温度和环境对2维C/(SiC–BxC)n断裂韧性的影响

Effects of Temperature and Environment on Fracture Toughness for Two Dimensional Carbon Fibre Reinforced(SiC–B_xC)_n Composite

采用单边切口梁法研究了二维碳纤维增强碳化硼–碳化硅复合材料(2D C/(SiC–BxC)n)在空气和真空两种环境下断裂韧性与温度的关系,用扫描电镜观察断口微观形貌。结果表明:真空中2D C/(SiC–BxC)n复合材料的断裂韧性随温度升高而降低,室温下界面结合弱,残余热应力大,易发生纤维桥接裂纹,断裂韧性高;高温下相反。在空气中随温度升高断裂韧性增加,700℃达到最大值,尔后随温度升高而降低,这与生成的B2O3和SiO2.B2O3固溶体会封填裂纹以及碳相的氧化有关。

The fracture toughness of two-dimensional carbon fibre-reinforced boron carbide-silicon carbide（2D C/（SiC–BxC）n） com-posite was investigated by means of single edge-notched beam method in both air and vacuum at different temperatures.The fracture morphologies were observed using scanning electron microscopy.The results show a significant reduction in the value of fracture toughness as the temperature increased in vacuum.The higher fracture toughness at room temperature is due to the fibres bridging of the crack caused by micro-residual stress and weak interfaces,whereas at high temperature the situation is opposite;the fracture toughness of 2D C/（SiC–BxC）n reaches its peak at 700 ℃ in air,then decreases.This is mainly related to the formation of B2O3 and SiO2？B2O3,which can seal the cracks,and it is related to oxidation of carbon component.