Experimental and Finite Element Modal Analysis of the Flexible Wings of Micro Munition Vehicles

Biologically inspired wings of micro munition vehicles are constructed with the pre-strained hyperelastic membrane, attached with composite reinforcing structures. Finite element models are developed for the modal characteristics of the flexible wings of micro munition vehicles and validated by experimental results. The effect of added mass, damping, and aerodynamic loads on the modal characteristics (natural frequencies and mode shapes) of the wings is investigated. The wings are vibrated in the vacuum and air environments for investigating the effect of added mass and damping on their modal characteristics. Aerodynamic loads are calculated from the wind tunnel test data where the angle of attack of the wings and free stream velocity of air are varied. Natural frequencies increase with mode, pre-strain level of the membrane, and aerodynamic loads but decrease in air from those in the vacuum environment due to the added mass of air. Damping of air is low and has minimal effect on the natural frequencies of the wings but helps to reduce the out-ofplane modal amplitude of vibration. The effect of added mass, damping, and aerodynamic loads on the mode shapes of the wings is also presented in the paper.