双酚A型聚碳酸酯形变行为的MD模拟  

A molecular dynamics simulation of the plastic behavior of bis-phenol-A-polycarbonate

作　　者：刘建[1] 胡文军[2] 万强[2] 魏建萍[1] 赵晓平[1] 何铁宁[1] 

机构地区：[1]中国工程物理研究院计算机应用研究所 [2]中国工程物理研究院总体工程研究所

出　　处：《计算机与应用化学》2009年第7期845-848,共4页Computers and Applied Chemistry

基　　金：国家自然科学基金青年科学基金(10802081)

摘　　要：采用分子动力学方法(MD),计算了双酚A型聚碳酸酯的应力应/变关系、能量/应变关系。研究中采用了COMPASS力场和NPT系综。应力-应变曲线的研究结果显示,应变ε_(XX)≤0.05为"弹性区域",在这一区域,应力-应变有很好的线性关系。在ε_(XX)=0.14处出现"屈服点",经过"屈服点",在0.15<ε_(XX)<1.0的区域出现应力脉动,应变ε_(XX)>1.0后发生了应变硬化。能量-应力关系的研究结果显示,在应力-应变呈线性关系的"弹性区域",体系的总势能及各势能分量随应变增大发生不规则的波动,在"屈服点"附近,E_(tot)与E_(be)的变化均产生突跃性的局部高点,而E_(VW)在"屈服点"附近的变化刚好与前两者相反;当体系在经历"屈服区域"时,随着应变的增加,各能量项并不发生明显的变化;当体系处于"应变硬化"阶段时,E_(tot)、E_(be)和E_(be)会随着应变的增大而继续增大。在整个拉伸过程中,E_(to)均没有发生明显的变化。对拉伸过程的分子链快照进行分析发现,材料在ε_(XX)≤0.16时发生均匀的形变,并维持初始的链结构,同时伴随了一些空穴的生成,在ε_(XX)>0.6时,可以清楚地看到密度变得不均匀。在ε_(XX)>1.0的应变硬化的初始阶段,新的网络结构生成了,长的直链与缠绕链形成的团簇相连。Molecular dynamics simulation has been applied to study the behavior of a kind of polycarbonate （ PC）, bis-phenol-A-polycarbonate, in this paper. The stress-strain curve and the energy-strain curve have been educed by using COMPASS force field and NPT ensemble. The stress-strain curve shows a linear elastic relationship up to the strain of 0.05, and the yield point was εxx =0. 14 ,after the yield point, the curve becomes flat with little oscillation while the strain continues to increase until εxx = 1.0, while after εxx = 1.0 the strain hardening occurred. The energy-strain curve illustrates the change in the potential energy of the system. E,o, and its components were ruleless at the elastic stage. An obvious phenomenon can be seen at the yield point, that is Etot and Ebs, pass through a local climax and with sadden debase subsequently, while changes of EVW reverse to before-mentioned two energy items. All the energy items change slightly during the yield stage. Etot, Ebs and Ebe increasing with strain increased at the strain-hardening stage. The snapshots of molecular chains illustrated the material deforms homogeneously and maintains the initial chain structure until εxx= 0. 16, with few voids appeared. The homogeneity in the density becomes clearer when εxx = 0. 6. At he beginning of the strain hardening at εxx = 1.0, a new network structure is generated where long straightened chains connect the clusters of entangled chains.

关 键 词：聚碳酸酯 分子动力学 应力应变 

分 类 号：TQ015.9[化学工程] O6-39[理学—化学]