Sound absorption coefficient assessment of sisal, coconut husk and sugar cane fibers for low frequencies based on three different methods

Silva, Claudia Cilene Bittencourt da; Terashima, Fernando Jun Hattori; Barbieri, Nilson; Lima, Key Fonseca de

doi:10.1016/j.apacoust.2019.07.001

Cited by 75 publications

(25 citation statements)

References 31 publications

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“…These properties make natural fibers able to compete with glass fibers in composite materials [34][35][36]. However, there are some disadvantages that restrict the use of natural fibers in industry, such as incompatibility with specific polymeric matrices, formation of aggregates while processing, and their poor resistance to moisture [37][38][39]. To control these drawbacks, natural fibers are often treated with suitable chemicals/methods, e.g., silane, graft copolymerization, isocyanate, mercerization, acetylation, benzyl compounds and acrylamide [40].…”

Section: Introductionmentioning

confidence: 99%

Fabrication and Characterization of Microcellular Polyurethane Sisal Biocomposites

Abdel-Hamid¹,

Al-Qabandi²,

N.A.S.

et al. 2019

Molecules

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In this study, microcellular polyurethane (PU)-natural fiber (NF) biocomposites were fabricated. Polyurethanes based on castor oil and PMDI were synthesized with varying volume ratios of sisal fiber. The effect of natural fiber treatment using water and alkaline solution (1.5% NaOH) and load effect were investigated. Biocomposites were mechanically and physically investigated using tensile, viscoelasticity, and water absorption tests. The interfacial adhesion between PU and sisal fiber was studied using SEM. Short NF loads (3%) showed a significant improvement in the mechanical properties of the PU-sisal composite such as modulus of elasticity, yield and tensile strength up to 133%, 14.35 % and 36.7% respectively. Viscoelastic measurements showed that the composites exhibit an elastic trend as the real compliance (J’) values were higher than those of the imaginary compliance (J’’). Increasing NF loads resulted in a decrease of J’. Applying variable temperatures (120–80 °C) caused an increase in the stiffness at different frequencies.

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Section: Introductionmentioning

confidence: 99%

Fabrication and Characterization of Microcellular Polyurethane Sisal Biocomposites

Abdel-Hamid¹,

Al-Qabandi²,

N.A.S.

et al. 2019

Molecules

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“…In the sound absorption and acoustic impedance tests, the incident plane wave that is reflected (i.e., reflected wave) is measured by the probe that is placed facing the sample. The normal sound absorption coefficient (α-Equation ( 1)) was calculated by monitoring the frequency-dependent reflection coefficient (R(ω)-Equation ( 2)) on a fixed position (x) [18]. This reflection coefficient is determined by the measurement of the acoustic impedance (Z(ω)) during the test, according to Equation ( 3), where P is the captures sound pressure level and u the particle velocity [19]:…”

Section: Acoustic Testing Of the Samplesmentioning

confidence: 99%

“…The values of incident acoustic impedance (Zi) were measured recurring to the same method used for the sound absorption coefficient (Equation ( 3)). As for the transmitted acoustic impedance (Zt) was determined in a similar approach, but by changing the probe to the other side of the sample (Figure 6) to measure the transmitted wave: The normal sound absorption coefficient (α-Equation ( 1)) was calculated by monitoring the frequency-dependent reflection coefficient (R(ω)-Equation ( 2)) on a fixed position (x) [18]. This reflection coefficient is determined by the measurement of the acoustic impedance (Z(ω)) during the test, according to Equation ( 3), where P is the captures sound pressure level and u the particle velocity [19]:…”

Section: Acoustic Testing Of the Samplesmentioning

confidence: 99%

Vibration Damping and Acoustic Behavior of PU-Filled Non-Stochastic Aluminum Cellular Solids

Carneiro

Puga

Meireles

2021

Metals

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Aluminum-based cellular solids are promising lightweight structural materials considering their high specific strength and vibration damping, being potential candidates for future railway vehicles with enhanced riding comfort and low fuel consumption. The filling of these lattices with polymer-based (i.e., polyurethane) foams may further improve the overall vibration/noise-damping without significantly increasing their density. This study explores the dynamic (i.e., frequency response) and acoustic properties of unfilled and polyurethane-filled aluminum cellular solids to characterize their behavior and explore their benefits in terms of vibration and noise-damping. It is shown that polyurethane filling can increase the vibration damping and transmission loss, especially if the infiltration process uses flexible foams. Considering sound reflection, however, it is shown that polyurethane filled samples (0.27–0.30 at 300 Hz) tend to display lower values of sound absorption coefficient relatively to unfilled samples (0.75 at 600 Hz), is this attributed to a reduction in overall porosity, tortuosity and flow resistivity. Foam-filled samples (43–44 dB at 700–1200 Hz) were shown to be more suitable to reduce sound transmission rather than reflection than unfilled samples (21 dB at 700 Hz). It was shown that the morphology of these cellular solids might be optimized depending on the desired application: (i) unfilled aluminum cellular solids are appropriate to mitigate internal noises due to their high sound absorption coefficient; and (ii) PU filled cellular solids are appropriate to prevent exterior noises and vibration damping due to their high transmission loss in a wide range of frequencies and vibration damping.

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“…In addition, Attenborough [35] has pointed out that empirical relationships of the form of Equations (1) and (2) should be valid for fibrous porous materials as well as non-fibrous ones. Therefore, the Delany and Bazley model has been successfully applied to different sound-absorbing materials [36][37][38], including those made of natural fibers [39,40]. One such study was recently presented by Berardi and Iannace [32].…”

Section: Empirical Model For Fibrous Sound-absorbing Materialsmentioning

confidence: 99%

Sound-Absorption Properties of Materials Made of Esparto Grass Fibers

Arenas¹,

Tormos

Fernández

et al. 2020

Sustainability

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Research on sound-absorbing materials made of natural fibers is an emerging area in sustainable materials. In this communication, the use of raw esparto grass as an environmentally friendly sound-absorbing material is explored. Measurements of the normal-incidence sound-absorption coefficient and airflow resistivity of three different types of esparto from different countries are presented. In addition, the best-fit coefficients for reasonable prediction of the sound-absorption performance by means of simple empirical formulae are reported. These formulae require only knowledge of the airflow resistivity of the fibrous material. The results presented in this paper are an addition to the characterization of available natural fibers to be used as alternatives to synthetic ones in the manufacturing of sound-absorbing materials.

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Sound absorption coefficient assessment of sisal, coconut husk and sugar cane fibers for low frequencies based on three different methods

Cited by 75 publications

References 31 publications

Fabrication and Characterization of Microcellular Polyurethane Sisal Biocomposites

Fabrication and Characterization of Microcellular Polyurethane Sisal Biocomposites

Vibration Damping and Acoustic Behavior of PU-Filled Non-Stochastic Aluminum Cellular Solids

Sound-Absorption Properties of Materials Made of Esparto Grass Fibers

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