This paper experimentally investigates the fatigue behavior and failure mechanism of a quasi-three-dimensional woven composite (Q3DWC) under combined high and low cycle fatigue loading (CCF) for the first time. In this study, to develop a composite with high tensile strength and sufficient delamination resistance, a Q3DWC structure is firstly designed. Then, a novel biaxial experimental platform, including the longitudinal tensile system, the lateral excitation system, and the dynamic signal monitoring system, is established. Based on this platform, a comprehensive analysis, including fatigue life, stiffness degradation, energy dissipation, and fracture morphology, is conducted. Results indicate that the superimposed high cycle fatigue (HCF) significantly reduces the fatigue life when compared to low cycle fatigue (LCF) life. Stiffness degradation and energy dissipation are obtained by hysteresis loops, showing that the entire fatigue process is mainly divided into three stages. Moreover, fracture morphologies are analyzed via scanning electron microscopy (SEM), indicating more severe fiber pull-out and fiber/matrix debonding due to the introduction of HCF vibration. Finally, the probable damage evolution under LCF and CCF loading is discussed separately. This study provides valuable references for the design and safe application of composites under CCF loading.

中文翻译：

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准三维编织复合材料在高低周联合疲劳下的疲劳行为及失效机理研究


本文首次实验研究了准三维编织复合材料 （Q3DWC） 在高低周联合疲劳载荷 （CCF） 下的疲劳行为和失效机制。在本研究中，为了开发具有高拉伸强度和足够抗分层性的复合材料，首先设计了 Q3DWC 结构。然后，建立了一种新型的双轴实验平台，包括纵向拉伸系统、侧向激励系统和动态信号监测系统。基于该平台，进行了包括疲劳寿命、刚度退化、能量耗散和断裂形态在内的综合分析。结果表明，与低周疲劳 （LCF） 寿命相比，叠加的高周疲劳 （HCF） 显着缩短了疲劳寿命。通过磁滞回线获得刚度退化和能量耗散，表明整个疲劳过程主要分为三个阶段。此外，通过扫描电子显微镜 （SEM） 分析了断裂形态，表明由于 HCF 振动的引入，纤维拉出和纤维/基体脱粘更加严重。最后，分别讨论了 LCF 和 CCF 载荷下可能的损伤演变。本研究为 CCF 载荷作用下复合材料的设计和安全应用提供了有价值的参考。