Detection of disbonds in adhesively bonded aluminum plates using laser-generated shear acoustic waves

• Main Authors: Patrycja Pyzik, Aleksandra Ziaja-Sujdak, Jakub Spytek, Matthew O’Donnell, Ivan Pelivanov, Lukasz Ambrozinski
• Format: Article
• Language: English
• Published: Elsevier 2021-03-01
• Series: Photoacoustics
• Subjects: Laser ultrasound; Shear waves; Adhesive bonds; Inverse filter
• Online Access: http://www.sciencedirect.com/science/article/pii/S2213597920300653

Adhesively bonded metals are increasingly used in many industries. Inspecting these parts remains challenging for modern non-destructive testing techniques. Laser ultrasound (LU) has shown great potential in high-resolution imaging of carbon-reinforced composites. For metals, excitation of longitudinal waves is inefficient without surface ablation. However, shear waves can be efficiently generated in the thermo-elastic regime and used to image defects in metallic structures. Here we present a compact LU system consisting of a high repetition rate diode-pumped laser to excite shear waves and noncontact detection with a highly sensitive fiber optic Sagnac interferometer to inspect adhesively bonded aluminum plates. Multiphysics finite difference simulations are performed to optimize the measurement configuration. Damage detection is performed for a structure consisting of three aluminum plates bonded with an epoxy film. Defects are simulated by a thin Teflon film. It is shown that the proposed technique can efficiently localize defects in both adhesion layers.