A Comparative Characterization of the Creep Behavior of Short-Fiber Reinforced Composites Based on the Prony Series and Fractional Derivative-Based Creep Models

This work examines dynamic models for describing the viscoelastic behaviour of short-fibre reinforced plastics in tensile tests. The creep behaviour of reinforced PBT GF30 compared to unreinforced PBT GF0 is investigated on the basis of experimental data. Two different modelling approaches are compared: a generalised Maxwell model based on the prony series and a model with fractional derivatives. The experimental data show that glass fibres significantly reduce the deformation under constant load, as they stiffen the polymer matrix and inhibit creep deformation. Parameters can be determined for both models using machine learning methods. However, the Prony-Maxwell based model requires three parameters to accurately represent the data, whereas the fractional model only requires two parameters. The results clearly show the advantages of fractional model for the description of the long time series behaviour: on the one hand, fewer parameters are required and on the other hand, additional knowledge can be gained through the interpretation of the parameters obtained. The experimental data as well a the open-source software developed to learn the model is published alongside this work.