Mixed Mode Crack Initiation and Propagation in Functionally Graded Materials: Experimental and Numerical Investigations

In this study, quasi-static fracture of cracked specimens made of functionally graded material is numerically investigated. As the main contribution and objective of the current work, material property variations in the longitudinal direction are continuously implemented for both of integration points and nodes; therefore, stress field is precisely attained for singular points like crack tip. Furthermore, functionally graded Fe–Cu plates are constructed via a new powder metallurgy method and experimentally tested by three-point bending. Various damage criteria such as maximum principal stress, maximum principal strain, maximum nominal stress, maximum nominal strain, quadratic nominal stress and quadratic nominal strain are employed to predict the crack initiation. Besides, minimum strain energy density (MSED) and maximum tangential stress (MTS) criteria are utilized to reveal the crack growth. To evaluate the mentioned criteria, the numerical results are compared with the experimental tests. The comparison shows that the stress-based criteria are more accurate than the strain-based ones and the MSED criterion has better accuracy rather than the MTS.