Bonded crack retarders are a novel technology for providing improved damage tolerance in aerospace structures. They can be applied either where mechanical fastening is being replaced by integral construction, or simply as a means of improved crack growth resistance in fatigue -critical locations. In previous studies we have measured the residual stresses arising from the CTE mismatch between the reinforcing strap and the substrate. We are now moving on to investigate the effects of the residual stress in cases where there is a joint through the strap, and the interaction between the joint and strap stress fields within the operating temperature envelope of ¿50 to + 70 degrees C.