Thermal and cure analysis in sheet molding compound compression molds

Abstract

AbstractSheet molding compound (SMC) compression molding growth will benefit from faster cycles and more uniform cure so as to reduce in‐plane thermal residual stress and resulting warpage in the molded part. These improvements require an in‐depth study of the mold thermal design. Here we use a finite element model to analyze the quasi‐steady temperature distribution in a plane perpendicular to the heating channels of a representative mold, and a finite difference model to investigate the cure dynamics at critical regions. Several changes in the mold heating system and operating conditions were considered and their effects on the temperature distribution and cure time were studied. It was assumed that the steam condensate is well drained and enough steam is supplied so that the steam tube walls are kept at a constant temperature. An important conclusion of the present study is that better insulation of the mold from the press does not help much in improving the uniformity of cavity surface temperature or cure. It was also found that reducing the distance between two consecutive steam tubes beyond the distance from the steam tube to cavity surface will not yield a significant change. The most practical way to give both more uniform cavity surface temperature and faster cure is to have higher steam temperature for the region where the charge is initially placed.