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Fibers, Volume 8, Issue 12 (December 2020) – 6 articles

Cover Story (view full-size image): This figure shows a comparison between the trend of the sound absorption coefficient as a function of frequency between measurements carried out with the impedance tube and simulations carried out with the model based on artificial neural networks. We can see that the simulated curves fit those returned by measurements with the impedance tube. The typical bell curve characteristic of porous materials is confirmed; moreover, for each configuration of the specimen, a trend of the sound absorption coefficient is confirmed which is distributed selectively around the resonant frequency of the resonator. View this paper.

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16 pages, 2989 KiB

Open AccessArticle

Numerical Simulation for the Sound Absorption Properties of Ceramic Resonators

by Giuseppe Ciaburro and Gino Iannace

Fibers 2020, 8(12), 77; https://doi.org/10.3390/fib8120077 - 18 Dec 2020

Cited by 16 | Viewed by 2920

Abstract

This work reports the results of experimental measurements of the sound absorption coefficient of ceramic materials using the principle of acoustic resonators. Subsequently, the values obtained from the measurements were used to train a simulation model of the acoustic behavior of the analyzed material based on artificial neural networks. The possible applications of sound-absorbing materials made with ceramic can derive from aesthetic or architectural needs or from functional needs, as ceramic is a fireproof material resistant to high temperatures. The results returned by the simulation model based on the artificial neural networks algorithm are particularly significant. This result suggests the adoption of this technology to find the finest possible configuration that allows the best sound absorption performance of the material. Full article

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8 pages, 2980 KiB

Open AccessArticle

Optical Characterisations of Bi-Phosphosilicate Fiber for O Band Amplification

by Amilia Mansoor, Nasr Y. M. Omar, Katrina D. Dambul, Hairul Azhar Abdul-Rashid and Zulfadzli Yusoff

Fibers 2020, 8(12), 76; https://doi.org/10.3390/fib8120076 - 09 Dec 2020

Cited by 3 | Viewed by 2684

Abstract

We report on the optical properties of Bi-doped phosphosilicate fiber. The fiber with a core and a clad diameter of 7.75 µm and 125 µm, respectively, is fabricated in-house using the modified chemical vapor deposition (MCVD) with in-situ solution doping technique. The spectroscopic properties of the fabricated fiber are characterized in terms of absorption, emission and lifetime. The lifetime decay is measured to be 800 µs; indicating a good potential optical amplification in the range of 1300 to 1500 nm. A Bismuth-doped fiber amplifier (BDFA) operating within the O-band region was successfully demonstrated. At 1340 nm, a 14.8 dB gain is achieved with 300 mW pumping power. Full article

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23 pages, 24689 KiB

Open AccessArticle

Investigation of Flow Behavior and Porous Medium Resistance Coefficients for Metallic-Cloth Fibers

by Erdem Gorgun, Yahya Dogu and Mahmut Faruk Aksit

Fibers 2020, 8(12), 75; https://doi.org/10.3390/fib8120075 - 07 Dec 2020

Viewed by 2453

Abstract

The flow through porous metallic-cloth fibers influences the cloth seal leakage performance. Measuring the actual seal leakage proves difficult with challenging turbine operating conditions. A non-Darcian porous medium Computational Fluid Dynamics (CFD) model was employed for the flow within porous metallic-cloth fibers. CFD analyses need leakage data depending on the pressure load to calibrate flow resistance coefficients. A test rig was built to measure leakage with respect to the pressure load and weave orientation in four directions. The Sutherland-ideal gas approach was utilized to determine the flow resistance coefficients for Dutch twill metallic-cloth fibers as a function of pressure load. The results show that metallic-cloth fiber leakage is a linear function of pressure load. The best–worst order for leakage performance was the warp, diagonal, shute, and cross directions. For the best sealing performance, the flow direction in metallic-cloth fibers would be the warp direction. The flow resistance coefficients depend on the evaluation of the pressure level, which changes over the weave flow thickness. This is represented with the pressure constant (C_down). The best match between the test and CFD leakages was obtained for the weave directions of warp (0.9), shute (0.9), diagonal (0.7), and cross (0.0). Calibrating the resistance coefficients with respect to the pressure and temperature enables performing CFD analyses in turbine conditions. Full article

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14 pages, 1642 KiB

Open AccessEditor’s ChoiceArticle

Experimental Tests and Reliability Analysis of the Cracking Impact Resistance of UHPFRC

by Hussain A. Jabir, Sallal R. Abid, Gunasekaran Murali, Sajjad H. Ali, Sergey Klyuev, Roman Fediuk, Nikolai Vatin, Vladimir Promakhov and Yuriy Vasilev

Fibers 2020, 8(12), 74; https://doi.org/10.3390/fib8120074 - 04 Dec 2020

Cited by 68 | Viewed by 3754

Abstract

Ultra-high performance (UHP) concrete is a special type of fibrous cementitious composite that is characterized by high strength and superior ductility, toughness, and durability. This research aimed to investigate the resistance of ultra-high performance fiber-reinforced concrete (UHPFRC) against repeated impacts. An adjusted repeated drop mass impact test was adopted to evaluate the impact performance of 72 UHPFRC disc specimens. The specimens were divided into six mixtures each of 12 discs. The only difference between the mixtures was the types of fibers used, while all other mixture components were the same. Three types of fibers were used: 6 mm micro-steel, 15 mm micro-steel, and polypropylene. All mixtures included 2.5% volumetric content of fibers, however with different combinations of the three fiber types. The test results showed that the mixtures with the 15 mm micro-steel fiber absorbed a higher number of impact blows until cracking compared to other mixtures. The mixture with pure 2.5% of 15 mm micro-steel fiber exhibited the highest impact resistance, with percentage increases over the other mixtures ranging from 25 to 140%. In addition, the Weibull distribution was used to investigate the cracking impact resistance of UHP at different levels of reliability. Full article

(This article belongs to the Special Issue Effectiveness and Efficiency of Fiber Reinforcement in Ultra-High Performance Concrete)

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19 pages, 9024 KiB

Open AccessArticle

Acetylation Treatment for the Batch Processing of Natural Fibers: Effects on Constituents, Tensile Properties and Surface Morphology of Selected Plant Stem Fibers

by Isiaka Oluwole Oladele, Omokafe Seun Michael, Adeolu Adesoji Adediran, Oluwayomi Peter Balogun and Folorunso Ojo Ajagbe

Fibers 2020, 8(12), 73; https://doi.org/10.3390/fib8120073 - 01 Dec 2020

Cited by 21 | Viewed by 4471

Abstract

This work was on the comparative evaluation of the property effects obtainable when acetylation is applied to parts of selected agro fibers that are obtainable within common localities. The fibers were subjected to different concentrations of acetylation treatment at ambient temperature for 3 h. The physico-chemical, morphological, and tensile properties of the fibers were examined after the treatment. It was discovered from the results that the procedures variedly influenced the constituents of the fibers, their resulting tensile properties as well as their post-acetylation treatment surface morphology. The proportion of crystalline cellulose in the starting fibers greatly influenced their post treatment composition, behaviour and properties. The results show that plantain fibers had the highest aspect ratios, followed by banana fibers with values of about 1000 and 417, respectively. These fibers exhibited the least density and are thus potential plant fibers for composite development. Banana fiber had the least density of about 1.38 g/cm³ while that of DombeyaBuettneri fiber possessed the highest value of 1.5 g/cm³. There was significant enhancement in the hemicellulose content of Combretum Racemosum, while the lignin content of the plantain fibers was highly reduced. The treatment favoured the enhancement of the tensile properties in Combretum Racemosum fibers, which had enhanced tensile strength and strain at all compositions of the treatment. Optimum tensile strength and strain values of 155 MPa and 0.046, respectively, are achieved at 4% composition. Dombeya Buettneri fibers showed the highest ultimate tensile strength among the plant fibers in the untreated condition, which was gradually decreased as the concentration of the reagents was increased. Overall, 4% acetylation treatment is optimum for tensile properties’ enhancement for most of the natural fibers evaluated. Full article

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14 pages, 1925 KiB

Open AccessArticle

An Experimental Investigation on Optimizing Liquid Repellency of Fluorochemical Urethane Finish and Its Effect on the Physical Properties of Polyester/Cotton Blended Fabric

by Sunidhi Mehta

Fibers 2020, 8(12), 72; https://doi.org/10.3390/fib8120072 - 01 Dec 2020

Cited by 4 | Viewed by 2933

Abstract

This paper aims to optimize the liquid repellency performance of fluorochemical urethane (FU)—a patented technology with a shorter fluorocarbon chain (C₄). FU is free from persistent bioaccumulative toxins such as perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS), unlike the long-chain fluorinated chemicals (>C₆). Different sets of varied finish concentrations with an extender and a wetting agent were prepared to treat the 65/35% polyester/cotton blended fabric. The finish concentration was optimized based on the liquid repellency (water and oil-repellency) of the treated fabric and its laundering durability. In addition, the effect of the finish concentration on selected physical properties of the treated fabric was studied as well. The liquid repellency, laundering durability, and selected physical properties of the treated and untreated fabrics were analyzed using ASTM and AATCC standard test methods. The results of textile substrates treated with 60 g/L of FU show an optimum balance of desired liquid repellency without affecting the physical properties of the fabric significantly. Full article

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