Abstract
The photoviscoelastic material used in this paper was prepared by mixing the liquid form base material Epon 828, the hardener MHAC-P and the cure accelerator 2E4MZ in a weight ratio of 100:103.6:1. To avoid the solidifying flow lines appear on the surface of the specimen and the unevenness of the specimen, an innovative vertical type mould was designed to accommodate the mixed materials and execute the curing process. Test specimens were prepared by following the ASTM B 557M specifications. The uniaxial tensile relaxation test and constant strain-rate test were performed at eight constant temperatures, 25°C, 70°C. 100°C, 130°C, 145°C, 160°C. 175°C, and 190°C. Both tests were video recorded for later detailed analysis. The master curves of relaxation modulus and relaxation birefringence strain coefficient were obtained by applying the time-temperature superposition principle. Prony series, Langevin equation and Boltzmann equation were used to fit those master curves. It was found that Boltzmann equation gave the most satisfactory results of fitting. After integrating the fitted Boltzmann equation with the photoviscoelastic theory, the time-varying stress field of the viscoelastic material under investigation can be analyzed. © 2010 SPIE.