Fibre steering for shear-loaded composite panels with cutouts

The traditional approach to mitigate problems resulting from stress concentrations around cutouts for windows and doors in aeronautical structures, either made of metallic or of composite materials, is to locally thicken the structure increasing its weight as well. A more effective solution, without weight penalties, is to reduce the peak stress by redistributing loads to supported regions of the panels such as frames and stiffeners. This can be achieved by means of fibre-steered laminates with variable in-plane stiffness. In this work, the potential of these novel designs for the purpose of stress alleviation around cutouts in composite panels is explored. The optimal configurations in terms of shear buckling and postbuckling failure responses are identified by means of parametric numerical studies. It is predicted that there are steered-fibre configurations that outperform the optimal straight-fibre ones for hole sizes up to two-thirds of the panel width.