High strain rate sensitivity of epoxy/clay nanocomposites using non-contact strain measurement

Abstract

As polymers are rate sensitive to mechanical properties, dynamic tensile tests are carried out on drop mass setup, to obtain medium strain rate stress-strain response which fills the gap between quasi-static strain rate (<10 s−1) and split Hopkinson pressure bar (SHPB) technique (>1000 s−1). The present research work is to study the effect of medium strain rate on tensile behavior of epoxy/clay nanocomposites. Neat epoxy and nanocomposites containing 1.5, 3 and 5 wt% clay content are fabricated using mechanical stirrer. The dispersion of nanoclay in epoxy is examined using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The digital image correlation (DIC) technique is employed for evaluating full-field strain and strain rate using high speed CCD camera, which captures about 100,000 frames per second. Stress-strain measurements are reported for epoxy/clay nanocomposites for strain rates ranging from 0.008 to 450 s−1. The results reveal that the tensile strength and modulus increase with increase in strain rate for epoxy and its clay nanocomposites. The fracture surfaces of tensile specimens are investigated using scanning electron microscopy (SEM).