Theoretical study on uniaxial compressive mechanical properties of three-dimensional graphene

Combining molecular dynamics (MD) simulations and continuum modeling, the uniaxial in-plane compressive properties of honeycomb three-dimensional (h3D), triangle-like 3D (t3D) and non-equilateral hexagon 3D (nh3D) graphene are investigated to elucidate configuration-property relationships, and the constitutive relations of three kinds of 3D graphene are derived to evaluate the compressive mechanical properties. Based on theoretical and MD simulation results, it is found that the compressive stress-strain responses of 3D graphene can be divided into five stages. The compressive mechanical properties and deformation mechanisms of each stage are different. When 3D graphene is compressed, graphene sidewalls undergo rotations, bending and buckling deformations, collapses. Because graphene sidewalls of h3D graphene are prone to undergo buckling deformations, there is large locking strain in h3D graphene. For t3D and nh3D graphene, their high plateau stress is attributed to unique configurations. Moreover, we also find that with increasing graphene sidewall width, Young's modulus and plateau stress of 3D graphene gradually decrease. In addition to the above investigations, the energy absorption mechanisms and compression-unloading stress-strain curves of 3D graphene are also studied. It is found that there are extraordinary compression-recovery properties and energy absorption capacities in 3D graphene. Finally, the selection criteria of 3D graphene are proposed.