A novel mixed mode fracture criterion for functionally graded materials considering fracture process zone

A new mixed mode I/II fracture criterion based on strain energy release rate theory is proposed for investigating fracture behavior in cracked functionally graded materials. In this study, the crack is assumed to be located along the material gradation and within the brittle side of the material. For the first time in this type of material, the fracture process zone and the energy dissipated in this region are considered to enhance the prediction accuracy of the proposed criterion. The mechanical and fracture properties of the damage zone are characterized using the microcrack density parameter. A novel method for manufacturing functionally graded materials is introduced, offering numerous advantages by controlling the gel time of the resin. The critical mixed mode and pure mode II fracture toughness of the fabricated specimens are determined through three-point and four-point bending tests. A comparison of the experimental data with the fracture limit curve demonstrates the effectiveness of the newly proposed criterion for investigating mixed mode fracture in functionally graded materials.