May 1, 2007 A fiber-reinforced ceramic, traditionally used in jets, has now been made into brakes for cars. The fibers strengthen the material and help keep it from crumbling.
- Automotive and Transportation
- Alternative Fuels
- Materials Science
- Transportation Science
- Fuel Cells
City driving is a pain, and just to add more fuel to your fury, your car's cast iron brakes cost you money every time you drive.
Cast iron is heavy so it reduces the fuel efficiency of your car. Stan Hemstad, a materials research scientist at Starfire Systems Inc. In Malta, New York, has come up with a solution. He has designed a new brake that weighs a lot less. It's made from fiber-reinforced ceramic and it's nearly indestructible.
Hemstad explains his technique, "What happens, instead of cracking, the fibers hold the material together, same thing as adobe bricks. The straw keeps it from crumbling and falling apart." A typical metal brake weighs nearly 20 pounds. This ceramic brake weighs less than five. Hemstad says, "There is a lot of weight savings. That makes the cars accelerate faster, more maneuverable, reduces gas consumption."
However, making the brakes is expensive and time consuming, taking over four hours. Hemstad says the goal is to make them less expensive so they can go on higher-end cars and eventually all passenger cars.
Ceramic brakes are still being tested, but they're already an option on high-end performance cars starting around $10,000. They could be on all cars for less than $400 within three years. According to Hemstad, the gas benefit savings will pay for the brakes. Ceramic brakes also last longer than metal brakes, so there is no need to replace them as often.
The secret behind the ceramic brakes is the special polymer. That polymer is also being used for repairs on space shuttle flights and in circuit boards. Ceramic brakes are now common in the world of motocross racing. One driver even says he's shaved two seconds off his lap time with the lighter material.
The Materials Research contributed to the information contained in the TV portion of this report.
BACKGROUND: Once an expensive high-end component in professional race cars and jet-powered aircraft, ceramic brakes are now being built into high-end cars. As the price continues to come down, they will soon be available in everyday cars, SUVs and trucks. Their lighter weight gives the consumer more miles per gallon, while providing the same performance as conventional metal brakes. They also offer quieter, smoother braking and experience less wear than conventional brakes, lasting four times longer.
WHY WE NEED THEM: As a vehicle accelerates, its rotating parts require more energy to accelerate than nonrotating parts, because they gain energy not only from moving forward, but from their increasingly rapid rotation. So brake discs play an important role in determining a vehicle's fuel efficiency. Furthermore, there is a great deal of stop-and-go in driving, and it takes more fuel to accelerate a heavy car than a light one. Reducing weight can help automakers meet new fuel-efficiency standards. Friction between brake discs and pads takes place every time a driver hits the brakes. That friction generates heat, and over time can wear down the brakes. Ceramics offer both lighter weight and a better ability to withstand higher temperatures and the wear and tear from breaking, at an affordable cost.
ABOUT CERAMICS: "Ceramic" applies to almost any inorganic, non-metallic material formed by heat, most commonly simple ceramics like the clays used in pottery, bricks and tiles, as well as cement and glass. However, single-ingredient simple ceramics tend to be very brittle and break easily. To make ceramics tough enough for a brake disc, and light enough to give it the reduced-weight advantage, the material is made as a composite, in which strands of carbon fiber -- which are highly resistant to stretching -- are embedded in the material. The fibers are woven into a disc shape before being doused with a liquid made of carbon and silicon. That liquid is then heated to convert it into a very tough ceramic known as silicon carbide. The finished surface resembles stone.
CAFE STANDARDS: The Corporate Average Fuel Economy (CAFE) regulations were enacted by Congress in 1975 to improve the average fuel economy of cars and light trucks under 8500 pounds. As of early 2004, the CAFE average for cars must be greater than 27.5 miles per gallon, while light trucks must average more than 20.7 miles per gallon, increasing to 23.5 miles per gallon by 2010. Pickup trucks, sport utility vehicles and large vans are exempt from the CAFE standards.