Plastic bumpers equipped with the soft fascia of polyurethane or polypropylene have recently become more popular. But almost all bumper beams, even in such the plastic bumpers, are generally made of steel today.
An approach to weight reduction is to make the bumper beam by the H-SMC, High-Strength Sheet Holding Compound. As a matrix for the H-SMC, we noticed the hybrid resin which was combined with the unsaturated polyester polyol and polyisocyanate, because it could produce cured system offering a vast improvement in toughness compared with the conventional unsaturated polyesters.
Such a bumper as assembled from a fascia, an energy absorbing foam and a bumper beam, which was molded from the H-SMC containing the hybrid resin as the matrix, passed the pendulum impact test at 5 mph according to F-MVSS part 581 and was lighter than the steel bumper beam.
The bumper beam fabricated from the hybrid resin H-SMC has been mounted on Mazda 323, Mazda 929 and Mazda RX-7.