Study of electromechanical impedance changes caused by modifications of CFRP adhesive bonds

Numerous techniques of nondestructive testing and structural health monitoring of CFRP structural parts are studied. In this research, we focus on electromechanical impedance (EMI) technique. This technique is based on a piezoelectric sensor that is surface mounted on or embedded in the inspected structure. Because of direct and converse piezoelectric effects, the electrical response of the sensor is related to mechanical characteristic of the structure. In the reported research, adhesively bonded CFRP samples were investigated. The EMI characteristics of samples with modified bonds were compared with properly bonded referential samples. The following modifications were considered: prebond thermal treatment, prebond contamination with de‐icing fluid, and precuring of the adhesive. The EMI spectra were investigated searching for anomalies and changes caused by modification of the adhesive bonds. Numerical indexes were used for the comparison of EMI characteristics. The sensitivity of the EMI method to modified bonds was observed.