which have been in development since the 1950s. The brake drum is made primarily of aluminum except for the braking surface, which is reinforced with ceramic particles. This process is called selective reinforcement — reinforcement of only the area in need of the ceramic material
leaving the remainder of the
product as a ductile, low-cost and easy-to-machine aluminum material. The ceramic is introduced to the brake drum as a “preform,” essentially a sponge made with ceramic particulates, fibers and a variety of organic and inorganic binders. Depending on the application, the preform is made to a specific volume fraction and density.
Perhaps the greatest challenges to adopting MMCs into mainstream applications are repeatability and cost. Until now, the method to make preforms has been a batch process. Today, the AMTG is working with Century, Inc. to utilize its Century 3+ Ring Extruder technology to develop a highly efficient, continuous mixing method to mass-produce the ceramic preform. Using the ring extruder, the preform material is continuously extruded, formed into shape and thermally processed and machined. The final ceramic preform is then
This new lightweight brake drum manufactured by Century, Inc. is one of many items being considered for vehicle weight reduction. (Photo courtesy of Century, Inc.)
ready to be impregnated with molten aluminum in a squeeze- casting process. After casting, the brake drum is heat treated, inspected with an X-ray and machined to the final size parameters. The entire process can be automated with a very small manufacturing footprint.
This technology has broad application across both the Department of Defense (DOD) and the industrial base. DOD’s ManTech 2009 Strategic Plan identifies “next-generation metal matrix composites”as a critical need for armor and backings. Additionally, this technology will be critical for select commercial truck platforms, especially hybrids and bulk haulers, to meet weight requirements for efficient operation of their vehicles within their respective markets.
Beyond braking components like drums, brake rotors and calipers, engine components are great candidates for MMC reinforcement. The MMC has improved properties over monolithic aluminum at elevated temperatures. For example, MMC cylinder liners allow for tighter cylinder placement, yielding a lighter-weight engine with the same output. Typically, since main bearing caps need to be stif , steel caps are used for an aluminum block. With steel, there are difficulties due to the large difference with thermal expansion between the two materials. Using stiff aluminum composite bearing caps alleviates this concern with less weight. Another popular engine application for MMC is reinforcing aluminum pistons. In one casting process, the combustion bowl and upper ring region can be reinforced with alumina fiber-based preforms. With a significant increase in stiffness, the upper piston ring can be moved closer to the top of the piston, providing improved
combustion and reduced emissions. Overall, the versatility offered by MMC enables an automated process to manufacture MMC- reinforced components of many shapes and sizes.
With the increasing threats to our Nation’s military vehicles and warfighters, the need for weight reduction has never been greater. The TARDEC AMTG’s technology development efforts will soon pay off for warfighters and America’s industrial base. To learn more about this technology and help further its development, military/government organizations can bring their weight reduction challenges to the TARDEC Advanced Manufacturing Team for evaluation. Commercial inquiries, ground vehicle systems concepts, ideas and innovations can be submitted using the electronic form and portal at TARDEC’s Ground Vehicle Gateway at: https:// tardec.groundvehiclegateway. com. All other inquiries should be referred to: http://tardec.army.mil/ contactus.aspx.
Randal Gaereminck is the Associate Director for Integrated Industrial and Sustainment Engineering at TARDEC. Gaereminck holds an Associate of Science degree from Macomb College, a bachelor’s degree from Northwood University and an M.B.A. from the Florida Institute of Technology. He is currently working on a doctorate in leadership from Andrews University. He is also a graduate of the Command and General Staff College, Senior Executive Development Program and Federal Executive Institute. Additionally, Gaereminck has completed the Harvard Leadership Program, Senior Management Executive Development Program, Weapons System Management Program and Logistics and Acquisition Management Program. He is an Army Acquisition Corps member and is level III certified in program management and logistics management.
SYSTEMS ENGINEERING & INTEGRATION