Water impact of flexible aluminum panels: Experimental study and numerical validation across different angles for aircraft ditching applications

Ditching behavior is typically studied using either high-stiffness representative structures or excessively complex assemblies replicating case studies of very specific aeronautical structures. The present study aims to investigate a comprehensive approach to ditching analysis, assessing experimentally and numerically the water impact behavior of thin flexible aeronautical-grade aluminum panels (Al 2024 T3), focusing on the influence of various test parameters, including panel thickness, angle of impact, ballast mass, and impact velocity. The panels were mounted on three different test fixtures, depending on the desired impact angles (0 degrees, 15 degrees, and 30 degrees, with the last two being in a wedge configuration), obtaining high repeatability of acceleration and strain measures. A numerical finite element model for ditching applications was enhanced exploiting the structured arbitrary Lagrangian Eulerian (S-ALE) method, allowing for improved leakage control. Sensitivity studies were performed to assess the effect of mesh size and water domain dimensions. The fluid-structure interaction between Lagrangian and ALE domains was correlated with experimental data using quantitative curve comparison metrics. This allowed us to choose the best fitting penalty factor curve to be used in the numerical model. The final model was validated against the experimental results across a wide range of configurations, accurately capturing both acceleration peaks and strain gauge responses. The validated numerical framework has the potential to be used for the creation of a comprehensive robust database of ditching events, paving the way to future development of efficient, data-driven simplified numerical tools for early-stage aircraft design.