An Australian company called Carbon Revolution is leading the way in production of carbon fiber composite automotive wheels, using new, proprietary high glass-transition temperature epoxy resin and unique dry fiber-forming technologies.
Its first wheel for a semi-production car is on the track-focused 2015 Ford Shelby GT350R Mustang, savings 60 pounds per vehicle compared to equivalently sized cast aluminum wheels. Each wheel weighs 18 pounds versus 33 pounds for the aluminum version.
Previously, only the automotive aftermarket and a low-volume supercar manufacturer (Koenigsegg) have offered carbon fiber wheels.
Ford engineers say that the carbon composite wheels improve suspension response times, chassis dynamics, steering feel and ride quality. The wheels also provide a reduction in rotational inertia of more than 40 percent, which positively impacts acceleration and braking performance. The springs and MagneRide dampers had to be recalibrated because the suspension can respond considerably faster to road inputs.
Precisely manufactured carbon strands are arrayed into woven fabrics to form a one-piece wheel and then placed into a mold using manufacturing techniques developed in a regional collaboration that includes Deakin University in Geelong, one hour from the Victorian capital of Melbourne.
An RFID chip with a unique tracking number is embedded in the structure. The assembly is then infused with resin and cured at high temperatures in a resin transfer molding (RTM) process. Hollow core spokes are used to boost wheel stiffness. Aluminum lug seats and backer plate sandwich the composite structure to create a strong joint.
Previous designs used pre-preg material with bonded joints between spokes and hubs.
Cured wheels are analyzed using 3D computerized tomography (CT) in which more than 18,000 X-ray images are taken. If the wheel passes inspection, it undergoes machining for the valve stem and mounting hardware holes before it gets painted, coated, assembled, dimensionally checked and shipped to Flat Rock Assembly Plant in Michigan for installation on a new Shelby GT350R.
Significant development was required to meet Ford standards, including curb strike, surface finish, chemical exposure, and heat resistance.
A ceramic plasma arc spray on the inner barrel and back of spoke surface on the front wheels–a technology borrowed from the original Space Shuttle main engine turbine blades–provides thermal protection from brake heat. The result is a ~0.3 mm thick, nearly diamond-hard coating.
A special coating was also developed to protect the resin from the environment. Ford says that the Mustang wheels have a high-gloss black finish based on proprietary processes. It’s difficult to achieve high-quality surface finishes with carbon composites.
The specialty resin developed for the wheel has improved thermal properties, high-yield stress and elongation properties, and abrasion and weathering resistance, according to Ford.
RTM tooling provides investment savings compared to low-pressure cast aluminum wheel tooling and significant savings versus tooling for forged wheels. Ford did not disclose the net increase in cost due to the higher cost of composite materials compared to metals.
Production of the wheels for the track-focused Mustang model is still very small scale–about 10 per day, with production expected to double next year at Carbon Revolution’s Waurn Ponds, Australia plant. Ford views the composite wheel program on the Mustang as a testbed for higher-volume cars.
The base technology has an interesting back story.
The Australian government helped finance the Victorian Centre for Advanced Materials Manufacturing at Deakin University after local industries, including aluminum smelting had collapsed. In 2014, a $34 million, open-access carbon fiber/composite research facility called Carbon Nexus opened at Deakin University’s Geelong Waurn Ponds campus.
Carbon Revolution was formed in 2007 as part of a competition at Deakin University to develop a prototype carbon composite wheel for a race car.
The wheel was a finalist in the 2015 SPE Automotive Division Innovation Competition.