典型多向2.5D机织预制体近净形编织结构设计

针对多向异型复合材料构件用3D整体预制体，基于衬经2.5D机织结构，提出5种近净形转向仿形编织工艺，设计并制备了具有典型引纱加纱结构的板条状预制体试样。采用计算机断层扫描法(Micro-CT)，观测各系统纱线横截面形态变化和纱线取向分布规律，发现引出加入的纱线沿织物厚度方向挤紧状态发生改变，其横截面从椭圆形变成梯形，又变为三角形，经纱被引出和加入会造成与其接触的纬纱横截面变化。结合复合材料构件的实际承载工况，对具有5种引纱加纱结构的复合材料试样进行了经向抗弯性能测试，结果表明，复合材料的弯曲强度和弯曲模量保持率分别达到82.6%~95.7%和89.1%~97.9%。可见，立足于满足复合材料力学性能要求，发展预制体的三维整体仿形编织技术，是实现复杂形状复合材料构件材料/结构一体化制造的有效途径。 

Near net-shaped design on the architecture of typical multi-directional 2.5D woven preform

According to the 3D integral preform which is used for multidirectional heteromorphic shaped composite parts, the preform sample with typical pulling in and adding in yarn structure was designed and prepared based on the 2.5D woven with warp-stuffer preform. Computed tomography (Micro-CT) was used to observe the morphological changes of the yarn cross-section and the distribution of yarn orientation in each system. The squeezed state of the pulled out and added in yarn changes along the thickness direction of the preform, and the cross-section shape of the pulled out and added in yarn are changed from an ellipse to a trapezoid, and then to a triangle. When the warp yarns are pulled out and added in, the cross-section of the weft yarns in contact with them change. Combining the practical loading condition of the composite parts, 5 kinds of composites with pulling out-adding in yarns were tested by three-point bending in warp direction. The results show that the retention rates of bending strength and modulus of the composites reach 82.6%-95.7% and 89.1%-97.9%, respectively. So, to meet the mechanical performance requirements of the composites, developing the 3D integral shaped braided technology of preforms is the effective approach for realizing the material/structure integrated manufacturing of complex shaped composite parts.