Evolution of cure, mechanical properties, and residual stress during electron beam curing of a polymer composite

Evolution of cure, mechanical properties, and residual stress during E-beam (Electron Beam) processing was studied to evaluate the influence of process parameters – dose and dose per pass – using an epoxy reinforced with IM7 carbon fibers. The composite prepreg was also cured thermally to various cure levels and compared with the E-beam cured composite. Cure evolution changed substantially with irradiation condition; lower dose/pass and wider scanning width of the beam (for the same dose/pass) resulted in rapid curing. For a given degree of cure, the longitudinal (E11) and transverse (E22) moduli of the E-beam cured composite varied with dose/pass and were less than that of the thermally cured composite. Transverse strength and failure strain of the composite cured at 20 kGy/pass were higher than that of composites cured thermally and at other dose/pass conditions. E-beam curing resulted in lower residual stresses than thermal curing and lower dose per pass resulted in lower cure-induced residual stress than higher dose/pass.