Application of laser-based ultrasound to the inspection of contoured parts [reinforced polymer composites]

To realize the full high-speed scanning potential of a same-side laser-in/laser out inspection system, it is necessary to angularly deflect the generation and detection laser beams across the part surface. The authors have investigated the variations in the detected ultrasonic signal amplitude in reinforced polymer composite (RPC) materials resulting from varying the angle of incidence of the laser beams from 0 to 45°. These studies have been made on a variety of RPC materials having various surface textures and coatings. The results show that several commonly used paints significantly enhance the diffusive component of the reflected light, thus increasing the signal amplitude obtained for large angles of incidence. Even for uncoated specimens the decrease in signal amplitude at large angles is within the dynamic range of a suitably designed laser-based ultrasound system