A Semi-theoretical criterion based on the combination of strain energy release rate and strain energy density concepts (STSERSED): Establishment of a new approach to predict the fracture behavior of orthotropic materials

ABS TRACT Motivated by previous research performed by the authors assessing the fracture behavior in orthotropic materials under mixed-mode I/II loading, this article aims to propose a novel Semi-theoretical criterion for desired crack -fiber angles to assess the fracture of composite materials. Contrary to all previously proposed fracture criteria, in this criterion a mid-point experimental data related to the mixed-mode I/II loading is employed instead of mode I fracture toughness. Utilizing an arbitrary combination of mixed-mode I/II experimental data leads to a signifi-cantly simple and accurate fracture assessment criterion. More accurate estimation is achieved using more experimental data in mixed-mode I/II. For the first time, due to the importance of providing a fracture criterion, a Semi-theoretical criterion based on a combination of Strain Energy Release Rate (SER) and Strain Energy Density (SED) criteria, namely STSERSED, is adopted for more accurate anticipating of the fracture of orthotropic materials. Using SED criterion, mode I fracture toughness is theoretically derived and substitutes in the equations of maximum strain release rate. Furthermore, fitting mid-point experimental data into the presented criterion compensate the portion of wasted energy due to the creation of Fracture Process Zone (FPZ) and therefore more accurate fracture estimation is possible. With the passage of pure mode I and the emergence of mode II, the effects of FPZ increase, so changing the critical point from pure mode I to mid-point experimental data makes the extracted fracture behavior closer to the experimental data. Due to using experimental data and the relevant theoretical criterion simultaneously, this criterion can be used in engineering applications to extract the crack behavior of orthotropic materials. The verification of the STSERSED criterion is evaluated by comparing the fracture limit curves (FLC's) with the available experimental data. The extracted results based on the proposed criterion highlight the achievement of this criterion to assess the fracture of orthotropic materials.