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At least 1,063 records · Page 59

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DOE OSTI2024

Distribution of Tritium in the Near Surface of Candidate Structural Materials for Fusion Reactors. Type 304L Stainless Steel, Inconel, Hastelloy, Eurofer-97, Oxide Dispersion-Strengthened Alloy 14YWT

Five different candidate structural materials for fusion have undergone pure tritium gas soaking at room temperature and at 310-mbar(a) pressure. The tritium uptake on the surface and in the bulk of the alloys has been analyzed using surface leaching, chemical etching, and thermal desorption. The nickel-based alloys: Inconel-X-750 and Hastelloy-X, absorbed the least amount of total tritium compared with austenitic stainless steel AISI 304L, reduced activation ferritic-martensitic (RAFM) Eurofer-97, and advanced nanoferritic alloy 14YWT. Microstructural analyses using electron backscatter diffraction (EBSD) indicate that the number of grains and mean grain size is not a dominant factor in near surface tritium uptake. The quantity of iron dissolved in the surface oxide appears to be the major factor in encouraging tritium absorption.

O'Callaghan, James↗

NASA NTRS1967

Materials data handbook, Inconel alloy 718

Materials data handbook on Inconel alloy 718 includes data on the properties of the alloy at cryogenic, ambient, and elevated temperatures and other pertinent engineering information required for the design and fabrication of components and equipment utilizing this alloy.

Sessler, J.↗

NASA NTRS1967

Materials data handbook, aluminum alloy 7075

Materials data handbook on aluminum alloy 7075 includes data on the properties of the alloy at cryogenic, ambient, and elevated temperatures, and other pertinent engineering information required for the design and fabrication of components and equipment utilizing this alloy.

Sessler, J.↗

NASA NTRS1971

Compressive behavior of titanium alloy skin-stiffener specimens selectively reinforced with boron-aluminum composite

A method of selectively reinforcing a conventional titanium airframe structure with unidirectional boron-aluminum composite attached by brazing was successfully demonstrated in compression tests of short skin-stiffener specimens. In a comparison with all-titanium specimens, improvements in structural performance recorded for the composite-reinforced specimens exceeded 25 percent on an equivalent-weight basis over the range from room temperature to 700 K (800 F) in terms of both initial buckling and maximum strengths. Performance at room temperature was not affected by prior exposure at 588 K (600 F) for 1000 hours in air or by 400 thermal cycles between 219 K and 588 K (-65 F and 600 F). The experimental results were generally predictable from existing analytical procedures. No evidence of failure was observed in the braze between the boron-aluminum composite and the titanium alloy.

Herring, H. W.↗

NASA NTRS1971

Hard tissue as a composite material. I - Bounds on the elastic behavior.

Recent determination of the elastic moduli of hydroxyapatite by ultrasonic methods permits a re-examination of the Voigt or parallel model of the elastic behavior of bone, as a two phase composite material. It is shown that such a model alone cannot be used to describe the behavior of bone. Correlative data on the elastic moduli of dentin, enamel and various bone samples indicate the existence of a nonlinear dependence of elastic moduli on composition of hard tissue. Several composite models are used to calculate the bounds on the elastic behavior of these tissues. The limitations of these models are described, and experiments to obtain additional critical data are discussed.

Katz, J. L.↗

NASA NTRS1973

Filament-wound composite vessels material technology

Programs are reviewed that were conducted to establish a technology base for applying advanced fibers or resins to high performance filament-wound pressure vessels for containment of cryogens and high pressure gases. Materials evaluated included boron, graphite, PRD 49-1 and 3/epoxy and S-glass/polyimide composites. Closed-end cylindrical, and oblate spheroid-shaped vessels were fabricated in 4- and 8-inch diameter sizes. Vessels were subjected to single-cycle burst, low-cycle fatigue, and sustained loading tests over a -423 F to room temperature range for epoxy composites and a -423 to 500 F temperature range for the polyimide composites. Vessels tested at cryogenic and/or 500 F had thin (3 to 20 mils) metallic liners whereas vessels tested at room temperature had elastomeric liners. Correlations between acoustic emissions and burst and cyclic properties of PRD 49-1 filament-wound vessels are discussed.

Lark, R. F.↗

NASA NTRS1975

Controlled intermittent interfacial bond concept for composite materials

Concept will enhance fracture resistance of high-strength filamentary composite without degrading its tensile strength or elastic modulus. Concept provides more economical composite systems, tailored for specific applications, and composite materials with mechanical properties, such as tensile strength, fracture strain, and fracture toughness, that can be optimized.

Marston, T. U.↗

NASA NTRS1973

Finite element analysis of a composite material interface

A finite element model of a composite material interface is developed to study the influence of the interface on the thermal strain in the composite. A plane stress model is used with an axisymmetric model as a check. The interface thickness, thermal coefficient, modulus, Poisson's ratio and the percent of mineral in the composite are variables in the study. The results confirmed the usability of the finite element model in studying the polymer-mineral interface.

Murray, K. H.↗

NASA NTRS1975

Space processing of composite materials

Materials and processes for the testing of aluminum-base fiber and particle composites, and of metal foams under extended-time low-g conditions were investigated. A wetting and dispersion technique was developed, based on the theory that under the absence of a gas phase all solids are wetted by liquids. The process is characterized by a high vacuum environment and a high temperature cycle. Successful wetting and dispersion experiments were carried out with sapphire fibers, whiskers and particles, and with fibers of silicon carbide, pyrolytic graphite and tungsten. The developed process and facilities permit the preparation of a precomposite which serves as sample material for flight experiments. Low-g processing consists then merely in the uniform redistribution of the reinforcements during a melting cycle. For the preparation of metal foams, gas generation by means of a thermally decomposing compound was found most adaptable to flight experiments. For flight experiments, the use of compacted mixture of the component materials limits low-g processing to a simple melt cycle.

Steurer, W. H.↗

NASA NTRS1976

A preliminary design study of a laminar flow control wing of composite materials for long range transport aircraft

The results of an aircraft wing design study are reported. The selected study airplane configuration is defined. The suction surface, ducting, and compressor systems are described. Techniques of manufacturing suction surfaces are identified and discussed. A wing box of graphite/epoxy composite is defined. Leading and trailing edge structures of composite construction are described. Control surfaces, engine installation, and landing gear are illustrated and discussed. The preliminary wing design is appraised from the standpoint of manufacturing, weight, operations, and durability. It is concluded that a practical laminar flow control (LFC) wing of composite material can be built, and that such a wing will be lighter than an equivalent metal wing. As a result, a program of suction surface evaluation and other studies of configuration, aerodynamics, structural design and manufacturing, and suction systems are recommended.

Swinford, G. R.↗

NASA NTRS1977

Evaluation of the Tensor Polynomial and Hoffman strength theories for composite materials

The Hoffman theory and the Tensor Polynomial (Tsai-Wu) theory with the stress interaction term set equal to zero have been found to be preferred alternatives to the general Tensor Polynomial theory for predicting strength of filamentary composite laminae. These theories were used to predict failure of off-axis boron/epoxy and E-glass/epoxy test specimens and gave excellent agreement with available experimental results. A numerical experiment was also performed to estimate the errors for ten different composite systems under six different loadings. The maximum error in predicted failure loads among all cases was below 10 percent. These results suggest that the Hoffman failure theory and the Tensor Polynomial theory with the stress interaction term equal to zero can predict failure of practical filamentary composite materials under general biaxial loading with sufficient accuracy for engineering applications.

Narayanaswami, R.↗

NASA NTRS1977

A study of the effects of long-term exposure to fuels and fluids on the behavior of advanced composite materials

The Task 1 (thirty-six-month) and Task 2 (twelve-month) exposure of composite materials to fuel and fluid environments are reported. Narmco T300/5209 (Task 1) shows no significant degradation. Slightly lower mechanical properties were obtained from fuel/water immersion exposure of this material. Kevlar 49/2544 (also Task 1) exhibits significant drop in short-beam shear when exposed to fuel/water immersion. Task 2 materials (T300/5208, Kevlar 49 fabric/5209, and Kevlar 49 fibers) have not shown any significant mechanical property degradation to date.

Hendricks, C. L.↗

NASA NTRS1979

Space radiation effects on composite matrix materials - Analytical approaches

In-vacuo ultraviolet and gamma radiation exposure tests are utilized in a study aimed at the identification of radiation damage mechanisms in composite materials, with the objective of predicting the long-term behavior of composite structures in a space environment at geosynchronous orbit. Physical and chemical methods of polymer characterization are utilized for the study of composite matrix degradation, in conjunction with GC/MS techniques for the analysis of volatile by-products.

Giori, C.↗

NASA NTRS1980

Selected NASA research in composite Materials and structures

Various aspects of the application of composite materials to aircraft structures are considered. Failure prediction techniques, buckling and postbuckling research, laminate fatigue analysis, damage tolerance, high temperature resin matrix composites and electrical hazards of carbon fiber composites are among the topics discussed.

Source record↗

NASA NTRS1982

The structure and properties of rapidly solidified high alloy aluminum materials

A series of 2024 type aluminum alloys modified by additions of 1 to 2% Li were studied to determine the role of the Cu:Li and the (Cu + Mg):Li ratios on resultant strength, ductility, notch-tensile behavior, and crack propagation rates. Ultrasonically gas atomized powders with quench rates of 10 to 100 thousand degrees/s were atomized in an argon atmosphere, producing yields of powder such that almost 100% was finer than 250 microns. The powders are free of gases and porosity, are quite spherical, have few satellites (adhering fine powder particles) and are of uniform microstructure. Strength properties are such that yield strength is 20% greater than for lithium-free 2024 ingot alloy, tensile strength is 10% greater than that of 2024 ingot material, and ductilities are comparable. In terms of specific strength and specific modulus, these RS 2024-Li alloys are significantly better than IM 2024.

Grant, N. J.↗

NASA NTRS1982

Advanced powder metallurgy aluminum alloys and composites

The differences between powder and ingot metallurgy processing of aluminum alloys are outlined. The potential payoff in the use of advanced powder metallurgy (PM) aluminum alloys in future transport aircraft is indicated. The national program to bring this technology to commercial fruition and the NASA Langley Research Center role in this program are briefly outlined. Some initial results of research in 2000-series PM alloys and composites that highlight the property improvements possible are given.

W. B. Lisagor↗

NASA NTRS1982

Strength criteria for composite materials (a literature survey)

Literature concerning strength (failure) criteria for composite materials is reviewed with emphasis on phenomenological failure criteria. These criteria are primarily intended to give a good estimation of the safety margin with respect to failure for arbitrary multiaxial stress states. The failure criteria do not indicate the types of fracture that will occur in the material. The collection of failure criteria is evaluated for applicability for the glass reinforced plastics used in mine detectors. Material tests necessary to determine the parameters in the failure criteria are discussed.

Roode, F.↗

NASA NTRS1983

Composite structural materials

Progress and plans are reported for investigations of: (1) the mechanical properties of high performance carbon fibers; (2) fatigue in composite materials; (3) moisture and temperature effects on the mechanical properties of graphite-epoxy laminates; (4) the theory of inhomogeneous swelling in epoxy resin; (5) numerical studies of the micromechanics of composite fracture; (6) free edge failures of composite laminates; (7) analysis of unbalanced laminates; (8) compact lug design; (9) quantification of Saint-Venant's principles for a general prismatic member; (10) variation of resin properties through the thickness of cured samples; and (11) the wing fuselage ensemble of the RP-1 and RP-2 sailplanes.

Ansell, G. S.↗