Bird impact effects on different types of aircraft bubble windows using numerical and experimental methods

Abstract

This paper uses numerical and experimental techniques to investigate the effect of bird strike on different types of aircraft bubble windows with different geometries and materials. Three different methods, namely Lagrangian, Arbitrary Lagrangian Eulerian (ALE) and Smooth Particle Hydrodynamics (SPH) are used to simulate bird strike effects on different types of bubble windows during the impact phase. Simple tension tests are carried out on some samples to determine the behaviour of window material during impact while models reported in the literature are used for modelling the bird. First, a simple bubble window is studied numerically using the Lagrangian, ALE and SPH techniques and the results are compared with experimental data. The results from all techniques are found to be almost similar and in good agreement with the test data. This will give way to only ALE to be used for other case studies. Next, bird impacts on a two-layer bubble window with a Poly Vinyl Butyral (PVB) interlayer and a multi-walled stretch acrylic bubble window are investigated numerically. Simulations for the latter bubble window show that the structure does not have enough strength to resist the bird impact as required by the FAR25 standard conditions. For this type of bubble, two bird impact tests are carried out with speeds lower than that needed for avian certification authorities and compared with numerical results. Finally, a three-layer bubble window with a polymeric interlayer will be proposed as a new design and it will be shown that this type of bubble is capable of withstanding against bird impacts according to the FAR standard conditions.

Keywords:

• bird strike
• bubble window
• finite element