1993-03-01

Flexible SMC for Vertical Body Panels: Two Approaches for Success 930465

Sheet molding compound (SMC) has long been the composite material of choice for horizontal automotive body panels. The excellent surface, dimensional stability and stiffness have made it preferred for hoods, deck lids and roofs. Softer thermoplastic and thermosetting (RIM) materials have been considered for fenders and occasionally doors, i.e., vertical body panels. However recent work has shown some performance problems with these materials and automobile companies are examining the low profile SMC alternative.
For fender applications increased flexibility over current horizontal body panel materials is desirable. Obtaining this flexibility can be readily achieved but usually at the expense of surface smoothness.
This paper reports on work done to achieve a Class A flexible SMC system for compression molding. Markedly greater flexibility of molded parts has been achieved by new combinations of low profile additive and unsaturated polyester resin technology. Discussions of surface and flexibility testing will be presented.

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