no. As for
overloading, you'll have to provide support for your claim that (bike
component) CFRP has higher safety margins.
>>>> Carbon fiber forks have been in service for much shorter, in much
>>>> less numbers than metal forks. Jury is still out on this.
>>> how much longer does the jury have to be out?
>>
>> As long as the use of Al alloys and steel on bike frames.
>
> bull.
The technology of CF forks has evolved considerably since introduction.
The characteristics of forks makes it one of the most attractive places
to exploit CF weight savings. It also makes it one of the most
reliability sensitive.
Your alternative?
>
> 2. because some cheap-ass chinese factory is skimping on the material
> quality and fakes testing certs for shipped product, doesn't mean that
> cfrp as a material is inherently flawed. manufacturers screw up.
> designers screw up. but that simply means they got it wrong. just like
> the metal casting with voids and forging that's too thin, or spoke elbow
> that's scratched up. i have personal experience of cfrp failure with a
> kestrel fork - there was a bad batch when they first off-shored. but i
> still ride carbon forks.
CF materials are expensive and the process is labor intensive -- that's
not likely to change soon. The temptation to cut corners will remain.
But that's beside the point. If your contention is that CF part failures
are due to bad process and user abuse rather than intrinsic qualities,
it's on you to back that up. This industry is full of blame the user
history. Even if 100% of fork failures were from crappy quality, and
100% of bar and post failures were from users over-clamping -- how is
that going to change? If CF parts become much more common do you think
these kinds of incidents will diminish?