Adhesively bonded timber joints - Do defects matter?

Although adhesively bonded timber joints have proven their suitability as a structural joining method, and often provide a better mechanical performance, practitioners remain reluctant to consider them as a substitute for traditional mechanical fasteners. Among the main reasons invoked, the quality control with regard to defects in the adhesive layer remains the most challenging. Little research effort, however, has been put into the evaluation of the effect of defects on the performance of adhesively bonded timber joints, respectively to which extent defects influence joint capacity. The experimental investigation of the influence of artificial defects on the capacity of adhesively bonded timber joints presented herein, completed by numerical calculations, demonstrated that joints with 50% amount of missing adhesion still achieve 70% amount of capacity of defect free joints. The investigation furthermore showed that it is possible to computationally estimate the influence of defects on joint capacity.