Monitoring of bearing failure in composite bolted connections using ultrasonic guided waves: A parametric study

Bearing damage in composite bolted connections (such as those commonly used in aerospace applications) is investigated through the application of ultrasonic guided waves. Specifically, identical macro-fiber composite sensor arrays were bonded to each of two identical composite plates. One plate was then inspected ultrasonically in the unloaded condition with bearing damage being introduced through successive uniaxial tensile tests, while the other plate was assessed while under load in the tensile testing machine. A scattering matrix approach is employed to characterize the interaction of the guided waves with the target bolt hole. The effects of applied load and the bolt fixture on the ultrasonic results are explored. A parametric study is carried out to determine the optimal actuation frequency and interrogation angle for this application. The results demonstrate that the system is capable of detecting bolt bearing damage as well as monitoring of the applied load in the elastic region.