Fibers

58 pages, 15866 KiB

Open AccessFeature PaperEditor’s ChoiceReview

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 164 | Viewed by 21421

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

Open AccessEditor’s ChoiceArticle

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 87 | Viewed by 11233

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

Open AccessEditor’s ChoiceArticle

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 25 | Viewed by 9831

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

Open AccessEditor’s ChoiceArticle

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 51 | Viewed by 9396

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

Open AccessEditor’s ChoiceArticle

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 15 | Viewed by 7446

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

Open AccessEditor’s ChoiceArticle

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 22 | Viewed by 7842

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

Open AccessEditor’s ChoiceArticle

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 8194

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

Open AccessEditor’s ChoiceReview

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 105 | Viewed by 24420

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

Open AccessEditor’s ChoiceArticle

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 4471

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

Open AccessEditor’s ChoiceArticle

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 16 | Viewed by 7859

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

Open AccessEditor’s ChoiceArticle

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 5868

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

Open AccessEditor’s ChoiceArticle

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 16 | Viewed by 7839

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

Open AccessEditor’s ChoiceArticle

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 104 | Viewed by 10475

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

Open AccessEditor’s ChoiceArticle

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 107 | Viewed by 10695

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

Open AccessEditor’s ChoiceReview

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 142 | Viewed by 20423

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

Open AccessEditor’s ChoiceReview

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 71 | Viewed by 11829

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

Open AccessEditor’s ChoiceArticle

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 35 | Viewed by 8649

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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12 pages, 3178 KiB

Open AccessEditor’s ChoiceArticle

Production of Nanocellulose from Pineapple Leaf Fibers via High-Shear Homogenization and Ultrasonication

by Melbi Mahardika, Hairul Abral, Anwar Kasim, Syukri Arief and Mochamad Asrofi

Fibers 2018, 6(2), 28; https://doi.org/10.3390/fib6020028 - 3 May 2018

Cited by 174 | Viewed by 17760

Abstract

In this study, the isolation and characterization of nanocellulose from pineapple leaf fibers (PLF) were carried out. Chemical pretreatment included pulping, bleaching, and acid hydrolysis to remove lignin, hemicellulose, and extractive substances were conducted. This was followed by high-shear homogenization and ultrasonication to [...] Read more.

In this study, the isolation and characterization of nanocellulose from pineapple leaf fibers (PLF) were carried out. Chemical pretreatment included pulping, bleaching, and acid hydrolysis to remove lignin, hemicellulose, and extractive substances were conducted. This was followed by high-shear homogenization and ultrasonication to produce nanocellulose. Morphological changes to the PLF due to treatment were investigated using scanning electron microscopy (SEM). This showed that the PLF had a diameter of 1–10 µm after high-shear homogenizing. Transmission electron microscopy (TEM) indicated that the nanofibers after ultrasonication for 60 min showed 40–70 nm diameters. Particle size analysis (PSA) indicates that the fibers had an average diameter of 68 nm. Crystallinity index was determined by X-ray diffraction (XRD) and had the highest value after acid hydrolysis at 83% but after 60 min ultrasonication, this decreased to 62%. Meanwhile, Fourier transform infrared (FTIR) spectroscopy showed there was no chemical structure change after acid hydrolysis. The most significant finding from thermal gravimetric analysis (TGA) is that the higher degradation temperature of nanofibers indicates superior thermal stability over untreated fiber. These results indicate that PLF waste could become a viable source of commercially valuable nanocellulose. Full article

(This article belongs to the Special Issue Biopolymer Nanofiber)

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8 pages, 3287 KiB

Open AccessEditor’s ChoiceArticle

Fabrication of Shatter-Proof Metal Hollow-Core Optical Fibers for Endoscopic Mid-Infrared Laser Applications

by Katsumasa Iwai, Hiroyuki Takaku, Mitsunobu Miyagi, Yi-Wei Shi and Yuji Matsuura

Fibers 2018, 6(2), 24; https://doi.org/10.3390/fib6020024 - 18 Apr 2018

Cited by 11 | Viewed by 6963

Abstract

A method for fabricating robust and thin hollow-core optical fibers that carry mid-infrared light is proposed for use in endoscopic laser applications. The fiber is made of stainless steel tubing, eliminating the risk of scattering small glass fragments inside the body if the [...] Read more.

A method for fabricating robust and thin hollow-core optical fibers that carry mid-infrared light is proposed for use in endoscopic laser applications. The fiber is made of stainless steel tubing, eliminating the risk of scattering small glass fragments inside the body if the fiber breaks. To reduce the inner surface roughness of the tubing, a polymer base layer is formed prior to depositing silver and optical-polymer layers that confine light inside the hollow core. The surface roughness is greatly decreased by re-coating thin polymer base layers. Because of this smooth base layer surface, a uniform optical-polymer film can be formed around the core. As a result, clear interference peaks are observed in both the visible and mid-infrared regions. Transmission losses were also low for the carbon dioxide laser used for medical treatments as well as the visible laser diode used for an aiming beam. Measurements of bending losses for these lasers demonstrate the feasibility of the designed fiber for endoscopic applications. Full article

(This article belongs to the Special Issue Hollow Core Optical Fibers)

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11 pages, 18662 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Key Stages of Fiber Development as Determinants of Bast Fiber Yield and Quality

by Natalia Mokshina, Tatyana Chernova, Dmitry Galinousky, Oleg Gorshkov and Tatyana Gorshkova

Fibers 2018, 6(2), 20; https://doi.org/10.3390/fib6020020 - 2 Apr 2018

Cited by 28 | Viewed by 13215

Abstract

Plant fibers find wide application in various fields that demand specific parameters of fiber quality. To develop approaches for the improvement of yield and quality of bast fibers, the knowledge of the fiber developmental stages and of the key molecular players that are [...] Read more.

Plant fibers find wide application in various fields that demand specific parameters of fiber quality. To develop approaches for the improvement of yield and quality of bast fibers, the knowledge of the fiber developmental stages and of the key molecular players that are responsible for a certain parameter, are vitally important. In the present review the key stages of fiber development, such as initiation, intrusive growth, and formation of thickened cell wall layers (secondary and tertiary cell walls) are considered, as well as the impact of each of these stages on the final parameters of fiber yield and quality. The problems and perspectives of crop quality regulation are discussed. Full article

(This article belongs to the Special Issue Plant Bast Fibers)

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19 pages, 11998 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Synthetic Strategies for the Fabrication of Cationic Surface-Modified Cellulose Nanocrystals

by Rajesh Sunasee and Usha D. Hemraz

Fibers 2018, 6(1), 15; https://doi.org/10.3390/fib6010015 - 5 Mar 2018

Cited by 40 | Viewed by 13169

Abstract

Cellulose nanocrystals (CNCs) are renewable nanosized materials with exceptional physicochemical properties that continue to garner a high level of attention in both industry and academia for their potential high-end material applications. These rod-shaped CNCs are appealing due to their non-toxic, carbohydrate-based chemical structure, [...] Read more.

Cellulose nanocrystals (CNCs) are renewable nanosized materials with exceptional physicochemical properties that continue to garner a high level of attention in both industry and academia for their potential high-end material applications. These rod-shaped CNCs are appealing due to their non-toxic, carbohydrate-based chemical structure, large surface area, and the presence of ample surface hydroxyl groups for chemical surface modifications. CNCs, generally prepared from sulfuric acid-mediated hydrolysis of native cellulose, display an anionic surface that has been exploited for a number of applications. However, several recent studies showed the importance of CNCs’ surface charge reversal towards the design of functional cationic CNCs. Cationization of CNCs could further open up other innovative applications, in particular, bioapplications such as gene and drug delivery, vaccine adjuvants, and tissue engineering. This mini-review focuses mainly on the recent covalent synthetic methods for the design and fabrication of cationic CNCs as well as their potential bioapplications. Full article

(This article belongs to the Special Issue Current Developments in Cellulose Based Nanomaterials)

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13 pages, 7356 KiB

Open AccessEditor’s ChoiceReview

Advances on Polymer Optical Fiber Gratings Using a KrF Pulsed Laser System Operating at 248 nm

by Carlos A. F. Marques, Arnaldo G. Leal-Junior, Rui Min, Maria Domingues, Cátia Leitão, Paulo Antunes, Beatriz Ortega and Paulo André

Fibers 2018, 6(1), 13; https://doi.org/10.3390/fib6010013 - 1 Mar 2018

Cited by 72 | Viewed by 6777

Abstract

This paper presents the achievements and progress made on the polymer optical fiber (POF) gratings inscription in different types of Fiber Bragg Gratings (FBGs) and long period gratings (LPGs). Since the first demonstration of POFBGs in 1999, significant progress has been made where [...] Read more.

This paper presents the achievements and progress made on the polymer optical fiber (POF) gratings inscription in different types of Fiber Bragg Gratings (FBGs) and long period gratings (LPGs). Since the first demonstration of POFBGs in 1999, significant progress has been made where the inscription times that were higher than 1 h have been reduced to 15 ns with the application of the krypton fluoride (KrF) pulsed laser operating at 248 nm and thermal treatments such as the pre-annealing of fibers. In addition, the application of dopants such as benzyl dimethyl ketal (BDK) has provided a significant decrease of the fiber inscription time. Furthermore, such improvements lead to the possibility of inscribing POF gratings in 850 nm and 600 nm, instead of only the 1550 nm region. The progress on the inscription of different types of polymer optical fiber Bragg gratings (POFBGs) such as chirped POFBGs and phase-shifted POFBGs are also reported in this review. Full article

(This article belongs to the Special Issue Optical Fiber Communications)

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13 pages, 7458 KiB

Open AccessEditor’s ChoiceArticle

Restrained Shrinkage Cracking of Fiber-Reinforced High-Strength Concrete

by Ashkan Saradar, Behzad Tahmouresi, Ehsan Mohseni and Ali Shadmani

Fibers 2018, 6(1), 12; https://doi.org/10.3390/fib6010012 - 19 Feb 2018

Cited by 77 | Viewed by 11050

Abstract

Concrete shrinkage and volume reduction happens due to the loss of moisture, which eventually results in cracks and more concrete deformation. In this study, the effect of polypropylene (PP), steel, glass, basalt, and polyolefin fibers on compressive and flexural strength, drying shrinkage, and [...] Read more.

Concrete shrinkage and volume reduction happens due to the loss of moisture, which eventually results in cracks and more concrete deformation. In this study, the effect of polypropylene (PP), steel, glass, basalt, and polyolefin fibers on compressive and flexural strength, drying shrinkage, and cracking potential, using the ring test at early ages of high-strength concrete mixtures, was investigated. The restrained shrinkage test was performed on concrete ring specimens according to the ASTM C1581 standard. The crack width and age of restrained shrinkage cracking were the main parameters studied in this research. The results indicated that the addition of fiber increases the compressive strength by 16%, 20%, and 3% at the age of 3, 7, and 28 days, respectively, and increases the flexural toughness index up to 7.7 times. Steel and glass fibers had a better performance in flexural strength, but relatively poor action in the velocity reduction and cracking time of the restrained shrinkage. Additionally, cracks in all concrete ring specimens except for the polypropylene-containing mixture, was developed to a full depth crack. The mixture with polypropylene fiber indicated a reduction in crack width up to 62% and an increasing age cracking up to 84%. Full article

(This article belongs to the Special Issue Recent Advancements in Fiber Reinforced Concrete And its Applications)

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9 pages, 2113 KiB

Open AccessFeature PaperEditor’s ChoiceCommunication

Investigation of the Mechanical Properties of Flax Cell Walls during Plant Development: The Relation between Performance and Cell Wall Structure

by Camille Goudenhooft, David Siniscalco, Olivier Arnould, Alain Bourmaud, Olivier Sire, Tatyana Gorshkova and Christophe Baley

Fibers 2018, 6(1), 6; https://doi.org/10.3390/fib6010006 - 17 Jan 2018

Cited by 52 | Viewed by 8509

Abstract

The development of flax (Linum usitatissimum L.) fibers was studied to obtain better insight on the progression of their high mechanical performances during plant growth. Fibers at two steps of plant development were studied, namely the end of the fast growth period [...] Read more.

The development of flax (Linum usitatissimum L.) fibers was studied to obtain better insight on the progression of their high mechanical performances during plant growth. Fibers at two steps of plant development were studied, namely the end of the fast growth period and at plant maturity, each time at three plant heights. The indentation modulus of the fiber cell wall was characterized by atomic force microscopy (AFM) using peak-force quantitative nano-mechanical property mapping (PF-QNM). Changes in the cell wall modulus with the cell wall thickening were highlighted. For growing plants, fibers from top and middle heights show a loose inner Gn layer with a lower indentation modulus than mature fibers, which exhibit thickened homogeneous cell walls made only of a G layer. The influence of these changes in the fiber cell wall on the mechanical performances of extracted elementary fibers was also emphasized by tensile tests. In addition, Raman spectra were recorded on samples from both growing and mature plants. The results suggest that, for the fiber cell wall, the cellulose contribution increases with fiber maturity, leading to a greater cell wall modulus of flax fibers. Full article

(This article belongs to the Special Issue Plant Bast Fibers)

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10 pages, 2949 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effect of Filler Orientation on the Electrical Conductivity of Carbon Fiber/PMMA Composites

by Muchao Qu, Fritjof Nilsson and Dirk W. Schubert

Fibers 2018, 6(1), 3; https://doi.org/10.3390/fib6010003 - 1 Jan 2018

Cited by 41 | Viewed by 10071

Abstract

The electrical conductivity of extruded carbon fiber (CF)/Polymethylmethacrylate (PMMA) composites with controlled CF aspect ratio and filler fractions ranging from 0 to 50 vol. % has been investigated and analyzed. The composites were extruded through a capillary rheometer, utilizing either 1-mm or 3-mm [...] Read more.

The electrical conductivity of extruded carbon fiber (CF)/Polymethylmethacrylate (PMMA) composites with controlled CF aspect ratio and filler fractions ranging from 0 to 50 vol. % has been investigated and analyzed. The composites were extruded through a capillary rheometer, utilizing either 1-mm or 3-mm diameter extrusion dies, resulting in cylindrical composite filaments of two different diameters. Since the average CF orientation becomes more aligned with the extrusion flow when the diameter of the extrusion dies decreases, the relationship between conductivity and average fiber orientation could therefore be examined. The room temperature conductivities of the extruded filaments as a function of CF fractions were fitted to the McLachlan general effective medium (GEM) equation and the percolation thresholds were determined to 20.0 ± 2.5 vol. % and 32.0 ± 5.9 vol. % for the 3-mm (with CFs oriented less) and 1-mm (with CFs oriented more) filaments, respectively. It turned out that the oriented CFs in the composite shift the percolation threshold to a higher value, however, the conductivity above the percolation threshold is higher for composites with oriented CFs. A novel approach based on the Balberg excluded volume theory was proposed to explain this counterintuitive phenomenon. Full article

(This article belongs to the Special Issue Carbon Fiber Reinforced Composites)

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