Nondestructive evaluation of structural adhesive bonding using the attenuation of zero-group-velocity Lamb modes

Abstract

A laser ultrasonic method is proposed for the nondestructive evaluation (NDE) of structural adhesive bonding. Zero-group-velocity (ZGV) resonances were generated and detected in five trilayer assemblies composed of two asymmetric aluminum alloy plates bonded with an epoxy adhesive. Cohesive and adhesive defects were introduced to degrade the practical adhesion. The attenuation of the temporal signal of ZGV resonances was found to provide sufficient information to discriminate between strong and weak bonding. Two metrics characterizing the attenuation were identified, which allow us to quantitatively evaluate the differences between the manufactured samples. A 2D scan of a trilayer assembly with different bond defects demonstrates the imaging capability of this all-optical NDE method.