Carbon/epoxy three-dimensional (3D) six-directional braided composites are fabricated and tensile fatigue behavior are reported. The results show that the composites have good fatigue properties and limit with small braiding angle. Fatigue life decreases with increasing the stress level. Dynamic modulus decreases and rate of stiffness degradation is also restricted by cycle number. Moreover, there are two regions on the hysteretic curve where the failure strain suddenly increases. Fracture morphology indicates that fatigue cracks spread from the outside to inside of the material and enter fiber/matrix interface, then to the fibers. The damage degree becomes more serious with increasing the stress level. At low stress levels, composite shows small damage and flush fracture. At high stress levels, it exhibits shear fracture along the braiding angle.

制造了碳/环氧树脂三维 (3D) 六向编织复合材料，并报告了拉伸疲劳行为。结果表明，复合材料具有良好的疲劳性能和小编织角极限。疲劳寿命随着应力水平的增加而降低。动态模量降低，刚度退化率也受到循环次数的限制。此外，在滞后曲线上有两个区域失效应变突然增加。断口形貌表明疲劳裂纹从材料的外部向内部扩展并进入纤维/基体界面，然后到达纤维。随着应力水平的增加，损伤程度变得更加严重。在低应力水平下，复合材料显示出小的损伤和齐平断裂。在高应力水平下，它会沿编织角出现剪切断裂。