Carbon frame life cycle

Sooooooo booooooring can't believe I read all of this.

I say this

Well I say this

But I say this

You're all wrong I say this

Yawn

talking about forks, but you get the idea...

http://velonews.competitor.com/2011/07/bikes-and-tech/technical-faq/tech...

"I have tested a lot of steel (mostly True Temper brand tubes) and of course carbon (lots of brands) in fatigue tests and also load-to-fail tests. In high fatigue loading, the carbon forks would eventually lose some stiffness (as much as 5 percent) after many thousands of cycles to represent many years of actual riding conditions. So I would not say the forks would last forever at high loading. You don’t hit high loads on most of your rides though … You should get a lifetime of JRA riding (just riding along).

Steel forks did not lose any stiffness in the fatigue tests. They are typically kind of over built so they never got stressed past the endurance limit (about 50 percent of ultimate tensile strength). In load-to-fail tests, the steel forks bend until they crack, or we would stop when the fork had bent more than 10-20 percent (un-useable).”

So there you go. Sleep easier.
— Lennard"

Some bizarre comments on here - clearly a little knowledge is a dangerous thing.

How long will a carbon frame last?

Indefinitely, as long as you don't crash it or leave it exposed to the elements on a permanent basis (this last part strangely, is true of most bike frame materials).

If you feel the urge to crash your bike regularly buy something else but but recognise than nothing can be fixed 'good as new'. What ever you buy don't leave it out in the sun, rain etc - but then if you're looking at high end carbon I'm guessing you weren't intending to?

I have carbon, steel and aluminium. The steel is 20+ years old and weirdly has rusted. The aluminium has unusually failed to snap yet (15 years old) and the carbon is still going strong despite only having paint to act as a sunscreen. I don't have a titanium bike yet, or a beard but who knows, both of those things may be in my future.

I crashed my carbon TT bike at 25mph. It just sucked it up and Im still racing it 3 years later.

I have carbon forks that are donkeys years old too

I'm fairly sure that no one said it would fail....just that it loses its stiffness.

As for aircraft, yes, it's used as an alternative to....aluminium.....which the thread seems to agree has a low stress life.

I'm not against carbon, I have carbon, I use carbon, but I still believe it has a limited life in use in the real world...just as that expensive re-enamel does on steel.

There's been some discussion, suggesting that if aircraft are made of carbon then carbon bike frames must be just as safe, so I thought I'd just quote what carbon-bike-check.com say on the subject, over in Germany.

"A plane consists of large, massive components which reinforce and support each other. Most are large machine-made components which help reduce inconsistencies. Each part is checked and tested after assembly as a whole. And that is for example the difference between an Airbus and a bicycle. An Airbus is tested and tested and tested. The aviation standards define exactly what, how and how often a component is to be tested. And for bikes, is there nothing? Actually, there are standards but these apply to Type Testing meaning the design is tested using samples before production but they do not apply to the production itself. They are also not mandatory. "

They also go on to say that "a defect-free frame, fork, stem, etc. does not exist", and that "many failures could have been prevented if testing had been carried out beforehand". Ok, CBC's business is the testing and analysis of composite materials, but it certainly makes sobering reading.

Gordy748 posted:

"Carbon has a fatigue life and, over time, flexes more and more every pedal stroke. Every time this happens, it absorbs (fractionally) more and more watts produced by the rider. For a pro, the point at which the frame is unacceptably flexible will happen a lot sooner than a sportive rider."

sorry, this goes against current technical understanding and material behaviour of composites (which is another reason they are now used in passenger aircraft)

one of the big bonuses of carbon fibre composites is that in normal use (in the design envelope) they do not fatigue (unlike aluminium alloy) and withstanding catastrophic impacts (crashes) or environmental degradation (exposure to UV, road salt, etc. which can be guarded against with good finishing) should easily outlast metallic alloy framesets

of course, this assumes good quality control during manufacturing and no in-built 'design flaws' to the composite design or galvanic corrosion from in-moulded metallic alloy hard points (this is why manufacturers are moving to all carbon frames with carbon dropouts, headset cups and bottom bracket tubes)

Many of the comments here are based on made-up facts and urban cycling legends. As someone has already mentioned, many modern aircraft are made of CF because it is the lightest material that offers superlative levels of structural integrity.
Anyone suggesting that CF is more likely to fail is quite simply mistaken.

I wouldn't worry - 6 to 12 months after purchase the bike companies will realise that the headset, BB and brake mounting standards they used to use are all shit, and then new ones are like, so much better it's unreal and we all need to upgrade or be stuck with a 2 wheeled betamax.

Works for Apple, no?

My understanding is that different materials behave differently to load.

For instance aluminium is compromised with every bend, twist, vibration it is asked to absorb. Over time the material degrades and at some point, no matter what you do, it is going to fail.

Steel has a definite yield point. Below that yield point it can suck up as bending, twisting/vibration almost indefinitely. Above that yield point, then the material ages in the same way as aluminium.

Titanium is like steel, although the yield point is considerably higher.... so it can take more extreme bending etc. The challenge with this is that it also makes for a bendier frame, so manufacturers mix in alloys/treat the material in such a way to stiffen it, which also lowers the respective yield point. So.. you can have a ti frame for life, but it rides like poop, or one that rides well, but has a similar life expectancy to steel.

Carbon, as I understand it is a yes/no material. It'll bend, twist, vibrate within a range indefinitely. Push it beyond its limit and it will fail spectacularly, and rapidly. The challenge with carbon is as mentioned, blunt impacts can compromise the material and right now we are still in the realms of developed understanding of the long term degradation of epoxies.
The great thing about carbon is that it is so un-precious its untrue. Punch a big hole in your frame... as long as you fix it, its no bother at all.
Its certainly not the super fragile material some make it out to be.

I'd like to know how many accidents were caused by catastrophic failures and how many catastrophic failures were caused by the accident.
"I fell off due to my handlebars/frame/crank snapping." Sounds better than,
"I was not looking where I was going, fell off and broken part x!"

Going back to the OP, just get a carbon frame if you want, in a few years time you'll be replacing for the next generation of disc braked electronic shifting frames anyway.

I wonder what it's like to live in fear. Fear of teh crabonz.

There's always going to be opposing views on carbon, but you you'd have to be pretty isolated not to have heard, read or seen examples of carbon frames and components which have failed, quite often without any prior warning, sometimes at high speed, and sometimes causing injury to other riders. We all have a responsibilty towards other road users, and indeed towards the resources of the emergency services and the NHS, and clearly far more important than a small weight saving.

You certainly don't have to be an engineer, armchair or otherwise, to conclude that if you really want to ride carbon then it's sensible (and responsible) to only buy from a well known source, destroy any frame/component immediately after suffering any impact, never lend your bike to anyone, and never EVER buy second hand.

Just go for a frame with a lifetime warranty.

Carbon should last as long as any other material - longer even than aluminum, as that is subject to fatigue damage. There's no evidence that ultraviolet light damages carbon fiber, and no evidence that stiffness reduces over time.

Sources:
http://carlhart.com/how-to/how-to-care-for-carbon-bikes-and-parts-pg220.htm

http://www.ibiscycles.com/support/technical_articles/all_about_carbon/

The same comment can be applied to any frame of any material, and I've broken steel and aluminium frames...

The idea that every carbon frame is minutes away from 'catastrophic failure' is one used by people who don't like them, and as above, is not related to material science.

What a load of nonsense.

Trek give a lifetime warranty on their frames, I've got a 14 year old one that's still as good as the day it was bought. People change frames because they go out of style, not for any material science reason.

Your cared for carbon frame will last at least as long as any steel or titanium frame.

The real answer is "all of the above".

Carbon can easily be built to last a lifetime, but you'd have a frame so stiff and heavy as to be unrideable. Older frames were overbuilt using more weave than needed, which is one reason why a C-40 or Kestrel SCi frame can still be bought and ridden today, and also the reason why the frames are pretty heavy.

These days, the frames are buiilt down to a weight, as well as being very stiff. This means less weave is doing more work than in older frames. For a modern frame, the operative issues become rider weight (the heavier the more the frame has to support), rider power (the stronger the more the frame needs to resist flex) and road type (the rougher the more the frame has to absorb vibrations).

Cancellara racing on cobblestones every day will probably go through a frame in 2 - 3 months. A petite female sportive rider only riding on smooth tarmac would get years out of the same frame.

The other thing is the point at which a frame is considered unusable. Carbon has a fatigue life and, over time, flexes more and more every pedal stroke. Every time this happens, it absorbs (fractionally) more and more watts produced by the rider. For a pro, the point at which the frame is unacceptably flexible will happen a lot sooner than a sportive rider.

Bottom line: amateur racers will change carbon frames every 2 - 3 years, sportive riders every 5 - 8 years.