加载循环数对2D针刺C/SiC复合材料疲劳剩余强度的影响

为研究陶瓷基复合材料的低周疲劳失效机理,通过试验和细观分析对其疲劳特性进行了探讨。研究了室温下加载循环数对2D针刺C/SiC复合材料拉-拉疲劳剩余强度的影响,并采用光学显微镜和扫描电子显微镜对该材料的断口形貌和微观结构进行了观察。结果表明:2D针刺C/SiC复合材料具有较好的抗疲劳特性,在85%极限拉伸强度(UTS)载荷下的循环数超过106;随着加载循环数的增加,剩余强度先增大然后下降。断口分析表明:纤维拔出长度随着加载循环数的增加而增加,说明在疲劳加载过程中,纤维/基体的界面结合强度降低,减缓了材料内部受力的不均匀性,提高了材料的承载能力,使2D针刺C/SiC复合材料出现了疲劳强化现象。 

Effects of loading cycles on fatigue residual strength for 2D needled C/SiC composites

In order to study the failure mechanism under low cycle fatigue loading of ceramic matrix composites, their fatigue behavior was investigated through tests and mesoscopre analysis. The effects of loading cycles on the residual strength after tension-tension fatigue were studied for 2D needled C/SiC composites at room temperature. The fracture morphology and microstructure of the materials were observed by optical microscope and scanning electron microscope. The results show that the 2D needled C/SiC composites present an outstanding fatigue resistance as the loading cycle is over 10⁶ cycles while loading at level of 85% ultimate tensile strength (UTS). With the increase of loading cycles, the residual strength first increases then declines. The fracture analysis shows that the length of pull-out fibers increases as loading cycle increase, which means that in the process of fatigue loading, the bonding strength of fiber/matrix interface declines, which can eliminate the stress nonuniformity in materials and enhance the bearing capacity of the composites, and result in the fatigue strengthening phenomenon of 2D needled C/SiC composites.