The dynamic mechanical properties of epoxy composites filled with different amounts of quartz powder were investigated. The storage modulus and loss tangent were measured at frequencies between 7.8 and 323 Hz from room temperature up to 460 K. The influence of the filler content on the temperature and frequency behavior of the dynamic mechanical properties is discussed and explained in terms of models presented in the literature. In particular, the dependence of the composite damping with the quartz content is explained with regard to damping due to particle-particle and polymer-particle interaction. Also, the glass-transition temperature as a function of filler content was obtained and was related to the results obtained for the apparent activation energies of the alpha relaxation, which were estimated with the Williams, Landel, and Ferry equation. (C) 2003 Wiley Periodicals, Inc.