Improved Interlaminar Fracture Toughness of Carbon Fiber/Epoxy/Core‐Shell Rubber Composites by Multiscale Toughening Mechanisms

ABSTRACT Carbon fiber reinforced polymers (CFRP) composites, prized for their outstanding mechanical properties, have garnered extensive applications across critical industries including aerospace, transportation, new energy systems, and power infrastructure. However, under increasingly demanding service environments, improving the interlaminar fracture toughness of CFRP composites has become a pivotal challenge to ensure structural integrity and longevity. The present work presents an effective design strategy to address this issue for the carbon fiber/epoxy/core‐shell rubber composite by integrating multi‐scale reinforcements. The mechanical performance of specimens with different compositions was systematically analyzed. Synergistic multi‐scale toughening mechanisms were rigorously elucidated through fracture surface morphology analysis and correlative mechanical data interpretation. The results demonstrate that incorporating short carbon fibers (SCF) into CFRP (i) and adding core‐shell rubber (CSR) to CFRP (ii) both significantly enhance the toughness. CFRP (iii), which contains both SCF and CSR, exhibits an even more pronounced toughening effect. The subsequent grafting of carboxylated multi‐walled carbon nanotubes (MWCNTs‐COOH) onto SCF, resulting in CFRP (iv) with SCF‐CNTs and CSR mixed, demonstrates superior interlaminar fracture toughness compared to CFRP (iii). Specifically, the and of CFRP (iv) increase by 12.89% and 15.46%, respectively, compared to CFRP (iii). This improvement is attributed to the strengthened interfacial bonding between MWCNTs‐COOH and the matrix through mechanical interlocking, which enhances fiber bridging and the effects of core‐shell rubber. This multi‐scale reinforcement paradigm provides critical insights into the design of damage‐tolerant CFRP composites for extreme operational scenarios, advancing their deployment in next‐generation engineering systems subjected to complex mechanical loads.