Examination of the Effects of Homogeneity and Anisotropy on Coating Thickness and Properties in Reinforced Carbon–Carbon by Eddy Current Testing

Abstract

Abstract Silicon carbide coating is widely used in various industrial fields and plays an important role in protecting carbon fiber composite materials. Meanwhile, coating thickness is directly related to the performances of the functional coating and the substrate. Therefore, accurate coating thickness inspection and substrate property research are extremely valuable. Based on eddy current testing, this study investigated the effects of homogeneous electromagnetic properties and anisotropic conductivities on the performance of carbon fiber composite with different coating thicknesses. This investigation was conducted by simulating a three-dimensional finite element model of carbon fiber substrate–silicon carbide coating by ANSYS. Results showed that under homogenous conductivity of carbon fiber composite, the voltage values of the detection coil array were symmetrical about the axis of the excitation coil. Therefore, this property avoids detecting the repeatability of measurement data and shorts processing time to improve detection efficiency. Simultaneously, the change in mutual resistance exhibited a positive correlation with increased coating thickness. This trend was similar to that of the self-resistance of the excitation coil in anisotropic conductivity. Furthermore, the self-resistances of the excitation coil in anisotropy and the coating thickness meet a formula. Furthermore, supposing the carbon fiber composite material was in the x-axis direction, the electromagnetic signal was exactly opposite to the y-axis direction perpendicular to the x-axis.