Correlating Shear Slip and Contact Pressure for Health Monitoring of Bolted Joints in Aerospace Structures

Bolted joints are critical components in aerospace structures. Checking the integrity of these connections, although time consuming, is a necessary step before launching aerospace vehicles and satellites. Recent advances in structural health monitoring (SHM) suggest the possible use of SHM technologies to assess the integrity of these joints. Moreover, there exists a need for continuous monitoring of aerospace structures after launching. This continuous monitoring requires relating damage features that can be extracted using sensing techniques (e.g. ultrasonic methods) to physical quantities representing the structural integrity of bolted joints typically related to contact pressure. This paper describes an experimental effort to correlate shear slip measurements of a bolted connection to contact pressure. The contact pressure map (spatial distribution of contact pressure) is calibrated to the torque applied to the bolted connection. Loading and unloading experiments on the joint allowed separating elastic and shear slip displacements. Shear slip is then correlated to contact pressure maps. Further efforts are underway to connect these measures to SHM metrics.