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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Thermoplastic coating of carbon fibers

A continuous powder coating system was developed for coating carbon fiber with LaRC-TPI (Langley Research Center-Thermoplastic Polyimide), a high-temperature thermoplastic polymide invented by NASA-Langley. The coating line developed used a pneumatic fiber spreader to separate the individual fibers. The polymer was applied within a recirculating powder coating chamber then melted using a combination of direct electrical resistance and convective heating to make it adhere to the fiber tow. The tension and speed of the line were controlled with a dancer arm and an electrically driven fiber wind-up and wind-off. The effects of heating during the coating process on the flexibility of the prepreg produced were investigated. The uniformity with which the fiber tow could be coated with polymer also was examined. Composite specimens were fabricated from the prepreg and tested to determine optimum process conditions. The study showed that a very uniform and flexible prepeg with up to 50 percent by volume polymer could be produced with this powder coating system. The coating line minimized powder loss and produced prepeg in lengths of up to 300 m. The fiber spreading was found to have a major effect on the coating uniformity and flexibility. Though test results showed low composite tensile strengths, analysis of fracture surfaces under scanning electron microscope indicated that fiber/matrix adhesion was adequate.

Edie, D. D.↗
NASA NTRS1988

Capture of an olivine micrometeoroid by spacecraft in low-earth orbit

Particulates associated with an impact feature in the solar maximum satellite MEB thermal control blanket are identified as magnesium-rich, Mg/Mg + Fe(2+) = 0.66 - 0.83, olivine and confirm that the impact feature was caused by an olivine micrometeoroid. At a relative impact velocity of about 7 km/s a considerable portion of the micrometeoroid was lost due to back splattering. Analytical electron microscope analysis of recovered particulates shows several degrees of mineralogical and chemical degradation such as mechanical fragmentation, melting, loss of sulfur and iron, and formation of Fe, Ni grains. The results indicate that recovery of information is sufficient to establish the character of the impacted micrometeoroid.

Rietmeijer, Frans J. M.↗
NASA NTRS1988

Fatigue crack closure behavior at high stress ratios

Fatigue crack delay behavior at high stress ratio caused by single peak overloads was investigated in two thicknesses of 7475-T731 aluminum alloy. Closure measurements indicated no closure occurred before or throughout the overload plastic zones following the overload. This was further substantiated by comparing the specimen compliance following the overload with the compliance of a low R ratio test when the crack was fully open. Scanning electron microscope studies revealed that crack tunneling and possibly reinitiation of the crack occurred, most likely a result of crack-tip blunting. The number of delay cycles was greater for the thinner mixed mode stress state specimen than for the thicker plane strain stress state specimen, which is similar to low R ratio test results and may be due to a larger plastic zone for the mixed mode cased.

Turner, C. Christopher↗
NASA NTRS1989

Ordering in the Fe-Ni system under electron irradiation

The disorder-order transformation was generated in a range of Fe-Ni alloys using 1 MeV electrons in a high voltage electron microscope. The experimental factors that influence the occurrence of the transformation were determined, and the critical disordering temperature, Tc, was determined as a function of composition. It was demonstrated that the irradiation enhanced the ordering reaction kinetics. A metastable, ordered phase transformation was not induced. From the results, it is possible to deduce new information about the Fe-Ni phase diagram below 350 C.

Reuter, K. B.↗
NASA NTRS1989

A study of the effects of prolonged simulated microgravity on the musculature of the lower extremities in man - An introduction

The experimental approach and the protocol are described for a study designed to investigate the effect of prolonged microgravity (simulated by a continuous exposure of subjects to 30-d-long 6-deg headdown tilt) on the musculature of the lower extremities in humans. The objectives of this study are as follows: (1) to determine changes in the functional characteristics of knee joint flexor and extensor muscle group; (2) to examine changes in the histochemical, biochemical, electron microscopic, and computed tomographic characteristics of skeletal muscle; (3) to determine if functional characteristics of skeletal muscle would be normalized four weeks after the bedrest; and (4) to compare these results to those of spaceflight. Percutaneous muscle biopsy, computed tomography, anthropometry, and in vivo muscle strength measurements are to be used to assess mechanical, structural, and metabolic characteristics of skeletal muscle.

Buchanan, Paul↗
NASA NTRS1988

Fatigue crack growth behavior of a single crystal alloy as observed through an in situ fatigue loading stage

An in situ fatigue loading stage inside a scanning electron microscope (SEM) was used to determine the fatigue crack growth behavior of a PWA 1480 single-crystal nickel-based superalloy. The loading stage permits real-time viewing of the fatigue damage processes at high magnification. The PWA 1480 single-crystal, single-edge notch specimens were tested with the load axis parallel to the (100) orientation. Two distinct fatigue failure mechanisms were identified. The crack growth rate differed substantially when the failure occurred on a single slip system in comparison to multislip system failure. Two processes by which crack branching is produced were identified and are discussed. Also discussed are the observed crack closure mechanisms.

Telesman, Jack↗
NASA NTRS1989

Microlesions - Theory and reality

Efforts to assess radiation risk in space have been complicated by the considerable unknowns regarding the biological effects of the heavy ion component (HZE particles) of the cosmic rays. The attention has focused primarily on the assignation of a quality factor (Q) which would take into account the greater effectiveness of heavy ions vis-a-vis other forms of ionizing radiation. If, however, as the so-called 'microlesion theory' allows, the passage of HZE particles through living tissue produces unique biological damage, the traditional use of Q becomes meaningless. Therefore, it is critical to determine if microlesions, in fact, do exist. While the concept does not necessarily require detectable morphological damage, 'tunnel-lesions' or holes in ocular tissues have been cited as evidence of microlesions. These data, however, are open to reinterpretation. Ongoing light, scanning and transmission electron microscopic studies of the corneas, lenses and retinas of rat eyes exposed to 450 MeV/amu Fe-56 ions thus far have not revealed tunnel-lesion damage. The morphological effects of the heavy ions have been found to be qualitatively similar to the changes following other kinds of ionizing radiation.

Worgul, Basil V.↗
NASA NTRS1989

Research and test facilities for development of technologies and experiments with commercial applications

One of NASA'S agency-wide goals is the commercial development of space. To further this goal NASA is implementing a policy whereby U.S. firms are encouraged to utilize NASA facilities to develop and test concepts having commercial potential. Goddard, in keeping with this policy, will make the facilities and capabilities described in this document available to private entities at a reduced cost and on a noninterference basis with internal NASA programs. Some of these facilities include: (1) the Vibration Test Facility; (2) the Battery Test Facility; (3) the Large Area Pulsed Solar Simulator Facility; (4) the High Voltage Testing Facility; (5) the Magnetic Field Component Test Facility; (6) the Spacecraft Magnetic Test Facility; (7) the High Capacity Centrifuge Facility; (8) the Acoustic Test Facility; (9) the Electromagnetic Interference Test Facility; (10) the Space Simulation Test Facility; (11) the Static/Dynamic Balance Facility; (12) the High Speed Centrifuge Facility; (13) the Optical Thin Film Deposition Facility; (14) the Gold Plating Facility; (15) the Paint Formulation and Application Laboratory; (16) the Propulsion Research Laboratory; (17) the Wallops Range Facility; (18) the Optical Instrument Assembly and Test Facility; (19) the Massively Parallel Processor Facility; (20) the X-Ray Diffraction and Scanning Auger Microscopy/Spectroscopy Laboratory; (21) the Parts Analysis Laboratory; (22) the Radiation Test Facility; (23) the Ainsworth Vacuum Balance Facility; (24) the Metallography Laboratory; (25) the Scanning Electron Microscope Laboratory; (26) the Organic Analysis Laboratory; (27) the Outgassing Test Facility; and (28) the Fatigue, Fracture Mechanics and Mechanical Testing Laboratory.

Source record↗
NASA NTRS1990

TiCl4 as a source of TiO2 particles for laser anemometry measurements in hot gas

A method of reacting TiCl4 with water saturated gaseous nitrogen (GN2) at the entrance into a high temperature gas flow is described. The TiO2 particles formed are then entrained in the gas flow and used as seed particles for making laser anemometry (LA) measurements of the flow velocity distribution in the hot gas. Scanning electron microscope photographs of the TiO2 particles are shown. Data rate of the LA processor was measured to determine the amount of TiO2 formed. The TiCl4 and mixing gas flow diagram is shown. This work was performed in an open jet burner.

Weikle, Donald H.↗
NASA NTRS1988

Pultrusion Process Development for Long Space Boom Model

Long flexible-boom models were required to develop ground-vibration test methods for very-low-frequency space structures with applications to the proposed Space Station. Pultruded quasi-isotropic composite beams were selected as an option over extruded aluminum alloy structures because of the lower cost potential, the higher specific strength, the flexural properties, and the dynamic similarity considerations. The reinforcement material that was used was biaxial (0 deg/90 deg) fiberglass roving held in place with knitted polyester yarn such that equal fiber volume in 0 deg and 90 deg orientations provided nearly equal strength in both longitudinal and transverse directions. An isophthalic polyester resin system was used as the matrix. Continuous lengths up to 270 ft were easily pultruded with biaxial fabric. Tracking problems were encountered with similar unidirectional fabrics. Analyses of processing problems were conducted to determine causes for delamination, scaling, and sloughing. Ultrasonic C-scanning and scanning electron microscope examinations were conducted as well as mechanical testing to failure. Test results indicate that pultrusion processes can be used to produce quasi-isotropic composite structures.

Wilson, Maywood L.↗
NASA NTRS1989

Fatigue crack growth in a unidirectional SCS-6/Ti-15-3 composite

An investigation was conducted to characterize and model the fatigue crack growth (FCG) behavior of a SCS-6/Ti-15-3 metal matrix composite. Part of the study was conducted using a fatigue loading stage mounted inside a scanning electron microscope (SEM). This unique facility allowed high magnification viewing of the composite fatigue processes and measurement of the near crack tip displacements. The unidirectional composite was tested in the (0)8 (i.e., longitudinal) and (90)8 (i.e., transverse) orientations. For comparison purposes unreinforced matrix material produced by the identical process as the reinforced material was also tested. The results of the study reveal that the fatigue crack growth behavior of the composite is a function of specimen geometry, fiber orientation and the interaction of local stress fields with the highly anisotropic composite. In the case of (0)8 oriented single edge notch (SEN) specimens and (90)8 oriented compact tension (CT) specimens, the crack growth was normal to the loading direction. However, for the (0)8 CT specimens the crack grew mostly parallel to the loading and the fiber direction. The unusual fatigue behavior of the (0)8 CT specimens was attributed to the specimen geometry and the associated high tensile bending stresses perpendicular to the fiber direction. These stresses resulted in preferential cracking in the weak interface region perpendicular to the fiber direction. The interface region, and in particular the carbon coating surrounding the fiber proved to be the composites weakest link. In the (0)8 SEN the crack growth was confined to the matrix leaving behind unbroken fibers which bridged the cracked surfaces. As the crack grew longer, more fibers bridged the crack resulting in a progressive decrease in the crack growth rates and eventual crack arrest. The actual near crack tip displacement measurements were used in a proposed formulation for a bridging-corrected effective crack driving force, delta K(sub eff). This parameter was able to account for most of the experienced bridging and correlated the (0)8 SEN fatigue crack growth data reasonably well.

Kantzos, Peter↗
NASA NTRS1990

Experiment K-6-01. Distribution and biochemistry of mineral and matrix in the femurs of rats

Previous analyses of the composition of mineral and matrix in the bone of young rats following space flight has revealed deficits in calcium, phosphorus, and osteocalcin, a non-collagenous protein, without an associated decrease in collagen. To characterize the location and nature of this mineralization defect in a weight bearing long bone, the femur, researchers attempted to relate the spatial distribution of mineral in situ in the proximal, central and distal thirds of the femoral diaphysis to the biochemical composition of bone from the same area. Biochemical analyses revealed lower concentrations of calcium, phosphorus and osteocalcin but not collagen only in the central third of the diaphysis of the flight animals (F) compared to synchronous controls (S). Collagen concentration was reduced only in the proximal third of the diaphysis, where all 3 crosslinks, expressed as nM/mol collagen were higher in F than S. A new technique, x ray microtomography, with a resolution of 26 microns, was used to obtain semi-quantitative data on mineral distribution in reconstructed sections of wet whole bone. To improve the resolution of the mineral density distribution, images of the surfaces of cut sections were analyzed by backscattered electrons in a scanning electron microscope (BSE). There was good agreement between the results of the two stereochemical techniques which revealed distinct patterns of mineralization in transverse and longitudinal directions of the diaphysis. The novel methodology developed for this flight experiment shows considerable promise in elucidating the biochemical nature of what appear to be regional alterations in the mineralization of long bones of animals exposed to spaceflight.

Arnaud, S.↗
NASA NTRS1990

Titanium oxide Magneli phases in four chondritic porous interplanetary dust particles

Detailed analytical electron microscope analyses of four fine-grained chondritic porous interplanetary dust particles (IDPs) reveal the presence of titanium oxide Magneli phases, Ti(n)O(2n-1) (n = 4, 5, 6), and rare Ti-metal. The association of Magneli phases, Ti-metal, and carbonaceous material in chondritic IDPs, along with the grain size distributions of Ti-metal and Magneli phases and equilibrium dissociation pressures for these oxygen-deficient Ti-oxides, support in situ solid carbon gasification in these extraterrestrial particles. The active catalyst in this process is titanium metal that may be of interstellar origin. A model is proposed that explains the higher solid carbon content of chondritic IDPs relative to bulk carbon abundances typical for carbonaceous chondrite matrices that represent another type of more metamorphosed undifferentiated solar system bodies.

Rietmeijer, E. J. M.↗
NASA NTRS1991

Collectors Of Airborne And Spaceborne Particles

Brushlike collectors capture samples of dust and other particles in space vacuum or air for optical, scanning-electron-microscope, and/or x-ray analysis. Gently decelerates particles without damaging them, minimizing tendency of some particles to rebound. Depending on design of specific collector of this type, it captures particles ranging upward in size from fractions of micrometer to few micrometers.

Frazer, Robert E.↗
NASA NTRS1990

Development of mercuric iodide uncooled x ray detectors and spectrometers

The results obtained in the development of miniature, lowpower, light weight mercuric iodide, HgI2, x ray spectrometers for future space missions are summarized. It was demonstrated that HgI2 detectors can be employed in a high resolution x ray spectrometer, operating in a scanning electron microscope. Also, the development of HgI2 x ray detectors to augment alpha backscattering spectrometers is discussed. These combination instruments allow for the identification of all chemical elements, with the possible exception of hydrogen, and their respective concentrations. Additionally, further investigations of questions regarding radiation damage effects in the HgI2 x ray detectors are reported.

Iwanczyk, Jan S.↗
NASA NTRS1990

Matrix fatigue crack development in a notched continuous fiber SCS-6/Ti-15-3 composite

In this study the extensive matrix fatigue cracking that has been observed in notched SCS-6/Ti-15-3 composites is investigated. Away from the notch a uniform spacing of the fatigue cracks develops. Closer to the notch, fiber-matrix debonding which occurs increases the crack spacing. Crack spacing and debond length determined from shear-lag cylinder models compare favorably with experimental observations. Scanning electron microscope (SEM) fractography showed that the principal fatigue crack initiation occurred around the zero degree fibers. Interface failure in the 90 degree plies does not lead to the development of the primary fatigue cracking.

Hillberry, B. M.↗
NASA NTRS1991

A non-invasive measure of minerals and electrolytes in tissue

A system for collecting epithelial cells from the oral mucosa for the determination of ion concentration is discussed with application to the study of man's adaptation to microgravity. A number of characteristics of these cells influenced the choice for clinical testing. They are non-cornified epithelial cells located on the inferior aspect of the tongue; therefore, they are well protected from trauma. They have the capability of reflecting relatively recent physiologic changes since they are renewed every three days and have aerobic metabolism. Most importantly, they are easily accessible and can be removed by a wooden applicator stick with minimum discomfort. Smears of cells removed in this manner show predominantly individual cells rather than sheets of contiuous cells. This facilitates the visual isolation of single cells with the electron microscope for analysis. NASA's principle effort in the development of a test to measure the ion concentration in sublingual cells has been research by the biomedical program carried out by scientists with expertise in skeletal metabolism. These efforts were directed toward determining the biological meaning and deviations in interacellular ions in nonhuman primates and in male volunteers for experiments in a model for weightlessness. A brief one page summary of the experiments and results are presented.

Arnaud, Sara B.↗
NASA NTRS1991

SIMS analysis of extended impact features on LDEF experiment

Discussed here are the first Secondary Ion Mass Spectroscopy (SIMS) analysis of projectile material deposited in extended impact features on Ge wafers from the trailing edge. Although most capture cells lost their plastic film covers, they contain extended impact features that apparently were produced by high velocity impacts when the plastic foils were still intact. Detailed optical scanning of all bare capture cells from the trailing edge revealed more than 100 impacts. Fifty-eight were selected by scanning electron microscope (SEM) inspection as prime candidates for SIMS analysis. Preliminary SIMS measurements were made on 15 impacts. More than half showed substantial enhancements of Mg, Al, Si, Ca, and Fe in the impact region, indicating micrometeorites as the projectiles.

Amari, S.↗