Debonding detection of defected CFRP-concrete interface using active microwave thermography

Abstract

This study presents an investigation of non-destructive evaluation (NDE) of carbon fiber reinforced polymer (CFRP)-concrete interfacial debonding using a novel technology referred to as active microwave thermography (AMT). AMT utilizes microwave energy as a heating excitation to the structure and captures the anomalies of temperature contrast (TC) at the structure surface using a thermal camera. In this study, AMT was used first as an inspection method of CFRP-concrete joints. Comparative tests on CFRP-concrete joints with and without an initial man-made defect showed AMT can detect initial defects at the CFRP-concrete interface in around 15 s. Then, AMT was used to monitor the time-history progressive interfacial debonding process of the CFRP-concrete joints tested in direct shear under monotonically increasing loading. The test results showed that: (i) the initial defect at the CFRP-concrete interface can be detected by AMT quickly; (ii) the presence of an initial defect at the CFRP-concrete interface can substantially decrease the load-carrying capacity of the CFRP-concrete joint; (iii) the initial defect can alter the interfacial debonding process and global load response; and (iv) significant load drops, indicative of interfacial damage formation, could be detected by a change of slope of the local CFRP surface TC determined by AMT.