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SEP 2017

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SEPTEMBER 2017 84 CompositesWorld FEATURE: AUTOMATED PREFORMING, PART 2 TFP evolves CW reported on the use of tailored fiber placement (TFP) for preforming in 2013 (see Learn More). "e first automotive composites application for TFP was 15 years ago in the engine brackets of the Bugatti Veyron," says Tailored Innova- tions (Highland, MI, US) founder Tommy Fristedt. He notes that more than 100 TFP machines, adapted from industrial embroi- dery equipment, have been installed for preforming composites in Europe and Asia. TAJIMA GmbH/Filacon Systems (Winterlingen, Germany) has a license to sell the machines. "TFP allows orienting the fiber in shapes other than just a straight line," says Fristedt, "for example, as reinforcements for holes and hard points for attachments." It can use glass, carbon, aramid and polymer fibers in a range of tow sizes. "We have processed heavy fiber, up to 610K, from Oak Ridge National Laboratory [Oak Ridge, TN, US]," he adds, "but, of course, this has to be combined with knowledge of how to achieve resin impregnation to achieve a good preform design." Patrick Schiebel, a research engineer at Faserinstitut Bremen eV (FIBRE, Bremen, Germany), has worked with TFP for 12 years and is now developing preforms that use a single thermoplastic as rein- forcement and stitch fiber. "We have produced load-optimized preforms, which are quickly thermoformed into parts," he explains. "e Airbus A350 window frames, made using TFP, are processed in four hours, using RTM, but require only half an hour with thermoplastics." ese preforms also may be overmolded to inte- grate bosses, ribs and attachment points into the final part. "We've made preforms using this technique with polyetherether- ketone (PEEK) and polyaryletherketone (PAEK from Victrex [Cleveleys, UK]," says Schiebel. He points out that the preconsolidated preform must be heated again to get a good interface with the overmolded plastic. Using the lower melt temperature PAEK as preform and overmolding with PEEK works well (see Learn More). "You can also use PA6 and PA66," adds Schiebel, who also reports making preforms with curved paths as small as 10 mm in diameter. "For consolidation, the rollers provide compaction and we have used infrared heating to tack the bindered dry fabrics or prepregs," says Borgwardt. "We've also used inductive heating for faster process time and thicker laminates." COPRO has processed straight profiles with as many as 10 layers at speeds of 400 mm/sec, and curved profiles, with as many as four layers, at a rate of 50 mm/sec for more complex shapes, such as door surround frames, which use as many as three layers of biaxial or triaxial NCF (e.g., ±45° or ±45°/90°). e COPRO approach handles localized shaping. But can it provide local reinforce- ments? "We can start and stop input bands like an ATL head," says Stahl. "We do the same for stringer flanges, feeding in 0° unis from extra side spools, or start extra layers before a joggle and stop after a joggle. We can also combine with a pick-and-place robot for other types of patches."

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