Environmental Degradation of Adhesive Joints Single-Lap Joint Geometry

The single-lap shear test is the most widely used method for producing in-situ shear strength data on adhesively bonded joints. The simplicity and low costs associated with specimen manufacture, testing and data analysis has contributed to the widespread use of this method for assessing environmental and fatigue resistance. This report evaluates this method in terms of fitness for purpose in assessing environmental performance and provides a guide to specimen geometry, manufacture and testing. The report also includes an evaluation of the perforated single-lap joint, which is assumed to promote accelerated ageing by shortening the diffusion path of moisture. The results of a comprehensive study will show that for a moisture sensitive adhesive system, the introduction of holes has no major effect and that temperature and exposure time have a far greater influence on strength retention. A number of tools have been employed in data interpretation. These include finite element analysis, statistical techniques, analytical modelling, fractographi