极化收缩关联的氮化硼纤维多级界面载荷传递机制研究

纳米氮化硼组装的新型纤维在空天领域具有不可替代的应用前景，但还面临组装基元超强力学性能难以从微观向宏观有效拓展的困难。亚纳米-纳米-微米尺度的多级界面作为联系微观基元与宏观纤维的关键，揭示其载荷传递机制是应对当前困难的前提，其中的核心问题是厘清界面色散力与静电力的协作竞争关系，然而现有认知对此还尚未清晰。申请人近期工作发现，极化收缩显著影响氮化硼界面色散/静电作用的相对强度，将其与多级界面相关联为该核心问题的解决提供了可能。因此，本项目采用多尺度模拟结合理论模型分析的方法开展极化收缩关联的界面载荷传递研究：通过第一性原理计算修正现有分子动力学作用势参数，实现极化收缩在多级界面的关联；基于多级界面载荷传递过程的分子动力学模拟，构建色散力与静电力关系演化的物理图像并揭示其对界面载荷传递的作用机制；结合纤维力学模型分析，明确影响载荷传递的关键界面结构因素，为氮化硼纤维的深入发展奠定理论基础。

The novel fibers assembled with nano boron nitride (BN) materials have shown an irreplaceable application prospect in the field of aerospace, but still face the challenges of efficiently expanding the super mechanical properties from nano BN to the assembled fibers. Since the multilevel interfaces at subnano-nano-micro scales are the key structures to connect the BN materials and the fibers, it is of vital importance to reveal the mechanisms of load transfer at these interfaces for the performance optimizations of the fibers. Although the fundamental problem is clarifying the cooperative competition relationship between dispersion forces and electrostatic forces, current studies are still lacking full understandings of this relationship. The applicant recently found that the polarizability contraction (PC), which pronouncedly affects the relative strengths of dispersion and electrostatic forces, provides the possibilities of deepening the cognition of the mechanisms by solving the fundamental problem. Therefore, this project will study the load transfer at the multiscale interfaces by performing computational simulations and theoretical analyses with taking the PC into account. Models of various interfacial structures at the subnano scale will be constructed, followed by the PC corrected first principle calculations to reparameterize the current molecular dynamics potential for BN systems, making correlation between the PC and interfaces at nano and micro scales. Based on the dynamic process simulations of load transfer at the multilevel interfaces in BN fibers, the physical images and corresponding mechanisms of the load transfer will be constructed and revealed by disentangling dispersion and electrostatic forces during the load transfer. Combined with the theoretical mechanical models of the assembled fibers, the interfacial factors, which dramatically influences the load transfer, will then be identified. The project will provide solid theoretical principles for optimizing the performance of BN fibers to promote their developments.