Evaluation of Stress Intensity Factor for CFRP Bonded Steel Plates

Recent studies on the application of carbon fibre reinforced polymer (CFRP) materials to defected steel structures have demonstrated the potential for significant reduction of stress intensity factor (SIF) values at crack tips leading to extended fatigue lives. However, most of the previous research relied on experimental and numerical methods, which were either expensive or time-consuming. In this paper, the SIF values at crack tips of steel plates strengthened with bonded composite materials were evaluated using linear elastic fracture mechanics. The analysis was based on the classical solution of SIF values of plain steel plates, considering load share effect and geometry correction factor change resulted from the overlay patch. The effect of different parameters were demonstrated and compared with experimental results, including initial damage degrees of specimens, geometric and mechanical properties of retrofitting materials and bond locations. Good agreement with the experimental data indicated that this approach could conservatively predict the SIF values with reasonable accuracy. A parametric study on variables including the CFRP modulus, the bond width and bond length was conducted based on this method to further investigate their effect on the SIF values.