sand/unsaturated polyester composites, 50/50 composition by weight, were prepared from sand treated with different silane solutions. n-2-aminoethyl-3-aminopropyltrimethoxy silane (a0700) and 3-aminopropyltriethoxy silane (a0750) were used. water and styrene solutions were employed to treat the sand. it was found that a0750 in styrene produced better composites than other surface treatments as the interfacial bond was improved, the tensile strength and the tensile modulus increased whereas the strain to failure decreased the acoustic emission data was a function of the sand surface treatment where a better interfacial bond resulted in more acoustic activity. dynamic mechanical analysis showed that the interfacial bond affects the dynamic shear modulus, the loss shear modulus, and the damping of the sand-filled composites. the glass transition temperature (t//g) of the composite was also affected by the surface treatment. the thermogravimetric analysis did not show a well-defined trend between the decomposition temperature and the surface treatment. (author abstract) 23 refs