Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Study of the sound absorption of two composites made with polyurethane and natural fiber layers at low frequency using an impedance tube.
Submission Author:
Key Fonseca de Lima , PR , Brazil
Co-Authors:
CLAUDIA BITTENCOURT, Ana Carolina Mendonça Mansur, Marco Zeschotko, Fernando Jun Hattori Terashima, Nilson Barbieri, Key Fonseca de Lima
Presenter: CLAUDIA BITTENCOURT
doi://10.26678/ABCM.COBEM2023.COB2023-2187
Abstract
Porous synthetic materials with low density are often used for acoustic surface treatment because they have high sound absorption. In the last decade, so-called green materials have been emerging ground in research in the noise control field. For example, natural fibrous material from agricultural waste or a by-product from another industrial transformation process. However, they do not have the same efficiency when compared to synthetic materials. To improve the acoustic performance of natural fibers, it is necessary to add some synthetic material together with the fibers, forming a composite. In this work, samples of thin composites classified as eco-friendly made by polyurethane (isocyanate + polyol obtained from sugar cane) and coconut coir husk and sugar cane bagasse fibers bonded with polyvinyl acetate (common white glue). The two materials involved were arranged in layers and glued with white glue. Ten samples of each material with a diameter of 100 mm were made. In addition, they were manufactured with polyurethane and fiber thicknesses of 5 and 10 mm, respectively. The sound absorption coefficient of the samples was evaluated between 180 and 1600 Hz, with the transfer function method based on the ASTM E1050 standard. The samples were inserted inside the tube so that the incidence of the sound waves occurred on the polyurethane face and with the fiber side on the rigid termination. The results showed that the addition of polyurethane increased the sound absorption in the range between 800 and 1000 Hz of the composites created in comparison with the samples formed only by natural fibers. When evaluating the results, fluctuations appeared in the sound absorption curves caused by the vibration of the composite when excited by the sound waves inside the impedance tube. This phenomenon does not occur when the samples are made only with natural fibers.
Keywords
sound absorption, Polyurethane, Natural Fiber, Coconut fiber, sugar cane bagasse fiber, transfer function method
