DBEM Simulation of a FML Full Scale Aeronautic Panel Undergoing Biaxial Fatigue Load,

This paper concerns the numerical characterization of the fatigue strength of a flat stiffened panel, designed as a fibre metal laminates (FML) and made of Aluminium alloy and Fibre Glass FRP. The panel is full scale and was tested under fatigue biaxial loads, applied by means of a multi-axial fatigue machine: an initial through the thickness notch is created in the panel and the aforementioned biaxial fatigue load is applied, causing a crack initiation and propagation. The fatigue test is simulated by the Dual Boundary Element Method (DBEM) in a two-dimensional approach, followed by a 3D BEM sub-modelling analysis, needed to justify the assumptions on delamination area and fibre rupture made in the 2d crack propagation. Due to the lack of experimental data on the size of the increasing delamination area (varying as the crack propagates), the latter is assessed by the aforementioned DBEM sub-model simulation, considering the inter-laminar stresses and a delamination criteria. This approach aims at providing a general purpose evaluation tool for a better understanding of the fatigue resistance of FML panels, providing a deeper insight into the role of fibre stiffness and of delamination extension on the stress intensity factors. The experimental test was realized in the context of a European research project (DIALFAST)