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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1970

Readily fiberizable glasses having a high modulus of elasticity

New glass compositions yield composites having higher moduli of elasticity and specific moduli of elasticity than commercially available glasses. Over a reasonable temperature range the glasses have a viscosity of about 20,000 poises. They consist of silica, alumina, magnesia, and beryllia, plus at least one uncommon oxide.

Bacon, J. F.↗
NASA NTRS1979

Improved high modulus carbon fibers

Carbon fibers which are electrically insulating but still maintain the mechanical properties of the original carbon fibers were investigated. Three approaches were taken to increase the electrical resistance of carbon fibers: (1) boron nitride (BN) coatings; (2) doping of carbon fibers to alter their electrical properties; and (3) low temperature final heat treatment. The structure of carbon fibers and its effect upon properties was also studied. Results are presented.

Ansell, G. S.↗
NASA NTRS1980

Universal odd-modulus frequency divider

Simple circuit divides frequency by preselected odd number. Exclusive-OR gate, divide-by-N circuit, and flip-flop are only components. Input pulses must be symmetrical.

Engel, A.↗
NASA NTRS1980

Internal friction and modulus in rocks at depth

Experimental results relevant to the seismic wave attenuation observed for the lunar crust are presented along with some results bearing on the mechanism by which the presence of volatiles increases the attenuation.

Tittmann, B. R.↗
NASA NTRS1980

Progress report 3 of cooperative program for design, fabrication, and testing of high modulus composite helicopter shafting

This report describes the third phase of work, the objective of which was to overcome the excessive brittleness of the previously developed UH-1 helicopter tail rotor drive shaft design which demonstrated a shaft train weight savings of 53.1% over the current 2024-T3 aluminum shaft train. A materials impact program demonstrated exceptionally noteworthy performance of two woven constructions containing E-glass and PRD 49-III (designation later changed to KEVLAR 49) fibers in an epoxy resin matrix. Thermoplastic matrices and PRD 49-III fiber provided impact resistance at low weight which was superior to composites having the same fiber in a thermoset resin matrix. A design, fabrication, and test program showed that shaft impact resistance could be improved over the previously developed graphite composite design at a cost in shaft train rate savings. The shaft train weight savings of the most impact tolerant construction was 4.0% over the current aluminum shaft train. Alternating plies of graphite and glass appear to provide substantially greater tube impact durability than that provided by hybridization of the two fibers into one tape wound to a ply design equivalent in strength and stiffness to that of the alternating ply design. Recommendations were made to continue research work to exploit the potential for more impact-durable structures through the use of KEVLAR 49 fiber, woven structures, thermoplastic matrices and THORNEL 50-S/KEVLAR 49 blends with thermoset matrices.

Wright, C. C.↗
NASA NTRS1982

The use of the PUCOT for elastic modulus measurements on intermetallics at high temperatures

The piezoelectric ultrasonic composite oscillator technique (PUCOT) is being applied to measure the elastic constants of the aluminides in the temperature ranges 300 to 1700 K (CoAl and NiAl) and 300 to 1500 K (FeAl). The PUCOT consists of piezoelectric quartz drive and gauge crystals to excite longitudinal or torsional ultrasonic (80 kHz) resonant stress waves in the specimen and alumina spacer rod of appropriate resonant lengths. The resonant system is driven by a closed loop oscillator which maintains a constant gauge voltage and hence constant strain amplitude in the specimen. While the specimen is heated at 20 K/h the resonant period is measured continuously. The elastic moduli are calculated from these values of the resonant period and accurate determinations of specimen length. The technique is described and some results given.

Wolfenden, A.↗
NASA NTRS1982

Analyses of processing variables in propellant burn rate and modulus. I - Mixing times

The effect of the final mixing time on quality of smokeless AP/HTPB propellant with bimodal AP was examined. Identical ingredients were mixed for various intervals, cast in a circular tube, then fired in a static test. Mechanical properties were measured and initial moduli were calculated from the initial slope of the S-N curves. A theoretical model was developed using the data to quantitatively configure a quality control procedure. A minimum time for mixing fine and coarse AP particles was identified and was approximated to within a factor of two or three using a viscous dispersion time and the surface areas of the particles. The model could be improved by considering settling time and particle size distribution effects.

Ramohalli, K.↗
NASA NTRS1985

Sensory and motor properties of the cerebellar uvula and modulus

The uvula and nodulus (vermal lobules 9 and 10) of the vestibulocerebellum are implicated by behavioral evidence in the control of eye and head movements and in the production of motion sickness. The uvula and nodulus could play a role in these functions through known output pathways. Purkinje cells in both structures project via the fastigial and vestibular nuceli to the ventral horn of the cervical spin cord, to oculomotor neurons, and to the emetic region of the reticular formation (ablation of which abolishes susceptability to motion sickness). Uvula and nodulus Purkinje cells will be analyzed in cats trained to make controlled head movements. The activity of these neurons is expected to modulate well during head and/or eye movements because the uvula and nodulus receive heavy projections from sources of visual, vestibular and neck proprioceptive information. How neuron activity contributes to movement and how different sensory inputs converge to influence this contribution may be determined by characterizing movement related properties of these neurons. A population of neurons that modulates powerfully to the conflict between different head movement signals that can cause motion sickness may be identified.

Robinson, F. R.↗