CompositesWorld
Issue link: https://cw.epubxp.com/i/632301
FEBRUARY 2016 36 CompositesWorld WORK IN PROGRESS » Te Composite Technology Center (CTC, Stade, Germany), a subsidiary of aircraft manufacturer Airbus (Toulouse, France), is dedicated to developing new technologies for the production and assembly of carbon fber-reinforced plastic (CFRP) composites for aircraft. In December 2014, CW reported on a CTC project designed to demonstrate the use of recycled carbon fber (RCF) materials in a full-scale aircraft interior sidewall panel (see "Learn More" on p. 37). Demonstration panels are now complete and in testing. When CW revisited the project, CTC researcher Tassilo Witte explained more about its motivation and future implications. "Currently, production of recycled carbon fber exceeds the market demand because too few potential applications using these materials have been investigated up to now," he noted. "With a recycling capacity of more than 1,000 MT per year in Germany alone, there is a signifcant source of raw material to be tapped!" And more recy- clate is generated each day. Te CTC's project's goal, then, was to begin developing parts using this RCF stockpile. "Instead of using continuous glass fber," says Witte, "we use short-length recycled carbon fber, which competes directly, performance-wise." Targeted development Witte walks CW through project's timeline. "At the beginning of 2013, we started looking at CFRP recycling and talking to recy- cling companies, analyzing the supply chain from raw material An Airbus-led team characterizes RCF veils and shows their ability to best glass fiber composite sidewalls in cost, weight and surface finish. Recycled carbon fiber proves its potential for aircraft interiors production all the way to companies who use the recycled CF products." Witte then assembled a team that included CarboNXT (Stade, Germany), RCF materials supplier; Gurit (Kassel, Germany), a phenolic prepregger; cabin lining manufacturer Diehl Aircabin (Laupheim, Germany) and aircraft OEM Airbus. "Our frst goal was to investigate the performance of RCF mate- rials," Witte recalls, noting one of the frst questions the team faced: "Was it even possible to reuse the reclaimed fbers in an aircraft application?" CTC characterized veils made from CarboNXT RCF materials as well as monolithic laminates made with the veils. Produced by CFK Valley Recycling (Wischhafen, Germany), these RCF veils began as either dry fber scraps, prepreg waste or parts. Te materials were sorted according to state of processing and type of carbon fber, and then crushed in preparation for pyrol- ysis. Temperatures of 400-500°C in the oxygen-excluded pyrolysis furnace removed any remaining matrix materials but preserved fber properties. CFK Valley Recycling then conditioned the fber surface for optimum adhesion as required by its prospec- tive end-use. Te fbers then were cut to a standard length and processed into a nonwoven veil, using either wet-lay or air-lay textile machines (see "Learn More"). After six months of testing, CTC had evaluated the RCF material properties and determined that they could meet basic composite laminate requirements. "Our next goal," says Witte, "was to identify a part for demonstra- tion." Interior panels were a good candidate, because they serve as RCF for cabin panels Four full-size aircraft interior sidewalls, made using carboNXT recycled carbon fber veil prepregged with Gurit standard phenolic resin, were produced at Diehl Aircabin's facility and are now undergoing tests. One of the four is shown here at far left, half covered with decorative foil (white) and the other half, showing the uncoated RCF composite (black). It reportedly has a surface fnish equal to or better than that achieved on conventional glass sidewalls like the sample (coated and uncoated) displayed to its right. Source | CTC