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JUN 2017

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NEWS CompositesWorld.com 33 (PMC) cutters, or put them in a PMC layup room," Hynes says. explaining, "You will have contamination issues." With this in mind, the company built a 3,252m 2 building in 2014 dedicated to CMC component manufacture. e facility includes an impressive array of CMC resources, including CNC cutters (Gerber Technology, Tolland, CT, US) with blades designed for cutting abrasive ceramic materials; laser projection systems (Virtek Vision, Waterloo, ON, Canada); a 5-axis CNC milling machine (Fooke GmbH, Borken, Germany); autoclaves (ASC Process Systems, Valencia, CA, US); a specialized 8 ft by 8 ft by 8 ft (512 ft 3 ), 1093°C sintering furnace; and digital laser NDT infrared flash thermography equipment, designed by ermal Wave Imaging Inc. (TWI, Ferndale, MI, US) and run under contract from CHI by X-Ray Industries (XRI, Troy, MI). Further, Bill Roberts, a 32-year veteran of e Boeing Co.'s (Chicago, IL, US) Space Shuttle program — was brought in as VP for ceramic operations. Benefits of CMC in engines, compared to metals As noted, a significant characteristic of CMC is its ability to with- stand a very hot engine and that engine's very hot exhaust. at's a significant advantage in this application because when a jet engine runs at high temperature, it typically discharges fewer emissions of carbon dioxide (CO 2 ) and nitrogen oxide (NOx) — thus advancing the aviation industry toward an often elusive, but important goal. Another advantage of CMC is that, like the less high-temper- ature-tolerant PMCs, it is flexible and can be formed into very tight radii — for example, the tight radii and complex shape of an engine mixer. is is in contrast to the difficulty experienced when forming less-flexible metals for this or similarly complex parts, Hynes points out. CMCs for the Hot Zone Mixers are used on small- to mid-sized aircraft engines to improve the mix of the hot core-engine exhaust with the cooler bypass air (air driven by the engine fan that bypasses the core engine). e smooth, tight shape that can be realized in a CMC mixer helps mix bypass air and exhaust more efficiently. e more efficiently those airflows mix, the better the specific fuel consump- tion. is increases engine efficiency and reduces engine noise. "For the same reasons, CMCs also resist acoustic fatigue [vibra- tion] better than, for example, welded titanium," Hynes says, particularly in designs such as the mixer. Metals that are bent or formed in very tight radii tend to exhibit fatigue failure, but CMC is far more forgiving and durable, Hynes explains. CMCs "allow you to build numerous shapes with exotic geometries," Roberts adds, "without the fatigue risk you would have in a welded joint." As a bonus, CMC contributes to lightweighting of the engine structure. "Oxide ceramics are about one-third the density of nickel alloys, with similar or even higher temperature capabili- ties," Hynes says. "So using CMC can make a significant reduction to the overall mass of the engine structure." GE design of parts and materials GE Aviation maintains a separate facility in Huntsville, AL, US, for production of silicon carbide (SiC) CMC materials used to make turbine shrouds, nozzles and other "superhot zone" parts for its LEAP and other engines, through a joint venture with Safran Aircraft Engines (Courcouronnes, France). For sake of cost control, however, GE turned to a different CMC for the Passport 20. "SiC/ SiC is a more expensive material and the temperature require- ment for the Passport 20 exhaust components did not dictate the need for the higher temperature capability that SiC/SiC provides," explains Tim Shumate, CHI VP of sales and marketing. FIG. 1 Managing heat in the engine hot zone Composites Horizons (Covina, CA, US) manufactures the Ox-Ox CMC mixer (far left), centerbody and cowl cover components for the Passport 20 jet engine developed by GE Aviation (Cincinnati, Ohio, US). Source | GE

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