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Fibers, Volume 11, Issue 11 (November 2023) – 10 articles

Cover Story (view full-size image): Ytterbium-doped silica fibres form the foundation of modern high-power lasers and amplifiers. Achieving high concentrations of ytterbium (Yb) ions is crucial, yet hindered by performance issues related to clustering and quenching effects. In this study, powder-in-tube technology is employed to realize a large-core silica fibre with exceptionally high levels of aluminium (Al) co-doping, aimed at increasing Yb-ion solubility in the glass matrix. Concentrations of 60 at.% Al and 1 at.% Yb are demonstrated, limited only by diffusion effects during fibre drawing. The fibre exhibits a fluorescence lifetime of 1.2 ms, indicating effective suppression of clustering and quenching effects. These findings are anticipated to provide valuable insights into advancing power scaling in fibre amplifier technology. View this paper
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19 pages, 3132 KiB  
Article
Shear Strengthening of Reinforced Concrete Beams Using Engineered Cementitious Composites and Carbon Fiber-Reinforced Polymer Sheets
Fibers 2023, 11(11), 98; https://doi.org/10.3390/fib11110098 - 14 Nov 2023
Viewed by 1323
Abstract
This study evaluates the performance of Reinforced Concrete (RC) beams enhanced in shear using Engineered Cementitious Composites (ECCs) and Carbon Fiber-Reinforced Polymers (CFRPs). The experimental study encompasses fifteen RC beams. This set includes one control specimen and fourteen beams fortified in shear with [...] Read more.
This study evaluates the performance of Reinforced Concrete (RC) beams enhanced in shear using Engineered Cementitious Composites (ECCs) and Carbon Fiber-Reinforced Polymers (CFRPs). The experimental study encompasses fifteen RC beams. This set includes one control specimen and fourteen beams fortified in shear with Externally Bonded (EB) composites. Two of these specimens were enhanced with ECC layers, while the remaining were augmented with combined CFRP-ECC layers. Variables in the test included the ECC layer thickness, matrix type, number of CFRP layers, and strengthening configurations such as full wrapping, vertical strips, and inclined strips. The results indicated that the shear capacity of the fortified beams increased by 61.1% to 160.1% compared to the control specimen. The most effective structural performance was observed in the full wrapping method, which utilized a single CFRP layer combined with either 20 mm or 40 mm ECC thickness, outperforming other techniques. However, the inclined strip method demonstrated a notably higher load-bearing capacity than the full wrapping approach for beams with double CFRP layers paired with 20 mm and 40 mm ECC thicknesses. This configuration also exhibited superior ductility compared to the rest. Furthermore, the experimental shear capacities obtained were juxtaposed with theoretical values from prevailing design standards. Full article
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12 pages, 3276 KiB  
Article
Field Study of Activity of Antimicrobial Polypropylene Textiles
Fibers 2023, 11(11), 97; https://doi.org/10.3390/fib11110097 - 10 Nov 2023
Viewed by 1222
Abstract
In this work, an in situ study is presented of the impact of textile materials used in healthcare facilities on microbial colonization of textile surfaces. The available literature describes antimicrobial active textiles and their effectiveness in laboratory conditions. However, the quantification of the [...] Read more.
In this work, an in situ study is presented of the impact of textile materials used in healthcare facilities on microbial colonization of textile surfaces. The available literature describes antimicrobial active textiles and their effectiveness in laboratory conditions. However, the quantification of the impact on the microbiome of healthcare facilities has not been investigated so far. Polypropylene yarns doped with silver phosphate glass and zinc pyrithione were prepared and used for the production of bed sheets and clothing for healthcare personnel. Subsequently, measurements of airborne particles and viable microorganisms on given textiles were conducted in a private surgery clinic for 3 weeks, comparing the counts of viable microorganisms before and after replacing staff clothing and bedding on examination and the surgical bed with said polypropylene cloth. A significant reduction in airborne particles and viable microorganisms was expected based on previous studies on the use of polypropylene textiles in operating rooms. In this study, a significant reduction in viable airborne fungi and viable microorganisms on monitored textiles was observed by multiple methods. However, the effect on airborne microorganisms seems insignificant in areas with frequent patient traffic. The textile described here represents a new additional way of protecting patients and medical personnel from healthcare-associated infections while using a modification of proven production procedures and commercially usable materials without legislative restrictions. Full article
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21 pages, 44123 KiB  
Article
Novel Fiber-Based Padding Materials for Football Helmets
Fibers 2023, 11(11), 96; https://doi.org/10.3390/fib11110096 - 08 Nov 2023
Viewed by 1159
Abstract
An experimental study is performed to determine the head mechanics of American football helmets equipped with novel fiber energy absorbing material (FEAM). FEAM-based padding materials have substrates of textile fabrics and foam made with nylon fibers using electro-static flocking process. Both linear and [...] Read more.
An experimental study is performed to determine the head mechanics of American football helmets equipped with novel fiber energy absorbing material (FEAM). FEAM-based padding materials have substrates of textile fabrics and foam made with nylon fibers using electro-static flocking process. Both linear and angular accelerations of the sport helmets are determined under impact loads using a custom-built linear impactor and instrumented head. The effectiveness of padding materials and vinyl nitrile (VN) foam for impact loads on six different head positions that simulate two helmeted sport athletes in real-time helmet-to-helmet strike/impact is investigated. A high-speed camera is used to record and track neck flexion angles and compare them with pad effectiveness to better understand the head kinematics of struck players at three different impact speeds (6 m/s, 8 m/s, and 10 m/s). At impact speed of 6 m/s and 8 m/s, the FEAM-based padding material of 60 denier fibers showed superior resistance for angular acceleration. Although novel pads of VN foam flocked with 60 denier fibers outperformed with lowest linear acceleration for most of the head positions at low impact speed of 6 m/s, VN foam with no fibers demonstrated excellent performance for linear acceleration at other two speeds. Full article
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10 pages, 3383 KiB  
Article
Multimode Ytterbium–Aluminosilicate Core Optical Fibre for Amplification and Laser Applications
Fibers 2023, 11(11), 95; https://doi.org/10.3390/fib11110095 - 08 Nov 2023
Viewed by 1155
Abstract
Rare-earth-doped optical fibres are widely used in lasers and amplifiers. The incorporation of ytterbium and aluminium oxide in a high doping concentration has led to the fabrication of a multi-mode (MM) optical fibre. Within this research, the design, preparation and calculation for the [...] Read more.
Rare-earth-doped optical fibres are widely used in lasers and amplifiers. The incorporation of ytterbium and aluminium oxide in a high doping concentration has led to the fabrication of a multi-mode (MM) optical fibre. Within this research, the design, preparation and calculation for the production of a fibre with a targeted 45 μm core diameter are explored. By Energy Dispersive X-ray (EDX) analysis, the doping concentrations of the elements in the core have been measured as 60.4 at.% Al and 1 at.% Yb. Supporting micrographs are used for confirming the core/cladding ratio. Based on the atomic percentage concentration, the calculated refractive index of the multi-element core has an n = 1.61 and an NA = 0.678. Characterisation of the fibre, including absorption and emission cross-section analysis, was performed in order to prove the ability of the fibre to be used for amplification as well as lasing applications. Full article
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17 pages, 8361 KiB  
Article
Performance of Fiber-Reinforced Ultra-High-Performance Concrete Incorporated with Microencapsulated Phase Change Materials
Fibers 2023, 11(11), 94; https://doi.org/10.3390/fib11110094 - 03 Nov 2023
Viewed by 1370
Abstract
In the era of environmental concerns, many attempts were proposed to optimize energy efficiency for buildings and consequently reduce their carbon footprint. As a sustainable approach, it is a promising solution to incorporate phase change materials (PCMs) in construction materials (i.e., ultra-high-performance concrete [...] Read more.
In the era of environmental concerns, many attempts were proposed to optimize energy efficiency for buildings and consequently reduce their carbon footprint. As a sustainable approach, it is a promising solution to incorporate phase change materials (PCMs) in construction materials (i.e., ultra-high-performance concrete (UHPC)) to increase its thermal storage capacity and reduce the operation energy. However, incorporating microencapsulated phase change materials (MPCMs) into cementitious materials negatively impacts the fresh and hardened properties. UHPC’s improved mechanical strength allows for the creation of slimmer and lighter structures, which may result in less demand in concrete manufacturing and fewer emissions. Hence, the properties of UHPC incorporated with MPCMs (MPCM-UHPC) need more investigations. To fill the gap in the literature about the lack of information about MPCM-UHPC performance, this paper provides a comprehensive work to study the mechanical, thermal, and impact resistance properties of (MPCM-UHPC). Proportions of 5% and 10% of MPCMs were incorporated as a replacement of sand by volume. Proportions of 0.5%, 1.0%, and 1.5% of micro steel fiber reinforcement were used as a percentage of the mixture’s total volume. The results revealed the importance of fiber reinforcement in compensating for the negative effect of MPCMs inclusion for improving the thermal properties. Increasing the amount of MPCMs enhanced the thermal performance of the produced UHPC panels through the ability to absorb and release the energy during the phase change process. Full article
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25 pages, 3449 KiB  
Review
Characterization Specifications for FRP Pultruded Materials: From Constituents to Pultruded Profiles
Fibers 2023, 11(11), 93; https://doi.org/10.3390/fib11110093 - 02 Nov 2023
Cited by 1 | Viewed by 1456
Abstract
Pultruded FRP composites have emerged as a promising alternative to traditional materials like concrete, steel, and timber, especially in corrosive environmental conditions. However, the unique properties of these composites necessitate careful consideration during their implementation, as they differ significantly from conventional materials. Proper [...] Read more.
Pultruded FRP composites have emerged as a promising alternative to traditional materials like concrete, steel, and timber, especially in corrosive environmental conditions. However, the unique properties of these composites necessitate careful consideration during their implementation, as they differ significantly from conventional materials. Proper testing and characterization of FRP pultruded materials is key for their efficient and safe implementation. However, the existing specifications are not unified, resulting in ambiguity among stakeholders. This paper aims to bridge this gap by thoroughly reviewing current destructive and non-destructive test methods for FRP pultruded materials, specifications, quality control, and health monitoring of FRP structures. Each subsection is further divided into subtopics, providing a comprehensive overview of the subject. By shedding light on these crucial aspects, this article aims to accelerate the adoption and utilization of these innovative materials in practical applications. Full article
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15 pages, 2957 KiB  
Article
Effect of Alkali Treatment under Ambient and Heated Conditions on the Physicochemical, Structural, Morphological, and Thermal Properties of Calamus tenuis Cane Fibers
Fibers 2023, 11(11), 92; https://doi.org/10.3390/fib11110092 - 02 Nov 2023
Viewed by 1353
Abstract
This study explores the effect of alkali treatment at ambient (25 °C) and elevated temperatures (100 °C) on the physicochemical, structural, morphological, and thermal properties of Calamus tenuis cane fibers (CTCFs) for the first time. Our purpose is to investigate their potential use [...] Read more.
This study explores the effect of alkali treatment at ambient (25 °C) and elevated temperatures (100 °C) on the physicochemical, structural, morphological, and thermal properties of Calamus tenuis cane fibers (CTCFs) for the first time. Our purpose is to investigate their potential use as reinforcement in polymer composites, since cane fibers are generally known for their accurate and consistent geometrical orientation. Treatment with 8% (w/v) sodium hydroxide (NaOH) is carried out at ambient temperature and at 100 °C for 4 h. Chemical analysis and Fourier transform IR spectroscopy (FTIR) indicate some removal of non-cellulosic elements from CTCFs during alkali treatment, resulting in increased surface roughness, as confirmed by using SEM micrographs. This removal of non-cellulosic elements leads to an enhancement in the density of the treated CTCFs. Untreated and treated fibers are analyzed for maximum degradation temperature, thermal stability, and kinetic activation energy (Ea) using thermogravimetric analysis (TGA). In particular, Ea was considerably diminished with treatment and temperature. X-ray diffraction (XRD) results show an improved crystallinity index (37.38% to 44.02%) and crystallite size (2.73 nm to 2.98 nm) for fibers treated with 8% NaOH at ambient temperature. In conclusion, a general benefit was achieved by treating CTCFs, though the influence of increasing temperature treatment appears controversial. Full article
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21 pages, 5717 KiB  
Article
A Comparison of Chitosan Adhesion to KOH and H2O2 Pre-Treated Electrospun Poly(3-Hydroxybutyrate) Nanofibers
Fibers 2023, 11(11), 91; https://doi.org/10.3390/fib11110091 - 26 Oct 2023
Viewed by 1050
Abstract
Chitosan coatings could effectively increase the biostability and biocompatibility of biomaterials while maintaining their structural integrity. In this study, electrospun fibrous polyhydroxybutyrate (PHB) membranes were pre-treated with potassium hydroxide (KOH) or hydrogen peroxide (H2O2) and then modified with dopamine [...] Read more.
Chitosan coatings could effectively increase the biostability and biocompatibility of biomaterials while maintaining their structural integrity. In this study, electrospun fibrous polyhydroxybutyrate (PHB) membranes were pre-treated with potassium hydroxide (KOH) or hydrogen peroxide (H2O2) and then modified with dopamine (DA) and glutaraldehyde (GA) to improve their adhesion with chitosan (CS). Scanning electron microscopy (SEM), water contact angles (WCA), and Fourier transform infrared spectroscopy (FTIR) were used to demonstrate the successful generation of DA and GA-modified PHB fibers. KOH pre-treated PHB membranes exhibited superior binding efficiency with CS at low concentrations compared to their H2O2 pre-treated counterparts. The thermal analysis demonstrated a considerable decrease in the degradation temperature and crystallinity of KOH pre-treated membranes, with temperatures dropping from 309 °C to 265.5 °C and crystallinity reducing from 100% to 25.59% as CS concentration increased from 0 to 2 w/v%. In comparison, H2O2 pre-treated membranes experienced a mild reduction in degradation temperature, from 309 °C to 284.4 °C, and a large decrease in crystallinity from 100% to 43%. UV-vis analysis using Cibacron Brilliant Red 3B-A dye (CBR) indicated similar binding efficiencies at low CS concentrations for both pre-treatments, but decreased stability at higher concentrations for KOH pre-treated membranes. Mechanical testing revealed a considerable increase in Young’s modulus (2 to 14%), toughness (31 to 60%), and ultimate tensile stress (UTS) (14 to 63%) for KOH-treated membranes compared with H2O2 pre-treated membranes as CS concentration increased from 0 to 2 w/v%. Full article
(This article belongs to the Special Issue Nanofibrous Yarns and Nanotextiles for Biomedical Application)
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14 pages, 7979 KiB  
Article
Next-Generation Cellulosic Filaments from Hemp Pulp via Dry-Jet Wet Spinning Using HighPerCell® Technology
Fibers 2023, 11(11), 90; https://doi.org/10.3390/fib11110090 - 26 Oct 2023
Viewed by 1458
Abstract
Fiber demand of cellulosic fibers is rapidly increasing; however, these fibers are mainly based on the use of wood pulp (WP), which often have long transport times and, consequently, a high CO2 footprint. So, alternative pulps based on non-wood, annual fast-growing plants [...] Read more.
Fiber demand of cellulosic fibers is rapidly increasing; however, these fibers are mainly based on the use of wood pulp (WP), which often have long transport times and, consequently, a high CO2 footprint. So, alternative pulps based on non-wood, annual fast-growing plants are an option to cover the demand for raw materials and resources. Herein, we report on the use of a novel developed hemp pulp (HP) for man-made cellulosic fiber filament spinning. Commercial WP was used as a reference material. While HP could be used and directly spun as received without any further pretreatment, an additional step to adjust the degree of polymerization (DP) was needed to use the wood pulp. Continuous filaments were spun using a novel dry-jet wet spinning (HighPerCell® process) technique, which is based on the use of 1-ethyl-3-methylimidazolium octanoate ([C2C1im][Oc]) as a solvent. Via this approach, several thousand meters (12,000 m–15,000 m) of continuous multifilament filaments were spun. The HP pulps showed excellent spinning performance. The novel approach allows the preparation of cellulosic fibers for either technical—with high tensile strength—or textile—possessing a low fibrillation tendency—applications. Textile hemp-based filaments were used for first weaving trials, resulting in a flawless fabric. Full article
(This article belongs to the Special Issue Fibers 10th Anniversary: Past, Present, and Future)
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16 pages, 6134 KiB  
Article
Optimization and Dispersion Tailoring of Chalcogenide M-Type Fibers Using a Modified Genetic Algorithm
Fibers 2023, 11(11), 89; https://doi.org/10.3390/fib11110089 - 24 Oct 2023
Viewed by 1006
Abstract
M-type optical fibers in which a core is surrounded by a thin ring layer with a higher refractive index have attracted increasing attention in recent years. One of their advantageous features is the ability to operate a non-fundamental LP02 mode possessing unusual [...] Read more.
M-type optical fibers in which a core is surrounded by a thin ring layer with a higher refractive index have attracted increasing attention in recent years. One of their advantageous features is the ability to operate a non-fundamental LP02 mode possessing unusual dispersion properties, namely, a zero-dispersion wavelength (ZDW) shifted to the short wavelength region relative to the material ZDW. The LP02 mode can be selectively excited since it is predominantly localized near the core, while the fundamental LP01 and other higher modes are localized near the ring (for proper fiber parameters). In this paper, we present a comprehensive theoretical analysis of effective dispersion tailoring for the HE12 mode of highly nonlinear chalcogenide glass fibers (for which the LP mode approximation fails due to large refractive index contrasts). We demonstrate fiber designs for which ZDWs can be shifted to the spectral region < 2 μm, which is of great interest for the development of mid-IR supercontinuum sources and frequency-tunable pulse sources with standard near-IR pumping. We obtained the characteristic equation and solved it numerically to find mode fields and dispersion characteristics. We show the possibility of achieving dispersion characteristics of the HE12 mode with one, two, three, and four ZDWs in the wavelength range of 1.5–5.5 μm. We used a modified genetic algorithm (MGA) to design fibers with desired dispersion parameters. In particular, by applying an MGA, we optimized four fiber parameters and constructed a fiber for which HE12 mode dispersion is anomalous in the 1.735–5.155 μm range. Full article
(This article belongs to the Special Issue Multimode Nonlinear Optical Fibers)
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