Multi-level optimization of aircraft shell structures

Abstract Various aspects of multi-level optimization are reviewed, and the application to problems typical of aircraft wing and fuselage structures is discussed. A three-level optimization is proposed, as this relates in a convenient way to the design of a shell structure in which stiffened panels are assembled into individual cross-sections which are in turn linked together to form the complete structure. Furthermore, the different tasks which the designer has to perform can then retain their separate identity, and a considerable degree of ‘local’ optimization can be carried out. The suitability of multi-level optimization in more complex design problems is tested on a structure representative of a wing box in composite material, with buckling limitations in each panel, and another problem in which aeroelastic requirements are included. Proposals are made for a simplified approach to the sensitivity data used in multi-level optimization.