This work aims to characterize the dynamical behavior of a multilayered beam with imperfect interfaces thanks to an equivalent model. The imperfect interfaces studied in this work are sliding interfaces, which is written as a discontinuity of the transverse displacement field. The latter is depending on the coupling conditions of the layers. These effects are modelled thanks to a spring approach. A high stiffness implies a good coupling, conversely, a low stiffness implies a bad coupling between the layers. Such modelling is implemented in an equivalent dynamic model, then it is used to characterize experimental samples. These samples are characterized by dynamical parameters computed by fitting the measurement with the model, such as the equivalent flexural rigidity or the equivalent damping in bending. The samples are sandwich beams with aluminum skins and a viscoelastic core (epoxy). They are manufactured in order to have a decreasing quality of the coupling within the multilayered beam to use the model on different coupling conditions and compare the results. The experimental setup is a vibration measurement thanks to a Laser Doppler Vibrometer (LDV), and a piezoelectric buzzer to make the sample measurement vibrate. Then, Corrected Force Analysis Technique (CFAT) is used to process the data. Finally, equivalent flexural rigidity is computed thanks to the velocity measured and is fitted by the model to characterize the interface coupling.