Elastic–plastic properties of graphene engineered by oxygen functional groups

Abstract

Using molecular dynamics (MD) simulations, we investigate the elastic–plastic mechanical performances of monolayer graphene oxide (GO) under uniaxial tension. The brittle–ductile–brittle transition and nonlinear–linear–nonlinear elastic transition is found in the uniaxial tension of GO, which displays strong correlations to the content, distribution and proportion of oxygen functional groups. In principle, the tensile behavior of graphene with epoxy groups exhibits ductile fracture features due to the unique epoxy-to-ether transformation in structural evolution. Our simulation results also reveal that wrinkling could cause a competing mechanism of strain-hardening or -softening, and in turn, the nonlinear–linear elasticity transition. Moreover, we propose a continuum mechanical model with a modified stress–strain relation to understand the unique deformation performances, which is consistent with the MD results. These findings might provide valuable insight and design guidelines for optimizing the specific mechanical properties and deformation behaviors of graphene and its derivatives.