while the composites collapse by a combination of fracture processes. Whereas metals are
isotropic^19 and comparatively easy to model, composites are internally much more complex,
involving a wide range of resins, fibers, fiber orientations, and manufacturing processes, and,
consequently, are much harder to model.^20 Thus far, an understanding of the mechanisms
responsible for energy absorption in composites and a methodology for its quantitative prediction
have yet to be developed. Theoretical studies, laboratory, component, and fill vehicle crash
testing will be required to complete the necessary development work. Finally, appropriate repair
strategies and techniques for crash-damaged composite structures, while familiar in the context of
advanced aircraft, have yet to be worked out in the automotive industry.
The lack of experience of automotive designers with the crash behavior of aluminum and
composites remains a significant barrier to their use, particularly for composites. This, combined
with unresolved manufacturing issues with these materials, is the principal reason that OTA
projects that mass production of aluminum-intensive vehicles will not begin before approximately
2005, and composite vehicles before approximately 2015 (see the discussion of materials use
scenarios below).Recyclability
The ultimate disposition of vehicle materials is becoming an increasingly important
consideration for vehicle designers. In Germany, for example, legislation is pending that would
make auto manufacturers responsible for recovering and recycling vehicles, similar to legislation
already passed for the recovery and recycling of product packaging. The prospect of this
legislation has already stimulated German car companies to consider changes in design strategies
such as reducing the number of different kinds of plastics used in the vehicle and “design for
disassembly” to facilitate the cost-effective removal of parts from junked vehicles for recycling.^21
Anticipating that this type of regulation may be coming in the United States, the Big Three and
their suppliers have formed a consortium under the auspices of the U.S. Council for Automotive
Research (USCAR) called the Vehicle Recycling Partnership to address the recycling issue.Currently, 25 percent of the weight of a vehicle (consisting of one-third plastics--typically
about 220 pounds of 20 different types--one-third rubber and other elastomers, and one-third
glass, fabric, and fluids) cannot be recycled and generally is landfilled. In the United States, this
automotive residue amounts to about 1.5 percent of total municipal solid waste. Sometimes the
residue is contaminated by heavy metals and oils or other hazardous materials.Most of the concern about auto recycling focuses on the quantity of this residue, specifically
the amount of plastics on vehicles. In the quest for increasing fuel efficiency in the 1970s and early
1980s, the plastic content of cars did increase slowly as lighter weight plastics were substituted
for metals. In the future, the trend toward increasing use of plastics is expected to continue. With
current recycling technology and economics, this will lead to increasing amounts of solid waste(^19) Isotropic means that the physical properties are the same in all directions.
(^20) Additional variables that can affect their crush behavior include laminatedesign, impact rate,temperature and environmental effects, angular
and bending loads, and void content. 21
U.S. Congress, Office of TechnologyAssessment Green Products by Design: Choices for a Cleaner Environment, OTA-E-541 (Washington
DC: U.S. Government Printing Office, October, 1992), p. 59.