Showing papers on "Fiber published in 2011"

A review on the tensile properties of natural fiber reinforced polymer composites

Abstract: This paper is a review on the tensile properties of natural fiber reinforced polymer composites. Natural fibers have recently become attractive to researchers, engineers and scientists as an alternative reinforcement for fiber reinforced polymer (FRP) composites. Due to their low cost, fairly good mechanical properties, high specific strength, non-abrasive, eco-friendly and bio-degradability characteristics, they are exploited as a replacement for the conventional fiber, such as glass, aramid and carbon. The tensile properties of natural fiber reinforce polymers (both thermoplastics and thermosets) are mainly influenced by the interfacial adhesion between the matrix and the fibers. Several chemical modifications are employed to improve the interfacial matrix–fiber bonding resulting in the enhancement of tensile properties of the composites. In general, the tensile strengths of the natural fiber reinforced polymer composites increase with fiber content, up to a maximum or optimum value, the value will then drop. However, the Young’s modulus of the natural fiber reinforced polymer composites increase with increasing fiber loading. Khoathane et al. [1] found that the tensile strength and Young’s modulus of composites reinforced with bleached hemp fibers increased incredibly with increasing fiber loading. Mathematical modelling was also mentioned. It was discovered that the rule of mixture (ROM) predicted and experimental tensile strength of different natural fibers reinforced HDPE composites were very close to each other. Halpin–Tsai equation was found to be the most effective equation in predicting the Young’s modulus of composites containing different types of natural fibers.

Sulfur‐Impregnated Activated Carbon Fiber Cloth as a Binder‐Free Cathode for Rechargeable Li‐S Batteries

Abstract: A route for the preparation of binder-free sulfur-carbon cathodes is developed for lithium sulfur batteries. The method is based on the impregnation of elemental sulfur into the micropores of activated carbon fibers. These electrodes demonstrate good electrochemical performance at high current density attributed to the uniform dispersion of sulfur inside the carbon fiber.

Effect of alkali treatment on interfacial and mechanical properties of coir fiber reinforced poly(butylene succinate) biodegradable composites

Abstract: The poly(butylene succinate) (PBS) biodegradable composites reinforced with coir fibers were developed. The effect of alkali treatment on the surface morphology and mechanical properties of coir fibers, interfacial shear strength (IFSS) and mechanical properties of coir fiber/PBS composites was studied. The effect of fiber mass content varying from 10% to 30% on the mechanical properties of coir fiber/PBS composites was also investigated. The coir fibers which are soaked in 5% sodium hydroxide solution at room temperature (RT) for 72 h showed the highest IFSS with 55.6% higher than untreated coir fibers. The mechanical properties of alkali-treated coir fiber/PBS composites are significantly higher than those of untreated fibers. The best mechanical properties of alkali-treated coir fiber/PBS composite were achieved at fiber mass content of 25% in this study, which showed an increase of tensile strength by 54.5%, tensile modulus by 141.9%, flexural strength by 45.7% and flexural modulus by 97.4% compared to those of pure PBS resin. The fiber surface morphologies and fractured surface of the composites exhibited an improvement of interfacial fiber–matrix adhesion in the composites reinforced with alkali-treated coir fibers.

Strain-hardening UHP-FRC with low fiber contents

Abstract: This research work focuses on the optimization of strength and ductility of ultra high performance fiber reinforced concretes (UHP-FRC) under direct tensile loading. An ultra high performance concrete (UHPC) with a compressive strength of 200 MPa (29 ksi) providing high bond strength between fiber and matrix was developed. In addition to the high strength smooth steel fibers, currently used for typical UHP-FRC, high strength deformed steel fibers were used in this study to enhance the mechanical bond and ductility. The study first shows that, with appropriate high strength steel fibers, a fiber volume fraction of 1% is sufficient to trigger strain hardening behavior accompanied by multiple cracking, a characteristic essential to achieve high ductility. By improving both the matrix and fiber parameters, an UHP-FRC with only 1.5% deformed steel fibers by volume resulted in an average tensile strength of 13 MPa (1.9 ksi) and a maximum post-cracking strain of 0.6%.

Layer-by-Layer Fabrication of Chemical-Bonded Graphene Coating for Solid-Phase Microextraction

Abstract: A new fabrication strategy of the graphene-coated solid-phase microextraction (SPME) fiber is developed. Graphite oxide was first used as starting coating material that covalently bonded to the fused-silica substrate using 3-aminopropyltriethoxysilane (APTES) as cross-linking agent and subsequently deoxidized by hydrazine to give the graphene coating in situ. The chemical bonding between graphene and the silica fiber improve its chemical stability, and the obtained fiber was stable enough for more than 150 replicate extraction cycles. The graphene coating was wrinkled and folded, like the morphology of the rough tree bark. Its performance is tested by headspace (HS) SPME of polycyclic aromatic hydrocarbons (PAHs) followed by GC/MS analysis. The results showed that the graphene-coated fiber exhibited higher enrichment factors (EFs) from 2-fold for naphthalene to 17-fold for B(b)FL as compared to the commercial polydimethylsioxane (PDMS) fiber, and the EFs increased with the number of condensed rings of PAHs. The strong adsorption affinity was believed to be mostly due to the dominant role of π-π stacking interaction and hydrophobic effect, according to the results of selectivity study for a variety of organic compounds including PAHs, the aromatic compounds with different substituent groups, and some aliphatic hydrocarbons. For PAHs analysis, the graphene-coated fiber showed good precision (<11%), low detection limits (1.52-2.72 ng/L), and wide linearity (5-500 ng/L) under the optimized conditions. The repeatability of fiber-to-fiber was 4.0-10.8%. The method was applied to simultaneous analysis of eight PAHs with satisfactory recoveries, which were 84-102% for water samples and 72-95% for soil samples, respectively.

Controlling the porosity of fibrous scaffolds by modulating the fiber diameter and packing density.

Abstract: Porosity has been shown to be a key determinant of the success of tissue engineered scaffolds. A high degree of porosity and an appropriate pore size are necessary to provide adequate space for cell spreading and migration as well as to allow for proper exchange of nutrients and waste between the scaffold and the surrounding environment. Electrospun scaffolds offer an attractive approach for mimicking the natural extracellular matrix (ECM) for tissue engineering applications. The efficacy of electrospinning is likely to depend on the interaction between cells and the geometric features and physicochemical composition of the scaffold. A major problem in electrospinning is the tendency of fibers to accumulate densely, resulting in poor porosity and small pore size. The porosity and pore sizes in the electrospun scaffolds are mainly dependent on the fiber diameter and their packing density. Here we report a method of modulating porosity in three dimensional (3D) scaffolds by simultaneously tuning the fiber diameter and the fiber packing density. Nonwoven poly(e-caprolactone) mats were formed by electrospinning under various conditions to generate sparse or highly dense micro- and nanofibrous scaffolds and characterized for their physicochemical and biological properties. We found that microfibers with low packing density resulted in improved cell viability, proliferation and infiltration compared to tightly packed scaffolds.

Fluid Mechanics of Papermaking

Abstract: Papermaking is to a large extent a multiphase flow process in which the structure of the material and many of the relevant properties of the final product are determined by the interaction between water and the wood fibers. The dominant feature of a suspension composed of wood fibers and water is its inherent propensity to form bundles of mechanically entangled fibers, known as fiber flocs. However, the phenomena apparent throughout the papermaking process are not unique but in fact have a generic fluid dynamical nature.

Three-dimensional microvascular fiber-reinforced composites.

Abstract: and materials or lack of scalability and vascular complexity of the fabrication approach. Here we show that the introduction of sacrificial fibers into woven preforms enables the seamless fabrication of 3D microvascular composites that are both strong and multifunctional. Underpinning the method is the efficient thermal depolymerization of catalyst-impregnated polylactide (PLA) fibers with simultaneous evaporative removal of the resulting lactide monomer. The hollow channels produced are high-fidelity inverse replicas of the original fiber’s diameter and trajectory. The method has yielded microvascular fiber-reinforced composites with channels over one meter in length that can be subsequently filled with a variety of liquids including aqueous solutions, organic solvents, and liquid metals. By circulating fluids with unique physical properties, we demonstrate the ability to create a new generation of biphasic pluripotent composite materials in which the solid phase provides strength and form while the liquid phase provides interchangeable functionality. Microvascular composite fabrication begins with the mechanized weaving of sacrifi cial fi bers into 3D woven glass

Colored and Functional Silver Nanoparticle−Wool Fiber Composites

Abstract: Silver nanoparticles utilizing the surface plasmon resonance effect of silver have been used to color merino wool fibers as well as imparting antimicrobial and antistatic properties to them to produce a novel silver nanoparticle−wool composite material. This is accomplished by the reduction of silver ions in solution by trisodium citrate (TSC) in the presence of merino wool fibers or fabrics. The silver metal nanoparticles simultaneously bind to the amino acids of the keratin protein in the wool fibers using TSC as the linker. The colors of the resulting merino wool−silver nanoparticle composites range from yellow/brown to red/brown and then to brown/black, because of the surface plasmon resonance effect of silver, and are tuned by controlling the reduction of silver ions to silver nanoparticles to give the required particle size on the fiber surface. In addition to the surface plasmon resonance optical effects, the silver nanoparticle−wool composites exhibit effective antimicrobial activity, thus inhibit...

Dietary fiber type reflects physiological functionality: comparison of grain fiber, inulin, and polydextrose

Abstract: Dietary fiber is a nutritional concept based not on physiological functions but on defined chemical and physical properties. Recent definitions of dietary fiber differentiate inherent plant cell wall-associated fiber from isolated or synthetic fiber. For the latter to be defined as fiber, beneficial physiological effects should be demonstrated, such as laxative effects, fermentability, attenuation of blood cholesterol levels, or postprandial glucose response. Grain fibers are a major natural source of dietary fiber worldwide, while inulin, a soluble indigestible fructose polymer isolated from chicory, and polydextrose, a synthetic indigestible glucose polymer, have more simple structures. Inulin and polydextrose show many of the same functionalities of grain fiber in the large intestine, in that they are fermentable, bifidogenic, and laxative. The reported effects on postprandial blood glucose and fasting cholesterol levels have been modest, but grain fibers also show variable effects. New biomarkers are needed to link the physiological functions of specific fibers with long-term health benefits.

Analysis of the Effects of Solution Conductivity on Electrospinning Process and Fiber Morphology

Abstract: The electrospinning process and morphology of electrospun nanofibers depend on many processing parameters. These parameters can be divided into three main groups: 1) solution properties; 2) processing conditions; and 3) ambient conditions. In this paper, we report the results of a comprehensive investigation of the effects of changing the conductivity of polyethylene oxide (PEO)/water solution on the electrospinning process and fiber morphology. The effects of the conductivity of PEO solution on the jet current and jet path are discussed. Furthermore, the fiber diameter and fiber uniformity are investigated by using scanning electron microscopy techniques.

Linear and nonlinear optical properties of hollow core photonic crystal fiber

Abstract: We review the optical guidance properties of hollow-core photonic crystal fibers. We follow a historical perspective to introduce the two major optical guidance mechanisms that were identified as operating in these fibers: photonic bandgap guidance and inhibited coupling guidance. We then review the modal properties of these fibers and assess the transmission loss mechanisms in photonic bandgap guiding hollow-core photonic crystal fiber. We dedicate a section to a review of the technical basics of hollow-core photonic crystal fiber fabrication and photonic microcell assembly. We review some of the early results on the use of hollow-core photonic crystal fiber for laser guiding micro-sized particles, as well as the generation of stimulated Raman scattering, electromagnetically induced transparency and laser frequency stabilization when the fiber core is filled with a gas-phase material. We conclude this review with a non-exhaustive list of prospects where hollow-core photonic crystal fiber could play a cen...

Flexible, Light‐Weight, Ultrastrong, and Semiconductive Carbon Nanotube Fibers for a Highly Efficient Solar Cell

Abstract: Carbon nanotubes have been widely introduced to fabricate high-efficiency organic solar cells because of their extremely high surface area (e.g., ca. 1600 mg 1 for single-walled nanotubes) and superior electrical properties. In one direction, nanotubes are used in electrode materials. For example, the incorporation of nanotubes onto titania nanoparticle films has been shown to increase the roughness factor and decrease the charge recombination of electron/hole pairs, and the replacement of platinum with nanotubes as counter electrode catalyzed the reduction of triiodide to improve the cell performance. In another direction, the distribution of nanotubes within the photoactive layer improved the short circuit current density and fill factor owing to rapid charge separation at the nanotube/electron donor interface and efficient electron transport through nanotubes. However, the degrees of improvement are far from what is expected for nanotubes, mainly because of random aggregation of nanotubes in the cells. For a random nanotube network, the electrons have to cross many more boundaries. Therefore, alignment of nanotubes will further greatly improve cell performance as charge transport is more efficient. Solar cells have typically been fabricated from rigid plates, which are unfavorable for many applications, especially in the fields of portable and highly integrated equipment. As a result, flexible devices have recently become the subject of active research as a good solution. In particular, weavable fiber solar cells are very promising and have attracted increasing attention in recent years. Fiber solar cells based on metal wires, glass fibers, or polymer fibers have been investigated. Herein, we first made a family of novel organic solar cells with excellent performance from the highly aligned nanotube fiber. Compared with traditional solar cells fabricated from rigid plates or recently explored flexible films/fibers, nanotube fiber solar cells demonstrate some unique and promising advantages. Firstly, as the building nanotubes are highly aligned, the fiber shows excellent electrical properties, which provide the novel solar cell with higher short-circuit photocurrent, better maximum incident monochromatic photon-to-electron conversion efficiency, and higher power conversion efficiency. Secondly, nanotube fibers show excellent mechanical properties, much stronger than Kevlar and comparable to the strongest commercial fibers of zylon and dyneema in tensile strength. Thirdly, these fibers are flexible, light-weight, and weavable and have tunable diameters ranging from micrometers to millimeters. The above properties provide nanotube fiber solar cells with a broad spectrum of applications, including power regeneration for space aircraft and clothing-integrated photovoltaics. To produce desired nanotube fibers, high-quality nanotube arrays were first synthesized by a typical chemical vapor deposition method. The synthetic details are reported elsewhere. To summarize, Fe/Al2O3 was used as the catalyst, ethylene served as the carbon source, and Ar with 6%H2 was used to carry the precursor to a tube furnace, where the growth took place. The reaction temperature was controlled at 750 8C and the reaction time was typically between 10 and 20 min. Fibers were directly spun from the nanotube array (see Figure S1 in the Supporting Information), and the fiber diameter was controlled from 6 to 20 mm by varying the initial ribbon, that is, a bunch of nanotubes pulled out of the array at the beginning of the spinning. The nanotube fiber can be spun with lengths of tens of meters or even longer, and the fiber is uniform in diameter. The density of the nanotube fiber was calculated to be on the order of 1 gcm , and its linear density was on the order of 10 mgm , relative to 10 mgm 1 and 20– 100 mgm 1 for cotton and wool yarns, respectively. As shown in Figure 1a, the nanotube fiber is flexible and will not break after being bent, folded, or even tied many times. Highresolution transmission electron microscopy (see Figure 1b) [*] T. Chen, S. Wang, Z. Yang, Q. Feng, X. Sun, Dr. L. Li, Prof. Z.-S. Wang, Prof. H. Peng Laboratory of Advanced Materials, Fudan University Shanghai 200438 (China) E-mail: zs.wang@fudan.edu.cn penghs@fudan.edu.cn T. Chen, Z. Yang, X. Sun, Dr. L. Li, Prof. H. Peng Key Laboratory of Molecular Engineering of Polymers of Ministry of Education, Fudan University (China) T. Chen, Z. Yang, X. Sun, Dr. L. Li, Prof. H. Peng Department of Macromolecular Science, Fudan University (China) S. Wang, Prof. Z.-S. Wang Department of Chemistry, Fudan University (China) [] These authors contributed equally to this work.

Bamboo Fiber Reinforced Polypropylene Composites and Their Mechanical, Thermal, and Morphological Properties

Abstract: Short bamboo fiber reinforced polypropylene composites were prepared by incorporation of various loadings of chemically modified bamboo fibers. Maleic anhydride grafted polypropylene (MA-g-PP) was used as compatibilizer to improve fiber–matrix adhesion. The effects of bamboo fiber loading and modification of the resin on the physical, mechanical, thermal, and morphological properties of the bamboo reinforced modified PP composites were studied. Scanning electron microscopy studies of the composites were carried out on the interface and fractured surfaces. Thermogravimetric analysis and IR spectroscopy were also carried out. At 50% volume fraction of the extracted bamboo fiber in the composites, considerable increase in mechanical properties like impact, flexural, tensile, and thermal behavior like heat deflection temperature were observed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Directly drawing self-assembled, porous, and monolithic graphene fiber from chemical vapor deposition grown graphene film and its electrochemical properties.

Abstract: Integration of graphene into macroscopic architectures represents the first step toward creating a new class of graphene-based nanodevices. We report a novel yet simple approach to fabricate graphene fibers, a porous and monolithic macrostructure, from chemical vapor deposition grown graphene films. Graphene is first self-assembled from a 2D film to a 1D fiberlike structure in an organic solvent (e.g., ethanol, acetone) and then dried to give the porous and crumpled structure. The method developed here is scalable and controllable, delivering tunable morphology and pore structure by controlling the evaporation of solvents with suitable surface tension. The fibers are 20–50 μm thick, with a typical electrical conductivity of ∼1000 S/m. The cyclic voltammetric studies show typical capacitive behavior for the porous graphene fibers with good rate stability and capacitance values ranging from 0.6 to 1.4 mF/cm2. Decorated with only 1–3 wt % MnO2, the graphene/MnO2 composites exhibit remarkable enhancement of c...

High-pressure and high-temperature characteristics of a Fabry―Perot interferometer based on photonic crystal fiber

Abstract: A fiber-optic Fabry-Perot interferometer was constructed by splicing a short length of photonic crystal fiber to a standard single-mode fiber. The photonic crystal fiber functions as a Fabry-Perot cavity and serves as a direct sensing probe without any additional components. Its pressure and temperature responses in the range of 0-40 MPa and 25°C-700°C were experimentally studied. The proposed sensor is easy to fabricate, potentially low-cost, and compact in size, which makes it very attractive for high-pressure and high-temperature sensing applications.