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Fibers, Volume 12, Issue 6 (June 2024) – 5 articles

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13 pages, 9510 KiB

Open AccessArticle

Potentials of Polyacrylonitrile Substitution by Lignin for Continuous Manufactured Lignin/Polyacrylonitrile-Blend-Based Carbon Fibers

by Daniel Sebastian Jens Wolz, Robert Seidel-Greiff, Thomas Behnisch, Iris Kruppke, Irina Kuznik, Paul Bertram, Hubert Jäger, Maik Gude and Chokri Cherif

Fibers 2024, 12(6), 50; https://0-doi-org.brum.beds.ac.uk/10.3390/fib12060050 - 18 Jun 2024

Viewed by 325

Abstract

While carbon fibers (CFs) are still the most attractive reinforcement material for lightweight structures, they are mostly manufactured using crude oil-based process chains. To achieve a higher eco-efficiency, the partial substitution of polyacrylonitrile (PAN) by renewable materials, such as lignin, is investigated. So far, this investigation has only been carried out for batch manufacturing studies, neglecting the transfer and validation to continuous CF manufacturing. Therefore, this work is the first to investigate the possibility of partial substituting lignin for PAN in a continuous process. Lignin/PAN-blended CFs with up to 15 wt.-% lignin were able to attain mechanical properties comparable to unmodified PAN-based carbon fibers, achieving tensile strengths of up to 2466 MPa and a Young’s Modulus of 200 Pa. In summary, this study provides the basis for continuous Lignin/PAN-blended CF manufacturing. Full article

(This article belongs to the Special Issue Carbon Fibers from Sustainable Precursors II)

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19 pages, 3763 KiB

Open AccessArticle

Numerical Simulation of Engineering Cementitious Composite Beams Strengthened with Fiber-Reinforced Polymer and Steel Bars

by Nadim I. Shbeeb, Wasim S. Barham and Wala’a Alyahya

Fibers 2024, 12(6), 49; https://0-doi-org.brum.beds.ac.uk/10.3390/fib12060049 - 17 Jun 2024

Viewed by 221

Abstract

In this paper, the flexural performance of the Engineering Cementitious Composite (ECC)-concrete composite beam hybrid reinforced by steel and Fiber Reinforced Polymer (FRP) bars is assessed using nonlinear finite element analysis. The concrete damage plasticity model is used to model the nonlinear behavior of ECC and concrete materials. A perfect bond is assumed at the interface surface between the ECC and concrete. The validity of the numerical model is established through comparison with a previously published experimental study (overall error of about 5.4%). Consequently, the developed model is utilized to consider the effect of hybrid (FRP/steel) tensile reinforcement ratio, thickness of the ECC layer, type of FRP bars, and compressive strength of concrete on the flexure performance. It was evident from the results that the ratio of hybrid (FRP/steel) tensile reinforcement should be carefully chosen to achieve an adequate balance between ductility and carrying load capacity. Additionally, the thickness of the ECC layer plays a crucial role in controlling the hybrid reinforcement’s tensile ratio to prevent rapid failure following the yielding of steel rebars within the ECC layer. Furthermore, the type of FRP bars used in the hybrid reinforcement has influenced the flexural behavior of the composite beam. Conversely, increasing the compressive strength of the concrete has minimal impact on enhancing the mechanical characteristics of the beams, even when considering a change in the type of FRP bars. Full article

15 pages, 2094 KiB

Open AccessArticle

Remote-Controlled Activation of the Release through Drug-Loaded Magnetic Electrospun Fibers

by Richard Ziegler, Shaista Ilyas, Sanjay Mathur, Gerardo F. Goya and Jesús Antonio Fuentes-García

Fibers 2024, 12(6), 48; https://0-doi-org.brum.beds.ac.uk/10.3390/fib12060048 - 3 Jun 2024

Viewed by 336

Abstract

The integration of magnetic nanoparticles within fibrillar structures represents an interesting avenue for the remotely controlled release of therapeutic agents. This work presents a novel drug release platform based on electrospun magnetic fibers (EMFs) combining drugs, magnetic nanoparticles (MNPs) and mesoporous silica nanoparticles (MSNs) for controlled drug delivery via alternating magnetic fields (AMF). The platform was demonstrated to be versatile and effective for hydrophilic ketorolac (KET) and hydrophobic curcumin (CUR) encapsulation and the major response observed for AMF-triggered release was reached using drug-loaded MSNs within the fibers, providing fine control over drug release patterns. The EMFs exhibited excellent inductive heating capabilities, showing a temperature increase of ∆T up to 8 °C within a 5 min AMF pulse. The system is shown to be promising for applications like transdermal pain management, oncological drug delivery, tissue engineering, and wound healing, enabling precise control over drug release in both spatial and temporal dimensions. The findings of this study offer valuable insights into the development of the next generation of smart drug delivery systems, based in multifunctional materials that can be remotely regulated and potentially revolutionize the field of nanomedicine. Full article

23 pages, 2711 KiB

Open AccessArticle

Analysis and Modeling of the System Boundaries of a High-Speed Direct-Yarn-Placement System for In Situ Impregnation of Carbon Fibre Heavy Tows as Textile Reinforcements for Concrete Parts

by Erik Knoch, Steffen Rittner and Klaus Holschemacher

Fibers 2024, 12(6), 47; https://0-doi-org.brum.beds.ac.uk/10.3390/fib12060047 - 31 May 2024

Viewed by 287

Abstract

This study investigates a novel approach in modeling the system limits of a braked, high-speed yarn-laying process with in situ impregnation. Special attention is paid to the investigation of the yarn spool overrun after the robot has come to a standstill. This phenomenon occurs at low yarn tensions in combination with high traversing speed and/or acceleration. The modeling of the yarn spool overrun is carried out using physical equations, taking into account the travel speed, acceleration of the robot, and braking force of the spool brake. Previous research has confirmed various operating points of the yarn-laying process, but a comprehensive and complete analysis of the system limits at different operating points and speeds up to 2 m/s is missing. The result of the study is a novel model that describes the system boundaries of the direct-yarn-placement. Furthermore, models for robot braking time, carbon spool diameter, and spool mass are developed. The proposed models have an

R^{2}

> 0.9674. Regarding the system stability boundaries, the calculations reveal that, as acceleration rises, the minimum tension requirement also increases. The same trend is found for system velocity. At

a = 12.5

%, a minimum tension of 16 N suffices, compared to 23 N and 32 N at

a = 25

% and 50%, respectively. The impact on tension of quadrupling the speed outweighs that of acceleration, with tension increasing by factors of up to 22.5 and 2, respectively. Full article

(This article belongs to the Topic Advanced Composites Manufacturing and Plastics Processing)

14 pages, 3477 KiB

Open AccessArticle

Variation in Activation Parameters for the Preparation of Cellulose-Based Porous Carbon Fibers Used for Electrochemical Applications

by Christoph Unterweger, Nemanja Gavrilov, Stefan Breitenbach, Christian Fürst and Igor A. Pašti

Fibers 2024, 12(6), 46; https://0-doi-org.brum.beds.ac.uk/10.3390/fib12060046 - 27 May 2024

Viewed by 286

Abstract

Porous carbon fibers play a pivotal role in electrochemistry due to their unique structural and textural properties, offering a promising avenue for diverse applications ranging from energy storage to electrocatalysis. In this study, we investigate the intricate relationship between the electrochemical responses of porous carbon fibers synthesized using the Design of Experiments protocol and their textural properties, aiming to elucidate key insights for material design and optimization. Through comprehensive correlation analyses, we uncover notable associations between oxygen reduction reaction mass activities and capacitances measured at different polarization rates, highlighting the significance of pore accessibility in dictating electrochemical performance. While direct correlations with specific surface area and total pore volume for mass activities were not observed, our findings reveal significant trends regarding capacitance retention. Specifically, materials with an elevated specific surface area and total pore volume demonstrate enhanced capacitance retention, particularly under varying charging and discharging rates. These results underscore the importance of optimizing specific surface area and pore volume to maximize capacitive performance across diverse operating conditions. Our study provides valuable guidance for developing porous carbon fibers tailored for superior electrochemical performance in various applications. Full article

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