Contribution of oxygen functional groups in graphene to the mechanical and interfacial behaviour of nanocomposites: Molecular dynamics and micromechanics study

•Epoxide and hydroxyl groups degrade mechanical properties of single-layer graphene.•Oxygen functional groups enhance surface roughness to boost interfacial shear load transfer between graphene and polymer matrix in composites.•Local evolution of the shear stress in matrix and oxygen functionalized graphene is sensitively affected by the oxygen functional groups.•Interfacial compliance for the equivalent continuum modelling of nanocomposites varies according to the oxygen functionalization of embedded graphene.•The transverse Young's modulus and longitudinal shear modulus of graphene were conjectured to be as large as the longitudinal Young's modulus and in-plane shear modulus. Based on the results of molecular dynamics (MD) simulations and a mean-field micromechanics model, we report on some positive contributions of the oxygen functional groups in single-layer graphene oxide (GO) to the mechanical and interfacial properties of polyethylene (PE)/graphene nanocomposites. As the epoxide and hydroxyl group degrade the mechanical properties of single-layer graphene, clear degradations in the longitudinal Young's and in-plane shear moduli are observed when the deformation of graphene is involved in the loading of the nanocomposite unit cells. However, a significant improvement in the longitudinal shear modulus of nanocomposites is predicted. By comparing the MD simulation results with double-inclusion (D-I) model predictions, contributions of the interphase zone and the interfacial stiffening effect to the elasticity of nanocomposites are again confirmed. Finally, we demonstrate a novel evolution of the out-of-plane normal stress and longitudinal shear stress in single-layer GO arising from its interaction with the surrounding PE matrix via atomic virial stress. [Display omitted]