Effect of adhesive on the performance of piezoelectric elements used to monitor structural health

The effect of adhesive thickness and its modulus on the performance of adhesively bonded piezoelectric elements for the purpose of monitoring structural health has been experimentally investigated. All the piezoelectric elements were adhesively bonded to aluminum plates. Experimental results revealed that an increase in adhesive thickness alters the electromechanical impedance and the resonant frequency of the piezoelectric elements as well as the amplitude of the sensor signal. When the modulus is within a certain range, the modulus of adhesive slightly affects the impedance of PZT element and the amplitude of sensor signal at lower frequency, while at high frequency, the impedance response and sensor signal are more sensitive to the modulus of adhesive.