Nondestructive characterization of mechanical properties on metallic and polymer plates using hybrid laser-air coupled ultrasonic techniques

Ultrasonic non-destructive techniques have been extensively used in various applications such as material characterization to extract important properties of materials. This work presents a non-contact hybrid system which integrates laser ultrasound and air-coupled transducer for generation and detection of guided waves. Furthermore, by adjusting the air-coupled transducer for an estimated angle, A₀ S₀ Lamb modes and longitudinal waves was detected in aluminum, stainless steel, and epoxy resin plates. Subsequently, the experimental measurements of dispersion curves are computed and Young’s modulus, thickness were calculated using inversion technique. Results show that the error percentage of Young’s modulus and thickness was about 7.60% and 9.26% for aluminum plate while the steel plate showed with 3.98% and 3.58%. Besides, the error percentage of Young’s modulus and thickness was about 4.05% and 5.88% for epoxy resin plate. The obtained experimental measurements were in good agreement with inversed material properties, which verified that the hybrid laser-air coupled ultrasonic technique can prove that the system is feasible, and the accuracy can be improved in the future to measure the material properties and geometrical character of metallic and polymer plates.