Debonding strength of steel joints strengthened using strand CFRP sheets under axial tension

Strand CFRP sheets have the unique features of containing factory impregnated CFRP strands and having the flexibility that make strand sheets suitable for strengthening circular hollow sections along the longitudinal direction. Sufficient gaps are designed between the strands that can be easily filled with epoxy resin during a wet layup process. These features make strand CFRP sheets a promising alternative to conventional CFRP materials in strengthening metallic structures. In these applications, proper bonding between steel and CFRP is vital. Therefore the debonding mechanism and debonding strength are of interests to many researchers. In this study, strand CFRP sheets, with a nominal Young's modulus of 430GPa, were used for the connection of double trap steel joints. Tensile tests were conducted to investigate the bonding behaviour and bond strength. Different failure modes were observed for specimens with and without a primer layer. The bond strength and measured stresses in the bond region were compared with those reported by previous researchers.