三维四向编织复合材料结构模型的几何特性

Geometrical characteristics of structural model for 3-D braided composites

建立合理的三维编织复合材料结构模型,对其力学性能的有限元计算结果具有重要影响.以成型后的三维四向编织复合材料为研究对象,在实验观察和以往研究的基础上,提出了一个新的有限元胞体结构模型,该模型正确地反映了纤维束的交织方式,更符合三维四向编织复合材料的实际细观结构.基于该单元模型推导了编织参数与结构模型参数之间的几何关系,计算了胞体中纤维体积比并讨论了其几何特性.研究结果表明:当纤维束中的纤维丝根数和纤维束半径,以及纤维体积含量一定时,编织物的花节长度和厚度随着纤维编织角的增大而分别减小和增大,三维四向编织复合材料结构的纤维体积比理论上可以达到68%.

It has significant effects on the FEA（finite element analysis） resuhs of the mechanical properties of braided composite to set up a reasonable structural model of 3-D（three-dimension）braided composite. The braided composite after molding was taken as a study object. According to the experimental result and former research, a new model of representative volume elements for FEA of braided composite was proposed. The new model truly reflected the braided manner, coinciding with the actual configuration of the 3-D and four-direction braided composites. On the basis of the new model, the relationship between the braiding parameter and the parameters of unit model was derived and the volume fraction of fibers in this representative volume element was calculated. By study- ing the geometrical characteristics of the braided composite, it indicates that if the volume fraction of yarn, the radi- us of yarn bundle and the number of yarns in a yarn bundle are invariable, the pitch length and thickness of composites will increase and decrease respectively with the increase of braiding angle, and the volume fraction can reach as much as 68 % theoretically.