In this study, the effects of defects in a triaxial braided textile composite was studied at unit cell level using three-dimensional finite element analysis. The manufacturing defects such as void defect and tow misalignments were considered in the model and the effect of their presence at different scale on the effective material properties were studied. The configuration of the finite element model was based on the geometric data extracted from an experimental test specimen. The representative unit cells (RUC) that repeat itself to build the whole braid were sliced out from the full interlaced geometry of axial and bias tows. Periodic boundary condition (PBC) was used to simulate the repeating nature of the unit cells. Then, numerical tests were performed to compute three-dimensional effective material properties for triaxial braided RUCs with predetermined void volume fractions and axial tow misalignment under uniaxial tension and shear loadings in different directions. It was observed that the void defects severely affected the out-of-plane properties of the material, while the tow misalignments influenced the axial modulus mostly.

中文翻译：

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缺陷对三轴编织纺织复合材料有效材料性能的影响

在这项研究中，使用三维有限元分析在晶胞水平上研究了三轴编织纺织复合材料中缺陷的影响。模型中考虑了制造缺陷，如空隙缺陷和丝束错位，并研究了它们在不同尺度上的存在对有效材料性能的影响。有限元模型的配置基于从实验试样中提取的几何数据。从轴向和偏置丝束的完整交错几何形状中切出重复自身以构建整个编织物的代表性单元格 (RUC)。周期性边界条件 (PBC) 用于模拟晶胞的重复性质。然后，进行了数值试验以计算在不同方向的单轴拉伸和剪切载荷下具有预定空隙体积分数和轴向丝束错位的三轴编织 RUC 的三维有效材料特性。观察到空隙缺陷严重影响材料的面外性能，而丝束错位主要影响轴向模量。