Hygrothermal modeling of thick thermoset resin during electron beam cure

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 I+Sb$F-6$ 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. The numerical results showed that the cure reaction of I +Sb$F-6$ DGEBA epoxy resin is diffusion controlled, but long lived reactive species allowed for measurable increase in conversion after e-beam irradiation (post cure 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. One simulation was performed to optimize the e-beam cure process by controlling the thermal history of the sample via adjusting thermal boundary conditions. The results showed that the temperature gradient in the resin could be reduced significantly and the critical condition under which the moisture induced blistering occurs could be avoided during cure, while obtaining the same degree of cure as before. Finally, the thermal gradient across the fiber matrix interface was modeled on a larger scale in order to study the development of stresses during the rapid cure of the carbon fiber epoxy resin under e-beam irradiation.