Abstract The behavior of damaged laminates under cyclic load is crucial to the damage tolerance of composite structures. In this experimental study, we investigate impact damaged laminates under tension–fatigue loading. For that purpose, a tension after impact (TAI) specimen is designed, which exhibits a similar impact behavior like a specimen of the established compression after impact (CAI) standard. A set of quasi-static TAI tests is conducted as a reference for the investigation under cyclic load. A 30 J impact was chosen as the baseline, causing a delamination-dominated barely visible impact damage. For the cyclic test, fifteen TAI specimens were distributed over three load levels. The tests reveal a widespread fatigue effect, edge delamination, and a significant growth of the impact-induced delamination. The damage propagates mainly in the load direction and in the interfaces close to the impact side. The observed delamination growth can be explained through to the fiber cracks caused by the impact. Moreover, the growth rate exhibits severe outliers, whose damage propagates exceptionally fast. These outliers can be traced back to the morphology of the impact damage. The qualitative pattern of fiber fracture massively influences the delamination propagation. Based on this dependency we outline the need for a qualitative evaluation of impact damage and its scatter.

中文翻译：

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冲击后拉伸疲劳复合材料层合板损伤增长的实验研究

摘要 循环荷载作用下受损层合板的行为对复合材料结构的损伤容限至关重要。在这项实验研究中，我们研究了在拉伸疲劳载荷下冲击损坏的层压板。为此，设计了冲击后拉伸 (TAI) 试样，其表现出与既定冲击后压缩 (CAI) 标准试样类似的冲击行为。进行了一组准静态 TAI 测试，作为循环负载下调查的参考。选择 30 J 的冲击作为基线，导致分层主导的几乎不可见的冲击损坏。对于循环试验，将 15 个 TAI 试样分布在三个载荷水平上。测试揭示了广泛的疲劳效应、边缘分层和冲击引起的分层的显着增长。损伤主要沿载荷方向和靠近冲击侧的界面传播。观察到的分层增长可以解释为由冲击引起的纤维裂纹。此外，增长率表现出严重的异常值，其损害传播异常快。这些异常值可以追溯到撞击损伤的形态。纤维断裂的定性模式极大地影响了分层传播。基于这种依赖性，我们概述了对冲击损伤及其散布进行定性评估的必要性。这些异常值可以追溯到撞击损伤的形态。纤维断裂的定性模式极大地影响了分层传播。基于这种依赖性，我们概述了对冲击损伤及其散布进行定性评估的必要性。这些异常值可以追溯到撞击损伤的形态。纤维断裂的定性模式极大地影响了分层传播。基于这种依赖性，我们概述了对冲击损伤及其散布进行定性评估的必要性。