Sound-absorbing and thermal insulating properties of natural coir/jute hybrid composites for functional materials

Abstract

A composite designed for soundproofing integrates both sound absorption materials and thermal insulation, combining the benefits of both into a single product. The absorption component serves to dissipate energy within the system, while the noise barrier reduces the transmission of sound. This study focuses on experimentally assessing the sound absorption coefficients of hybrid composite materials composed of coir and jute fibers, reinforced with epoxy resin, using compression molding techniques. Six different composite samples were prepared with varying blend proportions of these fibers: S1 Coir/100, S2 Jute/100, S3 Coir/Jute 50/50, S4 Coir/Jute 70/30, S5 Coir/Jute 30/70, and S6 Coir/Jute 60/40, following the standards set by the American Society for Testing and Materials (ASTM). The physical and morphological properties of the samples were examined using a Scanning Electron Microscope (SEM), while the sound absorption coefficients (SAC) were measured via the impedance tube method, following ASTM E (1050), and Thermal insulation values were measured according to Lee’s disk method (ASTM C177). The experimental results show the thermal resistance performances of natural fiber composites based on coir/jute fiber materials, is S5 C/J (0.156 W/mK) and S6 C/J (0.146 W/mK), and there is an improvement in thermal conductivity when compared to the rigid polyurethane foam, which is one of the most efficient thermal insulators. Across frequencies ranging from 1600 to 5000 Hz. The results indicated that the composite sample S4 C/J exhibited exceptional performance in absorbing high-frequency sound waves, particularly above 2500 Hz. Furthermore, it was observed that increasing the thickness of the S6 C/J composite could significantly enhance its sound absorption coefficient at medium and low frequencies. These findings underscore the potential of coir and jute fiber-based composites as effective sound-absorbing materials. Notably, these composites exhibit sound absorption coefficients exceeding 0.83%, showcasing their promising acoustic properties. Additionally, the utilization of natural fibers such as coir and jute, sourced from renewable materials, offers advantages of affordability, biodegradability, and recyclability, making them sustainable choices for soundproofing and thermal insulating materials.