The carbon-fiber and epoxy inner rear deck of the $150,000 Ford GT has proved its worth, and Ford Motor Co. of Dearborn, Mich., may consider the composite material in other low-volume models.
The clamshell inner panel ``has performed flawlessly throughout engineering development and in production, with no issues whatsoever,'' said Fred Goodnow, program design, engineering and launch manager on the high-performance Ford GT.
``We are not aware of any carbon-fiber automotive application in the field larger than the GT clamshell inner panel,'' he said.
The panel measures about 4½ feet by 6½ feet and, among carbon-fiber-reinforced automotive part sizes, is in a league with the structural monocoque underfloor tub on the $440,000 Porsche Carrera GT.
``As a result of the success of the GT clamshell inner panel, we would definitely consider this material in future applications,'' said Goodnow, who is based in Wixom, Mich.
But there are drawbacks.
``The limiting factor on carbon-fiber usage is the cost,'' he said. ``The business case would have to support its usage in any specific application.''
Also, he said, the cycle time to make the panel, compared with injection molding, prevents it from being used on higher-volume vehicles.
Executives authorized the Ford GT project in early 2002 on the basis of a concept-car design. Ford displayed the first three drivable models in 2003 at its centennial celebration, and during 2004 began regular production in the spring and retail deliveries in September.
Engineers drew on carbon fiber's benefits in designing the midengine car and equally distributing weight for optimal balance and precise handling. The V-8 engine produces 550 horsepower.
The one-piece, 14-pound composite lid resolved tight-tolerance, weight and complexity issues vs. another inner-lid concept: four or five pieces of individually stamped aluminum. The deck lid assembly consists of the stiff inner structure and an exterior superplastic-formed aluminum skin.
Sparta Composites in San Diego makes the carbon-fiber component, and a Norwalk, Ohio, plant of Mayflower Vehicle Systems Inc. hems the inner lid and aluminum skin. Saleen Inc.'s special vehicle operation in Troy, Mich., handles painting and final assembly.
Epoxy-reinforced carbon fiber ``was the most appropriate material for the application,'' said Valentin Florescu, a Sparta manufacturing engineer. Cutouts complicate production. Deep draws and small radiuses create a geometric challenge in laying up more than 200 plies with distinct patterns, Florescu said. ``We were able to design it so that it is cost effective even with the level of complexity.''
The Toray T600 unidirectional carbon-fiber fabric and woven materials come together in groups of plies totaling seven layers.
``We do not stitch them together,'' he said during a plant tour. ``The seams do not lie in the same spots as you go through the thickness of the part.''
Coast Composites Inc. of Irvine, Calif., made the Invar alloy mold.
In an autoclave, Sparta heats the part with a cure temperature of 290°-300° F for 10 minutes. Sparta Composites, a unit of Sparta Inc., has manufactured about half of the panels for the project's production run of 4,500.
A new variant with a roof modification retains GT design lines and the composite inner rear lid. In early 2006, Genaddi Design Group Corp. of Green Bay, Wis., begins delivery of the modified Ford GTX1 with a removable hardtop aluminum roof. The cost: $38,000 on top of the GT sticker price.