When it comes to carbon fiber for vehicle applications, the definition of what constitutes a "volume" vehicle has a different meaning than most everyone understands. Currently, the market for carbon fiber in the auto industry is limited to specialty models, where 10,000 units is a large run. That's not high enough for Plasan Carbon Composites (Bennington, VT; www.plasanusa.com). "This September we'll be capable of producing 50,000 units for a single model by increasing automation in the lay-up process and reducing overall cure times," says Dalton Blackwell, Plasan's v.p. and general manager. Automation will place the pre-impregnated (pre-preg) carbon fiber in a mold or wind it around a plug, while new resin chemistry reduces cure time without causing the part to set up before it's vacuum bagged and placed in an autoclave. According to Blackwell, curing speed isn't the problem as: "You could cure parts in 20 minutes if you had everything in place to support that." A less accelerated initial cure, however, will make it possible to batch build multiple parts, cure them together, and greatly increase throughput.
Blackwell is quick to dismiss expectations that this technology has crossed from aerospace to automotive, and says they are interested in Plasan's processes, especially as regards the quick autoclave turnaround time. "We've been making 70 fenders a day for the Corvette Z06 since 2005," he says. "So we've worked out a lot of the kinks in the process, which has let us produce more than the 1.5 parts per day you'll find at most aerospace suppliers." In addition, Plasan's position as the highest-volume supplier of OEM parts also means that companies are more willing to develop unique low-cost fibers for use in automotive applications. "Today, most of the carbon pieces in automotive are made from aerospace-grade carbon fiber," says Blackwell, "because it gives a nicer finish." Yet the visible woven finish most people identify as "carbon fiber" is used only in pieces where image is important. However, those parts have stringent detail finish requirements that results in a lot of scrap.
"Woven fiber parts are only 10% of production, with the rest made of uni-directional fibers that can be oriented as necessary to put strength in the part where it is needed," says Blackwell. Not only does this ability to place support where it is needed and eliminate it where it is not make uni-directional carbon fiber more cost-effective than the woven variety, it also makes uni-directional parts stronger because patches can be placed around brackets and in high-stress areas in ways that would not be possible on a part whose visual beauty is equally as important as its structural capability.
Blackwell also is looking beyond the visible to the invisible, and is interested in producing structural pieces for the auto industry. "This is where automakers will get a higher return on weight savings and where carbon fiber makes the most sense," he says. He suggests it is uniquely suited to hybrid and electric vehicles where carrying large numbers of heavy batteries reduces vehicle range, and foresees battery tubs and related structures made out of the material. In addition, structural composites could be used in some full-size truck models to reduce weight and lower the center of gravity. Its use also could be expanded to create front end modules with integrated composite bumper beams that reduce front end weight and length without sacrificing safety. As you might expect, Plasan currently works with each of the domestic OEMs, and has seen increasing interest from the transplants.