MMC brake drum 45% lighter than cast iron

Image: Century Lite Drum on Steer Axle.jpg

Military, hybrid, and commercial bulk hauler, concrete, and refuse trucks are potential applications for Century’s selectively reinforced aluminum MMC brake drum.

Lightweighting is a goal not just for light vehicles, as the folks at Century Inc. will gladly tell you.

At a recent defense vehicle show “well-attended by the large vehicle manufacturers, many of which have commercial vehicles as well, the interest in this technology was overwhelming,” shared Andrew Halonen, Technical Business Development, Century Inc.

The technology to which he is referring is an aluminum metal matrix composite (MMC) manufacturing technology developed by Century’s Advanced Materials Division, along with a demonstrator component for heavy trucks. The 15- x 4-in brake drum weighs 38.5 lb (17.5 kg) and is interchangeable with standard cast iron drums weighing 70 lb (32 kg).

“For a particular military truck that has eight drums, a lightweight Century drum is expected to save 250 lb,” Halonen said. “Plus, because 1 lb of unsprung mass saved is equivalent to about 4 lb elsewhere in the vehicle, we are talking of 1000 lb of weight savings by changing just one component type.”

For a larger drum such as 16.5- x 8-in, which weighs 132 lb (60 kg) in cast iron, “we expect the selectively reinforced aluminum MMC brake drum to weigh 73 lb (33 kg),” he added.

In addition to military ground vehicle programs, which are battling with gross vehicle weight growth due to additional armoring, Century is also working with commercial customers who want to integrate the drum to their Class 8 hybrid vehicle demonstrator platforms.

“The Century Ring Extruder technology is unique in that it utilizes a highly efficient, continuous mixing method to mass-produce the ceramic pre-form, which is the basis of a selectively reinforced MMC component,” Halonen explained. “A pre-form is essentially a sponge, made with ceramic particulates, fibers, and a variety of organic and inorganic binders. Using the Ring Extruder, the pre-form material is continuously extruded, formed into shape, and then thermally processed and machined, leaving a pre-form ready to be infiltrated with aluminum via the squeeze casting process.”

Because the 12-screw extruder produces the pre-form in a continuous process, batch-to-batch variations are eliminated and automation is enabled, “leading to efficiencies, repeatability, and versatility never before seen in the MMC business,” he said.

Beyond weight savings, benefits of the technology include selective reinforcement—placing the ceramic reinforcement only where it is required—which allows a lightweight component to withstand the required operation fatigue and minimizes the cost of machining composites. MMCs also reportedly provide a 40 to 80% increase in stiffness, improved wear resistance, and improved properties at elevated temperatures compared to the base alloy, usually aluminum or magnesium.

The best candidates for selective reinforcement, according to Halonen, are braking components—drums, rotors, and calipers—and engine components—pistons, cylinder liners, and connecting rods.

The Ring Extruder process technology has been under development for the past five years, and a recent test of the brake drum demonstrated that the technology is ready for scaled-up production, according to Halonen.

Century plans to develop a lightweight brake drum jointly with a vehicle manufacturer and then transition to a licensing agreement for mass production. The manufacturing process could be ready for production within one year.

The cost of an MMC component will depend on a number of factors, according to Halonen, including production volume, size of the component, component complexity, and the type of reinforcement. “Weight-sensitive markets will pay a premium for lightweight components; the target premiums for MMC components are $4-10 per pound of weight savings,” he added.

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