探讨了变截面三维编织预制件减纱净成型原理,结合图像观测与拓扑分析方法表征减纱区域细观结构,对比减纱变截面与切削变截面复合材料截面缩减区域及相应等截面复合材料的弯曲力学性能,并分析两种变截面试件在破坏模式上的异同。结果表明:减纱应遵循的原则是保证具有连续可编织性,减纱预制件在截面缩减区域呈现平滑的梯形过渡,其弯曲模量与强度显著高于切削变截面试件而略低于等截面试件,且表现为以纱线断裂为主、包括基体开裂和纤维抽拔等模式的复合型破坏。 In this paper, the principle of yarn-shedding and net forming in three-dimensional braided preform of variable section was discussed. The meso-structure of the yarn-cut region was characterized by the combination of image observation and topological analysis. By comparing the reduction cross section of cut yarn with that of the tapered cross section and the corresponding cross section Bending mechanical properties, and analyze the similarities and differences between the two kinds of specimens with different cross-sections in failure mode. The results show that the principle of yarn reduction should be followed to ensure the continuous weaving. The yarn preform has a smooth trapezoidal transition in the reduced area, and its flexural modulus and strength are significantly higher than those of the cutting cross-section specimens Section specimens, and manifested as the main yarn fracture, including matrix cracking and fiber extraction and other modes of composite damage.