Eddy current testing for estimation of anisotropic electrical conductivity of multidirectional carbon fiber reinforced plastic laminates

Eddy current testing methods to estimate the anisotropic electrical conductivity of multidirectional carbon fiber reinforced plastics are proposed in this work. Finite element analysis was performed to investigate the contributions of the three-directional conductivities to the coil impedance. The coil impedance variation was expressed as an approximate function with respect to the anisotropic conductivity using the response surface methodology. Three proposed methods were applied to estimate the conductivity from the measured coil impedance and the estimated conductivities were then compared with the conductivities measured using a four-probe method. Use of the response surface enabled prediction of the lower and upper limits of the conductivity while taking the scatter of the electrical properties in the tested material into consideration. The conductivity range was predicted correctly using the proposed methods. There was a trade-off relationship between the accuracy and the simplicity of these estimation methods.