Mechanical behaviour of composite laminates repaired with a stitched scarf patch

Abstract

In order to increase the service life and maintain the residual strength of damaged composite structures, it is necessary to investigate effective repairing techniques. In this paper, an innovative stitch-reinforced scarf patch is developed in order to reduce the amount of parent material that is removed during the repair. Carbon fibre threads are used to stitch the scarf patch to a damaged carbon fibre laminate via pre-drilled holes. Following stitching, the vacuum resin infusion technique is used to infuse the carbon fibre threads, thereby fixing the patch to the parent part. Here, the effects of varying both the hole diameter and the scarf angle on the load-carrying capacity of the repaired laminates are studied. The tensile strength, strain distribution and failure mechanisms are investigated using the digital image correlation (DIC) technique. The results show that by introducing a 2.5 mm diameter stitching hole, the ultimate tensile strength of repaired laminates related to three scarf angles is increased by up to 20, 27 and 45% respectively, relative to traditional laminates with an equivalent scarf ratio.