"CF Bike Shatters" - continued

jim beam wrote:
Peter Cole wrote:
jim beam wrote:
Tim McNamara wrote:
In article , "Jambo"
[email protected] wrote:

"jim beam" wrote in message
...
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.

from over-zealous stem clamping, not from road force.

Burden of proof is on you.

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.

What % of failed steerer tubes show this? Cites, please.

jim beam wrote:
Peter Cole wrote:
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 bull****. 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?

Cites, please.







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?

"Main Entry: 1prick
Pronunciation: 'prik
Function: noun
Etymology: Middle English prikke, from Old English prica; akin to Middle
Dutch pric prick
1 : a mark or shallow hole made by a pointed instrument
2 a : a pointed instrument or weapon b : a sharp projecting organ or part
3 : an instance of pricking or the sensation of being pricked : as a : a
nagging or sharp feeling of remorse, regret, or sorrow b : a slight
sharply localized discomfort the prick of a needle
4 usually vulgar : PENIS
5 usually vulgar : a spiteful or contemptible man often having some
authority"

"SPITE implies petty feelings of envy and resentment that are often
expressed in small harassments"

"CONTEMPTIBLE may imply any quality provoking scorn or a low standing in
any scale of values"

An ambiguous term. Unless you're being intentionally vulgar, I'm
guessing it's #3 -- it's your ego being pricked.

If it's #4, maybe it's a Freudian thing.

If it's #5, it's not spite -- I can honestly say I don't envy you. As to
"harassments", hmmmm... check the archives.

If it's "scorn", you seem to have a lot of that, and I'm really
flattered by my company. You seem to hold all engineers in contempt,
particularly good ones.

Calling someone a "prick" over and over seems an oxymoronic (prickish)
behavior if sincere, otherwise, just moronic.

Peter Cole wrote:
jim beam wrote:
Peter Cole wrote:
jim beam wrote:
Peter Cole wrote:
jim beam wrote:
Peter Cole wrote:
jim beam wrote:

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.

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.

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.

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_compos ites


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.


ah, the peter cole approach: "keep trying to baffle them with bull".

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.

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.

What would you like to add to the description in the Wikipedia cite?

You have repeatedly insinuated that high strength materials cannot be
brittle. That is wrong. Stop tap dancing and state your point -- if you
can.






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.

I am not doing that. You seem to not get the reality that an anisotropic
material can't be described for qualities like brittleness without
qualifying direction. Uniaxial CFRP is brittle in the fiber axis but not
orthogonal. In one mode you see the characteristics of the fiber
(brittle) in the other, the matrix (not brittle). To get strong/stiff
composite parts you have to construct in such a way that the fiber
characteristics dominate. By necessity that gives you parts that are as
brittle as the underlying fiber. Ergo, low impact tolerance.

If what you claim is true, you should be able to provide citations. Your
failure to do so speaks volumes, despite your evasions.

wow. you're still massively confused. but rather than pick through a
stale old thread, let's start again...

Jambo wrote:
"jim beam" wrote in message
...
wow. you're still massively confused. but rather than pick through a
stale old thread, let's start again...

You can start again as many times as you like, you're still going to be
wrong.

really?


Why not just take your own advice, learn from the data you've been
shown, and move on?

so when are /you/ going to learn?


You must think you have a reputation to save here on
rbt. Let me assure you that you don't.

so the **** what? i'm not selling anything so who the **** cares?

but at the same time, /i'm/ not being a jackass by ridiculously ignoring
industry standard testing in aerospace, while trying to insist on
aerospace for bike apps as a way to try fudging the facts.