BOX 4-1: Four Weight ReductionAbout 70 percent of today’s passenger car is comprised
body (25 to 28 percent), and the largest iron component
Scenarios for a Mid-Size Carof iron and steel. The largest steel component is the
is the engine (12 to 15 percent). A typical material
composition of a mid-size passenger car would be 55 percent steel, 15 percent iron, 5 percent aluminum, 8 percent
plastics, and 17 percent other. Substitutions of lightweight materials for iron and steel yield a primary weight
savings plus a secondary weight savings derived from downsizing of supporting components, engine size reduction,
and so forth. For vehicles that are completely redesigned (that is, all but the 2005 “optimistic” vehicle) a secondary
weight savings of 0.5 pounds per pound of primary weight is assumed for equal performance. For the 2005
“optimistic scenario” vehicle, a secondary weight savings of 0.25 pounds per primary pound is assumed.
For the 2005(m) scenario, the vehicle is an optimized steel design that has an aluminum engine. Because of the
automakers familiarity with steel auto manufacture, it is assumed that 10 years is long enough to implement a
complete vehicle redesign. Through a clean sheet design approach with high-strength steels and advanced
manufacturing processes, curb weight is reduced 11 percent, with an additional 4 percent reduction from the
aluminum engine, for a total of 15 percent, compared with an unsubstituted baseline. Composition changes to:
steel, 51 percent; iron, 8 percent; aluminum, 12 percent; plastic, 10 percent; and other, 19 percent. The estimated
cost increase of $200 to $400 for the intermediate sedan is scaled according to weight for the other size classes.
For the 2005 optimistic scenario, the vehicles have an aluminum-intensive body and an aluminum engine.
However, it is assumed that by 2005, there is insufficient time to solve all of the design and manufacturing issues
associated with a clean sheet aluminum design with maximum substitution and full secondary weight reductions. A
20 percent weight reduction below baseline is achieved assuming secondary weight savings of 0.25 pounds per
pound of primary weight. Composition changes to: steel, 29 percent; iron, 8 percent; aluminum, 31 percent; plastic,
12 percent; and other, 20 percent. The cost increase is estimated at $1,500 for the intermediate sedan and scaled
according to weight for the other size classes.
In the 2015(m) scenario, the vehicle has maximum use of aluminum with a clean sheet design. Curb weight
savings over the baseline are 30 percent. Composition shifts to: steel, 16 percent; iron, 1 percent; aluminum, 43
percent; plastic, 15 percent; and other, 25 percent. The cost increase for the intermediate sedan is estimated at
$1,200 to $1,500, and this figure is scaled by weight to yield the cost increases for the other size classes. Although
the vehicle contains more aluminum than the 2005 vehicle, which will tend to raise costs, the cost increase is about
the same as in 2005, due to increased manufacturing experience with aluminum and the advantage of a clean sheet
design to take advantage of the properties of aluminum.
In the 2015(0) scenario, the vehicles have a carbon fiber composite structure with aluminum engine and
appropriate secondary weight savings that yield 40 percent reduction in curb weight compared with today’s
baseline. Composition changes to: steel, 15 percent; iron, 1 percent; composite, 22 percent; aluminum, 19 percent;
plastic, 16 percent; other, 27 percent. The cost increase is estimated at $2,000 to $8,000 for the intermediate
sedan, and this range is scaled by weight for the other size classes. The weight breakdown for an intermediate size
vehicle by material is shown in the table below..
Material Weight Distribution for Lightweight Mid-Size Cars, Model Years 2005 and 2015steel
Iron
Aluminum
Plastic
Other
Carbon fiber2005(m) 2005(o) 2015(m) 2015(o)
1,838 775 366 294
501 214 23 20
167 829 984 373
211 321 343 314
401 535 572 529
~0 -Q ~0 431SOURCE: Office of Technology Assessment, 1995.