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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

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NASA NTRS1972

Status of reusable surface insulation thermal protection system technology programs

The development of three low-density rigidized insulation materials for the shuttle TPS application is reported. These materials consist of one high purity silica system and two systems based on mullite, an aluminum silicate. Both systems consist of fibers joined together with appropriate binders to obtain a rigidized insulation composite. Both material systems require the application of a glassy coating to provide a wear resistant, high emittance surface and to prevent the absorption of water by the fiber matrix. The technology program has addressed the development of water impervious coatings, methods of assembling the materials in design concepts while minimizing the thermal stress in the insulation, achieving compatibility between the RSI material and the structural system, and test evaluations to demonstrate the feasibility of the surface insulation concept.

Greenshields, D. H.↗

NASA NTRS1971

Copper/nickel eutectic brazing of titanium

Technique joins titanium or one of its alloys to materials, such as iron, nickel or cobalt base material, or to refractory metals. To ensure formation of a satisfactory bond, the temperature, time, environment and pressure must be controlled.

Kutchera, R. E.↗

NASA NTRS1972

Materials data handbook: Aluminum alloy 6061

A summary of the materials property information for aluminum alloy 6061 is presented. The scope of the information includes physical and mechanical properties of the alloy at cryogenic, ambient, and elevated temperatures. Information on material procurement, metallurgy, corrosion, environmental effects, fabrication, and joining techniques is developed.

Muraca, R. F.↗

NASA NTRS1972

Materials data handbook: Aluminum alloy 7075

A summary of the materials property information on aluminum alloy 7075 is presented. The scope of the information includes physical and mechanical properties of the alloy at cryogenic, ambient, and elevated temperatures. Information on material procurement, metallurgy, corrosion, environmental effects, fabrication, and joining techniques is developed.

Muraca, R. F.↗

NASA NTRS1972

Welding and brazing of nickel and nickel-base alloys

The joining of four types of nickel-base materials is described: (1) high-nickel, nonheat-treatable alloys, (2) solid-solution-hardening nickel-base alloys, (3) precipitation-hardening nickel-base alloys, and (4) dispersion-hardening nickel-base alloys. The high-nickel and solid-solution-hardening alloys are widely used in chemical containers and piping. These materials have excellent resistance to corrosion and oxidation, and retain useful strength at elevated temperatures. The precipitation-hardening alloys have good properties at elevated temperature. They are important in many aerospace applications. Dispersion-hardening nickel also is used for elevated-temperature service.

Mortland, J. E.↗

NASA NTRS1976

Interconnnect and bonding technologies for large flexible solar arrays

Thermocompression bonding and conductive adhesive bonding are developed and evaluated as alternate methods of joining solar cells to their interconnect assemblies. Bonding materials and process controls applicable to fabrication of large, flexible substrate solar cell arrays are studied. The primary potential use of the techniques developed is on the solar array developed by NASA/MSFC and LMSC for solar electric propulsion (SEP) and shuttle payload applications. This array is made up of flexible panels approximately 0.7 by 3.4 meters. It is required to operate in space between 0.3 and 6 AU for 5 years with limited degradation. Materials selected must be capable of enduring this space environment, including outgassing and radiation.

Source record↗

NASA NTRS1999

Cryotank Skin/Stringer Bondline Analysis

The need for light weight structure for advanced launch systems have presented great challenges and led to the usage of composites materials in a variety of structural assemblies where joining of two or more components is imperative. Although joints can be mechanically bolted, adhesive bonding has always been a very desirable method for joining the composite components, particularly for the cryotank systems, to achieve maximum structural efficiency. This paper presents the analytical approach resulted from the conceptual development of the DC-Y composite cryotank, conducted under the NASA/Boeing NRA 8-12 Partnership, to support the continued progress of SSTO (Single-Stage-To-Orbit) concepts. One of the critical areas of design was identified as the bonded interface between the skin (tank wall) and stringer. The approach to analyze this critical area will be illustrated through the steps which were used to evaluate the structural integrity of the bondline. Detailed finite element models were developed and numerous coupon test data were also gathered as part of the approach. Future plan is to incorporate this approach as a building block in analyzing bondline for the cryotank systems of RLVs (Reusable Launch Vehicles).

Nguyen, Bao↗

NASA NTRS1993

Semiconductor cooling apparatus

Gas derived graphite fibers generated by the decomposition of an organic gas are joined with a suitable binder. This produces a high thermal conductivity composite material which passively conducts heat from a source, such as a semiconductor, to a heat sink. The fibers may be intercalated. The intercalate can be halogen or halide salt, alkaline metal, or any other species which contributes to the electrical conductivity improvement of the graphite fiber. The fibers are bundled and joined with a suitable binder to form a high thermal conductivity composite material device. The heat transfer device may also be made of intercalated highly oriented pyrolytic graphite and machined, rather than made of fibers.

Banks, Bruce A.↗

NASA NTRS1996

Investigation of Machine Design for Friction Stir Welding

The process of joining two pieces of metal together has not significantly changed over the last few decades. The basic idea used is to bring the pieces together and apply enough heat to melt the metal at the interface. The molten metal mixes and after cooling forms a strong joint. This process is called the fusion process. The most significant difference between the many fusion processes is how the heat is generated and applied. The Welding Institute (TWI), in Great Britain, has recently patented an innovative application of mechanical friction. TWI designed a tool and process called Friction Stir Welding (FSW) that uses friction to heat the metal to within a few hundred degrees Fahrenheit of melting, just to the point of being plastic-like. The tool then stirs the plasticized metal together forming a joint that has been shown to be as good or better than an equivalent fusion joint. The FSW process is well suited for the joining of the aluminum alloys used in the aerospace industry. The relatively low melting point of aluminum eliminates the requirements for exotic materials for pin tool design. The FSW process has been successfully used to join alloys such as 7075 which were before considered "unweldable", and aluminum-lithium 2195 which exhibits many problems when fusion welded. The objective this summer was to investigate the design of a FSW system that could take this process from the laboratory to the manufacturing floor. In particular, it was the goal of my NASA colleague to develop a concept for applying the FSW process to the manufacturing of aluminum cryogenic oxygen and hydrogen tanks, of the sort used to make the Shuttle External Tank.

Romine, Peter L.↗

NASA NTRSDate not supplied

Prometheus and Constellation Materials Research and Testing Overview

Outline - New Technologies and New Materials meet Flight Program - Reactor Materials Selection - Material Radiation Resistance - Testing in four different radiation environments - Superalloy Creep Testing - Superalloy-Refractory Alloy Joining - Superalloy, Stainless Steel, Copper Brazing - Superalloy-Refractory Cross Contamination - Na and NaK Compatibility - Radiator Panel Materials Selection

nuclear power↗

NASA NTRS1998

Microstructure and Mechanical Properties of Reaction-Formed Joints in Reaction Bonded Silicon Carbide Ceramics

A reaction-bonded silicon carbide (RB-SiC) ceramic material (Carborundum's Cerastar RB-SIC) has been joined using a reaction forming approach. Microstructure and mechanical properties of three types of reaction-formed joints (350 micron, 50-55 micron, and 20-25 micron thick) have been evaluated. Thick (approximately 350 micron) joints consist mainly of silicon with a small amount of silicon carbide. The flexural strength of thick joints is about 44 plus or minus 2 MPa, and fracture always occurs at the joints. The microscopic examination of fracture surfaces of specimens with thick joints tested at room temperature revealed the failure mode to be typically brittle. Thin joints (<50-55 micron) consist of silicon carbide and silicon phases. The room and high temperature flexural strengths of thin (<50-55 micron) reaction-formed joints have been found to be at least equal to that of the bulk Cerastar RB-SIC materials because the flexure bars fracture away from the joint regions. In this case, the fracture origins appear to be inhomogeneities inside the parent material. This was always found to be the case for thin joints tested at temperatures up to 1350C in air. This observation suggests that the strength of Cerastar RB-SIC material containing a thin joint is not limited by the joint strength but by the strength of the bulk (parent) materials.

Singh, M.↗

NASA NTRS1982

One-step dual purpose joining technique

This fastener used in induction heating is a wire screen basically of an eddy current carrying material such as carbon steel. Selected wires in the screen are copper, sheathed in an insulating material. The screen is placed between two sheets of thermoplastics. When inductively heated, the composite softens and flows around the apertures of the screen. After this heating and joining, the copper wires may be used to conduct electricity.

Buckley, J. D.↗

NASA NTRS1997

Joining of Silicon Carbide-Based Ceramics by Reaction Forming Method

Recently, there has been a surge of interest in the development and testing of silicon-based ceramics and composite components for a number of aerospace and ground based systems. The designs often require fabrication of complex shaped parts which can be quite expensive. One attractive way of achieving this goal is to build up complex shapes by joining together geometrically simple shapes. However, the joints should have good mechanical strength and environmental stability comparable to the bulk materials. These joints should also be able to maintain their structural integrity at high temperatures. In addition, the joining technique should be practical, reliable, and affordable. Thus, joining has been recognized as one of the enabling technologies for the successful utilization of silicon carbide based ceramic components in high temperature applications. Overviews of various joining techniques, i.e., mechanical fastening, adhesive bonding, welding, brazing, and soldering have been provided in recent publications. The majority of the techniques used today are based on the joining of monolithic ceramics with metals either by diffusion bonding, metal brazing, brazing with oxides and oxynitrides, or diffusion welding. These techniques need either very high temperatures for processing or hot pressing (high pressures). The joints produced by these techniques have different thermal expansion coefficients than the ceramic materials, which creates a stress concentration in the joint area. The use temperatures for these joints are around 700 C. Ceramic joint interlayers have been developed as a means of obtaining high temperature joints. These joint interlayers have been produced via pre-ceramic polymers, in-situ displacement reactions, and reaction bonding techniques. Joints produced by the pre-ceramic polymer approach exhibit a large amounts of porosity and poor mechanical properties. On the other hand, hot pressing or high pressures are needed for in-situ displacement reactions and reaction bonding techniques. Due to the equipment required, these techniques are impractical for joining large or complex shaped components.

Singh, M.↗

NASA NTRS1976

Absorption dips at low X-ray energies in Cygnus X-1

Absorbing material in Cygnus X-1 jitters near the line joining the two stars, out of the orbital plane is described. Three looks with the Copernicus satellite at Cygnus X-1 have produced four examples of absorption dips (decreases in the 2 to 7 keV flux from Cygnus X-1 with an increase of spectral hardness consistent with photoelectric absorption).

Murdin, P. G.↗

NASA NTRS1993

Space Storable Rocket Technology program (SSRT). Option 1 program

The Space Storable Rocket Technology (SSRT) Option 1 Program was initiated in October 1991 after completion of the Basic Program. The program was restructured in mid-July 1992 to incorporate a Rhenium Technology Task and reduce the scope of the LO2-N2H4 engine development. The program was also extended to late February 1993 to allow for the Rhenium Technology Task completion. The Option 1 Program was devoted to evaluation of two new injector elements, evaluation of two different methods of thermal protection of the injector, evaluation of high temperature material properties of rhenium and evaluation of methods of joining the rhenium thrust chamber to the columbium injector and nozzle extension. In addition, critical experiments were conducted (Funded by Option 2) to evaluate mechanisms to understand the effects of GO2 injection into the chamber, helium injection into the main LO2, effect of the splash plate and effect of decreasing the aspect ratio of the 120-slot (-13a) element. The performance and thermal models were used to further correlate the test results with analyses. The results of the work accomplished are summarized.

Chazen, Melvin L.↗

NASA NTRS1973

A new concept for joining dissimilar composites

Bi-composite joint serves as interface between two dissimilar materials by interleaving plies of one composite with plies of another. This interleaving forms transition area between composites. Voids are filled in with epoxy resin to form strong, smooth transition between two materials.

Dullea, K. C.↗

NASA NTRS2006

Experimental Observations for Determining the Maximum Torque Values to Apply to Composite Components Mechanically Joined With Fasteners (MSFC Center Director's Discretionary Fund Final Report, Proj. 03-13}

Aerospace structures utilize innovative, lightweight composite materials for exploration activities. These structural components, due to various reasons including size limitations, manufacturing facilities, contractual obligations, or particular design requirements, will have to be joined. The common methodologies for joining composite components are the adhesively bonded and mechanically fastened joints and, in certain instances, both methods are simultaneously incorporated into the design. Guidelines and recommendations exist for engineers to develop design criteria and analyze and test composites. However, there are no guidelines or recommendations based on analysis or test data to specify a torque or torque range to apply to metallic mechanical fasteners used to join composite components. Utilizing the torque tension machine at NASA s Marshall Space Flight Center, an initial series of tests were conducted to determine the maximum torque that could be applied to a composite specimen. Acoustic emissions were used to nondestructively assess the specimens during the tests and thermographic imaging after the tests.

Thomas, F. P.↗

DOE OSTI2026

Towards High-Speed friction stir welding of 25 mm Thick AA2139-T8: tool innovation and process development

Joining thick plates (≥ 12 mm) of aluminum (Al) alloys is challenging due to high tool forces, uneven material flow, and non-uniform heat distribution through the material’s thickness. Recent advancements in tool design and welding parameters for friction stir welding (FSW) in thick plates butt joining have encountered a developmental plateau, highlighting the need for innovative approaches to overcome existing limitations. Here, this study focuses on the systematic development of single-pass and double-pass FSW processes for high-strength aluminum alloy AA2139-T8, to improve joint efficiency and enable high-speed welding capabilities. Experimental evidence is presented for a novel tool design with opposing pin threads, enabling high-speed (178 mm/min) single-pass friction stir butt welding of 25 mm thick AA2139-T8. A series of FSW trials was conducted both in air and with a trailing water spray, using steel backing plates (BPs) to investigate the impact of quenching and cooling rates on process response and joint performance. A joint efficiency of 83% was attained using the novel tool features and effectively controlling process forces and thermal boundary conditions.

AA2139-T8↗