Lattice trapping and crack decohesion in graphene

Lattice trapping is an important aspect in accurately understanding the fracture behaviors of nano materials. Employing molecular dynamics simulations, we studied the lattice trapping of nanocracks in both single-crystal and polycrystalline graphene. Different crack-dislocation and crack-grain boundary configurations were constructed and investigated. It is found that cracks in single-crystal graphene exhibit negligible lattice trapping, with or without the presence of dislocations. On the other hand, lattice trapping in polycrystalline graphene may vary greatly and is shown to be directly correlated to the tensile strength of grain boundary. Moreover, we showed that unique dislocation-independent traction-separation behaviors, which are not affected by the presence of dislocations, exist for cracks in single-crystal graphene. The traction-separation relation was then fitted to a cohesive zone model to demonstrate the possibility of bridging atomistic modeling with large-scale numerical simulations. Our findings provide critical hints for atomistic-informed multiscale modeling of fracture of two-dimensional materials. (C) 2017 Elsevier Ltd. All rights reserved.