EFFECT OF DEFORMATION AND THERMOSET CURE ON HEAT-CONDUCTION IN A CHOPPED-FIBER REINFORCED POLYESTER DURING COMPRESSION MOLDING

This paper concerns heat conduction in a chopped-fiber reinforced polyester resin during compression molding of thin sheet-like parts. Since the resin generates heat as it cures, the general boundary value problem involves a deforming heat conductor which reacts chemically. The randomly woven fiber structure in the sheet molding compound (SMC) motivates a kinematical assumption on the material deformation in the mold cavity. The resulting description of the deformation field is then used to formulate a boundary value problem for the temperature distribution in the deforming SMC in terms of coordinates that move with the material. From the solution to this problem we derive a general expression in closed form for the nonuniform distribution of heat energy absorbed from the mold surface as each part is molded. The exothermic cure reaction in the polyester resin, which begins after the mold closes, is characterized in terms of heat generated in the SMC. Numerical analysis of the transient distribution of temperature and cure shows how the degree of coupling between heat conduction and cure depends on the thickness of the molded sheet. The results of the analysis also determine the effect of sheet thickness and mold temperature on cure time, subject to limitations of thermal degradation. © 1979.