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Results for “Compressive Strength”

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 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

The Influence of Mechanical Treatment on the Surface Relief of a Fe{sub 77}Ni{sub 1}Si{sub 9}B{sub 13} Metal Glass

The micro- and nanoreliefs of the loaded surfaces of a Fe{sub 77}Ni{sub 1}Si{sub 9}B{sub 13} metal glass are probed via scanning tunneling and atomic force microscopies, scanning electron microscopy, and X-ray fluorescence. The fractal characteristics of surfaces are evaluated via the multifractal approach. As found, the variations in a singularity spectrum width, calculated from the tunneling and atomic force microscopies, may be useful for predicting the forthcoming fracture. An increase in the breaking strength of ribbons subjected to hydrostatic compression is due to decreasing microporosity of a near-surface layer, which corresponds to the surface smoothing.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Age-aware materials model for foam cushions - considering time-dependence of strain-rates and rate-independent measurements

Over the last few reports we have chronicled the progressive development of an age-aware materials model for foam cushions relevant to our systems. The latest version employs a N = 2 Ogden Hyperfoam model within a two-network Tobolsky scheme. As the material ages, the first network progressively loses in strength, while the second network progressively gains in strength. However, the two networks are in different strain states. Thus, in additive equilibrium (Tobolsky model) they manifest both permanent structural changes (measured as Compression Set) as well as changes in mechanical strength and modulus (measured as Load Retention).

36 MATERIALS SCIENCE↗
DOE OSTI2024

Final Scientific/Technical Report Rapid Design and Manufacturing of High-Performance Materials for Turbine Blades

This research demonstrated the concept of carbide precipitation-strengthened refractory high entropy alloys (RHEA). The advantage of a precipitation strengthened alloy is all phases are in thermodynamic equilibrium promoting microstructural stability, and consequently retention of properties at elevated temperatures. Additionally, as with any precipitation strengthened – or age hardened alloy, components can be heat-treated after manufacturing to manipulate the microstructure and optimize properties for performance. This is an advantage of the precipitation strengthened alloys over composites and ceramics materials, where the microstructure and properties are essentially fixed upon the initial materials manufacturing stage. High throughput (HT), multi-scale computer modeling was used to identifying novel RHEA compositions with desired characteristics needed for precipitation strengthening. The results showed that carbides precipitated and consequently, the strength of the alloys (measured in compression) increased after heat-treatment, which is the desired effect. The project also demonstrated the feasibility of producing articles from RHEA by additive manufacturing (AM).

36 MATERIALS SCIENCE↗
DOE OSTI2024

Rapid Design and Manufacturing of High-Performance Materials for Turbine Blades

This research demonstrated the concept of carbide precipitation-strengthened refractory high entropy alloys (RHEA). The advantage of a precipitation strengthened alloy is all phases are in thermodynamic equilibrium promoting microstructural stability, and consequently retention of properties at elevated temperatures. Additionally, as with any precipitation strengthened – or age hardened - alloy, components can be heat-treated after manufacturing to manipulate the microstructure and optimize properties for performance. This is an advantage of the precipitation strengthened alloys over composites and ceramics materials, where the microstructure and properties are essentially fixed upon the initial materials manufacturing stage. High throughput (HT), multi-scale computer modeling was used to identifying novel RHEA compositions with desired characteristics needed for precipitation strengthening. Designs were validated by producing small ingots via are melting. The results showed that carbides precipitated and consequently, the strength of the alloys (measured in compression) increased after heat-treatment, which is the desired effect. The project also demonstrated the feasibility of producing articles from RHEA by additive manufacturing (AM). Electron beam melting (EBM) and laser direct energy deposition (L-DED) additive manufacturing methods, were explored with various processing parameters were interrogated for both methods. Sound (crack-free and dense) precipitation strengthened RHEA samples were produced via EDM AM, demonstrating the feasibility of the concept.

36 MATERIALS SCIENCE↗
NASA NTRS1978

Buckling and structural efficiency of sandwich-blade stiffened composite compression panels

The minimum mass structural efficiency curve was determined for sandwich blade stiffened composite compression panels subjected to buckling and strength constraints. High structural efficiencies are attainable for this type of construction. A method of analysis is presented for the buckling of panels of this configuration which shows that buckling of such panels is strongly dependent on the through-the-thickness transverse shearing of the stiffener. Experimental results are presented and compared with theory.

Stein, M.↗
NASA NTRS1981

Studies of new perfluoroether elastomeric sealants

Channel and filleting sealants were developed successfully from cyano and diamidoxime terminated perfluoro alkylene ether prepolymers. The prepolymers were polymerized, formulated and tested. The polymers and/or formulations therefrom were evaluated as to their physical, mechanical and chemical properties (i.e., specific gravity, hardness, nonvolatile content, corrosion resistance, stress corrosion, pressure rupture resistance, low temperature flexibility, gap sealing efficiency, tensile strength and elongation, dynamic mechanical behavior, compression set, fuel resistance, thermal properties and processability). Other applications of the formulated polymrs and incorporation of the basic prepolymers into other polymeric systems were investigated. A cyano terminated perfluoro alkylene oxide triazine was formulated and partially evaluated. The channel sealant in its present formulation has excellent pressure rupture resistance and surpasses present MIL specifications before and after fuel and heat aging.

Basiulis, D. I.↗
NASA NTRS1984

Evaluation of long-duration exposure to the natural space environment on graphite-polyimide and graphite-epoxy mechanical properties (A0175)

The primary objective of this experiment is to accumulate the needed operational data associated with the exposure of graphite-polyimide and graphite-epoxy material to the environments of space. The experiment will be mounted in two 3-in.-deep peripheral trays. Graphite-polyimide specimens will occupy 1 1/3 trays and the graphite-epoxy specimens will occupy two-thirds of a tray. The experiment approach requires two matched sets of specimens with traceable records that are maintained for materials processing and specimen quality. After fabrication, one set of each test specimen will be sectioned and structurally tested to serve as a data baseline. After the flight, the other set of specimens will undergo extensive measurements of mechanical properties for comparison with the original data baseline. Structural testing of the graphite-polyimide specimens will provide strength and elastic data in tension, compression, and shear. Transverse tension microcracking and crack propagation will be evaluated by photomicroscopy. Structural testing of the graphite-epoxy specimens will include verification of laminate, core, adhesive, and fatigue properties as applied to the design and analysis of the payload bay door. Microcracking and crack propagation will also be analyzed by photomicroscopy.

Powell, J. H.↗
NASA NTRS1985

Hgi2 Sub 2 Crystal Growth for Nuclear Detectors

The objectives of this program are to obtain a benchmark quality sample grown at low-g conditions and to study vapor growth phenomena under space conditions. Ground-based crystals show a defect structure which impairs their performance as nuclear radiation detectors. These defects may be caused by the gravitational force acting on the crystal in its weakended state at the elevated growth temperature and by irregular convection patterns in the vapor during growth. Mechanical strength measurements have been performed (uniaxial compression tests) which show that the crystals exhibit slip parallel to the c-planes at stresses as low as 1/2 psi. Preliminary calculations using a simple linearized model indicate the oscillating instabilities in the convection part of the vapor transport system are unlikely, even at 1-g, provided that the utmost care is taken in the preparation of the crystal growth source material.

Schnepple, W. F.↗
NASA NTRS1986

On the influence of an external electric field on magnetotail reconnection

Magnetotail reconnection is studied under the influence of a dawn to dusk electric field applied at the high-latitude tail boundary using a two-dimensional resistive MHD code. It is found that the basic unstable sequence of tearing and plasmoid formation and ejection was not changed if the external electric field was fairly uniform. The externally forced compression, however, could shorten the onset time and the growth time of the evolution. The faster growth can be understood by the fact that the forced compression gradually alters the lobe field strength and the plasma sheet width and reduces thereby the relevant Alfven time. In fact, if the evolution of the cases with imposed electric field is rescaled on the basis of these characteristic parameters, a good quantitative agreement with the case without external electric field is found.

Birn, J.↗
NASA NTRS1989

Polyimide Matrix composites: Polyimidesulfone/LARC-TPI (1:1) blend

Polyimide matrix composites were fabricated from unidirectional unsized AS-4 carbon fiber and a doped 1:1 blend of two polyimides: benzophenone dianhydride-3,3'-diamino diphenylsulfone (PISO2) and benzophenone dianhydride-3,3'-diamino benzophenone (LARC-TPI). To enhance melt flow properties, the molecular weight of the PISO2 was controlled by end-capping with phthalic anhydride and addition of 5 percent by weight p-phenylene diamine-phthalic anhydride bisamic acid dopant. Prepreg was drum-wound using a diglyme slurry comprised of the soluble polyamideacid of PISO2, the soluble bisamideacid of the dopant, and the insoluble imidized LARC-TPI powder. Melt flow studies with a rotary rheometer and parallel plate plastometer on neat resin and prepreg helped develop an optimum cure cycle. Composite mechanical properties at room and elevated temperatures, dry and moisture-saturated, were evaluated, including short beam shear strength and flexure, tensile, shear, and compression properties. Two 18 in. x 24 in. skin-stringer panels were fabricated, one of which was tested in compression to failure.

Johnston, Norman J.↗
NASA NTRS1989

Polyimide matrix composites - Polyimidesulfone/LARC-TPI (1:1) blend

Polyimide matrix composites were fabricated from unidirectional unsized AS-4 carbon fiber and a doped 1:1 blend of two polyimides: PISO2 and LARC-TPI. To enhance melt flow properties, the molecular weight of the PISO2 was controlled by end-capping with phthalic anhydride and addition of 5 percent by weight p-phenylenediamine-phthalic anhydride bisamic acid dopant. Prepreg was drum-wound using a diglyme slurry comprised of the soluble polyamideacid of PISO2, the soluble bisamideacid of the dopant, and the insoluble imidized LARC-TPI powder. Melt flow studies with a rotary rheometer and parallel plate plastometer on neat resin and prepreg helped develop an optimum cure cycle. Composite mechanical properties at room and elevated temperatures, dry and moisture-saturated, were evaluated, including short beam shear strength and flexure, tensile, shear, and compression properties. Two 18 x 24-inch skin-stringer panels were fabricated, one of which was tested in compression to failure.

Johnston, Norman J.↗
NASA NTRS1980

Performance Properties of Graphite Reinforced Composites with Advanced Resin Matrices

This article looks at the effect of different resin matrices on thermal and mechanical properties of graphite composites, and relates the thermal and flammability properties to the anaerobic char yield of the resins. The processing parameters of graphite composites utilizing graphite fabric and epoxy or other advanced resins as matrices are presented. Thermoset resin matrices studied were: aminecured polyfunctional glycidyl aminetype epoxy (baseline), phenolicnovolac resin based on condensation of dihydroxymethyl-xylene and phenol cured with hexamine, two types of polydismaleimide resins, phenolic resin, and benzyl resin. The thermoplastic matrices studied were polyethersulfone and polyphenylenesulfone. Properties evaluated in the study included anaerobic char yield, limiting oxygen index, smoke evolution, moisture absorption, and mechanical properties at elevated temperatures including tensile, compressive, and short-beam shear strengths. Generally, it was determined that graphite composites with the highest char yield exhibited optimum fire-resistant properties.

Kourtides, Demetrius A.↗
NASA NTRS2001

Multifunctional Carbon Foams for Aerospace Applications

Carbon foams produced by the controlled thermal decomposition of inexpensive coal extracts exhibit a combination of structural and thermal properties that make them attractive for aerospace applications. Their thermal conductivity can be tailored between 0.5 and 100 W/mK through precursor selection/modification and heat treatment conditions; thus, they can serve in either thermal protection or heat transfer systems such as heat exchangers. Because their structure is essentially a 3D random network of graphite-like members, they also can be considered low-cost, easily fabricated replacements for multi-directional structural carbon fiber preforms. Strengths of over 4000 psi in compression are common. Their density can be designed between 0.1 and 0.8 g/cc, and they can be impregnated with a variety of matrices or used, unfilled, in sandwich structures. These foams also exhibit intriguing electrochemical properties that offer potential in high-efficiency fuel cell and battery applications, mandrels and tooling for composite manufacture, ablative performance, and fire resistance. This paper presents the results of research conducted under NASA SBIR Topic 99.04.01, General Aviation Technology, supported from Langley Research Center. The potential of foam design through precursor selection, cell size and density control, density grading, and heat treatment is demonstrated.

Rogers, D. K.↗
NASA NTRS2010

Polyimides Based on Asymmetric Dianhydrides (II) (a-BPDA vs a-BTDA) for Resin Transfer Molding (RTM)

A new series of low-melt viscosity imide resins (10-20 poise at 280 C) were formulated from asymmetric 2,3,3',4' -benzophenone dianhydride (a-BTDA) and 4-phenylethynylphthalic endcaps, along with 3,4' -oxydianiline, 3,3' -methylenedianiline and 3,3'- diaminobenzophenone, using a solvent-free melt process. a-BTDA RTM resins exhibited higher glass transition temperatures (Tg's = 330-400 C) compared to those prepared by asymmetric 2,3,3',4' -biphenyl dianhydride, (a-BPDA, Tg's = 320-370 C). These low-melt viscosity imide resins were fabricated into polyimide/T650-35 carbon fiber composites by a RTM process. Composites properties of a-BTDA resins, such as open-hole compression and short-beam shear strength, are compared to those of composites made from a-BPDA based resin at room temperature, 288 C and 315 C. These novel, high temperature RTM imide resins exhibit outstanding properties beyond the performance of conventional RTM resins, such as epoxy and BMI resins which have use-temperatures around 177 C and 232 C for aerospace applications.

Chuang, Kathy C.↗
DOE OSTI2018

MICRO-CELLULOSE FIBER REINFORCED BIOCOMPOSITES FOR ADDITIVE MANUFACTURING

Polymer additive manufacturing (AM) technology is rapidly growing and it is transitioning from being primarily a prototyping method to an advanced manufacturing technique. Melt extrusion/fused deposition modeling, a method in which molten thermoplastic-based feedstock material is deposited in a raster pattern layer by layer, is the most commonly used technique in polymer AM. The technique enables direct digital manufacturing of desired geometry with controlled anisotropic distribution of reinforcing phase. While thermoplastic composites are being used in many areas of industry including AM, due to increasing environmental and long-term sustainability concerns, there is an increasing interest in bio-based renewable alternatives. Nano-to-mm scale plant-based fibers are utilized to improve properties of thermoplastics and produce bio-composites. The effect of commercially available micro-scale cellulose fibers (MFC) on the mechanical and rheological behavior of polylactic acid to produce fully bio-based composites are being investigated and selected formulations will be 3D-printed to investigate the effect of printing process on MFC alignment. Significant increases in both tensile strength and elastic modulus of compression-molded MFC-PLA composites were observed at 40 % (by wt) fiber levels.

Tekinalp, Halil↗
DOE OSTI2017

Solidification/Stabilization of Liquid Oil Waste in Meta-kaolin-based geo-polymer - 17209

Cement-base solidification/stabilization (S/S) is a widely applied technique for the immobilization of inorganic hazardous constituents. However, S/S is considered less compatible with organic liquid wastes (OLW) because organic compounds may inhibit binder hydration. geo-polymers (alumino-silicate materials) are a worthwhile material for applications in which cements are inappropriate. In this study, we propose a direct immobilization process of organic liquid waste in a geo-polymer matrix based on the emulsification of OLW in an activating solution, followed by the addition of aluminosilicate source (meta-kaolin). At first, the harmlessness of the chemicals contained in the OLW on the geo-polymerization was examined through a screening, reveling that only acidic oils should be pre-treated before a direct immobilization. Waste form characterizations with a simulated OLW were measured, showing interesting mechanical and confinement properties. Waste forms containing 20% Vol. of OLW show a mechanical strength higher than 30 MPa in compression and less than 1 % of waste leached over a month in pure water. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1992

Correlation of deformation mechanisms with the tensile and compressive behavior of NiAl and NiAl(Zr) intermetallic alloys

To identify the mechanisms controlling strength and ductility in powder-extruded NiAl and NiAl + 0.05 at. pct Zr, tensile and compressive testing was performed from 300 to 1300 K for several grain sizes. Grain size refinement significantly increased yield stress in both alloys and, in some cases, slightly lowered the ductile-to-brittle transition temperature (DBTT), although no room-temperature tensile ductility was observed even in the finest grain size specimens. The small Zr addition increased the DBTT and changed the low-temperature fracture mode from intergranular in NiAl to a combination of intergranular and transgranular in the Zr-doped alloy. Scanning electron microscopy of compression specimens deformed at room temperature revealed the presence of grain-boundary cracks in both alloys. These cracks were due to the incompatibility of strain in the polycrystalline material, owing to the lack of five independent slip systems. The tendency to form grain-boundary cracks, in addition to the low fracture stress of these alloys, contributed to the lack of tensile ductility at low temperatures.

Bowman, R. R.↗
DOE OSTI2017

High-pressure polymorphism of two high-strength ceramics: Boron carbide (B4C) and silicon carbide (SiC)

We have determined the lattice-level structure of two high-strength, technologically important ceramic materials under shock wave compression. For decades, laboratory shock wave studies have provided crucial information on the dynamic response of many types of materials. However, previous studies were limited to continuum-level information only. By combining laser compression with pulsed X-ray diffraction we are able to obtain in situ structural information on these materials for the first time. Silicon carbide (SiC) and boron carbide (B4C) are two high-strength ceramics with many technical applications including debris shielding, armoring, and coating. We have carried out Xray diffraction measurements of the structure of SiC and B4C under shock compression to 185 and 300 GPa, respectively. Experiments were performed at the Matter in Extreme Conditions beamline of the Linac Coherent Light Source (LCLS). At LCLS, shock waves are driven into the sample using a high powered laser with approximately 10 nanosecond pulse length. The sample is probed with X-rays from the LCLS free electron laser and diffraction is recorded by x-ray detectors. By varying the delay between the laser and the x-ray probe, the sample can be studied at various times relative to the shock wave entering the sample. The diffraction data have been analyzed to determine the crystal structures, lattice parameters, density, and crystallographic texture as a function of pressure and loading time.

36 MATERIALS SCIENCE↗