Influence of fly-ash filler and moisture content on vibrational and acoustic properties of basalt fibre reinforced composites

Fly ash, a by-product of coal combustion consisting of particulates and flue gases expelled from coal-fired furnaces, has found application as a substitute for organic fillers in the composites industry. In this study, the focus lies on assessing the vibrational and acoustic performance of composites composed of epoxy-based basalt combined with fly ash. Experimental investigations were carried out on specimens containing different weight percentages of fly ash (0%, 10%, 15% and 20% of the epoxy weight) to evaluate free vibration and acoustic impedance. Additionally, the impact of moisture on the vibrational and acoustic properties of Basalt/Fly ash-Epoxy composites was examined by subjecting the specimens to 3 months of ageing in distiled water. The results revealed that increasing the filler content up to 15% led to an increase in natural frequencies (8.5 Hz) and stiffness (3.8 N/mm) of the material, although the damping ratio (0.219) has decreased. Notably, as the specimens aged, the damping ratio is improved by 9%, while the natural frequency and stiffness decline by 9.67% and 12.5%, respectively. The material density emerged as a critical factor influencing the sound absorption capability of the specimens. The inclusion of fly ash in the epoxy matrix has enhanced the acoustic properties of the tested specimens.