text: Fibers http://www.mdpi.com/journal/fibers Latest open access articles published in Fibers at http://www.mdpi.com/journal/fibers http://www.mdpi.com/2079-6439/5/2/23 A review on the recent progress in modeling and fabrication of medium infrared (Mid-IR) fiber lasers is reported. The main objective is to illustrate some recent examples of continuous wave optical sources at wavelengths longer than those commonly employed in telecom applications and allowing high beam quality. A small number of Mid-IR lasers, among the large variety of schemes, glasses, dopants and pumping schemes reported in literature, is selected on the basis of their slope efficiency and threshold pump power. In particular, tellurite, fluoride and chalcogenide fiber lasers are considered. More details are given with reference to the novel pumping schemes. Fibers 2017-06-15 5 2 Review 10.3390/fib5020023 23 2079-6439 2017-06-15 doi: 10.3390/fib5020023 Mario Falconi Dario Laneve Francesco Prudenzano http://www.mdpi.com/2079-6439/5/2/22 In this work, palladium (Pd) nanoparticles were blended into a solution of a sacrificial polymer and an aluminum sol gel precursor to form alumina fibers containing the palladium particles. The polymer solution was electrospun into template submicron fibers. These fibers were calcined at temperatures between 650 °C and 1150 °C to remove the polymer and oxidize the aluminum. The internal crystalline morphologies of the calcined fibers transformed with change in the calcination temperature. The calcined fibers were formed into fibrous mats and further tested for their catalytic performances. The Pd particles had a size ranging from 5–20 nm and appeared randomly distributed within and near the surfaces of the alumina fibers. The final metal loading of all Pd/Al2O3 samples ranged from 4.7 wt % to 5.1 wt %. As calcination temperature increased the alumina crystal structure changed from amorphous at 650 °C to alpha crystal structure at 1150 °C. With the increase of calcination temperature, the average fiber diameters and specific surface areas decreased. The catalyst supported fiber media had good conversion of NO and CO gases. Higher calcination temperatures led to higher reaction temperatures from 250 to about 450 °C for total conversion, indicating the effective reactivity of the fiber-supported catalysts decreased with increase in calcination temperature. The fibers formed at the 650 °C calcination temperature had the highest reaction activity. Fibers 2017-06-08 5 2 Article 10.3390/fib5020022 22 2079-6439 2017-06-08 doi: 10.3390/fib5020022 Hyeon Shin Ahmed Abutaleb Dinesh Lolla George Chase http://www.mdpi.com/2079-6439/5/2/21 Actively Q-switched laser operation of a narrow linewidth compact fiber laser based on an Er–Yb double-clad fiber is presented. The laser linewidth as a function of the repetition rate and the Q-switched pulses characteristics for different pump powers are experimentally analyzed. Stable Q-switched laser operation with spectral laser linewidth of 73 pm in a repetition rate range from 90 to 270 kHz is obtained. The minimum pulse duration of 178 ns, maximum peak power of 30.5 W, and maximum pulse energy of 5.4 µJ are observed. The maximum average power reached is 1.1 W. Fibers 2017-06-03 5 2 Article 10.3390/fib5020021 21 2079-6439 2017-06-03 doi: 10.3390/fib5020021 Berenice Posada-Ramírez Manuel Durán-Sánchez Ricardo I. Alvarez-Tamayo Jared Alaniz-Baylón Guillermo Salceda-Delgado Evgeny A. Kuzin Baldemar Ibarra-Escamilla http://www.mdpi.com/2079-6439/5/2/20 Botanical and field cotton trash comingled with Upland cotton lint can greatly reduce the marketability and quality of cotton. Trash found comingled with cotton lint during harvesting, ginning, and processing is of interest to the textile community. In the current study attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopic imaging was employed as an analytical technique to analyze cotton trash. Some benefits of this technique were its non-destructive nature and lack of required sample preparation. The technique used in this study, specifically ATR-FTIR spectroscopic chemical imaging, allows for three-dimensional spectral and spatial data to be obtained. In the current study, cotton in mixtures with botanical and field trash types have been identified spectrally and spatially using ATR-FTIR imaging. Botanical trash types (trash derived from the cotton plant) were evaluated and identified independently from cotton, even though both contained cellulose. The field trash types were easily identified from cotton due to their differences in chemical composition. This study can complement current cotton qualitative studies by adding spectral and spatial information to sample analysis. Fibers 2017-05-23 5 2 Article 10.3390/fib5020020 20 2079-6439 2017-05-23 doi: 10.3390/fib5020020 Chanel Fortier Michael Santiago Cintrón James Rodgers Krystal Fontenot Donna Peralta http://www.mdpi.com/2079-6439/5/2/17 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. Fibers 2017-05-16 5 2 Article 10.3390/fib5020017 17 2079-6439 2017-05-16 doi: 10.3390/fib5020017 Matthew Hudspeth Emily Jewell Suzanne Horner James Zheng Weinong Chen http://www.mdpi.com/2079-6439/5/2/18 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. Fibers 2017-05-12 5 2 Article 10.3390/fib5020018 18 2079-6439 2017-05-12 doi: 10.3390/fib5020018 Liang Huang Chang Gao Libo Yan Xiaoxi Li Gao Ma Tianfeng Wang http://www.mdpi.com/2079-6439/5/2/16 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. Fibers 2017-05-01 5 2 Article 10.3390/fib5020016 16 2079-6439 2017-05-01 doi: 10.3390/fib5020016 Ram Neupane Liyanto Eddy Kohei Nagai http://www.mdpi.com/2079-6439/5/2/15 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. Fibers 2017-04-19 5 2 Article 10.3390/fib5020015 15 2079-6439 2017-04-19 doi: 10.3390/fib5020015 Piotr Miluski http://www.mdpi.com/2079-6439/5/2/14 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. Fibers 2017-04-04 5 2 Article 10.3390/fib5020014 14 2079-6439 2017-04-04 doi: 10.3390/fib5020014 Silvia Simone Francesco Galiano Mirko Faccini Marcel Boerrigter Christiane Chaumette Enrico Drioli Alberto Figoli http://www.mdpi.com/2079-6439/5/1/13 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. Fibers 2017-03-21 5 1 Article 10.3390/fib5010013 13 2079-6439 2017-03-21 doi: 10.3390/fib5010013 Tomohiro Maeda Young-Jin Kim Takao Aoyagi Mitsuhiro Ebara http://www.mdpi.com/2079-6439/5/1/11 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. Fibers 2017-03-10 5 1 Review 10.3390/fib5010011 11 2079-6439 2017-03-10 doi: 10.3390/fib5010011 John Ballato Heike Ebendorff-Heidepriem Jiangbo Zhao Laeticia Petit Johann Troles http://www.mdpi.com/2079-6439/5/1/12 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. Fibers 2017-03-04 5 1 Article 10.3390/fib5010012 12 2079-6439 2017-03-04 doi: 10.3390/fib5010012 Canio Hoffarth Bilal Khaled Loukham Shyamsunder Subramaniam Rajan Robert Goldberg Kelly Carney Paul DuBois Gunther Blankenhorn http://www.mdpi.com/2079-6439/5/1/8 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. Fibers 2017-03-02 5 1 Article 10.3390/fib5010008 8 2079-6439 2017-03-02 doi: 10.3390/fib5010008 Stuart Phoenix Ulrich Heisserer Harm van der Werff Marjolein van der Jagt-Deutekom http://www.mdpi.com/2079-6439/5/1/10 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.[...] Fibers 2017-02-24 5 1 Editorial 10.3390/fib5010010 10 2079-6439 2017-02-24 doi: 10.3390/fib5010010 Edith Mäder http://www.mdpi.com/2079-6439/5/1/9 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. Fibers 2017-02-22 5 1 Article 10.3390/fib5010009 9 2079-6439 2017-02-22 doi: 10.3390/fib5010009 Subramani Sockalingam John Gillespie Michael Keefe http://www.mdpi.com/2079-6439/5/1/7 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. Fibers 2017-02-14 5 1 Article 10.3390/fib5010007 7 2079-6439 2017-02-14 doi: 10.3390/fib5010007 Sanjib Chowdhury Subramani Sockalingam John Gillespie http://www.mdpi.com/2079-6439/5/1/6 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. Fibers 2017-02-13 5 1 Article 10.3390/fib5010006 6 2079-6439 2017-02-13 doi: 10.3390/fib5010006 Ilya Borisov Anna Ovcharova Danila Bakhtin Stepan Bazhenov Alexey Volkov Rustem Ibragimov Rustem Gallyamov Galina Bondarenko Rais Mozhchil Alexandr Bildyukevich Vladimir Volkov http://www.mdpi.com/2079-6439/5/1/5 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. Fibers 2017-01-23 5 1 Article 10.3390/fib5010005 5 2079-6439 2017-01-23 doi: 10.3390/fib5010005 Taryn Morash Henry Collins-Hooper Robert Mitchell Ketan Patel http://www.mdpi.com/2079-6439/5/1/4 n/a Fibers 2017-01-12 5 1 Editorial 10.3390/fib5010004 4 2079-6439 2017-01-12 doi: 10.3390/fib5010004 Fibers Editorial Office http://www.mdpi.com/2079-6439/5/1/3 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. Fibers 2017-01-10 5 1 Review 10.3390/fib5010003 3 2079-6439 2017-01-10 doi: 10.3390/fib5010003 Yanping Xu Ping Lu Liang Chen Xiaoyi Bao http://www.mdpi.com/2079-6439/5/1/2 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. Fibers 2017-01-06 5 1 Article 10.3390/fib5010002 2 2079-6439 2017-01-06 doi: 10.3390/fib5010002 Abdulla Jabr Amr El-Ragaby Faouzi Ghrib http://www.mdpi.com/2079-6439/5/1/1 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. Fibers 2017-01-03 5 1 Article 10.3390/fib5010001 1 2079-6439 2017-01-03 doi: 10.3390/fib5010001 Vasileia Melissinaki Maria Farsari Stavros Pissadakis http://www.mdpi.com/2079-6439/4/4/30 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. Fibers 2016-12-01 4 4 Article 10.3390/fib4040030 30 2079-6439 2016-12-01 doi: 10.3390/fib4040030 Ahmed Abdel-Mohti Hui Shen http://www.mdpi.com/2079-6439/4/4/29 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. Fibers 2016-11-24 4 4 Article 10.3390/fib4040029 29 2079-6439 2016-11-24 doi: 10.3390/fib4040029 Muhammad Husain Ozgur Atalay Asli Atalay Richard Kennon http://www.mdpi.com/2079-6439/4/4/28 Chemical vapor deposition (CVD) is used as a method for the synthesis of carbon nanotubes (CNT) on substrates, most commonly pre-treated by a metal-catalyst. In this work, the capability of basalt fiber surfaces was investigated in order to stimulate catalyst-free growth of carbon nanotubes. We have carried out CVD experiments on unsized, sized, and NaOH-treated basalt fibers modified by growth temperature and a process gas mixture. Subsequently, we investigated the fiber surfaces by SEM, AFM, XPS and carried out single fiber tensile tests. Growth temperatures of 700 °C as well as 800 °C may induce CNT growth, but depending on the basalt fiber surface, the growth process was differently affected. The XPS results suggest surficial iron is not crucial for the CNT growth. We demonstrate that the formation of a corrosion shell is able to support CNT networks. However, our investigations do not expose distinctively the mechanisms by which unsized basalt fibers sometimes induce vertically aligned CNT carpets, isotropically arranged CNTs or no CNT growth. Considering data from the literature and our AFM results, it is assumed that the nano-roughness of surfaces could be a critical parameter for CNT growth. These findings will motivate the design of future experiments to discover the role of surface roughness as well as surface defects on the formation of hierarchical interphases. Fibers 2016-11-23 4 4 Article 10.3390/fib4040028 28 2079-6439 2016-11-23 doi: 10.3390/fib4040028 Theresa Förster Bin Hao Edith Mäder Frank Simon Enrico Wölfel Peng-Cheng Ma http://www.mdpi.com/2079-6439/4/4/27 Infrared imaging is gaining attention as a technique used in the examination of cotton fibers. This type of imaging combines spectral analysis with spatial resolution to create visual images that examine sample composition and distribution. Herein, we report on the use of an infrared instrument equipped with a reflection accessory and an array detector system for the examination of cotton fiber bundles. Cotton vibrational spectra and chemical images were acquired by grouping pixels in the detector array. This technique reduced spectral noise and was employed to visualize cell wall development in cotton fibers bundles. Fourier transform infrared spectra reveal band changes in the C–O bending region that matched previous studies. Imaging studies were quick, relied on small amounts of sample and provided a distribution of the cotton fiber cell wall composition. Thus, imaging of cotton bundles with an infrared detector array has potential for use in cotton fiber examinations. Fibers 2016-11-10 4 4 Article 10.3390/fib4040027 27 2079-6439 2016-11-10 doi: 10.3390/fib4040027 Michael Santiago Cintrón Joseph Montalvo Terri Von Hoven James Rodgers Doug Hinchliffe Crista Madison Gregory Thyssen Linghe Zeng http://www.mdpi.com/2079-6439/4/4/26 Directional water transport fabrics can proactively transfer moisture from the body. They show great potential in making sportswear and summer clothing. While moisture transfer has been previously reported, heat transfer in directional water transport fabrics has been little reported in research literature. In this study, a directional water transport fabric was prepared using an electrospraying technique and its heat transfer properties under dry and wet states were evaluated, and compared with untreated control fabric and the one pre-treated with NaOH. All the fabric samples showed similar heat transfer features in the dry state, and the equilibrium temperature in the dry state was higher than for the wet state. Wetting considerably enhanced the thermal conductivity of the fabrics. Our studies indicate that directional water transport treatment assists in moving water toward one side of the fabric, but has little effect on thermal transfer performance. This study may be useful for development of "smart" textiles for various applications. Fibers 2016-10-14 4 4 Article 10.3390/fib4040026 26 2079-6439 2016-10-14 doi: 10.3390/fib4040026 Chao Zeng Hongxia Wang Hua Zhou Tong Lin http://www.mdpi.com/2079-6439/4/3/25 Since the early 1990s nanofibers, particularly those of a carbonaceous content [1] have received heightened interest due to their advantageous physico-chemical characteristics (e.g., high strength, stiffness, semi-conductor, increased thermal conductivity and one of the highest Young's modulus [2]).[...] Fibers 2016-09-02 4 3 Editorial 10.3390/fib4030025 25 2079-6439 2016-09-02 doi: 10.3390/fib4030025 Alke Petri-Fink Barbara Rothen-Rutishauser Martin Clift http://www.mdpi.com/2079-6439/4/3/24 This paper presents a system that can be used for micro-hole measurement; the system comprises an optical fiber stylus that is 5 µm in diameter. The stylus deflects when it comes into contact with the measured surface; this deflection is measured optically. In this study, the design parameters of the optical system are determined using a ray-tracing method, and a prototype of the probing system is fabricated to verify ray-tracing simulation results; furthermore, the performance of the system is evaluated experimentally. The results show that the design parameters of this system can be determined using ray-tracing; the resolution of the measurement system using this shaft was approximately 3 nm, and the practicality of this system was confirmed by measuring the shape of a micro-hole 100 µm in diameter and 475 µm in depth. Fibers 2016-08-11 4 3 Article 10.3390/fib4030024 24 2079-6439 2016-08-11 doi: 10.3390/fib4030024 Hiroshi Murakami Akio Katsuki Takao Sajima http://www.mdpi.com/2079-6439/4/3/23 In plants there is no universal protocol for RNA extraction, since optimizations are required depending on the species, tissues and developmental stages. Some plants/tissues are rich in secondary metabolites or synthesize thick cell walls, which hinder an efficient RNA extraction. One such example is bast fibres, long extraxylary cells characterized by a thick cellulosic cell wall. Given the economic importance of bast fibres, which are used in the textile sector, as well as in biocomposites as green substitutes of glass fibres, it is desirable to better understand their development from a molecular point of view. This knowledge favours the development of biotechnological strategies aimed at improving specific properties of bast fibres. To be able to perform high-throughput analyses, such as, for instance, transcriptomics of bast fibres, RNA extraction is a crucial and limiting step. We here detail a protocol enabling the rapid extraction of high quality RNA from the bast fibres of textile hemp, Cannabis sativa L., a multi-purpose fibre crop standing in the spotlight of research. Fibers 2016-07-21 4 3 Technical Note 10.3390/fib4030023 23 2079-6439 2016-07-21 doi: 10.3390/fib4030023 Gea Guerriero Lauralie Mangeot-Peter Jean-Francois Hausman Sylvain Legay http://www.mdpi.com/2079-6439/4/3/22 A new type of reinforcement for unidirectional natural fiber composites has been developed, where a paper layer is assembled with a layer of unidirectional flax yarns. The paper layer chemically and mechanically bonds to the loose yarns to maintain their alignment and enables better manipulability of the reinforcement during stacking in the mold. Unfortunately, the paper layer adversely affects the permeability of the whole reinforcement to liquid resin and thus limits the impregnation quality of the final part. In this paper, a technique is adopted to increase the impregnation performance by modifying the architecture of the fibrous network in the paper layer. In particular, a method has been developed to replace a proportion of the Kraft fibers by short flax fibers in the paper layer, in an attempt to open the structure and increase the paper permeability. Permeability measurements show a major improvement in global reinforcement permeability. Basic mechanical properties of resulting composites were also analysed. Results show a slight decrease in modulus and strength when the paper layer is present. This is compensated by an important reduction in variability. Furthermore, increasing the flax proportion in the paper layer limits the loss of mechanical properties, while reducing variability even further. Fibers 2016-07-13 4 3 Article 10.3390/fib4030022 22 2079-6439 2016-07-13 doi: 10.3390/fib4030022 Mohamed Habibi Luc Laperrière Gilbert Lebrun Bruno Chabot http://www.mdpi.com/2079-6439/4/3/21 Cellulose nanocrystals exhibit an interesting combination of mechanical properties and physical characteristics, which make them potentially useful for a wide range of consumer applications. However, as the usage of these bio-based nanofibers increases, a greater understanding of human exposure addressing their potential health issues should be gained. The aim of this perspective is to highlight how knowledge obtained from studying the biological impact of other nanomaterials can provide a basis for future research strategies to deduce the possible human health risks posed by cellulose nanocrystals. Fibers 2016-07-08 4 3 Opinion 10.3390/fib4030021 21 2079-6439 2016-07-08 doi: 10.3390/fib4030021 Sandra Camarero-Espinosa Carola Endes Silvana Mueller Alke Petri-Fink Barbara Rothen-Rutishauser Christoph Weder Martin Clift E. Foster http://www.mdpi.com/2079-6439/4/2/20 Polycaprolactone (PCL) fibers were produced using Forcespinning® (FS). The effects of PCL concentration, solvent mixture, and the spinneret rotational speed on fiber formation were evaluated. The concentration of the polymer in the solvents was a critical determinant of the solution viscosity. Lower PCL concentrations resulted in low solution viscosities with a correspondingly low fiber production rate with many beads. Bead-free fibers with high production rate and uniform fiber diameter distribution were obtained from the optimum PCL concentration (i.e., 12.5 wt%) with tetrahydrofuran (THF) as the solvent. The addition of N, N-dimethylformamide (DMF) to the THF solvent promoted the gradual formation of beads, split fibers, and generally affected the distribution of fiber diameters. The crystallinity of PCL fibers was also affected by the processing conditions, spinning speed, and solvent mixture. Fibers 2016-06-07 4 2 Article 10.3390/fib4020020 20 2079-6439 2016-06-07 doi: 10.3390/fib4020020 Nancy Obregon Victor Agubra Madhab Pokhrel Howard Campos David Flores David De la Garza Yuanbing Mao Javier Macossay Mataz Alcoutlabi http://www.mdpi.com/2079-6439/4/2/19 The purpose of this study is to evaluate, through a nonlinear Finite Element (FE) analysis, the structural behavior of Reinforced Concrete (RC) beams externally strengthened by using Steel Reinforced Grout (SRG) and Steel Reinforced Polymer (SRP) systems. The parameters taken into account were the external strengthening configuration, with or without U-wrap end anchorages, as well as the strengthening materials. The numerical simulations were carried out by using a three-dimensional (3D) FE model. The linear and nonlinear behavior of all materials was modeled by appropriate constitutive laws and the connection between concrete substrate and external reinforcing layer was simulated by means of cohesive surfaces with appropriate bond-slip laws. In order to overcome convergence difficulties, to simulate the quasi-static response of the strengthened RC beams, a dynamic approach was adopted. The numerical results in terms of load-displacement curves, failure modes, and load and strain values at critical stages were validated against some experimental data. As a result, the proposed 3D FE model can be used to predict the structural behavior up to ultimate stage of similar strengthened beams without carrying out experimental tests. Fibers 2016-05-26 4 2 Article 10.3390/fib4020019 19 2079-6439 2016-05-26 doi: 10.3390/fib4020019 Francesco Bencardino Antonio Condello http://www.mdpi.com/2079-6439/4/2/18 The recovery and reuse of glass fibres from manufacturing waste and end-of-life composites in an environmentally-friendly, cost-effective manner is one of the most important challenges facing the thermosetting polymer composites industry. A number of processes for recycling fibres from such materials are available or under development. However, nearly all options deliver recycled glass fibres that are not cost-performance competitive due to the huge drop in strength of recycled glass fibre compared to its original state. A breakthrough in the regeneration of recycled glass fibre performance has the potential to totally transform the economics of recycling such composites. This paper reviews the available knowledge of the thermally-induced strength loss in glass fibres, discusses some of the phenomena that are potentially related and presents the status of research into processes to regenerate the strength and value of such weak recycled glass fibres. Fibers 2016-05-26 4 2 Review 10.3390/fib4020018 18 2079-6439 2016-05-26 doi: 10.3390/fib4020018 James Thomason Peter Jenkins Liu Yang http://www.mdpi.com/2079-6439/4/2/17 The hygrothermal aging of short glass fiber-reinforced polyamide 6 materials (PA6 GF) represents a major problem, especially in thin-walled components, such as in the automotive sector. In this study, therefore, the thickness and the glass fiber content of PA6 GF materials were varied and the materials were exposed to hygrothermal aging. The temperature and relative humidity were selected in the range from −40 °C up to 85 °C, and from 10% up to 85% relative humidity (RH). In the dry-as-molded state, the determined Poisson's ratio of the PA6 GF materials was correlated with the fiber orientation based on computer tomography (MicroCT) data and shows a linear dependence with respect to the fiber orientation along and transverse to the flow direction of the injection molding process. With hygrothermal aging, the value of Poisson's ratio increases in the flow direction in the same way as it decreases perpendicular to the flow direction due to water absorption. Fibers 2016-05-17 4 2 Article 10.3390/fib4020017 17 2079-6439 2016-05-17 doi: 10.3390/fib4020017 Thomas Illing Heinrich Gotzig Marcus Schoßig Christian Bierögel Wolfgang Grellmann http://www.mdpi.com/2079-6439/4/2/16 Flame retardants (FRs) have been around us for decades to increase the chances of survival against fire or flame by limiting its propagation. The FR textiles, irrespective of their atmospheric presence are used in baby clothing, pushchairs, car seats, etc. The overall FR market in Asia, Europe, and the United States in 2007 was around 1.8 million metric tonnes. It is estimated that the worldwide consumption of FRs will reach 2.8 million tonnes in 2018. Unfortunately, a sustainable approach for textile waste, especially in the case of FR textiles, is absent. Incineration and landfill of FR textiles are hindered by various toxic outcomes. To address the need for sustainable methods of discarding FR textiles, the mechanical recycling of cotton curtains was evaluated. Fibers 2016-05-11 4 2 Article 10.3390/fib4020016 16 2079-6439 2016-05-11 doi: 10.3390/fib4020016 Sohail Yasin Nemeshwaree Behary Massimo Curti Giorgio Rovero http://www.mdpi.com/2079-6439/4/2/15 Nowadays, innovative materials are more frequently adopted for strengthening historical constructions and masonry structures. The target of these techniques is to improve the structural efficiency with retrofitting methods while having a reduced aesthetical impact. In particular, the use of basalt fiber together with a cementitious matrix emerges as a new technique. This kind of fiber is obtained by basalt rock without other components, and consequently it could be considered a natural material, compatible with masonry. Another innovative technique for strengthening masonry columns consists of applying steel wires in the correspondence of mortar joints. Both techniques have been recently proposed and some aspects of their structural performances are still open. This paper presents the results of an experimental study on the compressive behavior of clay brick masonry columns reinforced either with Basalt Fiber–Reinforced Cementitious Matrix (BFRCM) or with steel wire collaring. Uniaxial compressive tests were performed on eight retrofitted columns and four control specimens until failure. Two masonry grades were considered by varying the mix used for the mortar. Results are presented and discussed in terms of axial stress-strain curves, failure modes and crack patterns of tested specimens. Comparisons with unreinforced columns show the capability of these techniques in increasing ductility with limited strength enhancements. Fibers 2016-05-10 4 2 Article 10.3390/fib4020015 15 2079-6439 2016-05-10 doi: 10.3390/fib4020015 Marinella Fossetti Giovanni Minafò http://www.mdpi.com/2079-6439/4/2/14 We demonstrate a novel electro-optic swept source for wavenumber-linear interferometric sensing and imaging applications. The electro-optic swept source based on an acousto-optic tunable filter (AOTF) provides high environmental stability and arbitrary drive function sweeping because the electro-optic wavelength selection does not depend on a mechanical moving component to tune the output lasing wavelength. We show improved stability of the suggested electro-optic swept source, compared to a conventional swept source based on a fiber Fabry–Perot tunable filter (FFP-TF). Various types of wavelength sweeping are demonstrated by applying the programmed drive function to the applied radio frequency (RF) of the AOTF. We demonstrated improved image quality of optical coherence tomography (OCT) by using the wavenumber-linear drive function of a simple triangular signal, which has a high wavenumber-linearity with an R-square value of 0.99991. Fibers 2016-04-26 4 2 Article 10.3390/fib4020014 14 2079-6439 2016-04-26 doi: 10.3390/fib4020014 Ga-Hee Han Soon-Woo Cho Nam Park Chang-Seok Kim http://www.mdpi.com/2079-6439/4/2/13 Large residual strain in reinforced concrete structures after a seismic event is a major concern for structural safety and serviceability. Alternative reinforcement materials like fiber-reinforced polymer (FRP) have been widely used to mitigate corrosion problems associated with steel. Low modulus of elasticity and brittle behavior compared to steel has made the use of FRP unsuitable in seismic resistant strictures. A combination of steel-FRP reinforcement configuration can address the problem of corrosion. Therefore, introducing a material that shows strong post elastic behavior without any decay due to corrosion is in demand. Shape memory alloy (SMA), a novel material, is highly corrosion resistive and shows super elastic property. Coupling SMA with FRP or steel in the plastic hinge region allows the structure to undergo large deformations, but regains its original shape upon unloading. In this study, the performance characteristics of four previously tested beam-column joints reinforced with different configurations (steel, SMA/steel, glass fiber reinforced polymer (GFRP) and SMA/FRP) are compared to assess their capacity to endure extreme loading. Experimental results are scrutinized to compare the behavior of these specimens in terms of load-story drift and energy dissipation capacity. SMA/FRP and SMA/Steel couples have been found to be an acceptable approach to reduce residual deformation in beam-column joints with adequate energy dissipation capacity. However, SMA/FRP is superior to SMA/Steel concerning to the corrosion issue in steel. Fibers 2016-04-12 4 2 Article 10.3390/fib4020013 13 2079-6439 2016-04-12 doi: 10.3390/fib4020013 Md Kabir M. Alam Aly Said Achraf Ayad http://www.mdpi.com/2079-6439/4/2/12 Polymerization of aniline in the presence of spider silk produces a natural fiber-based conducting polymer wire. We observed the fiber structure with polarizing optical microscopy and scanning electron microscopy. This spider-silk/PANI, a biosynthetic composite, could be the basis for organic high-performance conducting wire. Fibers 2016-03-31 4 2 Communication 10.3390/fib4020012 12 2079-6439 2016-03-31 doi: 10.3390/fib4020012 Hiromasa Goto Ryosuke Kikuchi Aohan Wang http://www.mdpi.com/2079-6439/4/1/11 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. Fibers 2016-03-15 4 1 Article 10.3390/fib4010011 11 2079-6439 2016-03-15 doi: 10.3390/fib4010011 Henrik Funke Sandra Gelbrich Lothar Kroll http://www.mdpi.com/2079-6439/4/1/10 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. Fibers 2016-02-19 4 1 Article 10.3390/fib4010010 10 2079-6439 2016-02-19 doi: 10.3390/fib4010010 Bipin Kumar Jinlian Hu Ning Pan http://www.mdpi.com/2079-6439/4/1/9 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. Fibers 2016-02-15 4 1 Article 10.3390/fib4010009 9 2079-6439 2016-02-15 doi: 10.3390/fib4010009 William Curtin Pedro Arias-Monje Charliean Dominguez Jonathan Phillips Claudia Luhrs http://www.mdpi.com/2079-6439/4/1/8 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. Fibers 2016-02-06 4 1 Article 10.3390/fib4010008 8 2079-6439 2016-02-06 doi: 10.3390/fib4010008 Ahmed Al-Rahmani Hayder Rasheed http://www.mdpi.com/2079-6439/4/1/7 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. Fibers 2016-02-05 4 1 Article 10.3390/fib4010007 7 2079-6439 2016-02-05 doi: 10.3390/fib4010007 Lluís Gil Ernest Bernat-Masó Francisco Cañavate http://www.mdpi.com/2079-6439/4/1/6 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. Fibers 2016-02-02 4 1 Article 10.3390/fib4010006 6 2079-6439 2016-02-02 doi: 10.3390/fib4010006 Ahmed Ghazy Mohamed Bassuoni Eugene Maguire Mark O'Loan http://www.mdpi.com/2079-6439/4/1/5 The editors of Fibers would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2015. [...] Fibers 2016-01-28 4 1 Editorial 10.3390/fib4010005 5 2079-6439 2016-01-28 doi: 10.3390/fib4010005 Fibers Editorial Office http://www.mdpi.com/2079-6439/4/1/4 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. Fibers 2016-01-27 4 1 Article 10.3390/fib4010004 4 2079-6439 2016-01-27 doi: 10.3390/fib4010004 Farshad Hedayati Dezfuli M. Alam http://www.mdpi.com/2079-6439/4/1/3 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. Fibers 2016-01-22 4 1 Article 10.3390/fib4010003 3 2079-6439 2016-01-22 doi: 10.3390/fib4010003 Ahmed Abdel-Mohti Hui Shen http://www.mdpi.com/2079-6439/4/1/2 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. Fibers 2016-01-20 4 1 Article 10.3390/fib4010002 2 2079-6439 2016-01-20 doi: 10.3390/fib4010002 Thitirat Chaochai Yusuke Imai Tetsuya Furuike Hiroshi Tamura http://www.mdpi.com/2079-6439/4/1/1 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. Fibers 2016-01-08 4 1 Article 10.3390/fib4010001 1 2079-6439 2016-01-08 doi: 10.3390/fib4010001 Richard Petersen http://www.mdpi.com/2079-6439/3/4/575 This research presents a preliminary study on finding predictable methods of controlling the self-folding behaviors of weft knit textiles for use in the development of smart textiles and garment devices, such as those with shape memory, auxetic behavior or transformation abilities. In this work, Shima Seiki SDS-One Apex computer-aided knitting technology, Shima Seiki industrial knitting machines, and the study of paper origami tessellation patterns were used as tools to understand and predict the self-folding abilities of weft knit textiles. A wide range of self-folding weft knit structures was produced, and relationships between the angles and ratios of the knit and purl stitch types were determined. Mechanical testing was used as a means to characterize differences produced by stitch patterns, and to further understand the relationships between angles and folding abilities. By defining a formulaic method for predicting the nature of the folds that occur due to stitch architecture patterns, we can better design self-folding fabrics for smart textile applications. Fibers 2015-12-15 3 4 Article 10.3390/fib3040575 575 587 2079-6439 2015-12-15 doi: 10.3390/fib3040575 Chelsea Knittel Diana Nicholas Reva Street Caroline Schauer Genevieve Dion http://www.mdpi.com/2079-6439/3/4/560 In this work, multifilament, continuous polyacrylonitrile (PAN) fiber tow was solution spun mimicking industrial processing at the small pilot scale (0.5 k tow), while carefully altering the composition of the coagulation bath, in order to determine the effect on the resulting fiber shape, density, orientation, and tensile properties at varying points in the spinning process. Novel here are the abnormally high coagulation bath solvent compositions investigated, which surpass those often reported in the literature. In addition, the coagulation bath was maintained at a slightly chilled temperature, contrary to reported methods to produce round fibers. Further, by altering the composition of the bath in a step-wise fashion during a single spinning run, variations in all other process parameters were minimized. We found that with increasing solvent composition in the coagulation bath, the fibers not only became round in cross section, but also became smaller in diameter, which persisted down the spin line. With this decrease in diameter, all else equal, came an accompanying increase in apparent fiber density via a reduction in microvoid content. In addition, molecular orientation and tensile properties also increased. Therefore, it was found that inadequate understanding of the coagulation bath effects, and spinning at low coagulation bath solvent compositions, can hinder the ability of the fiber to reach optimum properties. Fibers 2015-12-15 3 4 Article 10.3390/fib3040560 560 574 2079-6439 2015-12-15 doi: 10.3390/fib3040560 E. Morris Matthew Weisenberger Gregory Rice http://www.mdpi.com/2079-6439/3/4/539 This research program is intended to verify the influence of using distributed external U-wrap CFRP anchorage to shift the failure mode from overall debonding to sectional flexural failure for concrete beams externally bonded with CFRP sheets. Premature cover delamination and FRP debonding are predominant failure modes in FRP flexural strengthening that may be delayed or prevented by using FRP anchorage. The present experimental study aims to comparatively prove that proper anchorage of flexural strengthening is anticipated to yield a classical flexural failure by FRP rupture or concrete crushing. Once the cohesion of concrete and/or the adhesion with the FRP is exhausted, the U-wraps are engaged to provide anchorage to the flexural FRP through shear friction. Accordingly, three identical T beams and three identical rectangular beams were designed and constructed to examine the capacity improvement by preventing premature debonding failure. The first specimen in each series was tested as a control beam. The second specimen in each series was strengthened using five layers of flexural CFRP in order to admit a debonding failure. The third specimen in each series was strengthened with the same five layers of flexural CFRP plus additional transverse CFRP U-wraps. This study proved that it is possible to quantify the higher flexural capacity of CFRP strengthened beams using external anchorage. Fibers 2015-12-14 3 4 Article 10.3390/fib3040539 539 559 2079-6439 2015-12-14 doi: 10.3390/fib3040539 Hayder Rasheed Brandon Decker Asad Esmaeily Robert Peterman Hani Melhem http://www.mdpi.com/2079-6439/3/4/523 The influence of solid-state drawing on the morphology of melt-spun poly(l-lactic acid) (PLLA) tapes, and the accompanying changes in mechanical and degradation behaviour have been studied. Mechanical properties are found to be strongly dependent on both applied draw ratio and drawing temperature. Moduli of these highly oriented tapes are significantly increased compared to as-extruded tapes at both ambient and elevated temperatures. Interestingly, drawing leads to a significant increase in elongation to break (~3 times) and toughness (~13 times) compared to as-extruded tapes. Structural and morphological characterization indicates strain-induced crystallization as well as an increase in orientation of the crystalline phase at small strains. Upon further stretching, an "overdrawing" regime is observed, with decreased crystalline orientation due to the breakage of existing crystals. For fixed draw ratios, a significant increase in Young's modulus and tensile strength is observed with increasing drawing temperature, due to a higher crystallinity and orientation obtained for tapes drawn at higher temperatures. FT-IR results indicate no crystal transformation after drawing, with the α-form being observed in all tapes. Hydrolytic degradability of PLLA was significantly reduced by solid-state drawing. Fibers 2015-12-01 3 4 Article 10.3390/fib3040523 523 538 2079-6439 2015-12-01 doi: 10.3390/fib3040523 Fang Mai Wei Tu Emiliano Bilotti Ton Peijs http://www.mdpi.com/2079-6439/3/4/504 The increase in the use of polyolefin fiber-reinforced concrete (PFRC) is in contrast to the limited amount of published research about its fracture behavior. This study assesses the main mechanical and fracture properties of PFRC by using conventional and self-compacting concrete with various dosages. The results highlight the significant performance of PFRC and revealed that improving its residual strength for small deformations would enhance its use for structural purposes. For that matter, a combination of polyolefin and steel-hooked fibers was used, improving the results and showing synergies between the two types of fibers that could be exploited for infrastructure applications. The significance of this research is, in addition to the characterization of PFRC, the optimum selection and definition of the proportions and characteristics of the types of fibers chosen for the combination. The results proved that, by combining hooked-steel fibers and macro-polyolefin fibers, it is possible to preserve the high-performance fresh properties and obtain a reliable behavior with synergies in the fracture results. The latter provides an efficient use of the materials, as well as a better mechanical behavior in both service and failure states. Fibers 2015-11-26 3 4 Article 10.3390/fib3040504 504 522 2079-6439 2015-11-26 doi: 10.3390/fib3040504 Marcos Alberti Alejandro Enfedaque Jaime Gálvez http://www.mdpi.com/2079-6439/3/4/491 In the construction industry, the use of natural fabrics as a reinforcement for cement-based composites has shown great potential. The use of these sustainable composites to provide strengthening or repair old masonry structures that exhibit structural problems mainly due to a poor tensile strength of the mortar/brick joints is revealed to be a promising area of research. One of the most significant load conditions affecting the mechanical response of masonry structures occurs when axial bending loads are applied on the resistant cross-section. In this study, three different types of masonry elements were built using clay bricks and a lime-based mortar. After 28 days, the samples were subjected to concentric and eccentric compressive loads. In order to produce significant bending effects, the compressive loads were applied with large eccentricity, and a sudden failure characterized the behavior of the unreinforced masonry (URM) elements. The tested masonry specimens were repaired using fabric-reinforced cementitious matrix (FRCM) composites produced using bi-directional flax and polyparaphenylene benzobisoxazole (PBO) fabrics. The mechanical behavior of the URM and repaired samples was compared in terms of load-displacement and moment-curvature responses. Furthermore, the results achieved using flax-FRCM composites were compared with those of using PBO-FRCM composites. Fibers 2015-11-06 3 4 Article 10.3390/fib3040491 491 503 2079-6439 2015-11-06 doi: 10.3390/fib3040491 Oscar Cevallos Renato Olivito Rosamaria Codispoti http://www.mdpi.com/2079-6439/3/4/478 In this paper we investigate a potential new treatment option for basal cell carcinoma using electrospun polymer nanofibers. Poly(ε-caprolactone) fibers incorporated with the anti-cancer drug imiquimod were successfully produced for the first time. These fibers were characterized and their diffusion release profile tested in vitro. A range of different electrospinning parameters were investigated in order to determine the most effective approach in optimizing the fibers for future in vivo testing. Characterization showed stable and homogeneous distribution of imiquimod. Although the drug was released faster than what would be needed to replicate the current treatment model, this system would ideally allow for a treatment option which reduces side effects and is more convenient for the patient than the current topical treatment. Fibers 2015-11-06 3 4 Article 10.3390/fib3040478 478 490 2079-6439 2015-11-06 doi: 10.3390/fib3040478 Richard Garrett Eri Niiyama Yohei Kotsuchibashi Koichiro Uto Mitsuhiro Ebara http://www.mdpi.com/2079-6439/3/4/463 The Holter monitor is used to measure an electrocardiogram (ECG) signal while a subject moves. However, the Holter monitor is uncomfortable for the subject. Another method of measuring the ECG signal uses a smart shirt. We developed a smart shirt that has six electrodes on the chest and can measure a detailed ECG, obtained with unipolar precordial leads. The electrodes and wires of the shirt are made of conductive ink that is flexible and stretchable. The smart shirt is stretchable and fits the body well. However, because of the gap between the smart shirt and the body, electrodes V1 and V2 do not touch the body consistently. We developed a conductive foam block that fills this gap. We investigated the characteristics of the conductive foam block, and measured ECG signals using the smart shirt. The electrical resistance of the conductive foam block was reduced by pressure. This characteristic could be utilized to measure the ECG signal because the block was pressed by the body and smart shirt. We could measure the ECG signal using the smart shirt and blocks while the subject walked and could detect peaks of the ECG signal while the subject jogged slowly. Fibers 2015-11-03 3 4 Article 10.3390/fib3040463 463 477 2079-6439 2015-11-03 doi: 10.3390/fib3040463 Yasunori Tada Yusaku Amano Tomonobu Sato Shigeru Saito Masahiro Inoue http://www.mdpi.com/2079-6439/3/4/450 In this work, core–shell electrospinning was employed as a simple method for the fabrication of composite coaxial polymer fibers that became hollow ceramic tubes when calcined at high temperature. The shell polymer solution consisted of polyvinyl pyrollidone (PVP) in ethanol mixed with an aluminum acetate solution to act as a ceramic precursor. The core polymer was recycled polystyrene to act as a sacrificial polymer that burned off during calcination. The resulting fibers were analyzed with X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) to confirm the presence of gamma-phase aluminum oxide when heated at temperatures above 700 °C. The fiber diameter decreased from 987 ± 19 nm to 382 ± 152 nm after the calcination process due to the polymer material being burned off. The wall thickness of these fibers is estimated to be 100 nm. Fibers 2015-10-16 3 4 Article 10.3390/fib3040450 450 462 2079-6439 2015-10-16 doi: 10.3390/fib3040450 Jonathan Rajala Hyeon Shin Dinesh Lolla George Chase http://www.mdpi.com/2079-6439/3/4/432 The behavior of concrete-filled fiber tubes (CFFT) polymers under axial compressive loading was investigated. Unlike the traditional fiber reinforced polymers (FRP) such as carbon, glass, aramid, etc., the FRP tubes in this study were designed using large rupture strains FRP which are made of recycled materials such as plastic bottles; hence, large rupture strain (LRS) FRP composites are environmentally friendly and can be used in the context of green construction. This study performed finite element (FE) analysis using LS-DYNA software to conduct an extensive parametric study on CFFT. The effects of the FRP confinement ratio, the unconfined concrete compressive strength ( ), column size, and column aspect ratio on the behavior of the CFFT under axial compressive loading were investigated during this study. A comparison between the behavior of the CFFTs with LRS-FRP and those with traditional FRP (carbon and glass) with a high range of confinement ratios was conducted as well. A new hybrid FRP system combined with traditional and LRS-FRP is proposed. Generally, the CFFTs with LRS-FRP showed remarkable behavior under axial loading in strength and ultimate strain. Equations to estimate the concrete dilation parameter and dilation angle of the CFFTs with LRS-FRP tubes and hybrid FRP tubes are suggested. Fibers 2015-10-14 3 4 Article 10.3390/fib3040432 432 449 2079-6439 2015-10-14 doi: 10.3390/fib3040432 Omar Abdelkarim Mohamed ElGawady http://www.mdpi.com/2079-6439/3/4/411 A finite element model (FEM) was constructed using specialized three-dimensional (3D) software to investigate the punching shear behavior of interior slab-column connections subjected to a moment-to-shear ratio of 0.15 m. The FEM was then verified against the experimental results of full-scale interior slab-column connections reinforced with glass fiber reinforcement polymer (GFRP) bars previously tested by the authors. The FEM results showed that the constructed model was able to predict the behavior of the slabs with reasonable accuracy. Afterward, the verified model was used to conduct a parametric study to investigate the effects of reinforcement ratio, perimeter-to-depth ratio, and column aspect ratio on the punching shear behavior of such connections. The test results showed that increasing the tested parameters enhanced the overall behavior of the connections in terms of decreasing deflections and reinforcement strain and increasing the ultimate capacity. In addition, the obtained punching shear stresses of the connections were compared to the predictions of the Canadian standard and the American guideline for FRP-reinforced concrete structures. Fibers 2015-10-12 3 4 Article 10.3390/fib3040411 411 431 2079-6439 2015-10-12 doi: 10.3390/fib3040411 Ahmed Gouda Ehab El-Salakawy http://www.mdpi.com/2079-6439/3/4/394 Carbon nanofibers were generated over bimetallic catalysts in an atmospheric pressure chemical vapor deposition (APCVD) reactor. Catalyst compositions of Fe 30 at%, Cu and Ni 30 at% and Cu were mechanically alloyed using high-energy ball milling over durations of 4, 8, 12, 16, and 20 h. The catalyst powders were then used to produce carbon nanofibers in ethylene and hydrogen (4:1) at temperatures of 500, 550, and 600 °C. The microstructures of the catalysts were characterized as a function of milling time as well as at deposition temperature. The corresponding carbon deposition rates were assessed and are correlated to the microstructural features of each catalyst. The milling process directly determines the performance of each catalyst toward carbon deposition, and both catalysts performed comparably to those made by traditional co-precipitation methods. Considerations in miscible and immiscible nanostructured alloy systems are discussed. Fibers 2015-10-05 3 4 Article 10.3390/fib3040394 394 410 2079-6439 2015-10-05 doi: 10.3390/fib3040394 Laura Guevara Crystal Wanner Roger Welsh Mark Atwater http://www.mdpi.com/2079-6439/3/4/380 Novel chitosan (CS)-coated poly(l-lactic acid) (PLA) fibers (CS–PLA) were prepared by reaction of an alkali and CS under heat treatment without a chemical binder. These treatments induced hydrolysis on the PLA surface, formation of ionic bonds between the carboxyl groups of the PLA surface and the amino groups of CS, and dehydration between the carboxyls and amines. The prepared fibers were characterized by scanning electron microscopy and mechanical strength tests. The presence of CS on the fiber surface was observed by the visual test of CS–PLA with amido black 10B and confirmed by the amine ratio obtained by X-ray photoelectron spectroscopy. The coating thickness of CS on the surface of the PLA fibers was approximately 28 nm, as determined from calculations based on the results of Kjeldahl nitrogen analysis and elemental analysis. The degradation properties of CS–PLA were also investigated. These properties were apparently enhanced by hydrophilicity resulting from the CS-coating treatment. Furthermore, braided ropes prepared using CS–PLA became tight with increasing number of core ropes. Results indicate that the objective tensile strength and flexibility of the braided rope could be controlled by adjusting the number of core fibers. Fibers 2015-10-01 3 4 Article 10.3390/fib3040380 380 393 2079-6439 2015-10-01 doi: 10.3390/fib3040380 Tetsuya Furuike Hideaki Nagahama Thitirat Chaochai Hiroshi Tamura http://www.mdpi.com/2079-6439/3/3/373 Polyethylene has great potential as an alternative material for carbon fiber production. Polyethylene can be processed in the economic melt spinning process. These precursors are prepared for the subsequent process step of carbonization by using chemical stabilization (sulphonation). The strategy is to adjust these precursor properties by the melt spinning process, thus resulting in a precursor, which can be stabilized sufficiently by sulphonation. The objective is to find the correlation between precursor properties and the results of the sulphonation. In this paper, the chemical stabilization is described and the results of the chemical stabilization are discussed. The novelty in this paper is that the results of the sulphonation are brought in correlation with the precursor properties. It can be shown that the filament diameter and the polymer structure (e.g., the crystallinity) of the precursor have an influence on the sulphonation process. Fibers 2015-09-23 3 3 Article 10.3390/fib3030373 373 379 2079-6439 2015-09-23 doi: 10.3390/fib3030373 Gisa Wortberg Andreas De Palmenaer Markus Beckers Gunnar Seide Thomas Gries http://www.mdpi.com/2079-6439/3/3/348 Hydrolytic degradation in media having a continuous variation of pH from 2 to 12 was studied for a copolymer having two polyglycolide hard blocks and a middle soft segment constituted by glycolide, trimethylene carbonate, and ɛ-caprolactone units. The last units were susceptible to cross-linking reactions by γ irradiation that led to an increase of the molecular weight of the sample. Nevertheless, the susceptibility to hydrolytic degradation was enhanced with respect to non-irradiated samples and consequently such samples were selected to analyze the degradation process through weight loss measurements and the evaluation of changes on molecular weight, morphology, and SAXS patterns. Results reflected the different hydrolytic mechanisms that took place in acid and basic media and the different solubilization of the degradation products. Thus, degradation was faster and solubilization higher in the basic media. In this case, fibers showed a high surface erosion and the formation of both longitudinal and deep circumferential cracks that contrasted with the peeling process detected at intermediate pHs (from 6 to 8) and the absence of longitudinal cracks at low pHs. SAXS measurements indicated that degradation was initiated through the hydrolysis of the irregular molecular folds placed on the amorphous interlamellar domains but also affected lamellar crystals at the last stages. Subsequent heating processes performed with degraded samples were fundamental to reveal the changes in microstructure that occurred during degradation and even the initial lamellar arrangement. In particular, the presence of interfibrillar domains and the disposition of lamellar domains at different levels along the fiber axis for a determined cross-section were evidenced. Fibers 2015-09-15 3 3 Article 10.3390/fib3030348 348 372 2079-6439 2015-09-15 doi: 10.3390/fib3030348 Yolanda Márquez Juan Martínez Pau Turon Lourdes Franco Jordi Puiggalí http://www.mdpi.com/2079-6439/3/3/338 Surface-initiated graft atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) from self-assembled chitin nanofibers (CNFs) was performed under dispersion conditions. Self-assembled CNFs were initially prepared by regeneration from a chitin ion gel with 1-allyl-3-methylimidazolium bromide using methanol; the product was then converted into the chitin nanofiber macroinitiator by reaction with α-bromoisobutyryl bromide in a dispersion containing N,N-dimethylformamide. Surface-initiated graft ATRP of MMA from the initiating sites on the CNFs was subsequently carried out under dispersion conditions, followed by filtration to obtain the CNF-graft-polyMMA film. Analysis of the product confirmed the occurrence of the graft ATRP on the surface of the CNFs. Fibers 2015-08-27 3 3 Article 10.3390/fib3030338 338 347 2079-6439 2015-08-27 doi: 10.3390/fib3030338 Ryo Endo Kazuya Yamamoto Jun-ichi Kadokawa http://www.mdpi.com/2079-6439/3/3/323 This article describes aspects within an experimental program aimed at improving the structural performance of cracked solid fir-wood beams repaired with Basalt Fiber Reinforced Polymer (BFRP) spikes. Fir wood is characterized by its low density, low compression strength, and high level of defects, and it is likely to distort when dried and tends to fail under tension due to the presence of cracks, knots, or grain deviation. The proposed repair technique consists of the insertion of BFRP spikes into timber beams to restore the continuity of cracked sections. The experimental efforts deal with the evaluation of the bending strength and deformation properties of 24 timber beams. An artificially simulated cracking was produced by cutting the wood beams in half or notching. The obtained results for the repaired beams were compared with those of solid undamaged and damaged beams, and increases of beam capacity, bending strength and of modulus of elasticity, and analysis of failure modes was discussed. For notched beams, the application of the BFRP spikes was able to restore the original bending capacity of undamaged beams, while only a small part of the original capacity was recovered for beams that were cut in half. Fibers 2015-08-05 3 3 Article 10.3390/fib3030323 323 337 2079-6439 2015-08-05 doi: 10.3390/fib3030323 Luca Righetti Marco Corradi Antonio Borri http://www.mdpi.com/2079-6439/3/3/309 In this work, a supercritical carbon dioxide assembly was successfully constructed for dyeing Nylon6 fabric. Primary experiments were carried out to confirm the possibility of bringing the dyeing up to factory scale. A series of disperse azo dyes with potential antibacterial activity were applied to dye the fabric under our study in supercritical carbon dioxide (scCO2). The factors affecting the dyeing conditions (i.e., dye concentration, time, temperature and pressure) and functional properties were discussed and compared with those in aqueous dyeing. The comparison revealed that elimination of auxiliary chemicals such as salt, carrier or dispersing agent has no diverse effect on dyeing. The color strength of the dyed fabric evaluated by using K/S measurements increased by increasing dye concentration from 2% to 6% owf. (on weight of fabric). The nylon6 fabrics dyed in supercritical carbon dioxide have good fastness properties, and especially light fastness compared with conventional exhaustion dyeing. Antibacterial activity of the dyed samples under supercritical conditions was evaluated and the results showed excellent antibacterial efficiency. Fibers 2015-08-04 3 3 Article 10.3390/fib3030309 309 322 2079-6439 2015-08-04 doi: 10.3390/fib3030309 Tarek Elmaaty Eman El-Aziz Jaehuyk Ma Fathy El-Taweel Satoko Okubayashi http://www.mdpi.com/2079-6439/3/3/296 Controlled release drug delivery systems enable the sustained release of bioactive molecules, and increase bioavailability over an extended length of time. Biocompatible and biodegradable materials such as polycaprolactone (PCL) nanofibers and alginate hydrogel play a significant role in designing controlled release systems. Prolonged release of bioactive molecules is observed when these polymer materials are used as matrices independently. However, there has not been a report in the literature that shows how different molecules are released at various rates over time. The goal of this study is to demonstrate a novel drug delivery system that has a property of releasing designated drugs at various rates over a defined length of time. We fabricated multilayer nanofiber-hydrogel meshes using electrospun PCL nanofiber and alginate hydrogel, and evaluated their controlled release properties. The multilayer meshes are composed of sandwiched layers of alternating PCL nanofibers and alginate hydrogel. Adenosine triphosphate (ATP), encapsulated in the designated hydrogel layers, is used as a mock drug for the release study. The exposed top layer of the meshes demonstrates a dramatically higher burst release and shorter release time compared to the deeper layers. Such properties of the different layers within the meshes can be employed to achieve the release of multiple drugs at different rates over a specified length of time. Fibers 2015-07-17 3 3 Article 10.3390/fib3030296 296 308 2079-6439 2015-07-17 doi: 10.3390/fib3030296 Rigumula Wu Rohina Niamat Brett Sansbury Mandula Borjigin http://www.mdpi.com/2079-6439/3/3/265 Advances in tissue engineering have enabled the ability to design and fabricate biomaterials at the nanoscale that can actively mimic the natural cellular environment of host tissue. Of all tissues, cartilage remains difficult to regenerate due to its avascular nature. Herein we have developed two new hybrid polypeptide-glycosaminoglycan microfibrous scaffold constructs and compared their abilities to stimulate cell adhesion, proliferation, sulfated proteoglycan synthesis and soluble collagen synthesis when seeded with chondrocytes. Both constructs were designed utilizing self-assembled Fmoc-protected valyl cetylamide nanofibrous templates. The peptide components of the constructs were varied. For Construct I a short segment of dentin sialophosphoprotein followed by Type I collagen were attached to the templates using the layer-by-layer approach. For Construct II, a short peptide segment derived from the integrin subunit of Type II collagen binding protein expressed by chondrocytes was attached to the templates followed by Type II collagen. To both constructs, we then attached the natural polymer N-acetyl glucosamine, chitosan. Subsequently, the glycosaminoglycan chondroitin sulfate was then attached as the final layer. The scaffolds were characterized by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), atomic force microscopy and scanning electron microscopy. In vitro culture studies were carried out in the presence of chondrocyte cells for both scaffolds and growth morphology was determined through optical microscopy and scanning electron microscopy taken at different magnifications at various days of culture. Cell proliferation studies indicated that while both constructs were biocompatible and supported the growth and adhesion of chondrocytes, Construct II stimulated cell adhesion at higher rates and resulted in the formation of three dimensional cell-scaffold matrices within 24 h. Proteoglycan synthesis, a hallmark of chondrocyte cell differentiation, was also higher for Construct II compared to Construct I. Soluble collagen synthesis was also found to be higher for Construct II. The results of the above studies suggest that scaffolds designed from Construct II be superior for potential applications in cartilage tissue regeneration. The peptide components of the constructs play an important role not only in the mechanical properties in developing the scaffolds but also control cell adhesion, collagen synthesis and proteoglycan synthesis capabilities. Fibers 2015-07-17 3 3 Article 10.3390/fib3030265 265 295 2079-6439 2015-07-17 doi: 10.3390/fib3030265 Steven Romanelli Grant Knoll Anthony Santora Alexandra Brown Ipsita Banerjee http://www.mdpi.com/2079-6439/3/3/253 The composition of the extracellular matrix (ECM) of skeletal muscle fibers is a unique environment that supports the regenerative capacity of satellite cells; the resident stem cell population. The impact of environment has great bearing on key properties permitting satellite cells to carry out tissue repair. In this study, we have investigated the influence of the ECM and glycolytic metabolism on satellite cell emergence and migration—two early processes required for muscle repair. Our results show that both influence the rate at which satellite cells emerge from the sub-basal lamina position and their rate of migration. These studies highlight the necessity of performing analysis of satellite behavior on their native substrate and will inform on the production of artificial scaffolds intended for medical uses. Fibers 2015-07-16 3 3 Article 10.3390/fib3030253 253 264 2079-6439 2015-07-16 doi: 10.3390/fib3030253 Gaia Butera Henry Collins-Hooper Robert Mitchell Helen Makarenkova Emiliano Lasagna Ketan Patel http://www.mdpi.com/2079-6439/3/3/206 We describe a framework for modeling the writing and erasure of thermally-distributed activated processes that we can specifically apply to UV-induced refractive index change, particularly in fibers. From experimental measurements (isochrons and/or isotherms), this framework allows to find the distribution function of the activation energy by providing only a constant, which can be determined by a simple variable change when a few assumptions are fulfilled. From this modeling, it is possible to know the complete evolution in time of the system. It is also possible to determine the annealing conditions for extending a lifetime. This approach can also be used for other physical quantities, such as photodarkening, stress relaxation, and luminescence decay, provided that it can be described by a distribution function. Fibers 2015-07-15 3 3 Article 10.3390/fib3030206 206 252 2079-6439 2015-07-15 doi: 10.3390/fib3030206 Bertrand Poumellec Matthieu Lancry http://www.mdpi.com/2079-6439/3/3/197 Despite traditional metal-based dental files, such as NiTi being demonstrated effective in root cleaning, the tooth structure is always damaged. Thus, to fulfill the need for a minimally invasive tool for contemporary endodontics and dentistry, the use of polymer fibers might provide a good option, as it is soft, fabricable, and disposable. In this study, two types of nylon fibers with respective average diameters of 206.9 µm (fiber W) and 156.4 µm (fiber B), respectively, were used as dental files, and mounted onto either a reciprocating or a low-speed rotary hand-piece. In vitro, simulated root canal models were colored red using nail varnish, and then cleaned by the fiber files mounted on the hand-pieces. Three parts of the simulated models, i.e., the apical third, the medium third, and the coronal third, were chosen to assess the cleaning the efficiency (CE) of each specimen by calculating the ratio of the cross-sectional area changes, before and after cleansing, using micro-Computer Tomography (CT). A NiTi file with a low-speed hand-piece was used as a control. SEM was used to observe the nylon fiber surfaces before and after the cleansing. Micro-CT results showed that for both the nylon fibers, W and B, an average CE of 82.11% ± 9.68% for the medium third could be achieved, which is statistically higher (p < 0.01) than the coronal third and apical third. The cleansing efficiency was not affected by, the types of fibers, nor the hand-pieces according to student's t-test. Most of the nylon fibers could withstand deformation after the cleansing. To conclude, nylon fiber files have demonstrated a certain cleansing efficiency in simulated root canals, and micro-CT is a promising method to assess CE. Fibers 2015-07-02 3 3 Article 10.3390/fib3030197 197 205 2079-6439 2015-07-02 doi: 10.3390/fib3030197 Shiqian Gao James Tsoi Gary Cheung Jukka Matinlinna http://www.mdpi.com/2079-6439/3/2/184 Production of high strength carbon fibers from bio-derived precursors is of topical interest. Recently, we reported on dry-spinning of a partially acetylated softwood kraft lignin to produce carbon fibers with superior properties, but the thermo-oxidative stabilization step required a long time due to a slow heating rate needed to prevent the fibers from being heated too rapidly and sticking to each other. Here we report a rapid strategy of dual UV-thermoxidative stabilization (crosslinking) of dry-spun lignin fibers that significantly reduces the stabilization time. The fibers undergo reaction close to the surface such that they can be subsequently thermally stabilized at a rapid heating rate without fibers fusing together, which reduces the total stabilization time significantly from 40 to 4 h. Consequently, the glass transition temperature of UV irradiated fibers was about 15 °C higher than that of fibers without UV treatment. Stabilized fibers were successfully carbonized at 1000 °C and resulting carbon fibers displayed a tensile strength of 900 ± 100 MPa, which is amongst the highest reported for carbon fibers derived from softwood lignin-based precursors. These results establish that UV irradiation is a rapid step that can effectively shorten the total stabilization time for production of lignin-derived carbon fibers. Fibers 2015-06-18 3 2 Article 10.3390/fib3020184 184 196 2079-6439 2015-06-18 doi: 10.3390/fib3020184 Meng Zhang Jing Jin Amod Ogale http://www.mdpi.com/2079-6439/3/2/173 Inorganic nano-scale heterostructures have many advantages over hybrid organic-inorganic dye-sensitized solar cells (DSSC or Grätzel cells), including their resistance to photo-bleaching, thermal stability, large specific surface areas, and general robustness. This study presents a first-of-its-kind low-cost all-inorganic lead selenide-anatase titania (PbSe/TiO2) nanotube heterostructure material for photovoltaic applications. Herein, PbSe nanostructures have been co-electrospun within a hollow TiO2 nanotube with high connectivity for highly efficient charge carrier flow and electron-hole pair separation. This material has been characterized by transmission electron microscopy (TEM), electron diffraction, energy dispersive X-ray spectroscopy (EDX) to show the morphology and material composition of the synthesized nanocomposite. Photovoltaic characterization has shown this newly synthesized proof-of-concept material can easily produce a photocurrent under solar illumination, and, with further refinement, could reveal a new direction in photovoltaic materials. Fibers 2015-06-01 3 2 Article 10.3390/fib3020173 173 183 2079-6439 2015-06-01 doi: 10.3390/fib3020173 Evan Wujcik Stephanie Aceto David Heskett Arijit Bose http://www.mdpi.com/2079-6439/3/2/151 Electrospinning of regular poly(ester amide)s (PEAs) constituted by glycolic acid, adipic acid and diamines with five and six carbon atoms has been carried out. Selected PEAs were constituted by natural origin products and could be easily prepared by a polycondensation method that avoids tedious protection and deprotection steps usually required for obtaining polymers with a regular sequence. Nevertheless, the synthesis had some limitations that mainly concerned the final low/moderate molecular weight that could be attained. Therefore, it was considered interesting to evaluate if electrospun scaffolds could still be prepared taking also advantage of the capability of PEAs to establish intermolecular hydrogen bonds. Results indicated that the crucial factor was the control of polymer concentration in the electrospun solution, being necessary that this concentration was higher than 40% (w/v). The PEA with the lowest molecular weight (Mw close to 8000 g/mol) was the most appropriate to obtain electrospun samples with a circular cross-section since higher molecular sized polymers show solvent retention problems derived from the high viscosity of the electrospun solution that rendered ribbon-like morphologies after the impact of fibers into the collector. The studied PEAs were semicrystalline and biodegradable, as demonstrated by calorimetric and degradation studies. Furthermore, the new scaffolds were able to encapsulate drugs with anti-inflammatory and bacteriostatic activities like ketoprofen. The corresponding release and bactericide activity was evaluated in different media and against different bacteria. Finally, biocompatibility was demonstrated using both fibroblast and epithelial cell lines. Fibers 2015-05-12 3 2 Article 10.3390/fib3020151 151 172 2079-6439 2015-05-12 doi: 10.3390/fib3020151 Sara Murase Luís del Valle Jordi Puiggalí http://www.mdpi.com/2079-6439/3/2/134 This paper focuses on the load transfer improvement caused by nanofibers (NF) in carbon fiber reinforced composites. Load transfer is defined as the ability to transfer the mechanical loading between two adjacent fibers through the surrounding matrix. NF action is explored with a finite element model representing two carbon fibers separated by a layer of a NF reinforced matrix. It appears that the role of the NF network is to strengthen the matrix by increasing matrix shear rigidity, and thus to improve the load transfer between the carbon fibers. NF network morphology, defined by NF orientation, NF spatial distribution or NF diameter, governs the NF network efficiency. Fibers 2015-04-29 3 2 Article 10.3390/fib3020134 134 150 2079-6439 2015-04-29 doi: 10.3390/fib3020134 Alexandre Vivet Willy Leclerc Bessem Doudou Jun Chen Christophe Poilâne http://www.mdpi.com/2079-6439/3/2/103 Inorganic Mg2+ and Al3+ containing layered double hydroxide (LDH) particles were synthesised in situ from aqueous solution onto chemical pulp fibers of pine (Pinus sylvestris). High super saturated (hss) solution with sodium carbonate produced LDH particles with an average diameter of 100–200 nm. Nano-size (70 nm) LDH particles were found from fibers external surface and, to a lesser degree, from the S2 cell wall after synthesis via low super saturated (lss) route. The synthesis via slow urea hydrolysis (Uhyd) yielded micron and clay sized LDH (2–5 μm) and enabled efficient fiber densification via mineralization of S2 fiber wall layer as indicated by TEM and compliance analysis. The Uhyd method decreased fiber compliance up to 50%. Reduction in the polymerisation degree of cellulose was observed with capillary viscometry. Thermogravimetric analysis showed that the hybridization with LDH reduced the exothermic heat, indicating, that this material can be incorporated in flame retardant applications. Fiber charge was assessed by Fibers 2015, 3 104 adsorption expermients with methylene blue (MB) and metanil yellow (MY). Synthesis via lss route retained most of the fibres original charge and provided the highest capacity (10 μmol/g) for anionic MY, indicating cationic character of hybrid fibers. Our results suggested that mineralized fibers can be potentially used in advanced applications such as biocomposites and adsorbent materials. Fibers 2015-04-29 3 2 Article 10.3390/fib3020103 103 133 2079-6439 2015-04-29 doi: 10.3390/fib3020103 Carl-Erik Lange Mika Lastusaari Mehedi Reza Seyed Latifi Pasi Kallio Pedro Fardim http://www.mdpi.com/2079-6439/3/2/90 Mixtures of "template" and "adder" proteins self-assemble into large amyloid fibers of varying morphology and modulus. Fibers range from low modulus, rectangular cross-sectioned tapes to high modulus, circular cross-sectioned cylinders. Varying the proteins in the mixture can elicit "in-between" morphologies, such as elliptical cross-sectioned fibers and twisted tapes, both of which have moduli in-between rectangular tapes and cylindrical fibers. Experiments on mixtures of proteins of known amino acid sequence show that control of the large amyloid fiber morphology is dependent on the amount of glutamine repeats or "Q-blocks" relative to hydrophobic side chained amino acids such as alanine, isoleucine, leucine, and valine in the adder protein. Adder proteins with only hydrophobic groups form low modulus rectangular cross-sections and increasing the Q-block content allows excess hydrogen bonding on amide groups that results in twist and higher modulus. The experimental results show that large amyloid fibers of specific shape and modulus can be designed and controlled at the molecular level. Fibers 2015-04-16 3 2 Article 10.3390/fib3020090 90 102 2079-6439 2015-04-16 doi: 10.3390/fib3020090 Devin Ridgley Caitlin Rippner Justin Barone http://www.mdpi.com/2079-6439/3/1/76 Flax fibre bio-epoxy composites have not found many commercial uses in structural applications on account of their lack of cost efficiency and high susceptibility to environmental changes. Non-woven flax mats were subjected to alkali, acetylation, silane and enzymatic treatment, and then combined with untreated unidirectional (UD) flax fabrics to make hybrid flax bio-epoxy composites. Mechanical and environmental resistance (aging) tests were performed on the treated flax fibres. The glass transition temperature was detected at about 75 °C with little effect of treatments. Untreated composites were found to have a tensile strength of 180 MPa while no significant improvement was observed for any of the treatments, which are also not environmentally friendly. The amiopropyltriethoxysilane (APS) composites after Xenon aging, retained the tensile strength of 175 MPa and a modulus of 11.5 GPa, while untreated composites showed 35% reduction in elastic modulus. Fibers 2015-03-19 3 1 Article 10.3390/fib3010076 76 89 2079-6439 2015-03-19 doi: 10.3390/fib3010076 Jinchun Zhu Kirsi Immonen Christophe Avril James Brighton Huijun Zhu Hrushikesh Abhyankar http://www.mdpi.com/2079-6439/3/1/64 The growing environmental problems, the problem of waste disposal and the depletion of non-renewable resources have stimulated the use of green materials compatible with the environment to reduce environmental impacts. Therefore, there is a need to design products by using natural resources. Natural fibers seem to be a good alternative since they are abundantly available and there are a number of possibilities to use all the components of a fiber-yielding crop; one such fiber-yielding plant is Agave Americana. The leaves of this plant yield fibers and all the parts of this plant can be utilized in many applications. The "zero-waste" utilization of the plant would enable its production and processing to be translated into a viable and sustainable industry. Agave Americana fibers are characterized by low density, high tenacity and high moisture absorbency in comparison with other leaf fibers. These fibers are long and biodegradable. Therefore, we can look this fiber as a sustainable resource for manufacturing and technical applications. Detailed discussion is carried out on extraction, characterization and applications of Agave Americana fiber in this paper. Fibers 2015-02-05 3 1 Review 10.3390/fib3010064 64 75 2079-6439 2015-02-05 doi: 10.3390/fib3010064 Ashish Hulle Pradyumkumar Kadole Pooja Katkar http://www.mdpi.com/2079-6439/3/1/41 The use of fiber reinforcement in traditional concrete mixes has been extensively studied and has been slowly finding its regular use in practice. In contrast, opportunities for the use of fibers in masonry applications and structural rehabilitation projects (masonry and concrete structures) have not been as deeply investigated, where the base matrix may be a weaker cementitious mixture. This paper will summarize the findings of the author's research over the past 10 years in these particular applications of fiber reinforced cements (FRC). For masonry, considering both mortar and mortar-unit bond characteristics, a 0.5% volume fraction of micro fibers in type N Portland cement lime mortar appear to be a viable recipe for most masonry joint applications both for clay and concrete units. In general, clay units perform better with high water content fiber reinforced mortar (FRM) while concrete masonry units (CMUs) perform better with drier mixtures, so 130% and 110% flow rates should be targeted, respectively. For earth block masonry applications, fibers' benefits are observed in improving local damage and water pressure resistance. The FRC retrofit technique proposed for the rehabilitation of reinforced concrete two-way slabs has exceeded expectations in terms of capacity increase for a relatively low cost in comparison to the common but expensive fiber reinforced polymer applications. For all of these applications of fiber-reinforced cements, further research with larger data pools would lead to further optimization of fiber type, size, and amount. Fibers 2015-02-04 3 1 Review 10.3390/fib3010041 41 63 2079-6439 2015-02-04 doi: 10.3390/fib3010041 Ece Erdogmus http://www.mdpi.com/2079-6439/3/1/30 The secondary cell wall development of cotton fibers harvested at 18, 20, 24, 28, 32, 36 and 40 days after flowering was examined using attenuated total reflection Fourier transform-infrared (ATR FT-IR) spectroscopy. Spectra of deuterated cotton fibers did not demonstrate significant changes in their O–H stretching band shapes or positions during development. Only a progressive increase in O–H band intensity was observed. Results indicate that the highly crystalline cellulose component produced during secondary cell wall formation maintains the hydrogen bonding network observed for the primary cell wall. Other general changes were observed for the regular ATR spectra. A progressive intensity increase for bands assigned to cellulose Iβ was observed during fiber development, including a marked intensity increase for vibrations at 1002 and 985 cm−1. In contrast, C–O vibrational bands from dominant conformations observed at 1104, 1052, 1028 cm−1 undergo a modest intensity increase during secondary cell wall development. Fibers 2015-01-29 3 1 Article 10.3390/fib3010030 30 40 2079-6439 2015-01-29 doi: 10.3390/fib3010030 Michael Cintrón Doug Hinchliffe http://www.mdpi.com/2079-6439/3/1/13 Glass fiber reinforced polymers (GFRP) have become a preferable material for reinforcing or strengthening reinforced concrete structures due to their corrosion resistance, high strength to weight ratio, and relatively low cost compared with carbon fiber reinforced polymers (CFRP). However, the limited fatigue life of GFRP hinders their use in infrastructure applications. For instance, the low fatigue life of GFRP caused design codes to impose stringent stress limits on GFRP that rendered their use non-economic under significant cyclic loads in bridges. In this paper, we demonstrate that the fatigue life of GFRP can be significantly improved by an order of magnitude by incorporating Multi-Wall Carbon Nanotubes (MWCNTs) during GFRP fabrication. GFRP coupons were fabricated and tested under static tension and cyclic tension with mean fatigue stress equal to 40% of the GFRP tensile strength. Microstructural investigations using scanning electron microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy were used for further investigation of the effect of MWCNTs on the GFRP composite. The experimental results show the 0.5 wt% and the 1.0 wt% MWCNTs were able to improve the fatigue life of GFRP by 1143% and 986%, respectively, compared with neat GFRP. Fibers 2015-01-15 3 1 Article 10.3390/fib3010013 13 29 2079-6439 2015-01-15 doi: 10.3390/fib3010013 Moneeb Genedy Sherif Daghash Eslam Soliman Mahmoud Taha http://www.mdpi.com/2079-6439/3/1/12 The editors of Fibers would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2014:[...] Fibers 2015-01-09 3 1 Editorial 10.3390/fib3010012 12 12 2079-6439 2015-01-09 doi: 10.3390/fib3010012 Fibers Editorial Office http://www.mdpi.com/2079-6439/3/1/1 Wearing comfort of clothing is dependent on air permeability, moisture absorbency and wicking properties of fabric, which are related to the porosity of fabric. In this work, a plug-in is developed using Python script and incorporated in Abaqus/CAE for the prediction of porosity of plain weft knitted fabrics. The Plug-in is able to automatically generate 3D solid and multifilament weft knitted fabric models and accurately determine the porosity of fabrics in two steps. In this work, plain weft knitted fabrics made of monofilament, multifilament and spun yarn made of staple fibers were used to evaluate the effectiveness of the developed plug-in. In the case of staple fiber yarn, intra yarn porosity was considered in the calculation of porosity. The first step is to develop a 3D geometrical model of plain weft knitted fabric and the second step is to calculate the porosity of the fabric by using the geometrical parameter of 3D weft knitted fabric model generated in step one. The predicted porosity of plain weft knitted fabric is extracted in the second step and is displayed in the message area. The predicted results obtained from the plug-in have been compared with the experimental results obtained from previously developed models; they agreed well. Fibers 2014-12-30 3 1 Article 10.3390/fib3010001 1 11 2079-6439 2014-12-30 doi: 10.3390/fib3010001 Muhammad Siddiqui Danmei Sun http://www.mdpi.com/2079-6439/2/4/308 The ion exchange capability of electrospun cellulose acetate (CA) fibers containing zeolite A nanoparticles is reported. Solid and porous CA fibers were used to make a zeolite-embedded filter paper, which was then used to ion exchange Na+ with Cu2+ and Pb2+. The composite Linde Type A (LTA) zeolite CA fibers exchanged 0.39 mmol/g more Pb2+ than LTA nanoparticles in the solid CA fibers. These fibers could provide a simple and effective method for heavy metal ion removal in water. Fibers 2014-12-05 2 4 Article 10.3390/fib2040308 308 317 2079-6439 2014-12-05 doi: 10.3390/fib2040308 Daniel Tran Anne Marti Kenneth Balkus http://www.mdpi.com/2079-6439/2/4/295 Smart multi-walled carbon nanotube (MWCNT)-coated cellulose fibers with a unique sensing ability were manufactured by a simple dip coating process. The formation of electrically-conducting MWCNT networks on cellulose mono- and multi-filament fiber surfaces was confirmed by electrical resistance measurements and visualized by scanning electron microscopy. The interaction between MWCNT networks and cellulose fiber was investigated by Raman spectroscopy. The piezoresistivity of these fibers for strain sensing was investigated. The MWCNT-coated cellulose fibers exhibited a unique linear strain-dependent electrical resistance change up to 18% strain, with good reversibility and repeatability. In addition, the sensing behavior of these fibers to volatile molecules (including vapors of methanol, ethanol, acetone, chloroform and tetrahydrofuran) was investigated. The results revealed a rapid response, high sensitivity and good reproducibility for these chemical vapors. Besides, they showed good selectivity to different vapors. It is suggested that the intrinsic physical and chemical features of cellulose fiber, well-formed MWCNT networks and favorable MWCNT-cellulose interaction caused the unique and excellent sensing ability of the MWCNT-coated cellulose fibers, which have the potential to be used as smart materials. Fibers 2014-11-13 2 4 Article 10.3390/fib2040295 295 307 2079-6439 2014-11-13 doi: 10.3390/fib2040295 Haisong Qi Jianwen Liu Edith Mäder http://www.mdpi.com/2079-6439/2/4/285 Cellulose deposition in developing cotton fibers has been studied previously with analytical techniques, such as Fourier transform infrared spectroscopy (FTIR), High-performance liquid chromatography (HPLC) and Thermogravimetric analysis (TGA). Recent technological developments in instrumentation have made Raman microscopy emerge as an extraordinary analytical tool in biological and plant research. The advantage of using confocal Raman microscopy (CRM) resides in the lateral spatial resolution and in the fact that Raman spectroscopy provides not only chemical composition information, but also structural information. Cross-sections of cotton fibers harvested at different developmental stages were studied with CRM. The Raman bands assigned to cellulose were analyzed. The results of this study indicate that CRM can be used as a tool to study cellulose deposition in cotton fibers and could provide useful information on cellulose deposition during cotton fiber development. Fibers 2014-10-27 2 4 Article 10.3390/fib2040285 285 294 2079-6439 2014-10-27 doi: 10.3390/fib2040285 Luis Cabrales Noureddine Abidi Felicia Manciu http://www.mdpi.com/2079-6439/2/4/275 Hybrid sols of poly (vinyl alcohol) (PVA)/Silicon oxide-titanium oxide (SiO2-TiO2) were prepared with tetraethoxylsilane and tetrabutyl titanate as precursor using Sol-Gel method. PVA/SiO2-TiO2 hybrid fibers were prepared by drawing from the hybrid sols using dip-coating method and aging treatment. The spinnability of hybrid sols was investigated. Spinnable time (t) and spinnable length (l) of hybrid sols increased with either the PVA content or the molar ratio of SiO2 and TiO2. The hybrid fibers were characterized by Fourier transform infrared (FT-IR), Scanning electron microscopy (SEM), X-ray diffraction (XRD), Ultraviolet Visible Spectrometry (UV-Vis) and (Thermo-gravimetric Analysis) TGA. FT-IR results suggested that PVA was linked with (SiO2-TiO2) network by chemical bonds. SEM measurements indicated that when the fibers arrives the maximum spinning length, the diameter of the fibers was about 50 μm, and the whole system was homogeneous. XRD results revealed that the crystallinity of hybrid fibers was decreased distinctly. UV-Vis measurements confirmed that the shielding properties to Ultraviolet (UV) were greatly improved with titania filled in the hybrid fibers. TG measurements suggested that the hybrid fibers show better resistance to heat than pure PVA fibers. Fibers 2014-10-21 2 4 Article 10.3390/fib2040275 275 284 2079-6439 2014-10-21 doi: 10.3390/fib2040275 Haihong Ma Tiejun Shi Qiusheng Song http://www.mdpi.com/2079-6439/2/4/264 Cotton is and has been a large cash crop in the United States and abroad for many years. Part of the widespread interest and utility of this product is due to its attractive chemical and physical properties for use in textiles. The textile industry could benefit from the presentation of a quick, reliable method to classify U.S. from foreign cottons so that the appropriate tariffs can be levied for non-American cottons. In addition, there is some interest in avoiding cotton identity theft. Thus, an accurate and precise instrumental method would be of interest to correctly identify the country of origin of cotton. This study provides an analytical method to identify domestic and foreign cotton fibers using near-infrared (NIR) spectroscopy coupled with principal component analysis (PCA). Samples from American cottons were evaluated along with a representative amount of international samples. The results provide a proof of concept that indicates that PCA analysis can be used to separate the respective domestic and foreign cotton groups. Fibers 2014-09-29 2 4 Article 10.3390/fib2040264 264 274 2079-6439 2014-09-29 doi: 10.3390/fib2040264 Chanel Fortier James Rodgers http://www.mdpi.com/2079-6439/2/3/255 A (1→3)-β-d-Glucan produced by Lactobacillus suebicus CUPV221 strain was investigated by tapping mode atomic force microscopy (TM-AFM), to compare its supramolecular structure and conformation with two commercial polysaccharides: curdlan and scleroglucan. It was found that the β-d-Glucan was a (1→3)(1→2)-β-d-Glucan and at room temperature formed three-dimensional networks by entanglements between strands, as does scleroglucan. However, (1→3)(1→2)-β-d-Glucan strands seemed to be more stiff than those of scleroglucan. It was also observed that curdlan samples deposited from 5 mM NaOH aqueous solution showed supermolecular assemblies, recognized in the literature as micelles, which are controlled by hydrophobic hydration. The (1→3)(1→2)-β-d-Glucan in alkaline aqueous solutions produced different supramolecular structures depending on pH, and at 0.4 M NaOH (pH 13.16), denaturation took place. After neutralizing the alkaline solution with HCl, the formation of short linear, circular, and hairpin structures was observed. Fibers 2014-09-22 2 3 Article 10.3390/fib2030255 255 263 2079-6439 2014-09-22 doi: 10.3390/fib2030255 Ana Puertas Mª Dueñas Cristina Marieta http://www.mdpi.com/2079-6439/2/3/242 The objective of this research was to evaluate the properties of the chemically retted kenaf bast fiber impregnated with the inorganic nanoparticles. High quality kenaf bast fibers were obtained from a chemical retting process. An in situ inorganic nanoparticle impregnation (INI) process was used to introduce the CaCO3 nanoparticles into the retted kenaf bast fibers. It was found that some of the lignin-based components in the retted fibers were further removed during the INI treatment. From the characterization results, the inorganic nanoparticles CaCO3, with different shapes and sizes, appeared at the surface of the impregnated fiber after treatment. Heterogeneous CaCO3 nanoparticle distribution was observed on the INI treated fibers. The CaCO3 contents were different at different locations along the impregnated fiber. The presence of CaCO3 inorganic nanoparticles at the fiber surface increased the root mean square (RMS) surface roughness by 5.8% and decreased the hydrophilic nature of the retted fibers, evidenced by a 59.4% decrease in adhesion force between the fiber and hydrophilic AFM tip. In addition, the impregnation of CaCO3 dramatically increased the Young's modulus of the fiber by 344%. Fibers 2014-08-22 2 3 Article 10.3390/fib2030242 242 254 2079-6439 2014-08-22 doi: 10.3390/fib2030242 Kaiwen Liang Sheldon Shi Ge Wang http://www.mdpi.com/2079-6439/2/3/240 The main distinguishing feature of the fiber is simply that it is a particle where the ratio of length to width ratio is very large. This provides connectivity between two relatively remote areas. Such linkage may confer strength through physical linkage or may relate primarily to information transfer. In the inorganic world, fibers can originate as a result of the process by which the solid material is condensed from the corresponding liquid form. Man-made fibrous materials are essentially polymers of a single or several molecular species repeated many times, or, in the case of metals, chains of elemental atoms. A host of man-made fibers have been developed in the last 50 years. A large range of uses has been found for these products. These include clothing, upholstery, fiber optic cables, filters, insulation, electromagnetic screening, and boat and aircraft construction. [...] Fibers 2014-08-22 2 3 Editorial 10.3390/fib2030240 240 241 2079-6439 2014-08-22 doi: 10.3390/fib2030240 Stephen Bondy http://www.mdpi.com/2079-6439/2/3/221 Nanoscale three-dimensional (3D) scaffolds offer great promise for improved tissue integration and regeneration by their physical and chemical property enhancements. Electrospinning is a versatile bottom-up technique for producing porous 3D nanofibrous scaffolds that could closely mimic the structure of extracellular matrix. Much work has been committed to the development of this process through the years, and the resultant nanostructures have been subjugated to a wide range of applications in the field of bioengineering. In particular, the application of ceramic nanofibres in hard tissue engineering, such as dental and bone regeneration, is of increased research interest. This mini-review provides a brief overview of the bioceramic nanofibre scaffolds fabricated by electrospinning and highlights some of the significant process developments over recent years with their probable future trends and potential applications as biomedical implants. Fibers 2014-08-22 2 3 Review 10.3390/fib2030221 221 239 2079-6439 2014-08-22 doi: 10.3390/fib2030221 Rajkamal Balu Sivakumar Singaravelu Naveen Nagiah http://www.mdpi.com/2079-6439/2/3/211 An investigation of the relationships among fiber linear density, tenacity, and structure is important to help cotton breeders modify varieties for enhanced fiber end-use qualities. This study employed the Stelometer instrument, which is the traditional fiber tenacity reference method and might still be an option as a rapid screening tool because of its low cost and portable attributes. In addition to flat bundle break force and weight variables from a routine Stelometer test, the number of fibers in the bundle were counted manually and the fiber crystallinity (CIIR) was characterized by the previously proposed attenuated total reflection-sampling device based Fourier transform infrared (ATR-FTIR) protocol. Based on the plots of either tenacity vs. linear density or fiber count vs. mass, the fibers were subjectively divided into fine or coarse sets, respectively. Relative to the distinctive increase in fiber tenacity with linear density, there was an unclear trend between the linear density and CIIR for these fibers. Samples with similar linear density were found to increase in tenacity with fiber CIIR. In general, Advanced Fiber Information System (AFIS) fineness increases with fiber linear density. Fibers 2014-07-14 2 3 Article 10.3390/fib2030211 211 220 2079-6439 2014-07-14 doi: 10.3390/fib2030211 Yongliang Liu Devron Thibodeaux James Rodgers http://www.mdpi.com/2079-6439/2/3/187 When nanomaterials enter biological fluids, they are immediately covered by biomolecules, particularly proteins, forming the so-called protein corona. The dynamic nature and complexity of the protein corona can impact upon the biological effects and distribution of nanomaterials with an organism. Therefore, the protein corona is an important factor in determining the biological impact of any nanomaterials. The protein adsorption pattern is determined by various factors, including the bio-fluids' protein composition, the nanomaterials' physicochemical properties, as well as the time and type of exposure. Predominantly, research has focused upon spherical nano-objects, however, due to their ever-increasing potential use within human based applications, and, therefore, heightening and inevitable exposure to the human body, little is known regarding how proteins interact with nanofibers. Therefore, the present review focuses on the current knowledge as to how the geometry of man-made (nano)fibers, carbon nanotubes (in comparison with asbestos fibers), affects their interaction with proteins within biological fluids. Summarizing state-of the art methodologies applied to dissect protein-binding signatures, it is further discussed whether the protein corona composition of fibrous and non-fibrous materials differ, as well as what impact the protein corona has on (nano)fiber uptake, intracellular distribution and their subsequent toxicity. Fibers 2014-06-30 2 3 Review 10.3390/fib2030187 187 210 2079-6439 2014-06-30 doi: 10.3390/fib2030187 Melanie Kucki Jean-Pierre Kaiser Martin Clift Barbara Rothen-Rutishauser Alke Petri-Fink Peter Wick http://www.mdpi.com/2079-6439/2/2/158 Electrospinning is a rapidly growing polymer processing technology as it provides a viable and simple method to create ultra-fine continuous fibers. This paper presents an in-depth review of the mechanical properties of electrospun fibers and particularly focuses on methodologies to generate high strength and high modulus nanofibers. As such, it aims to provide some guidance to future research activities in the area of high performance electrospun fibers. Fibers 2014-04-30 2 2 Review 10.3390/fib2020158 158 186 2079-6439 2014-04-30 doi: 10.3390/fib2020158 Jian Yao Cees Bastiaansen Ton Peijs