A novel optical air-coupled ultrasound NDE sensing technique compared with infrared thermographic NDT on impacted composite materials

In this paper, a novel optical air-coupled ultrasound (O-ACU) technique is proposed. A wide broadband (100 KHz - 1 MHz) laser-acoustic based optical microphone worked as probe in an air-coupled ultrasound (ACU) system. The O-ACU modality was used to detect several CFRP and GFRP impacted laminates and the results were compared with the classical ACU modality. Infrared thermography, as an established reference technique, was used for the validation. Advanced image processing techniques were applied. Conclusively, O-ACU shows an obvious improvement in sensibility and resolution.