Originally Posted by
dvdslw
If you bend aluminum, it can be straightened. If you crack aluminum, it can be welded. We have an aluminum welder at our auto shop and I have seen several parts including body panels repaired so your theory of not being able to repair aluminum is flawed. As far as carbon goes, sure you can patch it but what about the layup? The strands of carbon fiber are "laid" down in certain lengths and patterns to give it strength so just patching a hole only fixes the cosmetic damage but leaves the affected part more susceptible to a catastrophic failure. Sure an aluminum or even steel bike could be damaged beyond repair but the same amount of force that noodled the metal frame would surely wreck a carbon frame as well.
Aluminum frames tend to use drawn tubes which are heat treated. Straightening might require a post-heat treat to eliminate work hardening. Welding on thin-walled drawn tubing is probably not recommended to fix cracks, especially since the frame is load bearing (body panels on cars are not load bearing). The weld itself will form a stress concentration that might lead to more cracking, and will probably require a heat treat as well.
When carbon is repaired, I believe the repair strategy is to cut out the damaged area and re-build the carbon tube structure with new pre-preg carbon fiber sheet. The orientation of the carbon strands is such that the repair is over-built; the intent being that the repaired area is more than strong enough for the frame location. Last I checked, it cost about $400 to repair a carbon frame and most of the time is a pretty routine repair.
__________________
Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --
the tiniest sprinter