Electric heating repair of short carbon fiber-reinforced polymer composites

Carbon fiber-reinforced polymer composites are susceptible to damage in practical applications, and their damage repair has attracted significant attention. In this study, an electric heating repair (EHR) method was proposed for repairing fatigue damage of short carbon fiber-reinforced polymer composites (SCFRPCs), leveraging the intrinsic electrothermal effect of SCFRPCs. First, the EHR method was evaluated through mechanical testing, and both tensile strength and fracture toughness of SCFRPCs were improved after EHR. The heating temperature of the specimens reached approximately 115 degrees C (close to the matrix's melting point of similar to 120 degrees C), demonstrating the efficacy of this repair method. Subsequently, the influence of electric heating power and duration on damage repair effectiveness was systematically analyzed. With optimal electric heating parameters, the maximum improvements in tensile strength, fracture toughness, and ductility reached 19.3%, 74.0%, and 13.8%, respectively. Conversely, insufficient or excessive heating parameters diminished the repair effectiveness. Furthermore, the microstructures of the original, fatigue-loaded, and repaired specimens were quantitatively compared, including fiber-matrix interfaces and fiber failure modes. Quantitative analysis indicated improved interfacial bonding between fibers and the matrix after EHR, and the fiber failure transitioned from pull-out to breakage modes. This enhanced bonding at the microscopic fiber-matrix interfaces accounts for the restored macroscopic mechanical properties. Overall, the EHR method demonstrated its capability to repair damages of SCFRPCs, offering a promising in situ repair approach for composite structures.