Mechanical property characterization of partially crystalline Poly-Ether-Ether-Ketone.

The present study investigates the mechanical properties of partially crystalline Poly-Ether-Ether-Ketone between the glass transition and the cold crystallization. Biaxial tension, uniaxial tension, and DMA experiments were conducted to investigate the influence of temperature-induced crystallization on mechanical properties, and three stiffening behaviors are observed. Firstly, a 'U' type mechanical property is observed for all three experiments with first softening and then significant stiffening behavior with increasing temperature. Secondly, stiffening also occurs during low strain rate tests but not in higher strain rate tests. Thirdly, the stiffening behavior of the anisotropic film shows orientation dependence. Crystallinity evolution is predicted by the Nakaruma non-isothermal crystallization kinetics with optimized parameters, with which we demonstrate and explain that the stiffening behaviors are connected to the onset of crystallization. Therefore, the conclusion provides a new tool to approach and distinguish extrinsic and intrinsic properties during characterization, promoting future implementation for constitutive modeling and corresponding simulation that could replicate the influence of temperature-induced crystallization.