CompositesWorld
Issue link: https://cw.epubxp.com/i/630867
FEBRUARY 2016 10 CompositesWorld OUT OF AUTOCLAVE SUPPLEMENT Fulfilling the promise of OOA composites without sacrificing pressure. Resin transfer molding: An update » Although the origins of resin transfer molding (RTM) reach back to post-World War II marine vessel development in the 1950s, the process was not applied to aerospace composites until the 1980s. RTM has two primary advantages over resin infusion. One is its application of high pressure — typically up to 100 psi, vs. 14.7 psi with vacuum only — although RTM equip- ment can generate pressures above 300 psi. Te other is its use of matched metal molds, which enable tight tolerances, complex geometries and a high-quality fnish on all visible molded surfaces. Its disadvan- tages include mold and injection equipment cost and process complexity, but with continuing advances in simulation tools, the latter is being addressed while the equipment, costly though it might be, ofers a route to automation and holds a defnite edge over infusion in terms of part repeatability. Advanced Composite Engineering GmbH (ACE, Immenstaad, Germany), for example, is manufacturing the Airbus (Toulouse, France) A350 XWB's carbon fber composite window frames, using an automated RTM production line supplied by mold manufacturer BBG GmbH & Co. KG (Mindelheim, Germany). BBG reports that the line installed at ACE's facility in Hagnau, Germany, can produce up to 8,000 composite window frames per year using the current twin BFT-C mold carrier systems (see "Learn More" on p. 11). Addition of four more BFT-C systems is planned, presumably for produc- tion rate increase. Originally developed for the Airbus A380, the frames met a challenge to reduce weight while meeting precise geometry and primary fuselage loads as well as cost targets. Te A350 frames use a complex 3D preform developed by Hightex Verstärkungsstrukturen (Klipphausen, Germany) and Airbus Operations in Hamburg, Germany. Tailored Fiber Placement (TFP, see "Learn More," p. 11) is used to create a 2D preform with both selective stitching (stitches in some areas and not in others) and structural stitching (straight up-and- down stitches), as well as a glass fber interior lining to prevent galvanic corrosion with aluminum interfaces FIG. 1 A350 XWB window frames The A350 XWB window frame preforms use vertical structural stitching and selective stitching to achieve an L-cross-sectioned oval without any wrinkles and a glass fber lining to prevent galvanic corrosion in contact with metal. Source | Hightex Glass fber lining Selective stitching By Ginger Gardiner / Senior Editor Interior edge buildup Vertical structural stitching Interior edge buildup