Wave number and damping characterization for sound and vibration mitigation in sandwich composite structures

Abstract

With the rising demand for high performance composite materials, there is a great interest for multi-functional materials. Our research focuses on materials with high noise mitigation and passive structural damping with minimal sacrifice in bending stiffness. Specifically, we seek to understand the vibrational properties of carbon-fiber face sheet sandwich beams, with interest in wave number and damping characteristics. Both experimental and analytical methods were applied to characterize the wave number response of sandwich beams, from which coincidence frequencies were obtained. From the same frequency response function, structural damping ratios were calculated using the half-power bandwidth method. Results showed that for low frequency applications, decreasing bending stiffness has the greatest effect on increasing the coincidence frequency. However for higher frequency applications, an improvement in coincidence frequency can be seen if one reduces the core's shear modulus. Moreover it may be concluded that the high amplitudes seen in the wave number domain may be contributed to the lower structural damping values at low frequencies. With both wave number and damping properties being frequency dependent, one can optimize design parameters pertaining to a certain frequency range which will improve damping and acoustic properties while maintaining necessary flexural stiffness.