MRS Talks Reveal Long Materials Wish List for Automotive Industry

Materials innovations are taking center stage in applications ranging from mile-long suspension bridges to microscopic motors that are only a few nanometers wide. Materials have played a particularly large role in the transportation industry, which has accounted for nearly 11% of the U.S. gross domestic product since 1989, according to Market Analysis: The Report on the Vehicle Parts Industry 1998 Pocket Overview.

Published in 1998 by the Motor and Equipment Manufacturers Assoc. (Research Triangle Park, NC), the report makes it obvious that reducing costs and increasing efficiencies in automobile production and operation will have a major impact on the nation's economy.

To make cars lighter and more fuel efficient, manufacturers have traditionally reduced vehicle sizes and used composites instead of heavier materials for automotive parts. Today, strict environmental regulations coupled with an increased consumer demand for large-bodied vehicles are requiring car manufacturers to pursue craftier approaches to decrease car weights and improve efficiencies.

"For every 100 kg saved in the weight of a car, its fuel efficiency increases 10%," says Christine Sloane, technical director for the Partnership for a New Generation of Vehicles (Warren, MI). "Despite this, lightweight materials like aluminum have been curbed in many car designs because they are too expensive." Sloane discussed opportunities for materials researchers in the automotive market at the Materials Research Society 1998 Fall Meeting (Boston; Nov. 30-Dec. 4, 1998).

Troubles With Aluminum
Despite the cost, Audi has created an all-aluminum car called the A8. In 1999, the A8 will be augmented with aluminum running gear and revised damping characteristics. This should improve initial suspension response, ride quality, and dynamic handling, according to Audi representatives. A hollow-spoke system will also be used for the first time in the new cast aluminum wheels. The design is too expensive for Audi's bottom-end vehicles; to recoup the cost of the lightweight material, the company implemented the designs in one of its higher-end models, Sloane says.

The Audi A8—all aluminum

Approximately 250 pounds of aluminum is used in each vehicle produced by Ford Motor Co. (Dearborn, MI). Less expensive materials are currently being explored to replace heavier materials in Ford components. For example, the company has projected that the magnesium content in their cars will grow from only five pounds per vehicle to approximately 250 pounds per vehicle over the next two decades.

Before lightweight materials can play this large of a role in car designs, materials researchers must solve a variety of problems that go far beyond the price tag. In many cases, sufficient testing has not been done to verify material impact resilience and long-term durability. Parts must be assembled with joints that have good structural integrity, and composites must fit into vehicle assembly processes.

Streamlined Assembly Process
Instead of building cars by assembling thousands of components with bolts and other fixatives, engineers are now compiling these minute pieces into a few manufactured components that can be assembled with just a few bolts. This technique improves the structural behavior of the car, reduces assembly cost, and improves the overall quality, as fewer mistakes are likely to be made when assembly is simplified. Some car bodies are now made of just 10 pieces, Sloane says, drastically reducing the scrap rate during manufacturing.

When all of the parts in the car are considered, this assembly process can add up to quite a bit of savings. According to a report by the Motor and Equipment Manufacturers Assoc., it takes approximately 3,800 different parts to build the average car. Since a car has more than one of each part—for example, a tire is one part, but a car has five tires—nearly 35,000 separate items are used to build each car. Reducing the number of individual parts can substantially drop the cost of each car and reduce the weight of the car body.

"Per pound, each vehicle is cheaper than a McDonald's quarter pounder," Sloane says. "Despite this, we are always in need of new ways to mold complex parts with high-performance characteristics so that we can reduce costs further."

Composites Pose Many Challenges
Although composites are a logical solution for replacing many of the heavy components in the car's design, they have to be modified to fit within the restraints of the large-scale manufacturing process. Composites used in automotive applications must be able to cure in less than five min., and must be both resilient and recyclable.

Surface chemistry is a key materials research issue when using composites. In order to join parts made of disparate materials, researchers must understand how their surfaces interact so that the parts can form long-lasting joints, even during inclement conditions. The problem presents a double-edged sword, because at the end of the car's life, manufacturers need to be able to separate the alloys so that car materials can be recycled.

Glass and other fibers used to reinforce composite materials can also pose a problem when they are used to strengthen molded composite parts. The orientation of the fibers, and therefore the tensile strength of the part, depends on the material flow direction and the mold shape. Developments are now underway at most car manufacturers to make lightweight composites strong across the entire part, Sloane says.

To improve available composites and speed their introduction into the manufacturing process, automotive companies have capitalized on research performed at government and university labs. In early November 1998, automotive companies joined forces with NASA and several DOE labs at the first Federal Laboratories Technology Exposition. Among the technologies explored in the conference were lightweight, heavy-duty materials used to build the Space Shuttle.

"Learning what the government has to offer will benefit both the government and Ford," says John McTague, vice president of technical affairs for Ford Motor Co. "Ultimately, many of the innovations from the federal labs may help us develop even safer and more environmentally friendly vehicles."

Automotive companies are making a serious investment in their research goals. According to DaimlerChrysler co-chairman Jürgen Schrempp in an announcement on Dec. 3, 1998, the company will have invested roughly $15 billion—or $40 million a day—in long-term investments such as research projects by the end of 1998.

Powertrain Design
One of the areas where automotive manufacturers have concentrated their efforts is in the powertrain design. Engineers are switching from mechanical to electrical systems, replacing gears with lightweight interconnects and wiring, and recreating drivetrain suspensions with newer, longer lasting catalytic converters, Sloane says. Alternatives are also being sought to replace the iron cores in aluminum engines with materials that provide the necessary strength without the added weight. Coatings are one of the options being explored as a strengthening agent for automotive components.

Coatings are also being used for car windows to reflect infrared heat in the summer months. This is crucial because each car can expend up to 8 kW of energy in the summer—twice the energy required to move the car—just to keep it cool. This is not as much of an issue in the winter, as the energy to heat each car is substantially less than the energy require to cool it, Sloane says.

Catalyst Improvements Needed
Car manufacturers are also researching ways to improve catalysts for reducing emissions. Hydrocarbons, carbon monoxide, and NOx need to be controlled to meet environmental regulations. "Most emissions occur in the first five minutes that you are in your car because the catalytic converter has to get hot," Sloane says. "If we move the converter closer to the engine, it heats faster, but the catalyst doesn't last as long because it is exposed to extreme temperature fluctuations."

Because automotive catalysts are usually made of expensive metals like platinum, it is too expensive to replace them frequently. Another option, placing a heater on the catalyst, makes the car more expensive and heavier, decreasing is fuel efficiency. A solution needs to be found soon, however. According to the new California environmental regulations, catalysts must soon convert 75% of NOx in the Los Angeles area to environmentally friendly gases. Currently, they can convert only 35% of the NOx that is released, Sloane says.

"The challenges here are driven mainly by the air-quality regulations in the United States," Sloane says. "What the automotive industry needs from the materials research community is a knowledge base. We need to transition information from science to engineering to make cars more environmentally friendly, yet affordable for consumers."