Advanced modelling of bird strike on high lift devices using hybrid Eulerian–Lagrangian formulation

The work presented in this paper deals with application of explicit finite element analyses in order to predict bird strike induced impact damage on high lift devices of typical large transport aircraft. The hybrid Eulerian–Lagrangian finite element formulation has been applied as to efficiently model the impact of a highly deformable object on an inboard flap structural model. As structural elements of aeronautical structures are commonly assembled from structural items manufactured from a variety of materials, a damage prediction methodology on aeronautical structures has to be able to model damage in metallic materials as well as in composite and sandwich structures. The presented methodology employs a progressive damage model for composite materials which is based on Hashinʼs failure initiation criterion. Prediction of damage in metallic structural items is based on the equivalent plastic strain, while strain rate effects are included in the hardening behaviour. An important part of the bird strike modelling procedure is the application of a bird replacement material with constitutive response which replicates the forces induced by an impact of a real bird. The bird material is modelled by an equation of state, with properties that match the pressure–density relations of water and air mixtures. The bird replacement material model and Eulerian impactor model have been validated in a comparison with experimental results available in the references. In order to demonstrate the ability of the presented procedure to simulate bird strike induced damage on actual high lift devices, an example of a possible impact scenario is investigated. The input parameters for the simulation have been selected as to simulate a bird strike used to verify the compliance with damage tolerance certification requirements.