Experimental and Finite Element Modal Analysis of a Pliant Elastic Membrane for Micro Air Vehicles Applications

Abstract

This paper investigates the modal characteristics of a latex membrane for micro air vehicles applications. Finite element (FE) models are developed for characterizing the latex membrane at dynamic loading and validated by experimental results. The membrane at different pre-tension levels is attached to a circular steel ring, mounted on a shaker, and placed inside the vacuum chamber for modal characterization using a scanning laser Doppler vibrometer (LDV). The experimental modal analysis is conducted by imposing a structural excitation to the ring for investigating the membrane vibration characteristics at both atmospheric and reduced pressures in a vacuum chamber. FE models are developed for the natural frequencies of the membrane at different uniform and non-uniform pre-tension levels with the effect of the added mass of air. The Mooney-Rivlin hyperelastic material model is selected for the membrane. The natural frequencies of the membrane computed by experimental and FE models are correlated well, although discrepancy is expected among experimental and FE results within reasonable limits due to the variation of the thickness of the membrane. The natural frequencies increase with the mode and pre-tension level of the membrane but decrease due to an increase in ambient pressure. The damping ratios have very minimal effect on the frequencies due to low values but help to reduce the amplitude of vibration. Natural frequencies of the membrane do not change with the uniform and non-uniform nature of the pre-tension, although they increase with the pre-tension level. It is also found that the effect of added mass on the natural frequencies increases with an increase of the size of the membrane specimen.