Compressive Buckling of Rippled Graphene via Molecular Dynamics Simulations

This paper studies the compressive buckling of near-square rippled monolayer graphene sheets in thermal environments by using molecular dynamics simulations. Armchair and zigzag graphene sheets are both considered and the four edges of a graphene sheet are either simply supported or clamped. Compressive force instead of the commonly used compressive strain is gradually applied to the edges of the graphene sheet until the graphene sheet is crushed. It is found that ripples in the graphene are formed owing to thermal fluctuations even before the compressive force is applied. The amplitude of ripples is reduced when the compressive force is applied to the graphene. The buckling mode of the graphene may show local or global mode shape features, depending on the chirality, the support conditions and the size of the graphene. Most buckling modes of the graphene sheets are very different from the global (1,1) mode of a uniaxially loaded and simply supported or clamped square plate as predicted by continuum mechanics models. A clamped graphene can take significantly more compressive force after the occurrence of initial buckling and before the graphene is completely crushed. A zigzag graphene has a larger initial buckling force than its armchair counterpart. Raising the environmental temperature may either increase or decrease the initial buckling force of the graphene depending on the support conditions and the chirality of the graphene.