Aeroelastic behavior of a parameterized sailplane wing using Tsai’s Modulus

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. Such invariant approach was not possible until Tsai and Melo published in 2014 their results about a novel invariant approach to describe elastic properties of composites plies and laminates. In this approach the trace of the plane stress stiffness matrix, namely Tsai's Modulus, is evaluated as a material property. Relatively to this, the present thesis aims to exploit the potentiality of this newly discovered invariant in the field of aeroelasticity. In particular, a finite element parametric sailplane wing model will be built to analyze flutter and divergence behaviour as function of material Tsai's Modulus. Since the focus is on composite materials 2D orthotropic plate elements parameterized as function of Tsai's Modulus will be used for the FEM model. For aerodynamics loads evaluation the vortex lattice method (VLM) and doublet lattice method (DLM), two of the most powerful tools for linear aeroelastic analysis in subsonic regime, will be used respectively for steady and unsteady aerodynamics. Since Tsai's Modulus essentially is a measure of material' stiffness, given that the aeroelastic behaviour of a wing is inherently tied to its bending, torsion, and shear properties, it logically follows that it should also be influenced by Tsai’s modulus of the material it is constructed from. Consequently, the primary objective of this thesis is twofold: first, to empirically verify the validity of this hypothesis, and secondly, if substantiated, to delineate the correlation between flutter behavior and Tsai’s modulus. This investigation will be undertaken by conducting comprehensive parametric flutter analysis on the specified wing. Should this hypothesis stand true, it implies that the process of wing design can be streamlined. Initial steps would involve identifying the optimal lamination sequence for the wing. Subsequently, the choice of the most suitable material becomes a straightforward task, contingent upon the desired flutter velocity.