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Durable Joining Technology for Uniformly-Curved Composite Sandwich Structures

An insert improves distribution of load through the joint, increasing safety. Langley Research Center, Hampton, Virginia NASA’s next-generation launch vehicles will be enabled by high-performance composite materials and innovative manufacturing methods. As such, NASA uses adhesively bonded joints where possible instead of mechanically fastened (bolted) joints to design and manufacture structures. The adhesive joints typically are lighter and distribute loads more efficiently across an interface, while mechanically fastened joints are prone to stress concentrations around the bolts.

Posted in: Manufacturing & Prototyping, Briefs

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Ohmic Contact to N- and P-Type Silicon Carbide

Ohmic contact can be formed in one process step. John H. Glenn Research Center, Cleveland, Ohio Electrical ohmic contacts can be simultaneously formed on silicon carbide (SiC) semiconductors having donor and acceptor impurities (n- and p-type doping, respectively). This implies that such contacts can be formed on SiC layers in one process step during the fabrication of the semiconductor device. This also means that the multiple process steps for fabricating contacts onto n- and p-type surfaces, which is characteristic of the prior art, will be greatly reduced, thereby reducing time and cost, and increasing yield (more process steps and complexity increases chances for lower yields). Another significance of this invention is that this scheme can serve as a non-discriminatory, universal ohmic contact to both n- and p-type SiC, without compromising the reliability of the specific contact resistivity when operated at temperatures in excess of 600 °C.

Posted in: Manufacturing & Prototyping, Briefs

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Flap Edge Noise Reduction Fins

This innovation has applications in aircraft leading edge slats and rotor tips for propulsion components on both aircraft and rotorcraft, as well as on wind turbines. Langley Research Center, Hampton, Virginia Aircraft noise is a significant problem with both economic and public health implications, especially for communities near airports. As a result, increasingly stringent constraints are being placed on aircraft carriers worldwide to reduce this noise. The current disclosure focuses on airframe noise generated at or near the surface of the flap-side edge.

Posted in: Manufacturing & Prototyping, Briefs

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Toughened Uni-piece Fibrous Reinforced Oxidation-Resistant Composite (TUFROC)

Ames Research Center, Moffett Field, California TUFROC has an exposed surface edge design and an appropriate materials combination for a space vehicle that will survive the mechanical stresses induced in the initial ascent, and will subsequently survive the extreme heating and mechanically stressful environment of re-entry. It provides a thermal protection tile attachment system, suitable for application to a space vehicle leading edge, and for other uses in extreme heating environments [up to 3,600 °F (1,982 °C), and possibly higher, for short time intervals].

Posted in: Materials, Briefs

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High-Efficiency Tantalum-Based Ceramic Composite Structures

Ames Research Center, Moffett Field, California High-efficiency tantalum-based ceramic (HETC) composite structures are suitable for use in thermal protection systems. These composite structures have high-efficiency surfaces (low catalytic efficiency and high-emittance), thereby reducing heat flux to a spacecraft during planetary reentry. These low catalytic efficiency and high-emittance ceramic materials were developed in order to increase the capability of a Toughened Uni-Piece Fibrous Insulation (TUFI)-like thermal protection system, with its high-impact resistance, to temperatures above 3,000 °F (≈1,650 °C). These ceramics have been applied to various aerodynamic configurations, such as wedge, wing-leading segment, and conventional tile shapes used on high-speed atmospheric entry vehicles. In addition, this family of tantalum-based ceramics exhibits low catalytic efficiency to atom recombination during exposure to highenergy dissociated hypersonic flow.

Posted in: Materials, Briefs

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Use of Solvent-Free Conditions/Dry Mixing for Functionalizing Carbon Nanotubes

Lyndon B. Johnson Space Center, Houston, Texas Two methods have been developed for functionalizing carbon nanotubes in solvent-free conditions. In one method, purified single-walled carbon nanotubes (SWNTs) and a diazonium salt are added to a metal vial, which is loaded with a stainless steel ball bearing. The metal vial is clamped into a mill mixer, and is mixed for one hour. The unreacted diazonium salt is then dissolved in a volume of acetonitrile that efficiently solubilizes the salt to remove the unreacted functionalization reagent. The functionalized nanotubes are then collected by filtration.

Posted in: Materials, Briefs

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Synthesis of Novel Copoly(alkyl ether imide)s With Unique Surface Properties

These materials have potential applications in marine biofouling, biomedical devices, microfluidics, corrosion and stain resistance, ice and water adhesion, and drag reduction. Langley Research Center, Hampton, Virginia Copoly(alkyl ether imide)s were synthesized for the purposes of tailoring surface chemistry. Alkyl ether oligomers with amine end groups were synthesized from the hydroxyl-terminated species, and subsequently reacted with aromatic dianhydrides and diamines to make the copolymers. Films were solution-cast from the copolymers and exhibited reduced surface energy and increased surface fluorine content at extremely low loadings relative to the imide matrix. These copolymers are currently being evaluated for mitigation of particle adhesion and fouling from exposure to various particle and biological contaminants. Additionally, the surface migration of the oxetane segments can be used as a shuttle to bring other designed chemical constituents to the surface.

Posted in: Materials, Briefs

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