A simple inverse analysis method for eddy current-based measurement of through-thickness conductivity of carbon fiber composites

A simple inverse analysis method is proposed to measure the through-thickness conductivity of carbon fiber reinforced plastic (CFRP) laminates using eddy current testing. Finite element analyses were performed to investigate the relationship between the eddy current sensor signal and the anisotropic conductivity of a cross-ply CFRP. It was found that the resistive component of the impedance of the eddy current sensor changed with the through-thickness conductivity of CFRP, while the conductivity in the transverse direction had almost no influence on the sensor impedance. Using this characteristic and the conductivity in the fiber direction determined by fiber volume fraction, the through-thickness conductivity of a CFRP laminate was estimated from the resistive component of the impedance of the eddy current sensor. Experimental studies showed that the through-thickness conductivity estimated by the proposed eddy current testing method was in good agreement with that measured by the four-probe method. The proposed eddy current method enables fast and non-contact measurement of the through-thickness conductivity of CFRP laminates.