Discussion in 'Bicycle Mechanics and Repairs' started by Bigtallfatbloke, 23 Jun 2008.
...I just read the alu frame thread..interesting...so how long will a carbon frame last?
Until it breaks!
Who knows? Until it breaks is probably the most accurate answer.
Assuming it has been properly designed and fabricated and is cared for well then the answer is probably forever. However, the problem with carbon fibre as opposed to metals is that its failure tends to be catastrophic so there isn't a crack that attracts your attention and stops you riding before your forks snap off!
Because of this people tend to adopt a cautious approach. Since you can't inspect for any internal damage then if the frame or forks get a large knock then they should probably be replaced. But what constitutes a large knock? A crash certainly, but what about your bike falling over or someone banging your bike outside the caff?? (I would have though both of these last two would be okay, but who knows?)
I have a friend who has carbon forks on his time trial bike and he was told he should replace them after two years! Two years has past and he's still running them but admits that he's nervous about them.
The problem with carbon fibre is that it can delaminate on the inside and be far weaker than it should be without showing any signs at all on the outside.
Can you prove it delaminates on the inside Mr Pig? Or is that just your opinion?
I would say Carbon frames will last as long as any other frame. Its impact that will damage it, time won't
> CARBON - Frames - How long...
Makes me think of how the fibres will last ?????????
Yes, but the problem is that you can't see if the impact has damaged it. But I agree, it won't deteriorate with age.
'Delamination' is a mode of failure for composite materials. In laminated materials repeated cyclic stresses, impact, and so on can cause layers to separate, forming a mica-like structure of separate layers, with significant loss of mechanical toughness. Delamination also occurs in reinforced concrete structures subject to reinforcement corrosion, in which case the oxidized metal of the reinforcement is greater in volume than the original metal. The oxidized metal therefore requires greater space than the original reinforcing bars, which causes a wedge-like stress on the concrete. This force eventually overcomes the relatively weak tensile strength of concrete, resulting in a separation (or delamination) of the concrete above and below the reinforcing bars.
Delamination is an insidious kind of failure as it develops inside of the material, without being obvious on the surface, much like metal fatigue.
Delamination failure may be detected in the material by its sound; solid composite has bright sound, while delaminated part sounds dull, reinforced concrete sounds solid, whereas delaminated concrete will have a light drum-like sound when exposed to a dragged chain pulled across its surface. Bridge decks in cold climate countries which use de-icing salts and chemicals are commonly subject to delamination and as such are typically scheduled for annual inspection by chain-dragging as well as subsequent patch repairs of the surface. Other nondestructive testing methods are used, including embedding optical fibers coupled with optical time domain reflectometer testing of their state, testing with ultrasound, radiographic imagining, and infrared imaging.
Some manufacturers of carbon composite bike frames suggest to dispose of the expensive frame after a particularly bad crash, because the impact could develop defects inside the material.
Due to increasing use of composite materials in aviation, delamination is increasingly an air safety concern, especially in the tail sections of the airplanes.
Delamination risk is as old as composite material. During the 1940s, several Yak-9s experienced delamination of plywood in their construction.
Retrieved from "http://en.wikipedia.org/wiki/Delamination"
Taken from the brillant Wiki:site
Carbon lasts longer than metal.Only love is stronger than carbon.Bonding is a different story.I believe that a good glue (epoxy) can last for 2000 hours of work, or about 800 days, not in continuous daylight, and below 35 Celsius.Whenever a carbon "part" has crashed, even if you cannot see a failure, if there is any reasonable doubt about having surpassed the elongation limit, the part must be replaced.
That makes me wonder about a touch of wheels I had a while back.
I think that's the point, you don't know. Obviously pro riders use carbon parts but I doubt if they'll use the same part for years!
I don't think it's a more risky material than steel or aluminum etc, just that the way it behaves and wears out is different. Don't think I'd buy second hand carbon forks though.
Well I cant afford to go replacing carbon frame/forks/stays etc whenever I get a knock or every two years etc...they are dam expensive ....maybe I should revise my plans for a carbon 928 bianchi...although I do love that bike.
BTFB. The two years is just a cover their arse statement from some manufacturers. I would go with the view that carbon fibre stuff will effectively last forever as long as you don't crash it. People have been using carbon fibre forks for years without widepsread failures.
That's probably why titanium is becoming so popular now and so many companies are now specialising in this material.
How about an Enigma ?
I think it is; it is the mode of failure: steel is nice as it is likely to bend first giving you warning whereas aluminium alloy or carbn fibre just snap.
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