Parametric instabilities of camber morphing wing structure with time-varying stiffness

Morphing wings with variable stiffness structures are a promising concept to improve aircraft performance. However, this can induce parametric instabilities, which have to be studied to avoid failures. A three-degree-of-freedom wing with periodically time-varying stiffness is used for this study. The resulting equation of motion resembles a coupled Mathieu equation with unsteady aerodynamic loads. The parametric instability of the wing is analyzed numerically using the Floquet theory. In this abstract, specifically, the effect of out-of-phase stiffness variation is investigated. It is found that a 180-degree phase difference in the flap stiffness variation reduces the primary parametric instability regions. However, it introduces a new combination instability region.