On attenuation and measurement of Lamb waves in viscoelastic composites

In this work, the influence of viscoelastic material properties, as featured by fibre reinforced plastics, on the measurement of Lamb waves with the aid of surface-applied piezoelectric sensors is examined. The focus points are frequency dependent material dampening and dispersion on the one hand and the impact of sensor size, wave excitation and measurement method on the other hand. The dependence of the measured wave propagation characteristics and the deviation from the actual characteristics is investigated to assess the relevance for Lamb wave based nondestructive testing and structural health monitoring methods. The sensor responses of piezoelectric sensors bonded to the surface of a viscoelastic composite are predicted by a comprehensive model including these influencing factors. The modelling approach is compared with experimentally measured values to evaluate both the methods and the relevance of the influencing factors.

► Interaction of piezoel. sensors and Lamb waves in viscoelastic CFRP is investigated.
► Sensor responses are predicted while accounting for multiple influencing factors.
► Influence of distance, frequency etc. on apparent TOF and esp. attenuation is shown.
► Qualitative agreement between experiments and predictions is observed.
► Measurements of material property changes need to account for the entire system.