Non-contact ultrasonic inspection of CFRP prepregs for aeronautical applications during lay-up fabrication

The possibility to inspect laminates of prepreg carbon fiber reinforced polymer (CFRP) laminates during lay-up fabrication is studied. First ultrasonic properties of the uncured material are determined, this information is used to design an inspection system that is tested during the fabrication of laminates with up to 30 layers, following different compaction schemes and including some Teflon insertions to simulate the presence of delaminations. The paper shows that for the chosen selection of parameters (transducers sensitivity, centre frequency and mold configuration), the inspection is possible, opening a new field of application of air-coupled ultrasonic techniques.