Reducing repair dimension with variable scarf angles

The increase in composites usage for primary and secondary structural components demands advanced repair techniques such as doubler, multi-step, and scarf to restore a damaged structure to its original design capability. Currently, most scarf repairs employ a straight taper at a typical ratio ranging between 1:20 to 1:60 to attain the original design strength. This paper aims to present a new method for reducing the footprint of scarf repairs by optimizing the taper profile through the composite thickness. Experiments are carried out on scarf repairs with piece-wise linear scarf joints, in which the 0° plies are tapered at two different ratios of 1:30 and 1:20, while the 45° and 90° plies are tapered at a ratio of 1:2. Experimental results show that compared to 1:20 straight scarf, the 1:30/1:2 piece-wise linear scarf can achieve 75% of the tensile strength while reducing the repair size by 60%.