Characterization and modelling of the PEKK thermomechanical and creep behavior above the glass transition temperature

The present work focuses on the characterization and the modelling of the PEKK 7002 thermomechanical behavior at temperatures between the glass transition temperature, Tg (≈160 °C), and 200 °C, as experienced in tensile, load-unload-reload and creep-recovery tests. A novel strain measurement image analysis based tool (IAT) is presented and compared with existing measurement setup, and employed for the validation of the strain measurement acquired during the thermomechanical tests. The crystallization kinetics between 165 °C and 200 °C is described and the coupling with thermomechanical solicitations is investigated. An analytical description of the identified mechanisms is proposed for the tensile, load – unload and creep-recovery solicitations and it constitutes a 1-D model of PEKK 7002, which is employed for understanding the experimental results.