Molecular dynamics simulation and finite element analysis on mechanical behavior of oxygen functionalized graphene/polymer nanocomposites

The mechanical behavior of oxygen functionalized single layer graphene (graphene oxide, GO)/polyethylene (PE) nanocomposites is studied by all atom-based molecular dynamics (MD) simulation and finite element analysis (FEA). To account for the effect of the oxygen functional group, both pristine and 15 hydroxyl functionalized graphene embedded into the transversely isotropic nanocomposites unit cell models are considered. Using the classical ensemble simulations at 200K and at atmospheric pressure, the transversely isotropic elastic constants of the nanocomposites molecular unit cell structures are determined from uniaxial tension and shear tests. To evaluate the effect of the addressed oxygen functional groups on elastic constants of the nanocomposites, periodic FEA models with the perfect interface condition between the graphene and PP matrix are constructed. Due to the degradation of the graphene by the oxidation, the longitudinal Young’s modulus and the in-plane shear modulus of the nanocomposites determined from the MD simulation and FEA are found to be degraded by the oxygen functional groups. According to the MD simulation results, however, the longitudinal shear modulus of the nanocomposites is improved by the oxygen functional groups compared with the pristine graphene. On the other hand, FEA analysis of the longitudinal shear modulus is overestimated unless the oxygen functional group-dependent cohesive interface law between the graphene and PP matrix is addressed.