Characteristics of accelerated lifetime behavior of polycarbonate under athermal and high loading frequency conditions

An accelerated lifetime testing (ALT) technique has been developed to determine the long-term fatigue life over millions of cycles for glassy polymers. Dumbbell shaped specimens made of carbon-filled polycarbonate (PC) were tested under fatigue based on the stress-lifetime approach (S-N curve). Fatigue-induced localized yield-like deformation is considered as the defect leading to fatigue, and its evolution behavior is characterized by a modified energy activation model in which temperature and frequency are considered as fatigue acceleration factors. This model allows the reduced time concept to account for effects of different temperatures and frequencies in short-term fatigue data to determine long-term fatigue life through the use of time-temperature and time-frequency superpositions that are applicable under high frequency and athermal conditions. The experimental results show that the application of the reduced time model can be a possible method for ALT of time-dependent polymeric materials.