Controlled crystallization of certain glasses leads to structured materials, designated glass-ceramics (GC), which consist of nano or microcrystals dispersed in a residual glass matrix. GC take advantage of beneficial ceramic and glass properties and have numerous applications to our daily lives, e.g., cookware, bone and dental implants, architecture, cell phone displays, etc. However, the ageing of these materials, namely how their properties evolve and potentially degrade in time is not understood. Ageing can severely restrict GC´s uses due to slow crack propagation leading to the failure of the GC under (apparently) harmless stresses. We aim to predict the fracture properties of GC of two common GC compositions in research today with potential applications ranging from dental works to transparent GC for various structural applications. Atomic level simulations are extremely valuable as they are able to quantify and qualify different phenomena in the wake of a crack front (including local structural rearrangements); however, they are limited due to system sizes and boundary conditions, which cause complications with pure mode I fracture. Recently, we have developed and tested protocols to implement these techniques via the CAPRICCIO method. Based on this tool, we will attempt to predict the evolution of the mechanical properties of GCs under mechanical loading.