Delamination detection in composite laminates using high-frequency P- and S-waves - Part II: Experimental validation

In this work, the delamination detection procedure presented in part I is experimentally investigated (Pasquali and Lacarbonara, 2015). Attention placed on the through-the-thickness propagation direction of composite laminates undergoing delaminations. As observed in the numerical tests, a precise correlation between the delamination position and the variations of the Time of Flight (ToF) of primary (P) and secondary (S) waves is found. A substantial modulation of the power spectral density (PSD) of the acquired output signals is recorded in the case of delaminations close to the surface onto which the actuator/sensor transducers are bonded. The experimental validation of the proposed SHM procedure is carried out through extensive testing on different types of isotropic and composite specimen. A good agreement between the experimental results and the theoretical predictions shown in part I [1] is found, together with determination of limitations on the delamination position offset with respect to the actuator-sensor pair position.