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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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18 pages, 21481 KiB  
Article
Flexural Strengthening of RC Continuous T-Beams Using CFRP
by Ayssar Al-Khafaji and Hani Salim
Fibers 2020, 8(6), 41; https://doi.org/10.3390/fib8060041 - 20 Jun 2020
Cited by 26 | Viewed by 5624
Abstract
In this paper, experimental investigations for strengthening reinforced concrete (RC) continuous beams were performed. Eighteen T-beams were cast, twelve of which were inverted T-beams where the flange portion of the T-beam was subjected to positive flexure to represent the support region of a [...] Read more.
In this paper, experimental investigations for strengthening reinforced concrete (RC) continuous beams were performed. Eighteen T-beams were cast, twelve of which were inverted T-beams where the flange portion of the T-beam was subjected to positive flexure to represent the support region of a continuous beam. Six of the T-beams were non-inverted where the web is subjected to positive flexure. Carbon fiber reinforced polymer (CFRP) sheets with different widths were considered, and different strengthening configurations with the same area of CFRP were investigated. The use of one-layer, multiple layers, or multiple strips of CFRP were evaluated to investigate the effect of these configurations on the ultimate capacity and ductility of the strengthened beams. From the experimental observation of the non-inverted beams, it was found that the ultimate load capacities of the CFRP-strengthened beams were enhanced by 4% to 90% compared to the control beam. Using multiple layers of CFRP sheets enhanced the stiffness of the beams by 4% to 46%, depending on the CFRP area and configurations. The debonding of CFRP before the ultimate failure provided additional ductility to the tested beams. For the strengthening of the inverted beams, it was found that the addition of CFRP strips did not increase the strength of the beams when the width of CFRP to beam width ratio was less than 0.25, but the ductility of the beam was enhanced slightly. The use of multiple strips was found to be a more effective way for the strengthening of the negative moment region than using multiple layers. This can also provide more desirable modes of failure than when applying CFRP in multiple layers. Ductility was found to be lower if multiple layers were used compared to other configurations. Moreover, it was observed that as the compressive strength of concrete increased the addition of the CFRP improved the beams ductility. Full article
(This article belongs to the Special Issue Experimental and Numerical Advancements on Strengthening of Concrete Structures with Fiber Reinforced Polymers)
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20 pages, 10381 KiB  
Article
Cyclic Performance of RC Columns with Inadequate Lap Splices Strengthened with CFRP Jackets
by George Kalogeropoulos and Alexander-Dimitrios Tsonos
Fibers 2020, 8(6), 39; https://doi.org/10.3390/fib8060039 - 13 Jun 2020
Cited by 17 | Viewed by 5670
Abstract
The cyclic performance of non-seismically designed reinforced concrete (RC) columns, strengthened with carbon fiber reinforced polymer (CFRP) jackets, was analytically and experimentally investigated herein. Three cantilever column specimens were constructed, incorporating design parameters of the period 1950s–1970s, namely with concrete of a low [...] Read more.
The cyclic performance of non-seismically designed reinforced concrete (RC) columns, strengthened with carbon fiber reinforced polymer (CFRP) jackets, was analytically and experimentally investigated herein. Three cantilever column specimens were constructed, incorporating design parameters of the period 1950s–1970s, namely with concrete of a low compressive strength, plain steel bars, widely-spaced ties and inadequate lap splices of reinforcement. The specimens were strengthened using CFRP jackets and were subsequently subjected to cyclic inelastic lateral displacements. The main parameters examined were the length of the lap splices, the acceptable relative bar slipping value and the width of the jackets. The hysteresis behaviors of the enhanced columns were compared, while also being evaluated with respect to those of two original columns and to the seismic performance of a control specimen with continuous reinforcement, tested in a previous work. An analytical formulation was proposed for accurately predicting the seismic responses of the column specimens, comparing the actual shear stress value with the ultimate shear capacity of the concrete in the lap splice region. The test results verified the predictions of the analytical model, regarding the seismic performance of the strengthened columns. Moreover, the influences of the examined parameters in securing the ductile hysteresis performance were evaluated. Full article
(This article belongs to the Special Issue Experimental and Numerical Advancements on Strengthening of Concrete Structures with Fiber Reinforced Polymers)
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18 pages, 7213 KiB  
Article
Influence of Milled Glass Fiber Fillers on Mode I & Mode II Interlaminar Fracture Toughness of Epoxy Resin for Fabrication of Glass/Epoxy Composites
by Kannivel Saravanakumar, Vellayaraj Arumugam, Rotte Souhith and Carlo Santulli
Fibers 2020, 8(6), 36; https://doi.org/10.3390/fib8060036 - 11 Jun 2020
Cited by 39 | Viewed by 6555
Abstract
The present work is focused on improving mode I and mode II delamination resistance of glass/epoxy composite laminates (50 wt.% of glass fibers) with milled glass fibers, added in various amounts (2.5, 5, 7.5 and 10% of the epoxy weight). Including fillers in [...] Read more.
The present work is focused on improving mode I and mode II delamination resistance of glass/epoxy composite laminates (50 wt.% of glass fibers) with milled glass fibers, added in various amounts (2.5, 5, 7.5 and 10% of the epoxy weight). Including fillers in the interlayer enhances the delamination resistance by providing a bridging effect, therefore demanding additional energy to initiate the crack in the interlaminar domain, which results in turn in enhanced fracture toughness. The maximal increase of mode I and mode II fracture toughness and of flexural strength was obtained by the addition of 5% milled glass fiber. The mechanism observed suggests that crack propagation is stabilized even leading to its arrest/deflection, as a considerable amount of milled glass fiber filler was oriented transverse to the crack path. In contrast, at higher filler loading, tendency towards stress concentration grows due to local agglomeration and improper dispersion of excess fillers in inter/intralaminar resin channel, causing poor adhesion to the matrix, which leads to reduction in fracture toughness, strength and strain to failure. Fractured surfaces analyzed using scanning electron microscopy (SEM) revealed a number of mechanisms, such as crack deflection, individual debonding and filler/matrix interlocking, all contributing in various ways to improve fracture toughness. Full article
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15 pages, 1616 KiB  
Article
Original Solution of Coupled Nonlinear Schrödinger Equations for Simulation of Ultrashort Optical Pulse Propagation in a Birefringent Fiber
by Airat Zhavdatovich Sakhabutdinov, Vladimir Ivanovich Anfinogentov, Oleg Gennadievich Morozov, Vladimir Alexandrovich Burdin, Anton Vladimirovich Bourdine, Ildaris Mudarrisovich Gabdulkhakov and Artem Anatolievich Kuznetsov
Fibers 2020, 8(6), 34; https://doi.org/10.3390/fib8060034 - 3 Jun 2020
Cited by 6 | Viewed by 5173
Abstract
This paper discusses approaches to the numerical integration of the coupled nonlinear Schrödinger equations system, different from the generally accepted approach based on the method of splitting according to physical processes. A combined explicit/implicit finite-difference integration scheme based on the implicit Crank–Nicolson finite-difference [...] Read more.
This paper discusses approaches to the numerical integration of the coupled nonlinear Schrödinger equations system, different from the generally accepted approach based on the method of splitting according to physical processes. A combined explicit/implicit finite-difference integration scheme based on the implicit Crank–Nicolson finite-difference scheme is proposed and substantiated. It allows the integration of a nonlinear system of equations with a choice of nonlinear terms from the previous integration step. The main advantages of the proposed method are: its absolute stability through the use of an implicit finite-difference integration scheme and an integrated mechanism for refining the numerical solution at each step; integration with automatic step selection; performance gains (or resolutions) up to three or more orders of magnitude due to the fact that there is no need to produce direct and inverse Fourier transforms at each integration step, as is required in the method of splitting according to physical processes. An additional advantage of the proposed method is the ability to calculate the interaction with an arbitrary number of propagation modes in the fiber. Full article
(This article belongs to the Special Issue Optical Fibers as a Key Element of Distributed Sensor Systems)
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22 pages, 5124 KiB  
Article
Measurement of Flexural Rigidity of Multi-Walled Carbon Nanotubes by Dynamic Scanning Electron Microscopy
by Renata Fortini, Asmus Meyer-Plath, Dominic Kehren, Ulrich Gernert, Leonardo Agudo Jácome and Heinz Sturm
Fibers 2020, 8(5), 31; https://doi.org/10.3390/fib8050031 - 12 May 2020
Cited by 7 | Viewed by 5163
Abstract
In this work the flexural rigidity of individual large diameter multi-walled carbon nanotubes (MWCNTs) was investigated. The bending modulus were obtained by detecting the resonance frequencies of mechanically excited cantilevered carbon nanotubes using the so-called dynamic scanning electron microscopy technique, and applying the [...] Read more.
In this work the flexural rigidity of individual large diameter multi-walled carbon nanotubes (MWCNTs) was investigated. The bending modulus were obtained by detecting the resonance frequencies of mechanically excited cantilevered carbon nanotubes using the so-called dynamic scanning electron microscopy technique, and applying the Euler–Bernoulli beam theory. For the nanotubes studied, we determined a modulus of up to 160 GPa. This agrees with values reported by other authors for MWCNTs produced by catalytic chemical vapor deposition, however, it is 6-8 times smaller than values reported for single and multi-walled carbon nanotubes produced by arc-discharge synthesis. Toxicological studies with carbon nanotubes have been showing that inhaled airborne nanofibers that reach the deep airways of the respiratory system may lead to serious, asbestos-like lung diseases. These studies suggested that their toxicity critically depends on the fiber flexural rigidity, with high rigidity causing cell lesions. To complement the correlation between observed toxicological effects and fiber rigidities, reliable and routinely applicable measurement techniques for the flexural rigidity of nanofibers are required. Full article
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17 pages, 1981 KiB  
Review
Laser Sources Based on Rare-Earth Ion Doped Tellurite Glass Fibers and Microspheres
by Elena A. Anashkina
Fibers 2020, 8(5), 30; https://doi.org/10.3390/fib8050030 - 11 May 2020
Cited by 49 | Viewed by 7504
Abstract
In recent years, huge progress has been made in the development of rare-earth ion doped tellurite glass laser sources, ranging from watt- and multiwatt-level fiber lasers to nanowatt level microsphere lasers. Significant success has been achieved in extending the spectral range of tellurite [...] Read more.
In recent years, huge progress has been made in the development of rare-earth ion doped tellurite glass laser sources, ranging from watt- and multiwatt-level fiber lasers to nanowatt level microsphere lasers. Significant success has been achieved in extending the spectral range of tellurite fiber lasers generating at wavelengths beyond 2 μm as well as in theoretical understanding. This review is aimed at discussing the state of the art of neodymium-, erbium-, thulium-, and holmium-doped tellurite glass fiber and microsphere lasers. Full article
(This article belongs to the Special Issue Fiber Laser Sources)
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14 pages, 4927 KiB  
Article
A Novel Method for Electrospinning Nanofibrous 3-D Structures
by Daniela Lubasova and Anil N. Netravali
Fibers 2020, 8(5), 27; https://doi.org/10.3390/fib8050027 - 30 Apr 2020
Cited by 13 | Viewed by 6207
Abstract
The fast and precise fabrication of three-dimensional (3-D) structures made of nanofibers is an important development trend in the electrospinning technique. This paper describes a new and facile method of electrospinning to fabricate nanofibrous 3-D structures. The nanofibrous 3-D structures can be engineered [...] Read more.
The fast and precise fabrication of three-dimensional (3-D) structures made of nanofibers is an important development trend in the electrospinning technique. This paper describes a new and facile method of electrospinning to fabricate nanofibrous 3-D structures. The nanofibrous 3-D structures can be engineered to have the desired layer thicknesses, where the fiber spacing, density (i.e., fiber volume/unit volume), as well as shape of the structure may be controlled. While innumerable structural variations are possible with this method, this paper discusses, as proof-of-concept, a few cases that illustrate how 3-D nanofiber webs can be made for filtration application. Computerized automation of the method will make it possible to build almost any 3-D web structure suitable for a myriad of applications including ultra-light-weight insulation and scaffolds for hydrogel preparation and tissue. Full article
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13 pages, 6185 KiB  
Article
New Silica Laser-Optimized Multimode Optical Fibers with Extremely Enlarged 100-μm Core Diameter for Gigabit Onboard and Industrial Networks
by Vladimir A. Burdin, Michael V. Dashkov, Vladimir V. Demidov, Konstantin V. Dukelskii, Alexander S. Evtushenko, Artem A. Kuznetsov, Alexandra S. Matrosova, Oleg G. Morozov, Egishe V. Ter-Nersesyants, Alexander A. Vasilets, Elena S. Zaitseva, Alexander E. Zhukov and Anton V. Bourdine
Fibers 2020, 8(3), 18; https://doi.org/10.3390/fib8030018 - 17 Mar 2020
Cited by 15 | Viewed by 5266
Abstract
We present new type of silica graded index laser-optimized multimode optical fibers (LOMF) with extremely enlarged core diameter up to 100 μm and “typical” “telecommunication” cladding diameter 125 μm. This optical fiber was designed for harsh environment Gigabit onboard cable systems and industrial [...] Read more.
We present new type of silica graded index laser-optimized multimode optical fibers (LOMF) with extremely enlarged core diameter up to 100 μm and “typical” “telecommunication” cladding diameter 125 μm. This optical fiber was designed for harsh environment Gigabit onboard cable systems and industrial networks. It differs by special optimized graded refractive index profile, providing low differential mode delay (DMD) for selected guided modes. We present some results of tests, performed for manufactured pilot 520 m length of described LOMF 100/125, concerned with its geometry properties as well as key transmission parameters—attenuation and DMD map. Full article
(This article belongs to the Special Issue Optical Fibers as a Key Element of Distributed Sensor Systems)
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14 pages, 7638 KiB  
Article
Development and Multiscale Characterization of 3D Warp Interlock Flax Fabrics with Different Woven Architectures for Composite Applications
by Henri Lansiaux, Damien Soulat, François Boussu and Ahmad Rashed Labanieh
Fibers 2020, 8(2), 15; https://doi.org/10.3390/fib8020015 - 18 Feb 2020
Cited by 10 | Viewed by 5916
Abstract
Multiscale characterization of the textile preform made of natural fibers is an indispensable way to understand and assess the mechanical properties and behavior of composite. In this study, a multiscale experimental characterization is performed on three-dimensional (3D) warp interlock woven fabrics made of [...] Read more.
Multiscale characterization of the textile preform made of natural fibers is an indispensable way to understand and assess the mechanical properties and behavior of composite. In this study, a multiscale experimental characterization is performed on three-dimensional (3D) warp interlock woven fabrics made of flax fiber on the fiber (micro), roving (meso), and fabric (macro) scales. The mechanical tensile properties of the flax fiber were determined by using the impregnated fiber bundle test. The effect of the twist was considered in the back-calculation of the fiber stiffness to reveal the calculation limits of the rule of mixture. Tensile tests on dry rovings were carried out while considering different twist levels to determine the optimal amount of twist required to weave the flax roving into a 3D warp interlock. Finally, at fabric-scale, six different 3D warp interlock architectures were woven to understand the role of the architecture of binding rovings on the mechanical properties of the dry 3D fabric. The results reveal the importance of considering the properties of the fiber and roving at these scales to determine the more adequate raw material for weaving. Further, the characterization of the 3D woven structures shows the preponderant role of the binding roving on their structural and mechanical properties. Full article
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21 pages, 3359 KiB  
Article
U-Jacketing Applications of Fiber-Reinforced Polymers in Reinforced Concrete T-Beams against Shear—Tests and Design
by Constantin E. Chalioris, Adamantis G. Zapris and Chris G. Karayannis
Fibers 2020, 8(2), 13; https://doi.org/10.3390/fib8020013 - 17 Feb 2020
Cited by 77 | Viewed by 7720
Abstract
The application of externally bonded fiber-reinforced polymer (EB-FRP) as shear transverse reinforcement applied in vulnerable reinforced concrete (RC) beams has been proved to be a promising strengthening technique. However, past studies revealed that the effectiveness of this method depends on how well the [...] Read more.
The application of externally bonded fiber-reinforced polymer (EB-FRP) as shear transverse reinforcement applied in vulnerable reinforced concrete (RC) beams has been proved to be a promising strengthening technique. However, past studies revealed that the effectiveness of this method depends on how well the reinforcement is bonded to the concrete surface. Thus, although the application of EB-FRP wrapping around the perimeter of rectangular cross-sections leads to outstanding results, U-jacketing in shear-critical T-beams seems to undergo premature debonding failures resulting in significant reductions of the predictable strength. In this work, five shear-critical RC beams with T-shaped cross-section were constructed, strengthened and tested in four-point bending. Epoxy bonded carbon FRP (C-FRP) sheets were applied on the three sides and along the entire length of the shear-strengthened T-beams as external transverse reinforcement. Furthermore, the potential enhancement of the C-FRP sheets anchorage using bolted steel laminates has been examined. Test results indicated that although the C-FRP strengthened beams exhibited increased shear capacity, the brittle failure mode was not prevented due to the debonding of the FRP from the concrete surface. Nevertheless, the applied mechanical anchor of the C-FRP sheets delayed the debonding. Moreover, the design provisions of three different code standards (Greek Code of Interventions, Eurocode 8 and ACI Committee 440) concerning the shear capacity of T-shaped RC beams retrofitted with EB-FRP jackets or strips in U-jacketing configuration are investigated. The ability of these code standards to predict safe design estimations is checked against 165 test data from the current experimental project and data available in the literature. Full article
(This article belongs to the Special Issue Steel Fibre Reinforced Concrete Behaviour)
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11 pages, 1282 KiB  
Article
Terahertz Hollow Core Antiresonant Fiber with Metamaterial Cladding
by Jakeya Sultana, Md. Saiful Islam, Cristiano M. B. Cordeiro, Alex Dinovitser, Mayank Kaushik, Brian W.-H. Ng and Derek Abbott
Fibers 2020, 8(2), 14; https://doi.org/10.3390/fib8020014 - 17 Feb 2020
Cited by 23 | Viewed by 7000
Abstract
A hollow core antiresonant photonic crystal fiber (HC-ARPCF) with metal inclusions is numerically analyzed for transmission of terahertz (THz) waves. The propagation of fundamental and higher order modes are investigated and the results are compared with conventional dielectric antiresonant (AR) fiber designs. Simulation [...] Read more.
A hollow core antiresonant photonic crystal fiber (HC-ARPCF) with metal inclusions is numerically analyzed for transmission of terahertz (THz) waves. The propagation of fundamental and higher order modes are investigated and the results are compared with conventional dielectric antiresonant (AR) fiber designs. Simulation results show that broadband terahertz radiation can be guided with six times lower loss in such hollow core fibers with metallic inclusions, compared to tube lattice fiber, covering a single mode bandwidth (BW) of 700 GHz. Full article
(This article belongs to the Special Issue Microstructured Optical Fibers and Applications)
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15 pages, 9975 KiB  
Article
Experimental Investigation and Numerical Analysis of Bond Behavior in SRG-Strengthened Masonry Prisms Using UHTSS and Stainless-Steel Fibers
by Francesco Bencardino, Mattia Nisticò and Salvatore Verre
Fibers 2020, 8(2), 8; https://doi.org/10.3390/fib8020008 - 27 Jan 2020
Cited by 22 | Viewed by 4748
Abstract
This paper deals with the experimental and numerical study of the bond behavior of two steel reinforced grout (SRG)-strengthened masonry systems. Ten shear bond tests were carried out on prismatic masonry specimens. The data of experimental tests are recorded and results are given [...] Read more.
This paper deals with the experimental and numerical study of the bond behavior of two steel reinforced grout (SRG)-strengthened masonry systems. Ten shear bond tests were carried out on prismatic masonry specimens. The data of experimental tests are recorded and results are given in terms of load/stress-global slip curves, failure modes, tables, graphs and photographic reports, comparing the results of the two strengthening systems. Two kinds of steel fibers available in marketplace were used: ultra-high tensile strength steel galvanized micro-cords and stainless-steel strands. The main target is to obtain information on the behavior of the bond between masonry surface and the two types of SRG composites, which are characterized by two substantial differences: tensile strength with a ratio of 2.4 and the corresponding surface mass density with a ratio of 0.30. Finally, the influence of the matrices coupled with the two systems is critically analyzed. The characterization of the bond behavior is necessary in order to confirm the performance of the SRG systems that have become increasingly used and attractive. It also aims to make a contribution to the existing knowledge especially in relation to the use of low resistance steel fibers (stainless steel) which are still few studied today. Furthermore, using a suitable interface law proposed in the literature, a numerical model is defined and employed to simulate the behavior of the specimens tested in the laboratory. The comparisons show a good agreement between numerical and experimental results in terms of the maximum load, load versus global-slip curves, and crack patterns. Full article
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16 pages, 863 KiB  
Article
Industrial Hemp Fibers: An Overview
by João P. Manaia, Ana T. Manaia and Lúcia Rodriges
Fibers 2019, 7(12), 106; https://doi.org/10.3390/fib7120106 - 2 Dec 2019
Cited by 149 | Viewed by 31006
Abstract
Industrial hemp (Cannabis sativa) is one of the most available and widely produced bast fibers with high cellulose content. Interest in these fibers is warranted due to environmental protection challenges as well as their inherent properties such as low density, high [...] Read more.
Industrial hemp (Cannabis sativa) is one of the most available and widely produced bast fibers with high cellulose content. Interest in these fibers is warranted due to environmental protection challenges as well as their inherent properties such as low density, high specific strength, and stiffness. In addition, advanced research and progress have gone into increasing their mechanical performance through surface treatments and in the development of new materials. The most promising application for hemp fibers is as reinforcement in polymeric composites or through hybridization. Nonetheless, more research is needed to improve their properties and expand their range of applications. The biodegradability issue is one problem that must be addressed when considering long life-cycle applications as the reproducibility of these composites’ final properties. This review is a comprehensive literature review on hemp fibers. It includes hemp fibers’ chemical and mechanical properties, surface modifications, hybrid composites, as well as current and future applications. Full article
(This article belongs to the Special Issue Plant Fibers)
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29 pages, 3127 KiB  
Review
Nano-Structured Optical Fibers Made of Glass-Ceramics, and Phase Separated and Metallic Particle-Containing Glasses
by Alexander Veber, Zhuorui Lu, Manuel Vermillac, Franck Pigeonneau, Wilfried Blanc and Laeticia Petit
Fibers 2019, 7(12), 105; https://doi.org/10.3390/fib7120105 - 30 Nov 2019
Cited by 35 | Viewed by 8652
Abstract
For years, scientists have been looking for different techniques to make glasses perfect: fully amorphous and ideally homogeneous. Meanwhile, recent advances in the development of particle-containing glasses (PCG), defined in this paper as glass-ceramics, glasses doped with metallic nanoparticles, and phase-separated glasses show [...] Read more.
For years, scientists have been looking for different techniques to make glasses perfect: fully amorphous and ideally homogeneous. Meanwhile, recent advances in the development of particle-containing glasses (PCG), defined in this paper as glass-ceramics, glasses doped with metallic nanoparticles, and phase-separated glasses show that these “imperfect” glasses can result in better optical materials if particles of desired chemistry, size, and shape are present in the glass. It has been shown that PCGs can be used for the fabrication of nanostructured fibers—a novel class of media for fiber optics. These unique optical fibers are able to outperform their traditional glass counterparts in terms of available emission spectral range, quantum efficiency, non-linear properties, fabricated sensors sensitivity, and other parameters. Being rather special, nanostructured fibers require new, unconventional solutions on the materials used, fabrication, and characterization techniques, limiting the use of these novel materials. This work overviews practical aspects and progress in the fabrication and characterization methods of the particle-containing glasses with particular attention to nanostructured fibers made of these materials. A review of the recent achievements shows that current technologies allow producing high-optical quality PCG-fibers of different types, and the unique optical properties of these nanostructured fibers make them prospective for applications in lasers, optical communications, medicine, lighting, and other areas of science and industry. Full article
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23 pages, 3139 KiB  
Article
Influence of Fiber Content on Shear Capacity of Steel Fiber-Reinforced Concrete Beams
by Juan Andres Torres and Eva O.L. Lantsoght
Fibers 2019, 7(12), 102; https://doi.org/10.3390/fib7120102 - 28 Nov 2019
Cited by 43 | Viewed by 8307
Abstract
For shear-critical structural elements where the use of stirrups is not desirable, such as slabs or beams with reinforcement congestion, steel fibers can be used as shear reinforcement. The contribution of the steel fibers to the shear capacity lies in the action of [...] Read more.
For shear-critical structural elements where the use of stirrups is not desirable, such as slabs or beams with reinforcement congestion, steel fibers can be used as shear reinforcement. The contribution of the steel fibers to the shear capacity lies in the action of the steel fibers bridging the shear crack, which increases the shear capacity and prevents a brittle failure mode. This study evaluates the effect of the amount of fibers in a concrete mix on the shear capacity of steel fiber-reinforced concrete beams with mild steel tension reinforcement and without stirrups. For this purpose, 10 beams were tested. Five different fiber volume fractions were studied: 0.0%, 0.3%, 0.6%, 0.9%, and 1.2%. For each different steel fiber concrete mix, the concrete compressive strength was determined on cylinders and the tensile strength was determined in a flexural test on beam specimens. Additionally, the influence of fibers on the shear capacity was analyzed based on results reported in the literature, as well as based on the expressions derived for estimating the shear capacity of steel fiber-reinforced concrete beams. The outcome of these experiments is that a fiber percentage of 1.2% or fiber factor of 0.96 can be used to replace minimum stirrups according to ACI 318-14 and a 0.6% fiber volume fraction or fiber factor of 0.48 to replace minimum stirrups according to Eurocode 2. A fiber percentage of 1.2% or fiber factor of 0.96 was observed to change the failure mode from shear failure to flexural failure. The results of this study support the inclusion of provisions for steel fiber-reinforced concrete in building codes and provides recommendations for inclusion in ACI 318-14 and Eurocode 2, so that a wider adoption of steel fiber reinforced concrete can be achieved in the construction industry. Full article
(This article belongs to the Special Issue Steel Fibre Reinforced Concrete Behaviour)
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13 pages, 1732 KiB  
Article
An Aging Evaluation of the Bearing Performances of Glass Fiber Composite Laminate in Salt Spray Fog Environment
by Luigi Calabrese, Vincenzo Fiore, Paolo Giovanni Bruzzaniti, Tommaso Scalici and Antonino Valenza
Fibers 2019, 7(11), 96; https://doi.org/10.3390/fib7110096 - 31 Oct 2019
Cited by 10 | Viewed by 5532
Abstract
The aim of the present paper is to assess the bearing performance evolution of pinned, glass-composite laminates due to environmental aging in salt-spray fog tests. Glass fibers/epoxy pinned laminates were exposed for up to 60 days in salt-spraying, foggy environmental conditions (according to [...] Read more.
The aim of the present paper is to assess the bearing performance evolution of pinned, glass-composite laminates due to environmental aging in salt-spray fog tests. Glass fibers/epoxy pinned laminates were exposed for up to 60 days in salt-spraying, foggy environmental conditions (according to ASTM B117 standard). In order to evaluate the relationship between mechanical failure mode and joint stability over increasing aging time, different single lap joints, measured by the changing hole diameter (D), laminate width (W) and hole free edge distance (E), were characterized at varying aging steps. Based on this approach, the property-structure relationship of glass-fibers/epoxy laminates was assessed under these critical environmental conditions. Furthermore, an experimental 2D failure map, clustering main failure modes in the plane E/D versus W/D ratios, was generated, and its cluster variation was analyzed at each degree of aging. Full article
(This article belongs to the Special Issue Advances in Glass Fibers)
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24 pages, 1996 KiB  
Article
ANN-Based Shear Capacity of Steel Fiber-Reinforced Concrete Beams without Stirrups
by Miguel Abambres and Eva O.L. Lantsoght
Fibers 2019, 7(10), 88; https://doi.org/10.3390/fib7100088 - 11 Oct 2019
Cited by 26 | Viewed by 7032
Abstract
Comparing experimental results of the shear capacity of steel fiber-reinforced concrete (SFRC) beams without stirrups to the capacity predicted using current design equations and other available formulations shows that predicting the shear capacity of SFRC beams without mild steel shear reinforcement is still [...] Read more.
Comparing experimental results of the shear capacity of steel fiber-reinforced concrete (SFRC) beams without stirrups to the capacity predicted using current design equations and other available formulations shows that predicting the shear capacity of SFRC beams without mild steel shear reinforcement is still difficult. The reason for this difficulty is the complex mechanics of the problem, where the steel fibers affect the different shear-carrying mechanisms. Since this problem is still not fully understood, we propose the use of artificial intelligence (AI) to derive an expression based on the available experimental data. We used a database of 430 datapoints obtained from the literature. The outcome is an artificial neural network-based expression to predict the shear capacity of SFRC beams without shear reinforcement. For this purpose, many thousands of artificial neural network (ANN) models were generated, based on 475 distinct combinations of 15 typical ANN features. The proposed “optimal” model results in maximum and mean relative errors of 0.0% for the 430 datapoints. The proposed model results in a better prediction (mean Vtest/VANN = 1.00 with a coefficient of variation 1 × 10−15) as compared to the existing code expressions and other available empirical expressions, with the model by Kwak et al. giving a mean value of Vtest/Vpred = 1.01 and a coefficient of variation of 27%. Until mechanics-based models are available for predicting the shear capacity of SFRC beams without shear reinforcement, the proposed model thus offers an attractive solution for estimating the shear capacity of SFRC beams without shear reinforcement. With this approach, designers who may be reluctant to use SFRC because of the large uncertainties and poor predictions of experiments, may feel more confident using the material for structural design. Full article
(This article belongs to the Special Issue Steel Fibre Reinforced Concrete Behaviour)
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8 pages, 1864 KiB  
Article
Borosilicate Based Hollow-Core Optical Fibers
by Walter Belardi and Pier John Sazio
Fibers 2019, 7(8), 73; https://doi.org/10.3390/fib7080073 - 11 Aug 2019
Cited by 21 | Viewed by 8584
Abstract
We discuss the fabrication of hollow-core optical fibers made of borosilicate glass. We show that, despite the high attenuation of the glass relative to silica, the fiber optical losses can be of the same order of magnitude of those obtained by using ultrapure [...] Read more.
We discuss the fabrication of hollow-core optical fibers made of borosilicate glass. We show that, despite the high attenuation of the glass relative to silica, the fiber optical losses can be of the same order of magnitude of those obtained by using ultrapure silica glass. Short lengths of the fabricated fibers, used in combination with incoherent optical sources, provide single-mode optical guidance in both near and mid-infrared spectral ranges without any additional optical components. Full article
(This article belongs to the Special Issue Hollow-Core Photonic Crystal Fibers)
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35 pages, 3540 KiB  
Review
Multi-Functional Electrospun Nanofibers from Polymer Blends for Scaffold Tissue Engineering
by Samerender Nagam Hanumantharao and Smitha Rao
Fibers 2019, 7(7), 66; https://doi.org/10.3390/fib7070066 - 19 Jul 2019
Cited by 68 | Viewed by 14805
Abstract
Electrospinning and polymer blending have been the focus of research and the industry for their versatility, scalability, and potential applications across many different fields. In tissue engineering, nanofiber scaffolds composed of natural fibers, synthetic fibers, or a mixture of both have been reported. [...] Read more.
Electrospinning and polymer blending have been the focus of research and the industry for their versatility, scalability, and potential applications across many different fields. In tissue engineering, nanofiber scaffolds composed of natural fibers, synthetic fibers, or a mixture of both have been reported. This review reports recent advances in polymer blended scaffolds for tissue engineering and the fabrication of functional scaffolds by electrospinning. A brief theory of electrospinning and the general setup as well as modifications used are presented. Polymer blends, including blends with natural polymers, synthetic polymers, mixture of natural and synthetic polymers, and nanofiller systems, are discussed in detail and reviewed. Full article
(This article belongs to the Special Issue Electrospun Fibers for Scaffold and Electrical Sensing)
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9 pages, 1995 KiB  
Article
Tensile Behavior of Unidirectional Bamboo/Coir Fiber Hybrid Composites
by Le Quan Ngoc Tran, Carlos Fuentes, Ignace Verpoest and Aart Willem Van Vuure
Fibers 2019, 7(7), 62; https://doi.org/10.3390/fib7070062 - 10 Jul 2019
Cited by 16 | Viewed by 7349
Abstract
Natural fibers, such as bamboo, flax, hemp, and coir, are usually different in terms of microstructure and chemical composition. The mechanical properties of natural fibers strongly depend on the organization of cell walls and the cellulose micro-fibril angle in the dominant cell wall [...] Read more.
Natural fibers, such as bamboo, flax, hemp, and coir, are usually different in terms of microstructure and chemical composition. The mechanical properties of natural fibers strongly depend on the organization of cell walls and the cellulose micro-fibril angle in the dominant cell wall layers. Bamboo, flax, and hemp are known for high strength and stiffness, while coir has high elongation to failure. Based on the unique properties of the fibers, fiber hybridization is expected to combine the advantages of different natural fibers for composite applications. In this paper, a study on bamboo/coir fiber hybrid composites was carried out to investigate the hybrid effect of tough coir fibers and brittle bamboo fibers in the composites. The tensile behavior of unidirectional composites of bamboo fibers, coir fibers, and hybrid bamboo/coir fibers with a thermoplastic matrix was studied. The correlation between the tensile properties of the fibers and of the hybrid composites was analyzed to understand the hybrid effects. In addition, the failure mode and fracture morphology of the hybrid composites were examined. The results suggested that, with a low bamboo fiber fraction, a positive hybrid effect with an increase of composite strain to failure was obtained, which can be attributed to the high strain to failure of the coir fibers; the bamboo fibers provided high stiffness and strength to the composites. Full article
(This article belongs to the Special Issue Natural Fiber-Reinforced Hybrid Composites)
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10 pages, 4072 KiB  
Article
Electrospun Nanofiber Mats with Embedded Non-Sintered TiO2 for Dye-Sensitized Solar Cells (DSSCs)
by Al Mamun, Marah Trabelsi, Michaela Klöcker, Lilia Sabantina, Christina Großerhode, Tomasz Blachowicz, Georg Grötsch, Carsten Cornelißen, Almuth Streitenberger and Andrea Ehrmann
Fibers 2019, 7(7), 60; https://doi.org/10.3390/fib7070060 - 4 Jul 2019
Cited by 23 | Viewed by 7145
Abstract
TiO2 is a semiconductor that is commonly used in dye-sensitized solar cells (DSSCs). However, the necessity of sintering the TiO2 layer is usually problematic due to the desired temperatures of typically 500 °C in cells that are prepared on polymeric or [...] Read more.
TiO2 is a semiconductor that is commonly used in dye-sensitized solar cells (DSSCs). However, the necessity of sintering the TiO2 layer is usually problematic due to the desired temperatures of typically 500 °C in cells that are prepared on polymeric or textile electrodes. This is why textile-based DSSCs often use metal fibers or metallic woven fabrics as front electrodes on which the TiO2 is coated. Alternatively, several research groups investigate the possibilities to reduce the necessary sintering temperatures by chemical or other pre-treatments of the TiO2. Here, we report on a simple method to avoid the sintering step by using a nanofiber mat as a matrix embedding TiO2 nanoparticles. The TiO2 layer can be dyed with natural dyes, resulting in a similar bathochromic shift of the UV/Vis spectrum, as it is known from sintered TiO2 on glass substrates, which indicates an equivalent chemical bonding. Our results indicate a new possibility for producing textile-based DSSCs with TiO2, even on textile fabrics that are not high-temperature resistant. Full article
(This article belongs to the Special Issue Functional Fibers for Next-Generation Flexible Technologies)
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14 pages, 3061 KiB  
Article
Cotton Cellulose-CdTe Quantum Dots Composite Films with Inhibition of Biofilm-Forming S. aureus
by Rohan S. Dassanayake, Poorna T. Wansapura, Phat Tran, Abdul Hamood and Noureddine Abidi
Fibers 2019, 7(6), 57; https://doi.org/10.3390/fib7060057 - 19 Jun 2019
Cited by 8 | Viewed by 6163
Abstract
A cellulose-cadmium (Cd)-tellurium (TE) quantum dots (QDs) composite film was successfully synthesized by incorporating CdTe QDs onto a cellulose matrix derived from waste cotton linters. Cellulose-CdTe QDs composite film was characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) spectroscopy, [...] Read more.
A cellulose-cadmium (Cd)-tellurium (TE) quantum dots (QDs) composite film was successfully synthesized by incorporating CdTe QDs onto a cellulose matrix derived from waste cotton linters. Cellulose-CdTe QDs composite film was characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and X-ray diffraction (XRD). The antibacterial activity of the prepared composite film was investigated using the multidrug-resistance (MTR) Staphylococcus aureus bacteria. In vitro antibacterial assays demonstrated that CdTe QDs composite film can efficiently inhibit biofilm formation. Our results showed that the cellulose-CdTe QDs composite film is a promising candidate for biomedical applications including wound dressing, medical instruments, burn treatments, implants, and other biotechnology fields. Full article
(This article belongs to the Special Issue Recent Progress in Cellulose Dissolution and Regeneration)
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46 pages, 8667 KiB  
Review
Electrically Conductive Coatings for Fiber-Based E-Textiles
by Kony Chatterjee, Jordan Tabor and Tushar K. Ghosh
Fibers 2019, 7(6), 51; https://doi.org/10.3390/fib7060051 - 1 Jun 2019
Cited by 73 | Viewed by 22653
Abstract
With the advent of wearable electronic devices in our daily lives, there is a need for soft, flexible, and conformable devices that can provide electronic capabilities without sacrificing comfort. Electronic textiles (e-textiles) combine electronic capabilities of devices such as sensors, actuators, energy harvesting [...] Read more.
With the advent of wearable electronic devices in our daily lives, there is a need for soft, flexible, and conformable devices that can provide electronic capabilities without sacrificing comfort. Electronic textiles (e-textiles) combine electronic capabilities of devices such as sensors, actuators, energy harvesting and storage devices, and communication devices with the comfort and conformability of conventional textiles. An important method to fabricate such devices is by coating conventionally used fibers and yarns with electrically conductive materials to create flexible capacitors, resistors, transistors, batteries, and circuits. Textiles constitute an obvious choice for deployment of such flexible electronic components due to their inherent conformability, strength, and stability. Coating a layer of electrically conducting material onto the textile can impart electronic capabilities to the base material in a facile manner. Such a coating can be done at any of the hierarchical levels of the textile structure, i.e., at the fiber, yarn, or fabric level. This review focuses on various electrically conducting materials and methods used for coating e-textile devices, as well as the different configurations that can be obtained from such coatings, creating a smart textile-based system. Full article
(This article belongs to the Special Issue Smart Coatings on Fibers and Textiles)
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14 pages, 3410 KiB  
Article
Development of Oxygen-Plasma-Surface-Treated UHMWPE Fabric Coated with a Mixture of SiC/Polyurethane for Protection against Puncture and Needle Threats
by Dariush Firouzi, Chan Y. Ching, Syed N. Rizvi and P. Ravi Selvaganapathy
Fibers 2019, 7(5), 46; https://doi.org/10.3390/fib7050046 - 20 May 2019
Cited by 14 | Viewed by 7599
Abstract
Although considerable research has been directed at developing materials for ballistic protection, considerably less has been conducted to address non-firearm threats. Even fewer studies have examined the incorporation of particle-laden elastomers with textiles for spike, knife, and needle protection. We report on a [...] Read more.
Although considerable research has been directed at developing materials for ballistic protection, considerably less has been conducted to address non-firearm threats. Even fewer studies have examined the incorporation of particle-laden elastomers with textiles for spike, knife, and needle protection. We report on a new composite consisting of ultra-high-molecular-weight polyethylene (UHMWPE) fabric impregnated with nanoparticle-loaded elastomer, specifically designed for spike- and needle-resistant garments. Failure analysis and parametric studies of particle-loading and layer-count were conducted using a mixture of SiC and polyurethane at 0, 30, and 50 wt.%. The maximum penetration resistance force of a single-layer of uncoated fabric increased up to 218–229% due to nanoparticle loading. Multiple-layer stacks of coated fabric show up to 57% and 346% improvement in spike puncture and hypodermic needle resistance, respectively, and yet were more flexible and 21–55% thinner than a multiple-layer stack of neat fabric (of comparable areal density). We show that oxygen-plasma-treatment of UHMWPE is critical to enable effective coating. Full article
(This article belongs to the Special Issue Smart Coatings on Fibers and Textiles)
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18 pages, 4333 KiB  
Review
A Brief Review of Nanocellulose Based Hybrid Membranes for CO2 Separation
by Zhongde Dai, Vegar Ottesen, Jing Deng, Ragne M. Lilleby Helberg and Liyuan Deng
Fibers 2019, 7(5), 40; https://doi.org/10.3390/fib7050040 - 6 May 2019
Cited by 52 | Viewed by 11311
Abstract
Due to the high specific surface area, high mechanical strength and broad possibility of surface modification, nanocellulose has obtained much attention as a new class of bio-based nanomaterials with promising potential in a wide variety of applications. Recently, a considerable amount of research [...] Read more.
Due to the high specific surface area, high mechanical strength and broad possibility of surface modification, nanocellulose has obtained much attention as a new class of bio-based nanomaterials with promising potential in a wide variety of applications. Recently, a considerable amount of research has been aimed to the fabrication of nanocellulose based hybrid membranes for water treatment. However, nanocellulose based hybrid gas separation membrane is still a new research area. Herein, we force on recent advancements in the fabrication methods and separation performances of nanocellulose-based hybrid membranes for CO2 separation, the transport mechanisms involved, along with the challenges in the utilization of nanocellulose in membranes. Finally, some perspectives on future R&D of nanocellulose-based membranes for CO2 separation are proposed. Full article
(This article belongs to the Special Issue Polymer Hollow Fiber Membrane 2019)
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9 pages, 3158 KiB  
Article
Fabrication of Water Absorbing Nanofiber Meshes toward an Efficient Removal of Excess Water from Kidney Failure Patients
by Mirei Tsuge, Kanoko Takahashi, Rio Kurimoto, Ailifeire Fulati, Koichiro Uto, Akihiko Kikuchi and Mitsuhiro Ebara
Fibers 2019, 7(5), 39; https://doi.org/10.3390/fib7050039 - 1 May 2019
Cited by 10 | Viewed by 8949
Abstract
Excellent water-absorbing nanofiber meshes were developed as a potential material for removing excess fluids from the blood of chronic renal failure patients toward a wearable blood purification system without requiring specialized equipment. The nanofiber meshes were successfully fabricated from poly(acrylic acid) (PAA) under [...] Read more.
Excellent water-absorbing nanofiber meshes were developed as a potential material for removing excess fluids from the blood of chronic renal failure patients toward a wearable blood purification system without requiring specialized equipment. The nanofiber meshes were successfully fabricated from poly(acrylic acid) (PAA) under various applied voltages by appropriately setting the electrospinning conditions. The electrospun PAA nanofibers were thermally crosslinked via heat treatment and then neutralized from their carboxylic acid form (PAA) to a sodium carboxylate form poly(sodium acrylate) (PSA). The PSA nanofiber meshes exhibited a specific surface area 393 times that of the PSA film. The PSA fiber meshes showed a much faster and higher swelling than its corresponding film, owing to the higher capillary forces from the fibers in addition to the water absorption of the PSA gel itself. The proposed PSA fibers have the potential to be utilized in a new approach to remove excess water from the bloodstream without requiring specialized equipment. Full article
(This article belongs to the Special Issue Electrospun Polymer Nanofibers for Food and Health Applications)
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10 pages, 1778 KiB  
Article
Fabrication of a Fluorophore-Doped Cylindrical Waveguide Structure Using Elastomers for Visual Detection of Stress
by Chie Hirose, Nobuko Fukuda, Takafumi Sassa, Koji Ishibashi, Tsuyoshi Ochiai and Rei Furukawa
Fibers 2019, 7(5), 37; https://doi.org/10.3390/fib7050037 - 26 Apr 2019
Cited by 6 | Viewed by 5727
Abstract
A fiber-optic strain sensor that can show strain via color change and which can be viewed using human eyes has demand in the civil engineering field for alerting purposes. A previous sensor was fabricated using PMMA (Poly(methyl methacrylate)), which had the exceeding hardness [...] Read more.
A fiber-optic strain sensor that can show strain via color change and which can be viewed using human eyes has demand in the civil engineering field for alerting purposes. A previous sensor was fabricated using PMMA (Poly(methyl methacrylate)), which had the exceeding hardness to exhibit satisfactory sensor performance. In this research, an elastomer-based fiber-optic structure was fabricated to enhance the elastic response of such sensors and to enlarge the waveguide cross section. Various organic fluorophores were added to the core and cladding regions of the elastic waveguide to induce energy flow from the core to the cladding when stress is applied to the waveguide. Elastomer pairs suitable for the core and cladding were selected from among several candidate materials having high transparency. A method of dispersing fluorophores to each host elastomer and constructing an excellent core–cladding interface using the selected materials was proposed. To investigate the time-dependent changes in the fluorescence of the doped elastomer waveguide, the absorption and emission spectra were monitored after the host elastomers were cured. Full article
(This article belongs to the Special Issue Functional Fibers for Next-Generation Flexible Technologies)
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7 pages, 2441 KiB  
Article
A Novel Approach to Realizing Low-Cost Plasmonic Optical Fiber Sensors: Light-Diffusing Fibers Covered by Thin Metal Films
by Nunzio Cennamo, Luigi Zeni, Francesco Arcadio, Ester Catalano and Aldo Minardo
Fibers 2019, 7(4), 34; https://doi.org/10.3390/fib7040034 - 17 Apr 2019
Cited by 15 | Viewed by 5400
Abstract
We have investigated, in a numerical and experimental way, a refractive index (RI) sensor based on surface plasmon resonance (SPR) in a silver-coated light-diffusing fiber (LDF). The experimental tests were conducted using water-glycerine mixtures with refractive indices ranging from 1.332 to 1.388. In [...] Read more.
We have investigated, in a numerical and experimental way, a refractive index (RI) sensor based on surface plasmon resonance (SPR) in a silver-coated light-diffusing fiber (LDF). The experimental tests were conducted using water-glycerine mixtures with refractive indices ranging from 1.332 to 1.388. In the considered refractive index range, the experimental results show a sensitivity of the SPR wavelength to the outer medium’s RI ranging from ~2600 to ~4700 nm/RIU, which is larger than the sensitivity recently reported for a gold-coated LDF sensor (~1200 to ~4000 nm/RIU). The silver-coated sensor is also shown to ensure a higher signal-to-noise ratio (SNR) compared to the gold-coated sensor. Full article
(This article belongs to the Special Issue Optical Fibers Sensors 2019)
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16 pages, 15900 KiB  
Article
Quasi-Static and Low-Velocity Impact Behavior of Intraply Hybrid Flax/Basalt Composites
by Fabrizio Sarasini, Jacopo Tirillò, Luca Ferrante, Claudia Sergi, Pietro Russo, Giorgio Simeoli, Francesca Cimino, Maria Rosaria Ricciardi and Vincenza Antonucci
Fibers 2019, 7(3), 26; https://doi.org/10.3390/fib7030026 - 22 Mar 2019
Cited by 25 | Viewed by 7532
Abstract
In an attempt to increase the low-velocity impact response of natural fiber composites, a new hybrid intraply woven fabric based on flax and basalt fibers has been used to manufacture laminates with both thermoplastic and thermoset matrices. The matrix type (epoxy or polypropylene [...] Read more.
In an attempt to increase the low-velocity impact response of natural fiber composites, a new hybrid intraply woven fabric based on flax and basalt fibers has been used to manufacture laminates with both thermoplastic and thermoset matrices. The matrix type (epoxy or polypropylene (PP) with or without a maleated coupling agent) significantly affected the absorbed energy and the damage mechanisms. The absorbed energy at perforation for PP-based composites was 90% and 50% higher than that of epoxy and compatibilized PP composites, respectively. The hybrid fiber architecture counteracted the influence of low transverse strength of flax fibers on impact response, irrespective of the matrix type. In thermoplastic laminates, the matrix plasticization delayed the onset of major damage during impact and allowed a better balance of quasi-static properties, energy absorption, peak force, and perforation energy compared to epoxy-based composites. Full article
(This article belongs to the Special Issue Natural Fiber-Reinforced Hybrid Composites)
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13 pages, 1835 KiB  
Review
Mineralogical Asbestos Assessment in the Southern Apennines (Italy): A Review
by Maria Carmela Dichicco, Michele Paternoster, Giovanna Rizzo and Rosa Sinisi
Fibers 2019, 7(3), 24; https://doi.org/10.3390/fib7030024 - 19 Mar 2019
Cited by 19 | Viewed by 5185
Abstract
This paper deals with petrography and mineralogy of serpentinitic rocks occurring in the Southern Apennines (Italy) with the aim to review the already available literature data and furnish new details on asbestos minerals present in the studied area. Two sites of Southern Italy [...] Read more.
This paper deals with petrography and mineralogy of serpentinitic rocks occurring in the Southern Apennines (Italy) with the aim to review the already available literature data and furnish new details on asbestos minerals present in the studied area. Two sites of Southern Italy were taken into account: the Pollino Massif, at the Calabrian-Lucanian border, and the surroundings of the Gimigliano and Mt. Reventino areas where serpentinites of Frido Unit are mainly exposed. Textural and mineralogical features of the studied rocks point to a similar composition for both sites including asbestos minerals such as chrysotile and tremolite-actinolite series mineral phases. Only in the Pollino Massif serpentinites edenite crystals have been detected as well; they are documented here for the first time. This amphibole forms as fibrous and/or prismatic crystals in aggregates associated with serpentine, pyroxene, and calcite. Metamorphism and/or metasomatic alteration of serpentinites are the most probable processes promoting the edenite formation in the Southern Apennine ophiolitic rocks. Full article
(This article belongs to the Special Issue Mineral Fibres)
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18 pages, 3099 KiB  
Article
Dissolution Kinetics of R-Glass Fibres: Influence of Water Acidity, Temperature, and Stress Corrosion
by Andrey E. Krauklis, Abedin I. Gagani, Kristine Vegere, Ilze Kalnina, Maris Klavins and Andreas T. Echtermeyer
Fibers 2019, 7(3), 22; https://doi.org/10.3390/fib7030022 - 12 Mar 2019
Cited by 21 | Viewed by 6570
Abstract
Glass fibres slowly degrade due to dissolution when exposed to water. Such environmental aging results in the deterioration of the mechanical properties. In structural offshore and marine applications, as well as in the wind energy sector, R-glass fibre composites are continuously exposed to [...] Read more.
Glass fibres slowly degrade due to dissolution when exposed to water. Such environmental aging results in the deterioration of the mechanical properties. In structural offshore and marine applications, as well as in the wind energy sector, R-glass fibre composites are continuously exposed to water and humid environments for decades, with a typical design lifetime being around 25 years or more. During this lifetime, these materials are affected by various temperatures, acidity levels, and mechanical loads. A Dissolving Cylinder Zero-Order Kinetic (DCZOK) model was able to explain the long-term dissolution of R-glass fibres, considering the influence of the p H , temperature, and stress corrosion. The effects of these environmental conditions on the dissolution rate constants and activation energies of dissolution were obtained. Experimentally, dissolution was measured using High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS). For stress corrosion, a custom rig was designed and used. The temperature showed an Arrhenius-type influence on the kinetics, increasing the rate of dissolution exponentially with increasing temperature. In comparison with neutral conditions, basic and acidic aqueous environments showed an increase in the dissolution rates, affecting the lifetime of glass fibres negatively. External loads also increased glass dissolution rates due to stress corrosion. The model was able to capture all of these effects. Full article
(This article belongs to the Special Issue Advances in Glass Fibers)
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24 pages, 5057 KiB  
Review
Actuator Materials: Review on Recent Advances and Future Outlook for Smart Textiles
by Dharshika Kongahage and Javad Foroughi
Fibers 2019, 7(3), 21; https://doi.org/10.3390/fib7030021 - 11 Mar 2019
Cited by 66 | Viewed by 16200
Abstract
Smart textiles based on actuator materials are of practical interest, but few types have been commercially exploited. The challenge for researchers has been to bring the concept out of the laboratory by working out how to build these smart materials on an industrial [...] Read more.
Smart textiles based on actuator materials are of practical interest, but few types have been commercially exploited. The challenge for researchers has been to bring the concept out of the laboratory by working out how to build these smart materials on an industrial scale and permanently incorporate them into textiles. Smart textiles are considered as the next frontline for electronics. Recent developments in advance technologies have led to the appearance of wearable electronics by fabricating, miniaturizing and embedding flexible conductive materials into textiles. The combination of textiles and smart materials have contributed to the development of new capabilities in fabrics with the potential to change how athletes, patients, soldiers, first responders, and everyday consumers interact with their clothes and other textile products. Actuating textiles in particular, have the potential to provide a breakthrough to the area of smart textiles in many ways. The incorporation of actuating materials in to textiles is a striking approach as a small change in material anisotropy properties can be converted into significant performance enhancements, due to the densely interconnected structures. Herein, the most recent advances in smart materials based on actuating textiles are reviewed. The use of novel emerging twisted synthetic yarns, conducting polymers, hybrid carbon nanotube and spandex yarn actuators, as well as most of the cutting–edge polymeric actuators which are deployed as smart textiles are discussed. Full article
(This article belongs to the Special Issue Smart Coatings on Fibers and Textiles)
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12 pages, 25501 KiB  
Article
Assessment of Serpentine Group Minerals in Soils: A Case Study from the Village of San Severino Lucano (Basilicata, Southern Italy)
by Rosalda Punturo, Claudia Ricchiuti and Andrea Bloise
Fibers 2019, 7(2), 18; https://doi.org/10.3390/fib7020018 - 25 Feb 2019
Cited by 9 | Viewed by 6145
Abstract
Naturally occurring asbestos (NOA) is a generic term used to refer to both regulated and un-regulated fibrous minerals when encountered in natural geological deposits. These minerals represent a cause of health hazard, since they have been assessed as potential environmental pollutants that may [...] Read more.
Naturally occurring asbestos (NOA) is a generic term used to refer to both regulated and un-regulated fibrous minerals when encountered in natural geological deposits. These minerals represent a cause of health hazard, since they have been assessed as potential environmental pollutants that may occur both in rocks and derived soils. In the present work, we focused on the village of San Severino Lucano, located in the Basilicata region (southern Apennines); due to its geographic isolation from other main sources of asbestos, it represents an excellent example of hazardous and not occupational exposure of population. From the village and its surroundings, we collected eight serpentinite-derived soil samples and carried out Differential Scanning Calorimetry (DSC), Derivative Thermogravimetric (DTG) and Transmission Electron Microscopy with Energy Dispersive Spectrometry (TEM-EDS), in order to perform a detailed characterization of serpentine varieties and other fibrous minerals. Investigation pointed out that chrysotile and asbestos tremolite occur in all of the samples. As for the fibrous but non-asbestos classified minerals, polygonal serpentine and fibrous antigorite were detected in a few samples. Results showed that the cultivation of soils developed upon serpentinite bedrocks were rich in harmful minerals, which if dispersed in the air can be a source of environmental pollution. Full article
(This article belongs to the Special Issue Mineral Fibres)
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58 pages, 15866 KiB  
Review
Hollow-Core Fiber Technology: The Rising of “Gas Photonics”
by Benoît Debord, Foued Amrani, Luca Vincetti, Frédéric Gérôme and Fetah Benabid
Fibers 2019, 7(2), 16; https://doi.org/10.3390/fib7020016 - 18 Feb 2019
Cited by 149 | Viewed by 19502
Abstract
Since their inception, about 20 years ago, hollow-core photonic crystal fiber and its gas-filled form are now establishing themselves both as a platform in advancing our knowledge on how light is confined and guided in microstructured dielectric optical waveguides, and a remarkable enabler [...] Read more.
Since their inception, about 20 years ago, hollow-core photonic crystal fiber and its gas-filled form are now establishing themselves both as a platform in advancing our knowledge on how light is confined and guided in microstructured dielectric optical waveguides, and a remarkable enabler in a large and diverse range of fields. The latter spans from nonlinear and coherent optics, atom optics and laser metrology, quantum information to high optical field physics and plasma physics. Here, we give a historical account of the major seminal works, we review the physics principles underlying the different optical guidance mechanisms that have emerged and how they have been used as design tools to set the current state-of-the-art in the transmission performance of such fibers. In a second part of this review, we give a nonexhaustive, yet representative, list of the different applications where gas-filled hollow-core photonic crystal fiber played a transformative role, and how the achieved results are leading to the emergence of a new field, which could be coined “Gas photonics”. We particularly stress on the synergetic interplay between glass, gas, and light in founding this new fiber science and technology. Full article
(This article belongs to the Special Issue Hollow Core Optical Fibers)
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21 pages, 9593 KiB  
Article
Continuous Fiber Angle Topology Optimization for Polymer Composite Deposition Additive Manufacturing Applications
by Delin Jiang, Robert Hoglund and Douglas E. Smith
Fibers 2019, 7(2), 14; https://doi.org/10.3390/fib7020014 - 1 Feb 2019
Cited by 78 | Viewed by 10579
Abstract
Mechanical properties of parts produced with polymer deposition additive manufacturing (AM) depend on the print bead direction, particularly when short carbon-fiber reinforcement is added to the polymer feedstock. This offers a unique opportunity in the design of these structures since the AM print [...] Read more.
Mechanical properties of parts produced with polymer deposition additive manufacturing (AM) depend on the print bead direction, particularly when short carbon-fiber reinforcement is added to the polymer feedstock. This offers a unique opportunity in the design of these structures since the AM print path can potentially be defined in a direction that takes advantage of the enhanced stiffness gained in the bead and, therefore, fiber direction. This paper presents a topology optimization approach for continuous fiber angle optimization (CFAO), which computes the best layout and orientation of fiber reinforcement for AM structures. Statically loaded structures are designed for minimum compliance where the adjoint variable method is used to compute design derivatives, and a sensitivity filter is employed to reduce the checkerboard effect. The nature of the layer-by-layer approach in AM is given special consideration in the algorithm presented. Examples are provided to demonstrate the applicability of the method in both two and three dimensions. The solution to our two dimensional problem is then printed with a fused filament fabrication (FFF) desktop printer using the material distribution results and a simple infill method which approximates the optimal fiber angle results using a contour-parallel deposition strategy. Mechanical stiffness testing of the printed parts shows improved results as compared to structures designed without accounting for the direction of the composite structure. Results show that the mechanical properties of the final FFF carbon fiber/polymer composite printed parts are greatly influenced by the print direction, and optimized material orientation tends to align with the imposed force direction to minimize the compliance. Full article
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17 pages, 3685 KiB  
Article
A Novel Method for Embedding Semiconductor Dies within Textile Yarn to Create Electronic Textiles
by Mohamad-Nour Nashed, Dorothy Anne Hardy, Theodore Hughes-Riley and Tilak Dias
Fibers 2019, 7(2), 12; https://doi.org/10.3390/fib7020012 - 26 Jan 2019
Cited by 24 | Viewed by 9411
Abstract
Electronic yarns (E-yarns) contain electronics fully incorporated into the yarn’s structure prior to textile or garment production. They consist of a conductive core made from a flexible, multi-strand copper wire onto which semiconductor dies or MEMS (microelectromechanical systems) are soldered. The device and [...] Read more.
Electronic yarns (E-yarns) contain electronics fully incorporated into the yarn’s structure prior to textile or garment production. They consist of a conductive core made from a flexible, multi-strand copper wire onto which semiconductor dies or MEMS (microelectromechanical systems) are soldered. The device and solder joints are then encapsulated within a resin micro-pod, which is subsequently surrounded by a textile sheath, which also covers the copper wires. The encapsulation of semiconductor dies or MEMS devices within the resin polymer micro-pod is a critical component of the fabrication process, as the micro-pod protects the dies from mechanical and chemical stresses, and hermetically seals the device, which makes the E-yarn washable. The process of manufacturing E-yarns requires automation to increase production speeds and to ensure consistency of the micro-pod structure. The design and development of a semi-automated encapsulation unit used to fabricate the micro-pods is presented here. The micro-pods were made from a ultra-violet (UV) curable polymer resin. This work details the choice of machinery and methods to create a semi-automated encapsulation system in which incoming dies were detected then covered in resin micro-pods. The system detected incoming 0402 metric package dies with an accuracy of 87 to 98%. Full article
(This article belongs to the Special Issue Electronically Active Textiles)
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13 pages, 8889 KiB  
Article
Mechanical Properties of Concrete with Steel and Polypropylene Fibres at Elevated Temperatures
by Josipa Bošnjak, Akanshu Sharma and Kevin Grauf
Fibers 2019, 7(2), 9; https://doi.org/10.3390/fib7020009 - 24 Jan 2019
Cited by 48 | Viewed by 8990
Abstract
Addition of steel fibres to concrete is known to have a significant positive influence on the mechanical properties of concrete. Micro polypropylene (PP) fibres are added to concrete to improve its performance under thermal loads such as in case of fire by preventing [...] Read more.
Addition of steel fibres to concrete is known to have a significant positive influence on the mechanical properties of concrete. Micro polypropylene (PP) fibres are added to concrete to improve its performance under thermal loads such as in case of fire by preventing the phenomena of explosive spalling. An optimum mixture of steel and micro PP fibres added to concrete may be utilized to enhance both the mechanical and thermal behaviour of concrete. In this work, systematic investigations were carried out to study the influence of elevated temperature on the mechanical properties and physical properties of high strength concrete without and with fibres. Three different mixtures for high strength concrete were used, namely normal concrete without fibres, Steel fibre reinforced concrete and Hybrid fibre reinforced concrete having a blend of hooked end steel fibres and micro PP fibres. The specimens were tested in ambient conditions as well as after exposure to a pre-defined elevated temperature and cooling down to room temperature. For all investigated concrete mixtures the thermal degradation of following properties were investigated: compressive strength, tensile splitting strength, bending strength, fracture energy and static modulus of elasticity. This paper summarizes the findings of the tests performed. Full article
(This article belongs to the Special Issue Recent Advancements in Fiber Reinforced Concrete And its Applications)
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17 pages, 2737 KiB  
Article
Surface Modified Polysulfone Hollow Fiber Membranes for Ethane/Ethylene Separation Using Gas-Liquid Membrane Contactors with Ionic Liquid-Based Absorbent
by Margarita Kostyanaya, Stepan Bazhenov, Ilya Borisov, Tatiana Plisko and Vladimir Vasilevsky
Fibers 2019, 7(1), 4; https://doi.org/10.3390/fib7010004 - 4 Jan 2019
Cited by 13 | Viewed by 7155
Abstract
Olefin/paraffin separation is an important technological process. A promising alternative to conventional energy-consuming methods is employment of gas-liquid membrane contactors. In the present work, the membranes used were polysulfone (PSf) asymmetrical porous hollow fibers fabricated via the NIPS (non-solvent induced phase separation) technique [...] Read more.
Olefin/paraffin separation is an important technological process. A promising alternative to conventional energy-consuming methods is employment of gas-liquid membrane contactors. In the present work, the membranes used were polysulfone (PSf) asymmetrical porous hollow fibers fabricated via the NIPS (non-solvent induced phase separation) technique in the free spinning mode. The surface of the fine-pored selective layer from the lumen side of the fibers was modified by layer-by-layer deposition of perfluorinated acrylic copolymer Protect Guard® in order to hydrophobized the surface and to avoid penetration of the liquid absorbent in the porous structure of the membranes. The absorbents studied were silver salts (AgNO3 and AgBF4) solutions in five ionic liquids (ILs) based on imidazolium and phosphonium cations. The membranes were analyzed through gas permeance measurement, SEM and dispersive X-ray (EDXS). Contact angle values of both unmodified and modified membranes were determined for water, ethylene glycol, ILs and silver salts solutions in ILs. It was shown that the preferable properties for employment in membrane contactor refer to the PSf hollow fiber membranes modified by two layers of Protect Guard®, and to the absorbent based on 1 M AgNO3 solution in 1-ethyl-3-methylimidazolium dicyanamide. Using the membrane contactor designed, ethylene/ethane mixture (80/20) separation was carried out. The fluxes of both components as well as their overall mass transport coefficients (MTC) were calculated. It was shown that the membrane absorption system developed provides absorption of approx. 37% of the initial ethylene volume in the mixture. The overall MTC value for ethylene was 4.7 GPU (gas permeance unit). Full article
(This article belongs to the Special Issue Polymer Hollow Fiber Membrane 2019)
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18 pages, 2238 KiB  
Article
Utilization of Recycled Material Sources for Wood-Polypropylene Composites: Effect on Internal Composite Structure, Particle Characteristics and Physico-Mechanical Properties
by Kim Christian Krause, Philipp Sauerbier, Tim Koddenberg and Andreas Krause
Fibers 2018, 6(4), 86; https://doi.org/10.3390/fib6040086 - 7 Nov 2018
Cited by 21 | Viewed by 7399
Abstract
In this study, various wood material sources were used for the manufacture of wood-polymer composites (WPC). The materials were categorised as virgin wood particles (VWP), reprocessed WPC particles (RWP) and recycled thermoset composite particles (RCP) and derived from two virgin wood sources, three-layer [...] Read more.
In this study, various wood material sources were used for the manufacture of wood-polymer composites (WPC). The materials were categorised as virgin wood particles (VWP), reprocessed WPC particles (RWP) and recycled thermoset composite particles (RCP) and derived from two virgin wood sources, three-layer particleboards, medium-density fibreboards (MDF) boards, or two different wood/polypropylene composites. All produced wood-polypropylene compounds contained 60% wood material and were manufactured using a co-rotating extruder. Malleated polypropylene was used as a coupling agent. Specimens were injection moulded and subsequently tested for their physico-mechanical properties. To characterize particles before and after processing, dynamic image analysis (DIA) measurement were performed. Additionally, X-ray micro-computed tomography (XµCT) was used to characterize the internal structure of the composites and to verify the obtained particle’s characteristics. It was found that length and aspect ratio of particles were remarkably different before and after processing (loss in length of 15–70% and aspect ratio of 10–40%). Moreover, there were notably differences between the particle sources (RCP retained the highest length and aspect ratio values, followed by VWP and RWP). The results suggest that increased aspect ratios can indeed significantly improve mechanical properties (up to 300% increase in impact bending strength and 75% increase in tensile strength, comparing WPC based either on virgin spruce or MDF material). This phenomenon is suggested to be partially superimposed by improved dispersion of particles, which is expected due to lower variance and increased mechanical properties of RWP composites. However, no notable alterations were observed for composite density. Reprocessed WPC and, particularly, RCP material have proved to be an appealing raw material substitute for the manufacturing of wood–polymer composites. Full article
(This article belongs to the Special Issue Wood Plastic Composites)
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11 pages, 3809 KiB  
Article
Use of Ginger Nanofibers for the Preparation of Cellulose Nanocomposites and Their Antimicrobial Activities
by Joby Jacob, Józef T. Haponiuk, Sabu Thomas, Gregary Peter and Sreeraj Gopi
Fibers 2018, 6(4), 79; https://doi.org/10.3390/fib6040079 - 15 Oct 2018
Cited by 35 | Viewed by 7763
Abstract
Ginger residues left after the extraction of active ingredients from ginger rhizomes are considered to be a bio-waste, available in abundance and very rarely used. Extraction and isolation of natural nanofibers from the agro-waste is economical, environmentally benign, and an alternate strategy to [...] Read more.
Ginger residues left after the extraction of active ingredients from ginger rhizomes are considered to be a bio-waste, available in abundance and very rarely used. Extraction and isolation of natural nanofibers from the agro-waste is economical, environmentally benign, and an alternate strategy to replace synthetic fibers. Here, we report, for the first time, the isolation of ginger nanofibers (GNF) from ginger rhizomes spent by acid hydrolysis and followed by high-pressure homogenization. Scanning electron microscopy was utilized to identify the surface morphology of the GNF and the widths ranged between 130 to 200 nm. Structural analysis of GNF was identified by Fourier transform infrared spectroscopy, Differential scanning calorimetry, and X-ray diffraction methods. This GNF was used to make natural nanocomposites by the solvent-casting method reinforcement, using potato starch (PS) and tapioca starch (TS), and was characterized through various methods. These composites were prepared by the addition of 1, 3, 5, and 7 weight % of GNF with PS or TS. Among these, 5% of the GNF composites of these starches showed very high mechanical properties. The antibacterial test showed that the bionanocomposites with 5% GNF exhibited good antibacterial activity against Bacillus cereus, Escherichia coli, Staphylococcus aureus, and Salmonella typhimurium, due to the addition of GNF in the biopolymer matrices. The viable use of GNF from the unexploited ginger agro-waste would create additional profit and it would help to diminish a large amount of waste generation. Thus, the developed bio-composite could also be employed for development of packing materials and be used in medical applications, such as wound healing pads and medical disposables. Full article
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41 pages, 5543 KiB  
Review
Gas-Liquid Hollow Fiber Membrane Contactors for Different Applications
by Stepan D. Bazhenov, Alexandr V. Bildyukevich and Alexey V. Volkov
Fibers 2018, 6(4), 76; https://doi.org/10.3390/fib6040076 - 10 Oct 2018
Cited by 93 | Viewed by 22970
Abstract
Gas-liquid membrane contactors that were based on hollow fiber membranes are the example of highly effective hybrid separation processes in the field of membrane technology. Membranes provide a fixed and well-determined interface for gas/liquid mass transfer without dispensing one phase into another while [...] Read more.
Gas-liquid membrane contactors that were based on hollow fiber membranes are the example of highly effective hybrid separation processes in the field of membrane technology. Membranes provide a fixed and well-determined interface for gas/liquid mass transfer without dispensing one phase into another while their structure (hollow fiber) offers very large surface area per apparatus volume resulted in the compactness and modularity of separation equipment. In many cases, stated benefits are complemented with high separation selectivity typical for absorption technology. Since hollow fiber membrane contactors are agreed to be one of the most perspective methods for CO2 capture technologies, the major reviews are devoted to research activities within this field. This review is focused on the research works carried out so far on the applications of membrane contactors for other gas-liquid separation tasks, such as water deoxygenation/ozonation, air humidity control, ethylene/ethane separation, etc. A wide range of materials, membranes, and liquid solvents for membrane contactor processes are considered. Special attention is given to current studies on the capture of acid gases (H2S, SO2) from different mixtures. The examples of pilot-scale and semi-industrial implementation of membrane contactors are given. Full article
(This article belongs to the Special Issue Polymer Hollow Fiber Membrane)
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10 pages, 3752 KiB  
Article
Mechanical Behavior of High-Performance Yarns Transversely Loaded by Different Indenters
by Boon Him Lim, Jou-Mei Chu and Wayne Chen
Fibers 2018, 6(4), 69; https://doi.org/10.3390/fib6040069 - 23 Sep 2018
Cited by 10 | Viewed by 4271
Abstract
In this study, we performed off-axis transverse loading experiments to study the stress concentration developed in a high-performance yarn with different indenters. A universal testing machine was utilized to perform quasi-static transverse loading experiments on Twaron® yarns. Seven different round indenters possessing [...] Read more.
In this study, we performed off-axis transverse loading experiments to study the stress concentration developed in a high-performance yarn with different indenters. A universal testing machine was utilized to perform quasi-static transverse loading experiments on Twaron® yarns. Seven different round indenters possessing radius of curvature ranging from 0.20 to 4.50 mm were employed in the experiments. In addition, post-mortem failure analysis was performed on the recovered specimens via a scanning electron microscope. From the transverse loading experiments, the results showed that, as the radius of curvature of the indenters increased, the concentrated load decreased, causing the failure surfaces to change from a combination of kink band, snapped-back, and localized shear to only fibrillations. The concentrated stresses were predicted by a strain energy model when loaded by an indenter with a radius of curvature smaller than 1.59 mm. For indenters larger than 1.59 mm, the specimens failed in fibrillation, the concentrated stresses agreed well with the stresses predicted by quasi-static circular curved beam theory. Full article
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12 pages, 4265 KiB  
Article
Understanding Dispersion of Revolver-Type Anti-Resonant Hollow Core Fibers
by Matthias Zeisberger, Alexander Hartung and Markus A. Schmidt
Fibers 2018, 6(4), 68; https://doi.org/10.3390/fib6040068 - 20 Sep 2018
Cited by 14 | Viewed by 7339
Abstract
Here, we analyze the dispersion behavior of revolver-type anti-resonant hollow core fibers, revealing that the chromatic dispersion of this type of fiber geometry is dominated by the resonances of the glass annuluses, whereas the actual arrangement of the anti-resonant microstructure has a minor [...] Read more.
Here, we analyze the dispersion behavior of revolver-type anti-resonant hollow core fibers, revealing that the chromatic dispersion of this type of fiber geometry is dominated by the resonances of the glass annuluses, whereas the actual arrangement of the anti-resonant microstructure has a minor impact. Based on these findings, we show that the dispersion behavior of the fundamental core mode can be approximated by that of a tube-type fiber, allowing us to derive analytic expressions for phase index, group-velocity dispersion and zero-dispersion wavelength. The resulting equations and simulations reveal that the emergence of zero group velocity dispersion in anti-resonant fibers is fundamentally associated with the adjacent annulus resonance which can be adjusted mainly via the glass thickness of the anti-resonant elements. Due to their generality and the straightforward applicability, our findings will find application in all fields addressing controlling and engineering of pulse dispersion in anti-resonant hollow core fibers. Full article
(This article belongs to the Special Issue Hollow Core Optical Fibers)
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18 pages, 5343 KiB  
Article
Further Progress in Functional Interlayers with Controlled Mechanical Properties Designed for Glass Fiber/Polyester Composites
by Antonin Knob, Jaroslav Lukes, Lawrence Thadeus Drzal and Vladimir Cech
Fibers 2018, 6(3), 58; https://doi.org/10.3390/fib6030058 - 16 Aug 2018
Cited by 16 | Viewed by 5686
Abstract
Compatible interlayers must be coated on reinforcing fibers to ensure effective stress transfer from the polymer matrix to the fiber in high-performance polymer composites. The mechanical properties of the interlayer, and its interfacial adhesion on both interfaces with the fiber and polymer matrix [...] Read more.
Compatible interlayers must be coated on reinforcing fibers to ensure effective stress transfer from the polymer matrix to the fiber in high-performance polymer composites. The mechanical properties of the interlayer, and its interfacial adhesion on both interfaces with the fiber and polymer matrix are among the key parameters that control the performance of polymer composite through the interphase region. Plasma-synthesized interlayers, in the form of variable materials from polymer-like to glass-like films with a Young’s modulus of 10–52 GPa, were deposited on unsized glass fibers used as reinforcements in glass fiber/polyester composites. Modulus Mapping (dynamic nanoindentation testing) was successfully used to examine the mechanical properties across the interphase region on cross-sections of the model composite in order to distinguish the fiber, the interlayer, and the modified and bulk polymer matrix. The interfacial shear strength for plasma-coated fibers in glass fiber/polyester composites, determined from the microindentation test, was up to 36% higher than those of commercially sized fibers. The effects of fiber pretreatment, single and double interlayers, and post-treatment of the interlayer on interfacial shear strength were also discussed. Functional interlayers with high shear yield strength and controlled physicochemical properties are promising for high-performance polymer composites with a controlled interphase. Full article
(This article belongs to the Special Issue Glass Fibers 2018)
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14 pages, 3390 KiB  
Article
Interface Characterization of Epoxy Resin Nanocomposites: A Molecular Dynamics Approach
by Carlos Sáenz Ezquerro, Manuel Laspalas, Agustín Chiminelli, Francisco Serrano and Clara Valero
Fibers 2018, 6(3), 54; https://doi.org/10.3390/fib6030054 - 7 Aug 2018
Cited by 12 | Viewed by 7451
Abstract
In polymer nanocomposites, the interface region between the matrix and the fillers has been identified as a key interaction region that strongly determines the properties of the final material. Determining its structure is crucial from several points of view, from modeling (i.e., properties [...] Read more.
In polymer nanocomposites, the interface region between the matrix and the fillers has been identified as a key interaction region that strongly determines the properties of the final material. Determining its structure is crucial from several points of view, from modeling (i.e., properties prediction) to materials science (i.e., understanding properties/structure relationships). In the presented paper, a method for characterizing the interface region of polymer nanocomposites is described using molecular dynamics (MD) simulations. In particular, the structure of the polymer within the interface region together with its dimension in terms of thickness were analyzed through density profiles. Epoxy resin nanocomposites based on diglycidyl ether of bisphenol A (DGEBA) were studied using this approach, and the interface region with triple walled carbon nanotubes (TWCNT) and carbon fibers (CF) was characterized. The effect of carbon nanotube diameter, type of hardener, and effect of epoxy resin cross-linking degree on interface thickness were analyzed using MD models. From this analysis no general rule on the effect of these parameters on the interface thickness could be established, since in some cases overlapping effects between the analyzed parameters were observed, and each specific case needs to be analyzed independently in detail. Results show that the diameter has an impact on interface thickness, but this effect is affected by the cross-linking degree of the epoxy resin. The type of hardener also has a certain influence on the interface thickness. Full article
(This article belongs to the Special Issue Smart Reinforced Composites Using Carbon and Carbon-Based Nanomaterials)
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18 pages, 9250 KiB  
Article
Investigation of a New Strengthening Technique for RC Deep Beams Using Carbon FRP Ropes as Transverse Reinforcements
by Constantin E. Chalioris, Parthena-Maria K. Kosmidou and Nikos A. Papadopoulos
Fibers 2018, 6(3), 52; https://doi.org/10.3390/fib6030052 - 25 Jul 2018
Cited by 101 | Viewed by 9993
Abstract
The effectiveness of a new retrofitting technique to upgrade the structural behaviour of reinforced concrete (RC) deep beams without steel stirrups using carbon fibre-reinforced polymer (CFRP) ropes as the only transverse shear reinforcement is experimentally investigated. Five shear-critical beams with rectangular and T-shaped [...] Read more.
The effectiveness of a new retrofitting technique to upgrade the structural behaviour of reinforced concrete (RC) deep beams without steel stirrups using carbon fibre-reinforced polymer (CFRP) ropes as the only transverse shear reinforcement is experimentally investigated. Five shear-critical beams with rectangular and T-shaped cross-section are tested under monotonic loading. The strengthening schemes include (a) one vertical and one diagonal single-link CFRP rope that are internally applied through the web of the rectangular beam using an embedded through-section (ETS) system and (b) two vertical U-shaped double-link ropes that are applied around the perimeter of the web of the flanged beam using a near-surface-mounted (NSM) system. In both cases, the free lengths of the CFRP ropes have been properly anchored using epoxy bonded lap splices of the rope as NSM at (a) the top and the bottom of the web of the rectangular beam and (b) the top of the slab of the T-beam. Promising results have been derived, since the proposed strengthening technique enhanced the strength and altered the brittle shear failure to a ductile flexural one. The experimental results of this study were also used to check the validity of an analytical approach to predict the strength of shear strengthened deep beams using FRP ropes as transverse link reinforcement. Full article
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14 pages, 2504 KiB  
Article
Influence of Steel and Macro-Synthetic Fibers on Concrete Properties
by Veronica Guerini, Antonio Conforti, Giovanni Plizzari and Shiho Kawashima
Fibers 2018, 6(3), 47; https://doi.org/10.3390/fib6030047 - 11 Jul 2018
Cited by 101 | Viewed by 9963
Abstract
Fiber addition has become one of the most prevalent methods for enhancing the tensile behavior of concrete. Fibers reduce cracking phenomena and improve the energy absorption capacity of the structure. On the other hand, the introduction of fibers can introduce a negative impact [...] Read more.
Fiber addition has become one of the most prevalent methods for enhancing the tensile behavior of concrete. Fibers reduce cracking phenomena and improve the energy absorption capacity of the structure. On the other hand, the introduction of fibers can introduce a negative impact on concrete workability, whose loss is influenced by different parameters (among which are fiber content and fiber type). In this context, an exploratory study on the influence of steel (high stiffness) and macro-synthetic (low stiffness) fibers on the fresh properties of concrete was carried out, considering workability and air content, as well as resultant mechanical performance. Four fiber types at two volume fractions (0.5% and 1.0%) were studied in two base concretes with different water-to-cement ratios (0.45 and 0.50) by using the slump test, DIN flow table test and air content meter. An additional parameter for the DIN flow table test is proposed herein to quantify the potential preferential flow direction caused by fiber orientation and entanglement. Air meter results showed that the fibers caused only a slight increase in concrete air content; this agreed well with the results of mechanical testing, which showed no apparent effect on measured compressive strength. In addition, it was captured that, for a given fiber volume fraction, steel fibers more adversely affected Fiber Reinforced Concrete (FRC) workability as compared to polypropylene ones, while the opposite result was obtained considering FRC toughness. Full article
(This article belongs to the Special Issue Recent Advancements in Fiber Reinforced Concrete And its Applications)
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53 pages, 11327 KiB  
Review
A Review on Biopolymer-Based Fibers via Electrospinning and Solution Blowing and Their Applications
by Ashish Kakoria and Sumit Sinha-Ray
Fibers 2018, 6(3), 45; https://doi.org/10.3390/fib6030045 - 2 Jul 2018
Cited by 126 | Viewed by 19172
Abstract
Electrospinning, for the last few decades, has been extensively acknowledged for its ability to manufacture a macro/nanofibrous architecture from biopolymers, which is otherwise difficult to obtain, in a cost effective and user-friendly technique. Such biopolymer nanofibers can be tailored to meet applications such [...] Read more.
Electrospinning, for the last few decades, has been extensively acknowledged for its ability to manufacture a macro/nanofibrous architecture from biopolymers, which is otherwise difficult to obtain, in a cost effective and user-friendly technique. Such biopolymer nanofibers can be tailored to meet applications such as drug delivery, tissue engineering, filtration, fuel cell, and food packaging etc. Due to their structural uniqueness, chemical and mechanical stability, functionality, super-high surface area-to-volume ratio, and one-dimensional orientation, electrospun biopolymer nanofibers have been proven to be extremely beneficial. A parallel method in nonwoven methodologies called “Solution Blowing” has also become a potential candidate to fabricate a similar type of architecture from biopolymer fibers, and is gaining popularity among researchers, despite its recent advent in early 2000’s. This review chiefly focuses on the fabrication of biopolymer macro/nanofibers via electrospinning and solution blowing, and several applications of such fiber architectures. Biopolymers include plant- and animal-derived biopolymers, such as cellulose, lignin, chitin, and chitosan, as well as proteins and their derivatives. The fabrication of biopolymer fibers from these biopolymers alone or as blends, predominantly with biodegradable polymers like Polyvinyl alcohol (PVA), Polyethylene Oxide (PEO), Polyethylene glycol (PEG), poly (lactide-co-glycolide) (PLGA) etc., or non-biodegradable polymers like polyamide, Polyacrylonitrile (PAN) etc., will be discussed in detail, along with the applications of several composites of such sort. Full article
(This article belongs to the Special Issue Biopolymer Nanofiber)
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26 pages, 6973 KiB  
Review
Revolver Hollow Core Optical Fibers
by Igor A. Bufetov, Alexey F. Kosolapov, Andrey D. Pryamikov, Alexey V. Gladyshev, Anton N. Kolyadin, Alexander A. Krylov, Yury P. Yatsenko and Alexander S. Biriukov
Fibers 2018, 6(2), 39; https://doi.org/10.3390/fib6020039 - 7 Jun 2018
Cited by 70 | Viewed by 11186
Abstract
Revolver optical fibers (RF) are special type of hollow-core optical fibers with negative curvature of the core-cladding boundary and with cladding that is formed by a one ring layer of capillaries. The physical mechanisms contributing to the waveguiding parameters of RFs are discussed. [...] Read more.
Revolver optical fibers (RF) are special type of hollow-core optical fibers with negative curvature of the core-cladding boundary and with cladding that is formed by a one ring layer of capillaries. The physical mechanisms contributing to the waveguiding parameters of RFs are discussed. The optical properties and possible applications of RFs are reviewed. Special attention is paid to the mid-IR hydrogen Raman lasers that are based on RFs and generating in the wavelength region from 2.9 to 4.4 μm. Full article
(This article belongs to the Special Issue Hollow Core Optical Fibers)
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12 pages, 3247 KiB  
Article
Engineering a Costume for Performance Using Illuminated LED-Yarns
by Dorothy A. Hardy, Andrea Moneta, Viktorija Sakalyte, Lauren Connolly, Arash Shahidi and Theodore Hughes-Riley
Fibers 2018, 6(2), 35; https://doi.org/10.3390/fib6020035 - 1 Jun 2018
Cited by 33 | Viewed by 8211
Abstract
A goal in the field of wearable technology is to blend electronics with textile fibers to create garments that drape and conform as normal, with additional functionality provided by the embedded electronics. This can be achieved with electronic yarns (E-yarns), in which electronics [...] Read more.
A goal in the field of wearable technology is to blend electronics with textile fibers to create garments that drape and conform as normal, with additional functionality provided by the embedded electronics. This can be achieved with electronic yarns (E-yarns), in which electronics are integrated within the fibers of a yarn. A challenge is incorporating non-stretch E-yarns with stretch fabric that is desirable for some applications. To address this challenge, E-yarns containing LEDs were embroidered onto the stretch fabric of a unitard used as part of a carnival costume. A zig-zag pattern of attachment of E-yarns was developed. Tensile testing showed this pattern was successful in preventing breakages within the E-yarns. Use in performance demonstrated that a dancer was unimpeded by the presence of the E-yarns within the unitard, but also a weakness in the junctions between E-yarns was observed, requiring further design work and reinforcement. The level of visibility of the chosen red LEDs within black E-yarns was low. The project demonstrated the feasibility of using E-yarns with stretch fabrics. This will be particularly useful in applications where E-yarns containing sensors are required in close contact with skin to provide meaningful on-body readings, without impeding the wearer. Full article
(This article belongs to the Special Issue Electronically Active Textiles)
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