Characterization of Wall-Loss Defects in Curved GFRP Composites Using Pulsed Thermography

Curved glass fiber–reinforced polymer (GFRP) composites are superior to alloy-steel pipes due to their excellent corrosive resistance properties, finding wide applications in the transportation of petrochemicals, chemical storage tanks, and power and water-treatment plants. Among the defects found in GFRP pipes, internal pitting or wall loss is one of the most severe, caused by material deterioration and the friction of small particles in the transfer fluid. This study investigates these in-service discontinuities using a pulsed thermal nondestructive evaluation technique. The paper focuses on the quantification of defect depth using the temperature peak contrast derivative and defect sizing using the full width at half maximum method. Further, the paper investigates the ability of pulsed thermography to estimate pitting or wall-loss defects at various depths and sizes through simulation and experimentation. Thermographic signal reconstruction images are used for quantification of defects at a deeper depth. The results of the present study are then compared with well-established ultrasonic C-scan results.