弹性体纳米复合材料断裂机制的分子动力学模拟研究

It is well known that the fracture strength is one of the most important properties for the nanofiller filled elastomer nanocomposites. Thus, to uncover the fracture mechanism, the most important scientific issue is to quantitatively characterize the relationship between the macroscopic stress and microscopic structure during the tensile process. In this project, based on molecular dynamics simulation, it can realize the multiscale simulation by coupling atomic and coarse-grained molecular dynamics simulation in big systems when adopting the Iterative Boltzmann Inversion and geometry optimization. After building the reliable simulation systems, the elastomer nanocomposites are under the uniaxial deformation until to the fracture. We uncover the fracture mechanism by characterizing the evolution process of the microstructure, such as the number, size, distribution, initiation of the voids, local modules and density, polymer-nanofiller network, kinetic anisotropic, nonaffine deformation behavior of chains near the crack. Meanwhile, we investigate the effect of the shape, size, volume fraction of nanofiller, polymer-nanofiller interaction, grafting density and grafting length, and chain length on the evolution of the microstructure under the deformation. Last, we intend to find out the most important factors which determine the fracture strength of nanocomposites. This project can contribute to uncover the fracture mechanism of the elastomer nanocomposites and provide the scientific basis for improving the rupture property by experimental modification and optimization.

断裂性能是弹性体纳米复合材料重要的性能之一。为了揭示材料断裂机理，重要的科学问题是定量表征材料断裂过程中微观结构与宏观应力的对应关系。本项目基于分子动力学模拟方法，首先结合反转迭代玻尔兹曼方法与几何优化方法耦合全原子与粗粒度模型，实现大体系下的跨尺度模拟。在建立可靠的模拟体系之后，对材料进行单轴拉伸直至发生断裂破坏。然后从表征裂纹萌生与扩展，以及其他微观结构(局部模量与密度，聚合物填料网络，动力学各向异性，裂纹附近分子链非仿射变形行为)的演变过程来揭示材料断裂机理。同时明晰填料形状、尺寸、体积分数，聚合物填料界面相互作用，填料接枝分子链长度、密度与分子链链长对材料微观结构演变的影响，找出影响材料断裂强度的关键因素。该研究有助于揭示材料断裂机理，同时为改性优化实验方法来提高弹性体基纳米复合材料断裂性能提供科学依据。

断裂性能是弹性体纳米复合材料重要的性能之一。为了揭示材料断裂机理，重要的科学问题是定量表征材料断裂过程中微观结构与宏观应力的对应关系。本项目基于分子动力学模拟方法，首先结合反转迭代玻尔兹曼方法与几何优化方法耦合全原子与粗粒度模型，实现大体系下的跨尺度模拟。在建立可靠的模拟体系之后，对材料进行单轴拉伸直至发生断裂破坏。然后从表征裂纹萌生与扩展，以及其他微观结构(局部模量与密度，聚合物填料网络，动力学各向异性，裂纹附近分子链非仿射变形行为)的演变过程来揭示材料断裂机理。同时明晰填料形状、尺寸、体积分数，聚合物填料界面相互作用，填料接枝分子链长度、密度与分子链链长对材料微观结构演变的影响，找出影响材料断裂强度的关键因素。该研究有助于揭示材料断裂机理，同时为改性优化实验方法来提高弹性体基纳米复合材料断裂性能提供科学依据。