Visualization of meso-structure of carbon fiber reinforced polymer based on eddy current imaging

The imaging of meso-structures within carbon fiber reinforced polymer (CFRP) composites was studied. The visualization of fiber orientations and defects such as missing bundles, wrinkle and gaps in CFRP laminates were realized by using eddy current imaging technique. Firstly, the mechanism and distribution of eddy currents in CFRP plates were analyzed by finite element simulation and circuit theory. The imaging mechanism of CFRP meso-structure based on eddy current method was also described. Then the high frequency eddy current testing (HF-ECT) experimental system for scanning imaging was introduced, and the form and parameters of the eddy current probe were determined. Finally, the eddy current imaging technique was used to detect the unidirectional plate, the orthogonal laminate plate and the four-directional angle-ply laminate plate. The three-dimensional pseudo-color images of the eddy current testing(ECT) signals were plotted and clear fiber textures were obtained. The images were further processed by introducing the filter denoising technique and the two-dimensional fast Fourier transform (2D-FFT) to improve the image resolution and complete the separation of the textures in different directions, so as to realize the accurate positioning of the defects in the unidirectional layer of the laminates.