Effect of Adhesive Type and Overlap Length on the Mechanical Resistance of a Simple Overlap Adhesive Joint

The present study focuses on the experimental determination of the mechanical behaviour of simple lap joints subjected to quasi-static tensile loads. Four different specimens were tested, resulting from the combination of two different adhesives (ductile and brittle) and two distinct overlap lengths. Cohesive fractures were observed on all specimens, which allowed for a direct comparison of experimental results and failure load prediction using analytical criteria adequate for adhesive joints. Three different criteria were used to predict the failure load, the Volkersen criterion, generalized yielding of adhesive and the adherend yielding criterion. The predictions based on the Volkersen criterion were found to agree well with experimental values obtained for the more brittle material. Moreover, increasing overlap length for the same material only led to a slight increase of the failure load of the joint. However, for the ductile material it was the generalized yielding criterion that better agreed with experimental results, where a significant and linear increase of the failure load was observed with increased overlap length. These results provide valuable insights for material selection and joint design procedures for adhesive joints loaded under large mechanical demands.