Minimum grain size and compression mechanical behavior of polycrystalline graphene based carbon honeycombs: cell irregularity and grain size effect

Abstract The graphene-based carbon honeycombs (CHCs) possess excellent mechanical properties and various application, and attract intensive attention recently. However, the real CHCs in experiments have random cell shapes. The effects of polycrystalline and cell irregularity on the mechanical properties of CHCs are still unknow. Here, first, we investigated the minimum cell size stability with ideal cell wall in the polycrystalline graphene-based carbon honeycombs (PGCHs). Then, based on molecular dynamic simulations, the compression mechanical properties of four typical cell irregularity PGCHs are studied systematically, including the periodic regular graphene-based carbon honeycombs (RGCHs) with a zero-degree cell irregularity. Under in-plane compression, the Young’s modulus, initial peak stress, mean plateau stress, and per volume energy absorption W v of RGCHs and PGCHs decrease significantly with the increasing of the grain size, and show a pseudo Hall-Petch relation. The mean plateau stress and W v of PGCHs are higher than those of RGCHs. Under out-of-plane compression, grain size effect is also obviously. However, the influence of cell irregularity is very small and can be ignored. The results indicate that the Hall-Petch relations of polycrystalline material are dependent on both grain size and cell irregularity, and provide a theoretical guidance for real CHCs in engineering application.