Method of Bonding Dissimilar Materials

Elastic adhesive overcomes the problems associated with large differences in thermal expansion coefficients.

An image of the Materials International Space Station Experiment-5 (MISSE-5) samples prior to launch shows a golden thermal blanket with flexible material samples attached.

NASA’s Goddard Space Flight Center has developed a new method for bonding dissimilar materials using an elastic adhesive to permit the bond to withstand variations in temperature and pressure. Specifically, NASA uses this method to provide a >98% specular finish on composite materials that is proven capable of withstanding ultraviolet solar radiation exposure in a vacuum and thermal cycling from –115 °C to +65 °C, as well as meeting outgassing requirement limits of 1%.

Posted in: Briefs, Materials, Joining, Adhesives and sealants, Composite materials, Elastomers, Durability

Nanoencapsulated Aerogels Produced by Monomer Vapor Deposition and Polymerization

This technology provides a method for making strong and lightweight aerogels with insulating properties.

The nano-encapsulated aerogel technology has the strength and insulation properties for many applications.

The Johnson Space Center researched methods to coat aerogel insulation in order to make it better able to withstand vibration, mechanical compression and flexure, and other environmental damage. This NASA-developed nanoencapsulated aerogel technology is a method for increasing the strength of the aerogel through a coating process while maintaining its insulating properties. With this ruggedizing process, the coating of the aerogel reduces mechanical damage, enabling its practical use in products that might not be suitable with the more fragile aerogel. The basic coating can also shield it from adsorbing humidity or other gases, which could otherwise bind to the substance and change its properties. Functionalized coatings could be developed to adsorb certain gases if that is desired. Aerogel’s low density and extremely low thermal conductivity make it useful as a lightweight, volume-efficient insulation material. Encapsulating the aerogel expands its ability to be incorporated into products that are exposed to vibration and compression during manufacture, shipping, or use. It can also improve its flexibility, opening up a range of new product uses.

Posted in: Briefs, Materials, Coatings, colorants, and finishes, Insulation, Nanomaterials, Durability

Insulative Carbon Fiber Systems for Aerospace Applications

New insulative carbon-fiber composite systems have been developed for use in structural and thermal applications for the aerospace vehicle interface. The sandwich-type composite structure, including carbon fiber and aerogel blanket materials, is based on the previously disclosed family of hybrid laminate composites. Offering unique and tailorable combinations of structural and thermal properties, these insulative carbon fiber systems can be used in vehicle shroud and thermal protection system applications at the aerodynamic interface plane, panels between stages, or fairings for spacecraft equipment space of space launch vehicles. The novel, lightweight, fiber composite laminate system with reduced heat transfer also has increased impact resistance at low temperatures.

Posted in: Briefs, Materials, Aircraft structures, Composite materials, Fibers, Insulation

In-Situ Formation of Reinforcement Phases in Ultra-High- Temperature Ceramic Composites

This technology could be used in re-entry vehicles, reusable launch vehicles, hypersonic vehicle leading edges, and commercial spacecraft.

Future-generation materials for use on space transportation vehicles require substantial improvements in material properties leading to increased reliability and safety, as well as intelligent design to allow for current materials to meet future needs. Ultra-high-temperature ceramics (UHTC), composed primarily of metal diborides, are candidate materials for sharp leading edges on hypersonic re-entry vehicles. NASA has demonstrated that it is possible to form high-aspect-ratio reinforcement phases in-situ during the processing step for both ceramic composites and UHTCs. Initial characterization of these systems has demonstrated that crack deflection along the matrix-reinforcement interface is observed yielding a system of improved toughness over the baseline system, leading to improved mechanical performance. The reinforced composites should therefore reduce the risk of catastrophic failure over current UHTC systems.

Posted in: Briefs, Coatings & Adhesives, Materials, Ceramics, Composite materials, Materials properties, Reliability, Spacecraft

Multi-Phase Ceramic System

Bearing surfaces are typically either metal-on-metal (MOM), ceramic-on-ceramic (COC), or metal-on-polyethylene (MOP). MOM and MOP couplings have the drawback that metallic or polyethylene particles can sometimes separate from the couplings, which can cause significant problems, particularly in a hip or joint replacement. COC couplings are less likely to lose particles due to wear, which makes them more biocompatible, but they are more susceptible to fracture. COC couplings also have a tendency to squeak as they move. Innovators at NASA’s Glenn Research Center have developed a technique using rare earth elements to fabricate a dual-phase ceramic composite that combines a wear-resistant phase and a solid-state lubricant phase. The result is a coupling material that, compared to currently used materials, exhibits a tenfold reduction in the friction coefficient, a sixfold reduction in wear, and a significant reduction in debris caused by wear. Glenn’s groundbreaking rare-earth aluminate composite has considerable potential, not only in biomedical applications, but also in commercial and industrial sectors.

Posted in: Briefs, Ceramics, Materials, Prostheses and implants, Fabrication, Ceramics, Materials identification, Materials properties, Wear

Minimally Machined HoneySiC Panels and T300 HoneySiC

The materials are intended for low areal density and near-zero CTE optomechanical structures.

The primary purpose of this work is to develop and demonstrate technologies to manufacture ultra-low-cost precision optical systems for very large x-ray, UV/optical, or infrared telescopes.

Posted in: Briefs, Coatings & Adhesives, Materials, Design processes, Integrated circuits, Optics, Fabrication, Semiconductors

Flexible Volumetric Structure

These composite elastic skins can be tailored for specific applications.

NASA’s Langley Research Center has developed composite elastic skins for covering shape-changing (morphable) structures. These skins are intended especially for use on advanced aircraft that change shapes in order to assume different aerodynamic properties. Examples of aircraft shape changes include growth or shrinkage of bumps, conformal changes in wing planforms, cambers, twists, and bending of integrated leading and trailing-edge flaps. Prior to this invention, there was no way of providing smooth aerodynamic surfaces capable of large deflections while maintaining smoothness and sufficient rigidity.

Posted in: Briefs, Coatings & Adhesives, Materials, Aircraft structures, Composite materials, Elastomers, Aerodynamics

Aeroplastic Composites

Aeroplastic refers to a family of polymeric composites with properties that provide a significant reduction in heat transfer. These composites reduce the thermal conductivity of the base polymer resin between 20%-50% without changing its mechanical properties or modifying the original techniques for processing those polymers. The composites can be made into fibers, molded, or otherwise processed into usable articles. Aeroplastic composites are superior alternatives to prior composite materials with respect to both their thermal conductivity and physical properties.

Posted in: Briefs, Coatings & Adhesives, Materials, Heat transfer, Composite materials, Heat resistant materials, Materials properties, Polymers

Thermomechanical Methodology for Stabilizing Shape Memory Alloy (SMA) Response

SMA training can be completed in a matter of minutes, rather than days or even weeks.

Shape memory alloys (SMAs), sometimes known as “smart metals,” provide a lightweight, solid-state alternative to conventional actuators and switches, such as hydraulic, pneumatic, or motor-based systems. To function properly, SMAs must be “trained” to return to a previous form when heated, and innovators at NASA’s Glenn Research Center have developed a remarkable new method of completing this training at a fraction of the time and cost of conventional training techniques. Glenn’s technique uses mechanical cycling, rather than more complicated and time-consuming thermal cycling, to train SMAs before implementation. In addition, this new approach to training allows SMAs to be applied to complex geometric components, so that they may be used in a broader number of applications.

Posted in: Briefs, Materials, Sensors and actuators, Switches, Metals, Smart materials

Flexible Ablator for Thermal Protection

Simple and versatile manufacturing approach to produce heat shields.

NASA has developed a class of low-density, flexible ablators that can be fabricated into heat-shields capable of being packaged, stowed, and deployed in space. The key characteristics of this new ablative thermal protection system (TPS) are its flexibility, conformability, and tailor-ability. Flexibility allows the material to be stowed in the shroud of a launch vehicle and deployed in space, without compromising functionality. Conformability allows the material to be attached to a curved surface without precise and expensive machining. Tailor-ability allows the density and composition to be optimized for the requirements. This flexible TPS can be used to cover and thermally protect a large, blunt shape that provides aerodynamic drag during hyper-velocity atmospheric flight. It can be used with minimal modification for large aeroshells whose deployment relies mainly on mechanical means and through inflation. Such devices are called Hypersonic Inflatable Aerodynamic Decelerators (HIADs). Large blunt body aeroshells may be used to deliver large payloads (40 metric tons) to the surface of Mars.

Posted in: Briefs, Materials, Thermal management, Packaging, Resins

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