Atomistic aspects of dynamic fracture in a variety of brittle crystalline, amorphous, nanophase, and nanocomposite materials are reviewed. Molecular dynamics (MD) simulations, ranging from a million to 1.5 billion atoms, are performed on massively parallel computers using highly efficient multiresolution algorithms. These simulations shed new light on (a) branching, deflection, and arrest of cracks; (b) growth of nanoscale pores ahead of the crack and how pores coalesce with the crack to cause fracture; and (c) the influence of these mechanisms on the morphology of fracture surfaces. Recent advances in novel multiscale simulation schemes combining quantum mechanical, molecular dynamics, and finite-element approaches and the use of these hybrid approaches in the study of crack propagation are also discussed.

International audienceThis paper is devoted to a comparison of experimental, simulation, and theoretical results on the density of SiO 2 – B 2 O 3 –Na 2 O glasses. It is found that theoretical and simulation densities do compare favorably with experimental values yet simulations give a better estimate of the density of the samples. Furthermore, the structural make-up (i.e. types of borate and silicate units) of the ternary glasses and the volume of the elementary units have also been investigated with simulations and compared to theory

International audienceThis study investigates the mechanical response of sodium borosilicate (SBN) glasses as a function of their chemical composition. Vickers's indentation tests provide an estimate of the material hardness (H V) and indentation fracture toughness (K C VIF) plus the amount of densification/shear flow processes. Sodium content significantly impacts the glass behavior under a sharp indenter. Low sodium glasses maintain high connected networks and low Poisson's ratios (ν). This entails significant densification processes during deformation. Conversely, glasses with high sodium content, i.e. large ν, partake in a more depolymerized network favoring deformation by shear flow. As a consequence , indentation patterns differ depending on the processes occurring. Densification processes appear to hinder the formation of halfpenny median–radial cracks. Increasing ν favors shear flow and residual stresses enhance the development of halfpenny median–radial cracks. Hence, K C VIF decreases linearly with ν