CompositesWorld
Issue link: https://cw.epubxp.com/i/630867
FEBRUARY 2016 4 CompositesWorld By David Inston / Contributing Writer VBO prepreg on wing structure GE Aviation scores frst use of OOA wing trailing edge on large commercial aircraft. OUT OF AUTOCLAVE SUPPLEMENT FIG. 1 VBO prepreg layup The trailing edge Upper Panel 12 is layed up under cleanroom conditions on the mold tool. Source | GE Aviation » GE Aviation's aircraft manufacturing facilities at Hamble-le-Rice, UK, acquired in 2007 as part of GE's acquisition of Smiths Aerospace, had a long history of aviation innovation dating back to Britain's WWII fghter, the Spitfre, and was the production site over the past two decades for composite parts destined for numerous aircraft platforms, including Airbus and Boeing commercial and military programs. In 2008, a year after it acquired the site, GE won the largest contract in the Hamble plant's history: to design and manufacture the entire wing fxed trailing edge, including the trailing edge secondary struc- ture, for both versions of the new Airbus A350 XWB. Te composites challenge that this package gives GE shouldn't be underestimated: It includes all the upper and lower panels that make up the trailing edge aft of the wing rear spar and the leg fairing door and hinge panels for the aircraft's main landing gear. Given the facility's history, it also was ftting that GE Aviation elected to form the composite secondary structure from out-of-autoclave (OOA), vacuum bag only (VBO) prepreg — a commercial aviation frst — using a technique that GE Aviation Hamble has carefully matured over a period of almost 15 years. Te OOA technology was originally developed in a UK-funded R&D; program and then industrial- ized for the high-performance automotive industry. GE Aviation transitioned the technology, making it suitable for aerospace use. Te new A350 XWB has become the stage for its production debut. Te fxed trailing edge part package comprises about 90 panels per aircraft. Two-thirds of the panels were made from Cytec's (Heanor, Derbyshire, UK) Airbus-qualifed MTM44-1 OOA prepreg using a 6K 2X2 twill Tenax HTA carbon fabric supplied by Toho Tenax Europe GmbH (Wuppertal, Germany). Inter- estingly, the use of OOA material, which can be cured at lower pressures, gave GE some additional design benefts. As is conventional for such aircraft parts, a sandwich construction was used, with aramid paper honeycomb core placed between composite face- skins. GE designers have used a mixture of the well- known Nomex honeycomb and the more recently qualifed and lighter-weight N636. Additionally, with a carbon fber wingbox and higher loads on the A350 fxed trailing edge structure, thicker honeycomb islands with steep ramp angles were required. One of the challenges to overcome was that the honeycomb might collapse during the conventional autoclave process. Apart from throughput and cost advantages the GE OOA process is expected to bring, their process for the most part has eliminated this technical risk. Early in the project a decision was made to design the largest, most heavily loaded panels using in-auto- clave materials to reduce risk. However, in light of the positive experiences with the OOA process, these