热/力/氧环境下SiCf/SiC复合材料裂纹竞争机理研究

The excellent performance of high temperature, oxidation and fatigue resistance makes SiCf/SiC possess a wide application in many fields such as aero-engine. SiCf/SiC microstructure cracks of fiber, matrix, interphase and double interfaces(Fiber/Interphase and Matrix/Interphase) interplay and compete. The microscale failure mechanism needs to be clarified. And the effective microscale and multiscale numerical modelling methods need to be developed. This project will focus on revealing the microstructure cracks competition mechanism of SiCf/SiC under thermal/mechanical/oxydic environment by means of the room and elevated temperature contrast experiment and numerical modeling methods. Fiber, matrix and interphase cracking initiation and propagation are described by linear elastic fracture theory. Double interfaces debonding are described by damage mechanics. The high temperature wet-oxidation accelerating factor is introduced into the XFEM-CZM micro-X numerical model, which is built to predict SiCf/SiC real failure behavior. On this basis, the multiscale virtual simulation method will be formed by correlating the micro, meso and macro model. The project can provide theoretical basis and scientific method for the accurate design on material components and microstructures.

SiCf/SiC复合材料耐高温、抗氧化、抗疲劳性能使其在航空发动机等领域具有广阔的应用前景。高温、循环机械载荷与湿氧化环境下，SiCf/SiC纤维、基体、界面相和双界面（纤维/界面相与基体/界面相）微结构裂纹相互影响与竞争，其微观失效机理尚待厘清，有效的微观与多尺度数值模拟方法也亟待发展。本项目拟通过常、高温对比实验与数值模拟揭示热/力/氧环境下SiCf/SiC的微结构裂纹竞争机理。基于线弹性断裂理论描述纤维、基体和界面相内部裂纹的起始与扩展，利用损伤力学描述双界面的脱粘，继而引入高温湿氧化加速因子，建立可预测SiCf/SiC真实失效行为的XFEM-CZM微观交叉数值模型。在此基础上，关联微观、细观与宏观模型，形成多尺度虚拟仿真方法。本项目可为SiCf/SiC材料组分及微结构的精准设计提供理论依据与科学方法。

本项目以CVI工艺BN界面SiCf/SiC二维编织复合材料和PyC界面C/SiC二维编织复合材料分别为研究对象，聚焦航空发动机涡轮叶片、燃烧室衬套等热端部件的工作环境，通过理论、数值和实验方法进行系统研究，从微观尺度研究高温-机械载荷-氧化复杂环境对CMCs失效机理和力学性能的影响。进行了常温试验，并以高温氧化力学真实环境实验揭示热/力/氧环境下SiCf/BN/SiC复合材料微裂纹竞争机理，进行了μCT和SEM的微观观察分析。改进了含界面、界面相、基体相裂纹的热应力解析模型，形成了改进的热应力解析模型。建立了基于XFEM与CZM交叉破坏理论的微观数值模型，补充了裂纹偏转判据理论。发展了宏-细-微观多尺度模型的虚拟仿真方法，支撑SiCf/BN/SiC复合材料的破坏分析、结构承载及寿命预报，为材料组分、微结构的精准设计提供科学依据和仿真手段，为SiCf/BN/SiC复合材料在航空航天等领域热端部件的进一步应用提供理论依据和科学方法。