Strain Monitoring and Damage Detection of Single-Lap Joint with Embedded FBGs

The use of adhesive bonding in composites is recently increasing because it has advantages over mechanically fastened joints, such as less sources of stress concentrations, more uniform distribution of load and better fatigue properties. Understanding the behavior of the adhesive joint is required for improving the reliability of a structure with bonding joints. We have developed the distributed strain measurement system based on optical frequency domain reflectometry (OFDR) system. It can measure a strain distribution with the high spatial resolution at an arbitrary position along long-length fiber Bragg grating (FBG) sensors. In this study, we embedded the long-length FBG sensors into the adhesive of a single-lap joint. We could successfully measure the strain distribution at the interface between the adhesive and the adherend in the tensile test. We could also detect damage of the adhesive joint.