When the federal government announced new Corporate Average Fuel Economy (CAFE) standards mandating a fleet average of 54.5 miles per gallon by 2025, automakers rushed to explore new materials and technology to reduce vehicle mass to boost fuel economy. Two materials, aluminum and high-strength steel, are key contenders to reduce weight in the vehicle's body-in-white, the heaviest component.
Ronald Krupitzer of the American Iron and Steel Institute believes the new high-strength steel products that have become available since 2000 are the material of choice for achieving vehicle mass reduction while maintaining strength and cost savings. He notes that automakers have a 100-year history with steel vehicle components, pointing out that about 60% of an average vehicle's weight is made up of steel in one form or another. Krupitzer also notes steel's relative low cost compared to aluminum: Using high strength steel for the body-in-white will achieve of cost savings of between $600-$1000 over aluminum.
A recent study by FutureSteelVehicle showed that using new steel components, vehicles could achieve a 35% reduction in vehicle mass while still meeting global crash and durability requirements to enable a five-star safety rating. In addition, the study found that new steel technologies reduced the total lifecycle emissions by 70%. The FSV study incorporated 20 new AHSS steel grades that will be commercially available starting in 2015. These include dual-phase (DP), transformation-induced plasticity (TRIP), and complex phase (CP) and hot-formed (HF) steels that boast GigaPascal strength. These new products are used in nontraditional places, such as the shotgun, front rail and rocker subsystems to achieve maximum efficiency and mass reduction.
This future of automobile manufacture could lie in the use of different, lightweight materials.
Randall Scheps, director of ground transportation at Alcoa, believes automakers will turn to aluminum to achieve maximum vehicle mass reduction to comply with CAFE. "It performs as well as steel, and it absorbs twice the crash energy per pound," he said, adding that aluminum was superior in braking and corrosion resistance.
Scheps pointed to a study by the University of Aachen in Germany. Researchers found that using aluminum components could achieve a vehicle weight reduction of 40%, potentially achieving a 525 pound savings leading to as much as 2.7 miles per gallon improved fuel efficiency. The study also found that aluminum has the smallest carbon footprint over the production lifecycle, road use and recycling stages. Scheps acknowledges that aluminum is more costly upfront, but believes the design flexibility, fuel and weight savings offset the costs.
While the best material choice for achieving vehicle mass reduction is unclear at this point, what is clear is that automakers will be investing in creative uses of alternative materials to achieve the tough new CAFE standards of 2025.
Further Reading: Automobiles for lightweight cars, Greencar Congress, Future Steel Vehicle, Materials lead the way to vehicle mass reduction
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