Design and testing of aeroelastically tailored composite wing under fatigue and gust loading including effect of fatigue on aeroelastic performance

The aim of the paper is to experimentally validate a numerical design methodology for optimizing composite wings subject to gust and fatigue loading requirements and to assess the effect of fatigue on the aeroelastic performance of the wing. Traditionally, to account for fatigue in composite design, a knockdown factor on the maximum stress allowable is applied, resulting in a conservative design. In the current design methodology, an analytical fatigue model is used to reduce the conservativeness and exploit the potential of composite materials. To validate the proposed analytical model, a rectangular composite wing is designed and manufactured to be critical in strength, buckling and fatigue. An experimental campaign comprising wind tunnel and fatigue tests is performed. In the wind tunnel, both static and dynamic aeroelastic experiments are conducted to validate the numerical dynamic aeroelastic model. The fatigue test is used to validate the analytical fatigue model and to understand the effect of fatigue on aeroelastic properties of the wings. The results from experimental campaign validated both the aeroelastic predictions as well as fatigue predictions of the numerical design methodology. However the fatigue process resulted in degradation of the wing stiffness leading to change in the aeroelastic response of the wing.