A review of stress concentration studies on fibre composite panels with holes/cutouts

Composite panels are widely used as structural members due to their high strength-to-weight ratio. In order to reduce further weight, cutouts or notches are introduced in these members. These cutouts also serve utility requirements such as man-holes for purpose of service as well as for passing electric or fuel lines. An aircraft wing rib is a typical example of such a composite panel. Even while composites with holes or cutouts provide great savings in weight compared to metallic structures, the presence of holes itself leads to strength reduction. The reduction in strength is due to the concentration of stress around the vicinity of the hole while the structure is under loading. Different-sized and shaped holes/cut-outs are used in composites structural members, which may serve for different purposes. They, in turn, introduce their own versions of stress concentrations effects in such members leading to weakening of the structure. The stress concentration effect in fibre composites also depends on other factors like fibre orientation, fibre material, matrix material, etc. Loading can also influence stress concentration. This review pursues vast research done in this area and attempts to compare and summarise the diverse findings for designers to obtain a comprehensive concept on stress concentration factor as an effective tool for composite structure design.