CARBON - Frames - How long...

[Blue]

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.

What personal experience do you have of snapping carbon parts? Do you have any stats that show that carbon frames fail more frequently than frames made of other materials? Why do the sellers of Ti bikes put carbon forks on the machines if they are likely to snap and involve the rider/frame in the subsequent crash?

I've been riding carbon for 3 years without problem and the only damaged carbon I've seen in my LBS has been crash damage.

I wouldn't be happy with any frame/fork after a heavy impact, no matter what the material.

Is this thread moving into the usual realm of "don't take carbon out in the rain as it will dissolve like sugar" type rubbish that gets written about carbon????

 

[Mr Pig]

I think his point is that 'if' a carbon part were to fail it would be a sudden catastrophic failure, you'll get no warning. That's all he's saying.

It's easy to say 'yeah, I'd get rid of it after a crash' but realistically how many people do that? For the average recreational rider, who doesn't have limitless money, if the bike looked as good as new after a tumble they'd just keep using it. I think the main point here is that metal will tend to show cracks or deformation on the outside as a first indicator of stress-related damage where as carbon fails from the inside out.

 

[Steve Austin]

there is a hell of a lot of CRAP being posted on this thread.

 

[Steve Austin]

Is this thread moving into the usual realm of "don't take carbon out in the rain as it will dissolve like sugar" type rubbish that gets written about carbon????

Exactly what i was thinking

 

[Steve Austin]

..... where as carbon fails from the inside out.

What a load of rubbish!!!! Where are your facts?????

CAN YOU PROVE THIS?????

 

[Chris James]

What a load of rubbish!!!! Where are your facts?????

CAN YOU PROVE THIS?????

Do you have a carbon fibre frame by any chance?

 

[Mr Pig]

Do you have a carbon fibre frame by any chance?

I don't know, but he does have a button with a question mark on it! ;0)

 

[Steve Austin]

Spouting nonsense again aren't you Mr Piggy. Making vast sweeping statements with nothing but your incorrect opinion to back it up.
If you could back up any of your pseudo facts with some actual evidence i might believe you. As it is you are just talking rubbish

 

[Steve Austin]

Do you have a carbon fibre frame by any chance?

yes i do. A Giant TCR

 

[02GF74]

What personal experience do you have of snapping carbon parts? Do you have any stats that show that carbon frames fail more frequently than frames made of other materials? Why do the sellers of Ti bikes put carbon forks on the machines if they are likely to snap and involve the rider/frame in the subsequent crash?

I've been riding carbon for 3 years without problem and the only damaged carbon I've seen in my LBS has been crash damage.

I wouldn't be happy with any frame/fork after a heavy impact, no matter what the material.

answers to your questions.
1. none personally but the statements comes from what I have read and seen; note how carbon fibre car parts disintrigrate rather than bend like steel would. (just watch F1)
2. I did not state that CF fail more than other frames.

 

[andy_wrx]

note how carbon fibre car parts disintrigrate rather than bend like steel would. (just watch F1)

Irrelevant !

C/F parts on F1 cars are not designed to bend - in fact, they're designed not to bend !

The aero C/F components are designed to be very light and very strong, to take huge downforce loads without deforming or bending, are not designed to take impacts : they are wings not bumpers !
(in fact, the earliest wings in F1, on the Lotus 49 back in the 60's, were of aluminium/magnesium alloy and glass-fibre - they've never been steel...)

The impact-resistant C/F crash-structure components - the tub, the nosebox, the driver protection cell, the fuel tank, etc - are designed to take impacts and are compulsorarily impact-tested on a rig.
Some are designed very strong to protect the driver by resisting penetration or deformation, others are designed to dissipate the impact by deforming or even breaking.
- but they're only designed to do this once : F1 is a non-contact formula, not stockcars.


Carbon fibre can be impact resistant - think expensive tennis rackets for instance.
But not as impact resistant as steel - think a hammer or axe.

A high-end bike which is carefully treated is perhaps more like the expensive tennis racket, a city bike which is constantly being knocked about and abused, scratched and bashed is perhaps better made out of old thick-wall gaspipe steel.

 

[02GF74]

so tell me what will happn if you take a steel tube and one made from carbon fibre and start to bend it?

Will the CF bend like the steel or will it snap?

of tkae the same two tube and whck them really hard with a hammer?

will the CF faltten like the steel tube or will ir break?

 

[Chromatic]

so tell me what will happn if you take a steel tube and one made from carbon fibre and start to bend it?

Will the CF bend like the steel or will it snap?

of tkae the same two tube and whck them really hard with a hammer?

will the CF faltten like the steel tube or will ir break?

What point are you trying to make here, this is totally irrelevant.

 

[Chris James]

What point are you trying to make here, this is totally irrelevant.

No it isn't. The point he is making is that carbon fibre parts will fail without warning, unlike steel. Whether this matters depnds on the risk the owner of the part feels is reasonable.

Using standard Failure Mode and Effect Analysis, for example, you would look at the likelihood of a failure, the severity of a failure and the likelihood of a defect escaping detection. The risk would be a product of all of these.

So for example the severity of defect resulting in a fork failure would be the same for any material (pretty bad! - so say 10 out of 10). The likelihood of a steel fork failing is very small (maybe 2 out of 10) - carbon forks resistnance to failure is less well known but it may be less than steel (say 1 out of 10 scoring).

The killer is the detection score.

For steel any potential failure will be easily observed due to a whacking great crack becoming visible, strange clicking noises etc and you can retire the fork or at least stop the bike before you crash. So a low score of 1 out of 10 may be applicable.

For carbon fibre, due to the failure mechanism of composites you are very unlikely to be able to see a defect that will lead to failure. Consequently you would have to give it a very high score. Maybe even 10, unless you adopt a cautious replacement strategy (in which case you could reduce the detection score but still not as low as one based on inspection).

I am not sure how clear my post above reads, so an alternative explanation can be found at Wikipedia. You can put in your own numbers to come up with your own risk rating if you disagree with mine. This is a standard tool for risk analaysis.

http://en.wikipedia.org/wiki/Failure_mode_and_effects_analysis

 

[andy_wrx]

What point are you trying to make here, this is totally irrelevant.

No it isn't.

Oooh yes it is !

A bicycle isn't designed to be bent or hit with a hammer.

If it were, carbon fibre would be a poor material to make it from.

But so would the majority of high-tech steels, aluminium or titanium !