中文摘要：

减纱工艺可以实现变截面三维编织复合材料的净形制备,通过对不同减纱方案制备的单次减纱试件和具有不同减纱截面间距的两次减纱试件进行三点弯曲实验,研究了减纱工艺参数对变截面三维编织复合材料弯曲性能和破坏形态的影响.结果表明,行单元减纱试件的弯曲性能略高于整列减纱试件而显著优于切削试件,纱线断裂是减纱试件的主要失效机制,切削试件则以基体和界面损伤为主.两减纱截面间隔1-3个花节时,试件主要在第2个减纱截面附近发生破坏,而间隔4或5个花节时,弯曲破坏集中在两减纱截面的中间区域.随着减纱截面间距由1花节递增至4花节,试件的弯曲性能逐渐提高,而间距为5花节的试件则与间距4花节试件的弯曲性能基本相同.

英文摘要：

Yarn-reduction techniques can realize net-shape preparation of tapered 3D braided composites.The influence of yarn-reduction plans and distances between yarn-reduction cross-sections on bending properties and fracture morphologies of tapered composites were studied,respectively.Results show that bending properties of the row unit yarn-reduction composites are slightly higher than those of the column yarn-reduction composites and significantly better than the cut composites.Yarn breakage is the primary failure mechanism of the yarn-reduction composites,while matrix cracking and interfacial debonding are the main damage mechanisms of the cut composites.When the distances between yam-reduction cross-sections are 1 pitch to 3 pitches,damages mainly occur near the second yarn-reduction cross-section.However,obvious damages are found in the center of the two yarn-reduction cross-sections when the distances are 4 and 5 pitches.As the distances between yarn-reduction cross-sections increase from 1 pitch to 4 pitches,bending properties of the composites increase,too.However,composites with 5 pitches distance have nearly the same bending properties as composites with 4 pitches distance.