SiC/SiC复合材料的力学性能

Mechanical Properties of SiC/SiC Composites

采用低压化学气相沉积(LPCVD)法制备了具有热解碳界面层的2.5维SiC/SiC复合材料。研究了残余孔洞及热解碳界面层厚度对材料力学性能的影响。结果表明:材料弯曲强度受纤维束之间大孔的影响很小,主要与纤维间的小孔有关,随小孔尺寸和数量的减小而增大。当气孔率低于27%时,小孔的数量和尺寸均变化不大,材料强度提高有限。90nm厚热解碳界面层的存在使材料由破坏性断裂变为非破坏性断裂,强度由174MPa增加到305MPa。进一步增加界面层厚度,纤维受到损伤,材料的力学性能下降。界面层为180nm和310nm厚时SiC/SiC的强度分别为274MPa和265MPa,纤维拔出数量少,材料近似破坏性断裂。

2.5 dimensional SiC/SiC composites with pyrocarbon interlayer were fabricated by low pressure chemical vapor deposition （ LPCVD）. Effects of residual pores and interlayer thickness on mechanical properties of fabricated SiC/SiC composites were investigated. The flexural strength of the composites is mainly affected by the micro-pores between filaments instead of the macro-pores between yarns. Strength increases with the decrease of the amount and size of micro-pores. When the porosity is below 27% , the further decrease of the porosity does not change the amount and size of micro-pores and hardly contributes to the strength. The existence of a pyrocarbon interlayer of 90nm thickness increased composite strength from 174 MPa to 305 MPa, and changed the fracture behavior from catastrophic fracture to non-catastrophic fracture. The further increase of interlayer thickness results in fiber damage which reduces the mechanical properties of the composites. The strength of the composites with 180nm and 310nm thick interlayers is 274 MPa and 265 MPa, respectively. Their amount of fiber pullout is small and the fracture behaviors are similar to catastrophic fracture.