As for alternatives to aluminum, some here say carbon fiber – strong, light and corrosion-resistant – is declining in price, but still is too expensive to be a viable alternative to steel.

Even early adopter BMW, which operates with supplier SGL a carbon fiber plant in Moses Lake, WA, to supply the i3 and i8 electric cars, has limited use of the material in some of its redesigned, higher-volume models, including the 5-Series, to increase their profitability.

BMW’s Florian Schek, head of lightweight design and vehicle weight, told an industry conference in August: “The cost (of carbon fiber) is still too high, and it’s a difficult technology.”

However, Ducker’s Abraham notes the cost of carbon-fiber composites is coming down, now 16 times the price of steel compared with 60 times the price of steel for aerospace grades of carbon fiber.

Aluminum as well as magnesium is seeing increased use in die-cast parts, says Morgans, who notes die-casting is an increasingly popular means to reduce the number of pieces in a given part.

Through use of die-casting, shock towers, typically multi-piece stamped designs, can be made singular.

Die-casting shock towers “offers a lot of advantages,” he says. “You get rid of all the joints, you get rid of any redundant material. And the other thing the casting allows is, you can tune that part in by putting ribs where you need it. And again you’ve got more control over the thickness and variation in your walls as opposed to stampings.”

Despite the growing popularity of new materials, steel continues to make up the vast majority of body and frame content.

“We’ll continue to build steel vehicles. I do not doubt that at all,” says Morgans, noting Ford is seeking the strongest grades of materials it can find.

Blake Zuidema, director-automotive products application for ArcelorMittal, promotes third-generation steels, such as his company’s Fortiform ultra-high-strength steel, as having the lighter weight and higher ductility automakers and suppliers want.

“The third-generation steels, whether it’s the Fortiform or the Fortiform S, provide a lot more ductility at a similar strength level (to second-generation steels),” he says. Fortiform S is in development at ArcelorMittal and has more ductility, the ability to stretch without breaking, than do traditional dual-phase steels.

Using the example of a front-motor compartment rail, Zuidema says third-generation steel can reduce weight about 10% but maintain the same level of formability.

Front rails and rear rails, which must absorb energy in front and rear collisions, as well as rockers and lower parts of B-pillars, which need to deform in side impacts, are the likely first candidates for third-gen steel, he says, adding some rear roof rails also could be candidates.

Beyond the usual suspects, Abraham says glass/glazing, coatings and interior components are the next areas from which weight will have to be removed.

The panelists say neither the midterm review of the 2025 CAFE standard nor the predicted coming of autonomous vehicles are derailing their march toward developing lighter, more efficient vehicles.

On the topic of CAFE, all say any possible change as a result of the midterm review, expected to be completed in April, is irrelevant given even developing countries, such as India, are toughening fuel-economy and emissions standards.

“I don’t think it really changes what we do,” Morgans says. “We’re producing vehicles for the global market. A lot of those vehicles get produced in the same plants. To manage the complexity that would be introduced if we did a different vehicle for each market, it’s too cumbersome to deal with.”

Zuidema agrees, adding the challenges of lightweighting are going on unmitigated around the world. “Frankly, we’re not really changing our strategy on the basis of the outcome (of the review),” he says.

Zuidema also says he is unconvinced autonomy will bring about accident-free transportation and therefore believes steel will be necessary to maintain the crashworthiness of the vehicle body.

“If you drive in Michigan in the winter time, you know all the sensors in the world don’t work if they’re covered with snow. All of the equipment in the world doesn’t help when the roads turn to ice.

“So in these situations, where technology is going to completely fail, you want a safe car,” he continues. “The crashworthiness has to be there, and under those circumstances all of the requirements of today are still going to be there in the foreseeable future.”

Stiffness will become more critical in later generations of autonomous vehicles, he says, as some models may use suicide doors that necessitate removal of the B-pillar.