P. Gasbarri, L.D. Chiwiacowsky, H.F. de Campos Velho (2008): A Hybrid Multilevel Approach for Aeroelastic Optimization of Composite Wing-box, International Conference on Engineering Optimization, June 1-5, Rio de Janeiro, Brazil.

Abstract: The quest for finding optimum solutions to engineering problems has existed for a long time. In the last decade several optimization techniques have been applied to structural design of wing composite structures. Generally many of these proposed procedures have dealt with different disciplines such as aerodynamics, structures, or dynamics separately. However an aeronautical design process is multidisciplinary involving strong couplings and interactions between, for instance, aerodynamics, dynamics, flight mechanics and structures. For this reason it is very important to take into account of these interactions also during a preliminary design of a modern aircraft and hence, the relevant optimization procedures must consider different disciplines simultaneously rather than separately. Techniques and strategies for merging disciplines in order to obtain, for instance, aircraft structural optimization, are current subjects under research and development. Generally the main problem in a multidisciplinary aircraft design is the development of an efficient method to integrate structures or structural properties, which can be considered both as global; and local; design variables. This paper describes an integrated aerodynamic/dynamic/structural optimization procedure for a composite wing-box design. The procedure combines an aeroelastic optimization of a composite wing based on a general purpose optimizer such as the Sequential Quadratic Programming (SQP) and a composite optimization using Genetic Algorithm (GA). Both the optimization are implemented through a multilevel decomposition technique. At the upper level, the wing composite structure is represented in terms of global quantities (e.g. stiffness, mass, anisotropicity parameters of composite materials, and average strain). At the lower level, the wing structure is represented as a composite laminate whose local quantities are the thicknesses and the orientation of the layers which constitute the laminate. The procedure here proposed is an attempt to provide an optimization technique of tailored composite structures that is compatible with industrial design practices in which, for instance, the aerodynamic, the dynamic or the aeroelastic design are performed at a global level and the structural design is carried out at a detailed level, generally with a compromise among the different disciplinary groups. This procedure is demonstrated for several numerical cases.