THE USE OF TIME-TEMPERATURE SUPERPOSITIONING IN STUDYING THE FRACTURE PROPERTIES OF RUBBER-TOUGHENED EPOXY POLYMERS

The fracture energies, G(Ic), of an unmodified and a rubber-modified epoxy have been ascertained as a function of test temperature and rate. A time-temperature superpositioning technique has been adopted in order to produce a master curve of the fracture energy, G(Ic), versus the reduced rate of test, t(f)/a(T); where t(f) is the time-to-failure and a(T) is the time-temperature shift factor. The value of the shift factor, a(T), as a function of test temperature has been determined from time-temperature shifting the yield stress and the modulus data for the materials. The master curve of G(Ic) versus t(f)/a(T) has been modelled and the values of the constants employed in the model have been deduced. The values of the constants so determined are discussed with respect to the microstructures of the epoxy polymers.