Fibers

12 pages, 2704 KiB

Open AccessArticle

A High-Flexibility Contact Force Sensor Based on the 8-Shaped Wound Polymer Optical Fiber for Human Safety in Human–Robot Collaboration

by Yi Liu, Yaru Zuo, Xueyao Jiang, Xuezhu Li, Weihao Yuan and Wenhong Cao

Fibers 2025, 13(2), 15; https://doi.org/10.3390/fib13020015 - 2 Feb 2025

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Abstract

Human–robot collaboration is a new trend in modern manufacturing. Safety, or human protection, is of great significance due to humans and robots sharing the same workshop space. To achieve effective protection, in this paper, a contact force sensor based on an 8-shaped wound polymer optical fiber is proposed. The 8-shaped wound structure can convert the normal contact force to the shrinkage of the 8-shaped optical fiber ring. The macro-bending loss of the optical fiber is used to detect the contact force. Compared with conventional sensors, the proposed scheme has the advantage of high flexibility, low cost, fast response, and high repeatability, which shows great promise in actively alerting users to potential collisions and passively reducing the harm caused to humans. Full article

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4 pages, 139 KiB

Open AccessEditorial

Perspectives on Natural Fibers’ Competitiveness and Sustainability

by Mourad Krifa and Vinoth Kumar Gnanasekar

Fibers 2025, 13(2), 14; https://doi.org/10.3390/fib13020014 - 2 Feb 2025

Viewed by 368

Abstract

Since antiquity, natural fibers have been a vital component of human civilization [...] Full article

(This article belongs to the Special Issue Natural Fiber Competitiveness and Sustainability)

26 pages, 4923 KiB

Open AccessReview

Advancements in Clothing Thermal Comfort for Cold Intolerance

by Amare Abuhay, Melkie Getnet Tadesse, Baye Berhanu, Benny Malengier and Lieva Van Langenhove

Fibers 2025, 13(2), 13; https://doi.org/10.3390/fib13020013 - 31 Jan 2025

Viewed by 457

Abstract

Due to constantly shifting environmental and personal circumstances, humans have a wide range of thermal comfort needs. Cold intolerance (CI) is a personalized thermoregulation disorder characterized by a persistently cold-feeling problem, regardless of weather conditions. Improvements in clothing thermal comfort can help maintain proper insulation levels, hence reducing excess heat loss brought on by thermoregulation disorders since the wearer’s thermal comfort is impacted by controllable environmental and personal factors. Despite extensive research on cold-proof clothing, no studies have examined the current status of cold protective clothing systems when taking individual considerations into account, particularly those who use them and have cold sensitivity. There is a significant study gap in research on cold intolerance discomfort and advancements in appropriate cold protection apparel applied to individuals with thermoregulation disorders. Accordingly, this paper reviews the occurrence and severity of cold intolerance and its comfort challenges. It also addresses recent developments in cold protective clothing design, aimed at opening pathways for further investigation into adopting this cutting-edge technology for cold intolerance wear design. This review also aims to clarify the existing opportunities for enhancing the thermal insulation capabilities and other comfort factors of cold protection apparel, which are conducted during the stages of garment design and clothing material/textile manufacture. A thorough assessment of the research on introducing novel surface finishing methods in the pretreatment section and modifying the structural properties of garment materials at the fiber/yarn or weaving stage is conducted. Furthermore, we systematically discuss the potential design solutions regarding fit and size as well as stitching technologies during garment development for thermal insulation enhancement of cold protective clothing design. Full article

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19 pages, 6443 KiB

Open AccessArticle

Effect of GFRP and CFPR Hybrid Confinement on the Compressive Performance of Concrete

by Marina L. Moretti

Fibers 2025, 13(2), 12; https://doi.org/10.3390/fib13020012 - 24 Jan 2025

Viewed by 352

Abstract

Application of hybrid jackets consisting of comparatively stiff FRP materials for the seismic retrofit of substandard RC columns, aiming at reducing the risk of buckling and of brittle failure, which are typical to older columns, is a promising challenge. Given the sparsity of similar experimental data, the objective of this paper is to study the hybrid effect in concrete confined with conventional carbon- and glass- reinforced polymer fabrics (CFRP and GFRP, respectively). Twenty-six concrete cylinders, wrapped by one to three layers of CFRP and GFRP with different fiber configurations, were tested in compression. A clear hybrid effect was observed, consisting of a less brittle failure and an improved confinement as compared to the behavior of simple jackets. Furthermore, hybrid specimens, in which a CFRP layer is substituted by a GFRP layer, appear to display similar efficiency in confinement compared to specimens with a stiffer jacket consisting of more CFRP sheets, which are expected to experience 30 to 40% higher lateral pressure owing to the stiffer jacket. A design model to estimate peak concrete compressive strength and axial strain is proposed. The results are promising towards the potential application of similar hybrid jackets for the seismic rehabilitation of older RC columns. Full article

(This article belongs to the Special Issue Fracture Behavior of Fiber-Reinforced Building Materials)

31 pages, 1892 KiB

Open AccessArticle

Optimizing Controlled-Resonance Acoustic Metamaterials with Perforated Plexiglass Disks, Honeycomb Structures, and Embedded Metallic Masses

by Giuseppe Ciaburro, Gino Iannace and Virginia Puyana Romero

Fibers 2025, 13(2), 11; https://doi.org/10.3390/fib13020011 - 22 Jan 2025

Viewed by 463

Abstract

Acoustic metamaterials offer new opportunities for controlling sound waves through engineered material configurations at the sub-wavelength scale. In this research, we present the optimization of a resonance-controlled acoustic metamaterial based on a sandwich structure composed of perforated plexiglass disks, honeycomb structures, and added metal masses. The innovative approach consists of integrating perforated plexiglass disks interspersed with honeycomb structures, which act as multiple and complex Helmholtz resonators, and adding metal masses to introduce resonances at specific frequencies. The metamaterial’s acoustic properties were experimentally characterized using an impedance tube (Kundt tube), allowing the measurement of the Sound Absorption Coefficient (SAC) over an expansive frequency selection. The results demonstrate a substantial enhancement in sound absorption at the target frequencies, demonstrating the effectiveness of the introduced resonances. Numerical simulations using an Artificial Neural Network (ANN) model in MATLAB environment were used to analyze the distribution of resonances and optimize the structural configuration. To effectively evaluate the acoustic properties of the metamaterial, various configurations were analyzed using perforated plexiglass disks combined with different layers of honeycombs arranged in a sandwich structure with a thickness ranging from 41 to 45 mm. A comparison of these configurations revealed a notable increase in the Sound Absorption Coefficient (SAC) when employing three layers of perforated plexiglass disks and adding masses to the first disk (about 14%). This study highlights the potential of resonance-controlled metamaterials for advanced applications in noise control and acoustic engineering. Full article

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Fibers, Volume 13, Issue 2 (February 2025) – 5 articles

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