's Forum Archives - General

Archive Home >> General(1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 )

What are the characteristics of carbon fiber failing?(19 posts)

What are the characteristics of carbon fiber failing?Terry_Swisher_PMF
Aug 7, 2003 5:57 AM
my experienceDougSloan
Aug 7, 2003 6:05 AM
I had the first run of the 2000 Bianchi EV2 all carbon fork (under 300 grams) fail just above the upper headset area. It got soft, then sort of shredded. It actully stayed intact enough to get me the few blocks home from where it failed. It failed right as I yanked on the bars to cross an intersection.

Any pictures of this? TIA. (nm)orange_julius
Aug 7, 2003 6:08 AM
nope; sorry nmDougSloan
Aug 7, 2003 6:19 AM
my experienceTerry_Swisher_PMF
Aug 7, 2003 6:19 AM
What causes them to go soft? Did you have any other issues with that frame and fork?
Aug 7, 2003 6:35 AM
No other issues. The replacement has lasted 3 years now. I have no idea what caused it, but speculation was the way the Cinelli Grammo stem clamped it or just early production problems. I've used an ITM Millenium since.

failure of composite structuresIronbutt
Aug 7, 2003 2:25 PM
I used to be employed as the Quality Control manager for a well respected manufacturer of luxury yachts. One of my responsibilities was the operation of the test lab, where we routinely tested composite structures. If the structure has been damaged, the integrity will be obviously compromised: the structure will loose it's normal rigidity, will flex beyond normal boundaries, and will often let it be known under stress by emitting suspicious noises. As the failure continues to degenerate, often there is visible evidence such as milkiness, reinforcement fibers protruding from the matrix, etc. The problem is that composite structures are very resistant to fatigue, and when ultimate yield is reached, the result is catastrophic failure. And when the structure is hollow, like a tube for constructing a bicycle frame, the only indications of incipient failure may be on the inside of the structure where they are not visible. If the structure is properly designed and well constructed, there will be no noticible weakening throughout it's lifetime. That's why a good boat is as sound now as it was when it was constructed 20 years ago, and a good bike is as sound now as ever was. Now, if the design is pushinig the limits of weight restriction, all bets are off. The normal operating range of the structure well may be at the edge of the failure limits. And if and when those limits are passed, the result is catastrophic failure.
hairline cracks, softness and snap.sievers11
Aug 7, 2003 6:34 AM
As the carbon fiber starts to get weak and age the glue/resin that holds it together will start to weaken its bond. This weakening of those bonds causes the frame to get weak or soft. Many fellow racers consider a carbon fiber components a 2 or 3 year deal (fellow racers, putting hard miles on may last you a lifetime, I don't know) A new carbon fiber frame is stiff and comforable, an old carbon frame is flexy and super comfortable. That flexy characteristic comes from the weakening of those bonds between the fibers. If this weakening get extream it gets soft and hairline cracks will form in the paint. If this happens dump it fast, it will fail very soon. It will start to "crackle" and then fall apart like tearing a piece of shreaded wheat.
Light weight aluminum components are a 2-3 year deal tooDave Hickey
Aug 7, 2003 6:40 AM
I really don't think carbon is any worse than other light weight parts. Manufacturers of light weight aluminum handlebars suggest replacing after 2-3 years too.
Good Call (nm)sievers11
Aug 7, 2003 6:45 AM
Frame manufactuers seem to think they will last foreverTerry_Swisher_PMF
Aug 7, 2003 7:21 AM
They advertise it as the strongest thing out there, but I just don't see that.
based on....?filtersweep
Aug 7, 2003 8:01 AM
Please cite some specific examples of these so-called flexy carbon frames that began life stiff. I have a difficult time believing the tube itself will "soften." I am more concerned about bonding of the lugs, but between fibers? Any research to support your claims? Most research is quite contrary- that carbon does NOT fatigue over time.
based on....?Terry_Swisher_PMF
Aug 7, 2003 8:30 AM
Yeah, that is what I have always heard that carbon does resist fatigue. But now I was reading that they suddenly fail, and I was wondering why? Why does Cevelo have to develop propietary carbon to prevent this from happening. There are a lot of old Trek 5200s out there that aren't just suddenly eploding like Ford Pintos.
Looks like thisalansutton
Aug 7, 2003 8:53 AM
I saw some gruesome picspedalAZ
Aug 7, 2003 4:53 PM
of a guy's face after his carbon fork failed and he face planted on the stem and then the ground and broke his nose, jaw, etc. Ate from a straw for months after that.

Just yesteray, saw pics of a Kestrel frame that fell apart (down tube) after being dropped while being taken off a roof rack.
A friend of mine's fork snapped without warning.Lon Norder
Aug 7, 2003 10:00 AM
He was powering up a hill and all of a sudden he was "stepping into space".
Two carbon incidents involving Calfee frames. Coincidence? nmorange_julius
Aug 7, 2003 10:05 AM
No damage to the Calfee, luckily. nmLon Norder
Aug 7, 2003 10:29 AM
Hmm... Ringing endorsement for Profile Fork nmFez
Aug 8, 2003 8:47 AM