  Zero-Group Velocity (ZGV) Lamb waves are studied in a structure composed of
two plates bonded by an adhesive layer. The dispersion curves are calculated
for a Duralumin/epoxy/Duralumin sample, where the adhesion is modeled by a
normal and a tangential spring at both interfaces. Several ZGV modes are
identified and their frequency dependence on interfacial stiffnesses and on the
bonding layer thickness are numerically studied. Then, experiments achieved
with laser ultrasonic techniques are presented. Local resonances are measured
using superimposed source and probe. Knowing the thicknesses and elastic
constants of the Duralumin and epoxy layers, the comparison between theoretical
and experimental ZGV resonances leads to an evaluation of the interfacial
stiffnesses. A good agreement with theoretical dispersion curves confirms the
identification of the resonances and the parameter estimations. This
non-contact technique is promising for the local evaluation of bonded
structures.
