Molecular Dynamics Studies on Size Effects in Laminated Polycrystalline Graphene/Copper Composites: Implications for Mechanical Behavior

Nanolaminated graphene/metal composites possess many outstanding mechanical properties due to the high load-bearing capacity of graphene. Considering that actually prepared graphene is usually polycrystalline, in this work, the mechanical responses of nanolaminated polycrystalline graphene/copper (PGr/Cu) composites subjected to uniaxial compression were simulated using the molecular dynamics method. The effects of grain boundary and size (the thickness of the Cu layer, h, and the size of PGr grains, d) on the mechanical properties and the underlying mechanisms were explored. It was found that h affects the mechanical responses in both the elastic and plastic stages, and the mechanical properties of the composites could be enhanced with the decrease of h, while d mainly affects the mechanical behavior in the elastic stage and has a negligible effect on the plastic stage. It was also found that extended dislocations would dominate the plastic deformation of the nanolaminated PGr/Cu composites. Two dislocation propagation paths were observed, and the interfacial barrier that hinders the propagation of dislocations is the primary strengthening mechanism. It was suggested that the confined layer slip model could be extended to predict the strength of the nanolaminated PGr/Cu composites. The results presented would be of great significance for the engineering application of nanolaminated polycrystalline graphene/copper composites.