Behaviour of two semi-crystalline polymers at a wide range of rates and temperatures

Abstract

Polymers exhibit a strong and complex strain rate and temperature dependent mechanical behaviour. In this paper, we study the response of two semi-crystalline polymers across a large range of strain rates $\left({10}^{-2.5}{s}^{-1}\text{to}{10}^3{s}^{-1}\right)$ and temperatures $\left(-{30}^{\circ }C\text{to}{80}^{\circ }C\right)$. A pre-tensioned split-Hopkinson tension bar and an Instron universal test machine are used in conjunction with climate chambers to achieve the various test conditions, using cameras and digital image correlation to acquire the local deformation field of the test specimen. We find a complex increase in flow stress with higher strain rates and lower temperatures. The test data are then used to evaluate the required features of thermo-viscoplastic flow rules for polymers. To this purpose we evaluate the physically motivated Ree-Eyring model and the phenomenological Johnson-Cook model. It is demonstrated that only the former one is able to represent the behaviour of both materials.