Optimal Supersonic Wing Structure Design Using Curvilinear Spars and Ribs (SpaRibs)

Supersonic aircraft design is characterized by major interactions among different disciplines: namely, structures, aerodynamics, thermal effects and flight dynamics. Hence, designing such aircraft requires severe constraints or requirements on the static and dynamic behavior of the structure. These requirements can only be met with the implementation of innovative design concepts during the early design phase. This research illustrates how the use of curvilinear spars and ribs, SpaRibs, can be advantageous for designing supersonic transport aircrafts. The primary benefit of using curvilinear stiffening members in the fabrication of wing-box structures is the coupling between bending and torsion deformations which provides a more efficient load-bearing mechanism. Moreover, the use of SpaRibs provides an enlarged and more flexible design space as compared to conventional design concepts. The mathematical parameterization used to describe the geometry of the SpaRibs is presented. In particular, the shape of the stiffening members is defined using third-order B-splines. The SpaRibs concept is applied to the design optimization of a supersonic transport aircraft. Aerodynamic loads are computed for critical maneuvers using doublet-lattice and ZONA51 methods implemented in MSC.NASTRAN. Static and buckling analyses are subsequently performed to check for maximum stress and instability constraints. Divergence and flutter velocities are also computed using MSC.NASTRAN and included as constraints of the design. A comprehensive set of results is presented, showing the optimum configuration using SpaRibs, the stresses, and the deformation of the structure under computed flight loads and the aircraft flutter envelope.