Interaction of the primary anti-symmetric Lamb mode (Ao) with symmetric delaminations: numerical and experimental studies

Abstract

The interaction of an ultrasonic guided Lamb wave mode with delaminationtype defects in a quasi-isotropic laminated composite plate has been studied,using both simulations and experiments. In a laminated composite platewith a symmetric delamination, when the primary anti-symmetric mode,Ao, is incident at the entrance and exit of a delamination, it generates a new mode,So, that is confined only to sub-laminates and undergoes multiple reflections in thedelaminated region. It was observed that only the incident and mode-convertedAo modes propagate in the main laminate. The two modes reverberate between the two endsof the delaminations while undergoing multiple mode conversions, leading to a trail ofsignals that is captured by the finite element model. The numerical observations werevalidated using experiments conducted using air coupled ultrasonic transducers.