Micro Geometry And Mechanical Model And Experimental Study Of2.5D Braided Quartz/SiO₂Ceramic Matrix Composites

Continuous fiber-reinforced quartz/SiO₂ceramic matrix composites （CMCs） can be widely usedin RF window and warhead of a missile for the combination properties of stable dielectric at hightemperature; it is regarded as the most promising next-generation high-temperature wave-transparentmaterials. This study concerns experimental and theoretical estimates through analyzingshallow-straight-joint braided and shallow-bend-joint braided structure. In this paper, all the researchcan be divided into three parts:First, the micro-geometry model of shallow-straight-joint braided and shallow-bend-joint braidedstructure were analyzed through describing the representative unit cell. Prediction results werecalculated by matlab software. To check accuracy of micro-geometry model, the comparison betweenprediction and experimental results is necessary and is meaningful for study effect of fabricgeometrical parameters on fiber volume fraction.Second, a new mechanical model of2.5D braided quartz/SiO₂CMCs was established. On thebase of built micro-geometry model, stiffness matrixes of warp and weft yarns were studied. Hybridmethod was adopted to obtain stiffness matrixes of the composites. Finally, we can get thestress-strain relationship of composites. Similarly, Prediction results of linear elastic constants wereworked out by matlab software.Third, we also did the experimental research of the2.5D braided composites.2.5D braidedcomposites were prepared by SIS method and tested by tensile, flexural and shear property to obtainexperimental results of linear elastic constants. To check accuracy of micro-mechanical model, thecomparison between prediction and experimental results is necessary. Experimental results and theeffect of fiber volume fraction on linear elastic constants are also studied in this paper.From the above three part, we can get mechanical prediction model of2.5D braided quartz/SiO₂CMCs, and the relationship between the parameters for materials, which can provide theory basis forthe engineering application.