Higher-Order Continuum Theory Applied to Fracture Simulation of Nanoscale Intergranular Glassy Film

Complex grain-boundary structures such as the 1-2 nm thick intergranular glassy films (IGF) play a prominent role in the failure behavior of nanophased ceramics. The IGF plays the role of an imperfection and serves as the location of strain localization and failure. This paper describes recently performed theoretical mechanical loading experiments on very large atomic models of IGF in silicon nitride using ab initio simulation to obtain their failure behavior. The ab initio simulations yield characteristic postpeak softening accompanied by strain localization zone. This paper applies microstructural granular mechanics-based higher-order continuum theory to model the failure behavior of these types of material systems. The results obtained from the ab initio simulations are compared with those predicted by the higher-order continuum theory.