中文摘要：

介绍变截面三维编织预型件的减纱净形制备工艺,通过实验观察与理论建模相结合的方法,分析减纱对预型件细观结构的影响,对比整列减纱、行单元减纱与切削复合材料在变截面区域的弯曲性能。结果表明表面与内部减纱单元是减纱时的基本单位,保证编织规律不变是减纱工艺的基本原则;表面或内部单元减掉后分别会形成两组特殊的纱线轨迹,其中一组纱线的长度与编织角大小较不减纱时增大,而另一组纱线只改变编织角的方向;行单元减纱与整列减纱复合材料的弯曲性能均明显优于切削试件,且行单元减纱试件的弯曲性能比整列减纱试件略高。

英文摘要：

Yarn-reduction technique was introduced for the net-shape preparation of tapered 3D braided preforms.The architectures of preforms were first investigated in different yarn-reduction manners by experimental observation and theoretical modeling.Bending performance in the tapered region of the column yarn-reduction composites,row unit yarn-reduction composites and cut composites were compared.The results show that surface or interior yarn-reduction unit is the basic yarn element to be removed and the braiding rules should be undisturbed after yarn-reduction.Two groups of special yarn trajectories are formed corresponding to the removals of a surface and an interior reduction units,respectively.In one group,the length and orientation degree increase relative to non-yarn-reduction,while in other group,found is only the change of the orientation directions.The row unit yarn-reduction composites have slightly better bending performance than the column yarn-reduction composites,while both of them have their bending performances significantly higher than those of the cut composites.