Molecular dynamics simulation based size and rate dependent constitutive model of polystyrene thin films
Molecular dynamics simulation based size and rate dependent constitutive model of polystyrene thin films
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基于聚苯乙烯薄膜尺寸和速率依赖本构模型的分子动力学模拟
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发表时间：
2012
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影响因子：
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通讯作者：
L. J. Lee
中科院分区：
文献类型：
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作者：
Fan Yang;Somnath Ghosh;L. J. Lee
在与能量产生、传输和存储相关的各种应用中，与速率和尺寸相关的性质主导着聚合物薄膜的力学行为。本文采用分子动力学(MD)方法对聚苯乙烯薄膜进行了模拟，建立了与尺寸和速率相关的有限变形弹塑性本构关系。在MD模型中考虑了不同的变形模式，并将模拟结果均化以产生本构模型的参数表示。对于不同厚度、不同应变率的薄膜，用改进的Ogden模型描述了其超弹性行为。分子动力学模拟表明屈服强度与速率有关，这是为一个完全塑性模型建立的，尺寸效应得到了缓解。薄膜的材料性能较软是由于具有较大的表面层，该表面层具有低密度和高局部链迁移率。
Rate and size-dependent properties dominate the mechanical behavior of polymeric thin films used in a variety of applications related to generation, transmission and storage of energy. In this paper, molecular dynamics (MD) simulations of polystyrene thin films are used to develop a size and rate dependent finite deformation elastic–plastic constitutive relations. Different modes of deformation are considered in the MD model, and results of simulations are homogenized to yield parametric representations of the constitutive model. The hyperelastic behavior is represented by a modified Ogden type model for films of different thicknesses at different strain rates. The MD simulations suggesting a rate-dependent yield strength is developed for a perfect plasticity model with mitigated size effects. The softer material properties of thin films are found to be the consequence of a large surface layer, which has a low density with high local chain mobility.