Molecular Dynamics Study on the Interfacial Properties of Short Kevlar Fiber Reinforced Polyphenylene Sulfide Composites

Polyphenylene sulfide (PPS) is a high-performance thermoplastic engineering material known for its excellent chemical resistance, thermal stability, and flame retardancy. In this work, the interfacial mechanical behavior of short-cut Kevlar fiber-reinforced PPS composites was systematically investigated by all-atom molecular dynamics (MD) simulations. By constructing a full-atom interface model between an amorphous PPS matrix and a Kevlar crystal, interfacial normal tension and tangential shear simulations were performed to reveal the mechanisms of load transfer, damage initiation, and damage evolution at the molecular scale. The results show that the interfacial normal tensile strength (approximately 245 MPa) is lower than the bulk tensile strength of pure PPS (approximately 270 MPa), which is attributed to the stiffness mismatch at the interface induced by the high modulus of Kevlar fibers, promoting the preferential initiation and propagation of voids near the geometrical interface. The tangential shear process exhibits pronounced stick-slip characteristics, with the interfacial binding energy fluctuating periodically with shear displacement, corresponding to the alternating establishment and rupture of non-bonded interactions between molecular chains. This study provides a theoretical basis for the micromechanical design of high-performance thermoplastic composite interfaces and identifies molecular-level optimization directions for future interfacial modification strategies of Kevlar/PPS systems.