碳纤维增强树脂基复合材料（CFRP）在航空航天等领域得到广泛应用，CFRP构件的超高周疲劳问题逐渐凸显出来。本文采用超声三点弯曲疲劳试验系统对CFRP复合材料的损伤演化过程进行研究。结果表明：CFRP复合材料在超高周三点弯曲加载下的S-N曲线呈阶梯状，尤其在108周次后，其疲劳强度明显下降。通过对CFRP复合材料在同一视场不同周次下的损伤过程进行分析，发现该材料在超高周加载下的损伤形貌主要表现为3种特征：纤维束交叉处基体损坏、近纤维束平行段基体空洞、基体贯穿，并随着加载周次的增加，其损伤过程也按照这3种特征依次呈现出来。
Carbon Fiber Reinforced Polymers (CFRP) has been widely used in aerospace and other fields. The ultra-high cycle fatigue of CFRP components has become more and more obvious. In this paper, the damage evolution process of CFRP is experimentally investigated via ultrasonic fatigue testing system for cyclic three-point bending. The results indicated that the S-N curve of CFRP composites presented a step-wise shape under the ultra-high testing for cyclic three-point bending, and especially, the fatigue strength decreases significantly after the cycles are more than 108. By investigating the damage evolution process of CFRP in the same field of view, this paper found that the damage morphology of CFRP composites under ultra-high cycle loading is mainly characterized by the matrix damage at the intersection of fiber bundles, near-fiber bundle parallel section matrix cavity, and matrix penetration. With the increase of test cycles, the damage process is also presented in turn according to the above three characteristics.
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