四步法三维矩形编织复合材料的细观结构模型

基于现有实验研究和编织工艺中携纱器的运动规律, 重点分析了材料内部区域纤维束的空间构型, 建立了材料的三维实体细观结构模型。该模型不仅体现了内部纱线因打紧工序而形成的紧密接触和截面变形, 而且考虑了内部和表面区域纱线因挤紧状态不同所造成的纱线填充因子变化。基于一种单胞取向平行于材料横截面边界方向的新划分方案, 解决了45°单胞划分方案的不足, 建立了便于力学性能分析的单胞几何模型, 并指出了编织工艺参数和模型宏细观结构参数的关系。模型数值结果与试件实测数据吻合, 表明了该模型的合理有效性,为材料后续力学性能分析奠定了基础。 

On the microstructure model of four-step 3D rectangular braided composites

Based on the existing experiment observation and the movement t races of yarn carriers on the braidingmachine bed , a microst ructure model of 4-step three-dimensional rectangular braided composites is established bythe analytical approach. Especially , the spatial configuration of interior yarns was analyzed in detail , and the distortion of the cross-section of interior yarns caused by mutual contact and jamming was considered in the model. As thejamming conditions in different regions were not uniform , the yarn packing factor of interior yarns was differentfrom that of surface yarns and corner yarns in the model. Then a new unit-cell partition scheme that can overcomethe shortcomings of the existing 45°partition schemes was proposed to make the directions of all the unit-cells parallel with the edges of the cross-section of the composites. Then the microst ructure unit-cell models for the three regions of the composites , the interior , surface and corner were established , which were expediently utilized to establish the prediction models of mechanical properties. By using the unit cell models , the st ructural geometry of thecomposites was analyzed , and the mathematical relation between technics parameters and microst ructure of the unitcells was obtained. The calculated values of the geometric characteristics of braided composites specimens by themodel well agree with the measured values. The numerical results indicate the effectiveness of the model , and thepresent model has presented a foundation for the mechanical performance prediction of the composites.