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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

3D-printing methacrylate/chitin nanowhiskers composites via stereolithography: Mechanical and thermal properties

We report on the mechanical and thermal properties of stereolithography (SLA) 3D-printed methacrylate (MA) resin reinforced by chitin nanowhiskers (CNWs). CNWs were synthesized by acid hydrolysis of crab shell chitin and nanocomposites with 0 wt%, 0.5 wt%, 1.0 wt%, and 1.5 wt% CNWs loading were prepared by slurry compounding method. The obtained CNWs (diameter = 23 ± 5 nm, length = 253 ± 100 nm, and aspect ratio = 11 ± 3) are well dispersed within the bulk of MA at 1.0 wt% loading, implying good interfacial adhesion between the nanofiller and the resin matrix possibly due to hydrogen bonding interactions. The addition of up to 1.0 wt% CNWs to neat MA enhances the tensile strength, strain at break, modulus, and maximum thermal degradation temperatures of the nanocomposites. Moreover, the incorporation of CNWs not only improves the mechanical and thermal properties, but also preserves the excellent resolution and accuracy of 3D-printed MA/CNWs nanocomposites.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Tribological behavior of hybrid Aluminum-TiB 2 metal matrix composites for brake rotor applications

Here, this research investigates the feasibility of hybrid aluminum metal matrix composites (MMC) incorporating TiB 2 particles for brake rotor applications. The composites were produced by incorporating both in-situ, submicron-sized TiB 2 particles and regular micron-sized TiB 2 powders via stir and squeeze casting techniques into A206 aluminum alloy matrix. Systematic adjustments in the fractions of in-situ and ex-situ TiB 2 particles were conducted to evaluate their impact on wear behavior and mechanisms. Combination of both particle types allowed composites with up to 10 vol% of reinforcements. Composites with higher proportions of ex-situ particles demonstrated increased wear resistance compared to those solely composed of in-situ particles, control specimens without TiB 2 , and conventional cast iron counterparts. The lowest wear rate for the hybrid composites sliding against phenolic brake pads was 1.1 × 10 -5 mm 3 /Nm, signifying a 3-fold reduction relative to cast iron sliding against the same pads. Wear analysis elucidated distinctive mechanisms within the hybrid composites, characterized by mild fragmented abrasive wear, adhesive wear, and plastic deformation, accompanied by the formation of an intermixed tribo-oxide layer.

42 ENGINEERING↗
DOE OSTI2021

Development of coherent-precipitate-hardened high-entropy alloys with hierarchical NiAl/Ni 2 TiAl precipitates in CrMnFeCoNiAl x Ti y alloys

Coherent precipitates hardening is currently emerging strengthening mechanism of the various high entropy alloys (HEAs). Recently, CrMnFeCoNiAl x HEAs have been studied to show a phase transition from face-centered-cubic (FCC) to body-centered-cubic (BCC) and formation of coherent precipitates (B2-NiAl) within the BCC matrix. The coherent precipitates in the CrMnFeCoNiAl x alloys could contribute to increase the strength but lead to considerable reduction of the ductility. The present work systematically investigated a series of CrMnFeCoNiAl 0.5 Ti x alloys to further improve the strength and plasticity, as compared to the previously reported CrMnFeCoNiAl x HEAs. As a result, an increase of Ti addition leads to the phase transition from FCC to BCC and formation of lamellar structure and hierarchical precipitates reinforced by B2-NiAl and L2 1 -Ni 2 TiAl phases. Excellent mechanical properties were achieved from CrMnFeCoNiAl 0.5 Ti 0.1 and CrMnFeCoNiAl 0.5 Ti 0.2 alloys. Herein, the mechanical properties of the CrMnFeCoNiAl 0.5 Ti x alloys were discussed via theoretical strengthening mechanisms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Understanding the effect of refractory metal chemistry on the stacking fault energy and mechanical property of Cantor-based multi-principal element alloys

Multi-principal-element alloys (MPEAs) based on 3d-transition metals show remarkable mechanical properties. In this study, the stacking fault energy (SFE) in face-centered cubic (fcc) alloys is a critical property that controls underlying deformation mechanisms and mechanical response. Here, we present an exhaustive density-functional theory study on refractory- and copper-reinforced Cantor-based systems to ascertain the effects of refractory metal chemistry on SFE. We find that even a small percent change in refractory metal composition significantly changes SFEs, which correlates favorably with features like electronegativity variance, size effect, and heat of fusion. For fcc MPEAs, we also detail the changes in mechanical properties, such as bulk, Young's, and shear moduli, as well as yield strength. A Labusch-type solute-solution-strengthening model was used to evaluate the temperature-dependent yield strength, which, combined with SFE, provides a design guide for high-performance alloys. We also analyzed the electronic structures of two down-selected alloys to reveal the underlying origin of optimal SFE and strength range in refractory-reinforced fcc MPEAs. These new insights on tuning SFEs and modifying composition-structure-property correlation in refractory- and copper-reinforced MPEAs by chemical disorder, provide a chemical route to tune twinning- and transformation-induced plasticity behavior in fcc MPEAs.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Highly Recyclable Thermosets for Lightweight Composites

The objective of this project, Highly Recyclable Thermosets for Lightweight Composites (DOE Award DE-EE0009297), was to develop recyclable carbon fiber–reinforced polymer (CFRP) composites that are more energy efficient to produce than existing technologies while achieving superior mechanical performance and enabling closed-loop material recovery. Specifically, the project targeted vitrimer-based composites with tensile strength at least 20% higher than baseline recyclable polypropylene composites, retention of greater than 95% of tensile strength after multiple recycling and reprocessing cycles, recovery of carbonate monomers through depolymerization, and recovery of greater than 95% of carbon fibers of reusable quality. The project was carried out by The University of Akron in collaboration with Pacific Northwest National Laboratory and Raytheon Technologies Research Center.

36 MATERIALS SCIENCE↗
NASA NTRS1995

Low Frequency Guided Plate Waves Propagation in Fiber Reinforced Composites

Conventional destructive techniques for the determination of the elastic stiffness constants of composite materials can be costly and often inaccurate. Reliable nondestructive evaluation methods for monitoring the integrity of composite materials and structures are needed. Guided wave propagation in isotropic plate have been studied. Studies on the low frequency symmetric guide waves are presented.

applied mechanics and materials plate wave propaga↗
DOE OSTI2025

Manufacturing of Al-Ce/Metal-Matrix-Composites (MMC) for Harsh Environments

An integrated modeling/simulation and experimental approach will be used to design and synthesize Al-Ce/MMC for use in key technologies where improved energy efficiency and performance is harsh environments is required. Modeling and simulation work including thermodynamic modeling, DFT calculations, and continuum modeling of casting processes and mechanical behavior, will be combined with lab-scale synthesis to identify potential matrix and reinforcing phase compositions for large-scale synthesis. The experimental synthesis work will rely on lab-scale casting and gas atomization to identify the optimal matrix compositions for pilot/commercial-scale synthesis is Al-Ce/MMC. Selected Al-Ce/MMC will be synthesized by commercial scale melt processing, powder metallurgy and thermomechanical processing. The corrosion resistance, mechanical properties as a function of temperature, and thermal conductivity of the composites will be characterized to validate target properties are met or exceeded. This work will focus on two selected applications; however, the design framework will have broad applicability for composites for numerous harsh service condition applications. We will have synthesized Al-Ce/MMC that exhibit better performance in harsh environments than currently used materials.

36 MATERIALS SCIENCE↗
NASA NTRS1993

An overview of elevated temperature damage mechanisms and fatigue behavior of a unidirectional SCS-6/Ti-15-3 composite

The fatigue behavior of a unidirectionally reinforced titanium matrix composite (TMC), SiC/Ti-15-3, was thoroughly characterized to support life prediction modeling of advanced TMC disks designed for gas turbine engine applications. The results of this coupon-level experimental investigation are reviewed. On a stress basis, the isothermal fatigue behavior of the (0 deg) TMC revealed significant improvements over the unreinforced matrix. In contrast, the (90 deg) TMC exhibited degraded properties and lives for similar comparisons. This was attributed to the weak fiber/matrix interfacial bond. Encasing the (0 deg) TMC with a Ti-15-3 case did not affect isothermal fatigue lives at higher strain levels. However, at lower strain levels, rapid initiation and propagation of large fatigue cracks in the case degraded the fatigue lives. Thermomechanical fatigue (TMF) lives were significantly reduced for the (0 deg) TMC when compared to isothermal lives. At high strains, in-phase TMF produced extremely short lives. This degradation was attributed to fiber overload failures brought about by stress relaxation in the matrix. At low strains, out-of-phase TMF conditions became life limiting. Environment-assisted surface cracking was found to accelerate fatigue failure. This produced extensive matrix damage with minimal fiber damage. For the (90 deg) TMC, TMF conditions did not promote an additional degradation in cyclic life beyond that observed under isothermal conditions.

Castelli, Michael G.↗
DOE OSTI2025

Influence of Tibetan Plateau sensible heat on pre-monsoon dust burdens over South Asia: Observational and modeling evidence

Tibetan Plateau sensible heating (TPSH) effect is recognized as a key driver of the South Asian climate; however its role in regulating the regional dust burdens over South Asia during the pre-monsoon season remains unclear. Using long-term reanalysis and/or observational dust and TPSH data, we show that the dust optical depth at 550 nm (DOD 550 ) over South Asia is significantly positively correlated with TPSH at the interannual scale. DOD 550 over South Asia increases (decreases) by 20 % (12 %) in the strongest (weakest) TPSH years. The phenomenon of TPSH-dust relationships is reinforced by sensitivity experiments by altering TPSH from global climate models. Further mechanism analysis reveals that TPSH perturbation induces regional circulation anomalies over South Asia, which features a low-tropospheric cyclonic response around the Tibetan Plateau. This cyclonic anomaly strengthens the prevailing northwesterly winds, increasing regional dust emissions and transportation over South Asia. This novel mechanism helps understand the South Asian dust change.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Sizing comingled CF/PA 6 fibers with cellulose nanofibrils for enhanced performance properties

Compatibility between the reinforcing phase and the polymer matrix is critical to achieving the desired mechanical and thermal performance of composite materials. Several mechanisms can enhance this interfacial interaction, including surface treatments (e.g., oxidation, plasma, or irradiation), in-situ nanoparticle deposition, and fiber sizing. Here, in this study, cellulose nanofibrils (CNF) were employed as a sustainable sizing agent to modify the interface in commingled carbon fiber (CF)/polyamide 6 (PA 6) yarns, in which CF and PA6 filaments are intimately blended to enable simultaneous consolidation. A 0.25 wt% CNF aqueous suspension was applied under bath sonication to ensure uniform dispersion and minimize agglomeration. CNF-sized and unsized yarns were used to fabricate unidirectional composite plates via filament winding on a flat mandrel, followed by compression molding. Scanning electron microscopy confirmed CNF presence on both CF and PA6 filaments. CNF-sized composites exhibited increments in interlaminar shear strength (ILSS) by 50%, flexural strength by 11%, and tensile strength by 2.5% compared to unsized composites. Thermal analysis showed minimal changes in degradation temperature and crystallinity. These findings demonstrate that CNF sizing enhances interfacial bonding and mechanical performance, offering a scalable and environmentally friendly strategy for thermoplastic composite manufacturing along with yarn/tow handleability.

Cellulose nanofibrils (CNF)↗
DOE OSTI2024

Property Variations in Modern REBCO Coated Conductors from Multiple Manufacturers

The complex, multilayer structure of REBCO Coated Conductor (CC) poses significant challenges in the fabrication of high magnetic field devices where large stresses may initiate various forms of damage. Our goal is to peer below the cartoon representations of CC so that, amongst other things, we might better understand whether a CC from one manufacturer is interchangeable with that from another. This involves knowledge of a broad range of electromagnetic, geometric, microstructural, and J c (θ,B,T) properties, and their variations that collectively pose challenges for the fault tolerance of REBCO CC devices. Accordingly, comparative measurements of J c , visualization of flux penetration with Magneto-Optical Imaging (MOI), tape geometry from Scanning Electron Microscopy (SEM) of polished cross-sections, and extensive optical microscopy was performed on recently purchased samples from multiple manufacturers. Our analyses reveal many deviations from or characteristics absent from manufacturers’ specifications, while a comparison of different manufacturers’ mechanically and laser slit tapes shows a diverse array of slitting characteristics amongst the manufacturers and variation in properties those made to the same specification. Laser slit tapes from several manufacturers reveal ablated edges with damaged regions extending up to 50 μm, comparable to the damaged region found in the mechanically slit CC of this study. Overall, the aim of this study is to flesh out appropriate ways to understand the real conductor below the manufacturers’ cartoons to avoid surprises in our REBCO CC coil development program. The goal of this work was to perform a broad array of characterizations of the type needed for validation of purpose for making high field magnets: to our surprise we found a wide range of properties which greatly impact the mechanical strength and electromagnetic performance of solenoids composed of these conductors and reinforced the need for a broad characterization program for each conductor prior to its implementation.

Bradford, G.↗
DOE OSTI2024

X-Band Radar and Surface-Based Observations of Cold-Season Precipitation in Western Colorado’s Complex Terrain

Abstract Hydrologic processes associated with intermountain cold-season precipitation in the Upper Colorado River basin have important impacts on avalanche forecasting and water resource management. However, traditional weather radar networks struggle with observations in this complex terrain. Data collected during the Study of Precipitation, the Lower Atmosphere, and the Surface for Hydrometeorology (SPLASH) and its sister campaign, Surface Atmosphere Integrated Field Laboratory (SAIL) in the East River watershed of western Colorado, are used to examine a multistorm period from 23 December 2021 to 1 January 2022 that contributed 35% of the total winter precipitation in this watershed. Dual-polarization X-band radar and disdrometer measurements show ∼30-mm differences in precipitation amount at two sites in proximity over four distinct storm events within the period. Wind patterns, synoptic forcings, microphysical characteristics of precipitation, and surface meteorology are analyzed to explain the observed spatial variability of cold-season precipitation in complex mountainous terrain. Analysis shows that differences over time within this event are mainly accounted for by synoptic forcings, such as frontal passages; differences between sites are accounted for by the impact of variations in local wind patterns on precipitation microphysics. Patterns of surface precipitation intensity are compared and found to be correlated with X-band radar signatures; a relationship between a strong dendritic growth stage and intense low-density surface precipitation is reinforced by this study. This relationship demonstrates the importance of particle growth mechanisms on surface snowfall patterns in high-altitude complex terrain, underscoring the importance of realistic microphysical parameterizations. Significance Statement The amount and density of snowpack from western Colorado winter storms have significant impacts on water resources in the Upper Colorado River basin. Snowpack characteristics are affected by small-scale differences in how snow forms in the atmosphere. These differences are hard to study in the complex terrain of the Rockies, but data from the SPLASH and SAIL field campaigns allows us to investigate how snow crystal formation and mountain-driven wind patterns affect snow near the surface. Our study finds that snow crystal growth varies over small space and time scales and is likely controlled by the terrain beneath a given location and resultant local wind patterns. These results imply that predicting snowpack in the Rockies requires properly representing local wind patterns and crystal growth processes in models.

Heflin, Stella↗
NASA NTRS1979

Mechanical property degradation and chemical interactions in Borsic/titanium composite

A study was undertaken to identify the mechanisms of mechanical property degradation in a Borsic (silicon-carbide coated boron) fiber reinforced Ti-3Al-2.5V composite exposed to elevated temperature. Samples containing 0.45 volume fraction of fibers were exposed, in vacuum, to temperatures from 700 K to 1255 K for times up to 240 hours. Room temperature tensile properties of unidirectional material were determined in both the longitudinal and transverse directions, before and after high-temperature exposure. Electron micro-probe analysis, scanning electron microscopy, and X-ray diffraction were used to determine the compounds formed and the extent of interaction between the boron, SiC coating, and matrix materials.

Brewer, W. D.↗
NASA NTRS1983

Dynamic-mechanical response of graphite/epoxy composite laminates and neat resin

Dynamic mechanical measurement results are presented for the case of carbon fiber-reinforced, epoxy matrix composite laminates subjected to loading perpendicular to the lamination plane, as well as for neat epoxy resin under the same conditions, where temperatures ranged between 20 and 200 C and deformation levels lie within the linear viscoelastic region. In-phase and out-of-phase stiffnesses are found to become superposed, forming master curves that cover a 12-decade frequency range. The application of a master curve scaling procedure shows that the in-phase stiffness has the same shape, and out-of-phase stiffness has the same dispersion, for all laminates irrespective of stacking sequence and are, in turn, nearly identical to those for the neat epoxy resin. An empirical function is found for the relaxation modulus which, when converted to a dynamic modulus, yields good overall agreement for both of the dynamic stiffness components as a function of frequency.

Yang, P.↗
NASA NTRS1985

Active control of compressible flows on a curved surface

The effect of localized, time periodic surface heating and cooling over a curved surface is studied. This is a mechanism for the active control of unstable disturbances by phase cancellation and reinforcement. It is shown that the pressure gradient induced by the curvature significantly enhances the effectiveness of this form of active control. In particular, by appropriate choice of phase, active surface heating can completely stabilize and unstable wave.

Maestrello, L.↗
NASA NTRS1985

Fundamental Studies of Low Velocity Impact Resistance of Graphite Fiber Reinforced Polymer Matrix Composites

A study was conducted to relate the impact resistance of graphite fiber reinforced composites with matrix properties through gaining an understanding of the basic mechanics involved in the deformation and fracture process, and the effect of the polymer matrix structure on these mechanisms. It was found that the resin matrix structure influences the composite impact resistance in at least two ways. The integration of flexibilizers into the polymer chain structure tends to reduce the T sub g and the mechanical properties of the polymer. The reduction in the mechanical properties of the matrix does not enhance the composite impact resistance because it allows matrix controlled failure to initiate impact damage. It was found that when the instrumented dropweight impact tester is used as a means for assessing resin toughness, the resin toughness is enhanced by the ability of the clamped specimen to deflect enough to produce sufficient membrane action to support a significant amount of the load. The results of this study indicate that crossplied composite impact resistance is very much dependent on the matrix mechanical properties.

Bowles, K. J.↗
NASA NTRS1985

Active control of compressible flows on a curved surface

The effect of localized, time periodic surface heating and cooling over a curved surface is studied. This is a mechanism for the active control of unstable disturbances by phase cancellation and reinforcement. It is shown that the pressure gradient induced by the curvature significantly enhances the effectiveness of this form of active control. In particular, by appropriate choice of phase, active surface heating can completely stabilize an unstable wave.

Maestrello, L.↗