"CF Bike Shatters" - continued

Ryan Cousineau wrote:

Chalo wrote:

Ryan Cousineau wrote:

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.

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

jim beam wrote:
Peter Cole wrote:
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,
bull****ter.

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.


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
****ing 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.

bull****.

1. who the **** 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 BULL**** 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? bull****. carbon componentry has
labels saying "do not clamp", "do not exceed...", etc., that can be
ignored? bull****.

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.

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!


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.

jim beam wrote:
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)

jim beam wrote:

but the point is, wood's not brittle. and metal can be.

But CF always is!

jim beam wrote:

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?

In article ,
Peter Cole wrote:

jim beam wrote:
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)

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.

In article ,
Peter Cole wrote:

jim beam wrote:

but the point is, wood's not brittle. and metal can be.

But CF always is!

Whether wood is brittle depends on the species of wood and its
condition.

Peter Cole wrote:
jim beam wrote:
Peter Cole wrote:
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,
bull****ter.

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.


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.










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 bull****ting 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 bull****s 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 bull****?









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. bull**** 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 ****ing 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?

**** 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.

bull****.


Given that they're all proprietary,

bull****! 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.

bull****.

1. who the **** 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 BULL**** 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 bull****ting.






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? bull****. carbon componentry has
labels saying "do not clamp", "do not exceed...", etc., that can be
ignored? bull****.

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 bull****. you're a complete prick.

Peter Cole wrote:
jim beam wrote:
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)

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.