Prediction of graphene's mechanical and fracture properties via peridynamics

Although graphene is believed to be the strongest material, many properties of this material are still worth exploring and discovering, especially the influence of inevitable defects in its preparation on the mechanical and fracture properties which are of high significance. This work provides a new feasible way to study the mechanical and fracture properties of graphene. The novelties of this study are threefold: (1) A novel peridynamic (PD) model is proposed for polycrystalline graphene in which grains of large size exist; (2) The coupling effect of the pre-crack length and the grain size on the inverse pseudo Hall-Petch relation is revealed; (3) The results confirm the applicability of classical Griffith theory in brittle fracture analysis of graphene. Based on the proposed PD model, dependence of the mechanical and fracture properties on the grain size which changes from a few to hundreds of nanometers is investigated in this study. The fracture forms of graphene are consistent with the experimental observations. Based on the Griffith theory, the obtained fracture toughness such as K_c (i.e. 3.8MPam - 6.3MPam) or G_c (i.e. 14.0 J/m² – 40.9 J/m²) is comparable with previously reported theoretical and experimental values, which proves the validity of the proposed PD model. Besides, the fracture toughness can be greatly enhanced by the blunt pre-crack tip. This work presents insights into mechanical failure of graphene and guidance on fragmentation of graphene for its practical use.