Effects of composite patches on fatigue crack propagation of single-side repaired aluminum panels

The major concern of this review paper is the effect of crack-front shape on fatigue crack growth of the repaired aluminum panels with single-side composite patches in Mode-I condition. It is experimentally and numerically shown that the crack growths non-uniformly from its initial position along the thickness of a single-side repaired panel and the crack-front shape are an important parameter influencing the stress intensity factor and crack propagation rate. Furthermore, effects of plate and patch thickness on the crack growth life of the repaired panels are investigated. It is shown that the lives obtained from uniform crack growth modeling using unpatched surface results are too conservative and the lives calculated using the mid-plane results are non-conservative by the order of 35–90%. It is also shown that the differences between the lives obtained from the non-uniform crack growth modeling and the experimental results are about 10%. A simple method is also introduced to predict the crack growth life of single-side repaired aluminum panels avoiding the complex crack growth analysis based on the non-uniform crack growth or real crack-front shape modeling. Therefore, the results of even a 2D analysis may be used to estimate the crack growth life of the repaired panels. The obtained results are verified with the available experimental results.