Fibers

32 pages, 5714 KiB

Open AccessArticle

Polynomial Modeling of Noise Figure in Erbium-Doped Fiber Amplifiers

by Rocco D’Ingillo, Alberto Castronovo, Stefano Straullu and Vittorio Curri

Fibers 2025, 13(3), 34; https://doi.org/10.3390/fib13030034 - 14 Mar 2025

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Erbium-Doped Fiber Amplifiers (EDFAs) are fundamental to optical communication networks, providing signal amplification while introducing noise that affects system performance. Accurate noise figure estimation is critical for optimizing link budgets, monitoring optical Signal-to-Noise Ratio (OSNR), and enabling real-time network optimization. Traditional analytical models, [...] Read more.

Erbium-Doped Fiber Amplifiers (EDFAs) are fundamental to optical communication networks, providing signal amplification while introducing noise that affects system performance. Accurate noise figure estimation is critical for optimizing link budgets, monitoring optical Signal-to-Noise Ratio (OSNR), and enabling real-time network optimization. Traditional analytical models, while computationally efficient, often fail to capture device-specific variations, whereas machine-learning-based approaches require large training datasets and introduce high computational overhead. This paper proposes a polynomial regression model for real-time EDFA noise figure estimation, striking a balance between accuracy and computational efficiency. The model leverages Generalized Least Squares (GLS) regression to fit a multivariate polynomial function to measured EDFA noise figure data, ensuring robustness against measurement noise and dataset variations. The proposed method is benchmarked against experimental measurements from multiple EDFAs, achieving prediction errors that are within the measurement uncertainty of Optical Spectrum Analyzers (OSAs). Furthermore, the model demonstrates strong generalization across different EDFA architectures, outperforming analytical models while requiring significantly less data than deep-learning approaches. Computational efficiency is also analyzed, showing that inference time is below 0.2 ms per evaluation, making the model suitable for real-time digital-twin applications in optical networks. Future work will explore hybrid modeling approaches, integrating physics-based regression with Machine Learning (ML) to enhance performance in high-variance spectral regions. These results highlight the potential of lightweight polynomial regression models as an alternative to complex ML-based solutions, enabling scalable and efficient EDFA performance prediction for next-generation optical networks. Full article

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38 pages, 9959 KiB

Open AccessArticle

Application of Carbon-Fiber-Reinforced Polymer Rods and Ultra-High-Performance Fiber-Reinforced Concrete Jackets with Mechanical Anchorage Systems to Reinforced Concrete Slabs

by Firas Hassan Saeed and Farzad Hejazi

Fibers 2025, 13(3), 33; https://doi.org/10.3390/fib13030033 - 13 Mar 2025

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Abstract

The aim of this experimental study was to develop and evaluate the effectiveness of a new strengthening system for reinforced concrete slabs employing external jackets consisting of ultra-high-performance fiber-reinforced-concrete (UHPFRC) and mechanical anchor systems. The issue of debonding between old and fresh concrete [...] Read more.

The aim of this experimental study was to develop and evaluate the effectiveness of a new strengthening system for reinforced concrete slabs employing external jackets consisting of ultra-high-performance fiber-reinforced-concrete (UHPFRC) and mechanical anchor systems. The issue of debonding between old and fresh concrete layers, as well as the efficiency of utilizing CFRP rods, is the primary challenge of applying the UHPFRC jackets with embedded CFRP rods. In this study, we propose a novel retrofitting technique for implementing a mechanical anchor system to improve the binding of fresh UHPFRC jackets with old RC slabs. An experimental test was conducted by subjecting three slabs to cyclic loads by utilizing a dynamic actuator: a reference slab, a retrofitted slab with an external UHPFRC layer, and a retrofitted slab with an external UHPFRC layer incorporating CFRP bars. Furthermore, finite element models (FEMs) were utilized to investigate the responses of the retrofitted slabs and compare the novel method with traditional strengthening techniques, including near-surface-mounted (NSM) CFRP rods, externally bonded CFRP strips, and epoxy-bonded UHPFRC jackets, as well as two models that were the same as the experimental strengthened slab specimens except for the fact that they did not have a mechanical anchor system. Additionally, analytical mechanistic models were employed to determine the flexural moment capacity of the RC slabs. The experimental findings demonstrated that the proposed strengthening strategy considerably prevented premature debonding and enhanced the maximum load of retrofitted RC slabs by over 82%. Also, the FEM and analytical results are significantly consistent with the experimental outcomes. In conclusion, the newly suggested strengthening technique is a reliable system for enhancing the efficacy of slabs, effectively preventing early debonding between existing and new components. Full article

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16 pages, 5970 KiB

Open AccessArticle

Advanced Vibration of Functionally Graded Material Coupled Plates and Circular Shells with Four Layers

by Chih-Chiang Hong

Fibers 2025, 13(3), 32; https://doi.org/10.3390/fib13030032 - 12 Mar 2025

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Abstract

This study is based on typical thermal studies on thick, functionally graded material (FGM)-coupled plates and circular shells. Numerical studies have been previously published by researchers on the linear first-order shear deformation theory (FSDT) model for thin-thickness and two-layer materials. The present relationship [...] Read more.

This study is based on typical thermal studies on thick, functionally graded material (FGM)-coupled plates and circular shells. Numerical studies have been previously published by researchers on the linear first-order shear deformation theory (FSDT) model for thin-thickness and two-layer materials. The present relationship was further studied by the author on the nonlinear third-order shear deformation theory (TSDT) model for thick-thickness and four-layer FGMs. The material properties of FGM layers deal with the effect of temperature. The novelty of this study is in its further consideration of four layers of FGMs and the non-dimensional shear coefficient. The stiffness and stiffness integrals of the four layers are studied. The material properties in the power law expression of the functions of the four layers are assumed for the first time. Under the conditions of a time sinusoidal, varied thermal loads and simply supported conditions for four layers are studied. Parametric case studies involving temperature, the standard power law form of the index, and the nonlinear term of the displacement theory and shear coefficient for the dynamic stresses and displacements are obtained and presented. Full article

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15 pages, 4088 KiB

Open AccessArticle

Durable Hydrophilic PVDF Hollow Fiber Membrane for Dissolved Organics Separation from High-Salinity Produced Water

by Samuel Oppong, Zongjie He, Gabriela Torres Fernandez, Guoyin Zhang and Jianjia Yu

Fibers 2025, 13(3), 31; https://doi.org/10.3390/fib13030031 - 11 Mar 2025

Viewed by 583

Abstract

Organic compounds are major constituents in produced water that have gained increasing attention due to their negative impacts on operations and the environment. In this study, a novel hydrophilic polyvinylidene fluoride (PVDF) hollow fiber (HF) membrane was formulated and fabricated for organics separation [...] Read more.

Organic compounds are major constituents in produced water that have gained increasing attention due to their negative impacts on operations and the environment. In this study, a novel hydrophilic polyvinylidene fluoride (PVDF) hollow fiber (HF) membrane was formulated and fabricated for organics separation (OS) from oilfield-produced water. The PVDF dope solution was formulated with lithium chloride (LiCl) and polyvinylpyrrolidone (PVP) as synergistic pore agents, and the obtained PVDF HF membranes showed a defect-free asymmetric structure with a stable hydrophilicity. The OS performance was studied in terms of permeate water flux, OS efficiency, and long-term membrane stability using both decanoic acid and real produced water as feed solutions. Specifically, the effects of operating parameters, such as pressure, total organic carbon (TOC), pH, and salinity, on the OS performance were examined in decanoic acid solution. The long-term membrane stability was evaluated through a 60 h continuous OS experiment using real produced water as the feed solution. The used membrane was thoroughly characterized to understand both scaling and fouling phenomena during the OS operation. The results indicated that the membranes showed promising permeate water flux (>500 kg/m²/h at 350 kPa) and OS efficiency (>92%). It also exhibited a near-100% recovery of organics separation efficiency during six cyclic OS experiments due to consistent membrane hydrophilicity. Full article

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21 pages, 7970 KiB

Open AccessArticle

Production of Decolorized Mushroom Pulp for Nonwoven Cotton Composite

by Ho-Seong Im, Satomi Tagawa, Jae-Seok Jeong and Hyun-Jae Shin

Fibers 2025, 13(3), 30; https://doi.org/10.3390/fib13030030 - 5 Mar 2025

Viewed by 921

Abstract

Cotton, widely used in the textile industry, has a significant environmental impact due to soil degradation and excessive water consumption during cultivation. As a result, there is a growing need for biodegradable alternatives. This study pioneers the development of decolorized mushroom pulps (DMPs) [...] Read more.

Cotton, widely used in the textile industry, has a significant environmental impact due to soil degradation and excessive water consumption during cultivation. As a result, there is a growing need for biodegradable alternatives. This study pioneers the development of decolorized mushroom pulps (DMPs) from edible mushrooms as a sustainable replacement for cotton. Decolorization of fruiting bodies showed the highest reactivity with hydrogen peroxide (H₂O₂). At the same time, mycelium responded more effectively to sodium hypochlorite (NaClO), though this led to structural changes such as melting and twisting. Potassium was detected in fruiting bodies but absent in mycelium, and higher salt content was noted in Agaricus bisporus and Trametes orientalis compared to Pleurotus ostreatus and Flammulina velutipes. Future research should focus on preserving mycelial integrity or developing strains that eliminate the need for decolorization treatments, advancing DMPs as viable biotextile materials. Full article

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11 pages, 2484 KiB

Open AccessArticle

High-Pressure Hydrogen Influence on Cellulose Nanofibers Filled Nitrile Rubber: Performance in Storage Applications

by Sheng Ye, Sohail Yasin, Haijie Zhi, Yihu Song, Chaohua Gu and Jianfeng Shi

Fibers 2025, 13(3), 29; https://doi.org/10.3390/fib13030029 - 5 Mar 2025

Viewed by 643

Abstract

High-pressure hydrogen storage systems (up to 100 MPa) require advanced materials for safety and reliability, particularly for rubber seals, which are prone to degradation under extreme conditions. This study explores the use of cellulose nanofibers (CNFs) and cellulose nanocrystals (CNCs) as sustainable nanofillers [...] Read more.

High-pressure hydrogen storage systems (up to 100 MPa) require advanced materials for safety and reliability, particularly for rubber seals, which are prone to degradation under extreme conditions. This study explores the use of cellulose nanofibers (CNFs) and cellulose nanocrystals (CNCs) as sustainable nanofillers for nitrile butadiene rubber (NBR) latex nanocomposites. CNFs and CNCs were evaluated for their effects on mechanical properties, crosslink density, and resistance to high-pressure hydrogen exposure in rubber O-rings. A life cycle assessment (LCA) was carried to assess the environmental impact of these nanocomposites. The results showed that CNF-filled NBR composites exhibited better resistance to bubble formation under hydrogen exposure compared to CNC-filled ones. However, the LCA indicated relatively high environmental impacts for both, reaching up to 2.5 kg CO₂ eq. in Global Warming Potential (GWP), highlighting the need for further optimization of production processes. This study demonstrates the potential of cellulose nanofillers to improve NBR performance while advancing sustainable hydrogen storage materials. Full article

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19 pages, 7052 KiB

Open AccessArticle

Experimental Study on the Valorization of Rice Straw as Fiber for Concrete

by Hesam Doostkami, David Hernández-Figueirido, Vicente Albero, Ana Piquer, Pedro Serna and Marta Roig-Flores

Fibers 2025, 13(3), 28; https://doi.org/10.3390/fib13030028 - 5 Mar 2025

Viewed by 697

Abstract

Rice straw is an agricultural waste that is difficult to manage and has traditionally been burned or buried, leading to environmental problems. Because of this, the introduction of rice straw into concrete has been proposed to revalue this residue. This investigation shows experimental [...] Read more.

Rice straw is an agricultural waste that is difficult to manage and has traditionally been burned or buried, leading to environmental problems. Because of this, the introduction of rice straw into concrete has been proposed to revalue this residue. This investigation shows experimental work carried out to prepare rice straw fibers and introduce them into a concrete mix as macrofibers. In addition, three fiber treatments were compared: two alkaline and one thermal. Four concrete mixes were studied: a reference mix, two concrete mixes with untreated rice straw fibers in two dosages, 10 kg/m³ and 15 kg/m³, and a fourth concrete mix with 10 kg/m³ of fiber treated with sodium hydroxide. The properties analyzed are workability, compression flexural strength, and shrinkage. The results show that the rice straw fiber used in this work improves concrete flexural strength at the peak but does not provide post-crack residual flexural strength. The sodium hydroxide treatment was effective in obtaining a more cohesive mix and lower setting time delay and slightly improved the performance of the rice straw fiber at the flexural strength peak. In summary, concrete can be used to encapsulate this agricultural waste material, providing enough strength for several engineering applications (>30 MPa). Full article

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19 pages, 3937 KiB

Open AccessReview

Geometric Characterisation of Stochastic Fibrous Networks: A Comprehensive Review

by Yagiz Kayali, Andrew Gleadall and Vadim V. Silberschmidt

Fibers 2025, 13(3), 27; https://doi.org/10.3390/fib13030027 - 5 Mar 2025

Viewed by 765

Abstract

Fibrous networks are porous materials that can have stochastic and uniform microstructures. Various fibrous networks can be found in nature (e.g., collagens, hydrogels, etc.) or manufactured (e.g., composites and nonwovens). This study focuses on the geometrical characterisation of stochastic fibrous networks with continuous [...] Read more.

Fibrous networks are porous materials that can have stochastic and uniform microstructures. Various fibrous networks can be found in nature (e.g., collagens, hydrogels, etc.) or manufactured (e.g., composites and nonwovens). This study focuses on the geometrical characterisation of stochastic fibrous networks with continuous fibres in a 2D domain, discussing their main relevant parameters: basis weight, orientation distribution function, crimp, porosity, spatial distribution of fibres (uniformity), and fibre intersections. The comprehensive review of the literature is combined with original results to understand the effect of the analysed parameters on various features of fibrous networks such as mechanical performance, filtration, insulation, etc. Full article

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43 pages, 27240 KiB

Open AccessArticle

An Experimental Investigation on the Effect of Incorporating Natural Fibers on the Mechanical and Durability Properties of Concrete by Using Treated Hybrid Fiber-Reinforced Concrete Application

by Anteneh Geremew, Amelie Outtier, Pieter De Winne, Tamene Adugna Demissie and Hans De Backer

Fibers 2025, 13(3), 26; https://doi.org/10.3390/fib13030026 - 28 Feb 2025

Viewed by 1293

Abstract

This research explores the use of treated hybrid natural fibers—wheat straw and bamboo—as reinforcements in concrete for pavement applications. Motivated by environmental and economic benefits, the study investigates how these fibers can enhance the mechanical and durability properties of concrete. Wheat straw fibers, [...] Read more.

This research explores the use of treated hybrid natural fibers—wheat straw and bamboo—as reinforcements in concrete for pavement applications. Motivated by environmental and economic benefits, the study investigates how these fibers can enhance the mechanical and durability properties of concrete. Wheat straw fibers, abundant in Ethiopia due to extensive wheat farming, help control micro-cracks and increase the tensile strength of concrete, while bamboo fibers, also locally available, reduce macro-crack propagation and improve concrete toughness. To prepare these fibers, wheat straw was cut to 25 mm in length and bamboo fibers were treated with a 5% sodium hydroxide solution before being cut into lengths of 30, 45, and 60 mm. A concrete mix targeting a cube compressive strength of 30 MPa incorporated 0.1% wheat straw fibers, with varying bamboo fiber contents (0.5%, 1%, and 1.5%) by weight of cement. The results indicate that the uniquely treated hybrid natural fiber-reinforced concrete mix exhibits noticeable enhancements in mechanical properties, with approximate increases of 4.16%, 8.80%, and 8.93% at 7, 28, and 56 days, respectively. Furthermore, the split tensile strength, flexural strength, and durability properties of the concrete were significantly improved by the proposed fiber concentration and length compared to the control concrete mix design. This treatment also shifted the failure mode of the concrete from brittle to ductile and enhanced its energy absorption capacity up to 7.88% higher than that of the control concrete. Based on the AASHTO 1993 pavement design guidelines, this fiber-reinforced concrete reduces pavement thickness by 11% compared to the control concrete while improving post-cracking behavior. This hybrid natural fiber-reinforced concrete presents a promising, sustainable, and eco-friendly alternative for rigid pavement construction. Full article

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31 pages, 27163 KiB

Open AccessArticle

Synergistic Use of Nanosilica and Basalt Fibers on Mechanical Properties of Internally Cured Concrete with SAP: An Experimental Analysis and Optimization via Response Surface Methodology

by Said Mirgan Borito, Han Zhu, Yasser E. Ibrahim, Sadi Ibrahim Haruna and Zhao Bo

Fibers 2025, 13(3), 25; https://doi.org/10.3390/fib13030025 - 26 Feb 2025

Viewed by 937

Abstract

This study explores the combined effects of nanosilica (NS) and basalt fibers (BF) on the mechanical and microstructural properties of superabsorbent polymer (SAP)-modified concrete. NS (0–1.5% replaced by cement weight) and BF (0–1.2% by volume fraction) were incorporated to optimize compressive, flexural, and [...] Read more.

This study explores the combined effects of nanosilica (NS) and basalt fibers (BF) on the mechanical and microstructural properties of superabsorbent polymer (SAP)-modified concrete. NS (0–1.5% replaced by cement weight) and BF (0–1.2% by volume fraction) were incorporated to optimize compressive, flexural, and split-tensile strengths using response surface methodology. Digital Image Correlation (DIC) was employed to analyze failure mechanisms. Results show that while SAP alone reduced strength, the addition of NS and BF mitigated this loss through synergistic microstructure enhancement and crack-bridging reinforcement. The optimal mix (0.9% NS and 1.2% BF) increased compressive, flexural, and split-tensile strengths by 15.3%, 10.0%, and 14.0%, respectively. SEM analysis revealed that NS filled SAP-induced pores, while BF limited crack propagation, contributing to improved mechanical strength of SAP-modified concrete. This hybrid approach offers a promising solution for durable and sustainable concrete pavements. Full article

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16 pages, 5390 KiB

Open AccessArticle

Flammability of Plant-Based Loose-Fill Thermal Insulation: Insights from Wheat Straw, Corn Stalk, and Water Reed

by Martins Andzs, Ramunas Tupciauskas, Andris Berzins, Gunars Pavlovics, Janis Rizikovs, Ulla Milbreta and Laura Andze

Fibers 2025, 13(3), 24; https://doi.org/10.3390/fib13030024 - 24 Feb 2025

Viewed by 682

Abstract

This study investigates the fire resistance capabilities of newly developed loose-fill thermal insulation materials crafted from annual plants such as wheat straw, corn stalk, and water reed. Three processing methodologies were employed: mechanical crushing (raw, size ≤ 20 mm), chemi-mechanical pulping (CMP) using [...] Read more.

This study investigates the fire resistance capabilities of newly developed loose-fill thermal insulation materials crafted from annual plants such as wheat straw, corn stalk, and water reed. Three processing methodologies were employed: mechanical crushing (raw, size ≤ 20 mm), chemi-mechanical pulping (CMP) using 4% sodium hydroxide, and steam explosion (SE). An admixture of boric acid (8%) and tetraborate (7%) was added to all treated materials to enhance fire retardancy. The fire reaction characteristics of the insulation materials were assessed using a cone calorimeter measuring the key parameters like time to ignition, total heat release, heat release rate, and total smoke production. The findings indicate that nearly all tested insulation samples, apart from the raw and SE water reed, demonstrated fire resistance comparable to commercial cellulose insulation, surpassing the fire performance of various synthetic foams and composite materials. Furthermore, the single-flame source fire tests indicated that the developed insulation materials achieved a fire classification E, except for the SE water reed sample. Thus, the fire performance results approve the suitability of developed plant-based insulation materials for competing materials in building constructions. Full article

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Fibers, Volume 13, Issue 3 (March 2025) – 11 articles

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