Mad Jock
You do have a very good point about quality control with composite structures, we inspect the job at each stage to make sure that all has been put together correctly, the post cure temperature and time are monitored by two independent systems, a sample of the resin is kept for analissis and if it is a spar boom we are repairing a test sample of the rovings and resin are made as the spar is being assembled. This test sample is tested in the same rig at the manufactures as they test samples of new spar booms.
Composite quality control is not a problem if it is done at the time of assembly but is as good as imposable once the assembly has been compleated, this is unlike most metal repairs were it is clear if a repair is not up to standard just visual inspection.