三维编织碳/碳复合材料高温力学及疲劳试验研究

Experimental investigation on fatigue of 3D braided C/C composites at high temperatures

在大气环境下,对有抗氧化涂层的非切边和切边三维(3D)四向碳/碳复合材料在室温、800和900℃下进行编织纵向拉伸试验,得到了相应工况下的弹性模量、拉伸强度以及应力-应变曲线;在800℃下对两种试件进行编织纵向拉/拉疲劳试验,得到了疲劳寿命数据以及剩余刚度随循环载荷的变化规律。采用扫描电子显微镜(SEM)对破坏后的试件断口进行观察研究,分析材料拉伸破坏机制以及疲劳破坏机制。结果表明:三维四向碳/碳复合材料的拉伸强度和弹性模量随着温度的升高而增大,非切边试件的力学性能优于切边试件;三维四向碳/碳复合材料剩余刚度随循环载荷先增加而后减小;材料的拉伸破坏形式以纤维拉伸为主,温度升高后,断口出现纤维束成簇拔出现象,疲劳破坏形式以纤维拉伸为主并伴随一定的纤维簇拔出和基体分层现象。

The braided longitudinal tensile test of anti oxidation coating coated non trimming and trimming3D four directional carbon/carbon(C/C)composites were investigated.The strength,elastic modulus and stress strain curves were obtained in atmospheric environment at room temperature,800and900℃.The fatigue life data and residual stiffness with cyclic loading were obtained from the braided longitudinal tensile/tensile fatigue test for two kinds of specimens when temperature raised to800℃.The static tensile and fatigue specimen fractures were observed by scaning electron microscope(SEM).Tensile failed mechanism and tensile/tensile fatigue failed mechanism were analyzed.Results showed that the tensile strength became higher with temperature increase,and the mechanical property of non trimming specimens was much better than that of trimming ones.The residual stiffness of3D four directional C/C composites first increased and then decreased.The main failed mode of specimen was fiber tensile,but bundles of fibers pulled out when temperature elevated.More pull out fiber in fatigue failed than tensile failed at the same temperature,and the matrix was delaminated obviously under fatigue load.