a) HSCT Wing External Geometry a) Cylindrical Fuselage Panel With Curvilinear Stiffeners
b) Buckling Mode of Optimized Panel
Fig. 2: Optimization Cylindrical Fuselage Panel under Multiple Load-cases
b) A Sample Internal Wing Structure for HSCT
Fig. 3: Curvilinear SpaRibs for Supersonic wing
c) Von Mises Stress Distribution for Optimized Panel
heights of the stiffeners. Figure 1-a shows the flat rectangular optimized panel designed using EBF3PanelOpt. During the optimization of this panel, non-uniform thicknesses for panel pockets were used. In Figure 1-b, it can be seen that all panel pockets are in the process of buckling, and Figure 1-c shows the von Mises stress distribution for the applied load. Figure 2 shows an optimized cylindrical fuselage panel under multiple load-cases, von Mises stress distribution and buckling mode shape. A tool called EBF3SSWingOpt is also in development to utilize curvilinear spars and ribs to optimize supersonic wings. In this framework, Patran, MSC Nastran, VisualDoc and MATLAB are integrated to optimize supersonic wings. EBF3SSWingOpt has the capability to optimize the wing using curvilinear spars and ribs (SpaRibs) for static aerodynamic loads against bucking and von Mises stress. Curvilinear SpaRibs redistribute the loads and changes its buckling modes as well as vibration modes so that one can control aeroelastic behavior and static behavior. Currently, EBF3SSWingOpt uses the ‘Translation’ utility of Patran to generate SpaRibs, and it adds the optimal number of SpaRibs in the wing based upon the bounds of translation parameters given by the user.
Figure 3 shows the example of curvilinear SpaRibs inside High-Speed Civil Transport (HSCT) aircraft. This framework has the flexibility to put SpaRibs in the selected area by the user. Using this framework, Freedom Fighter’s wing is optimized; the comparison of the optimized wing with its original design is shown in Fig. 4. The work of EBF3PanelOpt is funded under NASA Subsonic Fixed Wing Hybrid Body Technologies NRA Contract (NASA NNL08AA02C) with Ms. Karen M. Brown Taminger as the API and COTR and Richard Keith Bird as the Contract Monitor. The authors would like to thank our partners in the NRA project, Mr. David Havens, Mr. Robert J. Olliffe, and Dr. Steve Engelstad, all from Lockheed Martin Aeronautics Company of Marietta, GA, for their contribution in the present research. Unitized Structures Group at VT would like to thank Ms. Marcia S. Domack (Technical Monitor) of NASA Langley Research Center for substantial technical discussions. EBF3SSWingOpt was conducted as a subcontract from the National Institute of Aerospace, Hampton, Virginia. We would also like to thank Mr. John E. Barnes, Mr. Ryan J. Wittman and Mr. Agustin Garcia, all from Lockheed Martin Aeronautics Company for their technical inputs.
a) EBF3SSWingOpt Design
b) Freedom Fighter Design
Fig. 4: EBF3SSWingOpt Design of Freedom Fighter Wing
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Volume 1 - Winter 2011
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