针刺C/SiC复合材料拉-压疲劳特性与失效机理

Tension-compression Fatigue Behavior and Failure Mechanism of Needled C/SiC Composite

研究了室温下针刺C/SiC复合材料的拉-压疲劳特性,并与其拉-拉疲劳特性进行了对比。结果表明:针刺C/SiC复合材料的拉-压疲劳强度略低于拉-拉疲劳强度;两种循环载荷下都存在迟滞现象,随着循环数的增大迟滞环不断右移,且偏斜程度和包围面积不断增大。采用扫描电子显微镜对失效试件的断口形貌和微观结构的观察表明:除了垂直于加载方向的基体开裂以及界面脱粘,拉-压循环加载下的细观失效机制还包括平行于加载方向的基体开裂以及层间的开裂。这些平行于加载方向的损伤使得纤维受力状态恶化,最终削弱了针刺C/SiC复合材料拉-压疲劳强度。

T h e tension-compression fatigue behavior for needled C/SiC composite at room temperaturewas studied and compared with the properties under tension-tension fatigue loading.T h e results showthat the tension-compression fatigue strength of the needled C/SiC composites is slightly lower thanthat under tension-tension loading.Hysteresis phenomenon can be observed under both loading stations.T h e loops move to the right and their slopes and areas increase as the cycles increase.T h e microstructureof the composites and the morphology of the fractured surfaces of the failure specimenscan be observed by SEM.It shows that in addition to the matrix cracking and interface debonding,which is vertical to the loading direction,the meso failure mechanism under tension-compression cyclicloading also includes matrix cracking and interlayer delamination parallel to loading direction,whichcan make the stress state within fibers worse and finally weakens the fatigue strength of needled C/SiCcomposites under tension-compression loading.