Having recently had a tour round the Force India F1 factory, where carbon fibre isn't in it's infancy, I have the (well, one) answer for you: Ultrasonic detection!
Basically, a part is tested with a bunch of sensors all over it, and then asked to perform it's task (in a rig a bit like how Ikea test their chairs). We saw a nice graph where the stresses on the part were shown, and any red areas indicated weaknesses. Any sign of these not in the areas on the graph where you expect them (e.g. at tolerance limits) and the part is binned.
(excuse the layman reply, but whilst i'm an avid F1 watcher, i've never laid CF or tested it myself!)