ABSTRACT

This paper focuses on the fatigue performances and reliability analysis of fatigue life for scarf-repaired carbon fiber composite laminates, which plays an important role in ensuring the safety of repaired aircraft. Tension–tension fatigue tests at constant-load amplitude were conducted to determine the fatigue limit and mechanism of scarf-repaired composite laminates. Experimental results show that the fatigue limit of scarf-repaired composite laminates is about 34% of the static tensile strength and the failure modes of speicmens under different stress levels are similar. The dominated failure mode is cohesive failure of adhesive, accompanied by partial 45° and 90° matrix cracks of composite patch. Meanwhile, the stiffness degradation and crack observation indicate that the crack initiation stage occupies a large proportion (92 ± 5%) of fatigue life. In additon, the distribution of fatigue life data was discussed. Based on the best fitting distribution, a new approach incorporating both reliability and confidence level was proposed to predict the fatigue life of scarf-repaired composites.

摘要

本文重点研究了嵌缝修复碳纤维复合材料层合板的疲劳性能和疲劳寿命可靠性分析，对保障修复后的飞机安全具有重要作用。进行了恒定载荷幅值的拉伸-拉伸疲劳试验，以确定斜接修复复合材料层压板的疲劳极限和机理。实验结果表明，嵌缝修复复合层合板的疲劳极限约为静态抗拉强度的34%，不同应力水平下试样的破坏模式相似。主要的失效模式是粘合剂的内聚失效，并伴有复合贴片的部分45°和90°基体裂纹。同时，刚度退化和裂纹观察表明，裂纹萌生阶段占疲劳寿命的很大比例（92±5%）。此外，还讨论了疲劳寿命数据的分布。基于最佳拟合分布，提出了一种结合可靠性和置信度的新方法来预测嵌缝修复复合材料的疲劳寿命。