Investigation of equivalent CFRP delamination defect samples for infrared nondestructive testing based on VATCP

In the research of infrared non-destructive testing (IR NDT) technology, the effectiveness of prefabricated defects is a crucial factor. This paper proposes a new method based on the vacuum-assisted thermal curing process (VATCP) for prefabricating delamination defects of carbon fibre reinforced polymer (CFRP) composites. This method simulates delamination by inserting a thin film with air-like thermal resistance between carbon fiber plies. Long-pulse excitation infrared non-destructive testing experiments and defect characterisation were conducted on the equivalent specimens to verify the rationality of the specimen design. This study proposes polyurethane (PU) as a new simulation material. Combined with the experimental and simulation methods, a systematic comparative analysis was conducted on the thermal response differences between several materials and real air delamination defects. Using multi-dimensional evaluation criteria, the reliability of polyurethane and polytetrafluoroethylene in simulating delamination defects was assessed. Results across these multiple analytical dimensions indicate that the thermal response characteristics of PU-simulated defects in CFRP most closely resemble those of air. Finally, the detection capability was quantitatively evaluated using long-pulse thermography combined with post-processing algorithms.