Simulation of delamination propagation in laminated composites under Mode-I and Mixed-Mode bending with LCZ-Based R-curve cohesive zone modeling

For accurate prediction of the delamination behavior in the case of composite structures, toughening mechanisms like fiber bridging occurring in the fracture process zone (FPZ) must be considered. In this study, the relationship between the fiber bridging (R-curve) and the corresponding FPZ was investigated. Structural size, stacking sequence, and loading were considered in the study of the fiber-bridging behavior of composites. We propose an R-curve expression to estimate the variation of fracture toughness along the FPZ for structures of any configuration under mode-I and mixed-mode loading. These expressions are incorporated into simple bilinear softening laws to model the delamination behavior of any structural configuration under different loading conditions. The proposed methodology is computationally efficient, requiring simple measurements from experiments, such as initial and steady-state fracture toughness values. This eliminates the challenges of the conventional cohesive zone model in modeling large-scale bridging behavior in laminated composite structures. The proposed method was validated for different specimen configurations with variable thickness and cross-ply under mode-I loading. The effect of loading was investigated by subjecting a mixed-mode bending specimen to different mode ratios. The results indicated that the predicted values are in reasonable agreement with the measured values.