摘要
为实现天线罩用三维立体织物的近净成形,以头锥体立体特征为依据,角联锁结构为织物基础组织,提出了基于椭圆形纱线截面假设的变厚度层数计算模型和变截面经纱加列模型,并由此建立了织物纤维体积分数的预测模型,完成了头锥体结构织物顶部到薄壁均匀过渡的工艺设计与实验验证.研究结果表明,层数计算模型和经纱加列模型分别实现了织物厚度和织物截面的连续变化,其试织织物的三坐标扫描图与所设计头锥体三维模型相似度达 97.36%,纤维体积分数与预测值误差为 1.84%,验证了变厚度头锥体织物结构设计方案的可行性,并且织造过程中使用沿纬斜方向线密度梯度变化的经纬纱线有利于减小织物内层接线处的摩擦,提高预制体性能.
Abstract
Objective In order to form near-net tapered axisymmetric preform for radome using three-dimensional angular interlocking structure,a layer calculation model and a warp yarn adding model under the assumption of elliptical yarn cross section are put forward based on the analysis of the characteristics of variable thickness and variable cross section of the radome,and a fabric preform of variable thickness rotary cover is woven by combining the three-dimensional weaving technology.Method The three-dimensional characteristics of tapered axisymmetric body with variable thickness were analyzed,and the mathematical model for calculating thickness(weft skew)and number of layers and the warp yarn adding model were established.Firstly,the simulation experiment of warp and weft extrusion state was established,and the regression equations for yarn long and short diameter(a,b)were obtained by response surface analysis.The unit thickness(single layer warp and weft thickness)model along the weft oblique direction was modified.Then,the mathematical model of layers and the model of warp yarn addition were established.Finally,the two models were used to design the number of layers,layer reduction scheme and warp yarn adding scheme of the radome fabric,and the fabric was practically woven to verify the feasibility of the fabric structure design scheme.Results According to the analysis and calculation of the three-dimensional structure of the radome and the fineness as well as density of the selected warp and weft,four symmetrical 2.5D looms were used for weaving.In the weaving process,the regression equations of the long and short axes a and b of the yarn are obtained by determining the working conditions and inputting the horizontal coding of the corresponding factors,and then the number of weft layers was calculated according to the modified unit cell thickness model.When calculating the number of layers,it was determined that the position where the fineness of the warp yarn was reduced was the second weft according to the warp yarn difference rate f,and the number of layers after the thinning of the warp yarn needs to be equal to or less than that of the previous weft yarn due to the difficulty in adding layers.In the case that the predicted value of fabric fiber volume content is much different from the specified value,the yarn fineness would be redesigned.The warp and weft yarns with varying fineness gradient were used to improve the phenomena of ＂tight inside and loose outside＂ and uneven density of the fabric with variable thickness,and to reduce the friction at the yarn connection and reduce the fuzzing phenomenon.After weaving,the cover fabric was scanned in three coordinates,and the obtained three-coordinate scanning map showed 97.36%similarity with the cover model,and the error between the measured value and the predicted value of fabric fiber volume content was as small as 1.84%.The cured fabric was cut to obtain yarn sections in the variable thickness area and the equal thickness area.Conclusion Based on the assumption of elliptical yarn cross-section,this paper makes a geometric analysis of the radome fabric preform with diagonal interlocking structure according to the two characteristics of variable thickness and variable cross-section.Combined with the regression equations of long and short diameters of yarns,the unit thickness model along the weft skew direction is modified,and then establishes the mathematical calculation model of thickness(weft skew)and number of layers and the warp and weft yarn adding model are established,dividing the warp and weft yarn distribution in detail.Through the actual weaving on the machine,the design effect of the model is verified,and the results show the feasibility of the structure and process design of the fabric preform with variable thickness.It can realize the integrated near-shape weaving of the radome of hypersonic aircraft and improve the overall performance of the radome.
维普
万方数据