Numerical investigation on surface crack growth in steel plates repaired with carbon fiber-reinforced polymer

Fatigue crack growth is a major challenge to the structural integrity of steel structures. In technical practice, surface cracks are of great importance since cracks in components and structures often exhibit this geometry. Fiber-reinforced polymer (FRP) strengthening technology is a reliable technique to repair cracks in steel structures. Yet the investigation on FRP repairing surface cracks in steel structures is lacking. What’s more, the crack growth might cause crack-induced debonding at the interface of FRP reinforcement, generating negative effects to the reinforcement effectiveness. Unfortunately, there are limited studies in the open literature for this issue. In this paper, we conduct the investigation on surface crack growth in steel plates reinforced with Carbon Fiber-reinforced polymer (CFRP) under tensile load. Three-dimensional finite element models are built to predict the stress intensity factors of the surface cracks. The crack-induced debonding is considered in the finite element analysis by introducing the cohesive zone model and a bond failure criterion. In accordance with Paris law, surface crack growth rate of different models are predicted. The influential parameters of crack-induced debonding are analyzed by means of parametric studies. The results indicate that CFRP reinforcement could significantly decrease the surface crack growth rate, while the crack-induced debonding might generate negative effect on CFRP reinforcement. In addition, the crack-induced debonding is affected by not only the interfacial properties, but also the reinforcement scheme, such as thickness of the adhesive layer, CFRP layer number and its elastic modulus, and the depth of surface cracks.