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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 was created in the panel and the aforementioned biaxial fatigue load applied, causing the 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 made in the bidimensional approach and concerning the delamination area and the fibre integrity during the propagation. Due to the lack of experimental data on the size of the delamination area (increasing as the crack propagates), the latter is assessed by the aforementioned iterative 3D BEM analyses, 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).

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