Developing Lightweight Brake Products
Lightweighting is a popular word in the automotive market today. Aluminum body panels, high strength steel frames and body structure, reinforced plastics on the engine. What about the brakes? There are four per vehicle, and they are still iron? Do they work? Sure. Are they heavy? Yes.
As a rotating mass cantilevered on the suspension, brakes represent valuable weight on the vehicle, called the ‘unsprung mass’. Vehicle manufacturers place a premium value on the reduction of unsprung mass, in many cases, twice the value of mass reduced elsewhere on the vehicle.
REL is delivering and continuously developing lightweight brake products for vehicles; including electric vehicles, motorcycles and heavy trucks.
There are limited options for brake materials – iron, ceramic, or metal matrix composite (MMC). Let’s compare weight, cost & life:
*Estimated average brake life
*Estimated brake weight
*Estimated cost of brake life
What are the issues?
Ceramic brakes are very expensive, so only the premium vehicles and race cars can afford such a luxury. What about appearance? Iron brakes rust which causes them to produce sound driving up warranty replacement costs. Even cars that have not been around for long have rusty brakes.
MMC brakes were produced in the early 90’s and first in production on the rear of the Plymouth Prowler. These stir cast composite brakes performed, yet were not suitable for the higher energy loading on the front brakes, and on larger axles. Stir cast brake drums were attempted as well, yet had similar failures due to deficiencies in material properties.
How is REL’s technology different?
REL addresses the deficiencies of cast iron brakes, of stir cast MMC brakes, and of ceramic brakes. Cast iron is too heavy; stir cast MMC cannot perform at elevated temperatures, and ceramic brakes are too expensive. REL has a patented process that provides a functional reinforced gradient (FRG) which enables the placement of a higher volume loading of ceramic in one area and a lower volume loading in another. For a brake disc application, this enables high loading of ceramic on the outer perimeter where the disc is moving the fastest, generating the most heat, and a lower loading inward, which helps the disc maintain flatness and minimize fade in long braking events. See the images below of the functional reinforced gradient of ceramic in the disc, and the corresponding infrared thermal image of a spinning disc, confirming the hottest area is on the outer perimeter.
Brakes performance is dependent on the friction couple that is the friction material (pad or liner) applied to the brake disc or drum to create torque. With the development of a unique brake material comes the need for new friction materials. For MMC’s, these are typically non-asbestos organics (NAO) based materials. REL has been working with friction material providers to test and optimize their materials for MMC brakes, for a wide variety of applications.
For automotive and heavy truck MMC brake discs and drums, and your other MMC product ideas, please contact us here.