Numerical modelling of bond behaviour between steel and CFRP laminates with a ductile adhesive

Ductile adhesives are more appropriate than brittle adhesives for steel structure strengthening by adhesively bonding carbon fibre reinforced polymer (CFRP) due to its greater strain capacity, leading to larger loading and deformation capability. This paper investigated the bond behaviour of CFRP-to-steel joints bonded with a ductile adhesive via numerical studies. Single lap pull tests were also conducted, and the load-displacement relationship at the loaded end and the strain distribution along the CFRP plate were examined. A bond-slip relationship was derived from the test, and based on this, an isosceles trapezoid bond-slip model was proposed. A finite element model was developed for FE analysis of the bond behaviour of the CFRP to steel interface by using the proposed bond-slip model. The finite element model was used to model the experiments, and the good agreement between the experimental results and numerical results demonstrate the effectiveness and accuracy of the finite element model. Finally, a systemically parametric analysis was performed to investigate the effect of FRP modulus, adhesive equivalent strain, adhesive tensile strength and adhesive thickness on initial stiffness, effective bond length and ultimate load. Finally based on the numerical results, a model of effective bond length was proposed.