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    SiCf/SiC复合材料包壳预制体缠绕成型工艺铺层方案的优化

    Optimization of Layering Scheme of Winding Forming Process for SiCf/SiC Composite Cladding Preforms

    • 摘要: 采用缠绕成型工艺在1环向层+1螺旋层、环向层纱宽1.1 mm、螺旋层纱宽0.85 mm、螺旋层缠绕角度±45°、一切点、缠绕张力0~5 N铺层方案下制备SiC纤维(SiCf)/SiC复合材料包壳预制体,根据预制体的壁厚要求(0.45~0.56 mm)、纤维体积分数要求(45%~55%)及表面质量要求确定最优缠绕张力;改变螺旋层纱宽与缠绕角度,计算预制体理论厚度,得到满足壁厚要求的铺层方案并制备预制体,研究了螺旋层缠绕角度和切点数对壁厚、纤维体积分数的影响;预制体进行热解碳、化学气相渗透(CVI)及化学气相沉积(CVD)致密后制成包壳,对比研究了不同铺层方案下所制备包壳的密度、孔隙率、环向和轴向强度,确定了较优的铺层方案。结果表明:最优缠绕张力为3 N,此时预制体表面平整,纱线排布均匀,壁厚为0.5 mm,纤维体积分数为50%;螺旋层缠绕角度越大,包壳表面凸起数量越多,表面质量越差;切点数的增加导致预制体纤维搭接架空增多,对其CVI致密过程有正向作用,所制备包壳的孔隙率降低。满足预制体壁厚要求的铺层方案为1环向层+1螺旋层、环向层纱宽1.1 mm、螺旋层纱宽0.85 mm、缠绕角度±40°、3切点(方案一)以及1环向层+2螺旋层、环向层纱宽1.1 mm、螺旋层纱宽1.35 mm、缠绕角度±35°、3切点(方案二)。铺层方案一下所制包壳的轴向强度及孔隙率未达到指标要求,而铺层方案二下所制包壳的性能满足指标要求,其环向强度为197 MPa,轴向强度为235.2 MPa,孔隙率为6.45%,密度为2.87 g·cm−3

       

      Abstract: The preforms of SiC fiber (SiCf)/SiC composite cladding were fabricated by winding forming process under the layering scheme of one hoop layer + one spiral layer, hoop layer yarn width of 1.1 mm, spiral layer yarn width of 0.85 mm, spiral layer winding angle of ±45°, one cut point, and winding tension of 0–5 N. The optimal winding tension of the preform was determined by the requirements of the wall thickness (0.45–0.56 mm), fiber volume fraction (45%–55%), and surface quality of the preform. By changing yarn width and winding angle of the spiral layer, the theoretical thickness of preforms was calculated, and preform layering schemes that met the wall thickness requirements were obtained. The preforms were prepared, and the influence of the winding angle of the spiral layer and the number of cut points on wall thickness and fiber volume fraction was studied. After pyrolytic carbon, chemical vapor infiltration (CVI) and chemical vapor deposition (CVD) on preforms, the cladding was obtained. The density, porosity, circumferential and axial strength of the prepared cladding under different layering schemes were compared and studied, and the superior layering scheme was determined. The results show that the optimal winding tension was 3 N, and the surface of the preform was flat, the yarns were evenly arranged, the wall thickness was 0.5 mm, and the fiber volume fraction was 50%. The larger the spiral layer winding angle, the greater the the amount of protrusions on the surface of the cladding, and the poorer the surface quality. The increase in the number of cut points led to more fiber bridging and voids in the preform, which had a positive effect on CVI densification, and the porosity of the prepared cladding decreased. The layering schemes that met the preform wall thickness requirement were one hoop layer + one spiral layer, hoop layer yarn width of 1.1 mm, spiral layer yarn width of 0.85 mm, winding angle of ±40°, and three cut points (Scheme 1), and one hoop layer + two spiral layers, hoop layer yarn width of 1.1 mm, spiral layer yarn width of 1.35 mm, winding angle of ±35°, and three cut points (Scheme 2). The axial strength and porosity of the prepared cladding under Scheme 1 did not meet the index requirements, while the performance of the prepared cladding under Scheme 2 met the index requirements, with a hoop strength of 197 MPa, an axial strength of 235.2 MPa, a porosity of 6.45%, and a density of 2.87 g·cm−3.

       

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