Damages Evaluation of low velocity impact on Glass/Polyester-foam sandwich panels using the Acoustic Technique

Nowadays increasing application of Sandwich panels in various structures as like as aerospace and ship is due to excellent high strength to weight ratio, sound insulation and thermal properties. The study of failure mechanism in composites and especially sandwich panels are investigated as cutting edge. In this research, the acoustic emission data of low velocity impact tests has been used to study the impact strength and various defects created in glass / polyester-polyurthane foam composite sandwich panels with 3 different types of Lay-up technique. The analysis of the acoustic data and the study of the force-displacement diagrams and the visual images of the specimens after the various impacts of 20, 38 and 60 J have been studied. For this purpose, the obtained force-displacement diagrams and acoustic energy in each frequency range during the impact tests are interpreted and their relation to the types of failure mechanism, such as matrix cracking, fiber breakage and debonding in this type of sandwich panel has been extracted. Also, by studying the force-displacement diagrams and investigating the maximum reaction force and elastic return strength, acoustic events in signals has been verified. The results showed that the impact resistance of the cross-ply lay-up was30 to 40% higher than other specimens in the all impact tests.