The Microscopic Analysis Of Braided Geometry And Mechanical Properties For Three-dimensional Braided Composite

Three-dimensional braided composite is the product of the combination ofmodern weaving techniques and modern composite materials,it has superiormechanical properties and is widely used in various high-tech fields (such as aviation,aerospace, etc.). It has great significance in the study of mechanical properties of3-D braided composites.The study of the mechanical properties of3-D braidedcomposites has just started, there have many questions need to solve. The microscopicanalysis of braided geometry structure and mechanical properties is be studied. Thispaper include the following three aspects:The first chapter describes the development of3-D braided composites. FromMicro-geometry model,the stiffness performance and interfacial mechanics espects,Mechanical research is described. the purpose and significance of the topics isdescribed in this chapter.The second chapter set yarn model based on real space structure of the fiberbundle composed of three-dimensional braided composites. The set yarn modelcontains a single-cell within the yarn curved model, surface unit cell model and thecorner unit cell model of yarn polyline. Considering the fiber extrusion deformation,the fiber bundles of elliptical cross section is selected. The spatial structure of the fiberbundles is also reduced. Based on this chapter, Especially the geometric model for eachtype of unit cell stiffness averaging and final volume average. Numerical predictionmodel of the effective elastic constants is established, the elastic constants of thematerial is calculated. Numerical prediction results were compared with the test resultdata, the data is basical same, it proves that the model established on this chapter iseffective.The third chapter analyzes the drawing model which established on the structureof the small pieces. Expressions of the fiber axial stress and fiber interfacial shearstress are derived, the main parameters of the model is predict through finite elementsoftware, different loads are also exertd on the model, strain, stress and displacementvariation of fiber are given in different buried in the depth of the stress, strain anddisplacement variation. The calculated stress expression and the stress distributionobtained by simulating is agreement with experiment results, this provs that thistheoretical analysis is accurate.