Defect Size Characterization in Unidirectional Curved GFRP Composite by TSR Processed Pulse and Lock in Thermography: A Comparison Study

Glass fiber reinforced polymer (GFRP) curved composite is widely used in industries due to its high corrosive resistance nature. GFRP curved composites are involved in many industries like petrochemical industries for handling oil and gas at offshore platforms, chemical processes such as chemical storage tanks, desalination, and water treatment. Since alloy steel materials get corroded by environmental factors such as excess salinity in the surrounding environment, mud deposition, and sulfur crude accumulation makes alloy steel pipes are expensive to maintain. Every year billions of dollars can be saved by corrosion prevention using Glass Fiber Reinforced Polymer (GFRP) pipes instead of alloy steel pipes. In-service stage of the GFRP pipe or tank, different types of defects are forming such as void, delamination, and wall loss (pits). Among all these defects, pits or wall loss is one of the severe defects which may lead to leakage accidents. The objective of the study is the quantification of defect size by using TSR processed pulsed and lock-in thermography and analyses their capabilities in defect size quantification. TSR processed the PT image and the signal to noise ratio was used to estimate the defect size quantification. For defect size measurement, the TSR-processed PT thermal results are recommended and the near-surface defects can be measured with high accuracy in LT.