An Experiment-Simulation Method for the Determination of the Mode-II Critical Energy Release Rate

To overcome the harsh experimental conditions of determining the mode-II critical energy release rate G_IIC, a flexible experiment-simulation method for determining G_IIC is proposed based on the mixed-mode fracture experiments and the corresponding simulations by the mixed-mode phase-field model. In details, a mixedmode fracture experiment is first conducted to obtain the initial crack deflection angle. Subsequently, a series of phase-field simulations are conducted by altering the value of G_IC/G_IIC to reproduce the experimental result so as to determine the value of G_IIC with a known G_IC. Three mixed-mode fracture tests (single edge cracked circular test, central crack rectangular tension test and compact tension shear test) of PMMA indicate that the determined G_IIC is a stable material parameter independent of test and loading conditions. Meanwhile, the determined prediction of GIIC is compared with those in other references with a deviation of about 3.5%, which demonstrates that the proposed method can quantitatively and qualitatively obtain G_IIC. Furthermore, the determined parameter G_IIC is used to develop the mixed-mode phase-field model through using the mode-mixity factor (G_IC/G_IIC) to regular the relative contribution of the volumetric and distortional crack driving energy. As a result, the mixed-mode phase-field model provides better simulations than the classical phase-field model for the materials with large difference between G_IC and G_IIC. Without the harsh conditions of the pure mode-II fracture, the proposed method is of significant practice in the determination of G_IIC, which benefits the study of mixed-mode fracture problems.