A Method for the Prediction of Long-Term Creep Behavior of Continuous Fiber-Reinforced Thermoplastic Unidirectional Tape

This paper provides a method to predict the long-term creep behavior of continuous glass fiber-reinforced polypropylene composites (CGFRPP). The finite element method was used in this study, which was based on short-term experiments. For these calculations, a viscoelastic constitutive equation named the Burgers model was introduced to describe the creep behavior of pure polypropylene (PP) resin. The suitability of the Burgers model for the PP resin was investigated by performing short-term creep experiments under various stress conditions. The stress-dependent Burgers model was, thereafter, proposed by the calibration of elastic stiffness and viscosity parameters in nonlinearity. This nonlinear model was finally incorporated into a representative volume elements (RVE) model to predict the long-term creep behavior of CGFRPP unidirectional (UD) tape. It was found that the simulation results agreed with experiments when using the nonlinear Burgers model. The creep mechanism of the UD tape was also analyzed microscopically with the RVE model, and the redistribution of stress in the fiber and matrix was discussed.