Influence of the filler content on the thermal expansion behavior of an epoxy matrix particulate composite

The thermal expansion behavior of epoxy matrix particulate composites prepared with different volumetric filler contents (ϕ) up to 25 vol.% was studied. Using a very simple absolute optical dilatometer developed in our laboratory, the coefficients of thermal expansion (CTE) for pure epoxy resin matrix and the composites in the glassy and rubbery states (293 K ≤ T ≤ 493 K) were obtained. For the matrix, the CTE obtained in the two states are in good agreement with those reported. For composites the results are discussed into the frame of different approaches using well-known mechanical models. In the glassy state, the CTE behavior could be well described by the upper bound of the Hashin–Shtrikman model. In the rubbery state it was necessary to evaluate the contribution of the average volume of nanoholes in the epoxy matrix as a consequence of the addition of particles. To this aim, using positron annihilation lifetime spectroscopy, the dependence of the average volume of nanoholes with ϕ was measured.