Guided wave phased array beam steering in composite plates

Guided wave phased array systems have great potential in structural health monitoring (SHM), especially for aircraft applications due to its capability of steering the emitted guided wave beam to inspect a large area with the sensor array at just one accessible position. However, when the guided wave phased array is applied to composite panels of an aircraft component, the anisotropic behavior of the composite materials leads to a significant influence on the beam steering performance of the phased array. In this study, mode neighborhoods in dispersion curves where guided waves have quasi-isotropic behavior (i.e. constant or similar phase velocities in different wave propagation directions) are explored for unidirectional, cross-ply, and quasi-isotropic composite plates. It was demonstrated that the energy skewness of guided waves was well suppressed in these mode neighborhoods. Furthermore, by utilizing a modified delay-and-sum beam forming algorithm, the guided wave beam of a linear phased array can be steered quite well to the desired directions in a composite plate.