NAIAS: Composite battery enclosure debuts on Chevy Spark EV

The redesigned Corvette and Silverado truck are the big newsmakers for Chevy at the North American International Auto Show (NAIAS), which began the second day of press previews at Cobo Center in Detroit today.

But the 2014 Spark EV, which had a limited release last year, is also important from a plastics technology perspective.

It features the first industry application of a VOC-free, seven-ply vinyl ester/rove cloth composite battery enclosure. Traditional materials that would have been used for the application, either steel of aluminum, were too heavy, according to Kestutis Sonta, a General Motors' materials engineer.  He estimates that the composite enclosure cut weight more than 40% compared to metal systems.

Selective pattern layups are used for localized reinforcement within the complex compression molded shape. The parts are produced by Continental Structural Plastics (Auburn Hills, MI) with vinyl ester resin supplied by Cytec.   The toolmaker is Century Mold and Tool (Elk Grove Village, IL).

Sonta said the composite technology is also being evaluated for other applications in the car such as load floors and structural components.

"The composite enclosure protects the major battery components in the event of a catastrophic event," said Sonta. "The enclosure is nonconductive in nature and protects the occupants and first responders to the accident scene."

The composite used in the Spark does not have the styrene emissions normally associated with SMC/BMC thermoset composite materials, according to Sonta.

"This application was heavily influenced by the USCAR Automotive Composites Consortium project for the Structural Composites Underbody, which allowed us to achieve rapid implementation."

GM says that the Spark EV achieves zero to sixty mph in less than 7.6 seconds, and has an estimated range of 82 miles. Mileage estimates are 126 mpg in the city and 109 mpg on the highway. Selling prices start at $27,495.

The production version of the Spark EV debuted at the 2012 Los Angeles Auto Show. It's the first all-electric passenger car sold by GM domestically since production halted on the EV1 in 1999. The Chevy Volt is a hybrid.

The enclosure was the Electrical Systems category winner in the 2013 Innovation Awards sponsored by the Society of Plastics Engineers Automotive Division.