力-热复杂荷载下2D-C/SiC复合材料结构的多尺度损伤机理研究

The application conditions for ceramic matrix composites involve thermo-mechanical coupling. However, the failure mechanisms and strength theory under complex stress were rarely studied especially at high temperatures. This has seriously restricted the design and application of heat-resisting structures in aerospace field. In this project, the multiscale damage mechanisms and bearing capacity of 2D-C/SiC composite structures under complex loading at high temperature would be investigated. The thermo-mechanical coupled complex loading experiment will be conducted on typical 2D-C/SiC composite structures. The macro- and micro-scopic damage evolutions, failure mechanisms and bearing capacity of the specimens will be studied. Meanwhile, the interaction mechanism of the micro-damages and its influence upon macroscopic mechanical properties will be demonstrated. Based on the damage mechanisms, strength failure criterion and interlaminar debonding criterion would be established in order to overcome the drawbacks of the classical failure criteria, which fail to incorporate the damage types, process and mechanisms of composite materials. By the newly proposed criterion, progressive damage simulation upon 2D-C/SiC composite structures under complex thermo-mechanical loading will be performed. Predictive methodology and model for structural property will be developed. Furthermore, evolvement mechanism of the rupture strength with temperature and loading path will be illuminated. Through the studies in this project, representation theory and methodology for damage and failure of nonlinear composites are expected to be developed in order to facilitate the use of material bearing potential, to promote the strength design of ceramic matrix composite hot structures and to make social and military benefits obviously.

陶瓷基复合材料的服役工况涉及力-热耦合。高温复杂应力下，陶瓷基复合材料的损伤机理及强度理论研究不够，严重制约了其在航空航天耐热结构中的应用。本项目拟开展2D-C/SiC复合材料结构在高温复杂荷载下的多尺度损伤机理与承载性能研究。针对典型2D-C/SiC复合材料结构，开展力-热复杂加载试验，研究宏细观损伤演化机理、破坏机制与承载性能，阐明细观损伤的耦合机制及其对宏观性能的影响。提出基于细观损伤机理的强度失效准则和层间开裂准则，弥补传统失效判据在表征复合材料损伤形式、过程和机理方面的不足。应用新准则，开展复杂加载下2D-C/SiC复合材料结构的渐进损伤模拟，提出承载性能的预测模型和方法，阐明破坏强度随温度及加载方式的演变机理。通过本项目的研究，有望进一步发展非线性复合材料损伤、失效的表征理论和方法，促进材料承载潜力的发挥，提升陶瓷基复合材料热结构的强度设计能力，取得一定的社会与军事效益。

陶瓷基复合材料的热结构设计缺乏符合实际的本构关系，且在三维宏观应力状态下，其损伤破坏机理及强度理论的研究不够，严重制约了其在航空航天领域的应用。本项目针对2D-C/SiC复合材料的多轴加载性能开展了理论和模型研究。在细观尺度上，表征了微裂纹的几何参数随应力、温度和氧化的演变行为，揭示了各向异性细观损伤的耦合机理及其对力学响应的影响规律。在宏观尺度上，提出了预测陶瓷基复合材料氧化残余性能的模型和方法，准确预测了预加载2D-C/SiC复合材料的氧化剩余拉伸性能；基于声发射技术和刚度衰减描述了材料的各向异性损伤演化规律；研究了典型梁结构在组合加载下的损伤失效特性。在理论层面，基于损伤耦合机理构建了材料的热力耦合各向异性本构模型和强度失效判据，并编制UMAT子程序实现了对典型结构件承载性能的分析预测，提出了材料-结构跨尺度性能关联的模型和方法。基于微细观损伤机理和损伤耦合机制，提出了多应力作用下的疲劳失效准则和寿命预测方法，并初步得到试验验证。项目的研究成果，进一步丰富和发展了易损复合材料损伤-破坏的表征理论和方法，为发掘陶瓷基复合材料的承载潜力、提升热结构的刚度强度设计水平提供了基本的理论、模型和方法。在项目执行期间，共发表期刊论文7篇，参加学术会议4次，有4篇论文被会议录用；协助培养研究生4人，招收研究生1人；课题组在项目执行期间还获批国家自然科学基金面上项目1项。