变截面三维编织预制件的增减纱机制

从单元体角度分析了变截面三维编织预制件织造过程中增加或减少纱线的机制,讨论了单元数量减少法和单元尺寸缩减法2种具体实施方案的工艺、适用性和优缺点。采用数字摄影技术对预制件的表观结构进行了观测;采用拓扑方法对表面和内部减纱点处的纱线运动轨迹进行了分析,建立了纱线空间交织结构的几何模型。结果表明,采用2种减纱工艺制作的变截面预制件表面均无通透性孔洞缺陷,内部纱线倾斜方向无改变,倾斜角度稍有变化,整体结构不会出现明显应力集中,可以单独或联合使用制作变截面构件。

Methodology research on 3-D braided preform with changed-sections

The methodology of add or cut yarns during 3-D braiding courses were analyzed from a viewpoint of unit cell.The process,applicability,advantages and disadvantages of both the unit number reduction and unit size reduction methods were discussed.The apparent structure of the preform was observed by digital photograph,and the yarn tracks of cutting point in surface or inner control unit before and after cutting were obtained by topological analysis.Geometrical models of yarn interlace were built.The research shows that 3-D braided preforms made by these two cutting technologies have no such defect as holes.Yarn incline direction has not changed,and the incline angle changes a little.Therefore,there exists no obvious stress concentration in the whole structure.These methods are suitable,individually or in combination,for braiding section-changed composite products.