Detection Of Hidden Defects In Carbon Fiber Reinforced Plastics Based On Electromagnetic Eddy Current

The research on eddy current testing(ECT)of carbon fiber reinforced plastics(CFRP)is limited in fiber orientation detection and surface crack detection nowadays,and the CFRP plates to be studied are mostly thinner than 1mm,which greatly limit the practical application of ECT for CFRP materials.composite material in damage detection.In the actual non-destructive testing(NDT)process,a large number of defects are not on the surface of the structure,but hidden in the structure.In order to improve the applicability of the ECT for CFRP materials,this paper studied the detection method of eddy current testing for CFRP hidden defect by simulation and experiment.The work done in this paper mainly includes,First,COMSOL software was used to simulate the eddy current field of CFRP plates,and the way to improve the detection ability of eddy current testing on hidden defect was analyzed.Firstly,the accuracy of the simulation software was verified by the eddy current testing benchmark problems.Then,hidden defect models of CFRP plates was established.The distribution of eddy current in CFRP plates,skin effect and the influence of frequency on skin effect was studied.The effect of probe center distance on the detection of hidden defects in CFRP plates was also studied;Secondly,the hidden crack specimens of CFRP plates were fabricated.The influence of the signal characteristics and the influence of frequency on the ECT of hidden cracks at different defect depths was studied.Two multi-frequency ECT information fusion methods were proposed,the signal-noiseratio(SNR)of ECT C-scan image was increased.Based on the edge detection algorithm,hidden cracks of different lengths were tested,laying a foundation for the quantitative detection of hidden cracks;Thirdly,the CFRP delamination specimen was fabricated.The influence of frequency on different depth delamination defects detection by ECT was studied.The detection ability of delamination defect was improved by increasing the center distance of the probe and using the multi-frequency information fusion method.