Numerical Prediction of Failure Load of Scarf-Patch-Repaired CFRP Composite Using Damage Zone Model and Cohesive Zone Model

A numerical study was conducted to investigate the tensile behavior of carbon fiber-reinforced polymer (CFRP) scarf-repaired structures with different scarf ratios (1/5, 1/10, 1/20, and 1/30) using two approaches associated with the finite element method (FEM): the damage zone model (DZM) and cohesive zone model (CZM). The experimental data of CFRP laminates with the stacking sequence [45/ − 45/ − 45/0/90/0/45/ − 45/90/0]S, an over-ply layer (additional ply covering the outermost layer of the scarf-patch-repaired structure), and four different scarf ratios were obtained and analyzed. First, an empirical formula was established to describe the mathematical relationship and correlation between the failure load and scarf angle. Subsequently, the strength recovery rate was calculated to evaluate the mechanical performance of the scarf-repaired structures with different scarf ratios. Finally, the experimental data were used to verify the numerical results. The experimental and numerical results exhibited good agreement with each other. The effect of the scarf angle of scarf-patch-repaired composite laminates on the selection of the reference sample in the DZM method and the cohesive parameters in the CZM method were discussed as well.