Finite Element Analysis of Bird-strike on Leading-edge Structures

Abstract

Bird-strikes are fatal incidents, which are to some degree unpredictable. It places threats on many levels of the aero industry. Therefore, it has become a critical area of interest in research, as well as design and manufacture. The subject for consideration, of this study, is the engineering problem of material performance under high-velocity impact; efforts are made to build a valid finite element model for analysing and optimising material structure using numerical approaches. Finite element analysis is developing rapidly, along with equally-thriving computer science. It tackles the complexity of solving a non-linear question without an analytical solution, by discretising continuous complex structures into separate elements. In addition, numerical analysis of such problems has been widely used as a more flexible and economical approach for supporting and verifying experimental tests. This study investigates the characterisations of sandwich structures with leading-edge bays that have a honeycomb core, under a high-velocity bird strike impact, with the help of a finite element analysis. Firstly, a FE (finite element) model of a sandwich structure leading-edge bay with a honeycomb core is built in ABAQUS, a widely-used commercial FE analysis software. The sandwich structure that makes of the leading-edge curve surface of the bay, consists of thin Al2024 sheets that serve as the inboard and outboard, and an Al2024 honeycomb, with the thickness of 6.35mm, serves as the core. The geometry model and setup are taken from previous research by Guida (2007), where the leading-edge bay structure was designed and tested in a bird strike experiment with an air gun. The FE simulation results of this thesis are therefore justified by previous experiment results with the same scenario setup. Thus, the FE model can be employed as the benchmark for the following design and configurations. A new design of the outboard of the sandwich structure is proposed, two different configurations of FML (fibre metal laminate) are chosen to replace the outboard of the leading-edge bay sandwich structure, aiming to enhance impact resistance. FML allows metal alloy properties to dominate the material performance, yet considerable specific advantages on metal fatigue, impact, and corrosion resistance are obtained. The bird strike simulations are conducted with the two configurations in the new design, and the results are compared with the original design. The ability to maintain the original shape of the structure is one of the critical considerations of the new design; the damage characteristics for the new design are also investigated. Compared to the previous work, this thesis made an improvement on impact damage prediction by employing a progressive damage material model. In the previous work, the lack of a valid material failure evolution or propagation model makes rapture and delamination phenomena hard to be reflected in simulation results. Meanwhile this thesis took a further step in investigating impact characteristics of a multi-material laminate structure, involving both metal and unconventional fibre materials.