Investigation of acoustical and mechanical properties of epoxy based natural fibre composites

Noise is unwanted sound, which is harmful to our auditory system. Sound absorbing materials are used in reducing, eliminating or insulating the noise. Existing sound absorbing materials are mostly made from asbestos and synthetic materials, which are known to be harmful for the environment and health. Thus, this has motivated the initiative to develop alternative materials. In this research, natural waste product such as banana, luffa and oil palm fibre were blended with epoxy to form natural fibre composites. Mechel, and Delany and Bazley empirical models were used as a preliminary theoretical analysis in order to gain an understanding of the effect of thickness, fibre size, flow resistivity and types of fibre on sound absorption. The modelling showed that banana, luffa, and oil palm have almost similar sound absorption behaviour. Based on the empirical models, it showed that with increasing fibre diameter, the flow resistivity decreased, but the sound absorption still increased as long as the porosity is high. Furthermore, with increasing material thickness, an increase in the sound absorption is expected. Lastly, the modelling results showed that the sound absorption, increased with increasing frequency. In the case of acoustical and mechanical characterisation, it was revealed that the fibre loading and alkaline treatment have a significant effect. It was found that the sound absorption coefficient for the composites tested increased with increasing fibre loading. The result also showed that the treated fibre gives better sound absorption compared to the untreated counterpart. The treatment caused removal of certain wax, oil, and certain structure (i.e. such as hemicellulose, cellulose, and lignin), which improved the tensile and yield strength of the natural fibre composite materials. Chemical treatment caused break, stretch or bend in the H, OH and CH bond structure of the fibres which were validated by using Fourier transform infrared spectral analysis. Furthermore, the changes on the surface roughness and the structure of the fibre can be seen using scanning electron microscope and light/optical microscope. It showed that the treated fibre have a rougher surface and larger lumen structure than the untreated fibre. Based on the result of acoustical and mechanical test, it was concluded that the novel composites developed would find new applications for agricultural waste and reduced oil-derived polymers.