Effect of natural fibre reinforcement on the sound and vibration damping properties of bio-composites compression moulded by nonwoven mats

Biodegradable natural fibre composites are increasingly developed for lightweight structural applications in automobile and construction industries with significant environmental benefit. This work aims to explore the sound and vibration properties of natural fibre composites that inevitably suffer menace of vibrations during their operations as engineering structures. Natural fibres (bamboo, cotton, flax) and polylactic acid (PLA) fibres were blended, carded, laid up and finally needle-punched to nonwoven mats before being consolidated at elevated temperature under compression. Vibration damping and acoustic measurements were conducted on these natural fibre composites and their behaviour was compared to that of a commercial panel, made of polypropylene (PP) matrix reinforced with hemp and kenaf fibres. From both the coincidence frequency analysis and wave number amplitude analysis, the cotton/bamboo/PLA composite laminate showed the best acoustic performance (coincidence frequency of 2448 Hz) that is related to the fineness of cotton fibres, bending stiffness, natural frequency and density of the composite panel. The results suggest that the bamboo/cotton hybrid composites can be a viable candidate for engineering applications that require good bending properties, high sound absorption and vibration damping properties.