Dislocation Nucleation in Nickel-Graphene Nanocomposites Under Mode I Loading

Abstract

Graphene has superior mechanical properties, and previous studies have shown that it can be used as a fiber laminate in metal-graphene nanocomposites. Our research outlines the advantages and disadvantages of different Ni-graphene nanocomposite laminates. Using molecular dynamics, Ni-graphene nanocomposites are studied under mode I loading normal to the graphene laminate plane. The stress intensity factor ($K_{\text{I}}$) is predicted for the nanocomposite at varying distances between a simulated crack and the graphene sheet(s) in the Ni-matrix. We find that $K_{\text{I}}$ of the Ni-matrix is reduced with the addition of graphene sheet. However, for a single graphene sheet in the Ni-matrix, $K_{\text{I}}$ increases with increased spacing between the crack and the graphene sheet. This is due to the change in the crack-generated stress field in the region between the Ni-matrix containing the crack and the graphene sheet, which leads to the lower stress values at which dislocation nucleation occurs compared to single-crystal Ni. For multiple layers of graphene sheets in the Ni-matrix, we find that failure occurs exclusively by delamination at a lower stress than the one-layer case. This research concludes that fabricated Ni-graphene nanocomposites can be tuned for optimal fracture strength by the structural arrangement of graphene sheets within the Ni-matrix.