Low-velocity impact response of non-woven hemp fibre reinforced unsaturated polyester composites: Influence of impactor geometry and impact velocity

In this study, the influence of varying impactor geometries on the impact damage characteristics of hemp fibre reinforced unsaturated polyester composites were subjected to a low-velocity impact loading using an instrumented falling weight impact test setup. The three varying tup geometries: hemispherical, 30° and 90°, at four different impact velocity levels: 2.52 m/s, 2.71 m/s, 2.89 m/s and 2.97 m/s were assessed. The experimental results to investigate the influence of impactor geometry suggest that HFRUP composites were able to withstand higher loads when tested with hemispherical impactor and also absorbed more energy than that for 90° and 30° shaped tup geometry. The post impact damage patterns and failure mechanisms of impacted samples were further characterised by ultrasonic (UT) inspection. Impact induced damage characterised by scanning electron microscope (SEM) suggests that damage induced by the impact included a typical failure mechanisms showing matrix cracking, fibre breakage and fibre pullout. As the impact velocity increases the damage to back face of the laminate increased for laminates tested with a hemispherical impactor while it decreased to certain extent for laminates tested with 90° and 30° impactor geometries.