High sensitivity self-sensing damage of thick carbon fiber 3D woven angle-interlock composites with oblique current

The electrical potential distribution and current spreading depth significantly influence the sensitivity and resolution of self-sensing damage in thick 3D woven angle-interlock (AI) composites. Herein, we report the potential distributions along the thickness and surface in-plane directions of thick 3D woven AI composites under different current strategies. The damage mechanisms of the composites subjected to multiple low-velocity impacts were investigated. Micro-CT and Ultrasound C-scan techniques were used to analyze the microscopic damage morphology and macroscopic damage area, respectively, to demonstrate the effectiveness of the electrical potential self-sensing method. We found that the current completely spreads through the entire thickness of the thick composite plate under oblique injection mode. The potential values between −5.2 and 2.0 mV measured on the impact back surface of the composite plate are at least twice that of the in-plane current mode (−1.0-1.0 mV). The potential damage envelope mapping under oblique current mode coincides with the micro-CT profile, and is much larger than the ultrasound C-scan outline. It achieved the highest detection sensitivity, resolution and flexibility compared to the current in-plane introduction. A three-dimensional orthogonal potential model was developed to determine the spatial potential distribution. The theoretical results agree well with the experimental data. A quantitative relationship between the effective current penetration δ and electrode spacing an of 3D woven composites under in-plane current was established: δ ≥ 0.5, a≤46.6 mm. The electrical potential method with oblique current injection offers a highly sensitive, cost-effective, and non-destructive solution for accurate structural health monitoring in aircraft.