EBF3PanelOpt: An Overview and Recent Developments of An Optimization Framework for Stiffened Panel Using Curvilinear Stiffeners

For the last four years, an optimization framework, EBF3PanelOpt, is being developed to design panels with curvilinear stiffeners so as to utilize the larger design space made possible by direct digital manufacturing that uses additive manufacturing techniques like the Electron Beam Free Form Fabrication, Friction Stir Welding, and Selective Laser Sintering. Structural loads of future aerospace vehicles may not be well characterized using current knowledge-based databases, so medium-fidelity software like Msc.Patran (geometry modeling and mesh generation), Msc.Nastran (Finite Element Analysis) are integrated in EBF3PanelOpt framework using the Python programming environment. Earlier version of the EBF3PanelOpt supported curvilinear blade stiffeners without loads acting through the stiffeners to optimize the panels for minimum mass subjected to buckling, von Mises stress, and crippling or local failure of the stiffener constraints. EBF3PanelOpt is enhanced to have curvilinear T and L stiffeners with or without axial loads in addition to the loads acting only on the panel. The panel/stiffener geometry is defined in a parametric fashion based on design variables that include variables for orientation and shape of the stiffeners. This framework is modified to support a coarse-grained parallelism to analyze multiple designs on the cluster. This framework can easily be coupled with any optimizer like VisualDOC, DAKOTA or MATLAB. A vertical stabilizer skin panel of transport aircraft panel having two extreme load-cases, is optimized using with or without stiffener loads. The optimization results are compared with the current industry practice leading to a 17% reduction in the panel mass for an example panel.