Abstract
Semi-crystalline polymers are increasingly used in structural applications where they can withstand dynamic loads. It is then, of highly importance, to measure and model their mechanical behavior over a wide range of strain rates. In this paper, the polyetheretherketone's yield stress is investigated under quasi-static (0.0001-0.1/s), intermediate (5-500/s) and high (500-10,000/s) strain rates. Four experimental set-ups were used to achieve this task. It was shown that the mechanical behavior is highly sensitive to strain rate. The yield stress at 10,000/s is 115% higher than at 0.0001/s. Moreover, the strain rate sensitivity increases with increasing strain rate. A new three-material-constant constitutive equation is proposed to take into account the increase of strain rate sensitivity at very high strain rates. An identification approach is also developed to consider the influence of the strain rate range. The material constants, of the new constitutive equation and of three constitutive equations available in the literature, are identified. For each equation, we have reported the strain rate range where each model best fits the experimental data. The new model gives the best trade-off of fitting the experimental data with a good accuracy while minimizing the number of material constants. (C) 2014 Elsevier Ltd. All rights reserved.