Simultaneous inspection of multi-kind defects in adhesively bonded CFRP/ steel structures by inductive thermography

Carbon fiber reinforced polymer (CFRP) has been widely employed for the reinforcement of steel structures, necessitating the testing of resulting adhesively bonded CFRP/steel structures (ABCSS) to ensure structural integrity and safety. However, the simultaneous detection of multiple types of defects within ABCSS poses significant challenges due to variations in defect characteristics and the intricate effects of these defects on the ABCSS. In this study, we investigate the feasibility of inductive thermography (IT) as a comprehensive inspection method for detecting cracks in steel substrates, debonding, and delaminations in ABCSS. To assess the applicability of IT, we conducted numerical simulations and experimental validation to inspect adjacent and overlapped cracks/interfacial defects in ABCSS. Specifically, we analyzed the electromagnetic and thermal responses of ABCSS during IT inspections, investigated temperature indications associated with various defect types, and examined the underlying causes of these indications. Our results demonstrate that IT can simultaneously reveal distinct temperature indications corresponding to different defect types within the inspected ABCSS. This study establishes the effectiveness of IT in simultaneously detecting multi-kind defects present in ABCSS. The findings contribute to advancing non-destructive testing (NDT) techniques for ABCSS and offer valuable insights into the structural health monitoring of such a special hybrid engineering structure.