Control of aeroelastic instabilities through stiffness cross-coupling

An idealized aeroelastic tailoring model is developed to assess the effects of significant changes in directional stiffness orientation upon the flutter and divergence behavior of swept and unswept wings. A nondimensional stiffness cross-coupling parameter is used to illustrate the potentially strong influence of stiffness cross-coupling, commonly present in aeroelastically tailored structures, to increase flutter and divergence speeds. Conflicting requirements for flutter and divergence enhancement are indicated. Aeroelastic tailoring for flutter enhancement appears to be less effective when the wing is moderately swept back. However, by combining directional stiffness orientation with inertia balancing, flutter and divergence-free, aft-swept, high-aspect-ratio surfaces are shown to be theoretically possible.