Detecting and locating delamination defect in multilayer pipes using torsional guided wave

Delamination is a major defect in composite structures, such as multilayer pipes, that degrade the mechanical properties and longevity of these pipes. Therefore, in this research, using torsional guided wave has been considered to detect delamination in the multilayer pipes. First, an analytical investigation of torsional wave propagation in intact multilayer pipes has been used, and the corresponding dispersion curves and group velocity have been plotted following the implemented boundary conditions of the problem. Moreover, this research used the finite element method to simulate the torsional wave propagation in these pipes and implemented the analytical results to validate the simulated model, extended later to study the delamination defect. Besides detecting and determining the location of the applied defect, the influences of the geometric parameters of the defect, such as length and position, were also explored. The results indicated the advantages of using torsional guided waves to identify the delamination defect and its location in multilayer pipes. Moreover, based on the decreased reflection coefficient of delamination defects in the inner layers compared to the outer counterparts, this research distinguished the interface between the two adjacent layers where the delamination occurred.