Grid-Stiffened Panel Optimization using Curvilinear Stiffeners

摘要

Most of the time, grid-stiffened panels utilize straight stiffeners and their use is limited to fuselage structures. Their design is strongly dependent upon the manufacturing constraints like cost and lead time. Manufacturing techniques like Electron Beam Free Form Fabrication (EBF3), Friction Stir Welding (FSW) and Rapid Manufacturing techniques have created new opportunities and much bigger design space to optimize structures of complex shapes especially the aerospace vehicles panels which might be grid-stiffened using curvilinear (alignment) stiffeners. A framework is developed to minimize the mass of panels stiffened by blade stiffeners and subjected to constraints on buckling, von Mises stress, and crippling or local failure of the stiffener using global and/or gradient based optimization techniques. The stiffeners are defined in a parametric fashion using a set of design variables that include the orientation, the shape of the stiffeners, and the spacing between the stiffeners. Other design variables are the stiffeners' thicknesses and heights, and the plate thickness. Using this framework, three rectangular flat panels, similar to the ones used in practical applications, are optimized for different loading conditions. The optimal designs are governed by the location, size, curvature and the spacing between the stiffeners. The optimal spacing between the stiffeners is strongly dependent upon the minimum gauge manufacturing constraint and the applied loads. So, this framework has the flexibility to design traditional grid-stiffened panels as well as the optimal grid-stiffened panel with curvilinear stiffeners.