Today's design trends in aeronautics focus on decrease structural weight and increase aerodynamic efficiency in order to reduce emissions. These trends are towards slender aircraft configurations and are consequently prone to aeroelastic phenomena. At the same time composite materials allows to reduce structural weight and they are today's state of the art in aircraft industry. Furthermore, composite materials, with their different possible laminations that allows to induce coupling between bending and twisting deformation, can be exploited to counteract aeroelastic instabilities establishment, a phenomenon called aeroelastic tailoring. In this contest an invariant approach able to normalize stiffness components of every composite material could be tremendous in simplifying composite material design.