| The objective of this study was to understand the correlation between impact velocity and dynamic fracture initiation toughness in linear medium-density polyethylene (LMDPE). Three series of experiments were conducted. These experiments were grouped by impact velocity: Low, Medium and High impact velocity. In order to determine fracture toughness initiation a three-point bend technique utilizing a modified Hopkinson-bar apparatus was developed. Strain measurement at a single strain gage station was utilized to obtain force and load-point displacement. Moreover, the history of crack initiation and rapid crack initiation was measured by a crack propagation gage attached to the polymer specimen. Along with these experimental measurements, extensive optical and scanning electron microscopy was conducted to elucidate the micro- and macro- damage mechanisms operative during dynamic fracture of polyethylene. The results in this research have been compared to deductions obtained by employing other techniques by diverse authors, and provide a better understanding of fracture initiation as a function of impact velocity. |
