Impact-induced damage mechanisms and failure evolution in intra-ply carbon/flax hybrid composite laminates

This study evaluates the effectiveness of carbon/flax intra-ply hybridization in enhancing the low-velocity impact performance of sustainable composite laminates. This study provides a rigorous comparative assessment of neat carbon (NCFRP), neat flax (NFFRP), and carbon/flax intra-ply hybrid (CFFRP) composites. Low-velocity impact tests were conducted according to ASTM D7136 at multiple energy levels, and the responses were characterized using force–time, energy–time, and deformation–time histories alongside peak force, absorbed energy, rebound energy, contact duration, and maximum deformation. The results show that NCFRP exhibited the highest peak force, up to approximately 40–50% higher than NFFRP, but displayed limited deformation tolerance and brittle damage at elevated energies. In contrast, NFFRP demonstrated significantly greater deformation capacity, over 60% higher maximum deformation than NCFRP, and progressive energy dissipation, although quasi-perforation occurred at higher impact levels. The intra-ply hybrid CFFRP laminates achieved a synergistic response, increasing absorbed energy by approximately 15–25% compared with NCFRP while reducing maximum deformation by about 30–40% relative to NFFRP. Moreover, CFFRP maintained rebound capability at higher impact energies, indicating delayed damage initiation and improved impact resistance. Failure analysis revealed that hybridization activates complementary damage mechanisms, including matrix cracking, fiber–matrix debonding, fiber pull-out, delamination, fiber bridging, and localized fiber fracture, which collectively enhance energy absorption and mitigate catastrophic failure.