Application of Ultrasonic Thermography in the detection of delamination in the Glass Fiber Reinforced Plastics

In the present research, the applicability of active thermography using ultrasonic excitation in detecting delamination defects has been investigated experimentally. In this regard, a Glass Fiber Reinforced Plastic (GFRP) Sample was prepared via the hand layup method. PTFE sheet pieces were considered delamination defects located inside the sample. The delamination defects were considered in the three different sizes. Moreover, three delaminations with similar sizes were placed in three different depths. The ultrasonic excitations were conducted using a Piezoelectric PZT transducer. The excitation frequency was adjusted to a constant value. The ultrasonic thermography inspections were performed with three different excitation powers. The sample was constrained in the fixed-fixed mode. The thermography inspections were carried out with three various excitation times. Results indicated that the defect of a maximum size has been detected in all inspections. Moreover, in order to enhance the detectability a trade-off of excitation power and excitation time should be selected.