Cf/SiC复合材料的跨尺度模拟与微结构和性能调控

Continuous carbon fiber reinforced ceramic matrix composites (Cf/SiC) have great potential in the field of aerospace and defense. Because Cf/SiC composites have multi-level and multi-scale structures, simulation methods on this field still stay at the exploration stage. Microstructure details about the grain nucleation, grain growth and grain competition during the complex process have rarely been simulated, the influence of complex porous structures on these details has not been qualified. Considering this situation, this project focus on Cf/SiC composites fabricated by chemical vapor infiltration process (CVI). The research will develop a multi-scale simulation method based on molecular random walks, kinetic Monte Carlo, finite element method and others. We want to realize the optimization and design of microstructures by virtual manufacture and performance prediction through multi-scale simulations. At the same time, the simulation results will be verified by the samples prepared in laboratory and the simulation method will be improved according the verification results. The investigation will provide a new design method and technical reserves for high temperature structural composites.

连续碳纤维增强的陶瓷基复合材料（Cf/SiC）在航空航天和国防领域有巨大的应用潜力。但Cf/SiC具有多层次、多尺度的复杂结构，目前该领域的跨尺度计算模拟方法还处于探索阶段，鲜有在此复杂制备条件下模拟出晶粒形核、生长、竞争等微结构细节的成功例子，更未明确复杂多孔结构对这些细节的影响。本项目以高温结构复合材料为应用背景，选择化学气相渗透（CVI）制备的Cf/SiC体系为研究对象，基于分子随机游走、动力学蒙特卡罗和跨尺度有限元等计算方法，实现Cf/SiC微结构从虚拟制造到性能预测的跨尺度优化设计，揭示工艺因素对Cf/SiC微结构和性能的影响机制及调控方法，得到对制备性能优异Cf/SiC材料具有指导意义的工艺参数，并通过实验制备出的试样验证和改进模拟方法，为发展高温结构复合材料提供新的设计方法与制造技术储备。

本项目基于三氯甲基硅烷（MTS）和H2体系下，使用CFD模型结合提出的详细的气体和表面动力学机理进行CVD-SiC沉积模拟；建立了Si-B-C体系化学气相模型，实现耦合传热、传质和反应的反应器尺度/原子尺度材料生长模拟，采用跨尺度方法研究了（111）和（100）取向CVD-SiC薄膜；基于纤维预制体的多尺度结构特点，研究跨尺度CVI 数值模拟方法。实现多种复合材料的CVI致密化模拟。以BCl3/CH4/H2沉积碳化硼为研究对象，采用CFD建模结合机器学习预测碳化硼的沉积组分B/C。综合微缺陷及微结构信息和纤维排布、界面层等细观结构信息，利用跨尺度有限元方法预测Cf/SiC 多种性能：弹性常数、残余应力、基体开裂应力和抗氧化能力，建立从细观层次细化到微结构层次的CMC“构效”模型。确立了多孔陶瓷基体微结构传热/力学性能控制因素。采用有限元方法和内聚力模型研究陶瓷断裂失效的过程并且重新验证Orowan-Petch关系在晶粒尺寸从亚微米尺度向纳米尺度转变过程中的适用性；进行SiC/BN界面第一性原理模拟，预测了界面的黏附功、界面能、断裂韧性和拉伸强度。