Carbon nanotube structure
Macroscopic Nanotube Fabrication Process Control
A combination of magnetic and optical methods are applied to characterize the residual catalyst content, nanotube alignment and load transfer between individual nanotubes during the fabrication process. The techniques used in this method, which have been proven at the micro level, are applied so that scanning and mapping occurs at the macro level. These methods have been successfully used for nondestructive evaluation of large-format carbon nanotube-based structures, primarily yarns as well as sheets from several inches square to as large as 4ft. by 8ft.
crack testing
Method of Non-Destructive Evaluation of Composites
Guided wavefield techniques require excitation of guided waves in a specimen via contact or noncontact methods (such as attached piezoelectric transducers or laser generation). The resulting wavefield is recorded via noncontact methods such as laser Doppler vibrometry or air-coupled ultrasound. If the specimen contains damage, the waves will interact with that damage, resulting in an altered wavefield (compared to the pristine case). When guided wave modes enter into a delaminated region of a composite the energy is split above/below delaminations and travels through the material between delaminations. Some of the energy propagates beyond the delamination and re-emerges as the original guided wave modes. However, a portion of the wave energy is trapped as standing waves between delaminations. The trapped waves slowly leak from the delaminated region, but energy remains trapped for some time after the incident waves have propagated beyond the damage region. Simulation results show changes in the trapped energy at the composite surface when additional delaminations exist through the composite thickness. The results are a preliminary proof-of-concept for utilizing trapped energy measurements to identify the presence of hidden delaminations when only single-sided access is available to a component/vehicle. Currently, no other single-sided field-applicable NDT techniques exist for identifying hidden delamination damage.
power generation and storage
Thin film device for harvesting energy from wind
Compliant electrode and composite materials for piezoelectric wind and mechanical energy conversions
The NASA researchers integrated two innovations into this unique piezoelectric device. First, they combined polyvinylidene flouride (PVDF) with a metal oxide to improve conductance. Second, they designed a new carbon-electrode to improve durability (compliance) and reduce susceptibility to fatigue while retaining flexibility. Additionally, to integrate the carbon nanotube components, they use a polymer-to-polymer design that eliminates the need for adhesion layers. A prototype device generated 1 W power (at 15 mph wind) with a single layer of PVDF [4 inch by 12 inch and 50 um (micrometer) thick] sandwiched between two thin electrode films. A rectifier converts the AC signal into a DC signal and stores the charge in a capacitor. This electric power can be used for low power consuming devices, such an inaccessible sensors.
materials and coatings
Thermal Protection Systems
High Efficiency Tantalum-based Ceramic Composite (HETC) Structures
The various embodiments of this technology include insulating composites capable of surviving high heating rates and large thermal gradients in the aeroconvective heating environment that entry vehicles are exposed to characteristically. The tantalum-based ceramics contain tantalum disilicide, borosilicate glass and, optionally, molybdenum disilicide. The components are milled, along with a processing aid to facilitate sintering, then applied to a surface of a porous substrate, such as a fibrous or open-pored silica, carbon, aluminosilicate, silicon carbide or silicon oxycarbide substrate, as well as other substrates of silicon/carbon compositions. Following application, the coating is then sintered on the substrate. The composite structure is substantially impervious to hot gas penetration and capable of surviving high heat fluxes.
materials and coatings
hBN Dispersions
Exfoliated Hexagonal Boron Nitride
The invented method involves mechanical breakdown of large hBN particles followed by chemical functionalization to achieve exfoliation of the hBN sheets. The exfoliated h- nanosheets are of mono- or few atomic layers thick, and dispersible (or suspendable, soluble) in common organic solvents and/or water, depending upon the nature of the functionalities. The functionalities can be subsequently removed by thermal treatment, with the hBN nanostructures remaining intact and exfoliated.
materials and coatings
PICA being tested in Arcjet Facility
Creating Low Density Flexible Ablative Materials
The low density flexible ablator can be deployed by mechanical mechanisms or by inflation and is comparable in performance to its rigid counterparts of the same density and composition. Recent testing in excess of 400W/cm2 demonstrated that the TPS char has good structural integrity and retains similar flexibility to the virgin material, there by eliminating potential failure due to fluttering and internal stress buildup as a result of pyrolysis and shrinkage of the system. These flexible ablators can operate at heating regimes where state of the art flexible TPS (non-ablative) will not survive. Flexible ablators enable and improve many missions including (1) hypersonic inflatable aerodynamic decelerators or other deployed concepts delivering large payload to Mars and (2) replacing rigid TPS materials there by reducing design complexity associated with rigid TPS materials resulting in reduced TPS costs.
materials and coatings
Reentry Vehicles
New Resin Systems for Thermal Protection Materials
This method produces a low density ablator similar to Phenolic Impregnated Carbon Ablator (PICA) using a cyanate ester and phthalonitrile resin system, rather than the heritage phenolic resin. Cyanate ester resin systems can be cured in a carbon matrix and generate high surface area structure within the carbon fibers. This helps to reduce the thermal conductivity of the material which is one of the key requirements of thermal protection system (TPS) materials. The material has densities ranging from 0.2 to .35 grams per cubic centimeter. NASA has successfully processed the cyanate ester and phthalonitrile resins with a morphology similar to that of the phenolic phase in PICA, but with more advanced properties such as high char stability, high char yield, and high thermal stability. This new generation of TPS materials has the same microstructure as heritage PICA, but improved characteristics of PICA such as increased char yield, increased char stability, increased thermal stability and increased glass transition temperature.
Miniaturized High-Speed Modulated X-Ray Source (MXS)
Miniaturized High-Speed Modulated X-Ray Source (MXS)
The MXS produces electrons by shining UV light from an LED onto a photocathode material such as magnesium. The electrons are then accelerated across several kV and into a chosen target material; deceleration produces X-rays characteristic of the target. The MXS uses an electron multiplier for high X-ray production efficiency. The MXS is more compact, rugged, and power-efficient than standard X-ray sources. It can be manufactured using commercially available components and 3D printed housing, resulting in a low cost to manufacture. Unlike traditional X-ray sources, the MXS does not require a filament or vacuum and cooling systems. Most importantly, enabling rapid and arbitrary modulation allows using X-rays in the time domain, a new dimension to X-ray applications.
materials and coatings
Orion re-entry in to earth's atmosphere
Multifunctional Ablative Thermal Protection System
The initial compression pad design for Orion was complex and limited to Earth orbit return missions, such as the 2014 Exploration Flight Test-1 (EFT-1). The 2-D carbon phenolic material used for EFT-1 has relatively low interlaminar strength and requires a metallic sheer insert to handle structural loads. There are few options for materials that can meet the load demands of lunar return missions due to performance or part-size limitations. The 3DMAT material is a woven fiber preform fully densified with cyanate ester resin. It produces a large composite with significant structural capabilities and the ability to withstand high aerothermal heating environments on its outer surface while keeping the inner surface cool and protected from the aerothermal heating. The robustness of the 3DMAT material is derived from high fiber volume (>56%), 3-D-orthoganol architecture, and low porosity (0.5%). Orion has adopted 3DMAT for all future MPCV missions, including EM-1 schedule to launch in 2018.
materials and coatings
High Pressure Soft Lithography for Micro-topographical Patterning of Molded Polymers and Composites
This technology provides an efficient means to fabricate micro-topographical surface patterns or features. A polydimethylsiloxane (PDMS), or similar elastomer, would incorporate a master pattern, which acts as a mold through which liquid resin material flows and hardens to create a rigid, inverse replica of the mold specific to its intended surface applications. One application of the technology is to create super-hydrophobic surfaces that protect against contamination and fouling. Another application is to improve adhesion between two parts in an adhesively bonded joints, which is of particular interest for composite parts where sanding could expose reinforcing fibers to degenerative environmental effects. Another use of the technology is to create surfaces that reduce drag in aerodynamic and hydrodynamic applications.
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