Effect of elastic properties of material composition on the fracture response of transversely graded ceramic/metal material

The effect of material composition and their elastic properties on the fracture behavior of a transversely graded material is investigated. A single edge notched specimen machined from Ti/TiB graded material with a crack perpendicular to the gradient direction is subjected to three-point bending and the displacement fields on both faces of the sample, Ti and TiB-rich, are obtained using full-field 3D digital image correlation. These displacement fields, along with the asymptotic displacement equation, are used to extract fracture parameters using an overdeterministic least square approach. The displacement fields from a 3D finite element model are also used to calculate the stress intensity factor at each layer throughout the thickness. The variation of stress intensity factor in the gradient (thickness) direction is presented as a function of the elastic modulus of the material. A simple semi-empirical model is also proposed to calculate the stress intensity factor as a function of the material elastic properties at any section along the thickness direction, and to predict the effective fracture toughness of the material.