On the fatigue crack growth analysis of spliced aircraft wing panels under sequential axial and shear loads

The spliced wing panels on a surveillance aircraft are subject to sequentially applied axial and shear load cycles. This paper aims to propose an approach to address the fatigue crack growth under this scenario. Current understanding on fatigue crack growth behaviours was reviewed, focusing on crack surface interferences and fatigue crack growth mechanisms under non-proportional mixed-mode loads. A generic spliced plate was analysed using non-linear finite element modelling. The analysis revealed shear-induced-bearing at fastener holes, and predicted both shear-induced-KI and shear-induced-KII at a 0° crack emanating from the fastener hole edge. When the crack is short relative to the fastener hole radius, the shear-induced-KI is dominant therefore it has the potential to cause shear-induced mode I overload. As the crack grows longer, the shear-induce-KII increases, and depending on the load level, this may lead to both short-range acceleration and long-range retardation. Through the above analysis, the engineering problem of fatigue crack growth in spliced wing panels under sequential axial and shear loads was converted into a more generally understood problem of fatigue crack growth under cyclic mode I plus intermittent cyclic mixed-mode loads.