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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

Granular Media-Based Tunable Passive Vibration Suppressor

and vibration suppression device is composed of statically compressed chains of spherical particles. The device superimposes a combination of dissipative damping and dispersive effects. The dissipative damping resulting from the elastic wave attenuation properties of the bulk material selected for the granular media is independent of particle geometry and periodicity, and can be accordingly designed based on the dissipative (or viscoelastic) properties of the material. For instance, a viscoelastic polymer might be selected where broadband damping is desired. In contrast, the dispersive effects result from the periodic arrangement and geometry of particles composing a linear granular chain. A uniform (monatomic) chain of statically compressed spherical particles will have a low-pass filter effect, with a cutoff frequency tunable as a function of particle mass, elastic modulus, Poisson fs ratio, radius, and static compression. Elastic waves with frequency content above this cutoff frequency will exhibit an exponential decay in amplitude as a function of propagation distance. System design targeting a specific application is conducted using a combination of theoretical, computational, and experimental techniques to appropriately select the particle radii, material (and thus elastic modulus and Poisson fs ratio), and static compression to satisfy estimated requirements derived for shock and/or vibration protection needs under particular operational conditions. The selection of a chain of polymer spheres with an elastic modulus .3 provided the appropriate dispersive filtering effect for that exercise; however, different operational scenarios may require the use of other polymers, metals, ceramics, or a combination thereof, configured as an array of spherical particles. The device is a linear array of spherical particles compressed in a container with a mechanism for attachment to the shock and/or vibration source, and a mechanism for attachment to the article requiring isolation (Figure 1). This configuration is referred to as a single-axis vibration suppressor. This invention also includes further designs for the integration of the single-axis vibration suppressor into a six-degree-of-freedom hexapod "Stewart"mounting configuration (Figure 2). By integrating each singleaxis vibration suppressor into a hexapod formation, a payload will be protected in all six degrees of freedom from shock and/or vibration. Additionally, to further enable the application of this device to multiple operational scenarios, particularly in the case of high loads, the vibration suppressor devices can be used in parallel in any array configuration.

Dillon, Robert P.↗
DOE OSTI2017

Nanoindentation study of bulk zirconium hydrides at elevated temperatures

Here, the mechanical properties of zirconium hydrides was studied using nano-indentation technique at a temperature range of 25 – 400 °C. Temperature dependency of reduced elastic modulus and hardness of δ- and ε-zirconium hydrides were obtained by conducting nanoindentation experiments on the bulk hydride samples with independently heating capability of indenter and heating stage. The reduced elastic modulus of δ-zirconium hydride (H/Zr ratio =1.61) decreased from ~113 GPa to ~109 GPa while temperature increased from room temperature to 400°C. For ε-zirconium hydrides (H/Zr ratio=1.79), the reduced elastic modulus decreased from 61 GPa to 54 GPa as temperature increased from room temperature to 300 °C. Whereas, hardness of δ-zirconium hydride significantly decreased from 4.1 GPa to 2.41 GPa when temperature increased from room temperature to 400 °C. Similarly, hardness of ε-zirconium hydride decreased from 3.06 GPa to 2.19 GPa with temperature increase from room temperature to 300°C.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Study of dynamic properties for NaK binary liquid alloy using first principle and theoretical predictions of isothermal bulk modulus using elastic constants

Study of atomic motions in the binary liquid alloys have been studied in terms of dynamical variables like velocity auto correlation, power spectrum and mean square displacement. Elastic constants and isothermal bulk modulus have been calculated to see the effeectiveness of ab-initio pseudopotentials which has been used in this paper. This appraoch is free from the fitting parameters and results obtained using this appraoch have been found very close to the average values.

36 MATERIALS SCIENCE↗
NASA NTRS2007

Mechanical Properties of Cells

Many physiologic and pathologic processes alter the biomechanical properties of the tissue they affect, and these changes may be manifest at the single cell level. The normal and abnormal mechanical properties of a given cell type can be established with the aid of an atomic force microscope (AFM), nonetheless, consistency in the area of the tip has been a mayor limitation of using the AFM for quantitative measurements of mechanical properties. This project attempts to overcome this limitation by using materials with a known elastic modulus, which resembles the one of the cell, to create force-deformation curves to calculate the area of indentation by means of Hooke s Law (sigma = E(epsilon)), which states that stress (sigma) is proportional to the strain (epsilon) where the constant of proportionality, E, is called the Young s modulus, also referred as the elastic modulus. Hook s Law can be rearranged to find the area of indentation (Area= Force/ E(epsilon)), where the indentation force is defined by the means of the added mass spring calibration method.

Bradley, Robert↗
DOE OSTI2017

Molecular weight and uniformity define the mechanical performance of lignin-based carbon fiber

Lignin-based carbon fiber represents a renewable and low-cost alternative to petroleum-based carbon fiber. However, the poor mechanical performance of current lignin carbon fiber hinders its application. We hypothesized that the lower optimal mechanical performance is caused by the inherent heterogeneity of lignin. It is still unknown how the molecular weights (MWs) and lignin uniformity will impact the performance of lignin carbon fiber. We thereby addressed this hypothesis by fractionating lignin into fractions with different MWs and polydispersity indices (PDIs). An enzyme–mediator-based method and a dialysis method were developed to derive lignin fractions with increased MW and decreased PDI. Lignin fractions were electro-spun into fibers after blending with polyacrylonitrile (PAN) at 1 : 1 (w/w) ratio. The fractionation in general improved the spinnability of lignin to allow us to obtain finer lignin-based carbon fibers. The elastic modulus of lignin carbon fibers, as measured by nanoindentation, was increased as the lignin MW increased and as PDI decreased. The scatter plot and linear regression revealed very good correlation between the elastic modulus and PDI, as well as certain correlation between the elastic modulus and MW. XRD and Raman spectroscopy revealed that the crystallite size and the content of the pre-graphitic turbostratic carbon increased with higher lignin MW and lower PDI, revealing the mechanism of the improvement in carbon fiber mechanical performance. Finally, this study elucidated the impacts of lignin MW and uniformity on the mechanical properties of carbon fiber, and could thus guide the development of lignin processing technologies for quality lignin-based carbon fiber.

09 BIOMASS FUELS↗
DOE OSTI2018

Correlation between structural and mechanical properties of RF magnetron sputter deposited hydroxyapatite coating

Highlights: • Microstructure and mechanical properties of textured hydroxyapatite (HA) coatings were evaluated. • TEM results revealed two types of coating microstructure corresponding to the film texture. • Elastic performance of the coating was determined by the texture of the HA coating. • HA coating with (300) texture showed larger elastic recovery. - Abstract: In the present study hydroxyapatite (HA) thin films with a,b-plain and c-plain preferential orientation were prepared by means of RF-magnetron sputtering with water vapor addition into a working gas atmosphere to investigate the influence of microstructural features on mechanical performance of the coating at nanoscale. The mechanical properties of the HA coatings textured along a,b- and c-axes by nanoindentation conclusively highlight that elastic modulus, H/E ratio, H{sup 3}/E{sup 2} parameter and percent of elastic recovery are determined by preferential orientation of the film. Nanoindentation reveals that the HA films exhibiting (300) texture possess commensurate nanohardness and lower elastic modulus compared to (002) oriented films, indicating that the former films possess higher resistance to cracking. The (002) and (300) textured coatings exhibited a nanohardness of 4.7 ± 2.0 GPa and 4.4 ± 2.2 GPa, respectively. The elastic modulus of the HA film with (300) and (002) preferential orientation was 75 ± 40 GPa and 103 ± 40 GPa, respectively. The HA coating with (300) texture showed a higher percentage of elastic recovery of 92% within unloading than that of the (002) textured film (69%).

36 MATERIALS SCIENCE↗
DOE OSTI2015

Effects of hypergravity on adipose-derived stem cell morphology, mechanical property and proliferation

Alteration in specific inertial conditions can lead to changes in morphology, proliferation, mechanical properties and cytoskeleton of cells. In this report, the effects of hypergravity on morphology of Adipose-Derived Stem Cells (ADSCs) are indicated. ADSCs were repeatedly exposed to discontinuous hypergravity conditions of 10 g, 20 g, 40 g and 60 g by utilizing centrifuge (three times of 20 min exposure, with an interval of 40 min at 1 g). Cell morphology in terms of length, width and cell elongation index and cytoskeleton of actin filaments and microtubules were analyzed by image processing. Consistent changes observed in cell elongation index as morphological change. Moreover, cell proliferation was assessed and mechanical properties of cells in case of elastic modulus of cells were evaluated by Atomic Force Microscopy. Increase in proliferation and decrease in elastic modulus of cells are further results of this study. Staining ADSC was done to show changes in cytoskeleton of the cells associated to hypergravity condition specifically in microfilament and microtubule components. After exposing to hypergravity, significant changes were observed in microfilaments and microtubule density as components of cytoskeleton. It was concluded that there could be a relationship between changes in morphology and MFs as the main component of the cells. - Highlights: • Hypergravity (10 g, 20 g, 40 g and 60 g) affects on adipose derived stem cells (ADSCs). • ADSCs after exposure to the hypergravity are more slender. • The height of ADSCs increases in all test groups comparing their control group. • Hypergravity decreases ADSCs modulus of elasticity and cell actin fiber content. • Hypergravity enhances proliferation rate of ADSCs.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Comparative investigation on microstructures and mechanical properties of (TiB + TiC)/Ti-6Al-4V composites from Ti-B4C-C and Ti-TiB2-TiC systems

Highlights: • The (TiB{sub w}+TiC{sub p})/Ti-6Al-4V composites were fabricated from Ti-B{sub 4}C-C and Ti-TiB{sub 2}-TiC systems by reactive hot-pressed sintering. • Microstructures and mechanical properties of the two kinds of composites were comparatively investigated. • The composites from Ti-TiB{sub 2}-TiC system possess higher elastic modulus and Vickers hardness than those from Ti-B{sub 4}C-C system. • The composites from Ti-TiB{sub 2}-TiC system have higher bending strength than the other system while employing same conditions. • The composites from Ti-B{sub 4}C-C system present better abrasion resistance than those from Ti-TiB{sub 2}-TiC system. - Abstract: Two percentages of TiB + TiC reinforced Ti-6Al-4V composites from Ti-B{sub 4}C-C and Ti-TiB{sub 2}-TiC systems were fabricated by reactive hot-pressed sintering. Their microstructures and mechanical properties involving elastic modulus, Vickers hardness, bending strength and wear property were investigated comparatively. The experimental results show that needle-like TiB whiskers and near-equiaxed TiC particles are evenly distributed in the Ti-6Al-4V matrix. The mechanical properties of the (TiB + TiC)/Ti-6Al-4V composites are closely related with the nominal composition and synthesis system of TiB + TiC reinforcement and the microstructures of composites. With increasing the nominal volume fraction of reinforcement, both elastic modulus and Vickers hardness increase more or less and the bending strength decreases in varying degrees. A certain increase of pores in the composites with the sintering temperature increasing to 1300 °C can markedly affect the bending strength. Moreover, no matter what the sintering temperature and nominal volume fraction of reinforcement, the elastic modulus and Vickers hardness of composites from the Ti-TiB{sub 2}-TiC system are higher than those from the Ti-B{sub 4}C-C system. Similarly, the composites from the Ti-B{sub 4}C-C system present better abrasion resistance than those from the Ti-TiB{sub 2}-TiC system due to the difference of interfacial bonding between the TiC particles and Ti-6Al-4V matrix in the two kinds of composites.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Nanoscale characterization of the biomechanical properties of collagen fibrils in the sclera

We apply the PeakForce Quantitative Nanomechanical Property Mapping (PFQNM) atomic force microscopy mode for the investigation of regional variations in the nanomechanical properties of porcine sclera. We examine variations in the collagen fibril diameter, adhesion, elastic modulus and dissipation in the posterior, equatorial and anterior regions of the sclera. The mean fibril diameter, elastic modulus and dissipation increased from the posterior to the anterior region. Collagen fibril diameter correlated linearly with elastic modulus. Our data matches the known macroscopic mechanical behavior of the sclera. We propose that PFQNM has significant potential in ocular biomechanics and biophysics research.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Effect of Age and Cytoskeletal Elements on the Indentation-Dependent Mechanical Properties of Chondrocytes

Articular cartilage chondrocytes are responsible for the synthesis, maintenance, and turnover of the extracellular matrix, metabolic processes that contribute to the mechanical properties of these cells. Here, we systematically evaluated the effect of age and cytoskeletal disruptors on the mechanical properties of chondrocytes as a function of deformation. We quantified the indentation-dependent mechanical properties of chondrocytes isolated from neonatal (1-day), adult (5-year) and geriatric (12-year) bovine knees using atomic force microscopy (AFM). We also measured the contribution of the actin and intermediate filaments to the indentation-dependent mechanical properties of chondrocytes. By integrating AFM with confocal fluorescent microscopy, we monitored cytoskeletal and biomechanical deformation in transgenic cells (GFPvimentin and mCherry-actin) under compression. We found that the elastic modulus of chondrocytes in all age groups decreased with increased indentation (15–2000 nm). The elastic modulus of adult chondrocytes was significantly greater than neonatal cells at indentations greater than 500 nm. Viscoelastic moduli (instantaneous and equilibrium) were comparable in all age groups examined; however, the intrinsic viscosity was lower in geriatric chondrocytes than neonatal. Disrupting the actin or the intermediate filament structures altered the mechanical properties of chondrocytes by decreasing the elastic modulus and viscoelastic properties, resulting in a dramatic loss of indentation-dependent response with treatment. Actin and vimentin cytoskeletal structures were monitored using confocal fluorescent microscopy in transgenic cells treated with disruptors, and both treatments had a profound disruptive effect on the actin filaments. Here we show that disrupting the structure of intermediate filaments indirectly altered the configuration of the actin cytoskeleton. These findings underscore the importance of the cytoskeletal elements in the overall mechanical response of chondrocytes, indicating that intermediate filament integrity is key to the non-linear elastic properties of chondrocytes. This study improves our understanding of the mechanical properties of articular cartilage at the single cell level.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1991

Oxynitride glass fibers

Research at the Army Materials Technology Laboratory (AMTL) and elsewhere has shown that many glass properties including elastic modulus, hardness, and corrosion resistance are improved markedly by the substitution of nitrogen for oxygen in the glass structure. Oxynitride glasses, therefore, offer exciting opportunities for making high modulus, high strength fibers. Processes for making oxynitride glasses and fibers of glass compositions similar to commercial oxide glasses, but with considerable enhanced properties, are discussed. We have made glasses with elastic moduli as high as 140 GPa and fibers with moduli of 120 GPa and tensile strengths up to 2900 MPa. AMTL holds a U.S. patent on oxynitride glass fibers, and this presentation discusses a unique process for drawing small diameter oxynitride glass fibers at high drawing rates. Fibers are drawn through a nozzle from molten glass in a molybdenum crucible at 1550 C. The crucible is situated in a furnace chamber in flowing nitrogen, and the fiber is wound in air outside of the chamber, making the process straightforward and commercially feasible. Strengths were considerably improved by improving glass quality to minimize internal defects. Though the fiber strengths were comparable with oxide fibers, work is currently in progress to further improve the elastic modulus and strength of fibers. The high elastic modulus of oxynitride glasses indicate their potential for making fibers with tensile strengths surpassing any oxide glass fibers, and we hope to realize that potential in the near future.

Patel, Parimal J.↗
NASA NTRS1980

Film thickness for different regimes of fluid-film lubrication

Film thickness equations are provided for four fluid-film lubrication regimes found in elliptical contacts. These regimes are isoviscous-rigid; viscous-rigid; elastohydrodynamic lubrication of low-elastic-modulus materials (soft EHL), or isoviscous-elastic; and elastohydrodynamic lubrication of high-elastic-modulus materials (hard EHL), or viscous-elastic. The influence or lack of influence of elastic and viscous effects is the factor that distinguishes these regimes. The results are presented as a map of the lubrication regimes, with film thickness contours on a log-log grid of the viscosity and elasticity for three values of the ellipticity parameter.

Hamrock, B. J.↗
NASA NTRS1975

Determination of mechanical properties of polymer film materials

Five polymeric film materials, Tedlar, Teflon, Kapton H, Kapton F, and a fiberglass reinforced polyimide, PG-402, in thickness ranging from 0.002 to 0.005 inch, were tested over a temperature range of -195 to 200 C in the "machine" and transverse direction to determine: elastic modulus, Poisson's ratio, three percent offset yield stress, fracture stress, and strain to fracture. The elastic modulus, yield stress and fracture stress decreased with increasing temperature for all the materials while the fracture strain increased. Teflon and Tedlar had the greatest temperature dependence and PG-402 the least. At 200 C the Poisson ratio values ranged from 0.39 to 0.5; they diminished as the temperature decreased covering a range of 0.26 to 0.42 at -195 C. Shortening the gauge length from eight inches to one inch increased the strain to fracture and lowered the elastic modulus values.

Hughes, E. J.↗
DOE OSTI2024

Effect of laminae count and manufacturing methods on mechanical properties of thin‐ply woven composites

Abstract Thin‐ply woven composites exhibit exceptional mechanical performance by delaying the onset of damage, making them suitable for high‐performance structural applications. This study outlines the impact of manufacturing techniques (vacuum bagging and hot pressing), ply count, and fiber waviness on the mechanical properties of aromatic thermosetting copolyester/carbon‐fiber (ATSP/CF) composites. The analysis encompasses several different ply counts, evaluating their effects on the in‐plane elastic modulus (0°–90°) and tensile strength. Results demonstrate that reducing the waviness (or crimp) ratio significantly enhances the in‐plane elastic modulus, with improvements up to 188%, highlighting the importance of fiber alignment. Vacuum bagging produced ply thicknesses from 128 to 58 μm for 1–36 plies, with in‐plane elastic moduli from 30.3 to 87.2 GPa, and 4‐ and 8‐ply samples showed approximately 40% higher stiffness than those made by hot pressing. ATSP resin with high thermal stability (up to 400°C) and recyclability was used. Furthermore, this study highlights the microstructural enhancements achieved through vacuum bagging, as revealed by scanning electron and optical microscopy, and micro‐computed tomography imaging. This paper provides insights into damage mitigation and achieving enhanced mechanical properties by controlling fiber waviness using vacuum bagging and higher ply count in thin‐ply ATSP/CF composites. Highlights Crimp ratio reduction enhances elastic in‐plane elastic modulus up to 188%. Vacuum bagging increases modulus over the hot pressing manufacturing method by 40%. Lowering thickness‐per‐ply increases failure strain from 0.8% to 1.2%. Explored the performance of a novel ATSP matrix with high recyclability and thermal stability.

Kushwaha, Shashank [The Grainger College of Engine↗
DOE OSTI2018

3D Modeling Effect of Spherical Inclusions on the Magnetostriction of Bulk Superconductors

In this paper, the dependence of the effective magnetostriction of bulk superconductors on the elastic parameters including the volume fraction and elastic modulus ratio is studied by a three-dimensional model consisting of a spherical inclusion–superconducting matrix system. The effect of the elastic modulus and volume fraction on the magnetostriction is also obtained through the magnetostriction loop. The results indicate that the elastic modulus and volume fraction have obvious effects on the effective magnetostriction of the superconducting composite, which gives an explanation about the differences between the experimental and the theoretical results. Furthermore, it is worth pointing out that the linear field dependence of magnetostriction is unique to the Bean model by comparing the curve shapes of the magnetostriction loop with and without inclusion.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Role of Carbon Bridge Length of Organosilicate Precursors on the Atmospheric Plasma Deposition of Transparent Bilayer Protective Coatings on Plastics

Here, we demonstrate the deposition of transparent organosilicate protective bilayer coatings on poly methyl methacrylate (PMMA) substrates with different carbon chain length dipodalsilane precursors using atmospheric plasma deposition in ambient air. The bottom adhesive layer was a hybrid organosilicate coating deposited using either only carbon bridge organosilicate precursor or accompanied with a ring structure 1,5-cyclooctadiene precursor. The top layer was a dense silica coating with high elastic modulus and hardness deposited with only carbon bridge precursor. The adhesion energy of bottom layer increased with increasing carbon bridge length of precursors while the density, hardness, and elastic modulus of top hard layer decreased. The deposited bilayer structure showed ~3 times the adhesion energy and four times the elastic modulus of commercial polysiloxane sol–gel coatings.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Inverse measurement of stiffness by the normalization technique for J-integral fracture toughness

The single specimen normalization technique for J-integral fracture toughness has been successfully employed by several researchers to study the strongly non-linear fracture response of ductile semicrystalline polymers. As part of the normalization technique the load and the plastic component of displacement are normalized. The normalized data is then fit with a normalization function that approximates a power law for small displacements that are dominated by blunting and smoothly transitions to a linear relationship for large displacements that are dominated by stable crack extension. Particularly for very ductile polymers the compliance term used to determine the plastic displacement can dominate the solution and small errors in determining the elastic modulus can lead to large errors in the normalization or even make it ill-posed. This can be further complicated for polymers where the elastic modulus is strong strain rate dependent and simply using a 'quasistatic' modulus from a dogbone measurement may not equate to the dominant strain rate in the compact tension specimen. The current work proposes directly measuring the compliance of the compact tension specimen in the solution of J-integral fracture toughness and then solving for the elastic modulus. By comparison with a range of strain rate data the dominant strain rate can then be determined.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Tensile Modeling PVC Gels for Electrohydraulic Actuators

Polyvinyl chloride (PVC)-dibutyl adipate (DBA) gels are a fascinating dielectric elastomer actuator showing promise in soft robotics. When actuated with high voltages, the gel deforms towards the anode. A recent application of PVC gels in electrohydraulic actuators motivates elastic and hyperelastic constitutive relationships for tensile loading modes. PVC gels with plasticizer-to-polymer weight ratios of 2:1, 4:1, 6:1, and 8:1 w/w were evaluated. PVC gels exhibit a linear elastic region up to 25% strain. The elastic modulus decreased with increasing plasticizer content from 288.8 kPa, 56.1 kPa, 24.7 kPa, to 11 kPa. Poisson’s ratio also decreased with increasing plasticizer content from 0.42, 0.43, 0.39, to 0.35. We suggest that the decrease in polymer concentration facilitates a weakly interconnected polymer network susceptible to chain slippage that hinders the network response, thus lowering Poisson’s ratio. Our work suggests that PVC gels can be treated as isotropic and incompressible for large strains and hyperelastic modeling; however, highly plasticized gels tend to act less incompressible at small strains. The power scaling law between the elastic modulus and plasticizer weight ratio showed high agreement, making the elastic modulus deterministic for any plasticizer content. The Neo–Hookean, Mooney–Rivlin, Yeoh, Gent, Ogden, and extended tube hyperelastic constitutive models are investigated. The Yeoh model shows the highest feasibility when evaluated up to 3.5 stretch, showing a maximum normalized root-mean-square-error of 6.85%. Together, these findings establish a constitutive basis for PVC-DBA gels, incorporating small strain elasticity, large strain non-linear behavior, and network analysis while providing suggestive insight into the network structure required for accurately modeling the EPIC.

Polymer Science↗