Hygrothermal Modeling of Thick Thermoset Resin during Electron-Beam-Cure – Part I: Methodology and Modeling Cure Kinetics

Abstract

The hygrothermal model has been developed to predict the temperature evolution, epoxy conversion ratio, the glass transition temperature increase and associated resin yield stress rise, and absorbed moisture vapor pressure in ISbF 6 -catalyzed DGEBA epoxy resin systems during e-beam-induced polymerization on the effects of four different initiator concentrations: 0.1,1,3, and 10 phr. This paper summarizes the modeling procedure of e-beam-induced cure kinetics, and the results of local temperature and degree of cure rise within the sample as a function of dose. Dynamic characteristics of Tg y Pv rise and their modeling procedures together with an attempt at optimizing e-beam cure process will be presented in a subsequent paper. These papers provide a methodology to generate the overall integrated model for the e-beam, fast cure process of composites and the consequences upon process control in terms of thermal control, moisture-induced void elimination, and minimization of inherent composite processing stresses that had not been previously addressed by composite process model studies. An autocatalytic model was chosen to describe the cure kinetics for this study and provided excellent agreement with experimental results. The numerical results showed that the cure reaction of ISbF 6 –DGEBA epoxy resin is diffusion controlled, but long lived reactive species allowed for measurable increase in conversion after e-beam irradiation (postcure effects). Higher initiator concentration results in higher degree of cure at a specific dose, causing higher temperature rise and larger temperature and conversion ratio gradients within the sample under given experimental conditions.