Natural material based sandwich composites with enhanced noise mitigation

While sandwich structures boast high mechanical performance at a low weight, their acoustic performance is undesirable as they efficiently radiate noise at lower vibrational frequencies compared to metal structures. Moreover as there are increasingly growing interests in seeking structural materials which are environmentally friendly, natural fiber based composite materials could be a viable alternative. Considerable attention has been paid for their use in various engineering applications such as the automotive industry. Natural fibers such as cotton and bamboo are a renewable resource which can be grown for the production of natural composite materials. Through a combination of experimental and analytical methods, this study reports that the acoustic properties of sandwich composite beams can be improved up to 275% by utilizing natural materials over traditional carbon fiber sandwich composites by characterizing their vibrational responses. These results show promise for the use of natural materials in sandwich composite structures with significantly improved noise mitigation performance. This improvement is achieved without sacrificing flexural stiffness of the sandwich composite materials. In this study, cotton-vinyl ester, bamboo-vinyl ester and carbon fiber-epoxy were used as face sheets along with various synthetic and natural core materials for the investigation of the acoustic performance of sandwich composite beams.