2D-SiC/SiC复合材料损伤耦合力学行为

Damage coupling mechanical behaviors of 2D-SiC/SiC composite

基于轴向和45°偏轴加载实验,分别获得2D-SiC/SiC复合材料在单一轴向应力和复合应力状态下纤维束轴向方向上的拉伸、压缩和面内剪切应力-应变行为,计算分析材料在复合应力状态下的损伤耦合力学行为。结果表明,在45°偏轴拉伸和压缩复合应力状态下材料损伤耦合力学行为的起始应力分别约为40MPa和-100MPa。复合应力状态下材料纤维束轴向方向上的拉伸损伤和面内剪切损伤进程间具有相互促进作用,面内剪切损伤对压缩损伤进程具有促进作用,但是压缩应力分量对面内剪切损伤进程具有明显的抑制作用;上述损伤耦合作用随着应力水平的增加而越发显著。由试件断口电镜扫描结果可知,复合应力状态下材料纤维束轴向方向上3个应力分量对材料内部0°/90°和45°3种取向基体裂纹开裂损伤进程的影响作用,是2D-SiC/SiC复合材料产生损伤耦合力学行为的主要细观损伤机制。

By using axial and off-axis loading tests with off-axis angle as 45°,the tensile,compressive and in-plane shear stress-strain behaviors along the fiber bundles directions of a 2D-SiC/SiC composite were obtained,and the damage coupling mechanical behaviors of composite under combined stress condition were studied.The results show that the initial stress levels for the damage coupling mechanical behaviors of composite under 45°off-axis tensile and compressive loading conditions are 40MPa and-110MPa,separately.Under combined stress conditions,there exists obvious mutual acceleration between the tensile and the in-plane shear damage evolutions in the fibre bundles directions of composite,and the in-plane shear damage has accelerative effect on the compressive damage evolution,but the in-plane shear damage evolution is suppressed by compressive stress components obviously.These coupling effects become more significant with increasing stress level.The SEM(scanning electron microscope)pictures of fractured surfaces on off-axis loading specimens indicate that,in the fiber bundles directions,the mutual effects between the three stress components and the cracking evolutions of the three kinds of matrix cracks(oriented at 0°,90°and 45°)are the main micro-damage mechanisms for the damage coupling mechanical behaviors of 2D-SiC/SiC composite under combined stress conditions.