Development of a Framework for Design Optimization of Planar Panels Using Curvilinear Stiffeners

Innovative manufacturing techniques like Electron Beam Free Form Fabrication (EBF3), Friction Stir Welding (FSW), and Selective Laser Sintering (SLS) are additive in nature as opposed to subtractive. These techniques have created new opportunities and a much bigger design space to optimize structures of complex shapes especially the aerospace vehicles. New types of pressurized non-circular fuselage structures within hybrid wing/body vehicles that undergo complex structural load cases are not well characterized using current design databases. Therefore, a new framework is being developed for design and optimization of complex multifunctional aircraft structural concepts called EBF3PanelOpt.  This tool can be used to integrate materials and structural concepts to exploit emerging additive manufacturing processes that offer the ability to efficiently fabricate complex structural configurations.  The ultimate goal is to enhance structural performance through reductions in weight, emissions, and cabin noise, and to integrate functions such as acoustic damping, adaptive active aerodynamic controls, and aeroelastically tailored structures.     

Commercial softwares, Msc.Patran (geometry modeling and mesh generation), Msc.Nastran (Finite Element Analysis), VisualDoc (external optimizer) are integrated in EBF3PanelOpt framework using the Python programming environment to design stiffened panels. Earlier research has shown that panels with curvilinear stiffeners may have a reduced weight than panels with straight stiffeners having the same strength performance.  Currently, this framework allows the user to optimize flat multi-sided panels with straight/curved edges having curvilinear, blade-type stiffeners. The mass of the panel is minimized subjected to constraints on buckling, Von Mises stress, and crippling or local failure of the stiffener using global optimization techniques like Particle Swarm Optimization (PSO) or gradient based optimization techniques. The panel/stiffener geometry is defined by a parametric panel definition based on design variables that include design variables for orientation and shape of the stiffeners, the thicknesses and height of the stiffeners, and a discrete number of panel/plate pocket thicknesses.    

In this paper, the optimization of flat rectangular panel is carried out utilizing EBF3PanelOpt framework for a combined compression-shear load case that was provided by Lockheed Martin Aeronautics Company. Additionally, optimization will be carried out for a panel having curvilinear edges under the same load case in EBF3PanelOpt framework.