STRUCTURE AND THERMOELASTIC PROPERTIES OF SMC

A calculation process was developed to determine the whole set (in-pla ne as well as in the cross direction) of thermo-elastic properties of SMC materials on the basis of known properties of components. A typica l feature of SMC structure (that the majority of reinforcing fibres re main collected in bundles acting as a sieve during the wetting process ) is discussed. SMC-composite is held for a transverse isotropic mater ial and is modeled by a symmetric three-layer composite with the centr e layer consisting of plane isotropically reinforced fibre composite a nd the border layers represented by the isotropic particulate composit e. The classical laminate theory is used to find the effective deforma tion characteristics of SMC. The properties of the centre layer are ex pressed 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 sphe rical one (e.g., the case of a CaCO3 filler). The application of the L ewis-Nielsen theory allows a good agreement between theoretical and ex perimental values when platelet particle form must be considered (the case of a kaolin filler). An application of a low-profile additive red uces the stiffness of the resin and enhances its thermal expansion. Th is effect was found especially significant at higher temperatures and could not be described by means of a mechanical model only.