Sound and vibration damping characteristics in natural material based sandwich composites

Recently, considerable attention has been paid on the utilization of natural materials in structures. Utilizing natural materials over traditional, synthetic structures results in a reduction of carbon emissions from material synthesis; such a source of materials could also be renewable and recyclable. Currently, few reports exist on sound and vibrational properties in sandwich composites with the use of natural materials. Sandwich composites are commonly used in structures for their superior strength and stiffness-to-weight ratios, but from these same properties, they radiate noise efficiently. Here, in this study, the sound and vibration damping properties of natural material based sandwich composites were explored and characterized. It was experimentally observed that utilizing a balsa wood core with a natural fiber based face sheet has a 100% improvement in coincidence frequency, a metric of acoustic performance, and the combination of a natural fiber based face sheet with a Rohacell 51 WF synthetic core exhibits a 233% increase over a fully synthetic sandwich composite. As these improvements in acoustic performance are achieved with only small sacrifices in bending stiffness, these results suggest that, if optimized, natural material based sandwich composites could be an environmentally friendly solution to the sandwich structure-noise radiation problem. (C) 2012 Elsevier Ltd. All rights reserved.