Uniaxial Compressive Response and Constitutive Modeling of Selected Polymers Over a Wide Range of Strain Rates

Abstract

The present work deals with constitutive modeling of the compressive stress–strain response of selected polymers at strain rates from 10−3 to nearly 103 s−1. Six different commercially available extruded polymers—ABS, HDPE, PC, POM, PP and PVC—are tested at room temperature. Cylindrical specimens with a slenderness ratio (=length/diameter) of 0.5 are used in high strain-rate tests, and those with the slenderness ratios of 1.0 and 2.0 are used in low and intermediate strain-rate tests. High strain-rate compressive stress–strain loops up to a strain of nearly 0.08 are obtained on a standard split Hopkinson pressure bar. Low and intermediate strain-rate compressive ones are measured on an Instron testing machine. By fitting experimental loading stress–strain data to a modified Ramberg–Osgood equation, material parameters are uniquely determined using a linear least-squares procedure. Experimental results indicate that all polymers tested exhibit intrinsic dynamic viscoelastic–plastic characteristics and a higher elastic after-effect following complete unloading. It is shown that the modified Ramberg–Osgood constitutive model is appropriate for describing the monotonic loading compressive stress–strain relations of the three semi-crystalline polymers over a wide range of strain rates. The advantages and limitations of the constitutive model are also discussed.