Development of a Hailstone Substitute for Representative Impact Tests

The present work started with the analysis of real hailstones collected during a storm in France. The microstructure of real hailstone was studied in order to highlight its composition and crystallographic orientations. It helped understanding the formation and the growing mechanisms of hail in the atmosphere. Its impact behaviour was then studied through two different impact experiments: ballistic impacts on rigid target and on deformable targets. It was then compared with the impact response of standard reference ices (manufactured following ASTM standard and with standard freezing) on the same impact setup. From these observations several ices (with different microstructures) were developed and also tested, in order to select the best candidate to simulated the real hailstone. The behaviour of these ices was also studied with quasi-static tension and compression test, and dynamic compression test on Split Hopkinson bar apparatus. A numerical model and an equation of state were developed in LS-Dyna finite element commercial code. At the end, this study that combines multidisciplinary and joint study between microstructure analysis, numerical modelling and experiments, helped to develop a hailstone substitute with its associated shock behaviour model.