Multiscale Interfacial Engineering Coupled With Controlled Crystallization Dramatically Improves Delamination Resistance of Thermoplastic Fiber Metal Laminates

ABSTRACT Delamination remains a key challenge limiting the impact resistance performance of fiber metal laminates (FMLs). Although metal surface treatment and nanofiller interface modification are expected to improve interlaminar fracture toughness, the synergistic mechanisms of processing‐induced crystal structure and multiscale interfacial structures remain unclear. This work developed a novel strategy that combines cooling processes and multiscale interfacial structures to significantly improve the mode I interlaminar fracture toughness of thermoplastic FMLs. Aluminum alloy was phosphoric acid‐anodized to obtain nanopores that enhance the substrate anchoring effect. A “U‐shaped” multiscale reinforcement structure that retards crack propagation was constructed by introducing oxidized nanofibrillated cellulose (TONFC) into glass fiber/polypropylene fabric through chemical bonding. The crystallization kinetics, phase evolution, and spherulite morphology under varying cooling rates were systematically characterized. The results show that, under the combined effect of rapid cooling (40°C/min) and the optimal TONFC content (0.44 wt%/wt%), the peak crack propagation fracture toughness of the laminate can reach 3.53 kJ/m ² . This value is significantly higher than that of laminates cooled at slow and medium rates, representing increases of 212.4% and 702.3%, respectively. This superior performance originates from the synergistic effect of a broader crystallite size distribution, the formation of toughening ‐phase crystals, and a robust chemically bonded interface that promotes matrix plasticity and fiber bridging. This research offers a new pathway to enhance interlaminar fracture toughness in thermoplastic FMLs by developing multiscale interfacial architectures.