Effects of Cu/graphene interface on the mechanical properties of multilayer Cu/graphene composites

Molecular dynamics simulations are performed to investigate the effects of graphene on the mechanical properties in multilayer Cu/graphene composites under uniaxial tension. It is found that both of zigzag and armchair graphene can improve the mechanical strength of multilayer Cu/graphene composites. The enhanced efficiency is concerned with chirality and interlayer thickness of graphene. The Cu/graphene interface has a great effect on the dislocation nucleation and propagation in the plastic deformation. Firstly, the interface can act as a resource of dislocation emission. This is due to the high stress concentrated on the interface caused by lattice mismatch and shear modulus mismatch between Cu and graphene, which can reduce the energy of nucleation. The interface stress of armchair graphene is more evident than the zigzag graphene. Secondly, the dislocations are confined by the impenetrable interface during the propagation process, which leads to intense interaction between dislocations and interface. Both the confinements and interactions are responsible for high stress required during the propagation process. A confined layer slip (CLS) model is established to predict the strength of multilayer composites in quantification. After the fracture of graphene, the dislocations penetrate through the interface of Cu and graphene and the composites would neck and fracture around the region.