Noncontact Laser-Induced Ultrasound for Composites Inspection: Approaches for Material Discontinuity Visualization

Abstract

Pulsed laser techniques enable non-contact generation of ultrasound in composite materials and can provide full-wavefield data. Nonetheless, since a pulsed laser provides a broadband excitation of acoustic waves, the resulting field contains both the dominant propagating modes and the weaker signals caused by interactions with possible internal defects such as delaminations. Hence, proper analyses of wavefields become essential to reveal subtle phenomena that can be masked by the primary wavefronts. In this study, the Singular Value Decomposition is applied to the measured wavefield to effectively separate and suppress the main wave components, whereas time-integrated maps are computed to enhance the discontinuity visualization. Experimental results from a composite plate with artificial interlaminar defect demonstrate that the adopted processing approaches improve defect contrast and facilitate more accurate localization of subsurface delaminations.