SRIM BUMPER BEAMS ARE MANUFACTURED using a modified RIM molding process whereby a fiberglass preform is made and placed in a molding tool into which a thermoset polyurethane resin is injected to mold the part. Two types of preforms are used in SRIM: mat preforms and directed chopped fiber (DF) preforms. Mat preforms are made from multiple layers of fiberglass mat reinforcement, while DF preforms are made by sprayed fiberglass roving. The most common mat reinforcement used is Fabmat chopped strand mat/woven roving combination. Several plies of the combination mat are heated with infrared heaters to soften its thermoplastic binder. The mat is then transferred to a preforming tool which forms the fiberglas reinforcement to the dimensions of the part and cools it to solidify the binder. Typically, mat preforms can be made at a rate of one per minute. DF preforms are made by chopping fiberglass roving and spraying it with a binder onto a part-shaped screen. Air is drawn through the porous screen by a large blower to conform the rovings to the screen surface. When sufficient roving has been applied to the screen, the screen is transferred to an oven, which sets the binder. After the screen is removed from the oven, air is drawn through the preform to cool it. Finally, the preform is removed from the screen and the process can begin again. With a multi-station machine, DF preforms can also be made at a rate of one per minute. This paper describes the advantages of the DF preform/IMR SRIM process for the design and production of automotive bumper beams with particular emphasis on the design freedom afforded by DF preforms and SRIM and potential material cost savings compared to competitive bumper beam materials and production processes. An analysis of the property performances of DF preform SRIM composites is presented and compared with competitive materials.
SRIM bumpers molded with internal mold release and directed fiber preforms
Reaktionsspritzgegossene Stoßdämpfer durch Formprozeß mit internem Formtrennmittel und vorgeformter Faserverstärkung
1992
4 Seiten, 4 Tabellen, 7 Quellen
Aufsatz (Konferenz)
Englisch
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