With an eye to reducing a vehicle’s weight and its carbon footprint, a collaborative project called CAMISMA (carbon fiber-amid-metallic structural interior component using a multimaterial approach), supported by the German Federal Ministry of Education and Research, is funding research to combine steel and light alloys with fiber-reinforced composites, including carbon fiber, in hybrid automotive designs. Coordinated by Evonik Industries AG (Marl, Germany), the project’s partners include, among others, Johnson Controls (Milwaukee, Wis. and Burscheid, Germany), Jacob Plastics GmbH (Wilhelmsdorf, Germany), Toho Tenax Europe GmbH (Wuppertal, Germany) and the Technical University Aachen (Germany).
“The automotive industry is starting to demand carbon composites but, currently, carbon fiber doesn’t make sense for cars since the weight benefit doesn’t compensate for its total lifecycle energy,” contends Dr. Matthias Berghahn, who is responsible for the project at Creavis, the strategic research and development unit of Evonik Industries.
The three-year project, which will run through 2014, involves designing and developing an automotive seat backrest using off-spec carbon derived from fiber manufacturing and, eventually, recycled carbon parts. Evonik is about to develop a fully automated continuous process, known as “in situ polymerization,” which takes reclaimed carbon fiber and combines it with heated polyamide 12 (PA 12) monomer tweaked with a proprietary initiator. The result will be a nonwoven tape that Evonik calls an “organic sheet.” Because only a monomer is used, not a polymer resin, the viscosity is very low and, thus, it reportedly is possible to fully wet out the fibers as the monomer polymerizes during the process, explains Berghahn. “This is different from a traditional powder coating or a hot-melt system,” he adds. “This way, we get fast coating of the fibers for better tape production throughput, and good, void-free mechanical properties, because fiber wetout is so complete and independent of the sizing used on the waste fibers.” Part preforms can be created from the organic sheet (or tape), then heated and placed in the mold. With the application of heat and pressure, parts can be created quickly. Two types of tape are in development: a unidirectional product made with off-spec yet good-quality fibers, and a random nonwoven, made entirely from recycled fibers.
At present, says Berghahn and Axel Koever, manager of new technologies, Johnson Controls Automotive Experience, the composite seat backrest is still in the concept stage while designers determine the right mix of the tape and virgin carbon materials, combined with metallic elements and fasteners, to meet energy absorption and safety requirements. “Eventually we hope to use as much of the nonwoven recycled tape as possible, and as little metal as possible, to fully exploit the benefits of the recycling,” says Koever. A small demonstrator backrest is scheduled for completion late in 2012, and a full-scale test will occur at the end of 2013. Meanwhile, Evonik is still developing the resin recipe, and a tape production machine has just been ordered for installation at Technical University Aachen. The tape material won’t be in production until the end of 2012 at the earliest.
Interest in the project is high, says Berghahn, who plans to present a technical paper on CAMISMA in September at the SAMPE Technical Conference in Charleston, S.C. “We can’t landfill carbon waste in Europe,” he sums up. “It is essential that we recycle these high-value materials.”