编织C/C复合材料复杂应力状态下力学性能劣化特性与机理研究

As a critical type of thermal protective structural materials, C/C composites mainly serve in the extreme heat physical chemistry and complex stress conditions. Unlike other advanced composite materials, mechanical properties of the woven C/C are very sensitive to stress state and show significant deterioration (or enhancement) of characteristics and diverse failure modes, which seriously affect the potential of C/C materials to play and its rational applications in engineering. This project starts from the micro/meso structural characteristics of woven C/C composites to build the high fidelity of material mechanical analysis model with introduction of non-uniform, random microstructure, and further to predict numerically the mechanical properties and failure modes of C/C materials under different stress states. The project develops testing technology under complex stress state, builds "inversion" identification methods of material mechanical properties under complex stress state, and achieves experimental research of woven C/C material mechanical behavior under different stress states; Also, the project gives material strength, stiffness and other performance parameters deteriorated law and the evolution from the coupling stress using the combination of physical tests and numerical simulation, and reveals the failure mechanism of the woven C/C materials under complex stress state from micro/meso level. This study aims to establish a reliable mechanical performance testing and evaluation methods of C/C material to lay the theoretical foundation and further to improve the design and analysis level of woven composites of our country.

C/C复合材料作为非常关键的一类防热结构材料，主要服役于极端热物理化学和复杂应力环境。不同于其它先进复合材料，编织C/C材料力学性能对应力状态非常敏感，在不同应力状态下表现出显著劣化（或强化）特性和多样失效模式，严重影响C/C材料潜力的发挥和工程中合理应用。本项目从编织C/C复合材料的微/细观结构特征出发，建立引入非均匀、随机微结构的高保真度的材料力学分析模型，数值预报编织C/C材料不同应力状态下力学性能和失效模式。发展复杂应力状态试验技术，建立复杂应力状态材料力学性能参量 "反演"辨识方法，完成不同应力状态编织C/C材料力学行为试验研究；物理试验与数值仿真相结合给出应力耦合引起的材料强度、刚度等性能参量劣化规律及损伤演化规律，从微/细观层次揭示编织C/C材料复杂应力状态下的失效机理。本研究旨在为建立可靠的C/C材料力学性能测试与评价方法奠定理论基础，提高我国编织复合材料的设计与分析水平。

本项目以编织C/C复合材料为研究对象，基于Micro-CT无损检测手段及数理统计方法实现C/C复合材料典型微结构特征的原位观测与定量表征，建立了引入实际微结构特征的C/C复合材料高保真度的微/细观力学分析模型，实现双轴组合应力状态2D C/C编织复合材料的力学性能参量、失效模式预报，单轴及双轴拉伸强度预报值与试验值误差小于10%。基于材料双轴力学试验机发展了双轴载荷、Arcan圆盘和Iosipescu等组合载荷状态试验技术，建立了纤维增强复合材料双轴组合载荷状态试验方法，实现不同载荷形式（双轴拉-拉、拉-压、压-压、压-剪和拉-剪）、任意载荷比例和程控加载路径状态材料力学性能测试能力。数字图像相关应变场测试技术与有限元数值仿真方法结合，建立各向异性复合材料力学性能“反演”识别框架，利用ABAQUS和Isight等软件系统搭建优化更新平台，建立了极端环境各向异性材料力学性能参量辨识方法，实现室温~1800℃真空或惰性气氛环境下复合材料力学性能参量测量与反演辨识能力。系统研究了2D C/C编织复合材料在双轴拉/拉、压/压、拉/压、拉/剪和压/剪等组合应力状态下的力学行为，积累了该类材料力学性能数据，获得了该类材料力学性能随应力状态的劣化规律与多模式损伤演化规律，揭示了编织C/C复合材料在耦合应力状态下的失效机理。