Magnetic induction tomography (MIT), a relatively new method of non-destructive testing, is applied to monitor the structural health of carbon fiber reinforced plastics (CFRP). MIT utilizes inductive coils to map the properties of an object. A 3D finite element model of the sensor operation with defects in different CFRP layers is developed to obtain the sensitivity profile and solve the MIT forward problem. Moreover, a linear back projection algorithm was performed to reconstruct images for on-line detection. The results showed that the voltage values induced in the detection coil increase significantly at the defect positions within the related layer. Moreover, the average voltage of the layer with the defect is always higher than at the other layers. This indicates that MIT can easily detect not only surface defects of CFRP but also internal defects successfully and localize them accurately in depth as well.
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.
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