Multiscale crystal structure dependence of quasi-static and low-velocity impact resistance of glass fiber reinforced polypropylene composites

Thermoplastic continuous glass fiber reinforced polypropylene (CGF/PP m ) composites are promising next-generation structural materials, prized for their lightweight nature and recyclability. Critically, the mechanical properties of these composites can be substantially enhanced by tailoring the crystallization behavior of the polypropylene matrix. However, the stress transmission mechanism mediated by the multi-scale crystalline architecture (e.g., spherulites, lamellae) under quasi-static and low-velocity impact conditions remains insufficiently elucidated. Thus, this paper parses the crystallization kinetics and micron/nano-scale structural parameters to establish a coupling relationship between the cooling process, the resultant crystal structure, and the macroscopic mechanical properties. Then, the underlying regulatory mechanism through which a specific microcrystalline structure dominates stress transfer and energy dissipation is revealed. Results show under a high-energy impact of 75 J, the impact resistance of CGF/PP m prepared at low supercooling was improved by 45.1% compared with that prepared at high supercooling, and no perforation damage occurred. Large spherulite size with reduced deformation deflection, thick lamellae and low size distribution of crystallites, and spherulite boundary effects that induce lateral propagation of normal impact force are found to be the main elements that dominate the mechanical properties at low cooling rate. This work may pave the way for improving mechanical properties of thermoplastic composites via generating specific crystalline structures.