High-Performance Composites

NOV 2014

High-Performance Composites is read by qualified composites industry professionals in the fields of continuous carbon fiber and other high-performance composites as well as the associated end-markets of aerospace, military, and automotive.

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4 0 | H I G H - P E R F O R M A N C E C O M P O S I T E S PLANT TOUR / FACC AG delivered its frst set of Aviation Partners Boeing's (APB, Seattle, Wash.) trade- marked Blended Winglets for the Boe- ing 737 Next Generation (i.e., -600/-700/- 800/-900 series) in 2002. It then worked with APB to retroft them to Boeing 757 aircraft. In 2010, FACC delivered the 3,000 th shipset of Blended Winglets and was named single-source supplier for the product lifetime. It collaborated again on APB's next de- sign, the Split Scimitar Winglet (see Fig. 4), performing stress analysis, manufac- turing development and production tool design and fabrication. The name de- scribes use of both a split winglet design and high-performance scimitar-shaped tips, which, combined, cut aircraft fuel consumption by about 2 percent. FACC prototyped the winglets in only three months. In 2013, FACC worked with Airbus to develop new winglets for the A350 XWB, which measure 2.3m/7.5-ft wide at the base and 2m/7-ft high. FACC was respon- sible for the development, qualifcation, production tooling design and fabrica- tion, as well as testing, series production and assembly of the individual compo- nents into a ready-to-install system for delivery to the Airbus fnal assembly line (FAL) in Toulouse, France. This pro- gram was the frst in which tests on full- scale parts of this size — wingtips with attached winglets are 6m/20-ft long — were carried out at FACC's Composite Lab and Test Center (see Fig. 4, p. 41). The complete winglet system was sub- jected to static and dynamic testing for resilience, fatigue and endurance, up to mechanical failure, and was in the fnal stages of completion during HPC's tour. S I D E S T O R Y FACC: Aerospace infusion pioneer Fig. 2 Preforms for the A350 XWB spoiler center hinge fitting are shown here, prior to resin transfer molding. Source: FACC Fig. 3 In the run-up to fabrication of prototype OOA wingbox components for the Irkut MS-21, FACC found dry fiber layup using NCF and infusion via its large-format MARI technology much faster than prepreg and potentially faster than ATL with system optimization and new NDT developments. Although it's "new" to aerospace, liquid resin infusion has been the focus of R&D at FACC (Ried im Innkreis) since 2001. "The issue," said FACC's aerostructures product development director Hermann Filsegger, "is in getting 100 percent wetout with no voids in a large part with this much complexity." That's not, by any means, an easy task. The skins FACC developed for Moscow, Russia-based Irkut's MS-21 wingbox, for example, are more than 1 inch/25.4 mm thick at the roots, with stringers on top. On such a critical component, Filsegger pointed out, "It is not acceptable to go back and do 'emergency' processes to remediate dry spots." The diffculties encountered in the infusion of large parts prompted FACC to develop its patented process, called membrane-assisted resin infusion (MARI). Filsegger contends that it does not infringe on the Vacuum Assisted Process (VAP) pat- ent because the membrane is not applied directly to the part surface (see "Learn More," p. 45). "It is still in the breathing path but easier to apply and enables a very robust process that takes care of the consistency problems while de- livering 100 percent impregnation." When asked about the cost of producing primary structures in this way, Filsegger explained that the dry fber lay down is much faster than hand layup and even automated prepreg layup, due to the lack of tack. "This integrated wing panel has just a slightly curved surface," he noted. "So laying these fab- rics is like rolling out carpet. The noncrimp fabric basically prefabricates your laminate, confguring fve plies into one layer." (See Fig. 3, below.) The company continues to refne its proprietary MARI process with an eye toward production of primary structures. Can OOA liquid infusion molding compete with ATL prepreg in production manufacturing? Filsegger said yes, assuming some necessary innovations in NDT. "But we still need to work on the right fber materials for permeability and also better fow resins with a short cure time." He pointed out that the entire system must be developed together — fber, resin, process and inspection — and much work remains in optimization. Well-developed processing technol- ogy notwithstanding, such work also demands a commitment in time and perseverance. "Our thermoplastic copo- lymer is woven into the fabric, making up 8 percent of the laminate without any clustering or fltering of the toughener," he said, by way of example. "We did many tests, trying four to fve resins and then 10 to 15 different combinations of param- eters to see what worked and how to minimize variability, realizing that permeability is the largest cause of unreliability in infusion." "Only one resin worked," he added, naming Cytec's (Woodland Park, N.J.) 977-20 toughened epoxy resin system. Source: FACC Source: FACC

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