Dynamic property characterization of polyurea aerogel materials using a laser Doppler vibrometer

Abstract

This project seeks to characterize the dynamic material properties of a cross-linked, nanoscale, polyurea aerogel utilizing a new transfer function method. This method is able to determine the dynamic properties over a wide frequency range using impulse responses gathered from the top and bottom of the material by both accelerometers and a laser Doppler vibrometer. The dynamic material properties that can be calculated using this method include Young's modulus, density, and the speed of sound in the material. Different mounting systems for the shaker and the effect of test sample surface area and thickness will be examined. A method for using two different thicknesses of aerogel to resolve the material's dynamic stiffness was discovered. The advantages and disadvantages of using a laser Doppler vibrometer instead of an accelerometer will be studied. The data found that using smaller, circular plates and directly mounting the shaker to a marble floor resulted in the widest usable frequency range. A very low speed of sound was found for the material and confirmed using data from transmission loss measurements.