Plate Wave Flow Patterns for Ply Orientation Imaging in Fiber Reinforced Composties

Fiber orientations in graphite epoxy laminates of various configurations are investigated by imaging flow patterns of leaky guided plate waves. The plate wave flow pattern (PWFP) technique shows that the guided plate waves in laminated fiber reinforced composites tend to travel along the preferred fiber directions, rather than in the direction of impingement, especially for inhomogeneous ply layups. This method utilizes two transducers, a transmitter and receiver in a pitch-catch mode, fixed at the same oblique angle. The flow patterns for multi-ply laminates were mapped, and a global view of the ply directions was obtained. A frequency analysis of the ensuing signal showed that selective imaging of the fiber orientations in a multi-layered composite is feasible.