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AUG 2018

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NEWS CompositesWorld.com 27 metals will be used to fabricate the fuselage skin, stringers and frames, as well as all doors and wing slats. Placing, infusing dry fibers e MS-21 outer wings feature a standard design that includes an upper wingskin, a lower wingskin, stringers on the inside of each skin, ribs running perpendicular to the stringers, and forward and rear spars. All parts are composite except for the ribs, and the skins and stringers are integrally molded and co-infused. Each outer wing is about 18m long and 3.5m wide at the root. e wingbox is manufactured separately and integrated with the MS-21 fuselage at Irkut's final assembly line. AeroComposit's goal with the MS-21 wing and wingbox was not only to employ OOA infusion, but also to do so with as much automation as possible. Further, the company wanted, wherever possible, to co-infuse composite structures so as to minimize postmold assembly and mechanical fastening. Meeting this challenge would require the use of automated tape laying and fiber placement (ATL/AFP) systems to lay down dry fibers. at presented an additional challenge: Placement of prepregs, whether by hand or machine, offers the advantage of tack that helps stabilize the stackup and minimizes ply-to-ply slippage. Dry fibers, conversely, are inherently untacky and, therefore, consistent fiber wet-out and porosity, the latter of which must be less than 2% to meet OEM strength and stiffness requirements. e thermoset-based, non-prepreg process most discussed as a viable option for getting out of the autoclave and meeting those challenges is vacuum-bag resin infusion. Infusion is not new to composites fabrication in general, but has seen limited use in primary aerostructures, and almost no use in commercial aerostructures. ere are, however, two major exceptions: e wings for the Bombardier CSeries single- aisle commercial aircraft feature dry fiber infused via a process Bombardier calls resin transfer injection, or resin transfer infusion, but the process does employ an autoclave. e second, however, is the carbon fiber composite wing structure for the single-aisle MS-21 passenger aircraft under development by Irkut Corp. (Moscow, Russia). e process also involves infusion, but is done entirely out-of-autoclave (OOA), which makes it truly unique in the aerocomposites industry. is aircraft is quietly proving to the aerocomposites industry the viability of large, infused, OOA primary structures for commercial aircraft. In short, the MS-21 is shaping up to be that first next-generation aircraft. The specifications e MS-21 (also sometimes referred to as MC-21) was designed and is being assembled by Russian OEM Irkut, but composite structures for the MS-21 are being fabricated by sister company AeroComposit (Moscow). Both companies are owned by United Aircraft Corp. (Moscow). Two MS-21 test aircraft have been built to date. First flight was achieved in May 2017 and the plane is expected to enter the market in 2020. It features two Pratt & Whitney PW1000G or Aviadvigatel PD-14 turbofan engines and has a range of 6,000- 6,400 km. e plane will be offered in two configurations, the MS-21-200 (132-165 passengers) and the MS-21-300 (163-211 passengers). ere are 175 firm orders for the plane, almost exclusively from Russian carriers/leasers, including Aeroflot, Red Wings Airlines, UTair, Ilyushin Finance Co. and VEB Leasing. In addition to the outer wings, the MS-21 also will feature infused carbon fiber composites in the wingbox. But autoclaved carbon fiber prepreg will form the wing trailing and leading edges, flaps, spoilers, ailerons, engine fan cases, and interior floor panels and floor beams. Glass fiber composites will be featured in the nose cone, cargo bay floor panels, the leading edge of the vertical tailplane and wing-to-body fairings. Aluminum and other MS-21 Infused Wing A first for commerical aircraft and for the resin infusion process Moscow-based OEM Irkut is developing the MS-21 single-aisle passenger aircraft, set for 2020 market introduction, featuring wings and wingbox fabricated via resin infusion and oven cure by sister company AeroComposit. The wingskins and stringers are co-infused and the composite spars are fabricated separately, all out of the autoclave. Source | Irkut Automating large-part transport One of the key motivations behind efforts to employ out-of-autoclave methods in the manufacture of next-generation commercial aircraft is the potential to reap a signifcant reduction in overall production cycle time. Toward that end, AeroComposit has gone to great lengths to minimize touch labor in MS-21 wing fabrication. This suction-based automation system, for example, is used to move wingskins from one station to another throughout the manufacturing process. Source | Alexander Popov

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