Laminated composite materials are formed by laminating two or more layers of the same or different materials. Due to the excellent mechanical properties

laminate composite materials are widely used in aerospace and navigation fields. However

during the production and service stage

defects such as disbond and delamination between

layers have greatly affected the stability of component. Currently

the commonly used contact ultrasonic testing has limitations such as large blind area

small field of view

many artifacts and water coupling. Combining the advantages of laser ultrasound and air-coupled ultrasound

a non-contact laser ultrasonic testing system consisting of eight elements 250 kHz air-coupled transducer is developed to detect thin laminated composite materials with thickness of 0.8 mm metal–carbon fiber and 0.3 mm metal–metal

respectively. The system can not only clearly display multiple disbond defects inside the sample

but also successfully identify micro cavity defects formed by bonding layer indentation and bubbles. The imaging field and SNR are up to 220 mm and 35 dB

respectively. Besides

compared to high-frequency phased array and X-ray testing

the system exhibits excellent imaging contrast

resolution

and sensitivity. The experimental results show that the developed large-field air-coupled laser ultrasonic testing system has broad application prospects in the large laminated composite materials.