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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Polyimide adhesive bonding

Adhesive systems which could be used to bond composite-to-composite, composite-to-titanium, and honeycomb sandwich structures with operational capability at 589K for a minimum of 125 hours were evaluated. Evaluations were based on mechanical property tests such as lap shear and flatwise tensile and on processability. Quasi-isotropic Celion 6000/PMR-15 composite adherend was used to construct lap shear and flatwise tensile specimens. Hexcel's HRH-327-3/16-6.0 glass polyimide honeycomb core was also utilized in the flatwise tensile specimens. Numerous processing variations were also studied that led to selected cure cycles for each adhesive. Shear specimens having either 12 mm or 75 mm overlaps were used to determine the effect of bond size on processability and lap shear properties. The data indicate that processing of FM-34, FM-34B-18, LARC-13 and NRO56X can be achieved using a cure compatible with the composite adherend. No significant differences in mechanical properties were observed among the three adhesive systems and all three are suitable candidates for 589K/125 hour service.

Progar, D.↗
NASA NTRS1979

Thermochemical modeling

The prediction of smoke behavior of a material using only the thermochemical properties geometry and flow, was investigated to determine economical methods for producing better materials. Spinoff, and honeycomb sandwich structures are discussed.

Ramohalli, K.↗
NASA NTRS1979

LARC-13 polyimide adhesive bonding

The development of an addition-curing polyimide adhesive suitable for low pressure bonding without the generation of volatiles during cure is reported. LARC-13 is designed for bonding of polyimide matrix composites and of titanium to be used above 500 F, and is based on an oligomeric bis-nadimide which allows its processing at 50 psi or less, making it suitable for the bonding of fragile honeycomb sandwich structures. Few volatiles are evolved during its cure allowing large enclosed structures to be bonded, and it has high room and elevated temperature strengths and good strength retention after short terms up to 1100 F. LARC-13 was successfully used to bond the outer and inner skins of a polyimide/graphite wing shear panel for 500 F use, and for a short-term exposure up to 1100 F. Preparation of the adhesive, bonding, aging, and testing of lap shear and honeycomb samples are discussed.

Saint Clair, T. L.↗
NASA NTRS1980

Design and fabrication of titanium multi-wall Thermal Protection System (TPS) test panels

A titanium multiwall thermal protection system panel was designed. The panel is a nine sheet sandwich structure consisting of an upper and lower face sheet; four dimpled sheets, three septum sheets, and clips for attachment to a vehicle structure. An acceptable fabrication process was developed, and the panel design was verified through mechanical and thermal testing of component specimens. A design was completed which takes into consideration fabrication techniques, thermal properties, mechanical properties, and materials availability.

Blair, W.↗
NASA NTRS1979

High temperature adhesives for bonding composites

Selection and evaluation of candidate adhesives for bonding composites are described. These are based on mechanical property tests (lap shear and flatwise tensile) and processibility. Consideration is given to composite-to-composite, composite-to-titanium, and honeycomb sandwich structures.

Progar, D. J.↗
NASA NTRS1981

Development of advanced lightweight containment systems

Parametric type data were obtained on advanced lightweight containment systems. These data were used to generate design methods and procedures necessary for the successful development of such systems. The methods were then demonstrated through the design of a lightweight containment system for a CF6 size engine. The containment concept evaluated consisted basically of a lightweight structural sandwich shell wrapped with dry Kevlar cloth. The initial testing was directed towards the determination of the amount of Kevlar required to result in threshold containment for a specific set of test conditions. A relationship was then developed between the thickness required and the energy of the released blade so that the data could be used to design for conditions other than those tested.

Stotler, C.↗
NASA NTRS1981

A novel addition polyimide adhesive

An addition polyimide adhesive, LARC 13, was developed which shows promise for bonding both titanium and composites for applications which require service temperatures in excess of 533 K. The LARC 13 is based on an oligomeric bis nadimide containing a meta linked aromatic diamine. The adhesive melts prior to polymerization due to its oligomeric nature, thereby allowing it to be processed at 344 kPa or less. Therefore, LARC 13 is ideal for the bonding of honeycomb sandwich structures. After melting, the resin thermosets during the cure of the nadic endcaps to a highly crosslinked system. Few volatiles are evolved, thus allowing large enclosed structures to be bonded. Preparation of the adhesive as well as bonding, aging, and testing of lap shear and honeycomb samples are discussed.

St.clair, T. L.↗
NASA NTRS1984

Thermal performance of FRSI/graphite epoxy materials for the Orbiter TPS application

Radiant tests have been conducted to evaluate the performance of the Flexible Reusable Surface Insulation (FRSI) when bonded to Graphite/Epoxy (G/E) honeycomb sandwich structures. The results from this study indicate reasonable agreement with the baseline FRSI properties that existed prior to this test program. An updated Thermal Math Model (TMM) prediction technique was developed, with the use of the well-defined boundary conditions, which appears to be valid in analyzing the complex heat transfer associated with the honeycomb structure. The updated TM analysis of flight data resulted in good agreement of predicted temperatures with flight data for bondline responses of Orbiter FRSI/GE TPS applications.

Norman, I.↗
NASA NTRS1984

Steps toward eight-meter honeycomb mirror blanks. I Rationale and approach

The best form for 8-m telescope mirrors is discussed. It is concluded that honeycomb sandwich structure can meet the most exacting demand goals for subarcsecond image quality in optical and infrared astronomy. These structures are light, have good stiffness against gravitational and wind loading, and have low thermal inertia. The latter permits them to be operated at the ambient air temperature to avoid local seeing problems. Borosilicate and aluminosilicate glasses are adequate materials for ventilated honeycombs, which do not require low expansion materials.

Angel, J. R. P.↗
NASA NTRS1988

Processes for fabricating and load testing NASA scatterometer antenna assemblies

The purpose of this paper is to present the processes used to fabricate and load test the NASA Scatterometer Antenna Assemblies. The fabrication processes include layup, curing and machining of antenna components, and the bonding and assembly of the components into the final antenna configuration. The design of each antenna consists of an aluminum waveguide bonded to a sandwich structure of Nomex honeycomb core with graphite/epoxy skins. A titanium end fitting with fiberglass/epoxy transitions is bonded into one end of each antenna. Several antenna components are fabricated using a process where aluminum foil is co-cured to a composite surface. The antenna assemblies are radiographically inspected, thermally cycled, and load tested prior to shipment.

Barth, James R.↗
NASA NTRS1989

Microsandwich honeycomb

Microsandwich honeycombs are honeycombs in which the cell walls are themselves sandwich structures. This article develops the idea of microsandwich honeycombs, outlining their design principles, fabrication techniques and properties.

Bhat, T. Balakrishna↗
NASA NTRS1990

Crash-Resistant Shield

Impact-resistant shield designed to consist of aluminum honeycomb structure sandwiched between inner and outer aluminum skins. Intended to protect radioisotope thermoelectric generator of spacecraft from impact with ground or water after free fall from upper atmosphere. Designed to absorb impact energy by buckling, while inner and outer skins designed to protect against shrapnel, overpressure, and impact loads. Concept of shield applicable to crashproof compartments for ground vehicles and aircraft.

Bixler, Charles H.↗
NASA NTRS1990

Probe Measures Fouling As In Heat Exchangers

Combustion deposits reduce transfer of heat. Instrument measures fouling like that on gas side of heat exchanger in direct-fired boiler or heat-recovery system. Heat-flux probe includes tube with embedded meter in outer shell. Combustion gases flow over probe, and fouling accumulates on it, just as fouling would on heat exchanger. Embedded heat-flow meter is sandwich structure in which thin Chromel layers and middle alloy form thermopile. Users determine when fouling approaches unacceptable levels so they schedule cleaning and avoid decreased transfer of heat and increased drop in pressure fouling causes. Avoids cost of premature, unnecessary maintenance.

Marner, Wilbur J.↗
NASA NTRS1989

Extremely lightweight space telescope mirrors with integrated active figure control

A concept for an extremely lightweight primary mirror for a large space telescope is proposed. The mirror uses a sandwich structure composed of aluminum faceplates with an aluminum foam core. Modal analysis indicates that a fundamental frequency of 100 Hz can be obtained for a 6 meter diameter mirror with a tapered back and having a total mass of about 3500 kg. An array of thermal actuators embedded in the mirror corrects for figure errors. Such an active thermal figure control system does not have a quick response, but is well suited to space applications where disturbances have relatively long time constants. The advantage of thermal actuators is very high reliability, a primary concern in any space system requiring a large number of actuators.

Bely, Pierre Y.↗
NASA NTRS1991

Making Three-Layer Solid Electrolyte/Electrode Sandwiches

Tape-casting-and-sintering process joins two ceramic materials having widely different sintering temperatures into integral sandwich structure. Layers retain their identities, without migration of constituents. Used to make three-layer structure composed of outer porous layers of strontium-doped lanthanum manganite and inner dense layer of yttria-stabilized zirconia. Structures used to make electrolytic and fuels cells with solid electrolytes for use at high temperatures. Other potential applications include oxygen pumps and oxygen sensors.

Schroeder, James E.↗
NASA NTRS1989

Microsandwich cellular solids

This article introduces a new concept of microsandwiching in which the cell wall itself is a sandwich structure and is substantially stiffer. Some experimental results are presented to show the efficacy of this approach. A method for optimizing the design of honeycomb microsandwich is also briefly outlined.

Balakrishna Bhat, T.↗
NASA NTRS1993

Research in textile composites at KU, Leuven

An overview is presented of the research on textile composites at Katholieke Universiteit Leuven. Three dimensionally woven sandwich fabric preforms are investigated for delamination resistant sandwich structures, velvet woven 2.5 dimensional fabrics for delamination resistant laminates, and knitted fabrics with good drapability for laminates of complex shape.

Verpoest, Ignaas↗
NASA NTRS1992

Pressurized Lunar Rover (PLR)

The objective of this project was to design a manned pressurized lunar rover (PLR) for long-range transportation and for exploration of the lunar surface. The vehicle must be capable of operating on a 14-day mission, traveling within a radius of 500 km during a lunar day or within a 50-km radius during a lunar night. The vehicle must accommodate a nominal crew of four, support two 28-hour EVA's, and in case of emergency, support a crew of six when near the lunar base. A nominal speed of ten km/hr and capability of towing a trailer with a mass of two mt are required. Two preliminary designs have been developed by two independent student teams. The PLR 1 design proposes a seven meter long cylindrical main vehicle and a trailer which houses the power and heat rejection systems. The main vehicle carries the astronauts, life support systems, navigation and communication systems, lighting, robotic arms, tools, and equipment for exploratory experiments. The rover uses a simple mobility system with six wheels on the main vehicle and two on the trailer. The nonpressurized trailer contains a modular radioisotope thermoelectric generator (RTG) supplying 6.5 kW continuous power. A secondary energy storage for short-term peak power needs is provided by a bank of lithium-sulfur dioxide batteries. The life support system is partly a regenerative system with air and hygiene water being recycled. A layer of water inside the composite shell surrounds the command center allowing the center to be used as a safe haven during solar flares. The PLR 1 has a total mass of 6197 kg. It has a top speed of 18 km/hr and is capable of towing three metric tons, in addition to the RTG trailer. The PLR 2 configuration consists of two four-meter diameter, cylindrical hulls which are passively connected by a flexible passageway, resulting in the overall vehicle length of 11 m. The vehicle is driven by eight independently suspended wheels. The dual-cylinder concept allows articulated as well as double Ackermann steering. The primary power of 8 kW is supplied by a dynamic isotope system using a closed Brayton cycle with a xenon-hydrogen mixture as the working fluid. A sodium-sulfur battery serves as the secondary power source. Excess heat produced by the primary power system and other rover systems is rejected by radiators located on the top of the rear cylinder. The total mass of the PLR 2 is 7015 kg. Simplicity and low total weight have been the driving principles behind the design of PLR 1. The overall configuration consists of a 7-m-long, 3-m-diameter cylindrical main vehicle and a two-wheeled trailer. The cylinder of the main body is capped by eight-section, faceted, semi-hemispherical ends. The trailer contains the RTG power source and is not pressurized. The shell of the main body is constructed of a layered carbon fiber/foam/Kevlar sandwich structure. Included in the shell is a layer of water for radiation protection. The layer of water extends from the front of the rover over the crew compartment and creates a safe haven for the crew during a solar flare-up. The carbon fiber provides the majority of the strength and stiffness and the Kevlar provides protection from micrometeoroids. The Kevlar is covered with a gold foil and multi-layer insulation (MLI) to reduce radiation degradation and heat transfer through the wall. A thin thermoplastic layer seals the fiber and provides additional strength.

Creel, Kenneth↗