【作者】 方光武； 高希光； 宋迎东；

【Author】 FANG Guangwu;GAO Xiguang;SONG Yingdong;School of Mechanical Engineering, Anhui University of Technology;Key Laboratory of Aero-engine Thermal Environment and Structure, Ministry of Industry and Information Tech-nology, Nanjing University of Aeronautics and Astronautics;

【机构】 安徽工业大学机械工程学院； 南京航空航天大学航空发动机热环境与热结构工信部重点实验室；

【摘要】 采用数值模拟方法研究了2.5D编织预制体对陶瓷基复合材料环境障碍涂层损伤机制的影响。基于代表体单元思想,建立了包含涂层的复合材料二维细观有限元模型。模型中采用三角函数描述2.5D编织预制体中经纱的走向。以2.5D编织SiC/SiC复合材料及Si/Mullite/Yb2Si O5涂层为研究对象,首先对涂层制备完成后的冷却过程进行了热力学模拟,然后分别模拟了不同氧化增长层厚度下涂层的热应力,通过对比分析了氧化增长层厚度对涂层损伤的影响机制。结果表明:对于所研究的涂层体系,冷却过程在EBCs的各层中引起了较大的热残余应力;编织结构对EBCs中的应力分布具有显著的影响,2.5D编织CMCs的经纱走向波动较大,使得涂层中应力沿着经纱的波动显著,波动幅度可以达到100MPa;氧化增长层中存在较大的面内应力,利于垂直裂纹的扩展,同时还存在沿厚度方向的应力,可以驱动分层裂纹的扩展。更多还原

【Abstract】 A numerical simulation was performed to study the effect of woven structure on the damage mechanism in the environmental barrier coatings for 2.5 D woven ceramic matrix composites. Based on the concept of representative volume elements, a micromechanical finite element model of the composites containing the coatings was established. The trigonometric function was used to describe the warp direction of 2.5 D woven preform. The presented method was applied to model a 2.5 D woven SiC/SiC composite with Si/Mullite/Yb2 Si O5 coatings. Firstly, the cooling process after preparation was simulated. Then, the thermal stress in coatings during the growth of thermal grown oxide(TGO) layer was simulated, and the influence mechanism of TGO on the failure of coatings was analyzed by comparison. The results show that the cooling process resulted in a large thermal residual stress in each layer of EBCs. The woven structure has a significant impact on the stress distribution in EBCs. The warp direction of 2.5 D woven CMCs fluctuates greatly, which makes the stress in the coating fluctuate significantly along the warp, and the fluctuation range can reach 100 MPa. Large in-plane stress was induced in the TGO layer. It is advantageous to the vertical crack growth. Stress along the thickness direction was also introduced, which can drive the growth of delamination crack.更多还原