Non-Destructive Testing of Multi-Layer Composites Based on Microwave Time Reversal

Microwave time reversal (MTR) is a potential nondestructive testing (NDT) technique for multi-layer composites. In our previous study, the effectiveness of MTR for small buried defect detection was investigated in two-dimensional (2D) homogeneous composites, and the localization problem caused by the strong reflection from metal was revealed first. This paper discusses the effectiveness of MTR for NDT of multi-layer composites in 2D and three-dimensional (3D) cases. The improved entropy regularization method is used to solve the localization problem by combining the information provided by the target response signal, and correct defect detection for small buried defect and extended defect is achieved. Furthermore, the multi-scale effect caused by composites and small defect leads to longer detection times in 3D cases. Message passing interface and GPU parallel computing are used to accelerate the defect detection process to achieve efficient defect detection.