Two-Term Fracture Approach for the Prediction of Mixed Mode Crack Direction in Functionally Graded Materials

In a two terms approach, the representation of the stress field at the crack-tip consists of the mixed mode stress intensity factors (SIFs) as well as the non-singular term, the so-called T-stress. For the prediction of the crack direction in functionally graded materials, a short beam bend (SBB) containing an inclined pre-crack was considered. The main purpose is to investigate the influence of T-stress on the fracture initial angle under mixed mode conditions. Various specimen combinations were analyzed to generate different opening and shearing modes. Using the displacement field near the crack-tip, the fracture parameters were numerically determined then implemented in a subroutine to evaluate the fracture initial angle by both traditional and generalized maximum circumferential stress criteria. The results showed a difference in the predicted crack initial angle; this difference becomes more noticeable as the mode II becomes dominant which is attributed to the consideration of T-stress.