Modeling and analysis of the electrical resistance measurement of carbon fiber polymer–matrix composites

The self-sensing damage detection method based on the electrical resistance measurement of carbon fiber polymer–matrix composites has been investigated for a decade. In order to eliminate the effect of contact resistance when using the two-probe method, the four-probe methods, which include the resistance, potential and voltage change methods, were proposed in literature. However, the basic problems involved in the four-probe methods remain unclear, i.e., the validity range and the applicability of the four-probe methods. In this paper, beam-type specimens with and without delamination damage are used to carry out numerical analyses for the above-mentioned problems. It is found that the four-probe resistance method is valid only when the through-thickness conductivity is comparable to or larger than the longitudinal conductivity. For the potential method, which measures directly the voltage values between the voltage contacts, the present results show that the percentage change in damage-induced voltage between a pair of voltage contacts is not consistent with the percentage change in resistance. The underlying reason is that the damage-induced voltage change depends on the location of the applied current, while the resistance change does not.