Open AccessArticle
Exploration of Wave Development during Yarn Transverse Impact
Fibers 2017, 5(2), 17; doi:10.3390/fib5020017 -
Abstract
Single yarns have been impacted in a transverse fashion so as to probe the characteristics of resulting wave development. Longitudinal wave speeds were tracked in efforts to directly measure the yarn tensile stiffness, resulting in a slight increase in the modulus of Kevlar
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Single yarns have been impacted in a transverse fashion so as to probe the characteristics of resulting wave development. Longitudinal wave speeds were tracked in efforts to directly measure the yarn tensile stiffness, resulting in a slight increase in the modulus of Kevlar® KM2 and Dyneema® SK76. Additionally, the load developed in AuTx® and Kevlar® KM2 yarns behind the longitudinal wave front has been recorded, providing additional verification for the Smith relations. Further effort to bolster the Smith equations has been successfully performed via tracking transverse wave speeds in AuTx® yarns over a range of impacting velocities. Additional emphasis has been placed at understanding the transverse wave development around the yarn critical velocity, demonstrating that there is a velocity zone where partial yarn failure is detected. Above the critical velocity, measurement of early time transverse wave speeds also agrees with the Smith solution, though the wave speed quickly reduces in value due to the drop in tensile stresses resulting from filament rupture. Finally, the Smith equations have been simplified and are compared to the Cunniff equation, which bear a striking resemblance. Due to such a resemblance, it is suggested that yarn critical velocity experiments can be performed on trial yarn material, and the effect of modifying yarn mechanical properties is discussed. Full article
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Open AccessArticle
Experimental and Analytical Modeling of GFRP Strengthened Grouted Mortarless Masonry Prisms
Fibers 2017, 5(2), 18; doi:10.3390/fib5020018 -
Abstract
The compressive performance of grouted mortarless masonry prisms strengthened with glass fiber-reinforced polymer (GFRP) composites was investigated in this study. A total of 18 grouted mortarless masonry specimens, i.e., nine strengthened with GFRP (called G-GMM) and nine without GFRP (called GMM), were tested
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The compressive performance of grouted mortarless masonry prisms strengthened with glass fiber-reinforced polymer (GFRP) composites was investigated in this study. A total of 18 grouted mortarless masonry specimens, i.e., nine strengthened with GFRP (called G-GMM) and nine without GFRP (called GMM), were tested under uniaxial compression. The effect of grout strength on the compressive strength of the prisms was discussed. Moreover, the effect of GFRP on the cracking load, modulus of elasticity, ultimate bearing capacity, failure modes, compressive stress–strain behavior, and deformation behavior of the specimens was analyzed. The test results indicated that GFRP strengthening increased the ratio of initial cracking load and ultimate load bearing capacity of mortarless masonry to a great extent, i.e., the ratio is 50–80% for G-GMM and 40–65% for GMM. In addition, GFRP clearly improved the deformation capability of the GMM. The tested experimental data were in good agreement with the predicted values using classic expressions. Full article
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Open AccessArticle
Investigation on Strengthening Approaches Adopted for Poorly Detailed RC Corbels
Fibers 2017, 5(2), 16; doi:10.3390/fib5020016 -
Abstract
Poor detailing of the position of bearing pad over reinforced concrete (RC) corbel may lead to premature failure, which is undesired and structurally vulnerable. An appropriate retrofitting solution is necessary to ensure the functionality of such RC corbels. Considering the growing popularity of
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Poor detailing of the position of bearing pad over reinforced concrete (RC) corbel may lead to premature failure, which is undesired and structurally vulnerable. An appropriate retrofitting solution is necessary to ensure the functionality of such RC corbels. Considering the growing popularity of external carbon fiber-reinforced polymer (CFRP) in retrofitting, this research examines the effectiveness of an externally wrapped unidirectional CFRP sheet and compares its performance against traditional retrofitting methods. Moreover, it is intended to fulfill the lack of extensive research on external CFRP application for corbel strengthening. A total of eight medium-scale corbel specimens were tested on vertical load. Observed premature failure due to placing the bearing pad near the edge of corbel was verified and the effectiveness of the proposed structural strengthening solutions was studied. Experimental results show that although the loading capacity of the damaged corbel due to the poor detailing of bearing pad position could not be fully recovered, the external CFRP wrapping method demonstrated superior performance over RC jacketing and was able to prevent localized failure. Further study based on non-linear 3D finite element analysis (FEA) was carried out to identify the governing parameters of each retrofitting solution. Numerical studies suggested important parameters of various retrofitting alternatives for higher capacity assurance. Full article
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Open AccessArticle
Luminescent Properties of Oxazine 170 Perchlorate Doped PMMA Fiber
Fibers 2017, 5(2), 15; doi:10.3390/fib5020015 -
Abstract
The article presents fabrication and luminescent properties of poly(methyl methacrylate) (PMMA) fiber doped by Oxazine 170 perchlorate. The bright fluorescence of polymeric fiber (at molar fluorescent organic dye concentration 4.3 × 10−5) was characterized in terms of spectrum and signal attenuation
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The article presents fabrication and luminescent properties of poly(methyl methacrylate) (PMMA) fiber doped by Oxazine 170 perchlorate. The bright fluorescence of polymeric fiber (at molar fluorescent organic dye concentration 4.3 × 10−5) was characterized in terms of spectrum and signal attenuation vs. the fiber length. The significant changes in fluorescence spectrum (λmax red shift average slope 4.6 nm/cm and Full Width at Half Maximum (FWHM) increasing slope 6.7 nm/cm) have been noticed for the length of the fiber (0.02–0.08 m) which corresponds to a high overlapping region of absorption and emission spectra of used dye. The red shift of λmax (c.a. 80 nm) was presented in fabricated polymeric fiber at distance 0.85 m. The obtained characteristics can be used for luminescent properties optimization of fluorescent organic-dye-doped PMMA fiber. Full article
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Open AccessArticle
Preparation and Characterization of Polymeric-Hybrid PES/TiO2 Hollow Fiber Membranes for Potential Applications in Water Treatment
Fibers 2017, 5(2), 14; doi:10.3390/fib5020014 -
Abstract
In this work, poly(ethersulfone) (PES) ultrafiltration (UF) hollow fibers (HF) were modified by introducing TiO2 nanoparticles (TiO2-NPs) in the polymeric dope, to endow them with photocatalytic properties. Different dope compositions and spinning conditions for producing “blank” PES UF fibers with
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In this work, poly(ethersulfone) (PES) ultrafiltration (UF) hollow fibers (HF) were modified by introducing TiO2 nanoparticles (TiO2-NPs) in the polymeric dope, to endow them with photocatalytic properties. Different dope compositions and spinning conditions for producing “blank” PES UF fibers with suitable properties were investigated. PEO–PPO–PEO (Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol, Pluronic® (Sigma-Aldrich, Milan, Italy) was finally selected as the additive and a suitable dope composition was identified. After the detection of an appropriate dope composition and the optimization of the spinning parameters, PES-TiO2 HF was produced. The optimized composition was employed for preparing the mixed matrix HF loaded with TiO2 NPs. The effect of different TiO2 NP (0.3–1 wt %) concentrations and bore fluid compositions on the fiber morphology and properties were explored. The morphology of the produced fibers was analyzed by Scanning Electron Microscopy (SEM). Fibers were further characterized by measuring: pore size diameters and thickness, porosity, and pure water permeability (PWP). The photocatalytic activity of the new membranes was also tested by UV light irradiation. The model “foulant” methylene blue (MB) was used in order to prove the efficiency of the novel UF membrane for dye photo-degradation. Full article
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Open AccessArticle
The Design of Temperature-Responsive Nanofiber Meshes for Cell Storage Applications
Fibers 2017, 5(1), 13; doi:10.3390/fib5010013 -
Abstract
Here we report on the fabrication and characterization of temperature-responsive electrospun nanofiber meshes using N-isopropylacrylamide homopolymer (PNIPAAm). The effect of molecular weight on fiber formation and their thermoresponsive shrinking/dissolution behaviors were investigated. The PNIPAAm fiber meshes showed much faster temperature-dependent shrinking or
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Here we report on the fabrication and characterization of temperature-responsive electrospun nanofiber meshes using N-isopropylacrylamide homopolymer (PNIPAAm). The effect of molecular weight on fiber formation and their thermoresponsive shrinking/dissolution behaviors were investigated. The PNIPAAm fiber meshes showed much faster temperature-dependent shrinking or dissolution than that of its corresponding film due to its unique fibrous structure. By utilizing these quick and dynamic shrinking/dissolution properties, we successfully demonstrated the temperature-modulated “on-off” capture/release systems for macroscopic or mesoscopic-scale objects. Finally, we explored the potential application of PNIPAAm meshes for cell storage. Full article
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Open AccessReview
Glass and Process Development for the Next Generation of Optical Fibers: A Review
Fibers 2017, 5(1), 11; doi:10.3390/fib5010011 -
Abstract
Applications involving optical fibers have grown considerably in recent years with intense levels of research having been focused on the development of not only new generations of optical fiber materials and designs, but also on new processes for their preparation. In this paper,
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Applications involving optical fibers have grown considerably in recent years with intense levels of research having been focused on the development of not only new generations of optical fiber materials and designs, but also on new processes for their preparation. In this paper, we review the latest developments in advanced materials for optical fibers ranging from silica, to semi-conductors, to particle-containing glasses, to chalcogenides and also in process-related innovations. Full article
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Open AccessArticle
Verification and Validation of a Three-Dimensional Orthotropic Plasticity Constitutive Model Using a Unidirectional Composite
Fibers 2017, 5(1), 12; doi:10.3390/fib5010012 -
Abstract
A three-dimensional constitutive model has been developed for modeling orthotropic composites subject to impact loads. It has three distinct components—a deformation model involving elastic and plastic deformations; a damage model; and a failure model. The model is driven by tabular data that is
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A three-dimensional constitutive model has been developed for modeling orthotropic composites subject to impact loads. It has three distinct components—a deformation model involving elastic and plastic deformations; a damage model; and a failure model. The model is driven by tabular data that is generated either using laboratory tests or via virtual testing. A unidirectional composite—T800/F3900, commonly used in the aerospace industry, is used in the verification and validation tests. While the failure model is under development, these tests indicate that the implementation of the deformation and damage models in a commercial finite element program, LS-DYNA, is efficient, robust and accurate. Full article
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Open AccessArticle
Modeling and Experiments on Ballistic Impact into UHMWPE Yarns Using Flat and Saddle-Nosed Projectiles
Fibers 2017, 5(1), 8; doi:10.3390/fib5010008 -
Abstract
Yarn shooting experiments were conducted to determine the ballistically-relevant, Young’s modulus and tensile strength of ultra-high molecular weight polyethylene (UHMWPE) fiber. Target specimens were Dyneema® SK76 yarns (1760 dtex), twisted to 40 turns/m, and initially tensioned to stresses ranging from 29 to
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Yarn shooting experiments were conducted to determine the ballistically-relevant, Young’s modulus and tensile strength of ultra-high molecular weight polyethylene (UHMWPE) fiber. Target specimens were Dyneema® SK76 yarns (1760 dtex), twisted to 40 turns/m, and initially tensioned to stresses ranging from 29 to 2200 MPa. Yarns were impacted, transversely, by two types of cylindrical steel projectiles at velocities ranging from 150 to 555 m/s: (i) a reverse-fired, fragment simulating projectile (FSP) where the flat rear face impacted the yarn rather than the beveled nose; and (ii) a ‘saddle-nosed projectile’ having a specially contoured nose imparting circular curvature in the region of impact, but opposite curvature transversely to prevent yarn slippage off the nose. Experimental data consisted of sequential photographic images of the progress of the triangular transverse wave, as well as tensile wave speed measured using spaced, piezo-electric sensors. Yarn Young’s modulus, calculated from the tensile wave-speed, varied from 133 GPa at minimal initial tension to 208 GPa at the highest initial tensions. However, varying projectile impact velocity, and thus, the strain jump on impact, had negligible effect on the modulus. Contrary to predictions from the classical Cole-Smith model for 1D yarn impact, the critical velocity for yarn failure differed significantly for the two projectile types, being 18% lower for the flat-faced, reversed FSP projectile compared to the saddle-nosed projectile, which converts to an apparent 25% difference in yarn strength. To explain this difference, a wave-propagation model was developed that incorporates tension wave collision under blunt impact by a flat-faced projectile, in contrast to outward wave propagation in the classical model. Agreement between experiment and model predictions was outstanding across a wide range of initial yarn tensions. However, plots of calculated failure stress versus yarn pre-tension stress resulted in apparent yarn strengths much lower than 3.4 GPa from quasi-static tension tests, although a plot of critical velocity versus initial tension did project to 3.4 GPa at zero velocity. This strength reduction (occurring also in aramid fibers) suggested that transverse fiber distortion and yarn compaction from a compressive shock wave under the projectile results in fiber-on-fiber interference in the emerging transverse wave front, causing a gradient in fiber tensile strains with depth, and strain concentration in fibers nearest the projectile face. A model was developed to illustrate the phenomenon. Full article
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Open AccessEditorial
Glass Fibers: Quo Vadis?
Fibers 2017, 5(1), 10; doi:10.3390/fib5010010 -
Abstract Since the early 1930s, the process of melting glass and subsequently forming fibers, in particular discontinuous fiber glass or continuous glass filaments, evolved into commercial-scale manufacturing.[...] Full article
Open AccessArticle
Role of Inelastic Transverse Compressive Behavior and Multiaxial Loading on the Transverse Impact of Kevlar KM2 Single Fiber
Fibers 2017, 5(1), 9; doi:10.3390/fib5010009 -
Abstract
High-velocity transverse impact of ballistic fabrics and yarns by projectiles subject individual fibers to multi-axial dynamic loading. Single-fiber transverse impact experiments with the current state-of-the-art experimental capabilities are challenging due to the associated micron length-scale. Kevlar® KM2 fibers exhibit a nonlinear inelastic
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High-velocity transverse impact of ballistic fabrics and yarns by projectiles subject individual fibers to multi-axial dynamic loading. Single-fiber transverse impact experiments with the current state-of-the-art experimental capabilities are challenging due to the associated micron length-scale. Kevlar® KM2 fibers exhibit a nonlinear inelastic behavior in transverse compression with an elastic limit less than 1.5% strain. The effect of this transverse behavior on a single KM2 fiber subjected to a cylindrical and a fragment-simulating projectile (FSP) transverse impact is studied with a 3D finite element model. The inelastic behavior results in a significant reduction of fiber bounce velocity and projectile-fiber contact forces up to 38% compared to an elastic impact response. The multiaxial stress states during impact including transverse compression, axial tension, axial compression and interlaminar shear are presented at the location of failure. In addition, the models show a strain concentration over a small length in the fiber under the projectile-fiber contact. A failure criterion, based on maximum axial tensile strain accounting for the gage length, strain rate and multiaxial loading degradation effects are applied to predict the single-fiber breaking speed. Results are compared to the elastic response to assess the importance of inelastic material behavior on failure during a transverse impact. Full article
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Open AccessArticle
Molecular Dynamics Modeling of the Effect of Axial and Transverse Compression on the Residual Tensile Properties of Ballistic Fiber
Fibers 2017, 5(1), 7; doi:10.3390/fib5010007 -
Abstract
Ballistic impact induces multiaxial loading on Kevlar® and polyethylene fibers used in protective armor systems. The influence of multiaxial loading on fiber failure is not well understood. Experiments show reduction in the tensile strength of these fibers after axial and transverse compression.
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Ballistic impact induces multiaxial loading on Kevlar® and polyethylene fibers used in protective armor systems. The influence of multiaxial loading on fiber failure is not well understood. Experiments show reduction in the tensile strength of these fibers after axial and transverse compression. In this paper, we use molecular dynamics (MD) simulations to explain and develop a fundamental understanding of this experimental observation since the property reduction mechanism evolves from the atomistic level. An all-atom MD method is used where bonded and non-bonded atomic interactions are described through a state-of-the-art reactive force field. Monotonic tension simulations in three principal directions of the models are conducted to determine the anisotropic elastic and strength properties. Then the models are subjected to multi-axial loads—axial compression, followed by axial tension and transverse compression, followed by axial tension. MD simulation results indicate that pre-compression distorts the crystal structure, inducing preloading of the covalent bonds and resulting in lower tensile properties. Full article
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Open AccessArticle
Development of Polysulfone Hollow Fiber Porous Supports for High Flux Composite Membranes: Air Plasma and Piranha Etching
Fibers 2017, 5(1), 6; doi:10.3390/fib5010006 -
Abstract
For the development of high efficiency porous supports for composite membrane preparation, polysulfone (PSf) hollow fiber membranes (outer diameter 1.57 mm, inner diameter 1.12 mm) were modified by air plasma using the low temperature plasma treatment pilot plant which is easily scalable to
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For the development of high efficiency porous supports for composite membrane preparation, polysulfone (PSf) hollow fiber membranes (outer diameter 1.57 mm, inner diameter 1.12 mm) were modified by air plasma using the low temperature plasma treatment pilot plant which is easily scalable to industrial level and the Piranha etch (H2O2 + H2SO4). Chemical and plasma modification affected only surface layers and did not cause PSf chemical structure change. The modifications led to surface roughness decrease, which is of great importance for further thin film composite (TFC) membranes fabrication by dense selective layer coating, and also reduced water and ethylene glycol contact angle values for modified hollow fibers surface. Furthermore, the membranes surface energy increased two-fold. The Piranha mixture chemical modification did not change the membranes average pore size and gas permeance values, while air plasma treatment increased pore size 1.5-fold and also 2 order enhanced membranes surface porosity. Since membranes surface porosity increased due to air plasma treatment the modified membranes were used as efficient supports for preparation of high permeance TFC membranes by using poly[1-(trimethylsilyl)-1-propyne] as an example for selective layer fabrication. Full article
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Open AccessArticle
Mammalian Skeletal Muscle Fibres Promote Non-Muscle Stem Cells and Non-Stem Cells to Adopt Myogenic Characteristics
Fibers 2017, 5(1), 5; doi:10.3390/fib5010005 -
Abstract
Skeletal muscle fibres are unique cells in large animals, often composed of thousands of post-mitotic nuclei. Following skeletal muscle damage, resident stem cells, called satellite cells, commit to myogenic differentiation and migrate to carry out repair. Satellite stem cells migrate on muscle fibres
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Skeletal muscle fibres are unique cells in large animals, often composed of thousands of post-mitotic nuclei. Following skeletal muscle damage, resident stem cells, called satellite cells, commit to myogenic differentiation and migrate to carry out repair. Satellite stem cells migrate on muscle fibres through amoeboid movement, which relies on dynamic cell membrane extension and retraction (blebbing). It is not known whether blebbing is due to the intrinsic properties of satellite cells, or induced by features of the myofibre surface. Here, we determined the influence of the muscle fibre matrix on two important features of muscle regeneration: the ability to migrate and to differentiate down a myogenic lineage. We show that the muscle fibre is able to induce amoeboid movement in non-muscle stem cells and non-stem cells. Secondly, we show that prolonged co-culture on myofibres caused amniotic fluid stem cells and breast cancer cells to express MyoD, a key myogenic determinant. Finally, we show that amniotic fluid stem cells co-cultured on myofibres are able to fuse and make myotubes that express Myosin Heavy Chain. Full article
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Open AccessEditorial
Acknowledgement to Reviewers of Fibers in 2016
Fibers 2017, 5(1), 4; doi:10.3390/fib5010004 -
Open AccessReview
Recent Developments in Micro-Structured Fiber Optic Sensors
Fibers 2017, 5(1), 3; doi:10.3390/fib5010003 -
Abstract
Recent developments in fiber-optic sensing have involved booming research in the design and manufacturing of novel micro-structured optical fiber devices. From the conventional tapered fiber architectures to the novel micro-machined devices by advanced laser systems, thousands of micro-structured fiber-optic sensors have been proposed
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Recent developments in fiber-optic sensing have involved booming research in the design and manufacturing of novel micro-structured optical fiber devices. From the conventional tapered fiber architectures to the novel micro-machined devices by advanced laser systems, thousands of micro-structured fiber-optic sensors have been proposed and fabricated for applications in measuring temperature, strain, refractive index (RI), electric current, displacement, bending, acceleration, force, rotation, acoustic, and magnetic field. The renowned and unparalleled merits of sensors-based micro-machined optical fibers including small footprint, light weight, immunity to electromagnetic interferences, durability to harsh environment, capability of remote control, and flexibility of directly embedding into the structured system have placed them in highly demand for practical use in diverse industries. With the rapid advancement in micro-technology, micro-structured fiber sensors have benefitted from the trends of possessing high performance, versatilities and spatial miniaturization. Here, we comprehensively review the recent progress in the micro-structured fiber-optic sensors with a variety of architectures regarding their fabrications, waveguide properties and sensing applications. Full article
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Open AccessArticle
Effect of the Fiber Type and Axial Stiffness of FRCM on the Flexural Strengthening of RC Beams
Fibers 2017, 5(1), 2; doi:10.3390/fib5010002 -
Abstract
The use of externally-bonded fiber-reinforced polymer (FRP) sheets has been successfully used in the repair and strengthening of both the shear and flexural capacities of reinforced concrete (RC) beams, slabs and columns since the 1990s. However, the externally-bonded FRP reinforcements still present many
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The use of externally-bonded fiber-reinforced polymer (FRP) sheets has been successfully used in the repair and strengthening of both the shear and flexural capacities of reinforced concrete (RC) beams, slabs and columns since the 1990s. However, the externally-bonded FRP reinforcements still present many disadvantages, such as poor performance in elevated temperature and fire, lack of permeability and strength degradation when exposed to ultraviolet radiation. To remedy such drawbacks, the fiber-/fabric-reinforced cementitious matrix (FRCM) has been recently introduced. The FRCM system consists of a fiber mesh or grid embedded in a cementitious bonding material. The present research investigates the flexural strengthening of reinforced concrete (RC) beams with FRCM. The experimental testing included eight large-scale concrete beams, 150 mm × 250 mm × 2400 mm, internally reinforced with steel bars and strengthened in flexure with FRCM. The investigated parameters were the internal steel reinforcement ratio and the FRCM systems. Two steel reinforcement ratios of 0.18 and 0.36 of the balanced reinforcement ratio, as well as three FRCM systems using glass, carbon and PBO fibers were investigated. Test results are presented in terms of load-deflection, load-strain and load-crack width relationships. The test results indicated that the PBO FRCM significantly increased the ultimate capacity of the strengthened RC beams with both low and moderate internal reinforcement ratios compared to the glass and carbon FRCM. Full article
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Open AccessArticle
A Fiber Optic Fabry–Perot Cavity Sensor for the Probing of Oily Samples
Fibers 2017, 5(1), 1; doi:10.3390/fib5010001 -
Abstract
A micro-optical Fabry–Perot cavity fabricated by non-linear laser lithography on the endface of a standard telecom fiber is tested here as a microsensor for identifying oily liquids. The device operates within the 1550 nm spectral region, while the spectra recorded in reflection mode
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A micro-optical Fabry–Perot cavity fabricated by non-linear laser lithography on the endface of a standard telecom fiber is tested here as a microsensor for identifying oily liquids. The device operates within the 1550 nm spectral region, while the spectra recorded in reflection mode correlate to the refractive index of the oily liquids used, as well as, to the diffusion dynamics in the time domain of the oily samples inside the porous photo-polymerized sensing head. The operation of the microresonator sensing probe is explained by using a three-layer Fabry–Perot model and basic diffusion physics to estimate diffusivities for three series of refractive index matching oils with different chemical compositions that had been used in those experiments. The distinct spectro-temporal response of this sensing probe to the different oil samples is demonstrated and discussed. Full article
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Open AccessArticle
Performance of Strengthened Non-Uniformly Corroded Reinforced SCC-RAP Members
Fibers 2016, 4(4), 30; doi:10.3390/fib4040030 -
Abstract
This research examines the performance of strengthened non-uniformly corroded reinforced self-consolidating concrete (SCC) members. This paper focuses on three aspects of concrete including corrosion, concrete cover loss, and repair technique. Up to a 50% corrosion level is considered in this study. Corrosion was
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This research examines the performance of strengthened non-uniformly corroded reinforced self-consolidating concrete (SCC) members. This paper focuses on three aspects of concrete including corrosion, concrete cover loss, and repair technique. Up to a 50% corrosion level is considered in this study. Corrosion was experimentally induced and was simulated in other cases. Twenty-six reinforced concrete (RC) members with various corrosion levels or simulated corrosion levels were constructed and investigated. The beams with corrosion problems including those that had experimentally induced corrosion or simulated corrosion, with or without concrete cover, were repaired using carbon fiber reinforced polymer (CFRP) sheets and U-wraps. Two line loads were applied to all of the non-repaired and repaired beams constructed in this study until failure. It was found that it is conservative to model the actual corrosion by simulating the equivalent area of steel reinforcing for up to a 20% level of corrosion. For corrosion levels over 20%, the simulated corrosion over predicts the load capacity of the actual corrosion cases. When the concrete cover was lost and for a corrosion level larger than 10%, the repaired beam did not reach similar performance to that of a repaired beam with a concrete cover that was still intact. It appears that using two layers of CFRP sheet did not improve the load capacity further, but rather improved the ductility of the deteriorated RC member. Full article
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Open AccessArticle
Uncertainty Analysis of the Temperature–Resistance Relationship of Temperature Sensing Fabric
Fibers 2016, 4(4), 29; doi:10.3390/fib4040029 -
Abstract
This paper reports the uncertainty analysis of the temperature–resistance (TR) data of the newly developed temperature sensing fabric (TSF), which is a double-layer knitted structure fabricated on an electronic flat-bed knitting machine, made of polyester as a basal yarn, and embedded with fine
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This paper reports the uncertainty analysis of the temperature–resistance (TR) data of the newly developed temperature sensing fabric (TSF), which is a double-layer knitted structure fabricated on an electronic flat-bed knitting machine, made of polyester as a basal yarn, and embedded with fine metallic wire as sensing element. The measurement principle of the TSF is identical to temperature resistance detector (RTD); that is, change in resistance due to change in temperature. The regression uncertainty (uncertainty within repeats) and repeatability uncertainty (uncertainty among repeats) were estimated by analysing more than 300 TR experimental repeats of 50 TSF samples. The experiments were performed under dynamic heating and cooling environments on a purpose-built test rig within the temperature range of 20–50 °C. The continuous experimental data was recorded through LabVIEW-based graphical user interface. The result showed that temperature and resistance values were not only repeatable but reproducible, with only minor variations. The regression uncertainty was found to be less than ±0.3 °C; the TSF sample made of Ni and W wires showed regression uncertainty of <±0.13 °C in comparison to Cu-based TSF samples (>±0.18 °C). The cooling TR data showed considerably reduced values (±0.07 °C) of uncertainty in comparison with the heating TR data (±0.24 °C). The repeatability uncertainty was found to be less than ±0.5 °C. By increasing the number of samples and repeats, the uncertainties may be reduced further. The TSF could be used for continuous measurement of the temperature profile on the surface of the human body. Full article
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