We present a hybrid, semi-analytical approach to perform an eigenvalue-based flutter analysis of an Unmanned Aerial Vehicle (UAV) wing. The wing has a modern design that integrates metal and composite structures. The stiffness and natural frequency of the wing are calculated using a Finite Element (FE) model. The modal parameters are extracted by applying a recursive technique to the Lanczos method in the FE model. Subsequently, the modal parameters are used to evaluate the flutter boundaries in an analytical model based on the p-method. Two-degree-of-freedom bending and torsional flutter equations derived using Lagrange’s principle are transformed into an eigenvalue problem. The eigenvalue framework is used to evaluate the stability characteristics of the wing under various flight conditions. An extension of this eigenvalue framework is applied to determine the stability boundaries and corresponding critical flutter parameters at a range of altitudes. The stability characteristics and critical flutter speeds are also evaluated through computational analysis of a reduced-order model of the wing in NX Nastran using the k- and pk-methods. The results of the analytical and computational methods are found to show good agreement with each other. A parametric study is also carried out to analyse the effects of the structural member thickness on the wing flutter speeds. The results suggest that changing the spar thickness contributes most significantly to the flutter speeds, whereas increasing the rib thickness decreases the flutter speed at high thickness values.

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The thrust of increasing environmental and economic constraints on aircraft has enthused accelerated research in design of more economical and higher performance aircraft. Extensive experience in aerodynamic has established the use of high aspect ratio wings to improve the lift-to-drag ratio, a key parameter in determination of aircraft efficiency. Application of long slender wings has even more so intensified in the last decade due to emerging need for medium-to-high altitude long endurance (MALE/HALE) unmanned aerial vehicles (UAVs). However, such a wing comes at a trade-off of efficiency and safety. Longer wings tend of be more flexible and easily deform under load, hence are more vulnerable to the detrimental nature of aeroelastic effects. Divergence, control reversal and flutter are some major aeroelastic effects, which range from mere discomfort to complete destruction of body in flight. UAVs are most susceptible to this behaviour as their design incorporates very high aspect ratio wings. Numerous researches are available in literature which have focused on the explanation, calculation, and suppression of aeroelasticity; a subject which is as old as first heavier-than-air flight. This paper has attempted to cover the major aspect of aeroelasticity and summarize the state-of-the-art methods and approaches proposed by esteemed authors in this field for flutter prediction and suppression.