Temperature/Stress-Dependent Fractional Creep Models of Thermoplastic Polymers

The creep behavior of thermoplastic polymeric materials is highly dependent on loading conditions, which must be accounted for in the intrinsic model. In this paper, fractional creep models have been developed to describe the temperature/stress-dependent creep/creep-recovery and accelerated creep damage behavior, with the construction of a criterion correlating model parameters with temperature and initial stress. The fractional order in the fractional creep/creep-recovery model can be physically interpreted by the well-known master curve, and the creep rupture time can be predicted by combining the Monkman-Grant law with the fractional creep damage model. Extensive experimental data are employed to substantiate the model's applicability under different loading conditions. Moreover, a comparative analysis highlights the proposed model's superior simplicity and performance over existing models.