Numerical study of surface fatigue crack growth in steel plates repaired with CFRP

•• A Python-based FE method is developed for automated surface fatigue crack modelling.•• Validation of the FE method is conducted analytically and experimentally.•• CFRP repair can effectively enhance the fatigue life of surface cracked steel plates.•• Repair effects improve with CFRP equivalent stiffness but not with crack aspect ratio.•• Single-sided CFRP repair outperforms double-sided CFRP repair in efficiency. This paper presents a numerical study of the fatigue behaviour of carbon fibre-reinforced polymer (CFRP) repaired steel plates with a surface crack under uniaxial cyclic tension. A simulation programme for surface fatigue crack propagation has been developed by means of Abaqus-Python scripting. Validation of models was first performed analytically and experimentally, through evaluation of the stress intensity factor (SIF) and fatigue life of unrepaired specimens, respectively. The developed programme was then used to simulate the fatigue behaviour of surface cracked specimens repaired with CFRP sheets. Different aspect ratios of surface cracks, numbers of CFRP layers, CFRP sheet widths and types and CFRP repair schemes (i.e. single- and double-sided reinforcement) were considered, to assess their influence on the CFRP repair efficiency. The results showed that applying CFRP sheets could effectively reduce the SIF of the surface cracks, thereby prolonging the fatigue life of the steel plates. Further, the repair performance improved with more and wider CFRP sheets and higher equivalent modulus but remained almost unchanged for different crack aspect ratios, while the single-sided CFRP repair outperformed the double-sided repair in efficiency. The present study is of instructive value for application of CFRP materials to the repair of surface cracked metallic structures.