Monitoring interfacial defects in a composite beam using impedance signatures

A simply supported laminated beam bonded or embedded with a piezoelectric layer, which acts as sensor/actuator, is investigated using the state-space method. Linear spring-like constitutive relations are employed to model the behavior of interfacial bonding defects. The imperfect bonding between the host laminate and the piezoelectric transducer is also taken into account. Numerical results show that the electro-mechanical impedance (EMI) signatures extracted from the piezoelectric layer are very sensitive to the bonding imperfection of composite laminates. The covariance of the simulated data, which is a non-parametric damage index, is also employed to identify the severity of bonding imperfection quantitatively.