and other components. The materials technical team has estimated that each 1.0 lb of primary weight reduction may enable 1.0 to 1.5 lb of secondary weight reduction, provided that the entire vehicle can be redesigned to capture this opportunity. Nevertheless, large-scale weight reduction is an extremely challenging task, particularly since the addition of enhanced fuel-efficiency systems such as electrification results in the opposite effect, namely, mass compounding.
Broadly speaking, there are three obstacles to achieving the Partnership’s stated stretch goals regarding vehicle weight: increasing vehicle content, maintaining structural integrity, and managing cost.
• A 2011 Massachusetts Institute of Technology study (Zoepf, 2011) found that average passenger-car weight had increased by greater than 11 percent, or 160 kg, since 1990, despite the base car weight remaining unchanged. The entire weight increase was attributable to increasing comfort and convenience content and to added safety features and requirements. The pressure to keep adding feature content and more safety features will undoubtedly continue, in conflict with the need to reduce weight. Furthermore, the enhanced electrification of vehicles, while improving inherent fuel efficiency, adds considerable mass in batteries, motors, electronics, cooling, and so on, which must all be offset, including the mass compounding effect noted above, to yield the greatest fuel consumption benefits.
• Compliance with the full suite of Federal Motor Vehicle Safety Standards provides confidence in the overall safety performance of a vehicle, but it becomes increasingly challenging as weight is reduced. This has led to increased use of sophisticated structural analysis tools and demand for stronger, lighter materials such as high-strength steels and carbon fiber. This trend can only accelerate in the future.
• Cost is arguably the greatest challenge of the three: a detailed analysis in the NRC (2010) Phase 3 report illustrated both the high cost of weight reduction and the extent to which the reduction in fuel consumption can offset part of the cost to the ultimate consumer. However, the offset in fuel cost is only a fraction of the material cost penalty, and furthermore, much of the proverbial “low hanging fruit” has been harvested already.
In light of these challenges, having the Partnership’s activities focused as they are on enabling advanced high-strength lightweight materials and reducing their cost appears to be appropriate, even if the ultimate stretch goal is unrealistic.