Preliminary study on defect detection for sandwich composites using Impact-Echo method

The sandwich composites in this study are laminated structures with two outer thin glass fiber reinforced panels and one or more thick lightweight foam as the core material. Such often used wind turbine blade. Impact-Echo method using a microphone receiver was to test composite panel specimens. signals were analysed frequency domain normalized by Rayleigh wave amplitude. Preliminary results show that thicker plates generally have lower maximum peak (MPF) for specimens without defects, but MPFs unstable due higher number of layers inner plate. Internal defects generated excavating material, lateral dimensions small 20 mm, can be identified from MPF amplitude spectrum.