Issue 35

R. Sepe et alii, Frattura ed Integrità Strutturale, 35 (2015) 534-550; DOI: 10.3221/IGF-ESIS.35.59 534 Static and fatigue experimental tests on a full scale fuselage panel and FEM analyses Raffaele Sepe, Enrico Armentani Department. of Chemical, Materials and Production Engineering - University of Naples Federico II, P.le V. Tecchio, 80 - 80125 Naples, Italy. raffsepe@unina.it Francesco Caputo Department of Industrial and Information Engineering - Second University of Naples Via Roma 29 - 81031 Aversa, Italy. A BSTRACT . A fatigue test on a full scale panel with complex loading condition and geometry configuration has been carried out using a triaxial test machine. The demonstrator is made up of two skins which are linked by a transversal butt-joint, parallel to the stringer direction. A fatigue load was applied in the direction normal to the longitudinal joint, while a constant load was applied in the longitudinal joint direction. The test panel was instrumented with strain gages and previously quasi-static tests were conducted to ensure a proper load transferring to the panel. In order to support the tests, geometric nonlinear shell finite element analyses were conducted to predict strain and stress distributions. The demonstrator broke up after about 177000 cycles. Subsequently, a finite element analysis (FEA) was carried out in order to correlate failure events; due to the biaxial nature of the fatigue loads, Sines criterion was used. The analysis was performed taking into account the different materials by which the panel is composed. The numerical results show a good correlation with experimental data, successfully predicting failure locations on the panel. K EYWORDS . Multiaxial fatigue; Full scale panel; FE model; Sines criterion; Life prediction. I NTRODUCTION he global risk analysis must take into account all statistical structural parameters, their variation and their effects on design and response properties of aircraft structural components. In fact the structural safety and reliability can be estimate on a probabilistic basis providing information on the confidence that should be given to the predicted behaviour. The development of an overall probabilistic approach, aim of to evaluate the damage tolerance of the structure, must be based on a better description of the entire process of structural degradation (i.e. as crack initiation process, the use of initial flaw sizes, crack growth in small and long crack regime, residual strength) tuned to different structural details. Therefore one of the main tasks of the airframe design is the full-scale fatigue test, where an airframe is subjected to realistic loads, which are representative of those predicted to occur over the life type. Generally these fatigue tests are cycled until the equivalent of several lifetimes is achieved or an unrepairable failure occurs. In the last years several full scale fatigue tests on fuselage panels have been conducted [1-5]. In these tests the airframe is subjected to T