Abstract The sudden compressive failure of unidirectional (UD) fibre reinforced composites at loads well below their tensile strengths is a cause of practical concern. In this respect and more generally, analytical and numerical models that describe composite behaviour have been hard to verify due to a lack of experimental observation, particularly in 3D. The aim of this paper is to combine fast in-situ X-ray computed tomography (CT) with advanced image analysis to capture the changes in fibre orientation in 3D during uninterrupted progressive loading in compression of a UD glass fibre reinforced polymer (GFRP). By analysing and establishing correspondence between a sequence of time-lapse X-ray CT images of the composite, we are able for the first time to follow each fibre and quantify the progressive deflection that takes place during axial compression in the steps leading up to fibre micro-buckling and kinking. Even at just 25 % of the failure load, fibres have started to tilt in approximately the direction of the ultimate kink band. The rate of tilting increases as the composite approaches the collapse load. More generally, our approach can be applied to investigate the behaviour of a wide range of fibrous materials under changing loading conditions.

中文翻译：

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通过延时 X 射线成像和单根纤维跟踪量化复合材料轴向压缩过程中的纤维重新定向

摘要 单向 (UD) 纤维增强复合材料在远低于其拉伸强度的载荷下突然压缩破坏是一个实际问题。在这方面，更一般地说，由于缺乏实验观察，特别是在 3D 中，描述复合材料行为的分析和数值模型很难验证。本文的目的是将快速原位 X 射线计算机断层扫描 (CT) 与高级图像分析相结合，以捕捉 UD 玻璃纤维增​​强聚合物 (GFRP) 压缩过程中不间断渐进加载期间 3D 中纤维取向的变化。通过分析并建立复合材料的一系列延时 X 射线 CT 图像之间的对应关系，我们第一次能够跟踪每根纤维并量化轴向压缩过程中导致纤维微屈曲和扭结的步骤中发生的渐进偏转。即使只有 25% 的失效载荷，光纤也开始向大约最终扭结带的方向倾斜。随着复合材料接近坍塌载荷，倾斜率增加。更一般地说，我们的方法可用于研究各种纤维材料在不断变化的负载条件下的行为。