Carbon fibre framesets can be put into the ground, and if there are components that could fit it, could then be ridden as if it were a brand new bike. The caveat would be that the metallic components may corrode into goo.
A carbon frame will not, however, take the abuse of unprotected travel. Also, if the layup is not correct, it can eventually crack. Also, if the construction is poor, combined with impacts (i.e. numerous crashes, impacts with unprotected travel, etc.), it will eventually be nothing more than an inefficient paper weight (unless it is repaired-which CAN happen) in due time.
I still think it is the ultimate material, though must be used in the correct application.
Hmm, ultimate material? Perhaps a composite made with carbon nanotubes, if only you could make the nanotubes long enough. Or perhaps a monocoque monofilament metal matrix composite, but the possibility of making that is even less likely.
I agree that the blanket “Aluminium has very poor fatigue life…” is too broad and borderline plain untrue. Airplanes are made of the stuff and are subjected to much higher stresses of every kind (Temp change, flexing, UV exposure, catalyst fatigue, etc.) and last for many decades.
First of all, airplanes are designed with fatigue life in mind. In fact, every time you fly, there are plenty of small cracks growing in the frame of your airplane. Luckily, airplanes are constructed in a cellular fashion in order stop crack growth. This way, cracks can be detected, through ultrasonic or other non visual, non destructive evaluation techniques before they are large enough to cause catastrophic failure. All airplanes, military and commercial, are inspected at regular intervals based on flight time. So as someone asked earlier, no, your bike will not fatigue unless you are riding it.
Even though every material can be fatigued to the point of failure, I don’t thing that the stresses a bike frame is normally under is enough bring this about. Most likely cause of a bike frame failure is abuse or poor initial workmanship.
This is the reason aluminum is bad for fatigue. As someone else already mentioned unlike steel, aluminum does not have an endurance limit or minimum strength necessary for fatigue. Therefore, after enough cycles, a fatigue crack will form and a triaxial stress state will be present at the crack tip, causing the crack to grow and eventually lead to structural failure. You are correct though that most bike frame failures are the result of abuse or poor construction rather than fatigue. The failures in the early Cannondale frames were due to cracks in the HAZ (heat affected zone) after welding. This occurs due to a change in microstructure in the base metal surrounding the welds and is now avoided with a post weld heat treatment.
Of coarse I could totally wrong about this. I am an Enviromenal Biologist that sells Industrial machinery, not a Metalurgist.
I study corrosion, but have a degree in Materials Science & Engineering with a specialty in metals. BTW, metallurgist (and metallurgy) has two 'L’s.
Steel does the same thing as aluminum, but it takes more cycles. The analogy usually given is bending a paper clip until failure. An aluminum paper clip will tolerate fewer cycles than steel, but they both will ultimately fail, and in roughly the same mode. Composites just snap at their yield strength limit.
Except that a bicycle is not normally subject to forces that will go beyond the fatigue point of steel. No number of cycles below that point will cause failure.
I should have said “the ultimate material that still has many, many technological advancements to go through”.
Admittedly, carbon has a few growing pains to go through, and it is going to be awhile before it will be as impact resistant as something like ti.
But why I say that it is the ultimate material is it’s infinite tuning characteristics, the ability to make such large, fluid designs with minimal weight (compared to any metal in the same shape), and it ability to use it in so many applications.
Now, on the subject of nano-tech: the surface hasn’t even been scratched, from what I understand. I think that I would call it merely a marketing term, for now. But the future could bring some petty cool stuff…
Dents or large scratches can cause stress concentrations which will cause a crack to propogate quicker. So you have a similar mechanism occurring in a shorter amount of time since the local stress is larger.
I’m actually pretty careful in terms of cleaning it often, checking for any issues that might arise in the middle of nowhere on the open road. I think you might be a bit overly dramatic as to the “one minute its whole, the next it’s not” line of thinking…unless of course, you’ve had personal experience along those lines.
The point I was trying to make is CF gives no warning before failure.
Understood…but earthquakes don’t give us much warning, either. Not trying to be hyper-sarcastic, but I’m not going to fret too much about whether or not my bicycle will disintegrate beneath me. It has served me well for a very long time, is well cared for and despite your claims to the contrary, is showing no visible signs of imminent failure…which for some reason I would believe would be there if in fact something was amiss.
But I suppose it is possible nothing will evident before complete failure. If that is indeed the case, well, wish me luck then!
