In search of the lightweight, multi-material car

  • 16-Sep-2014 09:14 EDT
2015-Chevrolet-CorvetteZ06-002.jpg

The auto industry is in overdrive to meet a U.S. 54.5-mpg fleet average mandate in 2025. Lightweight materials are key to achieving higher fuel economy numbers. The 2015 Chevrolet Corvette Z06 (shown) has a standard carbon-fiber hood.


Automotive researchers and engineers are looking for ways to knock the fat off nearly every part of a vehicle in their efforts to achieve higher fuel economy.

“Target the things that are—for lack of a better term—deadweight because these are the things that drive mass into other subsystems,” said Dr. Paul Krajewski, Global Manager and Technical Fellow for Vehicle Mass Integration and Strategy at General Motors.

Krajewski and other industry experts addressed the topic of “Lightweighting and the Multi-Material Car” during an executive panel session at the 2014 Society of Plastics Engineers Automotive Composites Conference & Exhibition in Novi, MI.

Closure panels meet Krajewski’s deadweight designation. “Whatever material you use for door panels, the body should carry those loads. Ideally, get the deadweight first because that allows you to hit everything else strategically,” he said.

Over the next decade, vehicles will get lighter on route to reaching stricter global fuel economy and emissions requirements.

Panel moderator Jay Baron, PhD, President and CEO of the Center for Automotive Research, said cars are going to be 10-15% lighter by 2025 in comparison to a 2010 baseline. “And that 10-15% represents several hundred pounds. So that’s a big deal, especially when you look at history. We’ve been adding weight to cars for the last 25 years, every year incrementally. We are clearly at a tipping point,” he said.

An important conduit for engineering lightweight vehicles are the tools to model the various material choices.

Said Krajewski, “If there isn’t a good material model, over-design can occur. When we were sourcing the composite parts for the new Corvette, it was difficult to get a very good apples to apples comparison. Each supplier had a slightly different process and a different material. That made it challenging to be able to predict and optimize early on,” he said. “This emphasizes the need for standard material formulations and specifications in the composites industry.”

The 2015 full-size Ford F-150 marks the first time a high-volume pickup truck will use aluminum for exterior panels.

Peter Friedman, PhD and Ford Motor Co.’s Manager of Manufacturing Research Development, said, “With the new F-150, we decided very early on that we were going to use lightweighting as an enabler to deliver both fuel economy and performance. The 2015 F-150 is aluminum-intensive in the front end, the cab, and the box, and the frame is steel with three times the amount of high-strength steel compared to the outgoing model.”

(See http://articles.sae.org/12724/ and http://magazine.sae.org/14autp09/ for more on the F-150.)

Thomas Pilette, Global Vice President of Product and Process Development at Magna Exteriors, said multiple considerations factor into a material usage decision. “We’re very well aware of low-cost materials. But what we’re trying to mirror is the performance, cycle time, and part quality expectations out of a single set of tools. So it’s really balancing material, process, and performance with the understanding that nobody wants to pay more than the current material and the current process,” he said.

Paybacks are proving to be one of the outcomes of industry collaboration.

“The steel industry saw the headwinds of the lightweight materials coming and has done a really good job of buttoning down, aligning and working together through the Auto/Steel Partnership. That’s led to some great design solutions and development of new materials,” said Krajewski.

According to Pilette, the automotive industry needs to underscore the concept of reinvention. “We have to make sure that we keep sharpening our advanced development techniques and make sure that we have the right material and process applications,” he said.

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