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采用紧凑拉伸试件进行循环加载,研究了化学气相渗透工艺制备的二维平纹编织碳布增强碳化硅(C/SiC)复合材料的断裂韧性。基于实验结果,应变能释放率可分为弹性应变能释放率和不可逆应变能释放率,分别分析了弹性应变能释放率和不可逆应变能释放率随裂纹扩展的变化规律。发现在裂纹扩展初始阶段,裂纹分叉引起不可逆应变能释放率远高于弹性应变能释放率。随裂纹进一步扩展,不可逆应变能释放率迅速下降;最终两部分能量释放率都达到相近的平稳值,且不可逆应变能释放率大于弹性应变能释放率。对试件断裂表面进行扫描电镜分析,发现在裂纹尖端区域基体主要是剪切损伤,纤维具有很长的拔出长度。
Tensile toughness of two-dimensional plain weave carbon cloth reinforced silicon carbide (C / SiC) composites prepared by chemical vapor infiltration was studied by cyclic loading with a tensile specimen. Based on the experimental results, the strain energy release rate can be divided into the elastic strain energy release rate and the irreversible strain energy release rate, and the elastic strain energy release rate and the irreversible strain energy release rate with crack propagation are analyzed respectively. It is found that in the initial stage of crack propagation, the release rate of irreversible strain caused by crack bifurcation is much higher than the release rate of elastic strain energy. With the further expansion of the crack, the irreversible strain energy release rate declines rapidly. In the final two parts, the energy release rate reaches a steady value, and the irreversible strain energy release rate is greater than the elastic strain energy release rate. Scanning electron microscopy analysis of the fracture surface of the specimen shows that the matrix is mainly shear-damaged in the tip region of the crack, and the fiber has a long pull-out length.