Air-coupled laser ultrasonic testing of glass fiber reinforced polymer defect

Glass Fiber Reinforced Polymer (GFRP) composites are widely used in aerospace and other fields due to their excellent material properties. However, defects generated during the production and usage phases can greatly affect the stability and safety of the GFRP composites. Traditional non-destructive testing methods have certain limitations when they are applied to the internal defect detection of GFRP composites with anisotropic and layered structures. To address the material inspection challenges of GFRP, we have developed a laser ultrasonic inspection system based on a low-frequency air-coupled ultrasonic probe that can retain the high resolution of the laser ultrasonic inspection system with low-cost and high robustness of the air-coupled ultrasonic probe. In this paper, using a hybrid system combining the advantages of laser ultrasound and air-coupled ultrasound inspection, different types of minor defects in glass fiber reinforced composites were non-contact detected using a low-frequency air-coupled ultrasonic probe at 450 kHz, and the results were compared with those of contact ultrasound phased array inspection. The results show that the use of the hybrid system can effectively achieve low-cost, non-contact, high signal-to-noise ratio and high accuracy detection of the shape, size and location of defects in GRFP composites.