Background: This technical brief discusses material degradation issues and potential remedies related to advanced thermoset composites manufacturing using a new out-of-autoclave consolidation and curing process called Electron Beam processing with Specialized Elastomeric Tooling for Resin Infusion (EB-SETRI). To provide context, the design process for EB-SETRI tooling based on finite element structural analysis and Monte Carlo simulations of EB attenuation within tooling materials is briefly described. Of particular interest in this paper is the elastomeric mask, since it exhibits significant changes in mechanical properties based on prior work. Methods: Samples of five different silicone blends (four different durometers and two different catalysts) and one urethane (elastomeric mask materials of choice) were irradiated by an EB source with 3.0-MeV maximum power to simulate the conditions experienced by EB-SETRI tooling during processing. Changes in surface hardness and compression modulus were measured using ASTM D575 and D2240 as a function of dosage. Results: Urethane embrittles and becomes unusable even at low dosages, whereas silicone generally hardens to a maximum level at higher dosages, presumably due to increased crosslinking density, and stiffens (modulus increases) linearly. The embrittlement of silicone is shown to be a result of the EB irradiation and not due to a temperature increase from energy absorption. Conclusions: Changes in elastomer mechanical properties confound process performance as a result, and several concepts for dealing with these changes are suggested. Although the experimental focus is on EB-SETRI, results apply to any manufacturing process that combines the use of EB irradiation and elastomers.