This work exploded the effect of silica nanoparticles on shock adiabatic relation and tensile fracture in polyurethane based on atomistic simulations. It is found that the non-uniform interface structures introduced by nanoparticles can increase the shock impedance, which also leading to increased twisting of polyurethane chains and the generation of local hotspots near the nanoparticles. The interface structures near the nanoparticle consists of polyurethane chains with a high gyration radius, and the average gyration radius increases approximately linearly with the increase in nanoparticle content. At lower shock velocity, the potential energy increment initially increases and then decreases with the increase in nanoparticle content. Bond analysis reveal that flexible segments dominate the bending and twisting deformations of polyurethane, while nanoparticles enhance the corresponding deformation degrees. Furthermore, nanoparticles can serve as void nucleation sites for early-stage tensile damage, resulting in a decrease in fracture strength. Differing from metals, the relationship between tensile strength and fracture temperature follows a more linear law. Nanoparticles inhibit the later growth and coalescence of voids by increasing the temperature and steric hindrance. The density and size distribution characteristics of voids are consistent with the changes in potential energy during the shock compression process. Unlike classical spallation, the curled polyurethane chains in the tensile region gradually orient along the shock direction, evolving into a void-fiber structure.

中文翻译：

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纳米二氧化硅对聚氨酯冲击绝热关系和拉伸强度的影响

这项工作基于原子模拟，揭示了二氧化硅纳米颗粒对聚氨酯冲击绝热关系和拉伸断裂的影响。研究发现，纳米颗粒引入的不均匀界面结构会增加冲击阻抗，这也会导致聚氨酯链的扭曲增加以及纳米颗粒附近局部热点的产生。纳米颗粒附近的界面结构由具有高回转半径的聚氨酯链组成，平均回转半径随着纳米颗粒含量的增加近似线性增加。在较低的冲击速度下，势能增量随着纳米颗粒含量的增加先增加然后减少。键合分析表明，柔性链段主导聚氨酯的弯曲和扭曲变形，而纳米颗粒增强了相应的变形程度。此外，纳米颗粒可以作为早期拉伸损伤的空隙成核位点，导致断裂强度降低。与金属不同，拉伸强度和断裂温度之间的关系遵循更线性的规律。纳米颗粒通过提高温度和空间位阻来抑制空隙的后期生长和聚结。孔隙的密度和尺寸分布特征与冲击压缩过程中势能的变化一致。与经典的散裂不同，拉伸区域中的卷曲聚氨酯链逐渐沿着冲击方向取向，演变成空隙纤维结构。