中文摘要：

采用四步法三维编织以及VARTM技术制得三维编织复合材料T型梁,利用MTS 810.23仪器对材料进行准静态三点弯曲测试,使用频率为3Hz、应力比R=1的正弦波加载条件对材料进行弯曲疲劳测试.根据测得的数据分析获得S-N曲线、应力位移曲线以及最大最小位移曲线,材料在50％应力水平下其三点弯曲疲劳加载循环次数超过50万次.通过最终破坏形态可知,筋高处纤维的断裂是导致材料最终失效的主要破坏模式.

英文摘要：

This paper reports the three-point bending fatigue behaviors of four-step 3D braided composite Tbeam manufactured by four-step braiding technology and vacuum assisted resin transfer molding （VARTM）.The fatigue failure of the braided composite T-beam under different stress levels have been represented to explain the fatigue behaviors.The quasi-static three-point bending tests were conducted on the MTS 810.23 material tester system,and the fatigue tests with the sinusoidal wave loading of frequency of 3 Hz and stress ratio （R） value of 0.1 were implemented on the same system.The S-N curve,stress-displacement curves and the max and min deflections curves based on experimental data were used for analysis,and the load cysles of three-point fatigue test under stress level of 50％ was found tobe over 5 × 105 times.The fiber breakage on the web is the main damage mode which leads the ultimate failure of the 3 D braided composite T-beam according to the damage morphologies.