Mechanistic understanding of the fracture toughening in chemically strengthened glass—experiments and phase-field fracture modeling

The use of silicate glass in engineering applications has become widespread in recent years due to its superior mechanical and optical properties. However, glass, being a brittle material, poses extremely poor resistance against fracture. Chemical strengthening through ion-exchange has emerged as a promising technique to improve its fracture resistance. In this study, the relationships between chemical strengthening parameters and the resulting fracture toughness of chemically strengthened (CS) glass are investigated using experiments, analytical and numerical simulations. Our results show that optimal fracture resistance for a CS glass requires a proper combination of chemical strengthening parameters, namely the surface compressive stress (σ_CS), and depth of the compression layer (DOL). The present study establishes the fact that unlike glass, the fracture toughness (K_IC^CS) of a CS glass is not a constant material parameter, instead depends on the initial crack/notch length. The experimental data have also been supported with analytical calculations based on linear elastic fracture mechanics and numerical simulations based on the phase-field fracture theory. These findings provide a novel understanding towards the fracture toughness improvement of CS glass, which should facilitate their widespread engineering applications.