The influence of material and process parameters on high-energy electron beam curing of polymer composites

Abstract

High-energy electron beam (EB) curing of advanced composites is a novel alternative to conventional thermal processing. It offers the possibilities of both cost reduction and technical improvements when compared to autoclave curing. The purpose of this thesis is to present a critical examination of the process of EB curing, with the intent of developing a better understanding of its potential for commercial use. Specifically, this study describes EB curing, and then identifies and examines the influence of important material and process parameters on curing and material properties. A resin system consisting of a high-temperature epoxy and a cationic photoinitiator is investigated. The material and process parameters of radiant dose, initiator concentration, temperature, dose rate, and reinforcement are analysed for their effect on cure extent and glass transition temperature, Tg. Experimental investigation is performed by differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). Properties are also compared between EB and thermally cured samples of the identical resin formulation by mechanical testing. The most notable result of this research is th t incomplete curing (less than 80% cure extent) occurs for the epoxy formulation irradiated at room temperature, even at EB doses as high as 500 kGy. Also significant is that the ultimate cure extent is strongly influenced by the temperature and dose rate during processing. These results may curtail some of the proposed advantages of EB processing such as the ability to EB cure at a selectable temperature. Additional results are presented and discussed which are important to the further development of predictive models for high energy EB curing of composites.