Micro-mechanism and influencing factors of graphene foam elasticity

The emerging graphene foams (GrFs) have received increasing attention in both scientific and engineering fields in recent years. A good elasticity is the prerequisite for its further applications. However, the mechanism and basic characteristics of elasticity of GrFs have not been understood clearly so far. In this paper, we conduct systematic simulations of compression-uncompression and tension-untension to study the characteristics of GrF elasticity using the coarse-grained molecular dynamics (CGMD) method. We find that deformation of GrFs is highly nonuniform at the scale of both flakes and regions, which is qualitatively consistent with the experimental observations. The deformation of GrFs is dominated by the flake bending rather than stretching, which is independent of the loading type, size, shape or thickness of flakes, as well as the density or stiffness of crosslinks. The great asymmetry of elasticity under tension and compression is induced by different mode of bond breaking. Furthermore, by evaluating the elastic energy density, we find that both thicker flakes and more crosslinks are two key factors responsible for good elasticity of GrFs. These results should be useful for understanding GrF elasticity and further design of advanced graphene-based materials. (C) 2019 Elsevier Ltd. All rights reserved