3D-C/SiC复合材料拉伸蠕变损伤和蠕变机理

Tensile Creep Damage and Creep Mechanism of 3D-C/SiC Composite

对3D-C/SiC复合材料进行拉伸蠕变试验,蠕变进行一段时间后,用扫描电子显微镜(SEM)观察试样表面的变化,同时测量试样的共振频率。结果表明,3D-C/SiC除通常CMC所产生的蠕变损伤外,纤维束滑动,纤维束之间的夹角变化,孔隙变形,部分孔隙表面空间位置改变,孔隙表面产生基体微裂纹,损伤在纤维束交叉处更为集中,这些可作为3D-C/SiC蠕变变形的独特机理。电阻和模量的相对变化与蠕变曲线相似,因此电阻和模量都可表征C/SiC材料的蠕变损伤,作为损伤变量。该材料的蠕变属于损伤引起。

Tensile creep properties of the 3D-C/SiC were examined in vacuum creep testing machine. After a period of the creep time, the specimen was taken out for observing specimen surface by SEM and measuring resonance frequency. The experimental results indicated that fiber tows slid, pores inter fiber bundles were deformed, on pores surface matrix micro-cracks more likely generated, and angles of inter fiber tows were changed. The creep damage concentrated in cross points of fiber tows. These were special creep mechanism of 3D-C/SiC. Relative variable curves of electric resistance and modulus resemble to creep curve, so they can be used to evaluate the creep damage. The creep is caused by damage, and it can be explained by damage creep mechanism of 3D-C/SiC.