Abstract
On the basis of analyzing the movement law of 3D circular braided yarn, the three-cell model of 3D five-direction circular braiding composite material is established. By analyzing the node position relationship in various cell models, the calculation formulas of braiding angle, cell volume, fiber volume and fiber volume content in various cell models are obtained. It is found that there are four different braiding angles in four internal cells, and the braiding angles in internal cells gradually increase from inside to outside. The braiding angles of upper and lower surface cells are approximately equal. With the increase of the length of the knuckles, the braiding angles of each cell decrease, and the braiding angles of the four inner cells decrease greatly, while the braiding angles of upper and lower surfaces decrease slightly. The results of parametric analysis showed that with the increase of the length of the knuckles and the inner diameter of cells, the mass of cells increased proportionally, while the total fiber volume content of cells decreased. With the increase of braiding yarn number and axial yarn number, the unit cell mass decreases in direct proportion, and the unit cell total fiber volume content increases. Through the research results of this paper, the geometrical characteristics of the cell model under different braided parameters can be obtained, which greatly improves the analysis efficiency.
Highlights
The 3D braided composites are made by braiding fibers into preforms with specific structural shapes according to certain movement rules, and compounding, compacting and curing the preforms with liquid matrix
The results show that the compressive mechanical behavior of braided composites with smaller braiding angles is sensitive to the initial defects of braided yarns, and the strength of braided composites with different braiding angles is controlled by different microscopic failure modes
The relationship between the mass m, knuckle length h, radial yarn number M and axial yarn number N of the 3D annular braiding material unit cell is shown in Fig 15, in which the unit cell inner diameter Rin = 5mm
Summary
The 3D braided composites are made by braiding fibers into preforms with specific structural shapes according to certain movement rules, and compounding, compacting and curing the preforms with liquid matrix. The results show that the compressive mechanical behavior of braided composites with smaller braiding angles is sensitive to the initial defects of braided yarns, and the strength of braided composites with different braiding angles is controlled by different microscopic failure modes These studies have laid a foundation for the application of braided composites in aerospace and other fields [10]. In Sec., according to the established parametric relationship of 3D circular braided material cells, the influences of input parameters such as the knuckle length and cell inner diameter on cell mass, fiber volume content and braiding angle are discussed. Through the parametric relationship of three cells of 3D and five-directional annular braided composites established in this paper, the parameters such as cell mass, fiber volume content and braiding angle can be quickly predicted, which provides convenience for the prediction of mechanical properties and parametric modeling of 3D annular braided composites
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