Structure and Thermo-Elastic Properties of SMC

Abstract

A calculation process was developed to determine the whole set (in-plane as well as in the cross direction) of thermo-elastic properties of SMC materials on the basis of known properties of components. A typical feature of SMC structure (that the ma jority of reinforcing fibres remain collected in bundles acting as a sieve during the wetting process) is discussed. SMC-composite is held for a transverse isotropic material and is modeled by a symmetric three-layer composite with the centre layer consisting of plane isotropically reinforced fibre composite and the border layers represented by the isotropic particulate composite. The classical laminate theory is used to find the effective deforma tion characteristics of SMC. The properties of the centre layer are expressed in terms of a UD composite. The Kerner-Hashin theory has been proven satisfactory for prediction of particle composite properties in the case when the particle form doesn't differ too much from the spherical one (e.g., the case of a CaCO3 filler). The application of the Lewis-Nielsen theory allows a good agreement between theoretical and experimental values when platelet particle form must be considered (the case of a kaolin filler). An application of a low-profile additive reduces the stiffness of the resin and enhances its thermal expansion. This effect was found especially significant at higher temperatures and could not be described by means of a mechanical model only.