<p>Despite significant progress in developing mixed-mode I/II fracture criteria for orthotropic materials, many existing criteria still fail to fully consider the complexities of the fracture process zone (FPZ) and the arbitrary crack-fiber angles. This research addresses these limitations by developing generalized mixed-mode I/II fracture criteria for orthotropic materials. The proposed criteria are based on the concepts of minimum strain energy density and maximum strain energy release rate, which are combined with the reinforcement isotropic solid model. Including the non-singular term (T-stress) in the calculations improves the accuracy of crack growth predictions. Furthermore, based on these proposed criteria, an expression for the equivalent mode I fracture toughness is developed, which can be used to calculate the fracture toughness for any given crack orientation in orthotropic materials. The validity of the proposed criteria is evaluated through comparisons with available experimental data for wood species and composite materials. The results show that the newly proposed criteria offer more accurate predictions of material fracture behavior compared to classical criteria. The new approach, which includes the FPZ effects together with T-stress, provides a more realistic representation of crack growth in orthotropic materials under mixed-mode I/II loading conditions.</p>