Machine Design

Manufacturing costs keep composites out of cars, despite the weight savings

LUX Research Inc.

The primary factor that will drive the automotive sector to adopt composite materials will be lower costs, not weight savings that increase mileage, according to a recent report from Lux Research Inc., Boston.

Chasing cars: Can composites catch up to steel? analyzes surveys from automakers and composite-material suppliers. It explores what would impede or advance the adoption of new materials, examines composites’ potential to replace metals in cars, and identifies early-stage technologies that could change how composites perform.

“The conventional wisdom that says automakers will adopt composites solely for weight reduction misses the mark,” says lead author David Hwang. “In reality, composites will be used when they help cut manufacturing costs, such as in low-volume production and electric vehicles.”

The report notes that automakers can also boost efficiency less expensively by improving powertrains. For instance, adding turbochargers or switching to a gas/electric hybrid improves fuel efficiency by up to 50%. Automakers can adopt these changes without significantly altering production methods and supply chains, comso these changes cost less than switching to composites.

And while composites are usually touted as having higher strength-to-weight ratios than steel, automakers can get similar weight savings by switching from standard steels to other metals. Aluminum, for example, is lighter than steel and replaces it in many auto parts. And ultrahigh-strength steels can support as much or more than standard steel.

However, these factors don’t mean there’s no future for composites in automotive manufacturing. At low-production volumes, it can be cheaper if several steel parts are consolidated into a single, complex, nonstructural or semistructural composite part that couldn’t be made from metal.

Composites in the form of sheet-molding compound — mats of random fibers impregnated with resin that easily form to contours — can work at higher production rates in applications such as body panels.

Advanced material technologies that may help composites pull ahead in the future include nanoparticle additives, high-throughput structural-component molding, and bio-based materials, all of which are currently under development.

© 2011 Penton Media, Inc.

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