The highest profile material failure in recent times was cracking of the new 7449 aluminium alloy in A380 wing ribs, luckily this was not catastrophic. It is quite likely that this alloy (which is from the late 90s) is less well studied than the composite in the 777 wing.
I am curious as to why there should be any suspicion about the use of composites. How many metallic crash helmets are there? How much safer are modern formula 1 cars then their metallic forebears? How often do you hear of composite hulled boats breaking up?
Oh and why isn't this thread in Tech Log