Deformation and spallation of shock-loaded graphene: Effects of orientation and grain boundary

Abstract

We perform molecular dynamic simulations to investigate the effects of orientation and grain boundary (GB) on shock response of graphene, including shock-induced slip and spall. For compression under different loading orientations, the critical resolved shear stress for slip is constant along a given growth direction (armchair or zigzag) in single-crystal graphene, and spall initiates in elastically deformed graphene via tension-induced debonding. For bicrystal graphene, the locations of compression-induced slip and initial spall are influenced by preexisting stress field at GB and the interactions between GB and shock waves, respectively. Both of these two factors are related to GB structure, including the density of pentagon-heptagon pairs at GB. However, bicrystals show negligible anisotropy in shock-compression response. For polycrystalline graphene at high shock strength, slips initiate at GBs and triple junctions under shock compression, develop along GBs or toward grain interior, and serve as nucleation sites for spall damage.