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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Combustion Joining of Regolith Tiles for In-Situ Fabrication of Launch/Landing Pads on the Moon and Mars

To mitigate dust problems during launch/landing operations in lunar and Mars missions, it is desired to build solid pads on the surface. Recently, strong tiles have been fabricated from lunar regolith simulants using high-temperature sintering. The present work investigates combustion joining of these tiles through the use of exothermic intermetallic reactions. Specifically, nickel/aluminum (1:1 mole ratio) mixture was placed in a gap between the tiles sintered from JSC-1A lunar regolith simulant. Upon ignition by a laser, a self-sustained propagation of the combustion front over the mixture occurred. Joining was improved with increasing the tile thickness from 6.3 mm to 12.7 mm. The temperatures sufficient for melting the glass phase of JSC-1A were recorded for 12.7-mm tiles, which explains the observed better joining.

Ferguson, Robert E.↗
NASA NTRSDate not supplied

Joining, Disassembly, and Reconfiguration of Thermoplastic Composites for Space Applications

Thermoplastic composites are increasingly being investigated for aerospace applications because of their relatively short processing time, good chemical and radiation resistance, and potential for reforming and reuse via melting. The manufacturing, reforming, and reuse of thermoplastic composites can be leveraged to advance joining, disassembly, and reassembly of structures for space exploration activities. Potential applications include, but are not limited to, habitats and on-orbit assembly and reassembly of large-scale truss structures. This work focuses on demonstrating the feasibility of joining, disassembly, and reassembly of a thermoplastic bond using heat and pressure. Polyether ether ketone (PEEK) composite adherends were joined using low-melt polyaryl ether ketone (LM-PAEK) thermoplastic films at the bonding interface. The single lap shear specimens with LM-PAEK film were tested and had a maximum shear strength between 5 and 8 MPa and consistently failed adhesively at the bondline. Reassembly of disassembled specimens was successfully demonstrated using additional thermoplastic interlayers. Thus, the reassembly of thermoplastic composite joints was found to be feasible. However, additional work is required to reduce film flowout and optimize consolidation parameters for an in space environment.

thermoplastic composites↗
DOE OSTI2021

Joining Light Metals with Polymer Composites Through Metal Overcasting

This work investigates a unique technique to join aluminum (Al) and magnesium (Mg) alloys to carbon fiber reinforced polymer (CFRP) composites without the use of adhesives or mechanical fasteners. The joints were made using an overcasting technique where the molten alloys were cast around the polymer composites using high pressure die casting method. Rapid cooling during casting allowed the composite to be embedded inside the cast metal without causing any gross damage to the former even though the molten metal temperature exceeded the melting point of the composite matrix by several 100’s of deg. C. The metal/composite interface was examined using optical microscopy and x-ray imaging and the joint strength was examined through tensile testing. Although evidence of polymer melting was evident in the x-ray images, the embedded section of the composite coupons retained their overall shape and integrity. Preliminary tension tests on Al/CFRP composites showed strength degradation of the CFRP and it failed near the metal/CFRP interface (outside the joint). Strength degradation in the CFRP suggests that the overcasting process needs further optimization to minimize thermal excursion in the CFRP. Nevertheless, the overcasting process shows great promise as a unique joining technique with application in fabricating light-weight structures for automotive and transportation industries.

overcasting, Casting, Mg Castings, Al Casting, Joi↗
DOE OSTI2022

Joining technique for in-oven/autoclave molds manufactured by large scale polymer additive manufacturing

Large scale additive manufacturing (AM) of fiber-reinforced polymer composites has gained traction in the mold and die community over the last decade, largely due to reduced material cost and lead time. However, limitations in mold size remain present due to printer volume constraints and costs associated with large format machines. Here, this paper describes a method for producing additively manufactured polymer molds in segments with an O-ring joint design, which can be machined and subsequently assembled for autoclave applications. The developed joining mechanism allows for maintaining the vacuum integrity during the cure cycle while accounting for the anisotropic nature of the additively manufactured polymer molds. Over a range of tested temperatures, 20–200 °C, the multi-part mold joining design was able to achieve full vacuum of ∼73.7 cmHg (29 inchHg) and maintain a vacuum integrity with vacuum losses less than 1.5 cmHg/5min (0.6 inchHg).

Joining↗
DOE OSTI2023

Crack-Free Joining of High-Strength AA7055 Sheets by Friction Based Self-Piercing Riveting with the Aid of Numerical Design

Unique friction-based self-piercing riveting (F-SPR) was employed to join high-strength, low-ductility aluminum alloy 7055 for lightweight vehicle applications. This study aimed to maximize the joint strength of the AA7055 F-SPR joint while avoiding cracking issues due to low ductility at room temperature. A fully coupled Eulerian–Lagrangian (CEL) model was employed to predict the process temperature during F-SPR, and the temperature field was then mapped onto a 2D axisymmetric equivalent model for accelerated numerical analysis. The geometry, dimensions, and material strength of the rivet, as well as the depth of the die cavity and plunging depth, were investigated to enhance joint formation. Also, a static finite-element analysis model was developed to predict and analyze the stress distribution in the rivet under different mechanical testing loading conditions. Overall, the numerical model showed good agreement with the experiment results, such as joint formation and mechanical joint strength. With the aid of virtual fabrication through numerical modeling, the joint design iterations and process development time of F-SPR were greatly reduced regarding the goal of lightweight, high-strength aluminum joining.

36 MATERIALS SCIENCE↗
NASA NTRS1995

Plasma Enhanced Microwave Joining

A new method for plasma enhanced microwave joining of high purity (99.8%) alumina has been developed. The controlled application of a plasma between the adjoining surfaces of two rods permits the initial heating of low microwave absorbing alumina to sufficiently high temperatures where they can effectively absorb microwave energy. With this technology, the adjacent surfaces of alumina rods can be melted and welded together in less than three minutes using approximately 400 watts of microwave energy. Four point bending tests measured fracture strengths of up to 132 MPa at the joined interface.

microwave↗
DOE OSTI2024

Dissimilar material joining of densified superwood to aluminum by adhesive bonding

Abstract Superwood is a densified wood product that shows promise as a lightweight and renewable alternative for metallic materials. In order for this high-performance new material to be used in multi-material products, it must be able to be joined with other major materials. For example, joining superwood to aluminum would provide a key enabling technology for its use in automotive components since aluminum is presently a major lightweight material for such applications. In this paper, a methacrylate-based adhesive has been identified to provide high lap shear strength (7.5 MPa) for aluminum-to-superwood joints. The aluminum-to-superwood samples were prepared with different amounts of pre-polishing to create openings to the pores in the superwood so adhesive could penetrate into them and create a mechanical interlock, in addition to the hydrogen/chemical bonding at the surface between the methyl methacrylate (MMA) in methacrylate-based adhesive and the cellulose in superwood. For aluminum samples, a thin layer (typically a few nanometers) of oxide film on the surfaces provides hydrogen/chemical bond to MMA structure in the adhesive layer. The failure strength of the superwood-to-aluminum joint sample is about 50% higher than that of natural wood to natural wood joint sample and comparable to that of aluminum-to-aluminum joint sample.

Automation & Control Systems↗
DOE OSTI2021

Pulsed electric current joining of oxide-dispersion-strengthened austenitic steels

The solid-state joining of oxide-dispersion-strengthened (ODS) austenitic steels was achieved using a pulsed electric current joining (PECJ) process. Microstructures of the austenitic grain structures and oxide dispersions in the joint areas were characterized using electron microscopy. Negligible grain growth was observed in austenitic grain structures, while slight coarsening of oxide dispersions occurred at a short holding time. The mechanisms of the PECJ process may involve three steps that occur simultaneously, including the sintering of mechanical alloying powders in the bonding layer, formation of oxide dispersions, and bonding of the mechanical alloying powders with the base alloy. The high hardness and irradiation resistance of ODS alloys were retained in the joint areas. This research revealed the fundamental mechanisms during the PECJ process, which is beneficial for its potential applications during the advanced manufacturing of ODS alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Metallurgical Joining of immiscible system: Pure Mg and Pure Fe

Understanding the metallurgical joinability of pure Mg and pure Fe and their interfacial microstructure lays the foundation for deciphering the complicated mechanism of joining various magnesium alloys and steels in applications. We first produced a successful metallurgical joint between pure Mg and pure Fe using the friction stir assisted scribe technique. Through detailed characterization, we found that the two immiscible metals are bonded by a critical interfacial oxide layer that spans only ~40 ± 10 nm. We present the first direct experimental evidence of the presence of a Mg/Fe oxide rich interfacial layer using high-resolution electron microscopy and discuss the contribution of oxide formation toward a successful joining mechanism.

Das, Hrishikesh↗
DOE OSTI2025

On-Demand Column Joining for High Energy Physics

As the Large Hadron Collider (LHC) transitions into the High-Luminosity LHC (HL-LHC) era, the volume of data to be processed is expected to increase significantly. The CMS Experiment currently utilizes various data formats, including AOD, MiniAOD, and NanoAOD, each with different levels of detail and storage requirements. This paper addresses the challenges of data duplication and storage inefficiencies in high-energy physics (HEP) analyses by proposing an on-demand column-joining solution. This approach aims to reduce data duplication by enabling the dynamic combination of NanoAOD data with auxiliary information from larger data tiers, such as MiniAOD. The proposed solution leverages Trino, a high-performance distributed SQL query engine, to perform efficient and scalable data joins. Benchmarks using CMS OpenData demonstrate the feasibility of this approach, showing that it can handle large datasets with low latency. Integration with the scikit-hep ecosystem and the coffea analysis framework is also discussed, highlighting the potential for seamless end-to-end data processing and analysis. Ongoing and future work focuses on expanding benchmarks, integrating ServiceX for data transformation, and exploring the use of native object storage solutions.

Manganelli, Nicholas [Northeastern U.]↗
DOE OSTI2025

Dissimilar metal joining of Ti-6Al-4V and Inconel 625

The dissimilar joining of Ti-6Al-4V and Inconel 625 by using a suitable interlayer shows potential design flexibility by avoiding the brittle intermetallic phases from direct welding. These phases include NiTi , NiTi 2 , and Ni 3 Ti . The objective of this work is to facilitate laser welding of Ti-6Al-4V and Inconel 625 through a vanadium interlayer to form an intermetallic free, strong, and corrosion resistant joint. Vanadium was chosen based on binary phase diagram solubilities, literature, and theoretical CalPhaD calculations in PanDat. Laser welding was systematically explored from based on beam mode, offset, power, and scan speed. Varied parameters include laser power from 325 to 650 watts, laser scan speed from 80 to 160 in/min, and beam offset up to a ¼ of the beam diameter. Parameters were chosen based on previous dissimilar joining research and those found in the literature. Metallography, including optical and scanning electron microscopy, was used to analyze the weld chemical composition, grain structure, and defects through both the fusion and heat affected zones. The results and discussion will examine the relationship between process parameters, microstructure, and observed weld defects. Our findings will not only assess the weldability of vanadium and Inconel 625 but also establish a transferable framework for studying other dissimilar material combinations, providing valuable insights for future research in this field.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Modal Analysis of Ultrasonic Spot Welding for Lightweight Metals Joining

Ultrasonic spot welding (USW) represents one of the unique solid-state joining methods for lightweight materials such as magnesium alloy and aluminum alloy. However, the sonotrode vibration may have a detrimental impact on the sheet material and the existing welds, depending on the component geometry and vibration frequency. In this study, a modal analysis tool based on steady-state dynamics was developed for ultrasonic spot welding which features a cyclic load applied to the sheets during the joining process. Through predicting relative motion and shear stress at the faying surfaces, coupon geometry and weld spacing are identified as two major factors that affect the welding reliability and joint quality in USW. The model was validated via welding experiments on aluminum alloy and magnesium alloy and relevant characterization of temperature distribution, joint strength as well as fracture location.

36 MATERIALS SCIENCE↗
NASA NTRS1971

Method of joining metals of significantly different expansion rates

To join a refractory metal to a dissimilar high-temperature metal, braze a section of high elasticity, high ductility metal /such as columbium or columbium alloy/ between the metals to be joined, using a fork-type joint to hold the braze and transition member in place during expansion.

Caler, W.↗
NASA NTRS1973

Development of the weld-braze joining process

A joining process, designated weld-brazing, was developed which combines resistance spot welding and brazing. Resistance spot welding is used to position and aline the parts, as well as to establish a suitable faying-surface gap for brazing. Fabrication is then completed at elevated temperature by capillary flow of the braze alloy into the joint. The process was used successfully to fabricate Ti-6Al-4V alloy joints by using 3003 aluminum braze alloy and should be applicable to other metal-braze systems. Test results obtained on single-overlap and hat-stiffened panel specimens show that weld-brazed joints were superior in tensile shear, stress rupture, fatigue, and buckling compared with joints fabricated by conventional means. Another attractive feature of the process is that the brazed joint is hermetically sealed by the braze material, which may eliminate many of the sealing problems encountered with riveted or spot welded structures. The relative ease of fabrication associated with the weld-brazing process may make it cost effective over conventional joining techniques.

Bales, T. T.↗