Effect of high-energy radiation on the relaxation of residual stresses in polycarbonate and epoxy resin by stress optics

Residual stresses are an important factor in many polymers because they affect the components strength and potential warpage. Polymers exposed to gamma-ray radiation are no exception. The two polymers investigated (bisphenol-A based polycarbonate and epoxy resin), are potentially irradiated either as part of a sterilization process or during later application as part of composite or insulation material. Both polymers show a photoelastic effect that is used in this research to study the effect of 200 kGy and 500 kGy on the relaxation behavior of epoxy and polycarbonate, respectively. The photoelastic sensitivity for pristine and irradiated samples was found to decrease by irradiation treatment. In addition, EP and PC relaxed by 36 and 27% respectively, due to irradiation treatment. Furthermore, epoxy resin shows some artifacts in the stress optical images, which are likely related to curing and are not related to residual stresses.