The fracture toughness of graphene during the tearing process

The fracture toughness of single-crystal graphene and bi-crystal graphene with different misorientation angles is investigated by molecular dynamics simulation. We find that the fracture toughness fluctuates when a crack propagates across the grain boundary. It indicates that the grain boundary affects the fracture toughness during the fracture process. The affected region on the graphene is limited to a small zone around the grain boundary. However, for the complete tearing-failure case, fracture toughness of bi-crystal graphene is approximate to that of single-crystal graphene, which implies that the fracture toughness is not very sensitive to the grain boundary. For comparison, the tensile fracture simulations of the single-crystal graphene and bi-crystal graphene are carried out. The results show that the grain boundaries block the crack propagation and affect fracture toughness significantly in bi-crystal graphene under tensile force. Furthermore, we analyze the fracture of a single C–C bond at the crack tip of single-crystal graphene under tearing load from the atomic view. We find that the fracture toughness of the single C–C bond occupies about half of the fracture toughness for the complete failure of the total single-crystal graphene, and the other half energy distributes in the rest of the graphene. (paper)