Sound-Absorption Performance and Fractal Dimension Feature of Kapok Fibre/Polycaprolactone Composites

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.

Special Issue “Natural Fiber Based Composites”

“…The same sound-absorption ability can be obtained from hot pressed composites made from polycaprolactone (PCL) and kapok fibers as thermoplastic matrix and mechanical reinforcement, respectively, their sound-absorption performance depending on their volume density, the mass fraction of kapok fibers inside the materials, and their thickness [6].…”

Enhancing Image Quality Through a Novel Multiscale Fractal Dimension Formulated by the Characteristic Function

“…Studies focusing on numerical image processing and statistical examination of X-ray images have been carried out to tackle difficulties in interpreting X-ray imagery [13]. Additionally, differential box-counting methods have been proposed to compute the fractal dimension for image enhancement [14,15], with practical applications seen in the study of polymer images [16]. Moreover, a specific type of fractal, referred to as a quantum fractal or Jackson fractal, has been recently utilised in the examination of medical images [17][18][19].…”

Bio-based materials from sunflower co-products, a way to generate economical value with low environmental footprint

“…Many natural fibers can be used to manufacture such composite materials, e.g., miscanthus (Velásquez et al, 2003), kenaf core (Okuda and Sato, 2006), wheat straw (Halvarsoon et al, 2009), banana bunch (Quintana et al, 2009), oil palm trunk (Hashim et al, 2011), sugarcane bagasse (Nonaka et al, 2013), coriander straw (Uitterhaegen et al, 2017), linseed flax (Khan et al, 2021), kapok (Lyu et al, 2021), hemp (Laqraa et al, 2021), etc. Given their use properties, these materials could find applications in many fields, such as agriculture, ecological engineering, construction, load-bearing composites, packaging, paper industry, etc.…”