Abstract: The phenomenon that interphase of graphene nanocomposites has non-uniform distribution of material properties in the thickness direction has been confirmed by many studies. However, in those studies, interphase with changing properties is either equivalent to a homogeneous layer or segmental assigned in thickness direction. None of those methods can achieve good calculation accuracy and efficiency. In order to deal with this problem, a two-node isoparametric gradient finite element that can simulate interphase with any kinds of material distribution is proposed in this paper. An embedded represented volume element (RVE) model of graphene nanocomposite is established by finite element method to study the mechanical properties of graphene nanocomposite, under the assumption that the monolayer graphene was uniformly distributed in the matrix without agglomeration. To simplify the calculation, graphene and matrix are considered as isotropic materials, and simulated by plate element and solid element, respectively. The interphase layer is simulated by the presented two-node isoparametric gradient finite element. The effect of graphene fraction V^g_fr, the thickness t_in of interphase layer and the debondded condition between graphene and matrix on the overall mechanical properties of nanocomposites are discussed. The results show that, in case of V^g_fr=3.0%, the increase of t_in from 0.17 nm to 1.02 nm will lead to a deviation of 17.4% with the prediction result of Young′s modulus E_cx of the composite material.In the discussion of the debonding condition between graphene and matrix, it was found that E_cx decreased significantly when the edge of graphene was debondded, and the modulus decreased by about 10% when the debonding edge area was 1/6 of the total area.

Key words: graphene, nanocomposite, interphase, mechanical properties, finite element method