Residual strength prediction of aircraft fuselages using crack-tip opening angle criterion

Ductile tearing simulation and residual strength prediction of wide-body, lap-jointed fuselage panels are conducted. The damage configurations of the fuselage panels consist of a single lead crack and a lead crack with small multiple-site damage (MSD). The crack-tip opening angle fracture criterion and elastic-plastic finite element analysis are used to control stable crack advancement under conditions of general yielding. Thin-shell finite elements are used to model the fuselage structures except in the vicinity of cracks. In this region special plane-strain shell elements are used to capture three-dimensional constraint effects during stable crack growth. A global-local modeling procedure is employed in the numerical analyses. We show that accurate representation of the load transfer through the rivets is crucial for the stress distribution prediction. Modeling fatigue crack closure is essential to capture the fracture behavior at ductile tearing initiation. Breakage of a tear strap can have a major influence on residual strength prediction. Predicted crack growth and residual strength considering fatigue crack closure and tear strap failure agree reasonably well with test results. Observed and predicted results both indicate that the occurrence of small MSD cracks substantially reduces the residual strength.