Enhanced tensile performance of damaged CFRP laminates via microwave-cured skin-integrated repair: Experiment and progressive damage simulation

This study develops a rapid and efficient microwave-assisted skin-integrated repair (MSIR) strategy for carbon fiber reinforced polymer (CFRP) laminates. The strategy synergizes a novel microwave curing process with an externally bonded prepreg skin design. Experimental results demonstrate that the optimized microwave curing achieves a near-full cure (99.9%) in merely 15 min, over 99% faster than conventional room-temperature vacuum-assisted resin infusion (VARI). Mechanistically, microwave volumetric heating enables rapid and uniform resin cross-linking within the repair zone, minimizing thermal gradients and ensuring robust interfacial bonding. Tensile tests show that the microwave-cured patch-only repair recovers 72.9% of the original strength, outperforming the VARI repair (68.5%). The incorporation of an external skin significantly enhances the repair efficiency to over 80%. A three-dimensional progressive damage finite element model, validated by experimental data (deviation <5.5%), elucidates the failure mechanisms: interfacial debonding dominates patch-only repairs, whereas the external skin acts as a load-sharing member that redistributes stress and shifts the failure mode from interface-driven debonding to synergistic tensile fracture of the parent laminate and the skin. Simulation-guided optimization of a full-length skin configuration predicts a repair efficiency of 92.6%, establishing the performance upper bound for this approach. This work provides a cohesive rapid-repair framework encompassing process, design, and predictive simulation for high-performance restoration of CFRP structures.