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Thermally Activated Crack Healing Mechanism for Metallic Materials

A thin metallic film of a low-melting-temperature healing agent is used. Langley Research Center, Hampton, Virginia A thermally activated healing mechanism is proposed and experimentally validated to mitigate crack propagation damage in metallic materials. The protected structure is coated with a thin metallic film of a low-melting-temperature healing agent. To heal or mitigate crack damage, the structure is heated to the melting temperature of the healing agent, allowing it to flow into the crack opening. Once in the crack mouth, the healing agent has two benefits: (1) by adhering to the crack surfaces, the healing agent bridges the crack, reducing the amount of load at the crack tip; and (2) any voluminous substance in the crack mouth causes crack closure (premature crack-face contact during cyclic loading) that also reduces the crack-tip loading.

Posted in: Materials, Coatings & Adhesives, Briefs, TSP

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Subsurface Imaging of Nanocomposites

Applications include sensors and actuators, aerospace structures, and tissue infusion in medical areas. Langley Research Center, Hampton, Virginia A nondestructive method that is based on modified atomic force ultrasonic microscopy (AFUM) methods has been developed for characterizing nanomaterials. The technology allows imaging and quantifying of material properties at the surface and subsurface levels. The technology reveals the orientation of nanotubes within a composite structure and offers the ability to determine subsurface characteristics without destroying the nanomaterial structure. The method is widely applicable for basic nanomaterials characterization, including distribution and orientation of particles in a nanocomposite, localized elastic constants and changes in elastic constants, adhesive surface properties, sound velocity, and material damping coefficient.

Posted in: Materials, Coatings & Adhesives, Briefs

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Self-Healing Glass Sealants for Solid Oxide Fuel Cells and Electrolyzer Cells

Operational requirements are 600 to 1,000 °C for thousands of hours. John H. Glenn Research Center, Cleveland, Ohio A solid oxide fuel cell (SOFC) is an electrochemical device that converts chemical energy into electrical power. A solid oxide electrolyzer cell (SOEC) operates in a reverse mode of SOFC, and produces O2 and H2 gases. SOFCs are being developed for a broad range of applications including portable electronic devices, automobiles, power generation, and aeronautics. The salient features of SOFCs are all-solid construction and high-temperature electrochemical reaction-based operation, resulting in clean and efficient power generation from a variety of fuels. SOFCs of two different designs, tubular and planar, are currently under development. Planar SOFCs offer several advantages such as simple manufacturing and relatively short current path, resulting in higher power density and efficiency. However, planar SOFCs and SOECs require hermetic seals. Various glass and glass-ceramics based on borates, phosphates, and silicates are being examined for SOFC seals. Silicate glasses are expected to perform superior to the borate and phosphate glasses as sealing materials.

Posted in: Materials, Coatings & Adhesives, Briefs, TSP

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Micromachined Thermopile Arrays with Novel Thermo-electric Materials

Goddard Space Flight Center, Greenbelt, Maryland Future missions to outer planets will have stringent limits on payload mass. Thermal imaging instruments to map planetary surfaces will be part of those payloads, and, consequently, will have to be compact and low mass. For thermal instruments, another key requirement will be state-of-the-art, highly sensitive detectors. Thermopiles are prime candidates for high-resolution thermal mapping in the far-infrared (17- to 250-μm wavelength) spectral range. Thermopile detector arrays can be made to be very lightweight and compact. Furthermore, they require very few ancillary components (e.g., readout electronics, optics, amplifiers), which can add to instrument volume and mass. The implementation of thermopiles on these missions is likely because they (1) generate an output voltage that is proportional to the incoming radiation within the spectral range being mapped; (2) do not require an electrical bias or an optical chopper; (3) have negligible 1/f noise; (4) are radiation hard; and (5) have a reported specific detectivity of 1 × 109 cm·Hz1/2/W at room temperature.

Posted in: Materials, Coatings & Adhesives, Briefs, TSP

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Low-Cost, High-Performance MMOD Shielding

Relatively inexpensive fiberglass fabric is proposed in place of costlier materials. Lyndon B. Johnson Space Center, Houston, Texas High-performance micro-meteoroid and orbital debris (MMOD) shielding can be constructed from low-cost, off-the-shelf materials. The advantage in using this innovation is in achieving considerable reduction in both cost and mass of the shielding necessary to protect spacecraft from hypervelocity MMOD particle impacts. For instance, in a typical application of this technology for a visiting vehicle used to transport cargo to the International Space Station (ISS) over ten years, an estimated $330,000 is saved (at the time of this reporting) in using a less-expensive MMOD fabric over conventional materials, and an estimated 2,000-kg mass is reduced from the MMOD shielding using the materials and techniques described here compared to conventional means.

Posted in: Materials, Coatings & Adhesives, Briefs, TSP

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Creating Better Thermal-Imaging Lens From Waste Sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team has found. The team successfully took thermal images of a person through a piece of the new plastic. By contrast, taking a picture taken through the plastic often used for ordinary lenses does not show a person’s body heat.

Posted in: Imaging, Photonics, Optics, Optical Components, Materials, Plastics, News

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3D-Printing Aerial Robot Mimics Tiny Bird

Scientists from Imperial College London have developed a 3D-printing Micro Aerial Vehicle (MAV) that mimics the way that swiftlets build their nests.The MAV is a quad-copter, with four blades that enable it to fly and hover. The vehicle, made from off-the-shelf components, carries in its underbelly two chemicals that create polyurethane foam when mixed, and a printing module to deliver the foam. The foam can then be used to build simple structures or repair components.The texture of the polymer exuded from the 3D printer can also be used to create ’grippers,‘ which stick onto and transport objects to different locations. The MAV could therefore pick up and remove bombs, or dispose of hazardous materials without exposing humans to danger. The next step for the team is to enable the vehicle to fly autonomously in any environment. The scientists plan to incorporate high-speed cameras and sensors on board the MAV, which will act like a satellite navigation system for tracking and controlling of the flight trajectory.SourceAlso: Learn more about NASA's Robonaut 2.

Posted in: Imaging, Manufacturing & Prototyping, Rapid Prototyping & Tooling, Materials, Plastics, Sensors, Aerospace, Aviation, Machinery & Automation, Robotics, Defense, News

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