纳米级石墨晶体的各向异性力学性能的计算

Numerical Simulation of Anisotropic Mechanical Properties of Nano-graphite Crystals

理想的石墨晶体是由碳原子以sp2杂化轨道和邻近的三个碳原子形成共价键,构成六角平面的网状层片结构,层片之间以Van derW aals力相结合.基于原子键合理论的力能关系基本原理:层片内以C—C键合单元相结合,层片间采用连续介质填充单元,建立石墨晶体的复合模型.其中C—C键合单元包括两个节点,每个节点包含三个自由度:ux,uy,uz.键合单元是该复合建模方法的主要部分.通过运算分析,确定了石墨晶体C—C键合单元的各个参数,该参数保证了石墨晶体正交各向异性的性质.同时,通过建立石墨晶体的拉伸、剪切等计算模型,并与实验数据相对比,验证了该石墨晶体复合建模方法的正确性,并将该复合模型用于研究石墨晶体的模态分析.该复合建模方法为研究石墨的微观结构、性能等提供了一种有效的数值模拟方法.

The C atom in ideal graphite crystals is hybridized in sp^2 orbital and forms covalent bonds with adjacent 3 other C atoms. The graphite crystals consist of stacks of parallel hexagonal net planar layers. These layers are integrated with Van der Waals attraction. Based on the principle of force-energy relationship of bonding theory, a combining modeling method composed of the C-C Bonding Element in graphite crystals layer and constitutive filling element between these layers has been built. The C-C Bonding Element has two nodes and each node has three freedoms：ux, uy, uz. The planar C-C Bonding Element is the main part of the combining modeling method. Parameters of planar C-C Bonding Element have been analyzed to guarantee the anisotropic properties of the graphite crystals. Comparison between experimental data and computation value in tension and shearing model of graphite crystals verifzses the correctness of combining modeling method. And this method has been applied to analyze modals of graphite crystals. It provides an effective numeric simulation approach to study the microstructure and micro-properties of graphite crystals and other materials.