AK RIDGE, TN--The auto industry/federal government Partnership for a New Generation of Vehicles (PNGV) consortium--the crew in charge of producing, by 2004, a prototype 80-mpg (3L/100 km) km) family sedan--has been in existence for two-and-a-half years now. But before they even started, the auto industry engineers and government scientists assigned to design a 6-passenger vehicle that performs like today's cars, yet achieves roughly three times the fuel economy, knew the real bogey.
Weight is the ultimate enemy of just about anything automotive--or at least the enemy of any design that seeks efficiency. The 80 mpg target is going to require some serious efficiency.
That's why supercar development is biased so heavily toward weight reduction--the PNGV weight gurus, the automotive world's answer to Susan Powter, say they'll have to reduce the overall weight of today's vehicle by a stunning 40% to hit the bogie in 2004.
The job obviously calls out for new materials (see chart), most of which are far from common in current vehicle designs. Some, like aluminum and magnesium, play limited roles right now for some component and structural applications. others, particularly high-strength polymer composites, present more of a challenge because precious little is known about their applicability to automotive duty.
One further caveat: PNGV has made the project extra-tough because they've deemed that the "supercar" also must be no more expensive in the year 2000-something than today's typical family sedan. Many supercar-friendly advanced materials could be employed right now--if we didn't mind Luminas priced like Bentleys.
A look at some of PNGV's favored materials:
* Aluminum. Advantages: Can be much lighter than steel. Good strength-to-weight ratio. Certain alloys make excellent body panels. Disadvantages: Energy-intensive to produce. Not always easy to shape. More expensive to produce and fabricate. Automotive repair-industry infrastructure is almost nonexistent.
The aluminum industry and the steel-producing industry repeatedly have sniped at one another in some forums, but in the PNGV program differences are forgotten. Colonels from both camps admit the best PNGV-type vehicle probably will use both to their best advantages.
One PNGV source says privately that some factions in the aluminum industry recently have conceded they may find methods to reduce the price of the base feed-stock, something the aluminum cadre up to now has said couldn't be done. If it happens, aluminum may close its cost deficit to steel.
Moreover, the industry is reducing the cost of making aluminum. Says Bill Steuf ofMotor Co.'s Materials Technology Team, "If you look at the energy it takes to make an aluminum car versus the energy it saves over its lifetime, the aluminum car wins hands down." He says the kilowatthours needed to produce aluminum have been reduced by about 40%.
At the oak Ridge National Laboratory (ORNL) here, government scientists and engineers are focused on ways to reduce the cost of producing aluminum, as well as methods to make it more appropriate to volume production. They are working to adapt production processes such as metal compression forming, contour roll forming and slab casting to aluminum's unique requirements. And a Cooperative Research and Development Agreement (CRADA) has scientists here studying various alloys to develop optimized aluminum sheet for stamping.
Meanwhile, the Aluminum Association's Mike Wheeler says that if we're thinking "supercar" to forget currently produced limited-volume aluminum cars that rely on skeleton frames overlaid with aluminum body panels: "In general, a volume-produced aluminum car will be a unitized (body) car," he says.
Currently, there are nine production cars that have one or more aluminum closure panels. A total industry count finds 14 aluminum panels in use.
* Steel: Advantages: Known quantity. Good strength-to-cost ratio. Relatively easy to fabricate. Solid repair infrastructure. Easily and cheaply recycled. Disadvantages: Heavy compared with other alternative materials. Low-volume tooling is costly. Low-tech reputation.
But Darryl Martin of the American Iron and Steel Institute (AISI) says that we've tapped only 20% of steel's potential. In short, steel is waking up for the '90s.
Consider projects such as the Auto/Steel Partnership. Twelve North American steelmakers have teamed with the Big Three in this program to advance steel's potential. They're into big-league ideas like standardizing tooling, hydroforming steel parts and laser-welding techniques. The Partnership's work dovetails beautifully with PNGV's need to reduce all costs, including those in the manufacturing sector.
In fact, Bill Miller ofCorp.'s Materials Technology Team says the AISI's ballyhooed Ultra-Light Steel Auto Body (ULSAB) project should be finished sometime late next year. He claims the ULSAB is showing a titanic 51 Hz natural frequency, weighs just 452 lbs. 205 kg) and costs $154 less than a current all-steel body-in-white.
Mr. Miller admits, however, that the PNGV weight-saving goals will not be met by steel alone; other materials like aluminum, magnesium and composites must be utilized to rip the 1,200 lbs. (545 kg) from today's pudgy family sedans and morph them into supercars.
* Composites. Advantages: Extremely lightweight. Can allow for considerable parts consolidation. Disadvantages: Not enough performance, durability data. Quick volume production currently impossible. Bonding and joining techniques need study. Some are hugely expensive.
Composites (mostly some type of plastic or fiber material) represent an enormous potential for weight reduction. The problem, however, is that not much is known about how they'll work out for major automotive components and body panels.
Researchers at ORNL currently are studying the reliability and durability characteristics of many composite materials. Initial results look promising, but realworld use of composites is still decades behind the understanding we have compiled about today's more commonly used automotive materials.
The question of how to adequately join composites to one another, or to different materials, is another bugaboo. PNGV researchers have determined that developing reliable, high-strength adhesives is crucial if composite materials are to be reliably used in the high-stress, harsh environments to which most automobile components are subjected. Computer models have been employed to predict the strength of bonded joints, and new techniques for improved surface preparation are under way.