An NDT technique for composite structures using visualized Lamb-wave propagation

This study proposes a non-destructive testing (NDT) technique that visualizes the propagation of ultrasonic waves in solids, including composite laminates. This technique provides a moving diagram of traveling waves through the use of a pulsed laser that scans a test piece. A non-contact scan by the pulsed laser for ultrasound generation with reception at a fixed point enables us to inspect an arbitrarily shaped object and also facilitates easy operation of the measurement system. We applied the proposed technique to the inspection of CFRP laminates and successfully visualized the wave scattering due to impact-induced delamination as well as the propagation of the S₀ and A₀ Lamb modes. We also addressed disbonding detection in a composite skin-stringer structure and concluded that the reliable detection of damage and the advantages of the proposed technique are applicable to inspections of composite structures.