Re: Carbon Forks Reliability = paranoia or truth?

Carl Sundquist wrote:
jim beam wrote:
Carl Sundquist wrote:
jim beam wrote:
drew046@xxxxxxxxx wrote:
On Feb 17, 3:50�pm, Mike <nos...@xxxxxxxxxx> wrote:
On Sun, 15 Feb 2009 09:06:59 -0800 (PST), bfd <bfd...@xxxxxxxxx>
wrote:

I don't know. Back in 1997, I bought a USED carbon fiber bike (Calfee
with Kestrel fork) and have ridden it about 2K miles a year for the
last 11 years. I had my LBS inspect the frameset when I bought it.
Yes, I regularly inspect my frameset for problems. I have no problem
descending 30+mph (routine go faster) and expect both will last years.
I did have the frameset inspected and a new clearcoat put on by the
mfr about 7 years ago.
Is Grant being paranoid or are there legions of carbon forks breaking
and causing death and destruction? �Thanks!
While it's a different field there are many instances of catastrophic
failure of CF suspension and wing parts in Formula 1 motor racing due
to reasons other than collision. �The design, build, testing, lifing
and inspection policies adopted by F1 exceed anything in the bike
world at least as far as the ordinary consumer is concerned.

I'm not convinced any customer or bike shop inspection regime would
detect defects and reduce the risk to what some would deem acceptable
levels, and while I'd trust CF monocoques and impact structures on the
race track at 150+mph and in many other applications I'd not ride a
bicycle on the road with a CF fork, but I also have to say I wouldn't
by choice ride a diamond frame made out of anything other than steel.

--

How well does dye or florescent penetrant testing work w/ carbon
fiber? I've had no experience w/ penetrant testing of cf. Does it
attack the clear coat or the carbon fiber? Is it so widely absorbed by
the cf that the resulting bleed out masks any true indications? Does
it stain the clear coat or cf to such an extent as to render the part
to be cosmetically undesirable? Is there some other reason that it
would be unsatisfactory for cf flaw detection? At a cost of only ~$30
for a kit, that would test dozens of forks, it is not expensive. It
certainly doesn't require any great skills to use, although, to do it
professionally for clients, the training & certification involves some
time and money. If penetrant testing is technically a viable option,
why isn't it being used extensively?



you've answered your own question - the reason it's not used is...

Shit. I was actually looking forward to your explanation.

Signed,
Disappointed

i'm disappointed that it's not obvious to you.

Well, it's not. And apparently not to the person who posed the question.

forgive me being, er, "confused" by what appeared to be a poor attempt at sarcasm. if you want a serious answer, why not just ask a non-expleted serious question?

anyway, no, dp is not considered effective on composites, thus, it's not used - hence "why isn't it being used" is therefore a self-answering question.



Are dye/UV penetrants not viable because there is a coating (paint, clearcoat, epoxy) over the CF

partly, yes.


or because the base structure is a woven fabric rather than a single homogenous structure, i.e a metal tube

no.

and don't get side-tracked by "woven structure" when considering cfrp - its irrelevant. "woven" is almost always primarily cosmetic on top of other layers that are better oriented for load.


or is there another reason?

regarding fatigue, metals almost always have cracking nucleate at a surface. such a crack is accessible to dye penetrant, and thus there is a very good chance of post-manufacture flaw detection.

composites however don't necessarily [or even, rarely] have cracking nucleate from an outer surface, thus there is little or no chance of reliable crack detection using this method. indeed, you can get false positives from minor flaws in surface layers which have no effect on structural integrity.
.

Relevant Pages

  • Re: Carbon Forks Reliability = paranoia or truth?
    ... I'm not convinced any customer or bike shop inspection regime would ... bicycle on the road with a CF fork, but I also have to say I wouldn't ... I've had no experience w/ penetrant testing of cf. Does it ... you've answered your own question - the reason it's not used is... ...
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  • Re: Carbon Forks Reliability = paranoia or truth?
    ... I had my LBS inspect the frameset when I bought it. ... bicycle on the road with a CF fork, but I also have to say I wouldn't ... I've had no experience w/ penetrant testing of cf. Does it ... you've answered your own question - the reason it's not used is... ...
    (rec.bicycles.tech)
  • Re: Carbon Forks Reliability = paranoia or truth?
    ... I'm not convinced any customer or bike shop inspection regime would ... bicycle on the road with a CF fork, but I also have to say I wouldn't ... I've had no experience w/ penetrant testing of cf. Does it ... you've answered your own question - the reason it's not used is... ...
    (rec.bicycles.tech)
  • Re: Carbon Forks Reliability = paranoia or truth?
    ... I'm not convinced any customer or bike shop inspection regime would ... bicycle on the road with a CF fork, but I also have to say I wouldn't ... I've had no experience w/ penetrant testing of cf. Does it ... you've answered your own question - the reason it's not used is... ...
    (rec.bicycles.tech)