Molecular dynamics study of fracture toughness and trans-intergranular transition in bi-crystalline graphene

We investigate the deformation and fracture behaviors of pristine and bi-crystalline graphenes by molecular dynamics simulations. For pristine graphene with a pre-crack, fracture toughness is strongly dependent on the crack morphology and atomic configuration at the crack tip. For bi-crystalline graphene, fracture toughness becomes comparable to that of pristine graphene with increase in density of topological 5–7 defects arranged uniformly along grain boundary due to cancellation of the dipole stress field. In addition, we find that trans-intergranular transition can occur during the rupture process with increase in the slant angle of grain boundary with respect to the external loading direction. Our findings provide a fundamental understanding of failure mechanisms and fracture behaviors in graphene and other two-dimensional materials.