Fibers

8 pages, 1864 KiB

Open AccessEditor’s ChoiceArticle

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 7956

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

Open AccessEditor’s ChoiceReview

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 59 | Viewed by 13957

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

Open AccessFeature PaperEditor’s ChoiceArticle

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 12 | Viewed by 6659

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

Open AccessEditor’s ChoiceArticle

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 - 04 Jul 2019

Cited by 21 | Viewed by 6654

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

Open AccessEditor’s ChoiceArticle

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 5711

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

Open AccessEditor’s ChoiceReview

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 - 01 Jun 2019

Cited by 64 | Viewed by 20624

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

Open AccessEditor’s ChoiceArticle

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 13 | Viewed by 7089

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

Open AccessEditor’s ChoiceReview

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 - 06 May 2019

Cited by 47 | Viewed by 10617

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

Open AccessEditor’s ChoiceArticle

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 - 01 May 2019

Cited by 10 | Viewed by 8417

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

Open AccessEditor’s ChoiceArticle

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 5 | Viewed by 5414

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

Open AccessEditor’s ChoiceArticle

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 13 | Viewed by 4936

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

Open AccessEditor’s ChoiceArticle

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 23 | Viewed by 6957

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

Open AccessEditor’s ChoiceReview

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 16 | Viewed by 4826

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

Open AccessFeature PaperEditor’s ChoiceArticle

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 16 | Viewed by 5953

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

Open AccessEditor’s ChoiceReview

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 60 | Viewed by 15006

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

Open AccessEditor’s ChoiceArticle

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 8 | Viewed by 5689

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

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 129 | Viewed by 16635

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

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 - 01 Feb 2019

Cited by 62 | Viewed by 9676

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 20 | Viewed by 8648

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 44 | Viewed by 8143

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 - 04 Jan 2019

Cited by 13 | Viewed by 6583

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 - 07 Nov 2018

Cited by 20 | Viewed by 6742

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 28 | Viewed by 7151

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 85 | Viewed by 21106

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 4018

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 14 | Viewed by 6789

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 5334

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 - 07 Aug 2018

Cited by 12 | Viewed by 6917

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 93 | Viewed by 9245

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 90 | Viewed by 8540

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 - 02 Jul 2018

Cited by 116 | Viewed by 17801

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 - 07 Jun 2018

Cited by 67 | Viewed by 10371

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 - 01 Jun 2018

Cited by 25 | Viewed by 7627

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 - 03 May 2018

Cited by 142 | Viewed by 14492

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 6221

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 - 02 Apr 2018

Cited by 21 | Viewed by 11806

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 - 05 Mar 2018

Cited by 31 | Viewed by 11608

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 - 01 Mar 2018

Cited by 62 | Viewed by 6111

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 63 | Viewed by 9507

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 43 | Viewed by 7590

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 - 01 Jan 2018

Cited by 34 | Viewed by 9073

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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