Where else but the annual SAMPE gathering can you find not only the latest developments in composites and other advanced materials, but also new ways to join, design, and fabricate them? Here's a sampling of technologies from this year's exhibition, which took place in Long Beach, CA:
Materials for the heavens and Earth
NASA highlighted new materials technologies it has made available for license. For thin-film applications, NASA's Glenn Research Center has synthesized UV-curable polyimides with glass transition temperatures as high as 300F. NASA Langley Research Center has come out with an environmentally friendly polyimide for use as a matrix resin. Marshall Space Flight Center has developed a process to make layered composite tanks and pipes to store "aggressive" fluids such as cryogenic fuels or caustic fluids. These storage vessels consist of four layers: a corrosion-resistant liner fabricated by thermal spray or electrodeposition; a structural layer of woven graphite and epoxy; an insulating foam layer; and an impact fighting layer of Kevlar or impregnated glass outer coating. The resulting tanks weigh in at 25% lighter than a comparable aluminum structure and 20% lighter than those made from aluminum or fiberglass.
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... BP Amoco Polymers Inc. has developed EnerGraph DBX, a series of ultra-high crystallinity graphites for use in lithium battery anodes. Suitable for both liquid or polymer-thin-film battery systems, anodes using EnerGraph reportedly generate 30% less heat and exhibit 20% higher activation energy than anodes using non-fibrous graphite.
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... BP Amoco has also expanded its line-up of pitch fibers for thermal-management, frictional, and structural applications. And the company has added to its line of ultra-high thermal conductivity fibers with a Thornel K-800X 2K graphite fiber that offers a fiber thermal conductivity of 800 W/mK and a composite thermal conductivity of 400 w/mK.
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Joining together
Ciba Specialty Chemicals Performance Polymers introduced an optically clear, UV stable urethane adhesive for bonding fiberglass, glass, metal, and a variety of thermoplastics—including PC, ABS, and acrylic. Urelane 6100-A/B exhibits polycarbonate-to-polycarbonate lap shear strength of 950 psi at room temperature and an elongation of 400%.
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... As a low-cost alternative to traditional brazed or welded joints, NASA's Marshall Space Flight Center has cooked up new thermal elements that hold static joints together. Placed in the joint under a preload and heated, these gasket-like elements carry a coating that melts to form a connection in the joint. Depending on the application, the thermal elements can be heated with either an electrical current or external heat source. The coatings can be adhesives, thermoplastics, or braze alloys. Potential applications for the new joints include automotive engine cooling system housings, piping, sealed electrical housings, and housings for marine engines and transmissions.
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... SP Systems introduced new epoxy adhesives in a range of viscosities, including adhesives with fire retardant and quickset capabilities. Also among the new products is SpaBond 735, which combines a shear strength of up to 43 MPa on steel, cleavage strength in excess of 12kN, and a glass-transition temperature above 110C—all in a low-viscosity formulation.
Speedy turnarounds for composite parts
A new soft-tooling technique for close-tolerance composite parts has been developed by Ciba Specialty Chemicals and The Boeing Co.'s Rotorcraft Program . Called LCTC—short for "Low Cost Tooling for Composites"—the technique produces tools from Ciba's Ren seamless epoxy patties for a reported 70% cost savings versus traditional tooling methods. To go right from CAD data to the model surface, LCTC requires three steps: applying the patties to an undersize core, oven curing, and CNC machining. The resulting tools can make short-run parts in an autoclave or prepreg prototypes. The epoxy used for the tools, Ren TDT 177-150 offers machining rates of more than 200 ipm, temperature performance up to 380F, CTE values comparable to aluminum, and thermal transfer better than metal molds.
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