On the anisotropic behavior of electrodes for electrical-based monitoring of CFRP laminated composites

Electrical impedance tomography (EIT) is a promising structural health monitoring technique for carbon fiber-reinforced polymer (CFRP) composites. EIT technique has been specifically adopted as a non-destructive testing method along with the electrical characterization methods. Electrodes are the primary component in any EIT system because they act as an interface connecting the instrument/hardware to the structure under inspection. Simulation of electrical inspection of CFRP usually assumes the electrodes to be electrically isotropic interfaces. We show here that such isotropic assumption is a very poor approximation. We experimentally investigated the electrodes contact impedance behavior on CFRP-laminated composite specimens for different surface processing (sanding, CO ₂ laser, and Yb-fiber laser). The effective electrical responses of electrodes are characterized in-depth, so an accurate description can be proposed. Our findings emphasize that the electrodes contact impedance is strongly anisotropic, and varies largely between the on-axis (along surface fibers) and the off-axis (bias and perpendicular to the surface fibers) for all tested surface processing. POLYM. COMPOS., 2018.