Sound absorption properties of natural materials and sandwich structure composite

Awang, Nor Hasmah Ashikin (2021) Sound absorption properties of natural materials and sandwich structure composite. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

Natural composite material and wood are environmentally friendly materials and have been seen to be excellent sound absorption materials due to their properties which are low density and porous structure. In this study, the sound absorption coefficient of the sandwich structure contains wood fibers reinforce polyethylene composite (WPC), kenaf mat, Polyurethane foam (PU foam), and Pineapple leaf fiber (PALF) were evaluated by using a two-microphone transfer function technique with an impedance tube system at the frequency ranging from 500Hz to 5000Hz. 24 configuration of a sandwich structure with hollow and solid WPC skins is produced with a different type of core and the results are plotted using the MATLAB software. The results show that similar behaviour of solid and hollow WPC as the skin can be seen as at the lower frequency it can absorb almost half of the sound energy with a value above 0.5 and at the higher frequency, it gives a maximum coefficient value which is 1.0. WPC shows to have good properties of sound absorption because it contains many connected air cavities. As the sandwich structure is made with porous material for the core and skin, we could see the ability of the sound absorption of the sandwich structure is improved. The sound absorption coefficient of the sandwich structures with kenaf core and PALF core are overall higher compared to the sandwich structures with PU foam due to the porous structure of the materials that can reduce and trapped the sound energy. The introduction of air gap distance behind the sandwich structure can thus be a good alternative technique to improve the sound absorption coefficient at lower frequencies because the value improves significantly with the addition of 10mm and 20mm air gap distance. It was concluded that introducing a natural-materials-based sandwich structure is one of the effective ways to improve the acoustic absorption performance of composite laminate.

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