The effect of elastic couplings and material uncertainties on the flutter of composite high aspect ratio wings

Abstract

In this paper, the stochastic aeroelastic stability analysis of a composite high aspect ratio wing with various elastic couplings is investigated. The wing consists of a rectangular spar-box made from composite materials. Due to its high aspect ratio, the wing structure is modelled using the exact beam formulation, and the aerodynamic loads acting on the wing are simulated using an unsteady lifting line theory. A composite spar-box cross section is considered, and the effect of various effective parameters on the aeroelastic stability of the wing is studied. First, a baseline composite wing is designed and the effect of three different elastic couplings on the stability of the wing is determined. These three elastic couplings that affect the aeroelastic design of the composite wing are the out-of-plane (flap)-twist, the in-plane (lag)-twist and the extension-twist. Furthermore, the effect of uniformly distributed load on the aeroelastic stability of the wing is assessed for various layups. Finally, the effect of material uncertainties on the aeroelastic stability of the composite wing with various couplings is studied. It is observed that the type of elastic coupling has a significant effect on the sensitivity of the flutter speed and frequency of the composite wing due to the randomness of the material properties. In particular, the aeroelastic behaviour of the wing with lag-twist coupling is more sensitive to the material uncertainties than other two layups.