Modeling of Alumina-Epoxy Joints Reinforced by Functionally Graded Materials, Using Finite Element Method

Application of functionally graded materials (FGM''s) to join materials with extremely different thermo-mechanical properties can reduce sharp interface stresses caused by weak chemical affinity and high residual stress concentration. So، if the functionality of gradient regions be designed properly، it can minimize the failure probability due to unstable crack propagation. It has been shown that if the material gradient is parallel to the crack، the asymmetric stress field results in mixed-mode fracture and crack deviation for its initial direction. Mixed-mode stress intensity factors (SIF''s) and phase angle are computed by finite element method for a four-point-bending problem assuming functionally and multi-layered gradient regions. In order to obtain an optimum design، the effect of slope and breadth of gradient region، crack geometry، and residual stress field on fracture parameters (including SIF''s and phase angle) are studied. Minimum value of complex stress intensity factor is obtained per 2. 25 for profile power and 9 mm for width of gradient region.