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At least 307 records · Page 17

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NASA NTRS1982

Nonmetallic materials handbook. Volume 2: Epoxy and silicone materials

Chemical and physical property test data obtained during qualification and receiving inspection testing of nonmetallic materials for the Viking Mars Lander program is presented. Thermochemical data showing degradation as a function of temperature from room temperature through 773 K is included. These data include activation energies for thermal degradation, rate constants, and exo- and/or endotherms. Thermal degradations carried out under vacuum include mass spectral data taken simultaneously during the decomposition. Many materials have supporting data such as condensation rates of degassed products and isothermal weight loss. Changes in mechanical, electrical, and thermal properties after exposure to 408 K in nitrogen for times ranging from 380 to 570 hours are included for many materials.

Podlaseck, S. E.↗

NASA NTRS1981

Assessment of burning characteristics of aircraft interior materials

The performance of a series of seat cushion design constructions was compared based on their heat and smoke release characteristics. Tests were conducted in a room size calorimeter instrumented for measuring weight loss, rate of heat release, smoke and volatile decomposition products and the cumulative energy release. Baseline data were obtained from burn tests conducted on commercial airline salvage sets as a comparison with more advanced seat designs. A toxicological assessment of smoke and fire gases involved the exposure of test animals and their biological responses ascertained. Relative toxicological hazards of the combustion gases are discussed based on the animal response studies and the analysis of the combustion gases.

Grand, A. F.↗

NASA NTRS1981

Sub-T/g/ annealing studies of advanced epoxy-matrix graphite-fiber-reinforced composites

Annealing at temperatures below the glass transition temperature (sub-T/g/ annealing) in structural epoxy network glasses is found to affect long-term mechanical properties of symmetrically (+ or - 45 deg) reinforced 16-lamina graphite/epoxy composites. Post-cured specimens of Thornel 300 graphite/Narmco 5208 epoxy are sub-T(g) annealed at 140 C for about 10, 100, 1000, 10,000, and 100,000 min with a prior quenching above T(g). The ultimate tensile strength, strain-to-break, and static toughness of the composite materials are found to decrease as a function of sub-T(g) annealing time, while no weight loss is observed. Time-dependent changes in properties are explained by a physical aging concept based on free-volume decreases in the nonequilibrium glassy state of network epoxies, and results imply that changes in composite properties may occur with the service time.

Kong, E. S. W.↗

NASA NTRS1981

Effects of ultra-clean and centrifugal filtration on rolling-element bearing life

Fatigue tests were conducted on groups of 65-mm bore diameter deep-groove ball bearings in a MIL-L-23699 lubricant under two levels of filtration to determine the upper limit in bearing life under the strictest possible lubricant cleanliness conditions. Bearing fatigue lives, surface distress and weight loss were compared to previous bearing fatigue tests in contaminated and noncontaminated oil filters having absolute removal ratings of 3, 30, 49, and 105 microns, with lubricant and sump temperatures maintained at 347 K. Ultra clean lubrication was found to produce bearing fatigue lives that were approximately twice that obtained in previous tests with contaminated oil using 3 micron absolute filtration. It was also observed that the centrifugal oil filter has the same effectiveness as a 30 micron absolute filter in preventing surface damage.

Loewenthal, S. H.↗

NASA NTRS1981

Benzoic acid degradation of polyacrylonitrile fibers

The reactions of polyacrylonitrile (PAN) fibers in the presence of benzoic acid have been studied. Polyacrylonitrile fibers oxidize more readily in the presence of benzoic acid than in air at temperatures in the range of 170 C. The product decreased in solubility with extent of reaction. Gel permeation chromatography of the soluble fraction showed change in polydispersity. The insoluble product exhibited differences in weight loss as a function of decomposition temperature compared to PAN fibers. Infrared analyses of the fiber product showed absorption peaks similar to air-oxidized PAN. High-energy photoelectron spectral analysis showed a carbon-rich surface which contained oxygen and nitrogen. An air oxidized sample of fiber contained more oxygen at the surface than a fiber treated first with benzoic acid and then air oxidized.

Varma, D. S.↗

NASA NTRS1981

Benzoic acid degradation of polyacrylonitrile fibers

Varma, D. S.↗

NASA NTRS1982

Lower-curing-temperature PMR polyimides

Partial substitution of a p-aminostyrene end-cap for the monomethyl ester of 5-norbornene-2, 3-dicarboxylic acid lowered the final cure temperature of typical PMR resins from 600 F to 500 F. The weight loss characteristics of neat resins and graphite fiber composites prepared by using the mixed end-cap approach were determined at 600 F. The room temperature and short-time elevated temperature mechanical properties of the composites at 550 F and 600 F were determined. The mechanical property retention characteristics of the composites at 550 F and 600 F are discussed.

Delvigs, P.↗

NASA NTRS1982

The optimization of aircraft seat cushion fire-blocking layers. Full Scale: Test description and results

Full-scale burn tests were conducted on thirteen different seat cushion configurations in a cabin fire simulator. The fire source used was a quartz lamp radiant energy panel with a propane pilot flame. During each test, data were recorded for cushion temperatures, radiant heat flux, rate of weight loss of test specimens, and cabin temperatures. When compared to existing passenger aircraft seat cushions, the test specimens incorporating a fire barrier and those fabricated from advance materials, using improved construction methods, exhibited significantly greater fire resistance.

Schutter, K. J.↗

NASA NTRS1983

Cavitation pitting and erosion of Al 6061-T6 in mineral oil and water

The authors are currently carrying out a study of the cavitation erosion of different bearing metals and alloys in mineral oils were studied. The variations of weight loss, the pit diameter and depth due to cavitation erosion on Al 6061-T6 in mineral oil and water are presented.

Rao, B. C. S.↗

NASA NTRS1983

Solid particle impingement erosion characteristics of cylindrical surfaces, pre-existing holes and slits

The erosion characteristics of aluminum cylinders sand-blasted with both spherical and angular erodent particles were studied and compared with results from previously studied flat surfaces. The cylindrical results are discussed with respect to impact conditions. The relationship between erosion rate and pit morphology (width, depth, and width to depth ratio) is established. The aspects of (1) erosion rate versus time curves on cylindrical surfaces; (2) long-term exposures; and (3) erosion rate versus time curves with spherical and angular particles are presented. The erosion morphology and characteristics of aluminum surfaces with pre-existing circular cylindrical and conical holes of different sizes were examined using weight loss measurements, scanning electron microscopy, a profilometer, and a depth gage. The morphological features (radial and concentric rings) are discussed with reference to flat surfaces, and the erosion features with spherical microglass beads. The similarities and differences of erosion and morphological features are highlighted. The erosion versus time curves of various shapes of holes are discussed and are compared with those of a flat surface. The erosion process at slits is considered.

Rao, P. V.↗

NASA NTRS1983

Lower-curing-temperature PMR polyimides

Delvigs, P.↗

NASA NTRS1983

Space Station and the life sciences

Previous fundamental research in space life sciences is examined, and consideration is devoted to studies relevant to Space Station activities. Microgravity causes weight loss, hemoconcentration, and orthostatic intolerance when astronauts returns to earth. Losses in bone density, bone calcium, and muscle nitrogen have also been observed, together with cardiovascular deconditioning, fluid-electrolyte metabolism alteration, and space sickness. Experiments have been performed with plants, bacteria, fungi, protozoa, tissue cultures, invertebrate species, and with nonhuman vertebrates, showing little effect on simple cell functions. The Spacelab first flight will feature seven life science experiments and the second flight, two. Further studies will be performed on later flights. Continued life science studies to optimize human performance in space are necessary for the efficient operation of a Space Station and the assembly of large space structures, particularly in interaction with automated machinery.

White, R. J.↗

NASA NTRS1983

Galvanic coupling between D6AC steel, 6061-T6 aluminum, Inconel 718 and graphite-epoxy composite material: Corrosion occurrence and prevention

The effects of galvanic coupling between D6AC steel, 6061-T6 aluminum, Inconel 718, and graphite-epoxy composite material (G/E) in 3.5% NaCl were studied. Measurements of corrosion potentials, galvanic currents and corrosion rates of the bare metals using weight-loss methods served to establish the need for corrosion protection in cases where D6AC steel and 6061-T6 aluminum are galvanically coupled to G/E in salt water while Inconel 718 was shown to be compatible with G/E. Six tests were made to study corrosion protective methods for eliminating galvanic corrosion in the cases of D6AC steel and 6061-T6 aluminum coupled to G/E. These results indicate that, when the G/E is completely coated with paint or a paint/polyurethane resin combination, satisfactory protection of the D6AC steel is achieved with either a coat of zinc-rich primer or a primer/topcoat combination. Likewise, satisfactory corrosion protection of the aluminum is achieved by coating it with an epoxy coating system.

Danford, M. D.↗

NASA NTRS1983

OSHA medical and workplace surveillance requirements and NIOSH recommendations (for employees exposed to toxic substances and other work hazards)

Both OSHA medical and work place surveillance requirements and NIOSH recommendations were prepared as a desk reference to help occupational health professionals to perform their duties. The medical surveillance information focuses on frequency of physical examinations, specific problems that may arise as a result of exposure (e.g., decreased immunocompetence, weight loss, ets.), conditions that intensify the harmful effects of exposure (e.g., medication an exposed employee may be taking, cigarette smoking, etc.), the areas that should be scrutinized in medical and work histories and during the physical exam, and specific clinical tests that should be conducted. Recordkeeping requirements are also specified. The workplace surveillance information consists of monitoring requirements, personal protective equipment requirements, and recordkeeping requirements. Such details as the sampling devices that should be used, the type of respirators that should be worn, and the frequency of inspections are included. This document does not specify the training, labeling and posting, and safe work practice requirements and recommendations due to space considerations.

Cooper, L. P.↗

NASA NTRS1984

Processing study of a polyimidesulfone adhesive

An adhesive bonding process cycle study was performed for a polyimidesulfone (PISO2) recently developed as a promising structural adhesive. The high molecular weight, linear aromatic system possesses properties which make it attractive as a processable, low-cost material for elevated temperature applications. The results of a study to better understand the parameters that affect the adhesive properties of the polymer for titanium alloy adherends are detailed. These include the tape preparation, the use of a primer, and press and simulated autoclave processing conditions. The polymer was characterized using Fourier Transform Infrared Spectroscopy, glass transition temperature determination, flow measurements, and weight loss measurements. The adhesive's strength determined by lap shear strength tests was used to evaluate the effects of the bonding process variations. Higher lap shear strengths were obtained at room temperature when a primer (PISO2) was used; however, the results were the same at 232 C (450 F) with or without a primer. The use of a vacuum (simulated autoclave cycle) during titanium bonding produced similar lap shear strengths to those specimens bonded without a vacuum.

Progar, D. J.↗

NASA NTRS1984

Ion-beam-textured and coated surfaces experiment (S1003)

The objective of this LDEF experiment is to measure the effects of exposure to the shuttle launch and near Earth space environments on the optical properties of ion beam textured high absorptance solar thermal control surfaces, the optical and electrical properties of ion beam sputtered conductive solar thermal control surfaces, and the weight loss of ion beam deposited oxide polymer films. The various types of surfaces to be tested include six major categories: (1) ion beam textured surfaces suitable for space solar thermal (solar concentration) application; (2) painted and/or state of the art solar thermal surfaces; (3) ion beam sputtered conductive coatings for thermal and space charge control (e.g., indium-oxide coated metalized FEP Teflon); (4) ion beam sputtered conductive coated solar sail materials for space charge control and cooling through emittance; (5) micrometeoroid sensitive samples whose optical properties change only as a result of micrometeoroid impact; and (6) Kapton coated with oxide polymer films to minimize oxygen degradation at near Earth orbit altitudes.

Mirtich, M. J., Jr.↗

NASA NTRS1983

Physical aging and its influence on the reliability of network epoxies and epoxy-matrix composites

The matrix-dominated physical and mechanical properties of a carbon fiber reinforced epoxy composite and a neat epoxy resin were found to be affected by sub-Tg annealing in nitrogen and dark atmosphere. Postcured specimens of Thornel 300 carbon-fiber/Fiberite 934 epoxy as well as Fiberite 934 epoxy resin were quenched from above Tg and given annealing at 140 C, 110 C, or 80 C, for time up to one-hundred thousand minutes. No weight loss was observed during annealing at these temperatures. Significant variations were found in density, modulus, hardness, damping, moisture absorption ability, thermal expansivity. Moisture-epoxy interactious were also studied. The kinetics of aging as well as the molecular aggregation during this densification process were monitored by differential scanning calorimetry, dynamic mechanical analysis, density gradient column, microhardness tester, Instron, and solid-state nuclear magnetic resonance spectroscopy.

Heinemann, K.↗

NASA NTRS1983

Erosion of mylar and protection by thin metal films

Mylar strips, 2.5 microns thick, uncoated and coated with 50A, 100A and 200A of Al, Pd, and Au/Pd were exposed on STS-5 in order to measure the erosion of mylar and to test means of protecting thin plastic foils commonly used for space experiments in low earth orbit. Analysis by optical microscopy, SEM and STEM investigation, EDX measurements, FTIR spectroscopy and weight loss measurements showed that while up to 75 percent of the uncoated mylar was eroded during exposure, thin coatings of the above metals can protect mylar for integrated oxygen-fluxes of at least 10 to the 21st atoms/sq cm.

Fraundorf, P.↗