Test MethodAccelerated fatigue life testing of polycarbonate at low frequency under isothermal condition

An accelerated life testing (ALT) method has been developed to determine the long-term fatigue strength over millions of cycles for glassy polymers. Dumbbell shaped specimens made of carbon particle filled polycarbonate (PC) were tested under tension-tension fatigue, based on the strength-lifetime approach (S-N curve). Fatigue-induced localized irreversible deformation is considered to be the defect leading to fatigue failure; its evolution behavior is characterized by a modified energy activation model in which temperature and stress are considered as fatigue acceleration factors. This model allows the reduced time concept to account for the effects of different temperatures and stresses in the short-term fatigue data. The long-term fatigue life is determined through the use of time-temperature and time-stress superpositions that are applicable under low frequency and isothermal conditions. The experimental results provide assurance for the proposed accelerated fatigue life testing technique for polymers.