Material BehaviourRatcheting behavior of an epoxy polymer and its effect on fatigue life

Ratcheting behavior of an epoxy resin and its effect on fatigue life has been experimentally investigated. All the fatigue tests were carried out under stress-controlled mode, and stress-strain data were recorded during the entire fatigue life period by a newly established non-contact real-time strain measurement and control system. Quantitative results of evolutions of ratcheting strain, strain range and strain energy density in tests with various mean stresses and stress amplitudes have been retrieved from the stress-strain data. The amount of ratcheting strain and accumulation rate was sensitive to the stress amplitude and mean stress. Fatigue lives of these tests were compared with previous test results under strain-range-controlled mode and no obvious ratcheting strain effect on fatigue life was observed for this epoxy polymer. Additional fatigue tests with resting periods were further performed to investigate the mechanism of the experimental observations on this epoxy polymer.