3410. Initial Sizing Optimization of Anisotropic Composite Panels with T-Shape Stiffeners

Paper

Abstract

This paper provides an approach to perform initial sizing optimization of anisotropic composite panels with T-shape stiffeners. The method divides the optimization problem into two levels. At the first level, composite optimization is performed using Mathematical Programming (MP), where the skin and the stiffeners are modeled using lamination parameters accounting for their anisotropy. Skin and stiffener laminates are assumed to be symmetric, or mid-plane symmetric laminates with 0, 90, 45, or -45 degree ply angles. The stiffened panel is subjected to a combined loading under strength, buckling, and practical design constraints. Buckling constraints are computed using Closed Form (CF) solutions and energy methods (Rayleigh-Ritz). Conservatism is partially removed in the buckling analysis considering the skin-stiffener flange interaction and decreasing the effective width of the skin. Furthermore, the design and manufacture of the stiffener is embedded within the design variables. At the second level, the actual skin and stiffener lay-ups are obtained using Genetic Algorithms (GAs), accounting for manufacturability and design practices. This two level approach permits the separation of the analysis (strength, buckling, etc), which is performed at the first level, from the laminate stacking sequence combinatorial problem, which is dealt efficiently with GAs at the second level.