平纹编织C/SiC复合材料的断裂韧性(英文)

FRACTURE TOUGHNESS OF PLAIN WOVEN C/SiC COMPOSITES

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。

Fracture toughness of two dimensional plain woven C/SiC composite fabricated by the process of chemical vapor infiltra- tion by cycle loading was measured by the standard compact tension method. According to the test results, the release rate of strain energy can be divided into two categories： the elastic strain energy release rate and the irreversible strain energy release rate. The laws of the change of elastic strain energy release rate and irreversible strain energy release rate were investigated with the extension of cracks. The results show that during the beginning stage in the extension of cracks, the irreversible strain energy release rate caused by crack branching is much higher than the elastic strain energy release rate. With the further propagation of cracks, the irreversible energy release rate decreases rapidly. At last, both the irreversible energy release rate and the elastic energy release rate reach a similar plateau, and the irreversible strain energy release rate is greater than the elastic strain energy release rate. Scanning electron microphotographs of the fracture surface show that the damage near the notch tip area is mainly shear damage and relatively long fiber pull-out lengths can be observed.