Investigation of the parameters that influence the accuracy of bond defect detection in CFRP bonded specimens using IR thermography

Infra-red (IR) testing has emerged as a promising non-destructive method (NDM) to detect and effectively observe bond defects in composite materials. This paper presents the findings of an investigation of carbon fiber-reinforced polymer (CFRP) fabrics and laminates externally bonded to concrete and steel members. Various kinds of artificial bond defects at the CFRP-substrate bond surface were investigated in specimens with single- as well as multi-layer CFRP fabrics. Particular emphasis was placed on the use of different heating modules in the IR nondestructive testing. This was implemented by generating different thermal waves within the CFRP-substrate bond surface. The results show that substrate material type and methods of surface preparation have a marked influence on the type of heating modules that produce the best detection capability. The results also show that the number of CFRP layers has a considerable effect on the effectiveness of bond identification and the accuracy of the IR images.