Experimental and numerical analysis of fatigue crack growth in integral skin-stringer panels

Abstract

Experimental and numerical analysis of fatigue crack growth in integral skin-stringer panels, produced by means of laser beam welding (LBW), is performed. Since this type of panel is used in airframe construction, fatigue and damage tolerance is of paramount importance, since aircrafts must be tolerant to relatively large fatigue cracks. Firstly, using extended finite element method (XFEM), the fatigue crack growth on the simple flat plate made of AL-AA 6156T6/2.8 mm was simulated, and results were compared with values obtained in the experiment. The same approach was taken to simulate the fatigue behaviour and crack propagation of the real skin-stringer panel (four stringers, laser beam welded). It was found that the results obtained for stress intensity factors (SIFs) KI, KII, KIII and Keff along the crack front, are close to the experimental results, leading to conclusion that the XFEM method can be successfully used in prediction of fatigue life of complex airframe structures, such as laser-beam welded skin-stringer panels.