Influence of the cohesive law shape on the composite adhesively-bonded patch repair behaviour

In this study, the cohesive failure of the adhesive layer of an adhesively-bonded joint under uniaxial tensile loads in static conditions is discussed as an approximation to the behaviour of adhesively-bonded repairs. A three-dimensional finite-element model of a single-lap joint was developed using the commercial code Abaqus. Cohesive Zone Models (CZM) coupled to Finite Element Analysis, were used to study the failure strength of the joint. They allowed the prediction of the initiation of the crack and its growth. CZM are governed by a traction-separation law, which can acquire different shapes. The numerical model, considering a linear cohesive law, was validated with 2D numerical and experimental results available in the literature. The effect of different cohesive law shapes, such as exponential and trapezoidal, on the failure load of the joint was studied. In addition, a cohesive parametric analysis was performed, varying the adhesive toughness and cohesive strength. The most suitable cohesive law was the trapezoidal, since the failure load results were close to the experimental data taken from the literature. The cohesive strength is identified as the most influential parameter on the studied variable.