Water Impact of Metallic and Composite Material Structures: Experimental Tests and Numerical Simulations Adopting the ALE Approach

Water impacts in emergency are likely to have tragic consequences for the passengers of helicopters. Most of the passive safety devices developed for helicopter crashworthiness are designed for ground impact. When impacting a solid or a soft surface, impact loads are rather different and therefore energy absorption devices developed for ground impact are not effective during a water impact. In order to collect reliable data for numerical models validation, water impact drop tests were carried out: an Aluminium alloy and a Carbon Fibre Reinforced Plastic panel, similar to modern aircraft skin panels, were mounted on a specific test device and tested. Impact decelerations and deformations of the panels were measured. Afterwards, a numerical model of the tests was worked out. The Arbitrary Lagrangian Eulerian approach was adopted to model the fluid region. Eventually, a close experimental-numerical correlation was obtained for both the panels in terms of impact dynamics, decelerations and deformations. The main features of the event and the differences between the impact behaviour of the two panels are discussed and failure of the composite panel was investigated. Guidelines for further investigations are also drawn