The use of ionizing radiation in order to initiate polymerization of suitable monomers has found increased interest in the last two decades due to its several advantages. In this work, carbon fiber composites through gamma radiation polymerization of epoxy matrices have been produced for aerospace and advanced automotive applications. Composite samples were produced by irradiation at room temperature using different radiation doses and, as reference, thermal curing of the same epoxy resin formulations was also carried out. Furthermore, some irradiated samples were subjected to postirradiation thermal curing to complete the polymerization reactions. The properties of the cured materials were studied by dynamic mechanical thermal analysis and mechanical flexural tests. Also the effect of moisture absorption on the thermal properties was investigated. The results indicate that irradiation at room temperature gives rise to different cross-link densities of the epoxy matrix depending on the total absorbed dose. Postirradiation thermal treatment makes the materials more "homogeneous," resulting also in a higher glass transition temperature. Moreover, thermal analysis performed on irradiated samples, cut in both parallel and perpendicular directions to the fibers, has shown fiber-matrix interactions that are less intensive in comparison to thermally cured samples. The water absorption data show a plasticization effect of moisture on the epoxy matrix, causing a significant reduction of T-g. Flexural tests reveal a marked effect of postirradiation thermal curing on the less cross-linked samples, reflecting the higher efficiency of the thermal treatment on more mobile reactive species. (C) 2009 Wiley Periodicals, Inc. Adv Polym Techn 27: 163-171, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20127