Phase-field ductile fracture analysis of multi-materials and functionally graded composites through numerical and experimental methods

Despite extensive studies on material models for fracture applicable to homogenous materials, the demand for advanced numerical methods to predict the failure in multi-materials and functionally graded materials (FGMs) remains substantial. This study aims to address this gap by using a phase-field approach for analyzing crack development and ductile fracture in FGMs via numerical and experimental methods. To account for the failure induced by material plastic deformations, we introduce the elastoplastic material framework within the damage driving force. This framework enables us to analyze fracture in the FGM setting, whereby the gradual spatial changes of the elastoplastic and fracture properties across the functionally graded medium are modelled by considering the effective property values calculated via rule of mixtures. The influence of the gradation profiles and orientations on the problems of crack initiation, propagation, and fully-developed crack pattern is elucidated via mixed-mode crack analyses on a representative numerical example. In particular, the fracture resistance changes resulting from the property mismatches between the constituent FGM materials are assessed. To determine the efficacy of the numerical model in predicting the fracture behavior, it is evaluated against the experimental tensile test data obtained from miniaturized tensile test specimens excised from an FGM block consisting of 316L and IN718 powders, deposited via Laser powder blown Directed Energy Deposition (LDED).