FML Full Scale Aeronautic Panel Under Multiaxial Fatigue: Experimental Test and DBEM Simulation, Engineering Fracture Mechanics

This paper concerns the numerical and experimental characterization of the static and fatigue strength of a flat stiffened panel, designed as a Fibre Metal Laminate (FML) and made of aluminium alloy and Fibre Glass FRP. The panel is full scale and was tested under both static and fatigue bi-axial loads, applied by means of an in house designed and built multiaxial fatigue machine. The strain gauge outcomes from a preliminary static test are compared with the corresponding numerical results, getting a satisfactory correlation. A crack propagation in the FML is simulated by a two dimensional original approach based on the Dual Boundary Element Method (DBEM). To overcome the lack of experimental information on the size of delamination area an ‘‘inverse’’ procedure is applied: the delamination introduced in the DBEM model is calibrated in such a way to minimise the numerical and experimental growth rate differences. 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).