Influence of residual stress on the fracture behavior of phase-separated glasses: A molecular dynamics study

Phase-separated glasses are being explored for industrial applications due to their unique microstructure and potential for improved fracture toughness compared to homogeneous glasses. Residual stresses form, e.g., due to differences in thermal expansion among the phases, but the influence of these stresses on the fracture behaviour remains unclear. In this work, we use molecular dynamics simulation to investigate the effect of residual stress on the fracture behavior of droplet-type phase-separated soda-lime-silica glasses. Different residual-stress states are introduced by adjusting the density of the glassy silica droplet phase embedded in a soda-lime-silica glass matrix. In the phase-separated glasses, we find that both tensile and compressive residual stresses can lead to a reduction in fracture toughness. As such, our findings suggest that residual compressive stress does not necessarily improve fracture toughness in heterogeneous glasses. As the droplet density increases, the residual stress state within the droplets shifts from tensile to compressive, which fundamentally alters the fracture mechanism. This transition is characterized by a shift from crack propagation preferentially penetrating the droplets to a matrix-dominated fracture mode. Overall, the study underscores the importance of explicitly accounting for residual stress states in the design of phase-separated or glass-ceramic composite systems, suggesting that optimized crack-path engineering requires careful control of both microstructure and residual stress.