浸渗法制备SiC_f/SiO_2复合材料的力学性能研究

Mechanical performance of SiC_f/SiO_2 composite fabricated by impregnation method

使用硅溶胶浸渍沉积和未沉积碳界面层的碳化硅纤维2.5D编织体,制备了SiCf/SiO2复合材料。抗弯测试结果显示,随着处理温度的升高,基体缓慢释放出的结合水对纤维造成氧化损伤,使试样的抗弯强度均下降,但始终表现出非脆性断裂行为,这主要是由于基体与纤维的热膨胀系数差别较大,使得基体与纤维之间未形成强结合。另外,由于碳界面层对纤维的保护使得纤维免遭氧化损伤,沉积过碳界面层的试样在各温度处理后的抗弯强度均高于未沉积过碳界面层的试样。

The SiO2 sol was used to impregnate the 2.5D woven SiC fiber bodies with and without C interface to prepare SiCf/SiO2 composites.The result shows that the bending strength of the two kinds of composites declines as the treatment temperature rises due to the oxidation damage to the fiber by bound water releasing from the matrix in the process.Their tough fracture results from weak bonding between the fiber and the porous matrix which is led from the difference of the coefficient of thermal expansion of fiber and matrix.The higher strength of the composites with the C interface is attributed to its protection of the fibers from oxidation of water vapor during heat treatment.