Preliminary structural design optimization of an aircraft wing-box

Structural weight has always been important in aircraft manufacturing industry. Considering that a large number of candidate material and geometric shapes are available early in the design cycle, preliminary design optimization of skin-stringer panels used to build an aircraft wing is required to obtain the best preliminary structure before the final design phase. The design of skin-stringer panels forms an important and major portion of the wing-box design. The lift generated by the wings opposes the weight of the aircraft, and thus generates bending. Depending on their location, stiffened panels that make up the wings are therefore mainly loaded in compression and tension. Upper skin-stringer panels are typically subjected to compressive load while the lower panels are subjected to tensile load. The ability to resist the compressive load is assessed through a stability study to compute the critical buckling load of the stiffened panel while the ability to withstand the tensile load is evaluated by the Damage Tolerance Analysis. Optimization routines have been developed for the design of upper and lower wing panels. The main objective here is to design a stable wing-box structure more rapidly and automatically in the most economical manner having adequate strength and stability. These optimization routines are tested on a wing section defined at a specific span wise location of a DLR-F6 aircraft. Repeating the design process at different stations along the wing span completes the preliminary design of aircraft wing-box