The race is not to the swift, but to those with the best brakes, says Peter Filip.

Filip, director of the Center for Advanced Friction Studies (CAFS), and mechanical engineering professors Jarlen Don and Ajay Mahajan were in the pits--literally--for the practice sessions of the Gran Prix USA at Indianapolis this year.

Their job? Gathering information to improve brakes for Formula 1 race cars.

"A lot of Formula 1 races are won because the driver can go full throttle and he knows that he'll be able to stop if he needs to," Filip says. "If he doesn't have that confidence, he starts to brake earlier [in the turns], and then he loses."

In a new $400,000-per-year research program, Don, Mahajan, Filip, and staff researchers Poh Wah Lee and Tod Policandriotes will help two well-known Formula 1 sponsors improve brake efficiency and wear resistance. Some Formula 1 races are so demanding that brake rotors must be replaced once or twice per race.

"That can be done by the pit crew in approximately seven seconds," Filip says, "but when you're driving 300 kilometers an hour, seven seconds is a lot."

The SIUC team was in Indianapolis to learn more about the Formula 1 cars, observe racing conditions, and talk to drivers and technicians.

"If you want to model performance and predict wear under real conditions, you have to look at the interaction of a tremendous number of parameters," Filip says.

"For example, you have cooling vents (in the rotors), you have the wings (that hold the wheels down), you have the brake geometry, you have the location of the calipers, you have the stiffness of the system. These are all parameters we were checking while we were there."

The team also gathered data on operating temperatures and other conditions in the practice sessions and during the race.

A National Science Foundation Cooperative Research Center with 14 affiliated faculty in different specialties, CAFS teaches students by involving them in interdisciplinary materials research for braking and other friction applications. Its work is partially funded by 19 companies that make aircraft and automotive components, and it does research for all the major aircraft brake manufacturers.

Historically, much of the center's emphasis has been on carbon-carbon composites, used in brakes for airplanes, race cars, and high-end passenger cars. (They are so named because they have tough carbon fibers embedded in a carbon matrix.) But CAFS also works with other composites that have friction applications.

Some of the composite materials used to make brake rotors and linings have as many as 30 components. "We help the industry understand how those ingredients behave in those formulations, so that they can make educated decisions in developing new materials," Filip says.

For example, the Ohio Aerospace Institute chose CAFS to assess the performance of recently developed ceramic composite rotors from several top U.S. and European aircraft brake manufacturers.

"We looked at frictional behavior, such as the coefficient of friction (essentially, braking power), wear, vibration, and noise," Filip says of this work, which was completed in fall 2003. "We explained the scientific basis of performance--what's actually going on and why certain materials perform better than others."

The findings, some of the U.S. companies told him, improved their competitiveness by narrowing the gap between U.S. and European manufacturing.

"Manufacturing [of brakes] has been a trial-and-error approach," Filip says. "The center has brought a lot of science to bear" to help the industry improve its products.

"Typically the development of one brake lining takes between six months and five years," he adds. "Often, a company develops a brake and it works in the laboratory, but you put it in the car and it experiences difficulties.

"We have the technology to develop a new pad within one month. That's a significant contribution."

Many luxury cars now boast carbon-carbon composite brake rotors infiltrated with tough ceramic particles to better resist wear. CAFS is working with Porsche to develop brake linings compatible with such rotors. "The idea is never to have to replace the pads," Filip says.

At CAFS, faculty, students, and staff researchers use dynamometers and other equipment for friction testing of materials in the lab. Polarized-light, electron, and atomic-force microscopes allow them to analyze wear and to determine how the microstructure of a composite affects performance. And collaborations with national research laboratories, such as those at Brookhaven and Argonne, give them access to synchrotrons and other specialized equipment for high-tech analyses.

With extensive data on friction materials' properties and behavior, SIUC engineers and scientists are devising better composites, better lab testing protocols, and better computer programs to model how materials will perform in real life. That translates into better products for consumers and savings for industry.

For instance, CAFS gave one automaker an alternative to downhill brake testing.

"We analyzed the brakes after the downhill drive and designed a new test in the laboratory which generates the same friction forces," Filip says. "They save a tremendous amount of money."

As a brake lining rubs against a rotor to stop a vehicle, the two surfaces interact with each other mechanically and chemically. That interaction produces what's called a friction layer between the two. The composition, thickness, and other properties of the friction layer determine the brake's effectiveness and wear rate.

Filip recently developed a better way to model the performance of polymer matrix composite brake linings. These composites, used in passenger car brakes, are a mix of brass chips, petroleum coke, vermiculite, and other substances in a phenolic resin matrix.

To see how the constituents were behaving and interacting during braking, Filip friction-tested the materials against a standard-type cast iron rotor at high and low speeds. Then he analyzed the friction layer at the microscopic level.

The results allowed him to better model friction and wear properties for these types of composites so that companies can improve them. Filip's analysis was named by the Institution of Mechanical Engineers as the best paper in automotive technology published worldwide in 2002.

Something CAFS is testing with race cars may hold promise, down the line, for other vehicles. Filip, mechanical engineering professor Ed Hippo, and their students have developed a way to incorporate nanotubes--extremely strong, extremely small carbon tubes whose walls are only one atom thick--into carbon-carbon composites. Friction-testing of this new material, Filip says, produces "so little wear, we can't even measure it."

A leading car company recently tested rotors made of the nanotube-modified composite.

"We know how the material behaves in the lab," Filip says, "but in real life it may behave slightly differently. If you'd like to model and understand a material, you have to get as close as possible to the real world."

Now Hippo and Filip are analyzing the rotors to see if they gave improved performance. If so, they'll extend their research. Different types of nanotubes have different properties; Hippo and Filip will be searching to achieve the highest performance at the lowest price.

If CAFS has its way, brakes will become ever better performing--and brake jobs will become a thing of the past.

--by Marilyn Davis, ed.