Characterization of interfacial strength of layered powder-compacted solids

The interfacial strength of nearly planar surfaces between two layers of powder compacted solids produced by sequentially consolidating each layer into a bilayer solid was characterized. In this study, fracture mechanics principles were applied to evaluate the mechanical fracture strength of bilayer compacts. The fracture toughness (a measure of materials resistance to fracture when a crack is present) for the bilayer interfaces (KI) was evaluated in samples with a relatively sharp crack introduced during the manufacturing process. This experimental methodology has been utilized to understand and quantify the effect of power properties and process parameters on the mode I fracture strength. In particular, investigations were carried out to understand the impact of physico-mechanical properties of the powders, deformation histories of the layers, and compression process parameters on the interfacial stress intensity factor of the bilayer compacts. It has been observed that these factors have a strong impact on the fracture toughness of the bilayer interface crack. Results indicated that for both the plastic and brittle material compacts, interfacial fracture toughness is dependent on layer forces and layer sequence. Compacts made with brittle materials in the first layer offered better resistance to crack propagation compared to the compacts having plastic materials in the first layer. The combination of interfacial roughness and interfacial radius of curvature strongly influenced the ability of the interfaces to resist crack propagation. For the bilayer compacts with plastic material in the first layer, fracture toughness exhibits higher sensitivity to interfacial radius of curvature than roughness. However, in the case of bilayer compacts with brittle material in the first layer, dependency of stress intensity factor (SIF) is higher on interfacial roughness compared to the interfacial radius of curvature.