粘结界面层属性对石墨烯纳米复合材料力学性能影响的有限元分析

FINITE ELEMENT ANALYSIS OF THE INFLUENCE OF INTERPHASE PROPERTIES ON THE MECHANICAL PROPERTIES OF GRAPHENE NANOCOMPOSITE

针对石墨烯纳米复合材料粘结界面层材料属性非均匀分布这一现象,本文推导出可以模拟任意函数分布的空间两节点等参梯度单元。假设单层石墨烯在基体内均匀分布且无团聚现象,建立石墨烯纳米复合材料的嵌入式代表体积单元(Representative Volume Element,简称"RVE")有限元模型,对石墨烯纳米复合材料力学性能进行预测。本文讨论了石墨烯体积含量Vfrg、粘结界面层的厚度tin和脱粘情况对纳米复合材料整体力学性能的影响。模拟结果显示,在石墨烯含量Vfrg=3. 0%时,模型中tin的取值由0. 17 nm增大到1. 02 nm会使复合材料杨氏模量Ecx的预测结果偏差17. 4%。在对石墨烯与基体粘结情况讨论中发现,石墨烯边缘脱粘使Ecx下降明显,脱粘的边缘面积为总面积的1/6时,模量降低约10%。

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 Vfrg,the thickness tin 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 Vfrg= 3. 0%,the increase of tin from 0. 17 nm to 1. 02 nm will lead to a deviation of 17.4% with the prediction result of Young’s modulus Ecx of the composite material. In the discussion of the debonding condition between graphene and matrix,it was found that Ecx 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.