平纹编织C/SiC复合材料在室温和高温环境下的拉伸行为

通过单向拉伸试验,对比研究平纹编织C/SiC陶瓷基复合材料在室温和高温(1300℃,包括惰性气氛和湿氧气氛)环境下的宏观力学特性,并采用光学显微镜和扫描电镜对试件断口进行显微观察,分析其损伤模式和破坏机理。结果表明:C/SiC复合材料的室温和高温拉伸行为通常表现为非线性特征,在低应力时就开始出现损伤;纤维与基体之间界面滑行阻力的降低使C/SiC复合材料在高温惰性气氛环境下的拉伸强度和破坏应变均比室温下的高;碳纤维的氧化严重影响材料的承载能力导致高温湿氧环境下的拉伸强度和破坏应变均比室温下的低;C/SiC复合材料室温和高温下的拉伸均呈现韧性断裂,断口较为相似,只是纤维拔出长度和断口的平齐程度有所不同,其中高温惰性气氛环境下纤维拔出最长,高温湿氧环境下试件断口有明显的被氧化痕迹;0°纤维束表面基体开裂、明显的层间分层以及0°纤维和纤维束的拔出和断裂同时携带90°纤维束拔出是C/SiC复合材料在室温和高温下的拉伸破坏机理。

Comparison of Tensile Behavior of Plain-Woven Carbon/Silicon Carbide Composites at Room Temperature and High Temperature

Monotonic tensile experiments at room temperature and 1300℃ were performed to investigate the macro-mechanical behavior of plain-woven C/SiC ceramic matrix composites(CMCs) produced with CVI technique.Two environments including inert atmosphere and wet oxygen atmosphere were simulated at 1300℃.The microstructure of specimens were observed by optical microscope and scanning electron microscope to analyse its damage mechanism.The results indicate that, the responses of C/SiC composite under tensile loading at both room temperature and 1300℃ are nonlinear to rupture and damage appears at very low stress level. The tensile strength and failure strain at room temperature are lower than at 1300℃ in inert atmosphere but higher than at 1300℃ in wet oxygen atmosphere, respectively.The main reason of the former is the decrease of interfacial sliding resistance at 1300℃ in inert atmosphere.The main reason of the latter is fiber oxidation at 1300℃ in wet oxygen atmosphere. The tensile specimens all break in a ductile manner. Fractography analysis shows that the fracture surfaces are almost the same in the three environments except the obviously oxidative trace in wet oxygen atmosphere .The specimens in inert atmosphere have the longest pull-out length of fiber. Matrix cracks around the 0° fiber bundles, interlaminar cracks , fracture and pullout of 0° fiber and 0° bundles along with the pullout of 90°bundles are the main damage mechanisms.