Research on laser ultrasonic propagation characteristics and quantitative detection of delamination of carbon fiber composite

Abstract

Aiming at the problems of low signal-to-noise ratio (SNR) and low detection accuracy in the non-destructive testing of composites with anisotropic and multilayer structure, the delamination detection of composite materials is studied by using the advantages of laser ultrasonic micro defect detection combined with phased array technology. Firstly, through finite element simulation, the propagation characteristics of laser ultrasound when the delamination evolves are obtained, and a time-modulated phased array laser ultrasound test platform is designed to improve the SNR and detection efficiency of the delamination signal. Then, a laser ultrasonic feature extraction method based on the improved Hilbert-Huang transform is proposed. It includes optimizing the decomposition process of CEEMDAN (Complete Ensemble Empirical Mode Decomposition with Adaptive Noise), searching for the sensitive IMF components through correlation coefficient between the decomposed signal and the original signal, and extracting the feature parameters by Hilbert transform. Finally, the maximum amplitude imaging of the delamination defects is performed using the extracted feature parameters. Experiments show that the proposed method can characterize the delamination characteristics with high accuracy, effectively solve the interference of resin layer on the delamination characteristic signal, and can visualize the delamination in composites.