A new phenomenological constitutive model for thermoplastics

Abstract A new phenomenological constitutive model is proposed to predict the mechanical behaviour of thermoplastics in the current research. The new constitutive model and the method to determine the parameters of the model are introduced. In the new model, a transition function is proposed to enable a smooth transition of the flow stress behaviours under both small-strain and large-strain conditions. In validating the model with testing data of Polyetheretherketone (PEEK) and Polycarbonate (PC), it is found that this new model is able to predict different phases of the flow stress behaviour of thermoplastics in consideration of the effect of strain, strain rate and temperature. Although the basic trends of tensile and compressive behaviours of PEEK and PC materials are different, the new constitutive model can be used to represent these behaviours effectively. In addition, the results show that the new model gives a favourable prediction of the PC material at high strain rate conditions. Compared with Johnson-Cook, Nasraoui et al., Duan-Saigal-Greif-Zimmerman (DSGZ) and Mulliken-Boyce models, the new model presents an improved level of accuracy on the mechanical behaviour of thermoplastics in a wide range of deformation conditions.