Cohesive zone method for failure analysis of scarf patch-repaired composite laminates under bending load

The repair of composite materials has received much attention in recent decades because these materials are used in a wide range of industrial applications owing to their excellent mechanical properties. In this work, the failure of scarf patch-repaired composite laminates subjected to bending loads was experimentally and numerically investigated. Thirty repaired laminates with a scarf angle of 5.7 degrees or 3.8 degrees were prepared and tested under different bending loads. Three-dimensional finite element models implementing cohesive elements were created to examine crack initiation and propagation in the specimens during loading. Experimental results revealed that a combination of adhesive, intralaminar, and interlaminar failure occurred in the bonding surface area. Compared to the failure of repair under tensile loading, additional failure occurred in the patch. Simulations reproduced these failure modes well with cohesive elements. The failure loads were also accurately predicted with a maximum prediction error of 9.7%.