Dynamic Mechanical Characterization of Fiber Filled Unsaturated Polyester Composites

Abstract

Dynamic mechanical testing was used to qualitatively study the effects of various constituents of sheet molding compound (SMC) and bulk molding compound (BMC) materials, including unsaturated polyester resin, a chemical thickener (magnesium oxide), a filler (calcium carbonate), and glass fibers. Tests were designed to evaluate the influence of each constituent as it was added to the overall composition. The parameters tested were elastic shear modulus, viscous shear modulus, and complex viscosity as functions of frequency for non-cross-linked materials, and elastic shear modulus, viscous shear modulus, and damping as functions of temperature for cross-linked materials. The chemical thickener was observed to change the molecular weight of the polyester resin, as indicated by the appearance of a rubbery plateau in the viscoelastic spectrum, while cross-linking, filler, and glass fibers were observed to contribute heavily to the elastic shear modulus and temperature sensitivity.