编织SiC（C）/SiC复合材料细观建模与热弹性常数预报

Mesoscopic Modeling and Thermal and Mechanical Constant Prediction of Braided SiC(C)/SiC Composites

关键词:  陶瓷基复合材料  细观模型  导热系数  弹性模量  数值仿真

Key words:  Ceramic matrix composites  Mesoscopic model  Thermal conductivity  Elastic modulus  Numerical simulation

摘要:

为了准确有效地评估陶瓷基复合材料的热力性能，本文基于真实的CT扫描图像，充分考虑不同编织结构的铺层结构与内部孔隙，建立了平纹机织C/SiC复合材料、平纹机织SiC/SiC复合材料以及2.5D编织SiC/SiC复合材料的二维细观模型。在此基础上构建有限元模型，计算材料等效弹性模量与等效导热系数，并与实验结果进行对比，验证了模型的正确性和有效性。并分析微观结构对应力集中区域与热流集中区域分布的影响规律。研究发现：孔隙的几何形状和分布对宏观热力性能影响显著，且三种材料截面中的应力集中区和热流集中区均与纬纱和经纱交织前后的区域有关；SiC纤维增强的材料弹性模量及导热性能均大于C纤维增强的材料，与平纹机织结构相比2.5D编织结构材料在厚度方向的模量和热导率更大。

Abstract:

In order to accurately and effectively evaluate the thermal and mechanical properties of ceramic matrix composites， two dimensional mesoscopic models of plain woven C/SiC composites， plain woven SiC/SiC composites and 2.5D SiC/SiC composites were established based on real CT scanning images， taking full account of the layering structure and internal pores of different braided structures. On this basis， the finite element model was constructed， and the equivalent elastic modulus and equivalent thermal conductivity were calculated. The correctness and effectiveness of the model were verified by comparing with the experimental results. The influence of microstructure on the distribution of stress concentration and heat flux concentration was analyzed. The results show that the pore geometry and distribution have a significant effect on the macroscopic thermal performance， and the stress concentration and heat flow concentration areas in the cross sections of the three materials are related to the areas before and after the weft and warp interweaving. The elasticity modulus and thermal conductivity of SiC fiber reinforced material are greater than that of C fiber reinforced material. Compared with plain woven structure， 2.5D composite has higher modulus and thermal conductivity in the thickness direction and greater performance.