Composite materials such as glass and carbon fibre composites have become popular and the preferred choice in various applications due to their many advantages such as corrosion resistance, design flexibility, high strength and light weight. Combining materials with different mechanical properties make composites more difficult to evaluate where the damage mechanisms for composites are more complex than traditional materials such as steel. A relatively new non-destructive testing (NDT) method known as the electromechanical impedance (EMI) technique has been studied by various researchers, but the damage detection performance of the method on composite structures still requires more investigations before it can be accepted for field application, especially in aerospace industry due to the high standard of safety. In this paper, the detection capabilities and performance of the EMI technique subjected to different PZT attachment methods have been investigated. To this end, glass fibre composite plates with various attachment methods for the sensor have been prepared and detection of common defects such as delamination and crack with the EMI technique under study has been performed. The performance of each attachment method for identifying different damage types has been analysed and finite element analysis (FEA) was carried out for verification of the experimental results.
Keywords: composite materials; crack damage; delamination; electromechanical impedance technique; non-destructive testing.