Dissolution of Voids during Compression Molding of SMC

ABSTRACT: During compression molding of sheet molding compounds air bubbles are formed that can deteriorate several properties of the final composite. The story of such bubbles is directly set by the local pressure distribution during pressing. A number of experiments have therefore been performed in order to derive the relation between the pressure and dissolution rate of some gases into relevant resins. The experimental results follow Henry’s law up to a pressure of 0.7MPa and the rate of dissolution is highest for CO2 in pure polyester. When applying the results to the process in focus it is found that even large bubbles can be dissolved into the liquid resin during manufacturing. Hence, there is a potential to produce parts with very low void content