Fibers

13 pages, 294 KiB

Open AccessReview

The Current State and Prospects of Recycling Silk Industry Waste into Nonwoven Materials

by Elena S. Sashina and Olga I. Yakovleva

Fibers 2023, 11(6), 56; https://doi.org/10.3390/fib11060056 - 19 Jun 2023

Cited by 3 | Viewed by 2319

Natural fibres are the preferred options for garment, technical and medical textiles, nonwovens and composites. Their sustainability is a considerable advantage, though the nature of silk production and processing involves a large amount of waste. The present review explores the current issues of [...] Read more.

Natural fibres are the preferred options for garment, technical and medical textiles, nonwovens and composites. Their sustainability is a considerable advantage, though the nature of silk production and processing involves a large amount of waste. The present review explores the current issues of recycling silk waste into nonwovens for various purposes. The article proposes obtaining nonwovens from short fibres using electrospinning of fibroin solutions in volatile solvents. Longer fibres are proposed to be processed into needle-punched nonwoven materials with a selection of an effective antistatic treatment. Full article

13 pages, 2613 KiB

Open AccessArticle

Development of Soft Composite Based Anisotropic Synthetic Skin for Biomechanical Testing

by Vivek Gupta, Rohan Singla, Gurpreet Singh and Arnab Chanda

Fibers 2023, 11(6), 55; https://doi.org/10.3390/fib11060055 - 16 Jun 2023

Cited by 1 | Viewed by 1151

Abstract

Human skin exhibits highly varying mechanical properties, thickness, hardness, and anisotropy by virtue of changing fiber distributions and orientations, across different body locations. To date, only a few studies have computationally simulated skin anisotropy and no experimental study on synthetic skin exists which [...] Read more.

Human skin exhibits highly varying mechanical properties, thickness, hardness, and anisotropy by virtue of changing fiber distributions and orientations, across different body locations. To date, only a few studies have computationally simulated skin anisotropy and no experimental study on synthetic skin exists which can mimic the accurate biomechanical properties of the skin. In this work, unique anisotropic synthetic skin samples were created using an elastic composite-based structure. Both single and multi-layer synthetic skin were fabricated with consistent fiber density and fiber dimensions and varying fiber angles to generate over 100 compositions. The compositions implied stress versus stretch responses in mechanical biaxial testing were compared to those of the skin of a person. Hyperelastic constitutive models were used to characterize the non-uniform test results. The created anisotropic synthetic skin must be essential for reliable Biomechanical investigation of skin free from ethical concerns, undertaking medical training and researching skin pathophysiology and injuries. Full article

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14 pages, 4090 KiB

Open AccessFeature PaperArticle

Recent Achievements in Development of Chalcogenide Optical Fibers for Mid-IR Sensing

by Vladimir S. Shiryaev, Alexander P. Velmuzhov, Tatiana V. Kotereva, Elizaveta A. Tyurina, Maksim V. Sukhanov and Ella V. Karaksina

Fibers 2023, 11(6), 54; https://doi.org/10.3390/fib11060054 - 16 Jun 2023

Cited by 2 | Viewed by 1203

Abstract

Recent results of research of passive and active optical waveguides made of high-purity chalcogenide glasses for middle infrared fiberoptic evanescent wave spectroscopy of liquid and gaseous substances are presented. On the basis of selenide and telluride glass fibers, novel types of highly sensitive [...] Read more.

Recent results of research of passive and active optical waveguides made of high-purity chalcogenide glasses for middle infrared fiberoptic evanescent wave spectroscopy of liquid and gaseous substances are presented. On the basis of selenide and telluride glass fibers, novel types of highly sensitive fiber probes are developed. On the basis of Pr(3+)- and Tb(3+)-doped Ga(In)-Ge-As-Se and Ga-Ge-Sb-Se glass fibers, the 4.2–6 μm wavelength radiation sources are created for all-fiber sensor systems. Successful testing of chalcogenide glass fiber sensors for the analysis of some liquid and gaseous mixtures was carried out. Full article

(This article belongs to the Special Issue Fiber Laser Sources II)

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19 pages, 3438 KiB

Open AccessArticle

Failure Mode Prediction of Unreinforced Masonry (URM) Walls Retrofitted with Cementitious Textile Reinforced Mortar (TRM)

by Athanasia K. Thomoglou, Martha A. Karabini, Dimitra V. Achillopoulou, Theodoros C. Rousakis and Constantin E. Chalioris

Fibers 2023, 11(6), 53; https://doi.org/10.3390/fib11060053 - 15 Jun 2023

Cited by 5 | Viewed by 1588

Abstract

The brittle failure of unreinforced masonry (URM) walls when subjected to in-plane loads present low shear strength remains a critical issue. The investigation presented in this paper touches on the retrofitting of URM structures with textile-reinforced mortar (TRM), which enables shifting the shear [...] Read more.

The brittle failure of unreinforced masonry (URM) walls when subjected to in-plane loads present low shear strength remains a critical issue. The investigation presented in this paper touches on the retrofitting of URM structures with textile-reinforced mortar (TRM), which enables shifting the shear failure mode from a brittle to a pseudo-ductile mode. Despite many guidelines for applying composite materials for retrofitting and predicting the performance of strengthened structures, the application of TRM systems in masonry walls is not extensively described. A thorough retrospect of the literature is presented, containing research results relating to different masonry walls, e.g., bricks, cement, and stone blocks strengthened with TRM jackets and subjected to diagonal compression loads. The critical issue of this study is the failure mode of the retrofitted masonry walls. Available prediction models are presented, and their predictions are compared to the experimental results based on their failure modes. The novelty of this study is the more accurate failure mode prediction of reinforced masonry with TRM and also of the shear strength with the proposed model, Thomoglou et al., 2020, at an optimal level compared to existing regulations and models. The novel prediction model estimates the shear failure mode of the strengthened wall while considering the contribution of all components, e.g., block, render mortar, strengthening textile, and cementitious matrix, by modifying the expressions of the Eurocode 8 provisions. The results have shown that the proposed model presents an optimum accuracy in predicting the failure mode of all different masonry walls strengthened with various TRM jackets and could be taken into account in the regulations for reliable forecasting. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymers and Fiber-Reinforced Cement-Based Mortars in Repair/Strengthening Methods of Masonry and Reinforced Concrete Structural Members)

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10 pages, 2029 KiB

Open AccessArticle

Optimization of the Core Compound for Ytterbium Ultra-Short Cavity Fiber Lasers

by Andrey Rybaltovsky, Mikhail Yashkov, Alexey Abramov, Andrey Umnikov, Mikhail Likhachev and Denis Lipatov

Fibers 2023, 11(6), 52; https://doi.org/10.3390/fib11060052 - 13 Jun 2023

Viewed by 1077

Abstract

Highly ytterbium-, aluminum- and phosphorus-co-doped silica fibers with low optical losses were fabricated by the MCVD method, utilizing an all-gas-phase deposition technique. Optical and laser properties of the active fibers with a phosphosilicate and aluminophosphosilicate glass cores doped with 1.85 mol% and 1.27 [...] Read more.

Highly ytterbium-, aluminum- and phosphorus-co-doped silica fibers with low optical losses were fabricated by the MCVD method, utilizing an all-gas-phase deposition technique. Optical and laser properties of the active fibers with a phosphosilicate and aluminophosphosilicate glass cores doped with 1.85 mol% and 1.27 mol% Yb₂O₃ were thoroughly investigated. With the help of hydrogen loading, it was possible to induce highly reflective Bragg grating in both fiber samples using the standard phase-mask technique and 193 nm-UV laser irradiation. The ultra-short (less than 2 cm long) Fabry–Perot laser cavities were fabricated by inscribing two fiber Bragg gratings (highly and partially reflective FBGs) directly in the core of the fiber samples. The highest pump-to-signal conversion efficiency of 47% was demonstrated in such laser configuration using phosphosilicate fiber. The reasons for the low efficiency of aluminophosphosilicate fiber are discussed. Full article

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13 pages, 4160 KiB

Open AccessArticle

A Refinement of Backward Correlation Technique for Precise Brillouin Frequency Shift Extraction

by Fedor L. Barkov, Anton I. Krivosheev, Yuri A. Konstantinov and Andrey R. Davydov

Fibers 2023, 11(6), 51; https://doi.org/10.3390/fib11060051 - 12 Jun 2023

Cited by 2 | Viewed by 957

Abstract

A new method for extracting the Brillouin frequency shift (BFS) from the Brillouin gain spectrum (BGS), the modified backward correlation method (MBWC), is presented. The possibilities of using MBWC, and MBWC in combination with the Lorentzian curve fitting (LCF) based on Levenberg–Marquardt (LM) [...] Read more.

A new method for extracting the Brillouin frequency shift (BFS) from the Brillouin gain spectrum (BGS), the modified backward correlation method (MBWC), is presented. The possibilities of using MBWC, and MBWC in combination with the Lorentzian curve fitting (LCF) based on Levenberg–Marquardt (LM) method, are studied. The effectiveness of the new method, and its combination with LM, has been demonstrated for processing spectra with a low signal-to-noise ratio (SNR). The experiments, which were in good agreement with the performed simulation, showed that at SNR = 0 dB, the combined (MBWC + LM) method provided the BFS extraction error of less than 4 MHz, while the state-of-the-art LM algorithm extracted it with the error greater than 4.5 MHz. The advantage of correlation methods becomes more significant with the decreasing SNR: at SNR = −2 dB, the LM’s error is 14.3 MHz, and that of the combined one is 8.1 MHz. Full article

(This article belongs to the Special Issue Optical Fibers as a Key Element of Distributed Sensor Systems II)

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47 pages, 20432 KiB

Open AccessArticle

Investigation of the Tendency of Carbon Fibers to Disintegrate into Respirable Fiber-Shaped Fragments

by Asmus Meyer-Plath, Dominic Kehren, Anna Große, Romy Naumann, Marcel Hofmann, Tanja Schneck, Antje Ota, Frank Hermanutz, Nico Dziurowitz, Carmen Thim, Sabine Plitzko and Daphne Bäger

Fibers 2023, 11(6), 50; https://doi.org/10.3390/fib11060050 - 06 Jun 2023

Viewed by 1433

Abstract

Recent reports of the release of large numbers of respirable and critically long fiber-shaped fragments from mesophase pitch-based carbon fiber polymer composites during machining and tensile testing have raised inhalation toxicological concerns. As carbon fibers and their fragments are to be considered as [...] Read more.

Recent reports of the release of large numbers of respirable and critically long fiber-shaped fragments from mesophase pitch-based carbon fiber polymer composites during machining and tensile testing have raised inhalation toxicological concerns. As carbon fibers and their fragments are to be considered as inherently biodurable, the fiber pathogenicity paradigm motivated the development of a laboratory test method to assess the propensity of different types of carbon fibers to form such fragments. It uses spallation testing of carbon fibers by impact grinding in an oscillating ball mill. The resulting fragments were dispersed on track-etched membrane filters and morphologically analyzed by scanning electron microscopy. The method was applied to nine different carbon fiber types synthesized from polyacrylonitrile, mesophase or isotropic pitch, covering a broad range of material properties. Significant differences in the morphology of formed fragments were observed between the materials studied. These were statistically analyzed to relate disintegration characteristics to material properties and to rank the carbon fiber types according to their propensity to form respirable fiber fragments. This tendency was found to be lower for polyacrylonitrile-based and isotropic pitch-based carbon fibers than for mesophase pitch-based carbon fibers, but still significant. Although there are currently only few reports in the literature of increased respirable fiber dust concentrations during the machining of polyacrylonitrile-based carbon fiber composites, we conclude that such materials have the potential to form critical fiber morphologies of WHO dimensions. For safe-and-sustainable carbon fiber-reinforced composites, a better understanding of the material properties that control the carbon fiber fragmentation is imperative. Full article

(This article belongs to the Topic Advanced Carbon Fiber Reinforced Composite Materials)

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20 pages, 5272 KiB

Open AccessArticle

Controllable Water-Triggered Degradation of PCL Solution-Blown Nanofibrous Webs Made Possible by Lipase Enzyme Entrapment

by Fnu Asaduzzaman and Sonja Salmon

Fibers 2023, 11(6), 49; https://doi.org/10.3390/fib11060049 - 01 Jun 2023

Viewed by 1716

Abstract

Polymers in nanofibrous forms offer new opportunities for achieving triggered polymer degradation, which is important for functional and environmental reasons. The polycaprolactone (PCL) nanofibrous nonwoven polymer webs developed in this work by solution blow spinning with entrapped enzymes were completely, rapidly and controllably [...] Read more.

Polymers in nanofibrous forms offer new opportunities for achieving triggered polymer degradation, which is important for functional and environmental reasons. The polycaprolactone (PCL) nanofibrous nonwoven polymer webs developed in this work by solution blow spinning with entrapped enzymes were completely, rapidly and controllably degraded when triggered by exposure to water. Lipase (CALB) from Candida antarctica was successfully entrapped in the PCL webs via an enzyme-compatible water-in-oil emulsion in the PCL–chloroform spinning solution with added surfactant. Protein (enzyme) in the nanofibrous webs was detected by Fourier Transform Infrared Spectroscopy (FTIR), while time of flight-secondary ion mass spectroscopy (ToF-SIMS) and laser confocal microscopy indicated that enzymes were immobilized within solid fibers as well as within microbead structures distributed throughout the webs. Degradation studies of CALB-enzyme functionalized solution-blown nonwoven (EFSBN)-PCL webs at 40 °C or ambient temperature showed that EFSBN-PCL webs degraded rapidly when exposed to aqueous pH 8 buffer. Scanning electron microscopy (SEM) images of partially degraded webs showed that thinner fibers disappeared first, thus, controlling fiber dimensions could control degradation rates. Rapid degradation was attributed to the combination of nanofibrous web structure and the distribution of enzymes throughout the webs. CALB immobilized in the solid dry webs exhibited long storage stability at room temperature or when refrigerated, with around 60% catalytic activity being retained after 120 days compared to the initial activity. Dry storage stability at ambient conditions and rapid degradation upon exposure to water demonstrated that EFSBN-PCL could be used as fibers or binders in degradable textile or paper products, as components in packaging, for tissue engineering and for controlled-release drug or controlled-release industrial and consumer product applications. Full article

(This article belongs to the Special Issue Fibers 10th Anniversary: Past, Present, and Future)

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10 pages, 2758 KiB

Open AccessArticle

Multimode Graded Index Fiber with Random Array of Bragg Gratings and Its Raman Lasing Properties

by Alexey G. Kuznetsov, Alexey A. Wolf, Zhibzema E. Munkueva, Alexander V. Dostovalov and Sergey A. Babin

Fibers 2023, 11(6), 48; https://doi.org/10.3390/fib11060048 - 24 May 2023

Cited by 2 | Viewed by 1259

Abstract

Light propagation in multimode fibers is known to experience various nonlinear effects, which are being actively studied. One of the interesting effects is the brightness enhancement at the Raman conversion of the multimode beam in graded index (GRIN) fiber due to beam cleanup [...] Read more.

Light propagation in multimode fibers is known to experience various nonlinear effects, which are being actively studied. One of the interesting effects is the brightness enhancement at the Raman conversion of the multimode beam in graded index (GRIN) fiber due to beam cleanup at Raman amplification and mode selective feedback in the Raman laser cavity based on fiber Bragg gratings (FBGs) with special transverse structure. It is also possible to explore random distributed feedback based on Rayleigh backscattering on natural refractive index fluctuations in GRIN fibers, but it is rather weak, requiring very high power multimode pumping for random lasing. Here, we report on the first realization of femtosecond pulse-inscribed arrays of weak randomly spaced FBGs in GRIN fibers and study Raman lasing at its direct pumping by highly multimode (M²~34) 940-nm laser diodes. The fabricated 1D–3D FBG arrays are used as a complex output mirror, together with the highly reflective input FBG in 1-km fiber. Above threshold pump power (~100 W), random lasing of the Stokes beam at 976 nm is obtained with output power exceeding 28 W at 174 W pumping. The beam quality parameter varies for different arrays, reaching M²~2 at the linewidth narrowing to 0.1–0.2 nm due to the interference effects, with the best characteristics for the 2D array. Full article

(This article belongs to the Special Issue Multimode Nonlinear Optical Fibers)

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Fibers, Volume 11, Issue 6 (June 2023) – 9 articles

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