Tailoring crystalline structures via cooling rate control to enhance mechanical properties of novel thermoplastic fiber metal laminates

Material selection and processing conditions critically determine the mechanical performance of thermoplastic fiber metal laminates (TFMLs). However, the relationship between cooling rate, crystalline structure, and mechanical behavior remains unclear. In this study, the novel 3/2-type TFMLs were fabricated using glass fiber-reinforced polypropylene composites and PE-g-MAH adhesive films, and the effect of cooling rate on multiscale crystalline architecture and mechanical properties was systematically investigated. Results show that a medium cooling rate (10 °C/min) produces the thickest amorphous regions and induces banded spherulites with concentric ring morphology. This structure reduces tie-chain density and interfacial stress transfer, leading to the lowest interlaminar fracture toughness. In contrast, rapid cooling (40 °C/min) forms a denser chain network and enhances interfacial strength, resulting in superior tensile and flexural performance. Under impact loading, however, TFMLs prepared at the medium cooling rate exhibit the highest resistance to high-energy impact (75 J), with a 43.4% improvement compared to rapidly cooled laminates. This is attributed to the synergistic effect of interlamellar slip, lateral stress redistribution, and progressive delamination, which promotes energy dissipation and delays perforation. This work establishes a clear structure–property relationship governed by cooling rate, and provides a practical strategy for optimizing the impact resistance of high-performance TFMLs.