陶瓷基复合材料（SiC_W／Y—TZP）在循环压应力下的疲劳裂纹扩展

CRACK PROPAGATION IN CERAMIC MATRIX COMPOSITE UNDER CYCLIC LOADS

研究了碳化硅晶须（ＳｉＣｗ）增强，Ｙ２Ｏ３稳定的ＺｒＯ２四方多晶体（Ｙ—ＴＺＰ）复合材料（ＳｉＣｗ／Ｙ—ＴＺＰ）在循坏压应力作用下的疲劳特性．单边缺口弯曲试样在纵向循环压应力作用了缺口根部产生垂直于压应力的Ⅰ型裂纹．类似于金属材料，在室温下循环压应力导致Ⅰ型裂纹的稳定扩展．压应力在缺口权部产生的不可逆损伤区在循环卸载过程中形成较大的残余拉伸应力场，使裂纹萌生并长大．同时，裂纹面产生的碎粒及晶须拔出导致裂纹闭合使裂纹最终停止扩展．

The fatigue behavior of SiCw / 3Y-TZP under cyclic compressive load has been investigated.The application of cyclic compressive stresses used to single notched samples of SiCw / 3Y-TZP can lead to stable mode I crack growth along the plane of the notch in a direction normal to the far-field compression axis. The rate of crack growth is faster at the beginning of test, and then slow with an increase in cycles number. At last, the growth arrests completely. The amplitude of the very first compression cycle plays a decisive role in influencing the extent of the residual tensile field and the total crack growth distance as there is no contact in the wake of the notch-tip. The residual tensile siresses generated by irreversible damage ahead of the notch-tip during compression loading cause the crack nucleation and growth in unloading process.Obeservations of whisker pull-out on the fatigue fracture surfaces are indicative of the locally tensile separation mode. The accumulation of debris within the cracks and the pull-out of whiskers causes the progressive development of closure in the wake of the advancing crack-tip leading to crack arrest.