Showing papers on "Fiber published in 1976"

Synthesis of Continuous Sic Fibers with High Tensile Strength

Abstract: Continuous Sic fibers with a tensile strength of 350 kg/mm2 and a Young's modulus of 30 tons/mm2 were synthesized from an organometallic polymer. Continuous fibers were first obtained by heat-treating a polycarbosilane polymer which had been synthesized from dimethyldichlorosilane. The fiber, which contains ultrafine-grain crystallites of β-Sic, has no fiber texture measurable by X-ray diffraction and high-voltage electron microscopy.

Human body implant of graphitic carbon fiber reinforced ultra-high molecular weight polyethylene

Abstract: A medical body implant element that is intended to experience rolling or sliding pressure during its function in the human body comprises microparticles of ultra-high molecular weight polyethylene which are fused together into a matrix. A quantity of graphitic carbon fibers of short, random lengths is disposed in intersticies of the matrix. The resultant composite is wear-resistant and substantially isotropic.

Pull-Out Mechanism in Steel Fiber-Reinforced Concrete

Abstract: The bond between steel fibers and portland cement matrices is a critical factor in determining the strength properties of fiber-reinforced concrete structural elements. The influence of the following three major parameters on the pull-out behavior of fibers was studied: the angle of orientation of the fibers with the loading direction, the number of fibers being simultaneously pulled out from the same area, and the efficiency of random orientation. It is shown that: (1)The pull-out load of a randomly oriented fiber is not lower than that of an aligned fiber; (2)the pull-out capacity of a group of randomly oriented fibers decreases drastically when the number of fibers pulling out from the same area increases; and (3)the efficiency of fiber orientation after matrix cracking is substantially higher than efficiency factors derived from the theoretical elastic considerations. These results seem to explain why the addition to a concrete matrix of fibers with highly improved bond properties does not often lead to an equivalent improvement in the composite properties.

Progress in the Development of Graphite- Aluminum Composites Using Liquid Infiltration Technology:

Abstract: The most successful techniques for producing graphite-aluminum com posites have been those that utilize liquid-metal infiltration of graphite yarn. Almost all grades and types of graphite yarn can be infiltrated; how ever, a fiber coating is required, which results in wetting and provides a diffusion barrier to inhibit aluminum carbide formation. Two fiber coating methods are discussed in detail, including the sodium pretreatment method that results in intermetallic compound formation on the fiber and a chem ical vapor deposition method that applies a titanium-boron codeposit.

Structural improvement of carbon fibers prepared from benzene.

Abstract: Carbon fibers have been prepared by thermal decomposition of benzene at temperatures 1050–1080°C. Structural change with stepwise heat treatments up to 3000°C has been studied by X-ray and selected-area electron diffraction. The as-prepared fiber as well as the 1400°C-treated is basically of turbostratic structure, but has a preferred orientation of aromatic carbon planes more or less parallel to the fiber axis. By heat treatment around 2000°C, the preferred orientation is improved enormously; the carbon planes become almost completely parallel to the fiber axis, while the stacking order is still turbostratic. A three dimensional graphite structure is developed by heat treatment above 2400°C, which has qualitatively a similar behavior to that of graphitizing carbon. The fiber heat-treated at 3000°C consists of graphite layers concentrically surrounding the fiber axis.

Some structural aspects of sisal fibers

Abstract: A critical account has been presented of the recent investigation on the chemical modification of lignocellulosic sisal fibers. The molecular structure of the paracrystalline cellulose, which forms the major constituent of the fiber, was studied by x-ray diffraction technique. Scanning electron microscope examination of the multicellular structure, surface topology, and fracture morphology of the fiber was carried out. The mechanical properties of the sisal ultimate cell and the “technical” fiber have been investigated by means of a microextensometer and an Instron tensile tester, respectively.

Impact Strength of Angle Ply Fiber Reinforced Materials

Abstract: Tensile strength of angle ply balanced laminated made of glass fibers and epoxy matrix has been investigated under dynamic loading using an instrumented drop weight apparatus. A comparison of theoretical and experimental stress-strain curves reveals that good agreement exists for a certain range of fiber orientation. Different failure criteria have to be used for each range. Failure stresses in the dynamic case are found to be con siderably higher than the corresponding static values for the complete range of fiber orientation. Failure strains and initial effective moduli are the same for static and for impact loadings.

The effect of molecular weight on the physical and mechanical properties of ultra-drawn high density polyethylene

Abstract: A study has been made on the effects of molecular weight on the physical and mechanical properties of cold-extruded high density polyethylene. Prior data indicate that such ultra-drawn strands contain a significant fraction of extended-chain crystals. Four samples, spanning the molecular weight range of 59,000 to 147,000, were cold-extruded under the same conditions and were examined with respect to their melting point, degree of crystallinity, linear expansion coefficient, Young' modulus, strain to break, and tensile strength. The degree of crystallinity, linear expansion coefficient, and modulus did not change significantly with molecular weight. The melting point, strain to break, and tensile strength do increase with increasing molecular weight. This leads to the conclusion that the amount of extended-chain crystals is invariant with molecular weight. Higher molecular weight polymers are seen as providing a greater number of the chains, thus giving the fiber a higher tensile strength.

Microbending losses of single-mode, step-index and multimode, parabolic-index fibers

Abstract: We present formulas for the microbending losses of fibers that are caused by random deflections of the fiber axis. We consider single-mode (or almost single-mode), step-index fibers and multimode, parabolic-index fibers and compare their losses. Loss formulas for the single-mode fiber are derived from coupled-mode theory using radiation modes. Simple empirical approximations of the general formulas are also presented. The losses of the parabolic-index, multimode fiber have been derived earlier. The losses of both fiber types are compared by assuming either that each fiber samples the spatial Fourier spectrum of the distortion function at the same spatial frequency, or by comparing typical fibers of each type with each other regardless of any similarity between them. It is found that the multimode, parabolic-index fiber has lower losses if it supports a sufficient number of guided modes.

Method of preparing a porous implantable material from polytetrafluoroethylene and carbon fibers

Abstract: A composition of material suitable for in vivo implantation to provide an environment in which normal tissue growth is fostered which composition is a porous fibrous structure in which the critical surface tension of the fibers is 35 dynes per centimeter or higher. This composition in the preferred form is a porous structure of carbon or graphite fibers bonded together by sintered polytetrafluoroethylene in a manner to expose a maximum amount of fiber surface. Another composition of material suitable for implantation for wear surfaces includes carbon fibers and polytetrafluoroethylene resin and is processed to align the carbon fibers with the wear surfaces. The method of preparing both material includes the step of mixing, filtering, compressing, rolling, sintering and drying. The method of stabilizing appliances or implants includes bonding the ingrowth material to the appliance or implant. Also the combination of the ingrowth material with appliances, tendon replacement elements and wear material are included.

Interfacial properties of kevlar‐49 fiber‐reinforced thermoplastics

Abstract: A single-filament pull-out test was used to study adhesion of Kevlar-49 fibers to thermoplastic polymers. The test involved pulling a partially embedded fiber out of a polymer film. Kevlar-49 fibers with three different surface treatments were used with five thermoplastic materials. The test resulted in the measurement of two properties, an interfacial bond strength and a frictional shear strength. The interfacial bond strength is an essential factor in determining the critical aspect ratio of discontinuous fibers in a composite. The frictional shear strength was found to correlate with the tensile strength of discontinuous fiber composites which fail by fiber pull-out. Scanning electron microscopy was used to examine the fiber pull-out specimens after testing. Observations of the fiber showed that the failure mode at the fiber–matrix interface was complex. The predominant failure mode was fracture at the interface (or in some weak boundary layer). In some cases, cohesive failure of the fiber surface was observed, with the result that strips of material were torn from the fiber surface.

Analysis of Reinforced Fibrous Concrete Beams

Abstract: A method has been developed to predict the ultimate strength of concrete beams reinforced with a combination of steel bars and randomly distributed steel fibers. Strengths of three full-size beams were obtained experimentally to verify the analytical method. The method, which applies to beams using a cement-rich mortar mix with the steel fibers, shows good correlation with experimental results. A dynamic bond stress of 333 psi was assumed for the fibers. Fiber lengths were from 1-1/2 in. to 2-1/4 in. and the fiber amount was varied from 1.22% to 1.51% by volume. The test programs showed that: (1) Steel fibrous concrete increased the flexural load capacity of the reinforced beams by about 25%; (2) crack width and crack spacing were less than in a conventional reinforced beam; and (3) the post-cracking stiffness of the fibrous beams was greater than a conventional beam.

Propagation model for long step-index optical fibers.

Abstract: This paper reports some theoretical and experimental investigations on the propagation of a pulse in long step-index optical fibers where mode conversion is present. We derive simple analytical expressions for the frequency response and the radiation pattern as a function of the fiber’s length provided the launching conditions are known. A comparison with experimental observations made on a 3-km long Corning fiber shows reasonable agreement. We conclude that the approximations used to obtain the simple analytical solutions are satisfactory for predicting the transmission characteristics of the fiber.

In vitro polymerization of flagellar and ciliary outer fiber tubulin into microtubules.

Abstract: About 10--20% of the total protein in the outer fiber fraction was solubilized by sonication in a solution containing 5 mM MES, 0.5 mM MgSO4, 1.0 mM EGTA, 1.0 mM GTP, and 0 or 50 mM KC1 at pH 6.7. The sonicated extract was shown by analytical centrifugation to consist largely of a 6 S component (tubulin dimer), having a molecular weight of 103,000, as determined by gel filtration, and possessing a colchicine-binding activity of 0.8 mole per tubulin dimer. The tubulin fraction failed to polymerize into microtubules by itself. Addition of a small amount of the ciliary outer fiber fragments or reconstituted short brain microtubules, however, induced polymerization, as demonstrated by viscosity of flow birefringence changes as well as light or electron microscopic observations. The growth of heterogeneous microtubules upon mixing outer fiber tubulin with DEAE-dextran-decorated brain microtubules was observed by electron microscopy. Microtubules were reconstituted from outer fiber tubulin without addition of any nuclei fraction when a concentrated tubulin fraction was warmed at 35degree. A few doublet-like microtubules or pairs of parallel singlet microtubules that were closely aligned longitudinally could be observed among many singlet microtubules. Unlike other fiber microtubules, the reconstituted polymers were depolymerized by exposure to Ca2+ ions, high or low ionic strength, colchicine, low temperature or SH reagents. No microtubules were assembled under these conditions.

Micro lens formation at optical fiber ends

Abstract: Method of formation of lenses at optical fiber ends to increase the coupling efficiency thereof. In a first embodiment, the end of the optical fiber is masked with a substance non-soluble in the etching reagent. The portion of the coating at the very end of the fiber is then removed and the fiber end immersed in an etching reagent. The etching reagent serves to dissolve the uncoated portion of the fiber. By controlling the amount of time that the fiber end is in the reagent, different lens shapes may be formed. In a second embodiment, the fiber end is dipped into a liquid epoxy compound whereby a portion of the epoxy is deposited onto the fiber end. The surface tension of the portion deposited thereon draws the liquid epoxy into the desired lens shape. The epoxy is then hardened to form a permanent lens structure on the fiber end.

Method for drawing fibers

Abstract: A method for drawing silica fibers utilizing an electrical resistance furnace includes the steps of heating a preform so that it begins to flow forming a fiber; pulling the fiber from the furnace; and flushing the preform and the fiber within the furnace with counteracting inert gas flows, the gas flows protecting the preform and the fiber from contamination. Apparatus used with the above-described method is also disclosed.

Mechanical Properties of Glass and Steel Fiber Reinforced Mortar

Abstract: Tensile, flexural and compressive tests were conducted on mortar specimens reinforced with different lengths and volumes of steel and glass fibers. The tensile flexural strength of reinforced specimens was at most two to three times that of plain mortar while the corresponding strains or deflections were as much as ten times that of mortar. The stresses and strains at first cracking were not significantly different from those of plain mortar. The values of the modulus of elasticity and the extent of nonlinearity was observed to depend on the methods of deformation measurement. Extensive microcracking was observed on the surfaces of failed flexural specimens indicating a significant contribution of the matrix even after the first cracking. For steel fiber reinforced specimens, the peak loads and deformations appear to be linearly related to the fiber parameter: v f(L/D). After failure, steel fibers pulled out while most of the glass fibers broke.

Air filter material

Abstract: An air filter material having the construction of (1) an upper fibrous layer to be disposed at upper-stream position of influent air, containing 50 to 70% by weight of small diameter polyester fiber and 50 to 30% by weight of larger diameter polyester fiber, the basis weight of the layer being 25 to 45 g/m2 ; (2) an intermediate fibrous layer partially jointed to the upper layer by local intertwinement of fibers, containing 60 to 80% by weight of small diameter polyester fiber and 20 to 40% by weight of larger diameter polyester fiber, the basis weight of the intermediate layer being 40 to 60 g/m2 ; (3) a lower fibrous layer to be disposed at downstream position of the influent air, which is partially jointed to the intermediate layer by local intertwinement of fibers and which contains 60 to 80% by weight of small diameter rayon fiber and 40 to 20% by weight of larger diameter rayon fiber, the basis weight of the lower fibrous layer being 80 to 100 g/m2 ; and (4) a resin applied to the unified mass of the three fibrous layers; has improved dust holding capacity and air filter efficiency and a high in mechanical strength.

Coating of fiber lightguides with UV cured polymerization products

Abstract: Glass fiber lightguides require polymer coatings for protection. A new coating system comprising an acrylate-epoxy polymer that is UV cured is convenient to apply and gives excellent strength and durability to fiber lightguides.

Method for manufacturing helical optical fiber

Abstract: An optical cable which is relatively immune to the effects of bending and/or tension comprises a helical optical fiber loosely confined within a protective sheath. Apparatus is disclosed for fabricating the helical fiber. For example, as the fiber is drawn from a heated preform the fiber is subjected to periodic, pulsating jets of an inert gas, such as nitrogen, which physically deform the fiber into the desired helical configuration.

Epoxy‐acrylate‐coated fused silica fibers with tensile strengths ≳500 ksi (3.5 GN/m2) in 1‐km gauge lengths

Abstract: Laser‐drawn epoxy‐acrylate‐coated fused silica fibers (∼110 μm fiber diameter) have been produced with high and exceptionally uniform strength. When tested in 20‐μm lengths, they show a single‐moded Weibull distribution, (m∼25), a median tensile strength Sm of 750 ksi (5.25 GN/m2), and a coefficient of variation (ν) of about 0.04. Using the previously justified ’’weakest link’’ model, this predicts Sm∼600 ksi (4.2 GN/m2) for l‐km gauge lengths. The measured strength of a 1680‐m‐long fiber (i.e., the minimum strength found in testing 84 20‐m lengths) is 620 ksi (4.35 GN/m2). The capability of drawing kilometer lengths of fibers with strengths of this magnitude and uniformity is extremely important for the production of optical fiber cables.

Molds for production of plastics material boats

Abstract: Molds for the production of fiber reinforced plastics material boat hulls filled with hard foam plastics material are constructed of plastics material and reinforced against deformation by rigid cores and tension bands to accurately shape the hulls even when subjected to high stresses during molding and foam filling. The molds have separable top and bottom halves connected around their peripheries by interfitting flanges forming a seal and also provided with ventilating channels. The outer shell of the bottom mold half between the flanges has a free catenary curve configuration supporting the reinforcing cores for the molding surface or inner shell of the mold.

Buffered optical waveguide fiber

Abstract: A low loss buffered optical waveguide fiber is described. An optical waveguide fiber is coated with a first layer of high modulus material applied to the exterior longitudinal surface thereof. Thereafter, a second layer of low modulus plastic material is disposed over the layer of high modulus material. The ratio R i /R o of the radii of the first and second applied layers is selected to minimize the microbending loss.

Fine structure and mechanical properties of jute differently dried after retting

Abstract: Fine structure, density, and some mechanical properties have been studied in jute fiber dried differently after retting. It is observed that the fiber has a less compact structure before under-going any drying processes after retting. Formation of hydrogen bonding during subsequent drying seems to be the cause of subsequent compactness of the molecules in the fiber.

Method of making thermoplastic resin composite

Abstract: A unidirectional fiber reinforced thermoplastic stock material is prepared by passing fibers through a resin solution to coat the fibers. The coated fibers are treated to remove the solvent and thereafter are consolidated into the desired shape.