A Numerical Model for Hail Impact Analysis

Hail impact is an actual threat for aircraft structures such as the forward sections of the fuselage, the engine nacelles, and the leading edges of wings and tail planes. When flying through a hailstorms region cannot be avoided, these aircraft parts are called to maintain a certain level of functionality even after being impacted by a number of hailstones. In particular, with regard to nacelle intake, these parts have to be such to avoid hailstone penetrations, which could cause a failure of the control-system of the engine usually placed in the lower part of the intake airframe and then the loss of the engine. For these reasons, and also considering the difficulty in performing specific experimental tests, it is important to develop numerical models, which eventually might represent a tool to develop high-efficient and hail-proof structures. In particular, using LSTC LS-Dyna, an explicit Finite Element code, a Smoothed Particle Hydrodynamics (SPH) model of the hailstone has been developed. Initially, this model was validated referring to a laboratory test and, then, referring to the (documented) damages of an airlines aircraft. Subsequently, using the numerical model of an intake in a preliminary design phase, the impact with penetration of a single hailstone and subsequently the simultaneous impact of a number of hailstones were investigated. As a result, the numerical model developed has showed to be feasible and reliable for the analysis of the event investigated.