Speaker
Stefano Zapperi
(University of Milano)
Description
Glasses represent the quintessential brittle materials and
yet at the nanoscale they become ductile, as experimentally
observed in amorphous silica nanofibers as the sample size
is reduced. I will discuss the results of extensive
molecular dynamics simulations at low and room temperatures
for a broad range of sample sizes, with open and periodic
boundary conditions. Our results show that small sample size
enhanced ductility is primarily due to diffuse damage
accumulation, that for larger samples leads to brittle
catastrophic failure. Surface effects such as boundary
fluidization contribute to ductility at room temperature by
promoting necking, but are not the main driver of the
transition. Our results suggest that the experimentally
observed size-induced ductility of silica nanofibers is a
manifestation of finite-size criticality, as expected in
general for quasi-brittle disordered networks. In the rest
of the talk, I will discuss our recent results on the
plasticity of glasses based on molecular dynamics
simulations and meso-scale models.
