Fracture of silica aerogels: An all-atom simulation study

Silica aerogels are highly nano-porous and fragile solids, which exhibit brittle properties under tensile loading. In this work, molecular dynamics simulations with a model size up to 5.07 million atoms have been performed to investigate the effect of the crack length to height ratio on the fracture strength, fracture toughness and strain energy release rate. For a wide range of densities from 295 to 1155 kg m−3, we demonstrate that the fracture toughness and the strain energy release rate at the onset of the crack propagation increase with the crack length to height ratio. Moreover, these fracture properties were found to exhibit a power law dependence on the aerogel density with exponent values of 2.02 ± 0.05 for the fracture toughness and 1.16 ± 0.04 for the strain energy release rate. The investigations presented grant a more comprehensive understanding of the fracture behavior and provide a mechanistic basis for reliable applications of silica aerogels.