Microstructure-based modelling and experimental investigation of crack propagation in glass–alumina functionally graded materials

The aim of the present work was the determination of the fracture mechanisms in glass–alumina functionally graded materials (FGMs). The investigation was performed by means of a combined approach based on microscale computational simulations, which provided for an accurate modelling of the actual FGM microstructure, and experimental analysis. The numerical results proved that microstructural defects, such as pores, deeply influenced the damage evolution. On the contrary, the minimization of the mismatch in the coefficients of thermal expansion of the ingredient materials allowed to obtain low thermal residual stresses, which did not relevantly affect the crack propagation. In order to support the numerical model, microindentation tests were performed on the cross-section of FGM specimens and the experimentally observed crack paths were compared to the computationally predicted ones.