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CALM study highlights possibilities of mixed-material for mass reduction

The CAR’s (Center for Automotive Research) Coalition for Automotive Lightweighting Materials (CALM) is a collaboration of more than thirty industry organizations working to support the cost-effective integration of mixed materials to achieve significant reductions in mass through the joint efforts of the material sectors and the auto manufacturers.

CAR has just published the results of a CALM co-development lightweighting study using a roof structure. The baseline vehicle for this research is the 2011 Honda Accord which has a mild steel roof structure. The design space contains twelve parts including the roof panel, roof bows, roof rails, and the headers.


The CALM team compared three lightweighting concepts were compared to the 2011 Honda Accord roof in mild steel as the baseline.

  • With the latest generation steels, the mass reduction was 22%.

  • With a mix of steel, aluminum and composites, the mass reduction was 39%.

  • An all-composite design reduced the mass by 40%.


Secondary mass reduction can be achieved by optimizing other parts and systems such as tires, wheels, powertrain, suspension system, braking system, bumpers, fuel and exhaust systems, steering system, and electrical systems and wiring.

Future research could include an all-aluminum design, side impact analysis, and a moon roof design.



There are no real technical reasons, not to reduce total vehicle weight, with new lighter materials, from current 4000 lbs to 2000 lbs, while maintaining the equivalent interior space and comfort. This could reduce the energy required and the pollution/GHGs created to drive from A to Z by 50+ % and be specially beneficial to electrified extended range vehicles.

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