Abstract Initial fibre misalignment is recognised to be one of the precursors leading to longitudinal compressive failure in fibre-reinforced composites. Thus, to properly model their mechanical behaviour, an accurate spatial representation of the fibrous reinforcements must be assured. This work presents a three-dimensional micromechanical framework that is capable of analysing in detail the longitudinal tensile and compressive failure mechanisms which are inherent in unidirectional composites. This is achieved through the incorporation of initial fibre waviness via a combination of a stochastic process and an optimisation procedure. A robust micro-scale framework is developed by assigning, to both constituents and their interface, proper thermodynamically consistent damage models. Several microstructures having different degrees of misalignment are modelled and a clear trend is observed for the longitudinal compressive load case, i.e. by increasing initial fibre misalignment, the overall performance of the material decreases. In contrast, the models subjected to longitudinal tension exhibit a similar overall response, despite the misalignment. However, local mechanisms seem to change with the degree of friction and fibre misalignment, but these smaller-scale mechanisms do not play a decisive role on the overall longitudinal tensile performance of the material.

中文翻译：

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单向复合材料纵向压缩和拉伸破坏的微观力学建模：通过随机过程引入的纤维错位效应

摘要 初始纤维错位被认为是导致纤维增强复合材料纵向压缩失效的前兆之一。因此，为了正确模拟它们的机械行为，必须确保纤维增强材料的准确空间表示。这项工作提出了一个三维微机械框架，能够详细分析单向复合材料中固有的纵向拉伸和压缩破坏机制。这是通过结合随机过程和优化程序结合初始纤维波纹度来实现的。通过为成分及其界面分配适当的热力学一致损伤模型，开发了一个强大的微尺度框架。对具有不同错位度的几种微观结构进行建模，并观察到纵向压缩载荷情况的明显趋势，即通过增加初始纤维错位，材料的整体性能下降。相比之下，尽管存在错位，承受纵向张力的模型表现出相似的整体响应。然而，局部机制似乎随着摩擦和纤维错位的程度而变化，但这些较小规模的机制对材料的整体纵向拉伸性能并不起决定性作用。尽管未对准，但承受纵向张力的模型表现出相似的整体响应。然而，局部机制似乎随着摩擦和纤维错位的程度而变化，但这些较小规模的机制对材料的整体纵向拉伸性能并不起决定性作用。尽管未对准，但承受纵向张力的模型表现出相似的整体响应。然而，局部机制似乎随着摩擦和纤维错位的程度而变化，但这些较小规模的机制对材料的整体纵向拉伸性能并不起决定性作用。