USCAR Consortium Successfully Demonstrates SRIM Technology

    Process is cost-effective and efficient; pickup box 25 percent lighter
                                  than steel

    SOUTHFIELD, Mich., May 29 The United States Council for
Automotive Research (USCAR) has demonstrated the capability to mold large
structural reaction injection molded (SRIM) parts through the work of the
Automotive Composite Consortium (ACC).
    SRIM is a promising process for the manufacture of composite structures
that have a high degree of part consolidation, improving cost-effectiveness
relative to stamped metal structures.  In this process, a glass fiber preform
is placed in a matched metal mold and low viscosity resin is rapidly injected.
The resin quickly impregnates the fibers and rapidly crosslinks to form the
rigid polymer matrix.
    The use of structural polymer composites in cars and trucks can
significantly reduce vehicle mass and thus decrease fuel consumption.
However, the industry has historically been limited in its ability to cost-
effectively manufacture large structural parts in high volume.  According to
Program Manager Doug Denton of DaimlerChrysler, "This technology can be very
beneficial in the effort to reduce the weight of vehicles, but the cost has
been prohibitive.  The goal of this program was to address issues -- like cost
-- that have been associated with the production of large SRIM structural
composite parts."
    The project showed the feasibility of producing parts at a relatively
rapid rate that meet performance criteria and saves weight, while costing no
more than a steel structure.  Use of a fully-automated, robotic process, P4,
produced consistent net-shape, net-size chopped glass fiber preforms and
achieved high material usage rates and lower cost.  The production quality
mold was designed with shear edges to allow use of an injection-compression
process and production of net-edge parts requiring minimal trimming.  The mold
incorporated a vacuum to assist in mold filling and fiber wetting.  The use of
real-time monitoring equipment helped define and optimize molding process
parameters.
    The structural inner of a pickup truck box was selected as the primary
demonstration part.  A cost model was developed to assess the cost of the
composite box assembly relative to a steel assembly using similar production
scenarios.  The cost model indicated an SRIM composite pickup box can be cost
competitive at annual volumes of up to 50,000 units.
    Researchers demonstrated the feasibility of achieving a four-minute
production rate for the pickup box.  The box meets performance requirements
and weighs 25 percent less than a corresponding steel structure.  "ACC, with
the help of our supplier partners, met the goals of the SRIM project and
advanced the state of high-volume, low-cost liquid composite molding for use
in the automotive industry," Denton said.
    Key among the development accomplishments was advancement of P4 as a means
to reliably produce net-shape, net-size random chopped fiber preforms.
Manufacturing advancements were made in SRIM for the production of large
structures and cored parts.  Technology was also developed in the durability
characterization of polymer composites, adhesive materials, and NDT methods.
    ACC functions under the umbrella of USCAR -- a cooperative of
DaimlerChrysler, Ford and GM established in 1992.  The purpose of USCAR is to
assist the domestic auto industry in facilitating pre-competitive research.