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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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At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

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.↗
NASA NTRS1982

Materials processing in space

Processing-refining of raw materials from extraterrestrial sources is detailed for a space materials handling facility. The discussion is constrained to those steps necessary to separate desired components from raw or altered input ores, semi-purified feedstocks, or process scrap and convert the material into elements, alloys, and consumables. The materials are regarded as originating from dead satellites and boosters, lunar materials, and asteroids. Strong attention will be given to recycling reagent substances to avoid the necessity of transporting replacements. It is assumed that since no aqueous processes exist on the moon, the distribution of minerals will be homogeneous. The processing-refining scenario will include hydrochemical, pyrochemical, electrochemical, and physical techniques selected for the output mass rate/unit plant mass ratio. Flow charts of the various materials processing operations which could be performed with lunar materials are provided, noting the necessity of delivering several alloying elements from the earth due to scarcities on the moon.

Waldron, R. D.↗
NASA NTRS1984

Exposure to space radiation of high-performance infrared multilayer filters and materials technology experiments (A0056)

Infrared multilayer interface filter which were used in satellite radiometers were examined. The ability of the filters to withstand the space environment in these applications is critical. An experiment on the LDEF subjects the filters to authoritative spectral measurements following space exposure to ascertain their suitability for spacecraft use and to permit an understanding of degradation mechanisms. The understanding of the effects of prolonged space exposure on spacecraft materials, surface finishes, and adhesive systems is important to the spacecraft designer. Materials technology experiments and experiment on infrared multilayer filters are discussed.

Seeley, J. S.↗
NASA NTRS1984

Forecasting of high voltage insulation performance: Testing of recommended potting materials and of capacitors

Nondestructive high voltage test techniques (mostly electrical methods) are studied to prevent total or catastrophic breakdown of insulation systems under applied high voltage in space. Emphasis is on the phenomenon of partial breakdown or partial discharge (P.D.) as a symptom of insulation quality, notably partial discharge testing under D.C. applied voltage. Many of the electronic parts and high voltage instruments in space experience D.C. applied stress in service, and application of A.C. voltage to any portion thereof would be prohibited. Suggestions include: investigation of the ramp test method for D.C. partial discharge measurements; testing of actual flight-type insulation specimen; perfect plotting resin samples with controlled defects for test; several types of plotting resins and recommendations of the better ones from the electrical characteristics; thermal and elastic properties are also considered; testing of commercial capaciters; and approximate acceptance/rejection/rerating criteria for sample test elements for space use, based on D.C. partial discharge.

Bever, R. S.↗
NASA NTRS1984

High temperature performance of flexible thermal protection materials

Aero convective tests of several flexible thermal protection system (FTPS) concepts were conducted in the NASA Ames Research Center 20 MW arcjet aero heating wind tunnel. The concepts consisted of quilted insulation blankets with nextel AB312 felt insulation stitched between cover cloths with AB312 thread. The cover cloths were commercially available nextel AB312 and nicalon fabrics. The specimens were subjected to convective heat fluxes ranging from 7 to 35 Btu/per sq ft per sec at stagnation pressures of .005 to .02 atm. Specimens were tested both with and without transpiration cooling. Results indicated that both the nextel and nicalon fabrics offer the potential for higher temperature applications than current FTPS, and nicalon appears to be capable of withstanding temperatures well above 2500 degrees F with minimal degradation.

Savage, R. T.↗
NASA NTRS1984

Geobotanical discrimination of ultramafic parent materials An evaluation of remote sensing techniques

Color and color infrared aerial photography and imagery acquired from a Daedalus DEI-1260 multispectral airborne scanner were employed in an investigation to discriminate ultramafic rock types in a test site in southwest Oregon. An analysis of the relationships between vegetation characteristics and parent materials was performed using a vegetation classification and map developed for the project, lithologic information derived from published geologic maps of the region, and terrain information gathered in the field. Several analytical methods, including visual image analysis, band ratioing, principal components analysis, and contrast enhancement and subsequent color composite generation were used in the investigation. There was a close correspondence between vegetation types and major rock types. These were readily discriminated by the remote sensing techniques. It was found that ultramafic rock types were separable from non-ultramafic rock types and serpentine was distinguishable from non-serpentinized peridotite. Further investigations involving spectroradiometric and digital classification techniques are being performed to further identify rock types and to discriminate chromium and nickel-bearing rock types.

Mouat, D. A.↗
NASA NTRS1985

Adhesive evaluation of LARC-TPI and a water-soluble version of LARC-TPI

The results of a study to evaluate two Langley Research Center thermoplastic polimide (TPI) materials, identified as TPI/MTC for the material from Mitsui Toatsu Chemicals Inc. and TPI/H2O for the material from United Technologies Research Center, as high temperature thermoplastic adhesives and primers for bonding titanium (6AL-4V) adherends are discussed. A limited characterization of the materials was performed using a Diffuse Reflectance-Fourier Transform Infrared Spectroscopy (DR-FTIR) technique. Thermomechanical Analysis (TMA) and torsional braid techniques were used to determine glass transition temperature. The adhesive's strength, as determined by simple lap shear tests, as used to evaluate the effects of long term thermal exposure (up to 1000 hrs) at 204 deg C and a 72-hour water-boil.

Progar, D. J.↗
NASA NTRS1984

Predicting electrochemical breakdown in terrestrial photovoltaic modules

Electrochemical corrosion of PV cells can cause a cell-to-frame short circuit with two undesirable resuits: (1) catastrophic loss of source-circuit power; and (2) high field maintenance (module replacement) costs. Parameter dependencies are determined and encapsulated two-cell coupons are exposed to a range of voltage differences, temperatures, and relative humidities. Material relative performance is assessed. Nine different metallization-encapsulation combinations are tested.

Mon, G. R.↗
NASA NTRS1985

Acetylene terminated matrix resins

The synthesis of resins with terminal acetylene groups has provided a promising technology to yield high performance structural materials. Because these resins cure through an addition reaction, no volatile by-products are produced during the processing. The cured products have high thermal stability and good properties retention after exposure to humidity. Resins with a wide variety of different chemical structures between the terminal acetylene groups are synthesized and their mechanical properties studied. The ability of the acetylene cured polymers to give good mechanical properties is demonstrated by the resins with quinoxaline structures. Processibility of these resins can be manipulated by varying the chain length between the acetylene groups or by blending in different amounts of reactive deluents. Processing conditions similar to the state-of-the-art epoxy can be attained by using backbone structures like ether-sulfone or bis-phenol-A. The wide range of mechanical properties and processing conditions attainable by this class of resins should allow them to be used in a wide variety of applications.

Goldfarb, I. J.↗
NASA NTRS1985

Mechanical properties testing of candidate polymer matrix materials for use in high performance composites

The mechanical properties of four candidate neat resin systems for use in graphite/epoxy composites are characterized. This includes tensile and shear stiffnesses and strengths, coefficients of thermal and moisture expansion, and fracture toughness. Tests are conducted on specimens in the dry state and moisture-saturated, at temperatures of 23C, 82C and 121C. The neat resins tested are Hexcel HX-1504, Narmco 5245-C, American Cyanamid CYCOM 907, and Union Carbide ERX-4901A (MDA). Results are compared with those obtained for four other epoxy resins tested in a prior program, i.e., Hercules 3502, 2220-1, and 2220-3, and Ciba-Geigy Fibredux 914, as well as with available Hercules 3501-6 data. Scanning electron microscopic examination of fracture surfaces is performed to permit the correlation of observed failure modes with the environmental test conditions. A finite element micromechanics analysis is used to predict unidirectional composite response under various test conditions, using the measured neat resin properties as input data.

Zimmerman, R. S.↗
NASA NTRS1985

Tethers for Mars space operations

A tether-mediated transport system is proposed in which mass may be transferred between the Martian surface, Mars orbit, and open space, using the orbital momentum of Phobos and Deimos. The performance and materials strength requirements of a prototype tether system are studied with attention given to: tether dynamics effects during different stages of operation; micrometeoroid impact effects; replacement of tether segments; and contingency methods in case of tether failure. A schematic diagram of the proposed tether transportation system is provided.

Penzo, P. A.↗
NASA NTRS1986

Adhesive evaluation of LARC-TPI and a water-soluble version of LARC-TPI

The results of a study to evaluate two Langley Research Center thermoplastic polimide (TPI) materials, identified as TPI/MTC for the material from Mitsui Toatsu Chemicals Inc. and TPI/H2O for the material from United Technologies Research Center, as high temperature thermoplastic adhesives and primers for bonding titanium (6AL-4V) adherends are discussed. A limited characterization of the materials was performed using a Diffuse Reflectance-Fourier Transform Infrared Spectroscopy (DR-FTIR) technique. Thermomechanical Analysis (TMA) and torsional braid techniques were used to determine glass transition temperature. The adhesive's strength, as determined by simple lap shear tests, was used to evaluate the effects of long term thermal exposure (up to 1000 hrs) at 204 deg C and a 72-hour water-boil.

Progar, D. J.↗
NASA NTRS1985

Preliminary results of SMM exposed aluminized Kapton and silvered Teflon

Early Space Shuttle flights revealed that organic materials, such as those used in thermal control blankets and paints in the payload bay, were adversely affected in the low Earth orbit environment. Examination of eroded surfaces on these early flights and materials experiments performed on subsequent flights led to the conclusion that atomic oxygen present at Shuttle operating altitudes was responsible for surface degradation. The Solar Maximum Mission provided surfaces that had been exposed in real time to atomic oxygen and ultraviolet radiation. Preliminary results of studies of the microscopic surface effects on silvered Teflon and aluminized Kapton used for thermal control on the Solar Maximum Mission are presented.

Santos-Mason, B.↗
NASA NTRS1989

Acetylene-Terminated Aspartimides And Derived Resins

New polymers and derived blends exhibit improved processability and properties. New toughened epoxies exhibit excellent properties, but use temperatures limited. Bismaleimide resins are some base materials formulated to develop materials having moderate use temperatures. Work conducted on use of acetylenic (ethynyl) group to cross-link and extend chains of oligomers and polymers to obtain materials to perform at higher temperatures. Extended to include acetylene-terminated aspartimides (ATA's).

Hergenrother, Paul M.↗
NASA NTRS1989

Strain energy release rate as a function of temperature and preloading history utilizing the edge delamination fatique test method

Static laminate and tension-tension fatigue tests of IM7/8551-7 composite materials was performed. The Edge Delamination Test (EDT) was utilized to evaluate the temperature and preloading history effect on the critical strain energy release rate. Static and fatigue testing was performed at room temperature and 180 F (82 C). Three preloading schemes were used to precondition fatigue test specimens prior to performing the normal tension-tension fatigue EDT testing. Computer software was written to perform all fatigue testing while monitoring the dynamic modulus to detect the onset of delamination and record the test information for later retrieval and reduction.

Zimmerman, Richard S.↗
NASA NTRS1988

Global/local finite element analysis of composite materials

The motivation for performing global/local finite element analysis in composite materials is described. An example of such an analysis of a composite plate with a central circular hole is presented. Deformed finite element grids and interlaminar normal stress distributions are presented to aid understanding of the plate response. Such distribution at the plate edge is shown to be basically unaffected, although transverse displacements of the edge were slightly different from an analysis of a similar plate with no hole.

Griffin, O. Hayden, Jr.↗
NASA NTRS1990

Ethynyl-Terminated Imidothioethers And Derived Resins

New toughened epoxies exhibit excellent properties, but temperatures at which used limited. Bismaleimide resins some of base materials being formulated to develop materials used at moderate temperatures. Work conducted on use of acetylenic (ethynyl) group to cross-link and extend chains of oligomers and polymers to obtain materials that perform at high temperatures. Work extended to ethynyl-terminated imidothioethers (ETI's). Tested primarily as adhesives and composite matrices and found to have useful properties in terms of processing, resistance to high temperature, fracture toughness, and resistance to solvents. Also have desirable mechanical properties. Potentially useful for aerospace and nonaerospace applications.

Hergenrother, Paul M.↗
NASA NTRS1991

Glass formation and crystallization in high-temperature glass-ceramics and Si3N4

The softening of glassy grain boundaries in ceramic matrix composites and Si3N4 at high temperatures reduces mechanical strength and the upper-use temperature. By crystallizing this glass to a more refractory crystalline phase, a material which performs at higher temperatures may result. Three systems were examined: a cordierite composition with ZrO2 as a nucleating agent; celsian compositions; and yttrium silicate glasses both in bulk and intergranular in Si3N4. For the cordierite compositions, a series of metastable phases was obtained. The crystallization of these compositions was summarized in terms of metastable ternary isothermal sections. Zircon formed at the expense of ZrO2 and spinel. In SiC composites, the transformations were slower. In celsian, two polymorphs were crystallized. One phase, hexacelsian, which always crystallized, even when metastable, had an undesirable volume change. The other phase, celsian, was very difficult to crystallize. In yttrium silicate bulk glasses, similar in composition to the intergranular glass in Si3N4, a number of polymorphs of Y2Si2O7 were crystallized. The conditions under which these polymorphs formed are compared with crystallization in Si3N4.

Drummond, Charles H., III↗