Non-destructive examination of GFRP composite parts using active microwave thermography with water spraying

Abstract In this paper, in an attempt to non-destructively evaluate the Glass Fiber Reinforced Plastic (GFRP) composites, active thermography with microwave excitation is employed. Different types of defects including holes and cracks with different sizes were located in GFRP samples as well as specimens produced from PVC foams. Active Microwave Thermography (AMT) tests were performed from two different distances and with two different power levels. Moreover, the enhancement of detectability by the application of water spraying on the surface of the samples was investigated. The results indicated that active microwave thermography has better performance in the detection of holes compared with cracks. The application of water spraying significantly enhanced the detectability of surface cracks in the GFRP composites and PVC foam samples. Finite Element Analysis was employed to numerically simulate the microwave heating of the GFRP samples and evaluate the temperature variations. Statistical analyses were carried out to investigate the effect of test parameters on the detectability of defects. The statistical analysis results indicated that the heating time has a superior influence on the temperature contrast and detectability.