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Fibers, Volume 4, Issue 1 (March 2016) – 11 articles

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Article
The Durability and Performance of Short Fibers for a Newly Developed Alkali-Activated Binder
Fibers 2016, 4(1), 11; https://doi.org/10.3390/fib4010011 - 15 Mar 2016
Cited by 11 | Viewed by 4404
Abstract
This study reports the development of a fiber-reinforced alkali-activated binder (FRAAB) with an emphasis on the performance and the durability of the fibers in the alkaline alkali-activated binder (AAB)-matrix. For the development of the matrix, the reactive components granulated slag and coal fly [...] Read more.
This study reports the development of a fiber-reinforced alkali-activated binder (FRAAB) with an emphasis on the performance and the durability of the fibers in the alkaline alkali-activated binder (AAB)-matrix. For the development of the matrix, the reactive components granulated slag and coal fly ash were used, which were alkali-activated with a mixture of sodium hydroxide (2–10 mol/L) and an aqueous sodium silicate solution (SiO2/Na2O molar ratio: 2.1) at ambient temperature. For the reinforcement of the matrix integral fibers of alkali-resistant glass (AR-glass), E-glass, basalt, and carbon with a fiber volume content of 0.5% were used. By the integration of these short fibers, the three-point bending tensile strength of the AAB increased strikingly from 4.6 MPa (no fibers) up to 5.7 MPa (carbon) after one day. As a result of the investigations of the alkali resistance, the AR-glass and the carbon fibers showed the highest durability of all fibers in the FRAAB-matrix. In contrast to that, the weight loss of E-glass and basalt fibers was significant under the alkaline condition. According to these results, only the AR-glass and the carbon fibers reveal sufficient durability in the alkaline AAB-matrix. Full article
(This article belongs to the Special Issue Glass Fibers)
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Article
Memory Bandage for Functional Compression Management for Venous Ulcers
Fibers 2016, 4(1), 10; https://doi.org/10.3390/fib4010010 - 19 Feb 2016
Cited by 5 | Viewed by 4335
Abstract
In current compression practice for the treatment of chronic venous disorders, there has always been a challenge of controlled compression by a bandage to achieve a particular pressure range in the affected region of the limb. The challenges in compression in the products [...] Read more.
In current compression practice for the treatment of chronic venous disorders, there has always been a challenge of controlled compression by a bandage to achieve a particular pressure range in the affected region of the limb. The challenges in compression in the products could be solved if there were the possibility of stress control in fabric. Herein, we are exploiting the newly discovered phenomena, i.e., stress memory, in a memory polymer (MP) for the design and investigation of a smart bandage for functional compression benefits. A memory bandage is developed using a blend yarn consisting of MP filaments (segmented polyurethane) and nylon filaments. Results showed the possibility to control or manage the internal stress developed in the bandage in wrapped position by simple heating, and thus allowing pressure readjustment externally. Extra pressure generated by the bandage increases with increasing the level of temperature and strain (p < 0.05). The pressure variations also depend on the number of layers and limb circumference (p < 0.05). The memory bandage could have a great potential over existing conventional compression products, as they could give more freedom to govern pressure level whenever needed during the course of compression therapy as a novel wound care management system. Full article
(This article belongs to the Special Issue Smart Textiles)
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Article
Scaling up the Fabrication of Mechanically-Robust Carbon Nanofiber Foams
Fibers 2016, 4(1), 9; https://doi.org/10.3390/fib4010009 - 15 Feb 2016
Viewed by 4019
Abstract
This work aimed to identify and address the main challenges associated with fabricating large samples of carbon foams composed of interwoven networks of carbon nanofibers. Solutions to two difficulties related with the process of fabricating carbon foams, maximum foam size and catalyst cost, [...] Read more.
This work aimed to identify and address the main challenges associated with fabricating large samples of carbon foams composed of interwoven networks of carbon nanofibers. Solutions to two difficulties related with the process of fabricating carbon foams, maximum foam size and catalyst cost, were developed. First, a simple physical method was invented to scale-up the constrained formation of fibrous nanostructures process (CoFFiN) to fabricate relatively large foams. Specifically, a gas deflector system capable of maintaining conditions supportive of carbon nanofiber foam growth throughout a relatively large mold was developed. ANSYS CFX models were used to simulate the gas flow paths with and without deflectors; the data generated proved to be a very useful tool for the deflector design. Second, a simple method for selectively leaching the Pd catalyst material trapped in the foam during growth was successfully tested. Multiple techniques, including scanning electron microscopy, surface area measurements, and mechanical testing, were employed to characterize the foams generated in this study. All results confirmed that the larger foam samples preserve the basic characteristics: their interwoven nanofiber microstructure forms a low-density tridimensional solid with viscoelastic behavior. Fiber growth mechanisms are also discussed. Larger samples of mechanically-robust carbon nanofiber foams will enable the use of these materials as strain sensors, shock absorbers, selective absorbents for environmental remediation and electrodes for energy storage devices, among other applications. Full article
(This article belongs to the Special Issue Carbon Fibers)
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Article
Combined Transverse Steel-External FRP Confinement Model for Rectangular Reinforced Concrete Columns
Fibers 2016, 4(1), 8; https://doi.org/10.3390/fib4010008 - 06 Feb 2016
Cited by 4 | Viewed by 4542
Abstract
Recently, the need to increase the strength of reinforced concrete members has become a subject that civil engineers are interested in tackling. Of the many proposed solutions, fiber-reinforced polymer (FRP) materials have attracted attention due to their superior properties, such as high strength-to-weight [...] Read more.
Recently, the need to increase the strength of reinforced concrete members has become a subject that civil engineers are interested in tackling. Of the many proposed solutions, fiber-reinforced polymer (FRP) materials have attracted attention due to their superior properties, such as high strength-to-weight ratio, high energy absorption and excellent corrosion resistance. FRP wrapping of concrete columns is done to enhance the ultimate strength due to the confinement effect, which is normally induced by steel ties. The existence of the two confinement systems changes the nature of the problem, thus necessitating specialized nonlinear analysis to obtain the column’s ultimate capacity. Existing research focused on a single confinement system. Furthermore, very limited research on rectangular sections was found in the literature. In this work, a model to estimate the combined behavior of the two systems in rectangular columns is proposed. The calculation of the effective lateral pressure is based on the Lam and Teng model and the Mander model for FRP wraps and steel ties, respectively. The model then generates stress-strain diagrams for both the concrete core and the cover. The model was developed for the analysis in extreme load events, where all possible contributions to the column’s ultimate capacity should be accounted for without any margin of safety. The model was validated against experiments, and the results obtained showed good agreement with almost all of the available experimental data. Full article
(This article belongs to the Special Issue Fiber Reinforced Polymers (FRP) for Infrastructure Applications)
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Article
Changes in Properties of Cement and Lime Mortars When Incorporating Fibers from End-of-Life Tires
Fibers 2016, 4(1), 7; https://doi.org/10.3390/fib4010007 - 05 Feb 2016
Cited by 9 | Viewed by 3989
Abstract
This paper studies the addition of fibers from end-of-life tires to commercial mortar mixtures. Two different types of mortar, one lime-plastic and other cement-fluid, are mixed with different percentage of fibers ranging from 0% to 1%. The changes in bulk density, consistency, compressive [...] Read more.
This paper studies the addition of fibers from end-of-life tires to commercial mortar mixtures. Two different types of mortar, one lime-plastic and other cement-fluid, are mixed with different percentage of fibers ranging from 0% to 1%. The changes in bulk density, consistency, compressive and flexural strength, dynamic Young modulus and water absorption are studied. According to the results, consistency is the property that shows more relevant changes for an addition of 0.25% fibers. Consistency is related to workability and affects the water absorption and the Young modulus values. On the contrary, bulk density and mechanical properties did not change with the addition of fibers. The results prove that this fiber, considered a waste from recycling of end-of-life tires, can be used in commercial mixtures without losing strength. On the other hand, mortar workability limits the amount of fibers that can be included in the mixture and this parameter determines the performance of the mortar. Full article
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Article
Properties of Fiber-Reinforced Mortars Incorporating Nano-Silica
Fibers 2016, 4(1), 6; https://doi.org/10.3390/fib4010006 - 02 Feb 2016
Cited by 24 | Viewed by 4573
Abstract
Repair and rehabilitation of deteriorating concrete elements are of significant concern in many infrastructural facilities and remain a challenging task. Concerted research efforts are needed to develop repair materials that are sustainable, durable, and cost-effective. Research data show that fiber-reinforced mortars/concretes have superior [...] Read more.
Repair and rehabilitation of deteriorating concrete elements are of significant concern in many infrastructural facilities and remain a challenging task. Concerted research efforts are needed to develop repair materials that are sustainable, durable, and cost-effective. Research data show that fiber-reinforced mortars/concretes have superior performance in terms of volume stability and toughness. In addition, it has been recently reported that nano-silica particles can generally improve the mechanical and durability properties of cement-based systems. Thus, there has been a growing interest in the use of nano-modified fiber-reinforced cementitious composites/mortars (NFRM) in repair and rehabilitation applications of concrete structures. The current study investigates various mechanical and durability properties of nano-modified mortar containing different types of fibers (steel, basalt, and hybrid (basalt and polypropylene)), in terms of compressive and flexural strengths, toughness, drying shrinkage, penetrability, and resistance to salt-frost scaling. The results highlight the overall effectiveness of the NFRM owing to the synergistic effects of nano-silica and fibers. Full article
(This article belongs to the Special Issue Fiber Reinforced Polymers (FRP) for Infrastructure Applications)
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Editorial
Acknowledgement to Reviewers of Fibers in 2015
Fibers 2016, 4(1), 5; https://doi.org/10.3390/fib4010005 - 28 Jan 2016
Viewed by 3454
Abstract
The editors of Fibers would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2015. [...] Full article
Article
Experiment-Based Sensitivity Analysis of Scaled Carbon-Fiber-Reinforced Elastomeric Isolators in Bonded Applications
Fibers 2016, 4(1), 4; https://doi.org/10.3390/fib4010004 - 27 Jan 2016
Cited by 9 | Viewed by 4453
Abstract
Fiber-reinforced elastomeric isolators (FREIs) are a new type of elastomeric base isolation systems. Producing FREIs in the form of long laminated pads and cutting them to the required size significantly reduces the time and cost of the manufacturing process. Due to the lack [...] Read more.
Fiber-reinforced elastomeric isolators (FREIs) are a new type of elastomeric base isolation systems. Producing FREIs in the form of long laminated pads and cutting them to the required size significantly reduces the time and cost of the manufacturing process. Due to the lack of adequate information on the performance of FREIs in bonded applications, the goal of this study is to assess the performance sensitivity of 1/4-scale carbon-FREIs based on the experimental tests. The scaled carbon-FREIs are manufactured using a fast cold-vulcanization process. The effect of several factors including the vertical pressure, the lateral cyclic rate, the number of rubber layers, and the thickness of carbon fiber-reinforced layers are explored on the cyclic behavior of rubber bearings. Results show that the effect of vertical pressure on the lateral response of base isolators is negligible. However, decreasing the cyclic loading rate increases the lateral flexibility and the damping capacity. Additionally, carbon fiber-reinforced layers can be considered as a minor source of energy dissipation. Full article
(This article belongs to the Special Issue Fiber Reinforced Polymers (FRP) for Infrastructure Applications)
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Article
Strengthening of Corroded Reinforced SCC-RAP Members with CFRP
Fibers 2016, 4(1), 3; https://doi.org/10.3390/fib4010003 - 22 Jan 2016
Cited by 1 | Viewed by 3918
Abstract
Corrosion is one of the major problems affecting the durability of reinforced concrete (RC) structures. This paper investigates the effect of rebar corrosion on the performance of reinforced self-consolidating concrete (SCC) members and the effectiveness of repair. A control RC member, which has [...] Read more.
Corrosion is one of the major problems affecting the durability of reinforced concrete (RC) structures. This paper investigates the effect of rebar corrosion on the performance of reinforced self-consolidating concrete (SCC) members and the effectiveness of repair. A control RC member, which has no corrosion problem, was prepared to compare against corroded and repaired members. A number of reinforced concrete members having up to 50% corrosion level were constructed and tested to study the effect of corrosion on the structural performance of RC members. The beams with corrosion problem were repaired using carbon fiber reinforced polymer (CFRP) sheets and U-wraps. All of the beams constructed, which are either not repaired or repaired, in this study were tested under two static line loads until failure. The effect of corrosion and effectiveness of repairing technique were assessed by evaluating the performance in terms of load carrying capacity, deflection, and ductility. Test results revealed that as the corrosion level increases, the loss in load carrying capacity increases. Repairing using CFRP improved the performance of corroded members. For example, when 50% corrosion level was achieved, the beam lost approximately 57% of its load carrying capacity, but when it was repaired, it recovered about 42% of its load carrying capacity. Full article
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Article
Preparation and Properties of Gelatin Fibers Fabricated by Dry Spinning
Fibers 2016, 4(1), 2; https://doi.org/10.3390/fib4010002 - 20 Jan 2016
Cited by 8 | Viewed by 4639
Abstract
Gelatin fibers have been prepared by dry spinning based on the sol-gel transition phenomena of aqueous gelatin solutions. This method is simple and environmentally friendly because only water is used for the spinning, thereby avoiding the use of any toxic organic solvents. A [...] Read more.
Gelatin fibers have been prepared by dry spinning based on the sol-gel transition phenomena of aqueous gelatin solutions. This method is simple and environmentally friendly because only water is used for the spinning, thereby avoiding the use of any toxic organic solvents. A sol-state aqueous solution of gelatin at 50 °C was extruded into air through a thin nozzle at room temperature followed by high-speed stretching in air. As a result, a stretched and shiny gelatin fiber was produced. To improve the mechanical and water-resistant properties of the fibers, a crosslinking treatment by the addition of sugars, denacol, and glutaraldehyde vapor was used. Despite their smooth surfaces, the gelatin fibers exhibited a multi-porous phase on the inside, probably owing to the retention of water during the spinning process. The mean diameters of the obtained fibers with all crosslinking agents were approximately 50–60 μm. Furthermore, the mean tensile strength was increased by all crosslinking agents. In particular, the use of N-acetyl-d-glucosamine and glutaraldehyde as the crosslinkers resulted in a remarkable increase in tensile strength and water resistance. Moreover, their properties were further improved after heat treatment. These fibers also exhibited good water resistance and maintained their morphologies for more than 90 days. Full article
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Article
Carbon Fiber Biocompatibility for Implants
Fibers 2016, 4(1), 1; https://doi.org/10.3390/fib4010001 - 08 Jan 2016
Cited by 23 | Viewed by 5662
Abstract
Carbon fibers have multiple potential advantages in developing high-strength biomaterials with a density close to bone for better stress transfer and electrical properties that enhance tissue formation. As a breakthrough example in biomaterials, a 1.5 mm diameter bisphenol-epoxy/carbon-fiber-reinforced composite rod was compared for [...] Read more.
Carbon fibers have multiple potential advantages in developing high-strength biomaterials with a density close to bone for better stress transfer and electrical properties that enhance tissue formation. As a breakthrough example in biomaterials, a 1.5 mm diameter bisphenol-epoxy/carbon-fiber-reinforced composite rod was compared for two weeks in a rat tibia model with a similar 1.5 mm diameter titanium-6-4 alloy screw manufactured to retain bone implants. Results showed that carbon-fiber-reinforced composite stimulated osseointegration inside the tibia bone marrow measured as percent bone area (PBA) to a great extent when compared to the titanium-6-4 alloy at statistically significant levels. PBA increased significantly with the carbon-fiber composite over the titanium-6-4 alloy for distances from the implant surfaces of 0.1 mm at 77.7% vs. 19.3% (p < 10−8) and 0.8 mm at 41.6% vs. 19.5% (p < 10−4), respectively. The review focuses on carbon fiber properties that increased PBA for enhanced implant osseointegration. Carbon fibers acting as polymer coated electrically conducting micro-biocircuits appear to provide a biocompatible semi-antioxidant property to remove damaging electron free radicals from the surrounding implant surface. Further, carbon fibers by removing excess electrons produced from the cellular mitochondrial electron transport chain during periods of hypoxia perhaps stimulate bone cell recruitment by free-radical chemotactic influences. In addition, well-studied bioorganic cell actin carbon fiber growth would appear to interface in close contact with the carbon-fiber-reinforced composite implant. Resulting subsequent actin carbon fiber/implant carbon fiber contacts then could help in discharging the electron biological overloads through electrochemical gradients to lower negative charges and lower concentration. Full article
(This article belongs to the Special Issue Carbon Fibers)
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