Gamma Irradiation-Induced Modifications in the Tensile Properties of Epoxy Resins and Composites

Gamma irradiation is a powerful tool for modifying polymers, inducing either crosslinking or chain scission and thereby tailoring mechanical, thermal, and chemical properties. However, a systematic characterization of dose-dependent effects on tensile properties, especially across different epoxy chemistries, is still lacking. This study investigates the influence of gamma irradiation on the tensile properties of epoxy resins and fiber-reinforced composites. Dumbbell-shaped specimens of LZ resin composite, LY 556 resin, and LY 556 composite were irradiated with Co-60 gamma rays at doses from 0 to 220 kGy using a Gamma Cell 220, followed by tensile testing in accordance with ASTM D638. Results revealed distinct dose-dependent responses: LY 556 resin and its composite showed pronounced improvements, with ultimate tensile strength (UTS) gains of 25–35% at doses between 70 and 170 kGy, attributed to dominant crosslinking. By contrast, LZ composites displayed only limited improvement before embrittlement occurred at doses beyond 170 kGy due to oxidative scission and microcracking. These findings highlight resin-specific responses to irradiation and demonstrate the potential of gamma processing as a low-cost, non-thermal curing strategy for epoxy-based composites.