Effects of Graphene Defects on Evolution of Dislocations and Pores in Graphene/Al Composites: A Molecular Dynamics Study

Vacancy defects in graphene are inevitably introduced during the fabrication of graphene-reinforced metal matrix composites through mechanical processing, chemical reactions, or in-service environmental exposure. Despite their prevalence, the precise atomic-scale impact of these vacancies on dislocation motion, strengthening mechanisms, and failure behavior remains incompletely understood. To address this gap, we employ molecular dynamics simulations to construct aluminum-graphene interface models featuring systematically varied vacancy defect concentrations, enabling a detailed investigation of dislocation–interface interactions and the underlying reinforcement and failure mechanisms under shear deformation. Compared to pristine graphene, interfaces containing vacancy defects exhibit significantly enhanced out-of-plane buckling when dislocations impinge upon the interface, disrupting the periodicity of buckling waves, reducing interfacial stability, and ultimately degrading the overall mechanical performance of the composite. The buckling amplitude shows a positive correlation with the contact area between vacancies and the dislocation slip plane, highlighting the role of localized defect-dislocation overlap in amplifying structural perturbations. During shear loading, vacancy defects markedly impair load transfer efficiency across the aluminum–graphene interface, precipitating pronounced stress concentrations that nucleate preferentially at the edges of the atomic voids. Consequently, the shear strength of the graphene-reinforced aluminum composite undergoes a monotonic decrease as the defect area fraction increases. Quantitatively, as the defect area fraction rises from 1.24% to 13.8%, the shear strength declines markedly by approximately 14%–15%. Beyond the 13.8% threshold, the mechanical response deteriorates precipitously, characterized by disordered buckling waves localized near the voids, which act as precursors to premature interfacial fracture. These findings provide a theoretical basis for the design optimization of aluminum-graphene composites in experiments.