Bentley Making Cheaper, Stronger Carbon-Fiber Parts

TROY, MI – Old-school auto maker Bentley Motor Cars Ltd. is trying a new-school approach to using composite parts where costlier steel or less-rigid plastics traditionally would reside.

Using a method called directed carbon-fiber preforming, Bentley researchers are molding carbon-fiber parts more cheaply and quickly than current processes, while retaining the technology’s lightweight performance and delivering excellent crashworthiness.

Antony Dodworth, principal research manager at the Crewe, U.K.-based auto maker, presents the process at the Society of Plastics Engineers’ Automotive Composites Conference Exhibition here.

So far, much of Dodworth’s work has been via Bentley’s T35-4 low-cost technology demonstrator vehicle. The 2-seat sports car borrows its designation from the auto maker’s former T-Series line of sedans but might more resemble a Pontiac Fiero stripped of its plastic body panels.

“Styling did not style this vehicle,” Dodworth admits coyly. “As engineers, we’ve done our job and we’ve done a half-decent job.”

What the car lacks in style it more than makes up for in functionality. A test bed for a number of Bentley technologies, the car’s body features a front end of DCFP carbon fiber wrapped in a thin layer of metal and a rear-end using the best composite technology from parent Volkswagen AG.

As such, the body weighs 262 lbs. (119 kg), or more than 60% less than that of a comparably sized car.

“It’s a lot lighter and a lot stiffer,” Dodworth says, noting the metal-wrapped application sounds and feels just like steel and appeared on a recent Bugatti concept.

It’s also less-expensive, because Bentley’s proprietary process can rely on the cheapest carbon fiber available and offers a 14% energy-absorption improvement over costlier methods.

Bentley proved the technology’s crashworthiness with six rear-impact structures it installed on a Formula 1 Super Aguri in 2006 and through frontal- and side-impact and pole-crash simulations.

So far, production applications remain few. But Bentley did leverage the process for a carbon-fiber wheel well on its all-new Mulsanne flagship sedan.

The previous wheel-well composite lacked rigidity, Dodworth says, with 165 lbs. (75 kg) of car batteries creating a bounce and shake drivers could feel through the steering wheel. “Unfortunately, no one will see our hard efforts.”

Future applications include a composite floor pan for a coming Audi vehicle.

Dodworth says Bentley would like to use the technology beyond its $300,000 Mulsanne. But the bespoke auto maker launches so few cars, it was not ready for the new volume Continental GT, which was well-along in development before his team could contribute.

“We weren’t there yet,” he says. “And do you want to risk it on a high-volume vehicle, or just sneak it in on your low-volume car?”

Dodworth says Bentley would consider licensing DCFP to other auto makers, sort of. “There is a list of people we would, and there is a list of competitors we won’t.”

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