Body panels on two different high-performance sports cars accent non-metals. That's not news, but what makes the material choices a cut above the norm is the engineering expertise that made it possible.
A particular challenge on the 2009 Chevrolet Corvette ZR1 involved the complex shape of the carbon-fiber fender vent, which required that the molds "be built so that the cured fender can be removed. The mold had to be designed to allow for adequate draft and clearance in three dimensions," explained Lars Severance, Manufacturing Engineer for Plasan USA, which displayed some of its lightweight solutions at the SAE World Congress in April.
Sixty-four different pieces make up the fender. "Each carbon-fiber subcomponent is shaped for a specific location like a complex jigsaw puzzle," said Severance. After each piece is placed in a mold, the autoclave-cured fender is machined via CNC equipment. The fender then undergoes a specialized finishing process to prepare the surface for priming before the part is shipped to General Motors' plant for final body assembly and painting.
In addition to the front fenders, Plasan provides the Corvette ZR1 with its other carbon-fiber panels: the hood, roof, bow cover, front splitter, and rocker moldings. Supplying exposed carbon weave panels in production-run quantities is unusual. "The difference from what we're doing with the current Corvette Z06 is the exposed carbon-fiber weave. With the 2009 Corvette ZR1's hood, we're doing both styles of carbon fiber—exposed weave on the underside and painted on the exterior—on one part, which is two panels bonded together," said Robert Schudlich, Account Manager for Plasan USA.
Like the current Corvette Z06's sheet molding composite (SMC) hood, the carbon-fiber hood meets crash performance requirements, thanks to its built-in reinforcements and specifically designed inner geometry. Bottom line: "The many specialized processes involved in manufacturing carbon-fiber exterior body panels have to be 'stepped up' in order to produce quantities needed to support Corvette production," Severance said.
The 2008 Dodge Viper SRT10's unique SMC hood provides a pathway for air to cool the new 8.4-L V10 engine that produces 600 hp (447 kW) and 560 lb·ft (759 N·m). "It's one of the only production hoods on the market with louvers integrated into the Class A surface in a single molding. Most hoods, whether sheet metal or aluminum, have an opening cut in them with a thermoplastic trim ring to create the louver," said Tyler Hardy, Director of Engineering for Composite Products at Meridian Automotive Systems.
Viper's previous hood, also supplied by Meridian, had five smaller openings vs. the new SRT10 hood's three larger openings on each side of the raised power dome. "This hood is unique in the fact that we use a robotic laser to trim the backside of the louver openings after the molding process, then the inner and outer hood panels are adhesively bonded and primed to prepare for the final color. The hood is produced at Meridian's Shelbyville, Indiana, plant. All body panels, including the hood, are sent elsewhere for a final top coat prior to delivery to Chrysler's assembly plant in Detroit," said Hardy.