Abstract For the last 20 years, plant fibres have emerged as an alternative to glass fibres in composites. However, a crucial issue with plant fibre composites is their durability, i.e. their long-term hygrothermal and fatigue performances. This study deals with the influence of different conditionings (Ambient, Wet and Wet/dry) on the fatigue behaviour of [(±45)]7 hemp/epoxy composites. The induced damage mechanisms are investigated by acoustic emission and micro-CT. Results show that the Wet samples exhibit the lowest fatigue sensitivity despite their greatest damage quantity, whereas the Wet/dry specimens behave like pre-damaged Ambient ones. Micro-CT scans show that the same type of damage appears in all cases: cracks are made of a coalescence of partial debondings at hemp yarn/matrix interfaces, which can lead to macro-cracks crossing the sample thickness. Moreover it is demonstrated that, during fatigue tests, the evolution of cumulative AE energy and hysteresis loop energy, and the evolution of damage quantity measured by micro-CT and final hysteresis energy, are very similar whatever the conditioning.

中文翻译：

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水分和干燥对编织麻/环氧树脂复合材料疲劳损伤机制的影响：声发射和微 CT 分析

摘要 在过去的 20 年中，植物纤维已成为复合材料中玻璃纤维的替代品。然而，植物纤维复合材料的一个关键问题是它们的耐久性，即它们的长期湿热和疲劳性能。本研究涉及不同条件（环境条件、湿条件和湿/干条件）对 [(±45)]7 大麻/环氧树脂复合材料疲劳行为的影响。通过声发射和微 CT 研究诱导损伤机制。结果表明，湿样品尽管损伤量最大，但表现出最低的疲劳敏感性，而湿/干样品表现得像预损坏的环境样品。显微 CT 扫描显示在所有情况下都会出现相同类型的损坏：裂纹是由大麻纱线/基质界面处部分脱粘的聚结形成的，这会导致跨越样品厚度的宏观裂纹。此外还表明，在疲劳试验中，累积 AE 能量和滞后回线能量的演变，以及微 CT 和最终滞后能量测量的损伤量的演变，无论何种条件都非常相似。