Showing papers on "Fiber published in 1986"

Matrix fracture in fiber-reinforced ceramics

Abstract: A fiber-reinforced ceramic subject to tensile stress in the fiber direction can undergo extensive matrix cracking normal to the fibers, while the fibers remain intact. In this paper, the critical conditions for the onset of widespread matrix cracking are studied analytically on the basis of fracture mechanics theory. Two distinct situations concerning the fiber-matrix interface are contemplated : (i) unbonded fibers initially held in the matrix by thermal or other strain mismatches, but susceptible to frictional slip, and (ii) fibers that initially are weakly bonded to the matrix, but may be debonded by the stresses near the tip of an advancing matrix crack. The results generalize those of the Aveston-Cooper-Kelly theory for case (i). Optimal thermal strain mismatches for maximum cracking strength are studied, and theoretical results are compared with experimental data for a SiC fiber, lithium-alumina-silicate glass matrix composite.

Fiber reinforced glasses and glass-ceramics for high performance applications

Abstract: The development of fiber reinforced glass and glass-ceramic matrix composites is described The general concepts involved in composite fabrication and resultant composite properties are given for a broad range of fiber and matrix combinations It is shown that composite materials can be tailored to achieve high levels of toughness, strength, and elastic stiffness, as well as wear resistance and dimensional stability

Strength Measurement of Optical Fibers by Bending

Abstract: A bending technique for the strength measurement of glass fibers is described and an analysis is presented which determines the effective tested length as a function of the statistical parameters which describe the fracture properties of the fiber. The analysis is used to compare strength data determined in both tension and bending for various representative fibers. It is found that the tensile strength cannot be predicted from the strength in bending and vice versa because the tested lengths differ by at least 3 orders of magnitude. Thus, while bending does not replace tension as a measurement technique, it does provide additional valuable information about the flaw size distribution.

Fiber-reinforced silicon carbide

Abstract: On decrit la fabrication de composites de SiC renforces de fibres ceramiques par impregnation de vapeur chimique, liaison reactive par impregnation de silicium liquide, impregnation avec polymerisation subsequente et decomposition thermique des composes organosilicies. Les bases chimiques et physiques de ces processus sont discutees

Thermally conductive polymer compositions

Abstract: While polymers are widely used for their excellent insulating properties, there is a growing need for thermally conductive polymer compounds. The thermal conductivity of metal particle, mineral particle, and carbon fiber filled compounds are examined at volume concentrations up to the maximum packing fraction of each filler. From these data the coefficients in Nielsen's model were determined for each type of filler. Gaps in available thermal conductivity data were then predicted using these coefficients, the properties of the polymer and filler, and the volume concentration of the filler. Gaps were found to exist mostly for compounds containing short fiber reinforced compounds. A comparison of predicted values of thermal conductivity for such systems with the sparse data available shows that Nielsen's model cannot be applied to highly filled fiber reinforced composites because it cannot account for the anisotropy of such compositions.

Soil Randomly Reinforced with Fibers

Abstract: A fine-grained soil was mixed with 1% by volume of 20-mm-long synthetic fibers. Laboratory specimens were compacted at various water contents and tested in unconfined compression. Specimens compacted wet of optimum were found to have somewhat greater strength (up to 25%) and strain to failure with fibers in comparison with specimens without fibers. Dry of optimum, there was little or no benefit from the fibers. Nylon and polypropylene fibers gave similar results. Mixing the fiber into the soil was difficult; especially for the smaller (less than 0.20 mm diameter) fibers.

Gas separation by high‐flux, asymmetric hollow‐fiber membrane

Abstract: A mathematical model of multicomponent permeation systems with high-flux, asymmetric hollow-fiber membranes is presented. The model takes into account the permeate pressure variation inside the fiber. In the special case of negligible permeate pressure drop, the model yields a simple analytical solution for membrane area calculation that eliminates the numerical integration step required in existing methods. Laboratory multicomponent permeation experiments have verified the mathematical model and have demonstrated the technical feasibility of using the high-flux asymmetric cellulose acetate hollow fiber for H,, CO,, and H,S separation. It is shown that the selectivity of the cellulose acetate membrane is ideally suited to the recovery of hydrogen from the purge gas of reactor recycle loops. For the separation of high-concentration CO, or H,S, the test data show that the permeabilities of the individual components in mixed gas permeation are significantly different from those of pure gases.

Stress Transfer in Single Fiber/ Resin Tensile Tests

Abstract: Microscale (25 mm gauge length) “dogbone” resin specimens with single carbon fibers embedded through the length of the specimen have been studied as a method for determining the fiber-resin interphase strength. The specimens are pulled in tension until the fiber fragments to a critical length, lc . Evidence is presented here, based primarily on the relaxation of stress birefringence around the fiber fragment, that this test may not be an unambiguous measure of fiber-resin adhesion. Data obtained for various production lots of AS-4, AS-6, and IM-6 fibers indicate an increase in lcd with laminate tensile strength. Although there is theoretical justification for this correlation, it requires that the interphase shear strength is relatively constant. In those instances where interfacial adhesion was expected to be low, i.e., surface contamination or unsurface treated fiber, there was a significant increase in lc/d and usually a distinct difference in stress birefringence compared to “good” adhesion. ...

Swash plate type compressor

Abstract: PURPOSE:To reduce abrasion of rotor by forming the surface section for forming a swash plate in rotor through lamination of collected fiber mainly composed of wiskers and collected fiber mainly composed of short fibers CONSTITUTION:In a swash plate type compressor, a piston 8 fitted slidably in plural cylinder bores 10 made in parallel with a rotary shaft 11 is reciprocated in axial direction through an intermediate member or a semi-sphercal shoe 9 by the rotation of a rotor 7 having a swash plate Here, at least the surface sections 1, 1 forming the swash plate of the rotor 7 is composed of first fiber reinforced metal complex material sections 21, 21' reinforced with first fibers such as alumina short fibers, second fiber reinforcedmetal complex material sections 3, 3' composed of second fibers such as silicon carbide wiskers and mixed fiber reinforced metal complex material sections 4, 4' formed at the interface of said sections

Composite heat transfer means

Abstract: A thermal heat transfer member is disclosed for use with electronic or microwave systems. The thermal heat transfer member comprises a generally planar composite member in which elongated high thermal conductivity fibers are disposed within a matrix material. The matrix material may be an insulating epoxy or thermoplastic resin, while the fibers are elongated continuous commonly directed graphite fibers. The fiber ends terminate at a thermal contact surface which is interfaced with a heat sink. The thermal contact surface may be the transverse edge of the planar member or can be substantially parallel to the planar member. The fiber ends are inclined at an angle with respect to the plane of the planar member to provide for termination of the fibers at the thermal contact surface parallel to the planar member. Heat into the composite member is transferable along the commonly directed graphite fibers.

Nutritional, Fatty Acid, and Oil Characteristics of Pumpkin and Melon Seeds

Abstract: Nutritional and oil characteristics of pumpkin and melon seeds were investigated. On a dry basis, the data obtained for the two seeds, respectively, were: crude oil 45.4 and 37.8%; crude protein, 32.3 and 25.2%; crude fiber, 12.1 and 15.4%; and ash, 4.65 and 3.85%. Food energy values were 2.83 and 2.59 MJ/100g, respectively. The seeds were found to have considerable amounts of essential minerals (K, Ca, Mg, Fe, Cu, Zn, and P). The defatted flour of the pumpkin and melon seeds contained, respectively: crude protein, 55.4 and 39.4%; crude fiber, 28.1 and 24.7%; and ash, 7.23 and 6.18%. The major fatty acid of the oils was linoleic (18:2) at concentrations of 43.1 and 64.6%, followed by oleic (18:1), 37.8 and 20.1%, respectively.

Fabrication and characterization of low-loss optical fibers containing rare-earth ions

Abstract: Low-loss fibers containing rare-earths have been produced with high absorption levels in the visible and near infrared regions. Although containing relatively large quantities of rare-earth impurity dopants, the fibers possess low-loss windows where the attenuation is similar to that observed in undoped fibers. This attribute makes the fibers attractive for use in long distributed sensors, as well as low-threshold fiber lasers. Fiber characteristics relevant to these two applications are uniformity of dopant incorporation, absorption and fluorescence spectra, and fluorescence lifetime. These measurements are presented, together with their respective temperature dependences. The fiber fabrication method is described and results given for Nd3+-, Er3+-, and Tb3+-doped fibers.

Synthesis of fiber-reinforced SiC composites by chemical vapor infiltration

Abstract: Fabrication de composites par infiltration et depot chimique en phase vapeur de SiC dans une structure fibreuse de SiC. L'utilisation d'un gradient thermique et d'un ecoulement gazeux force permet de reduire la duree d'infiltration. On etudie les proprietes mecaniques de ces composites

Melt-blown material with depth fiber size gradient

Abstract: A filter medium is formed by sequentially depositing layers of melt-blown thermoplastic fibers, having the same composition but different sizes, onto a collector. The resulting laminate web has a fiber size gradient across its depth so that the large particulate can be trapped across the filter's depth without prematurely plugging the fine fiber, high efficiency layers.

Multi-layered microfiltration medium

Abstract: A multilayered microfiltration medium exhibiting high particle capture efficiency and minimal flow restriction having a base substrate layer, a fine fiber filtration or efficiency layer deposited on and adhered to the substrate layer and a nonhandleable, non-self-supporting protective cover layer which is self-adhering to the fine fiber layer and has a very smooth outer surface. Suitable cover layer materials include polystyrene and polycarbonate fibers.

Tunable single-mode fiber lasers

Abstract: Tunable laser action has been obtained in Nd3+- and Er3+-doped single-mode fiber lasers. In the case of the Nd3+-doped fiber, an extensive tuning range of 80 nm has been achieved. Tunable CW lasing also has been observed for the first time in an Er3+-doped fiber laser, which has an overall tuning range of 25 nm in the region of \lambda = 1.54 /mu m.

The influence of fiber length and fiber orientation on damping and stiffness of polymer composite materials

Abstract: This paper describes the theoretical analysis, the experimental results and the curve-fitting of the analytical model to the experimental results on the influence of fiber length and fiber orientation on damping and stiffness of polymer-composite materials. The experimental results show that, as predicted, very low fiber aspect ratios are required to produce significant improvements in damping. Measurements and predictions also indicate that the control of lamina orientation in a continuous fiber-reinforced laminate may be a better approach to the improvement of damping than the control of the fiber aspect ratio.

Effect of Fiber and Matrix Maximum Strain on the Energy Absorption of Composite Materials

Abstract: Static crushing tests were conducted on graphite composite tubes to examine the influence of fiber and matrix maximum strain at failure on the energy absorption capability of graphite reinforced composite material. Fiber and matrix maximum strain at failure were determined to significantly effect energy absorption. The higher strain at failure composite material system, AS-4/5245, exhibited superior energy absorption capability compared to AS-4/934, T300/5245 or T300/934 composite material. Results of this investigation suggest that to achieve maximum energy absorption from a composite material a matrix material that has a higher strain at failure than the fiber reinforcement should be used.

Non-woven activated carbon fabric

Abstract: An air and water vapor permeable, toxic vapor absorptive non-woven fabric material comprising a web-laid sheet containing fibrillated acrylic fiber, and an activated carbon constituent selected from the group consisting of activated carbon fiber, activated carbon particles, and mixtures of activated carbon fiber and activated carbon particles.

Fiber for lateral beaming of laser beam

Abstract: A fiber for lateral beaming of a laser beam, wherein an affected portion in a cavity of an internal organ in a living body is irradiated by the laser beam in a through-endoscopic manner. The fiber for lateral beaming of the laser beam is constructed such that a transparent tubular member is coupled to the forward end portion of a fiber through two coating layers, and an anti-reflection coating layer is formed on a laser beam exiting surface of the transparent tubular member. Owing to the anti-reflection coating layer, this fiber for lateral beaming is free from the harmful leaking beam. Since the transparent tubular member is connected to the fiber through the two coating layes, the fiber can avoid being broken.

Composite article and method of making same

Abstract: A method of making a composite article and a composite article specifically adapted for use in high temperature, corrosive and errosive environments comprising a carbon fibrous substrate, including a pyrolytic carbon sheath formed about each fiber of the substrate; a metallic carbide, oxide, or nitride compliant coating over the coated fibers of the substrate; and an impermeable metallic carbide, oxide or nitride outer protective layer formed about the entire periphery of the coated substrate. In accordance with the method of the invention, the compliant metallic coating is applied to the fibers in a manner such that any mechanical stresses built-up in the substrate due to a mismatch between the coefficient of thermal expansion of the fibrous substrate and the coating are effectively accomodated.

Hot-melt-adhesive composite fiber

Abstract: A hot-melt-adhesive composite fiber having a broad temperature range of hot-melt adhesion, exhibiting a low heat-shrinkage over the whole temperature range thereof, having a high tenacity and suitable to production of a non-woven fabric having superior restoring properties, bulkiness, draping properties and feeling is provided, which composite fiber comprising a fiber-forming component and an adhesive component, the fiber-forming component comprising 0.5 to 30% by weight of a copolymer of a carboxyl group containing modified polyolefin with a polyamide, and the adhesive component comprising a carboxyl group-containing modified polyolefin, an unmodified polyolefin or a mixture thereof.

The number and diameter distribution of axons in the monkey optic nerve.

Abstract: Using an automated image analysis system, cross-sections from optic nerves of 17 normal cynomolgus monkeys were examined The number of nerve fibers, their density, and the distribution of their diameters for whole nerves and for various regions of the nerve cross-section were estimated The mean total number of fibers in the optic nerve was 12 million The mean diameter of axons was 08 micron The method of tissue fixation substantially affected the measurements Histograms of fiber diameter suggested a trimodal distribution of fiber size with peaks at 05, 08, and 15 micron The relative proportions of these fiber peaks differed significantly in different regions of the nerve The highest proportion of large fibers was in the superior nerve periphery The highest concentration of smallest fibers and the highest density of all fibers were located centrally in the infero-temporal quadrant The observation that higher fiber density and smaller mean fiber diameter are skewed toward the inferior pole appears to coincide with the inferior position of the fovea with respect to the optic nerve head This finding has importance for interpretation of pathologic changes in the optic disc

Fluid flow sensing apparatus for in vivo and industrial applications employing novel optical fiber pressure sensors

Abstract: A fiber optical fiber fluid flow measuring device is provided for in vivo determination of blood flow in arteries. The device includes a fiber optical fluid differential pressure measuring device having at least one optical fiber sensor which optical fiber sensor is positioned in the blood flow passage in a restricted flow area. The fiber optical differential pressure fluid sensor is connected to a divided interferometer associated with an opto-electronic demodulator which has an output signal representing the differential pressure in the sensed area. The device also has utility in industrial applications.

Radiative transfer through a fibrous medium: Allowance for fiber orientation

Abstract: The problem of radiative transfer through a fibrous medium has been formulated rigorously to account for the orientation of the fibers. The fibers in the medium can be either randomly oriented or aligned. It is shown that the radiative properties of the medium, e.g. the extinction efficiency, are strongly dependent on the fiber orientation. A specific case of collimated irradiation on the fibrous medium with fibers randomly oriented in a plane is investigated. Parametric studies are performed to determine the effect of fiber size and fiber optical properties on the transmissivity and reflectivity of the medium.

A radial flow hollow fiber bioreactor for the large‐scale culture of mammalian cells

Abstract: A radial flow hollow fiber bioreactor has been developed that maximizes the utilization of fiber surface for cell growth while eliminating nutrient and metabolic gradients inherent in conventional hollow fiber cartridges. The reactor consists of a central flow distributor tube surrounded by an annular bed of hollow fibers. The central flow distributor tube ensures an axially uniform radial convective flow of nutrients across the fiber bed. Cells attach and proliferate on the outer surface of the fibers. The fibers are pretreated with polylysine to facilitate cell attachment and long-term maintenance of tissuelike densities of cell mass. A mixture of air and CO(2) is fed through the tube side of the hollow fibers, ensuring direct oxygenation of the cells and maintenance of pH. Spent medium diffuses across the cell layer into the tube side of the fibers and is convected away along with the spent gas stream. The bioreactor was run as a recycle reactor to permit maximum utilization of nutrient medium. A bioreactor with a membrane surface area of 1150 cm(2) was developed and H1 cells were grown to a density of 7.3 x 10(6) cells/cm(2).