Originally Posted by shuttlebus
In thinking about planes, it is worth remembering that composites are less likely than metals (such as aluminium) to break up completely under stress. A small crack in a piece of metal can spread very rapidly with very serious consequences (especially in the case of aircraft). The fibres in a composite act to block the widening of any small crack and to share the stress around.
Does the aircraft aluminum, when subjected to excessive forces, fail by cracking, or by bending out of shape while remaining in one piece and keeping its strength?
Also, once a composite is broken, how can it be mended? Metals can be welded, and they commonly were welded in the first building. But composites? I presume that even in case of thermoplastic matrix, if you join them by welding the matrix, the fibres would not be extending through the joint and connected to the fibres on the other side the way they were in intact material...