Flax fibre mats are promising and versatile biosourced reinforcements that can be used in composite parts obtained using various processing routes. To optimise their impregnation and the end-use properties of composites, it is crucial to better understand the process-induced evolution of their microstructure and their permeability. In this study, flax fibre mats were subjected to in situ X-ray microtomography compression experiments. The resulting 3D images enabled the evolution of several key descriptors of their microstructure under compression to be determined, and the evolution of their permeability to be quantified by direct fibre scale CFD simulations. The microstructural data were also used as input parameters of a modified directional Kozeny-Carman model, accounting for the anisotropy and heterogeneity of mats. Only one unknown directional parameter was identified by inverse method from permeability calculations performed on numerically generated 3D realistic fibre networks. The predictions of the proposed model were consistent with numerical simulations.

亚麻纤维垫是一种很有前途的多功能生物来源增强材料，可用于使用各种加工途径获得的复合材料部件。为了优化复合材料的浸渍和最终使用性能，更好地了解其微观结构和渗透性的过程诱导演变至关重要。在这项研究中，亚麻纤维垫进行了原位 X 射线显微断层扫描压缩实验。由此产生的 3D 图像能够确定压缩下其微观结构的几个关键描述符的演变，并通过直接纤维尺度 CFD 模拟来量化其渗透率的演变。微观结构数据也用作修正的定向 Kozeny-Carman 模型的输入参数，说明垫的各向异性和异质性。通过对数值生成的 3D 真实纤维网络进行渗透率计算的逆向方法，仅识别出一个未知的方向参数。所提出模型的预测与数值模拟一致。