Simulating delamination in composite laminates with fracture process zone effects: A novel cohesive zone modeling approach

In this paper, a novel cohesive zone modeling (CZM) approach is presented to simulate the crack initiation and propagation of mixed mode I/II delamination in laminated composites, with a focus on the effects of the fracture process zone. The CZ model employs a novel approach that combines linear and torsional spring elements to calculate the material's residual strength within the fracture process zone along the delamination growth path. In this model, the stiffness of springs changes based on the normal and tangential traction-separation curves. Unlike previous models, this approach considers the effect of all toughening mechanisms in the fracture process zone and softening behavior of the material's traction-separation curve. Also, the application of this model to estimate the R-curve behavior is demonstrated. In this way, an analytical relationship has been presented for changes in crack growth resistance with crack length increase for mode I and mode II loadings. This relationship calculates the fracture initiation toughness, the energy dissipation from toughening mechanisms in the fracture process zone, and the steady-state fracture toughness using only the potential energy of the linear and torsional elements of spring. Comparison of the obtained R-curve with experimental data highlights the efficacy of this new model.