Numerical analysis of correlation between fibre orientation and eddy current testing signals of carbon-fibre reinforced polymer composites

This paper deals with eddy current testing simulation for carbon-fibre reinforced polymer composites (CFRPs) using an edge - element FEM code. The FEM code is based on the A formulation and it uses the coupled analysis with external fields. The coil impedance variations due to the fibre orientation and cracks in CFRP plates with unidirectional plies are computed. The conductivity of CFRP is characterized as low value and high anisotropy, which cause the distinct difference between CFRP and isotropic metal ECT signals. The correlation of the fibre orientation with coil impedance variations is obtained, but the exact fibre arrangement in a composite plate can't be ascertained because of signal symmetry. Another method for determining the fibre orientation via the edge effect is presented in this study. According to the numerical results, the shape of cracks in a CFRP plate is not easily evaluated from the detection signal curves unless the fibre orientation is perpendicular to the crack path.