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DOE OSTI2022

Artificial intelligence based analysis of nanoindentation load–displacement data using a genetic algorithm

In this work, we developed an automated tool, Nanoindentation Neo package for the analysis of nanoindentation load–displacement curves using a Genetic Algorithm (GA) applied to the Oliver-Pharr method (Oliver et al.,1992). For some materials, such as polycrystalline isotropic graphites, Least Squares Fitting (LSF) of the unload curve can produce unrealistic fit parameters. These graphites exhibit sharply peaked unloading curves not easily fit using the LSF, which tends to overestimate the indenter tip geometry parameter. To tackle this problem, we extended our general materials characterization tool Neo for EXAFS analysis (Terry et al., 2021) to fit nanoindentation data. Nanoindentation Neo automatically processes and analyzes nanoindentation data with minimal user input while producing meaningful fit parameters. GA, a robust metaheuristic method, begins with a population of temporary solutions using model parameters called chromosomes; from these we evaluate a fitness value for each solution, and select the best solutions to mix with random solutions producing the next generation. A mutation operator then modifies existing solutions by random perturbations, and the optimal solution is selected. We tested the GA method using Silica and Al reference standards. We fit samples of graphite and a high entropy alloy (HEA) consisting of BCC and FCC phases.

42 ENGINEERING↗

NASA NTRS2013

Statistical Analyses of Raw Material Data for MTM45-1/CF7442A-36% RW: CMH Cure Cycle

This report describes statistical characterization of physical properties of the composite material system MTM45-1/CF7442A, which has been tested and is currently being considered for use on spacecraft structures. This composite system is made of 6K plain weave graphite fibers in a highly toughened resin system. This report summarizes the distribution types and statistical details of the tests and the conditions for the experimental data generated. These distributions will be used in multivariate regression analyses to help determine material and design allowables for similar material systems and to establish a procedure for other material systems. Additionally, these distributions will be used in future probabilistic analyses of spacecraft structures. The specific properties that are characterized are the ultimate strength, modulus, and Poisson􀂶s ratio by using a commercially available statistical package. Results are displayed using graphical and semigraphical methods and are included in the accompanying appendixes.

Coroneos, Rula↗

DOE OSTI2023

Stabilizing the Interphase in Cobalt–Free, Ultrahigh–Nickel Cathodes for Lithium–Ion Batteries

High-nickel layered oxide cathodes, such as LiNi 1-x-y Mn x Co y O 2 (NMC) and LiNi 1-x-y Co x Al y O 2 (NCA), are at the forefront for implementation in high-energy-density lithium-ion batteries. The presence of cobalt in both cathode chemistries, however, largely deters their application due to fiscal and humanitarian issues affiliated with cobalt sourcing. Increasing the Ni content drives down the Co content, but introduces additional structural and electrochemical problems attributed to high-Ni cathodes. Herein a dually modified cobalt-free ultrahigh-nickel cathode 0.02B-LiNi 0.99 Mg 0.01 O 2 (NBM) is presented with 1 mol% Mg and 2 mol% B that exhibits a high initial 1C discharge capacity of 210 mA h g –1 with a 20% capacity retention improvement over 500 cycles when benchmarked against LiNiO 2 (LNO) in pouch full cell configurations with graphite anode. Postmortem analyses reveal the enhanced performance stems from reduced active lithium inventory loss and localized surface reactivity in the NBM cathode. Here, the stabilized cathode-electrolyte interphase subsequently reduces transition-metal dissolution and ensuing chemical crossover to the graphite anode, which prevents further catalyzed parasitic reactions that harmfully passivate the anode surface. Altogether, this study aims to highlight the importance of electrode characterization and analysis from an interphasial viewpoint and to push the ongoing research to stabilize cobalt-free ultrahigh-Ni cathodes for industrial feasibility.

25 ENERGY STORAGE↗

DOE OSTI2024

Production of Carbon Nanomaterials and Sorbents from Domestic U.S. Coal (Final Report)

The main goal of this project was to produce high-value carbon nanomaterials and carbon sorbents from domestic coal resources in a cost-effective manner. Four types of domestic coal samples were processed through a combination of deashing, devolatilization, oxidation, reduction, and activation treatments to produce graphene oxide (GO), reduced graphene oxide (RGO), and activated carbon (AC). The precursors and developed materials were extensively characterized by various methods to investigate the impact of the coal feedstock type on the yield and quality of each product. A commercial graphite-based GO sample was included in the experimental work as the baseline material for comparison with the coal-based materials developed in this work. The performed work also included a technoeconomic analysis and cost estimation for a plant processing 20 tons/day coal, a market evaluation for the graphene materials, and a technology gap analysis. A simple process by concentrated nitric acid oxidation is used to oxidize coal precursors for the production of GO. Fine oxidized coal particles that were separated from larger oxidized coal particles had significantly higher oxygen contents and were identified as coal-based GO samples. Coarse oxidized coal particles were used as precursors for production of AC. Based on the Raman spectroscopy results, coal-based GO samples exhibited G and D bands similar to those of graphite-based GO samples. X-ray photoelectron spectroscopy revealed that coal-based GO samples had surface oxygen contents of ~26-35% that were higher than the oxygen contents of graphite-based GO samples. Larger particles of oxidized coal samples were activated under different conditions to produce high surface area functionalized AC. Prepared materials had surface areas exceeding 1,500 m 2 /g and pore volumes more than 1 cm 3 /g with different pore size distributions. Reduced graphene oxide samples were prepared by thermal reduction of both coal-based and graphite-based GO samples at 170-2800 ºC. Coal-based and graphite-based RGO samples exhibited similar carbon contents, Raman spectra, and XRD profiles. Heat treatment above 1500 ºC shifted RGO to synthetic graphite. Among anthracite, bituminous, subbituminous, and lignite coals tested, anthracite was the best precursor to produce carbon nanomaterials exhibiting properties similar to those of graphite-based materials. Anthracite-based carbon nanomaterials also had the highest production yields. Technoeconomic analysis estimated the production cost of GO and RGO for anthracite-based samples at about 2,600 and 4,200 $/ton, respectively, which is about two orders of magnitude lower than the current estimated price of graphite-based materials. Several gaps to further develop the proposed technology were identified and discussed that include process and equipment optimization, process integration, need for additional bench- and pilot-scale experiments, and other items to reduce the scale up risk. Market analysis reports suggested a compound annual growth rate of 40% for graphene and related materials. Short-term applications include composites, inks, and coatings. However, energy storage applications appear to be the dominant potential long-term applications. Different applications of coal-based GO and RGO need to be explored and clear metrics and standards for each application need to be developed.

01 COAL, LIGNITE, AND PEAT↗

NASA NTRS1985

Space radiation effects on an elastomer-toughened epoxy-graphite composite

An elastomer-toughened epoxy-graphite composite system (CE339/T300) was evaluated for its potential durability in the space radiation environment. The physical and chemical response of this system was characterized following exposure to radiation doses equivalent to 20 to 30 years in geosynchronous orbit using 1 MeV electrons. The results show that electrons generate extensive crosslinking and embrittlement of the matrix. This embrittlement results in chemical and mechanical property changes that would limit the service life of this epoxy system in some space structure applications.

Sykes, G. F.↗

NASA NTRS2004

Nanotube Activities at NASA-Johnson Space Center

Nanotube activities at NASA-Johnson Space Center include production, purification, characterization as well as applications of single wall carbon nanotubes (SWCNTs). A parametric study of the pulsed laser ablation process is recently completed to monitor the effect of production parameters including temperature, buffer gas, flow rate, pressure, and laser fluence. Enhancement of production is achieved by rastering the graphite target and by increasing the target surface temperature with a cw laser. In-situ diagnostics during production included time resolved passive emission and laser induced fluorescence from the plume. The improvement of the purity by a variety of steps in the purification process is monitored by characterization techniques including SEM, TEM, Raman, UV-VIS-NIR and TGA. A recently established NASA-JSC protocol for SWCNT characterization is undergoing revision with feedback from nanotube community. Efforts at JSC over the past five years in composites have centered on structural polymer/nanotube systems. Recent activities broadened this focus to multifunctional materials, supercapacitors, fuel cells, regenerable CO2 absorbers, electromagnetic shielding, radiation dosimetry and thermal management systems of interest for human space flight. Preliminary tests indicate improvement of performance in most of these applications because of the large Surface area as well as high electrical and thermal conductivity exhibited by SWCNTs. Comparison with existing technologies and possible future improvements in the SWCNT materials sill be presented.

Arepalli, Sivaram↗

NASA NTRS1993

Hypervelocity impact survivability experiments for carbonaceous impactors

We performed a series of hypervelocity impact experiments using carbon-bearing impactors (diamond, graphite, fullerenes, phthalic acid crystals, and Murchison meteorite) into Al plate at velocities between 4.2 and 6.1 km/s. These tests were made to do the following: (1) determine the survivability of carbon forms and organize molecules in low hypervelocity impact; (2) characterize carbonaceous impactor residues; and (3) determine whether or not fullerenes could form from carbonaceous impactors, under our experimental conditions, or survive as impactors. An analytical protocol of field emission SEM imagery, SEM-EDX, laser Raman spectroscopy, single and 2-stage laser mass spectrometry, and laser induced fluorescence (LIF) found the following: (1) diamonds did not survive impact at 4.8 km/s, but were transformed into various forms of disordered graphite; (2) intact, well-ordered graphite impactors did survive impact at 5.9 km/sec, but were only found in the crater bottom centers; the degree of impact-induced disorder in the graphite increases outward (walls, rims, ejecta); (3) phthalic acid crystals were destroyed on impact (at 4.2 km/s, although a large proportion of phthalic acid molecules did survive impact); (4) fullerenes did not form as products of carbonaceous impactors (5.9 - 6.1 km/s, fullerene impactor molecules mostly survived impact at 5.9 km/s; and (5) two Murchison meteorite samples (launched at 4.8 and 5.9 km/s) show preservation of some higher mass polycyclic aromatic hydrocarbons (PAHs) compared with the non-impacted sample. Each impactor type shows unique impactor residue morphologies produced at a given impact velocity. An expanded methodology is presented to announce relatively new analytical techniques together with innovative modifications to other methods that can be used to characterize small impact residues in LDEF craters, in addition to other acquired extraterrestrial samples.

Bunch, T. E.↗

DOE OSTI2023

Advancing neutron diffraction for accurate structural measurement of light elements at megabar pressures

Over the last 60 years, the diamond anvil cell (DAC) has emerged as the tool of choice in high pressure science because materials can be studied at megabar pressures using X-ray and spectroscopic probes. In contrast, the pressure range for neutron diffraction has been limited due to low neutron flux even at the strongest sources and the resulting large sample sizes. Here, we introduce a neutron DAC that enables break-out of the previously limited pressure range. Key elements are ball-bearing guides for improved mechanical stability, gem-quality synthetic diamonds with novel anvil support and improved in-seat collimation. We demonstrate a pressure record of 1.15 Mbar and crystallographic analysis at 1 Mbar on the example of nickel. Additionally, insights into the phase behavior of graphite to 0.5 Mbar are described. These technical and analytical developments will further allow structural studies on low-Z materials that are difficult to characterize by X-rays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2020

Beneficial Effect of Li 5 FeO 4 Lithium Source for Li-Ion Batteries with a Layered NMC Cathode and Si Anode

The energy density of lithium-ion batteries can be increased by replacing the traditional graphite anode with a high capacity silicon anode. However, volume changes and interfacial instabilities cause a large irreversible capacity and a continual loss of lithium during cycling, which lead to rapid capacity loss. In this work, we add Li 5 FeO 4 (LFO) to a LiNi 0.5 Mn 0.3 Co 0.2 O 2 (NMC) cathode as a pre-lithiation additive, which increases the lithium inventory and extends the cycle life of Si-graphite/NMC full cells, and decreases the NMC particle degradation. LFO delivers a large 764 mAh g –1 LFO capacity below 4.7 V vs Li/Li + . By tuning the LFO content in Si-graphite/LFO-NMC full cells, we show higher capacity, improved retention, lower impedance, and superior rate performance compared to full cells without LFO. Post-test characterizations demonstrate that LFO inclusion in the cathode matrix leads to less NMC secondary particle segregation/cracking and a thinner surface reduced layer on the NMC particles. The beneficial effects of LFO endure after the lithium reserve has been exhausted, highlighting a lasting synergy between the lithium source and electrode active materials. This study introduces a new approach to simultaneously increase lithium inventory and reduce cathode degradation, and makes critical advances toward enabling Si anodes for lithium-ion batteries.

25 ENERGY STORAGE↗

NASA NTRS1972

Composite material characterization for large space structures.

A program phase to characterize advanced composite materials for a large reflector support truss on the ATS F & G spacecraft is described. The selection of a Hercules Incorporated, 2002M graphite fiber reinforced epoxy material was based on criteria of spacecraft system requirements and the potential of this material to meet these requirements. The objective of this phase was to develop materials data required for development, design, fabrication, test, and flight of a graphite-fiber, reinforced-plastic spacecraft structure. Testing within a temperature range from -300 F to +200 F covered the generation of data for physical, mechanical, thermophysical, and space environmental properties for the selected material. Additional testing covered adhesive bonded joint materials within the temperature ranges of the spacecraft environment. Descriptions of the spacecraft, reflector support truss, design, requirements, materials, tests, and developed data are presented.

Macneill, C. E.↗

NASA NTRS2017

Fully Coupled Aero-Thermochemical-Elastic Simulations of an Eroding Graphite Nozzle

A multiphysics simulation capability has been developed that incorporates mutual interactions between aerodynamics, structural response from aero/thermal loading, ablation/pyrolysis, heating, and surface-to-surface radiation to perform high-fidelity, fully coupled aerothermoelastic ablation simulations, which to date had been unattainable. The multiphysics framework couples CHAR (a 3-D implicit charring ablator solver), Loci/CHEM (a computational fluid dynamics solver for high-speed chemically reacting flows), and Abaqus (a nonlinear structural dynamics solver) to create a fully coupled aerothermoelastic charring ablative solver. The solvers are tightly coupled in a fully integrated fashion to resolve the effects of the ablation pyrolysis and charring process and chemistry products upon the flow field, the changes in surface geometry due to recession upon the flow field, and thermal-structural analysis of the body from the induced aerodynamic heating from the flow field. The multiphysics framework was successfully demonstrated on a solid rocket motor graphite nozzle erosion application. Comparisons were made with available experimental data that measured the throat erosion during the motor firing. The erosion data is well characterized, as the test rig was equipped with a windowed nozzle section for real-time X-ray radiography diagnostics of the instantaneous throat variations for deducing the instantaneous erosion rates. The nozzle initially undergoes a nozzle contraction due to thermal expansion before ablation effects are able to widen the throat. A series of parameters studies were conducted using the coupled simulation capability to determine the sensitivity of the nozzle erosion to different parameters. The parameter studies included the shape of the nozzle throat (flat versus rounded), the material properties, the effect of the choice of turbulence model, and the inclusion or exclusion of the mechanical thermal expansion. Overall, the predicted results match the experiment very well, and the predictions were able to bound the data within acceptable limits.

Blades, E. L.↗

NASA NTRSDate not supplied

Coordinated Microstructural and Isotopic Characterization of Diamond Inclusions within the Kenna Ureilite

Introduction: The origin of diamonds in ureilitic meteorites, a major family of ultramafic achondrites, has long been debated, with various formation mechanisms inferred, including: 1) shock conversion of preexisting graphite due to a hypervelocity impact on the ureilite parent body [e.g., 1]; 2) vapor deposition during condensation of the solar nebula [e.g., 2]; or 3) static transformation in the mantle of a large planetesimal (>1000 km in diameter) [e.g., 3]. The Kenna ureilite is a 10.9 kg stone that was found in Kansas in 1972 and is dominantly composed of olivine and pigeonite (68% and 22% modal abundance, respectively), together with minor metal and carbon-rich regions. Within the carbon-rich domains researchers have identified microdiamonds up to ~10 µm in size [4]. Methods: Due to the proximity of the extremely hard microdiamonds with soft graphite and moderately hard silicates, achieving an appropriately flat surface for electron backscatter diffraction (EBSD) analysis has proven challenging. We have, therefore, employed a Hitachi ArBlade 5000 broad beam Ar ion milling system to prepare a sample with an adequately uniform surface flatness across the various minerals. The ion milling dramatically im-proved indexing of the EBSD patterns and facilitated high-resolution microstructural analysis of the carbon-rich domains. After microstructural EBSD analyses using an Oxford Symmetry detector we collected coordinated hy-perspectral cathodoluminescence (CL) analyses using a Gatan Monarc system mounted on a JEOL 7900F field emission (FE) scanning electron microscope at NASA Johnson Space Center. A focused ion beam (FIB) foil was extracted from a region of interest and analyzed using a JEOL 2500 FE scanning transmission electron microscope (STEM). In situ carbon and nitrogen isotopic analyses were collected from diamond-bearing domains using a Cameca NanoSIMS 50L at NASA JSC. Results: The carbon rich regions occur as tabular domains between polygonal olivine and pigeonite, and are composed of aggregates of micrometer-scale diamond with intermediate graphite, oxides and metal grains. Within the microdiamonds, {111} twins are abundant, many of which form ragged lamellae consistent with mechanical twinning. The microdiamond assemblages appear to pseudomorph tabular graphite habits, which together with the abundant deformation twins, support a shock transformation mechanism for microdiamond formation within the Kenna meteorite. Further supporting this observation, the diamond laths show close alignment of <111> and <110> between domains, consistent with a solid-state transformation from graphite along <0001> and <1-210>, respec-tively [5]. A FIB foil was extracted from a region with mechanical twins, and high resolution STEM analyses reveal cross-cutting veins of graphite and oriented kamacite crystals together with additional sets of {111} nano-twins formed in at least three orientations. Isotopic analyses of C and N reveal sector zoning patterns [cf. 3] that are unre-lated to the diamond substructure identified by EBSD yet consistent with hyperspectral CL images. Conclusions: These data provide new constraints on microdiamond formation within ureilites. The microdia-monds exhibit orientation variants defined by aligned <111> and <110> axes consistent with inherited crystallo-graphic orientations from transformation of a single hexagonal graphite parent crystal [5]. Crosscutting the micro-diamonds are veins of graphite and kamacite, together with additional {111} nanotwins. Taken together these data suggest that microdiamonds from ureilites formed from a solid state, diffusionless transformation from graphite, likely associated with a major shock event, which was subject to subsequent reversion either during decompression or a later deformation event. The N and C isotopic sector zoning is unrelated to diamond microstructures and likely reflects inheritance from the parent graphite crystal.

Ureilite↗

DOE OSTI2021

Effect of Carbon Doping on CO 2 –Reduction Activity of Single Cobalt Sites in Graphitic Carbon Nitride

Single atom catalysts have demonstrated interesting activity in a variety of applications. In this study, we prepared single C o2+ sites on graphitic carbon nitride (C 3 N 4 ), which was doped with carbon for enhanced activity in visible-light CO 2 reduction. The synthesized materials were characterized with a variety of techniques, including microscopy, X-ray powder diffraction, UV-vis spectroscopy, infrared spectroscopy, photoluminescence spectroscopy, and X-ray absorption spectroscopy. Here, doping C 3 N 4 with carbon was found to have profound effect on the photocatalytic activity of the single Co 2+ sites. At relatively low levels, carbon doping enhanced the photoresponse of C 3 N 4 in the visible region and improved charge separation upon photoactivation, thereby enhancing the photocatalytic activity. Furthermore, high levels of carbon doping were found to be detrimental to the photocatalytic activity of the single Co 2+ sites by altering the structure of C 3 N 4 and generating defect sites responsible for charge recombination.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Valorizing the carbon byproduct of methane pyrolysis in batteries

While low-cost natural gas remains abundant, the energy content of this fuel can be utilized without greenhouse gas emissions through the production of molecular hydrogen and solid carbon via methane pyrolysis. In the absence of a carbon tax, methane pyrolysis is not economically competitive with current hydrogen production methods unless the carbon byproducts can be valorized. In this work, we assess the viability of the carbon byproduct produced from methane pyrolysis in molten salts as high-value-added anode or conductive additive for secondary Li-ion and Na-ion batteries. Raman characterization and electrochemical differential capacity analysis demonstrate that the use of molten salt mixtures with catalytically-active FeCl 3 - or MnCl 2 result in more graphitic carbon co-products. These graphitic carbons exhibit the best electrochemical performance (up to 272 mAh/g of reversible capacity) when used as Li-ion anodes. For all carbon samples studied here, disordered carbon domains and retained salt species trapped and/or intercalated into the carbon structure were identified by X-ray photoelectron and multinuclear solid-state nuclear magnetic resonance spectroscopy. The latter lead to reduced electrochemical activity and reversibility, and poorer rate performance compared to commercial carbon anodes. The electronic conductivity of the pyrolyzed carbons is found to be highly dependent on their purity, with the purest carbon exhibiting an electronic conductivity nearly on par with that of commercial carbon additives. These findings suggest that more effective removal of the salt catalyst could enable applications of these carbons in secondary batteries, providing a financial incentive for the large-scale implementation of methane pyrolysis for “low-carbon” hydrogen production.

08 HYDROGEN↗

DOE OSTI2023

Synthesis and Thermal Oxidation Resistance of Boron-Rich Boron–Carbide Material

A boron-rich boron–carbide material (B4+δC) was synthesized by spark plasma sintering of a ball-milled mixture of high-purity boron powder and graphitic carbon at a pressure of 7 MPa and a temperature of 1930 °C. This high-pressure, high-temperature synthesized material was recovered and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Vickers hardness measurements, and thermal oxidation studies. The X-ray diffraction studies revealed a single-phase rhombohedral structure (space group R-3m) with lattice parameters in hexagonal representation as a = 5.609 ± 0.007 Å and c = 12.082 ± 0.02 Å. The experimental lattice parameters result in a value of δ = 0.55, or the composition of the synthesized compound as B4.55C. The high-resolution scans of boron binding energy reveal the existence of a B-C bond at 188.5 eV. Raman spectroscopy reveals the existence of a 386 cm−1 vibrational mode representative of C-B-B linear chain formation due to excess boron in the lattice. The measured Vickers microhardness at a load of 200 gf shows a high hardness value of 33.8 ± 2.3 GPa. Thermal gravimetric studies on B4.55C were conducted at a temperature of 1300 °C in a compressed dry air environment, and its behavior is compared to other high-temperature ceramic materials such as high-entropy transition metal boride. The high neutron absorption cross section, high melting point, high mechanical strength, and thermal oxidation resistance make this material ideal for applications in extreme environments.

36 MATERIALS SCIENCE↗

NASA NTRS1993

Aeroelastic airfoil smart spar

Aircraft wings and rotor-blades are subject to undesirable bending and twisting excursions that arise from unsteady aerodynamic forces during high speed flight, abrupt maneuvers, or hard landings. These bending excursions can range in amplitude from wing-tip flutter to failure. A continuous-filament construction 'smart' laminated composite box-beam spar is described which corrects itself when subject to undesirable bending excursions or flutter. The load-bearing spar is constructed so that any tendency for the wing or rotor-blade to bend from its normal position is met by opposite twisting of the spar to restore the wing to its normal position. Experimental and theoretical characterization of these spars was made to evaluate the torsion-flexure coupling associated with symmetric lay-ups. The materials used were uniweave AS-4 graphite and a matrix comprised of Shell 8132 resin and U-40 hardener. Experimental tests were conducted on five spars to determine spar twist and bend as a function of load for 0, 17, 30, 45 and 60 deg fiber angle lay-ups. Symmetric fiber lay-ups do exhibit torsion-flexure couplings. Predictions of the twist and bend versus load were made for different fiber orientations in laminated spars using a spline function structural analysis. The analytical results were compared with experimental results for validation. Excellent correlation between experimental and analytical values was found.

Greenhalgh, Skott↗

NASA NTRS1993

Mechanical characterization of 2D, 2D stitched, and 3D braided/RTM materials

Braided composite materials have potential for application in aircraft structures. Fuselage frames, floor beams, wing spars, and stiffeners are examples where braided composites could find application if cost effective processing and damage tolerance requirements are met. Another important consideration for braided composites relates to their mechanical properties and how they compare to the properties of composites produced by other textile composite processes being proposed for these applications. Unfortunately, mechanical property data for braided composites do not appear extensively in the literature. Data are presented in this paper on the mechanical characterization of 2D triaxial braid, 2D triaxial braid plus stitching, and 3D (through-the-thickness) braid composite materials. The braided preforms all had the same graphite tow size and the same nominal braid architectures, (+/- 30 deg/0 deg), and were resin transfer molded (RTM) using the same mold for each of two different resin systems. Static data are presented for notched and unnotched tension, notched and unnotched compression, and compression after impact strengths at room temperature. In addition, some static results, after environmental conditioning, are included. Baseline tension and compression fatigue results are also presented, but only for the 3D braided composite material with one of the resin systems.

Deaton, Jerry W.↗

NASA NTRS1979

Quality control developments for graphite/PMR15 polyimide composites materials

The problem of lot-to-lot and within-lot variability of graphite/PMR-15 prepreg was investigated. The PMR-15 chemical characterization data were evaluated along with the processing conditions controlling the manufacture of PMR-15 resin and monomers. Manufacturing procedures were selected to yield a consistently reproducible graphite prepreg that could be processed into acceptable structural elements.

Sheppard, C. H.↗