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All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Particle Shape and Composition of NU-LHT-2M

Particle shapes of the lunar regolith simulant NU-LHT-2M were analyzed by scanning electron microscope of polished sections. These data provide shape, size, and composition information on a particle by particle basis. 5,193 particles were measured, divided into four sized fractions: less than 200 mesh, 200-100 mesh, 100-35 mesh, and greater than 35 mesh. 99.2% of all particles were monominerallic. Minor size versus composition effects were noted in minor and trace mineralogy. The two metrics used are aspect ratio and Heywood factor, plotted as normalized frequency distributions. Shape versus composition effects were noted for glass and possibly chlorite. To aid in analysis, the measured shape distributions are compared to data for ellipses and rectangles. Several other simple geometric shapes are also investigated as to how they plot in aspect ratio versus Heywood factor space. The bulk of the data previously reported, which were acquired in a plane of projection, are between the ellipse and rectangle lines. In contrast, these data, which were acquired in a plane of section, clearly show that a significant number of particles have concave hulls in this view. Appendices cover details of measurement error, use of geometric shapes for comparative analysis, and a logic for comparing data from plane of projection and plane of section measurements.

Rickman, D. L.↗
NASA NTRS2012

Mechanical and Combustion Performance of Multi-Walled Carbon Nanotubes as an Additive to Paraffin-Based Solid Fuels for Hybrid Rockets

Paraffin-based solid fuels for hybrid rocket motor applications are recognized as a fastburning alternative to other fuel binders such as HTPB, but efforts to further improve the burning rate and mechanical properties of paraffin are still necessary. One approach that is considered in this study is to use multi-walled carbon nanotubes (MWNT) as an additive to paraffin wax. Carbon nanotubes provide increased electrical and thermal conductivity to the solid-fuel grains to which they are added, which can improve the mass burning rate. Furthermore, the addition of ultra-fine aluminum particles to the paraffin/MWNT fuel grains can enhance regression rate of the solid fuel and the density impulse of the hybrid rocket. The multi-walled carbon nanotubes also present the possibility of greatly improving the mechanical properties (e.g., tensile strength) of the paraffin-based solid-fuel grains. For casting these solid-fuel grains, various percentages of MWNT and aluminum particles will be added to the paraffin wax. Previous work has been published about the dispersion and mixing of carbon nanotubes.1 Another manufacturing method has been used for mixing the MWNT with a phenolic resin for ablative applications, and the manufacturing and mixing processes are well-documented in the literature.2 The cost of MWNT is a small fraction of single-walled nanotubes. This is a scale-up advantage as future applications and projects will require low cost additives to maintain cost effectiveness. Testing of the solid-fuel grains will be conducted in several steps. Dog bone samples will be cast and prepared for tensile testing. The fuel samples will also be analyzed using thermogravimetric analysis and a high-resolution scanning electron microscope (SEM). The SEM will allow for examination of the solid fuel grain for uniformity and consistency. The paraffin-based fuel grains will also be tested using two hybrid rocket test motors located at the Pennsylvania State University s High Pressure Combustion Lab.

Larson, Daniel B.↗
NASA NTRS2012

Design and Characterization of Thin Stainless Steel Burst Disks for Increasing Two-Stage Light Gas Launcher Efficiency

Laser etched 300 series Stainless Steel Burst Disks (SSBD) ranging between 0.178 mm (0.007-in.) and 0.508mm (0.020-in.) thick were designed for use in a 17-caliber two-stage light gas launcher. First, a disk manufacturing method was selected using a combination of wire electrical discharge machining (EDM) to form the blank disks and laser etching to define the pedaling fracture pattern. Second, a replaceable insert was designed to go between the SSDB and the barrel. This insert reduced the stress concentration between the SSBD and the barrel, providing a place for the petals of the SSDB to open, and protecting the rifling on the inside of the barrel. Thereafter, a design of experiments was implemented to test and characterize the burst characteristics of SSBDs. Extensive hydrostatic burst testing of the SSBDs was performed to complete the design of experiments study with one-hundred and seven burst tests. The experiment simultaneously tested the effects of the following: two SSBD material states (full hard, annealed); five SSBD thicknesses 0.178, 0.254, 0.305, 0.381 mm (0.007, 0.010, 0.012, 0.015, 0.020-in.); two grain directions relative); number of times the laser etch pattern was repeated (varies between 5-200 times); two heat sink configurations (with and without heat sink); and, two barrel configurations (with and without insert). These tests resulted in the quantification of the relationship between SSBD thickness, laser etch parameters, and desired burst pressure. Of the factors investigated only thickness and number of laser etches were needed to develop a mathematical relationship predicting hydrostatic burst pressure of disks using the same barrel configuration. The fracture surfaces of two representative SSBD bursts were then investigated with a scanning electron microscope, one burst hydrostatically in a fixture and another dynamically in the launcher. The fracture analysis verified that both burst conditions resulted in a ductile overload failure indicated by transgranular microvoid coalescence, non-fragmenting rupture and mixed tensile and shear failure modes, regardless of the material states tested. More testing is underway to determine the relationship between SSBD burst pressure and projectile velocity.

Tylka, Jonathan M.↗
NASA NTRS2013

Wear and Reactivity Studies of Melt infiltrated Ceramic Matrix Composite

As interest grows in the use of ceramic matrix composites (CMCs) for critical gas turbine engine components, the effects of the CMCs interaction with the adjoining structure needs to be understood. A series of CMC/material couples were wear tested in a custom elevated temperature test rig and tested as diffusion couples, to identify interactions. Specifically, melt infiltrated silicon carbide/silicon carbide (MI SiC/SiC) CMC was tested in combination with a nickel-based super alloy, Waspaloy, a thermal barrier coating, Yttria Stabilized Zirconia (YSZ), and a monolithic ceramic, silicon nitride (Si3N4). To make the tests more representative of actual hardware, the surface of the CMC was kept in the as-received state (not machined) with the full surface features/roughness present. Test results include: scanning electron microscope characterization of the surfaces, micro-structural characterization, and microprobe analysis.

Jarmon, David C.↗
NASA NTRS2013

Fuzzy Reasoning to More Accurately Determine Void Areas on Optical Micrographs of Composite Structures

Accomplishing the best-performing composite matrix (resin) requires that not only the processing method but also the cure cycle generate low-void-content structures. If voids are present, the performance of the composite matrix will be significantly reduced. This is usually noticed by significant reductions in matrix-dominated properties, such as compression and shear strength. Voids in composite materials are areas that are absent of the composite components: matrix and fibers. The characteristics of the voids and their accurate estimation are critical to determine for high performance composite structures. One widely used method of performing void analysis on a composite structure sample is acquiring optical micrographs or Scanning Electron Microscope (SEM) images of lateral sides of the sample and retrieving the void areas within the micrographs/images using an image analysis technique. Segmentation for the retrieval and subsequent computation of void areas within the micrographs/images is challenging as the gray-scaled values of the void areas are close to the gray-scaled values of the matrix leading to the need of manually performing the segmentation based on the histogram of the micrographs/images to retrieve the void areas. The use of an algorithm developed by NASA and based on Fuzzy Reasoning (FR) proved to overcome the difficulty of suitably differentiate void and matrix image areas with similar gray-scaled values leading not only to a more accurate estimation of void areas on composite matrix micrographs but also to a faster void analysis process as the algorithm is fully autonomous.

Dominquez, Jesus A.↗
NASA NTRS2013

Silicon Micromachined Microlens Array for THz Antennas

5 5 silicon microlens array was developed using a silicon micromachining technique for a silicon-based THz antenna array. The feature of the silicon micromachining technique enables one to microfabricate an unlimited number of microlens arrays at one time with good uniformity on a silicon wafer. This technique will resolve one of the key issues in building a THz camera, which is to integrate antennas in a detector array. The conventional approach of building single-pixel receivers and stacking them to form a multi-pixel receiver is not suited at THz because a single-pixel receiver already has difficulty fitting into mass, volume, and power budgets, especially in space applications. In this proposed technique, one has controllability on both diameter and curvature of a silicon microlens. First of all, the diameter of microlens depends on how thick photoresist one could coat and pattern. So far, the diameter of a 6- mm photoresist microlens with 400 m in height has been successfully microfabricated. Based on current researchers experiences, a diameter larger than 1-cm photoresist microlens array would be feasible. In order to control the curvature of the microlens, the following process variables could be used: 1. Amount of photoresist: It determines the curvature of the photoresist microlens. Since the photoresist lens is transferred onto the silicon substrate, it will directly control the curvature of the silicon microlens. 2. Etching selectivity between photoresist and silicon: The photoresist microlens is formed by thermal reflow. In order to transfer the exact photoresist curvature onto silicon, there needs to be etching selectivity of 1:1 between silicon and photoresist. However, by varying the etching selectivity, one could control the curvature of the silicon microlens. The figure shows the microfabricated silicon microlens 5 x5 array. The diameter of the microlens located in the center is about 2.5 mm. The measured 3-D profile of the microlens surface has a smooth curvature. The measured height of the silicon microlens is about 280 microns. In this case, the original height of the photoresist was 210 microns. The change was due to the etching selectivity of 1.33 between photoresist and silicon. The measured surface roughness of the silicon microlens shows the peak-to-peak surface roughness of less than 0.5 microns, which is adequate in THz frequency. For example, the surface roughness should be less than 7 microns at 600 GHz range. The SEM (scanning electron microscope) image of the microlens confirms the smooth surface. The beam pattern at 550 GHz shows good directivity.

Lee, Choonsup↗
NASA NTRS2013

Micromechanical Characterization and Testing of Carbon Based Woven Thermal Protection Materials

Woven thermal protection system (TPS) materials are one of the enabling technologies for mechanically deployable hypersonic decelerator systems. These materials can be simultaneously used for thermal protection and as structural load bearing members during the entry, descent and landing operations. In order to ensure successful thermal and structural performance during the atmospheric entry, it is important to characterize the properties of these materials, once they have been subjected to entry like conditions. The present paper focuses on mechanical characteristics of pre-and post arc-jet tested woven TPS samples at different scales. It also presents the observations from scanning electron microscope and computed tomography images, and explains the changes in microstructure after being subjected to combined thermal-mechanical loading environments.

Agrawal, Parul↗
NASA NTRS2013

Engineering Evaluation of International Low Impact Docking System Latch Hooks

The international Low Impact Docking System (iLIDS) provides a structural arrangement that allows for visiting vehicles to dock with the International Space Station (ISS) (Fig 1). The iLIDS docking units are mechanically joined together by a series of active and passive latch hooks. In order to preserve docking capability at the existing Russian docking interfaces, the iLIDS latch hooks are required to conform to the existing Russian design. The latch hooks are classified as being fail-safe. Since the latch hooks are fail-safe, the hooks are not fracture critical and a fatigue based service life assessment will satisfy the structural integrity requirements. Constant amplitude fatigue testing to failure on four sets of active/passive iLIDS latch hooks was performed at load magnitudes of 10, 11, and 12 kips. Failure analysis of the hook fatigue failures identified multi-site fatigue initiation that was effectively centered about the hook mid-plane (consistent with the 3D model results). The fatigue crack initiation distribution implies that the fatigue damage accumulation effectively results in a very low aspect ratio surface crack (which can be simulated as thru-thickness crack). Fatigue damage progression resulted in numerous close proximity fatigue crack initiation sites. It was not possible to determine if fatigue crack coalescence occurs during cyclic loading or as result of the fast fracture response. The presence of multiple fatigue crack initiation sites on different planes will result in the formation of ratchet marks as the cracks coalesce. Once the stable fatigue crack becomes unstable and the fast fracture advances across the remaining ligament and the plane stress condition at a free-surface will result in failure along a 45 deg. shear plane (slant fracture) and the resulting inclined edge is called a shear lip. The hook thickness on the plane of fatigue crack initiation is 0.787". The distance between the shear lips on this plane was on the order of 0.48" and it was effectively centered about the mid-plane of the section. The numerous ratchet marks between the shear lips on the fracture initiation plane are indicative of multiple fatigue initiation sites within this region. The distribution of the fatigue damage about the centerline of the hook is consistent with the analytical results that demonstrate peak stress/strain response at the mid-plane that decreases in the direction of the hook outer surfaces. Scanning electron microscope images of the failed sections detected fatigue crack striations in close proximity to the free surface of the hook radius. These findings were documented at three locations on the fracture surface : 1) adjacent to the left shear lip, 2) adjacent to the right shear lip, and 3) near the centerline of the section. The features of the titanium fracture surface did not allow for a determination of a critical crack size via identification of the region where the fatigue crack propagation became unstable. The fracture based service life projections where benchmarked with strain-life analyses. The strainrange response in the hook radius was defined via the correlated finite element models and the modified method of universal slopes was incorporated to define the strain-life equation for the titanium alloy. The strain-life assessment confirmed that the fracture based projections were reasonable for the loading range of interest. Based upon the analysis and component level fatigue test data a preliminary service life capability for the iLIDS active and passive hooks of 2 lifetimes is projected (includes a scatter factor of 4).

Martinez, J.↗
NASA NTRS2013

Fabrication Method for LOBSTER-Eye Optics in <110> Silicon

Soft x-ray optics can use narrow slots to direct x-rays into a desirable pattern on a focal plane. While square-pack, square-pore, slumped optics exist for this purpose, they are costly. Silicon (Si) is being examined as a possible low-cost replacement. A fabrication method was developed for narrow slots in <110> Si demonstrating the feasibility of stacked slot optics to replace micropores. Current micropore optics exist that have 20-micron-square pores on 26-micron pitch in glass with a depth of 1 mm and an extent of several square centimeters. Among several proposals to emulate the square pore optics are stacked slot chips with etched vertical slots. When the slots in the stack are positioned orthogonally to each other, the component will approach the soft x-ray focusing observed in the micropore optics. A specific improvement Si provides is that it can have narrower sidewalls between slots to permit greater throughput of x-rays through the optics. In general, Si can have more variation in slot geometry (width, length). Further, the sidewalls can be coated with high-Z materials to enhance reflection and potentially reduce the surface roughness of the reflecting surface. Narrow, close-packed deep slots in <110> Si have been produced using potassium hydroxide (KOH) etching and a patterned silicon nitride (SiN) mask. The achieved slot geometries have sufficient wall smoothness, as observed through scanning electron microscope (SEM) imaging, to enable evaluation of these slot plates as an optical element for soft x-rays. Etches of different angles to the crystal plane of Si were evaluated to identify a specific range of etch angles that will enable low undercut slots in the Si <110> material. These slots with the narrow sidewalls are demonstrated to several hundred microns in depth, and a technical path to 500-micron deep slots in a precision geometry of narrow, closepacked slots is feasible. Although intrinsic stress in ultrathin wall Si is observed, slots with walls approaching 1.5 microns can be achieved (a significant improvement over the 6-micron walls in micro - pore optics). The major advantages of this technique are the potential for higher x-ray throughout (due to narrow slot walls) and lower cost over the existing slumped micropore glass plates. KOH etching of smooth sidewalls has been demonstrated for many applications, suggesting its feasibility for implementation in x-ray optics. Si cannot be slumped like the micropore optics, so the focusing will be achieved with millimeter-scale slot plates that populate a spherical dome. The possibility for large-scale production exists for Si parts that is more difficult to achieve in micropore parts.

Chervenak, James↗
NASA NTRS2013

Experimental Characterization and Simulation of Slip Transfer at Grain Boundaries and Microstructurally-Sensitive Crack Propagation

A systematic study of crack tip interaction with grain boundaries is critical for improvement of multiscale modeling of microstructurally-sensitive fatigue crack propagation and for the computationally-assisted design of more durable materials. In this study, single, bi- and large-grain multi-crystal specimens of an aluminum-copper alloy are fabricated, characterized using electron backscattered diffraction (EBSD), and deformed under tensile loading and nano-indentation. 2D image correlation (IC) in an environmental scanning electron microscope (ESEM) is used to measure displacements near crack tips, grain boundaries and within grain interiors. The role of grain boundaries on slip transfer is examined using nano-indentation in combination with high-resolution EBSD. The use of detailed IC and EBSD-based experiments are discussed as they relate to crystal-plasticity finite element (CPFE) model calibration and validation.

Gupta, Vipul↗
NASA NTRS2014

Magnetite as Possible Template for the Synthesis of Chiral Organics in Carbonaceous Chondrites

The main goal of the Japanese Aerospace Ex-ploration Agency (JAXA) Hayabusa-2 mission is to visit and return to Earth samples of a C-type asteroid (162173) 1999 JU3 in order to understand the origin and nature of organic materials in the Solar System. Life on Earth shows preference towards the set of organics with particular spatial arrangements, this 'selectivity' is a crucial criterion for life. With only rare exceptions, life 'determines' to use the left- (L-) form over the right- (D-) form of amino acids, resulting in a L-enantiomeric excess (ee). Recent studies have shown that L-ee is found within the alpha-methyl amino acids in meteorites [1, 2], which are amino acids with rare terrestrial occurrence, and thus point towards a plausible abiotic origin for ee. One of the proposed origins of chiral asymmetry of amino acids in meteorites is their formation with the presence of asymmetric catalysts [3]. The catalytic mineral grains acted as a surface at which nebular gases (CO, H2 and NH3) were allowed to condense and react through Fisher Tropsch type (FTT) syntheses to form the organics observed in meteorites [4]. Magnetite is shown to be an effective catalyst of the synthesis of amino acids that are commonly found in meteorites [5]. It has also taken the form as spiral magnetites (a.k.a. 'plaquettes'), which were found in various carbonaceous chondrites (CCs), including C2s Tagish Lake and Esseibi, CI Orgueil, and CR chondrites [e.g., 6, 7, 8]. In addition, L-ee for amino acids are common in the aqueously altered CCs, as opposed to the unaltered CCs [1]. It seems possible that the synthesis of amino acids with chiral preferences is correlated to the alteration process experienced by the asteroid parent body, and related to the configuration of spiral magnetite catalysts. Since C-type asteroids are considered to be enriched in organic matter, and the spectral data of 1999 JU3 indicates a certain de-gree of aqueous alteration [9], the Hayabusa-2 mission serves as a perfect chance to attest this argument. In order to understand the distribution of spiral magnetites among different meteorite classes, as well as to investigate their spiral configurations and correlation to molecular asymmetry, we observed polished thin sections of CCs using scanning electron microscope (SEM) imaging. Individual magnetite grains were picked, embedded in epoxy, thin-sectioned using an ultra-microtome, and studied with electron backscatter diffraction (EBSD) in order to reconstruct the crystal orientation along the stack of magnetite disks.

Chan, Q. H. S.↗
NASA NTRS2015

Scaffold of Asymmetric Organic Compounds - Magnetite Plaquettes

Life on Earth shows preference towards the set of organics with particular spatial configurations, this 'selectivity' is a crucial criterion for life. With only rare exceptions, life prefers the left- (L-) form over the right- (D-) form of amino acids, resulting in an L-enantiomeric excess (L-ee). Recent studies have shown Lee for alpha-methyl amino acids in some chondrites. Since these amino acids have limited terrestrial occurrence, the origin of their stereoselectivity is nonbiological, and it seems appropriate to conclude that chiral asymmetry, the molecular characteristic that is common to all terrestrial life form, has an abiotic origin. A possible abiotic mechanism that can produce chiral asymmetry in meteoritic amino acids is their formation with the presence of asymmetric catalysts, as mineral crystallization can produce spatially asymmetric structures. Magnetite is shown to be an effective catalyst for the formation of amino acids that are commonly found in chondrites. Magnetite 'plaquettes' (or 'platelets'), first described by Jedwab, show an interesting morphology of barrel-shaped stacks of magnetite disks with an apparent dislocation-induced spiral growth that seem to be connected at the center. A recent study by Singh et al. has shown that magnetites can self-assemble into helical superstructures. Such molecular asymmetry could be inherited by adsorbed organic molecules. In order to understand the distribution of 'spiral' magnetites in different meteorite classes, as well as to investigate their apparent spiral configurations and possible correlation to molecular asymmetry, we observed polished sections of carbonaceous chondrites (CC) using scanning electron microscope (SEM) imaging. The sections were also studied by electron backscattered diffraction (EBSD) in order to reconstruct the crystal orientation along the stack of magnetite disks.

Chan, Q. H. S.↗
NASA NTRS2015

Creep Behavior and Durability of Cracked CMC

To understand failure mechanisms and durability of cracked Ceramic matrix composites (CMCs), Melt Infiltration (MI) SiCSiC composites with Sylramic-iBN fibers and full Chemical vapour infiltration SiCSiC composites with Sylramic-ion bombarded BN (iBN) and Hi-Nicalon -S fibers were pre-cracked between 150 to 200 megapascal and then creep and Sustained Peak Low Cycle Fatigue (SPLCF) tested at 13150 C at stress levels from 35 to 103 megapascal for up to 200 hours under furnace and burner rig conditions. In addition creep testing was also conducted on pre-cracked full Chemical vapour infiltration SiCSiC composites at 14500 C between 35 and 103 megapascal for up to 200 hours under furnace conditions. If the specimens survived the 200 hour durability tests, then they were tensile tested at room temperature to determine their residual tensile properties. The failed specimens were examined by Scanning electron microscope (SEM) to determine the failure modes and mechanisms. The influence of crack healing matrix, fiber types, crack density, testing modes and interface oxidation on durability of cracked Ceramic matrix composites (CMCs) will be discussed.

Creep↗
NASA NTRS2011

Carbon-Based Nano-Electro-Mechanical-Systems

We provide an overview of our work where carbon-based nanostructures have been applied to two-dimensional (2D) planar and three-dimensional (3D) vertically-oriented nano-electro-mechanical (NEM) switches. In the first configuration, laterally oriented single-walled nanotubes (SWNTs) synthesized using thermal chemical vapor deposition (CVD) were implemented for forming bridge-type 2D NEMS switches, where switching voltages were on the order of a few volts. In the second configuration, vertically oriented carbon nanofibers (CNFs) synthesized using plasma-enhanced (PE) CVD have been explored for their potential application in 3D NEMS. We have performed nanomechanical measurements on such vertically oriented tubes using nanoindentation to determine the mechanical properties of the CNFs. Electrostatic switching was demonstrated in the CNFs synthesized on refractory metallic nitride substrates, where a nanoprobe was used as the actuating electrode inside a scanning-electron-microscope. The switching voltages were determined to be in the tens of volts range and van der Waals interactions at these length scales appeared significant, suggesting such structures are promising for nonvolatile memory applications. A finite element model was also developed to determine a theoretical pull-in voltage which was compared to experimental results.

Complementary-Metal-Oxide-Semiconductor (CMOS)↗
NASA NTRS2015

Optimization of a Wcl6 CVD System to Coat UO2 Powder with Tungsten

In order to achieve deep space exploration via Nuclear Thermal Propulsion (NTP), Marshall Space Flight Center (MSFC) is developing W-UO2 CERMET fuel elements, with focus on fabrication, testing, and process optimization. A risk of fuel loss is present due to the CTE mismatch between tungsten and UO2 in the W-60vol%UO2 fuel element, leading to high thermal stresses. This fuel loss can be reduced by coating the spherical UO2 particles with tungsten via H2/WCl6 reduction in a fluidized bed CVD system. Since the latest incarnation of the inverted reactor was completed, various minor modifications to the system design were completed, including an inverted frit sublimer. In order to optimize the parameters to achieve the desired tungsten coating thickness, a number of trials using surrogate HfO2 powder were performed. The furnace temperature was varied between 930 C and 1000degC, and the sublimer temperature was varied between 140 C and 200 C. Each trial lasted 73-82 minutes, with one lasting 205 minutes. A total of 13 trials were performed over the course of three months, two of which were re-coatings of previous trials. The powder samples were weighed before and after coating to roughly determine mass gain, and Scanning Electron Microscope (SEM) data was also obtained. Initial mass results indicated that the rate of layer deposition was lower than desired in all of the trials. SEM confirmed that while a uniform coating was obtained, the average coating thickness was 9.1% of the goal. The two re-coating trials did increase the thickness of the tungsten layer, but only to an average 14.3% of the goal. Therefore, the number of CVD runs required to fully coat one batch of material with the current configuration is not feasible for high production rates. Therefore, the system will be modified to operate with a negative pressure environment. This will allow for better gas mixing and more efficient heating of the substrate material, yielding greater tungsten coating per trial.

Belancik, Grace A.↗
NASA NTRS2015

A Fully Nonmetallic Gas Turbine Engine Enabled by Additive Manufacturing, Part II: Additive Manufacturing and Characterization of Polymer Composites

This publication is the second part of the three part report of the project entitled "A Fully Nonmetallic Gas Turbine Engine Enabled by Additive Manufacturing" funded by NASA Aeronautics Research Institute (NARI). The objective of this project was to conduct additive manufacturing to produce aircraft engine components by Fused Deposition Modeling (FDM), using commercially available polyetherimides-Ultem 9085 and experimental Ultem 1000 mixed with 10% chopped carbon fiber. A property comparison between FDM-printed and injection molded coupons for Ultem 9085, Ultem 1000 resin and the fiber-filled composite Ultem 1000 was carried out. Furthermore, an acoustic liner was printed from Ultem 9085 simulating conventional honeycomb structured liners and tested in a wind tunnel. Composite compressor inlet guide vanes were also printed using fiber-filled Ultem 1000 filaments and tested in a cascade rig. The fiber-filled Ultem 1000 filaments and composite vanes were characterized by scanning electron microscope (SEM) and acid digestion to determine the porosity of FDM-printed articles which ranged from 25 to 31%. Coupons of Ultem 9085, experimental Ultem 1000 composites and XH6050 resin were tested at room temperature and 400F to evaluate their corresponding mechanical properties. A preliminary modeling was also initiated to predict the mechanical properties of FDM-printed Ultem 9085 coupons in relation to varied raster angles and void contents, using the GRC-developed MAC/GMC program.

Polymer↗
NASA NTRS2015

Crystallography of Magnetite Plaquettes and their Significance as Asymmetric Catalysts for the Synthesis of Chiral Organics in Carbonaceous Chondrites

We have previously observed the magnetite plaquettes in carbonaceous chondrites using scanning electron microscope (SEM) imaging, examined the crystal orientation of the polished surfaces of magnetite plaquettes in CI Orgueil using electron backscattered diffraction (EBSD) analysis, and concluded that these magnetite plaquettes are likely naturally asymmetric materials. In this study, we expanded our EBSD observation to other magnetite plaquettes in Orgueil, and further examined the internal structure of these remarkable crystals with the use of X-ray computed microtomography.

Chan, Q. H. S.↗
NASA NTRS2015

Electron Beam Irradiated Intercalated CNT Yarns For Aerospace Applications

Multi-walled CNT yarns have been experimentally and commercially created to yield lightweight, high conductivity fibers with good tensile properties for application as electrical wiring and multifunctional tendons. Multifunctional tendons are needed as the cable structures in tensegrity robots for use in planetary exploration. These lightweight robust tendons can provide mechanical strength for movement of the robot in addition to power distribution and data transmission. In aerospace vehicles, such as Orion, electrical wiring and harnessing mass can approach half of the avionics mass. Use of CNT yarns as electrical power and data cables could reduce mass of the wiring by thirty to seventy percent. These fibers have been intercalated with mixed halogens to increase their specific electrical conductivity to that near copper. This conductivity, combined with the superior strength and fatigue resistance makes it an attractive alternative to copper for wiring and multifunctional tendon applications. Electron beam irradiation has been shown to increase mechanical strength in pristine CNT fibers through increased cross-linking. Both pristine and intercalated CNT yarns have been irradiated using a 5-megavolt electron beam for various durations and the conductivities and tensile properties will be discussed. Structural information obtained using a field emission scanning electron microscope, energy dispersive X-ray spectroscopy (EDS), and Raman spectroscopy will correlate microstructural details with bulk properties.

electrical wiring↗