Abstract
This article introduces a kind of composite material made of kapok fibre and polycaprolactone by the hot-pressing method. The effects of volume density, mass fraction of kapok fibre, and thickness on the sound-absorption performance of composites were researched using a single-factor experiment. The sound-absorption performance of the composites was investigated by the transfer function method. Under the optimal process parameters, when the density of the composite material was 0.172 g/cm3, the mass fraction of kapok was 40%, and the thickness was 2 cm, the composite material reached the maximum sound-absorption coefficient of 0.830, and when the sound-absorption frequency was 6300 Hz, the average sound-absorption coefficient was 0.520, and the sound-absorption band was wide. This research used the box dimension method to calculate composites’ fractal dimensions by using the Matlab program based on the fractal theory. It analysed the relationships between fractal dimension and volume density, fractal dimension and mass fraction of kapok fibre, and fractal dimension and thickness. The quantitative relations between fractal dimension and maximum sound-absorption coefficient, fractal dimension, and resonant sound-absorption frequency were derived, which provided a theoretical basis for studying sound-absorption performance. The results showed that kapok fibre/polycaprolactone composites had strong fractal characteristics, which had important guiding significance for the sound-absorption performance of kapok fibre composites.
Highlights
Noise pollution belongs to one kind of environmental pollution, which is regarded as one of four major environmental problems in the world together with water pollution, air pollution, and light pollution
Azieyanti et al [18] prepared reinforced polypropylene composites using jute and kapok fibres as raw materials and compared jute and kapok fibre-reinforced polypropylene sound insulation effect composites; the results showed that the performance of the composite material, along with the increase in the quality percentage of jute and kapok fibre, increased the filling amount to
The results showed that the multilayer composite had better sound-absorption performance than the single-layer non-woven fabric at low frequency
Summary
Noise pollution belongs to one kind of environmental pollution, which is regarded as one of four major environmental problems in the world together with water pollution, air pollution, and light pollution. Smardzewski et al [5] determined the normal surface impedance and sound-absorption coefficient of several woods from Europe and tropical regions, and the results showed that oak, ash, sapele, and pine had the highest soundabsorption coefficient at the frequency of 2 kHz. Asdrubali et al [6] studied the acoustic properties of sustainable materials and found that sustainable products made from natural and recycled materials are effective substitutes for traditional synthetic materials. The results showed that the industrially prepared fibres had poorer sound-absorption performance at low frequencies than fresh coconut shell fibres due to the addition of the binder. Fibres must be mixed with additives to enhance properties such as hardness, antifungal, and flammability Methods such as increasing air gaps or perforating plates should be used to improve the acoustic properties of industrially treated coconut shell fibres
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