▎ 摘　　要

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.