We modeled poly(p-phenylene terephthalamide) (PPTA) fibers in realistic size and structure and used Molecular Dynamics (MD) simulations with the ReaxFF reactive force field to investigate response to tensile deformation at extreme values. We constructed PPTA fibers in three forms: fully crystalline, fully unordered and core-shell structured with core and shell regions consisting of unordered and crystalline chains. The tensile deformation applied quasi-statically up to 15% strain. We calculated the average tensile modulus of fully unordered and crystalline fibers as 192 GPa and 289 GPa, indicating that crystallinity significantly increases this modulus. We introduced defects in the form of nitrogen vacancies with densities up to 5% and formulated an empirical equation to predict tensile modulus of the fiber based on defect density and crystallinity of the fiber. During the simulation, we observed domains in the crystalline region of fibers and failure of fibers started with breaking of chains located at these domain boundaries. As such, in this paper we present the first realistic-scale fully reactive molecular dynamics simulations of structure and failure in high performance fibers.

我们对poly（p-实际尺寸和结构的聚对苯二甲酰对苯二胺（PPTA）纤维，并结合ReaxFF反应力场使用了分子动力学（MD）模拟，以研究极限值下对拉伸变形的响应。我们以三种形式构造PPTA纤维：完全结晶，完全无序和核-壳结构，其芯和壳区域由无序和结晶链组成。拉伸变形准静态施加至15％的应变。我们计算出完全无序和结晶纤维的平均拉伸模量分别为192 GPa和289 GPa，表明结晶度显着提高了该模量。我们以密度高达5％的氮空位形式引入了缺陷，并建立了一个经验方程式，以基于纤维的缺陷密度和结晶度来预测纤维的拉伸模量。在模拟过程中，我们观察到了纤维晶体区域中的区域，而纤维的破坏则始于位于这些区域边界处的链断裂。因此，在本文中，我们介绍了高性能纤维中结构和破坏的第一个现实规模的完全反应性分子动力学模拟。