CompositesWorld
Issue link: https://cw.epubxp.com/i/632301
CompositesWorld.com 37 NEWS N E W S N S N E W S E N W S W RCF Potential in Aerointeriors aesthetic surfaces but are not primary structures —a use for which RCF materials have already demonstrated a good ft, for example, in automotive seat components (see "Learn More"). By August 2014, a typical airliner interior cabin sidewall was chosen. Consid- ered secondary structure, these curved liners are attached to the fuselage by clips and provide an interior surface with cutouts for windows but carry no fuselage loads, as do window frames. Only the woven S-glass fabric of the liners was targeted for replacement. "We decided to leave everything else unchanged," says Witte, "because it ofered the most practical approach to demon- strate usability, near term." Te team outlined the process require- ments and began work to optimize the RCF material for process and equivalent perfor- mance at the same or less weight. By the end of 2014, CTC and its supply chain team had produced the frst batch of short- fber RCF veil mate- rials prepregged with phenolic resin and measured their properties. Several months later, the frst sandwich speci- mens were made using RCF veils and honeycomb core. "Now we began to look at the fnal part design and proceeded through several rounds of optimizing the RCF veil for fber length, areal weight and thickness," says Witte. By July 2015, the product design and semi-fnished product (prepreg) specifcation were completed. Te following month, the frst production run of RCF veil prepreg, with phenolic resin, was completed at Gurit. By September, the project team had made four full-size (1.2m tall by 1m wide) demonstrator parts at the Diehl Aircabin facility. Success on the frst try Full-scale demonstration sidewalls were molded via the conven- tional "crushed core" process (see "Learn More") that is typi- cally used by Boeing, Airbus and their Tier 1 suppliers to produce curved interior panels. Honeycomb core, typically made from Nomex aramid paper, is crushed down to a predetermined thick- ness in a large press by heated steel molds under pressures greater than 10 bar. Processing times are approximately 15 minutes, after which a decorative, wear-resistant flm is typically applied (see the photo on p. 36). Te process reportedly went more smoothly than anyone expected. "After 18 months of development, we wouldn't have thought that the frst part produced in the serial machines would be perfect, ready to use," recalls Witte. "But we produced four parts, one after each other, in two hours with no issues, and I was amazed at how good the surface quality was." Although there often is a dimpling efect where the laminate bridges the honeycomb cells in conventional sidewall produc- tion, "with the RCF material we didn't see that efect," Witte notes. Beyond its potential to reduce molding time and cost in post- fnishing, the RCF sidewalls also achieved a 22% weight reduction. Te sidewalls are currently undergoing mechanical properties testing and tests against conventional sidewalls in categories that include noise abatement (acoustic damping) and thermal perfor- mance. Acceptable fre, smoke and toxicity (FST) performance was confrmed during coupon and laminate plate testing before full-scale parts were molded. "Te plan is that by mid-2016, we will reach TRL 6 and start preparing for serial production," says Witte. "Te entire composite industry must start to change from a linear supply chain to a circular supply chain," says Witte, "and we are now one step closer to a circular lifecycle loop for CFRP materials!" Read this article online | short.compositesworld.com/RCFAeroInt Read "Recycling carbon fiber for structural applications" online | short.compositesworld.com/RCFStruc Read more about pyrolysis and RCF processes in "Recycled carbon fiber update: Closing the CFRP lifecycle loop" online | short.compositesworld.com/RCFUpdate Read more about RCF in automotive seats in "CAMISMA's car seat back: Hybrid composite for high volume" online | short.compositesworld.com/Camisma Read more about the "crushed core" process in "Advanced materials for aircraft interiors" online | short.compositesworld.com/AeroIntMat Recycled carbon fiber vs. glass fiber: Three-point bending test results After evaluating myriad RCF material and composite properties, CTC determined that they could meet basic aircraft composite laminate requirements and compete well with current glass fber materials used in sidewalls. These three-point bending test results show that sandwich panels made using RCF veil prepregs (dark and light blue curves) outperform glass fber fabrics in both 0° (direction of veil production) and 90° directions. Source | CTC CW senior editor Ginger Gardiner has an engineering/mate- rials background and has more than 20 years of experience in the composites industry. ginger@compositesworld.com 0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 GFK 1 (45°) GFK 2 (0°) rCFK (90°) rCFK 0° 45° 90° GFK 1 (0°) GFK 2 (45°) rCFK (0°) [mm]