The Society of Plastics Engineers (SPE) held its annual Automotive Composites Conference & Exhibition (ACCE) at the Michigan State University’s Management Education Center in Troy, Mich., from Sept. 11 to 13. The current uptick in the automotive industry was certainly in evidence — the facility was packed to capacity with automotive industry engineers as well as composites industry suppliers, and exhibition booths and tabletops took up virtually every extra square inch of space at the venue.
Tuesday morning’s events started with an introduction by by Creig Bowland of PPG Industries (Pittsburgh, Pa.), the ACCE Chair, followed by three simultaneous tracks of technical papers and presentations. Some highlights from the excellent presentations included Lee Harper of Nottingham University (Nottingham, U.K.), who discussed new work in producing carbon fiber preforms by spraying discontinuous fibers with binder, similar to Ford Motor Co.’s (Detroit, Mich.) P4 preforming method, originally developed in the early 1990s with Owens Corning (Toledo, Ohio) and Aplicator System AB (Molnlycke, Sweden). Harper and his research team have created a process simulation tool to help predict sprayed fiber preform performance and optimize the method, and also now have a way to orient fibers during the spray process, while maintaining fast fiber throughput. The oriented preforms deliver the same stiffness as continuous unidirectional tow, claims Harper, with good strength retention, and other materials like fabrics can be incorporated, offering a lower-material-cost option for molding high-performance structural parts.
Preforms in general were a hot topic, with two full sessions devoted to new technology. For example, Dan Buckley of American GFM Corp. (Chesapeake, Va.), highilighted his company’s light-curable binder that cures in less than 1 second, on simple, low-cost tooling. The light cure can be varied to selectively control stiffness where needed and the preform can be combined with cores or with thermoplastic skins, for example. He emphasized the importance of drapeability, or, as he preferred, “conformability,” which is key to a successfully formed preform. Sigmatex High Technology Fabric’s (Benicia, Calif.) Jonah Jimenez discussed his company’s ability to weave custom preforms using a high-speed, three-dimensional Stäubli (Faberges, France) Jacquard machine. While admitting that the weaving process adds cost, Jimenez pointed out that material can be quickly produced continuously in long rolls, and in multiple shapes and fiber types, at a price approaching that of 2-D fabrics. Interest was also high in a paper presented by Tommy Fristedt of LayStitch Technologies (Highland, Mich.), a tailored fiber placement technique that produces a flat preform in a “printing” manner, using stitched carbon tows for reinforcement. The company claims almost zero waste, since the preform can be stitched and layed down exactly as needed, and stitching can be selective, for maximum conformability in the mold. The company’s products have been used by Airbus for aircraft window frames, and Fristedt believes the low cost and improved stitching speed, as well as the ability to incorporate electronic wires for example, can yield cost-effective, multifunctional preforms for automotive.
Also much discussed were advances in thermoset chemistries for rapid processing. Roman Hillermeier of Momentive Specialty Chemicals GmbH (Iserlohn, Germany) discussed a way to accelerate structural part cure with a new-generation epoxy resin formulated with a latent short cycle; the resin cures in five minutes but maintains a lower viscosity for a four-times longer resin injection window in a gap impregnation RTM process, while delivering a higher Tg and a Class A finish. The new Momentive EPIKOTE resin (with EPIKURE curing agent), intended for carbon fiber automotive parts and at least 50 percent fiber volume, is aimed at automated, large-series production. Also offered by the company at the show is an even faster-curing epoxy, (EPIKOTE Resin 05475) with a two-minute cure cycle, that still allows complete fiber wetting and mold fill while delivering good mechanical properties.
The first of two panel discussions, “Design and Assembly of the Multi-Material Car,” included Saad Abouzahr of Chrysler Group LLC (Auburn Hills, Mich.); Jay Baron of the Center for Automotive Research (CAR, Ann Arbor, Mich.); Oliver Kuttner of Edison2 (Charlottesville, Va.), the startup car company that won the Progressive Insurance Automotive X Prize for proving 100+ mpg; Gary Lownsdale of Plasan Carbon Composites (Wixom, Mich.); Tom Pilette of Magna Exteriors and Interiors (Troy, Mich.); and George Ritter of EWI (Edison Welding Institute, Columbus, Ohio), a not-for-profit research group dedicated to joining issues. This diverse group, moderated by Lindsay Brooke of Automotive Engineering Magazine (published by SAE International), engendered some lively discussion, particularly given Kuttner’s outspoken opinions on rethinking entirely what cars are or even should be, and starting with a clean design sheet. Many on the panel pointed out that combining multiple materials in modern cars, which is already done in many cases, is difficult and complex, particularly related to joining and bonding. There was some agreement that education of young engineers is key to understanding this complexity, and that giving those engineers more freedom to design in a new space, beyond today’s conventional suspension and body architecture, is necessary. Things really got lively when Abouzahr threw down a gauntlet, saying essentially that the composites industry cannot deliver a body panel that can be made quickly, at a low enough density, with a Class A finish, and a low price, for a high-production rate vehicle model. Lownsdale countered quickly, saying that such technology is possible and that a new generation of engineers will be able to meet such a target. Baron made a cogent point, saying “The best part is no part,” meaning that innovative part consolidation is a huge benefit offered by composite materials. As always at such events, the question was asked: Since aerospace programs tend to consume available carbon fiber, will there be enough supply? It was pointed out that the steel industry is very aggressive in designing new forms and alloys that can be made thinner and thinner, yet, said Ritter, that can only go so far. Lownsdale applauded the recent alliances and partnerships that virtually every automotive OEM has made with a carbon fiber producer, to ensure supply. And, he added, what is really happening in the end is judicious use of smaller quantities of carbon fiber where needed — not entire bodies.
The remainder of the event included many more presentations, including some on the opportunities and challenges of carbon fiber supply. Cliff Eberle discussed the Oak Ridge National Laboratory’s efforts in developing alternative carbon precursors lignin and polyolefin. The lab’s new carbon fiber line, slated to open in February 2013, can produce both tows and a web-laid mat, which could be extremely attractive to auto OEMS as a low-cost carbon material form that still delivers good properties. George Husman of Zoltek Corp. (St. Louis, Mo.) delivered an interesting presentation in which he asserted that most part manufacturers are struggling with process — that is, finding the most effective and efficient way to make carbon composite parts. He believes that a carbon fiber-filled SMC shows much promise, because of its lower density than glass at the same fiber content, and that thinner part profiles are possible. He also discussed the concept of using unidirectional continuous fibers in selective reinforcement of a low-cost, injection molded part. “We need more creative design for manufacturing to advance composites for broader use,” added Husman.