Abstract The present study is focused on the characterization of the fatigue damage features in carbon/epoxy laminates under mode-II loading conditions. To this aim, a sinusoidal cyclic load was applied to the End-Notched Flexural (ENF) specimens and the fatigue behavior of specimens was investigated. Scanning Electron Microscope (SEM) was used to identify the damage features on the fracture surface, i.e. fiber imprints, cusps, roller cusps, and striations. It was found that the fatigue damage features, such as cusps and striations, completely depended on the fatigue crack growth rate, da/dN. In addition, a linear relationship between the fatigue striation space and the strain energy release rate range (ΔGs) and the hysteresis loop area was established. The Acoustic Emission (AE) method was also employed to characterize the damage features. The obtained results showed that higher AE energy indicates larger and rougher cusps and striation features.

中文翻译：

---

模式 II 疲劳裂纹增长率对 CFRP 复合层压板断口特征的影响：声发射和扫描电子显微镜分析

摘要 本研究的重点是表征 II 型加载条件下碳/环氧树脂层压板的疲劳损伤特征。为此，对端部缺口弯曲 (ENF) 试样施加了正弦循环载荷，并研究了试样的疲劳行为。扫描电子显微镜（SEM）用于识别断裂表面的损伤特征，即纤维印记、尖端、辊子尖端和条纹。结果表明，疲劳损伤特征，如尖峰和条纹，完全取决于疲劳裂纹扩展速率 da/dN。此外，建立了疲劳条纹空间与应变能释放率范围（ΔGs）和磁滞回线面积之间的线性关系。还采用声发射 (AE) 方法来表征损伤特征。