Modeling hailstone fragmentation upon impact with curved aircraft panels using a modified Hertzian contact mechanics framework

Abstract Hailstone impacts on aircraft have become increasingly frequent over the past 2 decades, causing significant damage to various components such as radomes, windshields, engine nacelles, and wings. Observing hailstone fragmentation during flight is extremely challenging due to the high-speed inflight conditions and the rapid nature of the fragmentation process, making it difficult to capture the exact dynamics of the event. Hailstones range in size from 0.5 inches to 4 inches in diameter, and this size variability influences the extent of damage to aircraft panels. To address this, a modified numerical model is required to predict hailstone impact damage on curved aircraft panels more accurately. This paper introduces a fragmentation model for hailstone impacts on curved aircraft panels, using modified Hertzian contact mechanics model. By incorporating the conservation of mass, momentum, and energy, the model successfully predicts contact pressures, deformation behavior, and fragmentation characteristics upon hailstone impact with aluminum alloy panels. It accounts for the influence of impact velocity, hailstone size, and material properties, providing insights into the damage potential of hailstones on critical aircraft components. The findings reveal that smaller hailstones exhibit greater fragmentation, producing a higher number of fragments, while larger hailstones generate higher contact pressures and plastic deformation energy, resulting in more severe damage. Additionally, the fragmentation radius and residual velocity of hailstones decrease exponentially with increasing size, further influencing the severity of impact. These results offer valuable insights into aircraft structural design, emphasizing the need to account for size-dependent effects when developing hail-resistant materials and configurations. Additionally, numerical simulations of the hailstone impact on AA2024 curved panels were conducted on ANSYS Explicit Dynamics ® for validating the analytical results.