Buckling optimization of variable stiffness composite rotary shell under combined loads
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摘要: 通过曲线纤维轨迹设计,变刚度复合材料回转壳将拥有比常刚度(直线纤维)回转壳更好的抗屈曲稳定性,为此,研究了复合载荷作用下曲线纤维铺层形式和几何参数对变刚度复合材料回转壳屈曲性能的影响规律。首先根据回转壳横截面圆弧变化改进曲线纤维角度线性描述方法,建立了变刚度复合材料回转壳的参数化有限元模型;其次,结合序列二次响应面方法和回转壳屈曲优化模型,搭建了复合材料回转壳曲线纤维轨迹优化的设计流程;最后,以准各向同性铺层复合材料回转壳为比较基准,对弯扭载荷作用变刚度圆柱壳和轴压、弯矩和扭矩分别作用变刚度椭圆柱壳在不同铺层方式、不同几何参数下的屈曲性能进行了优化比较。结果表明:弯扭载荷作用下,变刚度圆柱壳的屈曲性能随弯矩载荷占比增加而提高,且均好于准各向同性圆柱壳,但扭矩载荷占优时,优化常刚度圆柱壳的屈曲性能更具有优势;不同载荷作用下,具有较小截面方向比的变刚度椭圆柱壳屈曲性能要明显好于对应的准各向同性椭圆柱壳,且横截面越接近圆形,曲线纤维对椭圆柱壳屈曲性能的改善越弱。Abstract: By designing curvilinear fiber trajectory, composite rotary shell with variable stiffness (VS) has more excellent buckling resistance than straight-fiber shell with constant stiffness (CS). This work studies the influence of ply patterns and geometrical parameters on buckling performance of composite rotary shell under combined loads. Firstly, directional arc of the cross section of rotary shell was used to describe the linear variation of fiber angle, and based on this, a parametric finite element model of VS rotary shell was established. Secondly, for the purpose of achieving the maximum buckling capacity, the fiber trajectory of the composite rotary shell was optimized by combining the sequence quadratic response surface method (SRSM) with the rotary shell model. Finally, effects of ply patterns and geometrical parameters on both the cylindrical shells with bending-torsion load and the elliptical cylindrical shells with axial compression-bending-torque load were studied. It is found that the buckling capacity of VS composite cylindrical shell increases with the increase of the proportion of bending moment, and this is better than the quasi-isotropic (QI) cylindrical shells. However, when the torsional moment is the dominant factor, the buckling performance of the optimized CS cylindrical shell shows more advantages. The buckling performance of the elliptical VS cylindrical shell with smaller ratio of radius is obviously better than that of the QI cylindrical shell under different loads. The closer the cross-section is to a circle, the weaker the improvement of the buckling performance of the elliptical cylindrical shell by the curvilinear fiber.
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Key words:
- variable stiffness composite /
- composite rotary shell /
- buckling optimization /
- combined load /
- FEA
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