Elevated-temperature tensile properties of tungsten fiber composites.
Elevated temperature tensile properties of copper alloy-tungsten fiber-reinforced composites
COPPER ALLOY↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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A procedure for rapid computation of equilibrium chemical composition and thermodynamic properties of the generalized argon-nitrogen-oxygen-hydrogen gas system
Rapid computation of equilibrium, chemical composition, and thermodynamic properties of argon-oxygen-hydrogen gas system
Mascitti, V. R.↗
Interfacial Effects on the Thermal and Mechanical Properties of Graphite/Copper Composites
Graphite surfaces are not wet by pure copper. This lack of wetting has been responsible for a debonding phenomenon that has been found in continuous graphite fiber reinforced copper matrix composites subjected to elevated temperatures. By suitably alloying copper, its ability to wet graphite surfaces can be enhanced. Information obtained during sessile drop testing has led to the development of a copper-chromium alloy that suitably wets graphite. Unidirectionally reinforced graphite/copper composites have been fabricated using a pressure infiltration casting procedure. P100 pitch-based fibers have been used to reinforce copper and copper-chromium alloys. X-ray radiography and optical microscopy have been used to assess the fiber distribution in the cast composites. Scanning electron microscopy and Auger electron spectroscopy analyses were conducted to study the distribution and continuity of the chromium carbide reaction phase that forms at the fiber/matrix interface in the alloyed matrix composites. The effects of the chromium in the copper matrix on the mechanical and thermal properties of P100Gr/Cu composites have been evaluated through tensile testing, three-point bend testing, thermal cycling and thermal conductivity calculations. The addition of chromium has resulted in an increased shear modulus and essentially zero thermal expansion in the P100Gr/Cu-xCr composites through enhanced fiber/matrix bonding. The composites have longitudinal tensile strengths in excess of 700 MPa with elastic moduli of 393 GPa. After 100 hr at 760 deg C 84 percent of the as-cast strength is retained in the alloyed matrix composites. The elastic moduli are unchanged by the thermal exposure. It has been found that problems with spreading of the fiber tows strongly affect the long transverse tensile properties and the short transverse thermal conductivity of the P100Gr/Cu-xCr composites. The long transverse tensile strength is limited by rows of touching fibers which are paths of easy crack propagation under low tensile loads. The short transverse thermal conductivity is dictated by the fiber/matrix interface. Conduction across this interface has been estimated to be two orders of magnitude lower than that across the composite. This is due to the mechanical, and not chemical, nature of Gr/Cu bond.
Devincent, Sandra Marie↗
A Subsurface Soil Composition and Physical Properties Experiment to Address Mars Regolith Stratigraphy
Previous in-situ measurements of soil-like materials on the surface of Mars, in particular during the on-going Mars Exploration Rover missions, have shown complex relationships between composition, exposure to the surface environment, texture, and local rocks. In particular, a diversity in both compositional and physical properties could be established that is interpreted to be diagnostic of the complex geologic history of the martian surface layer. Physical and chemical properties vary laterally and vertically, providing insight into the composition of rocks from which soils derive, and environmental conditions that led to soil formation. They are central to understanding whether habitable environments existed on Mars in the distant past. An instrument the Mole for Soil Compositional Studies and Sampling (MOCSS) - is proposed to allow repeated access to subsurface regolith on Mars to depths of up to 1.5 meters for in-situ measurements of elemental composition and of physical and thermophysical properties, as well as for subsurface sample acquisition. MOCSS is based on the compact PLUTO (PLanetary Underground TOol) Mole system developed for the Beagle 2 lander and incorporates a small X-ray fluorescence spectrometer within the Mole which is a new development. Overall MOCSS mass is approximately 1.4 kilograms. Taken together, the MOCSS science data support to decipher the geologic history at the landing site as compositional and textural stratigraphy if they exist - can be detected at a number of places if the MOCSS were accommodated on a rover such as MSL. Based on uncovered stratigraphy, the regional sequence of depositional and erosional styles can be constrained which has an impact on understanding the ancient history of the Martian near-surface layer, considering estimates of Mars soil production rates of 0.5... 1.0 meters per billion years on the one hand and Mole subsurface access capability of approximately 1.5 meters. An overview of the MOCSS, XRS instrument accomodation and the impact that these instruments have on Mars science is discussed.
Richter, L.↗
Effects of fiber/matrix interactions on the properties of graphite/epoxy composites
A state-of-the-art literature review of the interactions between fibers and resin within graphite epoxy composite materials was performed. Emphasis centered on: adhesion theory; wetting characteristics of carbon fiber; load transfer mechanisms; methods to evaluate and measure interfacial bond strengths; environmental influence at the interface; and the effect of the interface/interphase on composite performance, with particular attention to impact toughness. In conjunction with the literature review, efforts were made to design experiments to study the wetting behavior of carbon fibers with various finish variants and their effect on adhesion joint strength. The properties of composites with various fiber finishes were measured and compared to the base-line properties of a control. It was shown that by tailoring the interphase properties, a 30% increase in impact toughness was achieved without loss of mechanical properties at both room and elevated temperatures.
Mcmahon, P. E.↗
Influence of Constituents on Creep Properties of SiC/SiC Composites
SiC-SiC composites are being considered as potential candidate materials for next generation turbine components such as combustor liners, nozzle vanes and blades because of their low density, high temperature capability, and tailorable mechanical properties. These composites are essentially fabricated by infiltrating matrix into a stacked array of fibers or fiber preform by one or a combination of manufacturing methods such as, Melt Infiltration (MI) of molten silicon metal, Chemical Vapor Infiltration (CVI), Polymer Infiltration and Pyrolysis (PIP). To understand the influence of constituents, the SiC-SiC composites fabricated by MI, CVI, and PIP methods were creep tested in air between 12000 and 14500 degrees Centigrade for up to 500 hours. The failed specimens were analyzed under a scanning electron microscope to assess damage mechanisms. Also, knowing the creep deformation parameters of the fiber and the matrix under the testing conditions, the creep behavior of the composites was modeled and compared with the measured data. The implications of the results on the long term durability of these composites will be discussed.
modeling↗
Shaped glass fibers.
Solid and hollow noncylindrical glass fibers fabrication for reinforced plastics, discussing composites properties and advantages
Humphrey, R. A.↗
Metal carbide-graphite composites
Tungsten used in NbC-C composites as low melting densification additive to improve composite properties and lower fabrication temperatures
Harada, Y.↗
Analytical ultracentrifuge services and research Final report
Physicochemical properties, composition and ribosome characterization of biological materials using ultracentrifugation and electron microscopy
Chao, F.-C.↗
Vacuum melting and casting of superalloys
Composition, properties, and applications of superalloys and techniques for vacuum melting and vacuum casting procedures
Alexander, C. A.↗
Phenylquinoxaline copolymers
The preparation of a series of homopolymers and block and random type phenylquinoxaline copolymers is described together with their important characteristics and preliminary measurements of composite properties. Phenylquinoxaline homopolymers consisting of low, intermediate, and high molecular weight versions were prepared from the reaction of 3,3'-diaminobenzidine (DAB) and 3,3',4,4'-tetraaminobenzophenone (TAB), each with p-bis(phenylglyoxalyl)benzene as solutions (18% solids content) in a 1:1 mixture of m-cresol and xylene. Three random and three block copolymers were prepared from the reaction of various amounts of DAB and TAB with p-bis(phenylglyoxalyl)benzene. The copolymers were prepared with DAB to TAB distribution ratios of 3:1, 1:1, and 1:3. The work was performed primarily to determine if phenylquinoxaline copolymers exhibit any advantage over the homopolymers for use as functional or structural resins, especially as a matrix material in combination with a high-modulus graphite fiber reinforcement.
Hergenrother, P. M.↗
Shortgrass prairie spectral measurements
The spectral methods of vegetation analysis not only measure herbage biomass on a nondestructive basis but also can be adapted to aircraft and satellite devices to map the spatial distribution over an area in an efficient and economical fashion. This study reviews the ground-based in situ field spectrometry in the 0.350-0.800 micron region of the spectrum. A statistical analysis of in situ spectroreflectance data from sample plots of the shortgrass prairie shows that green biomass, chlorophyll concentration, and leaf water content are directly interrelated to that composite property of the plot which is called functioning green biomass. Spectrocorrelation data indicate the spectral regions of optimum sensitivity for a remote estimation of the green biomass, chlorophyll, and leaf water content. The near-infrared region of the spectrum shows a high positive spectrocorrelation to these three sample parameters, regardless of the amount of standing dead vegetation.
Tucker, C. J.↗
Colloquium on Planetary Satellites, 28th, Cornell University, Ithaca, N.Y., August 18-21, 1974, Proceedings
The papers consider the orbits, physical properties, composition, origin, and evolution of the natural satellites of the solar system from the viewpoint of celestial mechanics. Topics include a computer technique for developing analytic expressions for the coordinates and partial derivatives of Jupiter's Galilean satellites, a theory of the motion of the Galilean satellites, a comparison between photographic observations of the positions of the Galilean satellites and Sampson's tables, astrolabe observations of several transits of the Galilean satellites, the orbital resonance among the Galilean satellites, the motion of the Martian satellites from ground-based observations and Mariner-9 TV data, and a general method for predicting eclipses of natural planetary satellites. Individual items are announced in this issue.
Burns, J. A.↗
Brazed boron-silicon carbide/aluminum structural panels
Fluxless brazing process minimizes degradation of mechanical properties composite material of silicon carbide coated boron fibers in an aluminum matrix. Process is being used to fabricate full-scale Boron-Silicon Carbide/Aluminum-Titanium honeycomb core panels for flight testing and ground testing.
Arnold, W. E., Jr.↗
Stability of PMR-polyimide monomer solutions
The stability of alcohol solutions of norborneyl capped PMR-polyimide resins was monitored during storage at ambient and subambient temperatures. Chemical changes during storage were determined spectroscopically using nuclear magnetic resonance. Resin processability and cured resin quality were determined by fabrication of unidirectional, graphite fiber composites using aged solutions and testing of selected composite properties. PMR-15 solutions exhibit nominally two weeks of useful life and PMR-2 solutions exhibit nominally two days of useful life at ambient conditions. The limiting factor is precipitation of imide reaction produces from the monomer solutions. Both solutions exhibit substantially longer useful lifetimes in subambient storage. PMR-15 shows no precipitation after several months storage at subambient temperatures. PMR-2 solutions do exhibit precipitates after extended subambient storage, however, the precipitates formed under these conditions can be redissolved. The chemical implications of these observations are discussed.
Lauver, R. W.↗
Recent developments in PMR polyimides at NASA Lewis
The following areas of PMR polyimide research were reviewed: (1) prepreg tack and drape; (2) cure temperature; (3) solution characterization; and (4) elevated temperature composite properties. Recent hardware applications of PMR-15 by various fabricators were also reviewed.
Serafini, T. T.↗
High char yield epoxy curing agents
Class of imide-amine curing agents preserves structural integrity, prevents fiber release, and is fully compatible with conventional epoxy resins; agents do not detract from composite properties while greatly reducing char yield. Materials utilizing curing are used in aerospace, automotive, and other structural components where deterioration must be minimized and fiber release avoided in event of fire.
Delvigs, P.↗
Second generation PMR polyimide/fiber composites
A second generation polymerization monomeric reactants (PMR) polyimdes matrix system (PMR 2) was characterized in both neat resin and composite form with two different graphite fiber reinforcements. Three different formulated molecular weight levels of laboratory prepared PMR 2 were examined, in addition to a purchased experimental fully formulated PMR 2 precurser solution. Isothermal aging of graphite fibers, neat resin samples and composite specimens in air at 316 C were investigated. Humidity exposures at 65 C and 97 percent relative humidity were conducted for both neat resin and composites for eight day periods. Anaerobic char of neat resin and fire testing of composites were conducted with PMR 15, PMR 2, and an epoxy system. Composites were fire tested on a burner rig developed for this program. Results indicate that neat PMR 2 resins exhibit excellent isothermal resistance and that PMR 2 composite properties appear to be influenced by the thermo-oxidative stability of the reinforcing fiber.
Cavano, P. J.↗