Keywords: dual boundary element method, fiber metal laminates, full scale panel, crack propagation, multi-axial fatigue.

The objective of this paper is to show an original approach based on the dual boundary element method (DBEM), useful to simulate fatigue crack growth in fiber metal laminates (FML). The numerical crack growth rates are calculated using the DBEM in a two dimensional approach [1] and compared with experimental results available from the literature, obtained by a fatigue test on a full scale stiffened panel.

This approach aims at providing a general purpose prediction tool for a better understanding of the fatigue resistance of FML panels [2], providing a deeper insight into the roles of the fibre stiffness and of the delamination extension on the stress intensity factors. The experimental test, realized by a multiaxial fatigue machine [3] in the context of a European research project (DIALFAST), is consistently reproduced by the DBEM.

The geometry and extension of the delaminated area were used as fitting parameters with the aim of obtaining a satisfactory correlation between numerical and experimental crack growth rates. Such a delaminated area is reasonable and compatible with information coming from literature, so that it is possible to interpret such a result as a preliminary validation of the numerical procedure developed for such types of problem, especially considering the simplicity of the adopted DBEM approach (the modeling and meshing process is straightforward) and the reduced computational effort. The obtained crack growth rates decrease with crack advances, showing the optimal damage tolerance properties of the material used.

Further developments will be devoted to an in depth analysis, from the theoretical and experimental point of view, for an accurate assessment of the delamination occurrence and extension.

1

E. Armentani, R. Citarella, "DBEM and FEM analysis on non-linear multiple crack propagation in an aeronautic doubler-skin assembly", International Journal of Fatigue, 28, 598-608, 2006. doi:10.1016/j.ijfatigue.2005.06.050

2

E. Armentani, V. Ascione, R. Citarella, R. Sepe, "BEM simulation and experimental test of a FML full scale aeronautic panel undergoing biaxial static load", in "Proceedings of the International Conference on Multiaxial Fatigue and Fracture (ICMFF9)", Parma, 2010.

3

E. Armentani, F. Caputo, R. Esposito, G. Godono, "A new three loading axes machine for static and fatigue tests", in "Proceedings of the Sixth International Conference on Biaxial/Multiaxial Fatigue & Fracture (6th ICBMFF)", Lisboa, Portugal, 1, 323-330, 2001.

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