Modal Analysis of a Flexible Membrane Wing of Micro Air Vehicles

A biologically inspired flexible wing for micro air vehicles applications is constructed with a prestrained latex membrane, attached to a thin aluminum ring with elliptical planform shape. The wing is placed inside a low-speed wind tunnel and the strains of the membrane due to the aerodynamic loads are measured using the visual image correlation technique at different angles of attack and freestream velocities. Finite element models are developed for investigating the modal characteristics of the wing including the effect of added mass, damping, and aerodynamic loads. For validating the finite element models, experimental modal analysis of a prestrained membrane is conducted inside a vacuum chamber at different ambient pressures. Natural frequencies of the wing increase with mode and strain level of the membrane, but decrease in air from those in vacuum, due to the added mass of air. Damping of air is low and has minimal effect on the natural frequencies of the wing, but assists to reduce the out-of-plane modal amplitude of vibration.