Nanomechanical investigation of the interplay between pore morphology and crack orientation of amorphous silica

Abstract

Porous amorphous silica (a-SiO2) is of both fundamental and practical interests, as they exhibit a large specific surface area and tunable porous network. However, the brittle nature of a-SiO2 and the presence of pre-existing cracks at both micro- and nano-scales lead to complex mechanical behavior. In this study, we systematically investigate the effects of pre-existing crack and its orientation on the mechanical properties of a-SiO2 with varying pore shapes using reactive molecular dynamics simulations. We demonstrate that pore shape will primarily influence the Young’s modulus (E) and critical energy release rate (GIC). We further investigate the impact of pore shape and crack orientation by local characterization of the structural parameters. By defining the high stress and inter-mediate regions, the overall mechanical properties are found to be greatly influenced by the pore shape which can be reflected through the spatial distribution of von Mises stress. Overall, GIC is found to increase with the increase of ligament length (also known as pore wall thickness). Meanwhile, the effect of the pre-existing crack on the crack propagation process is confirmed by analyzing the density distribution evolution. These results highlight the interplay between pore morphology and crack orientation in controlling the fracture behaviors in brittle porous materials.