Structural transformations in porous glasses under mechanical loading. I. Tension

Abstract

The evolution of porous structure and mechanical properties of binary glasses under tensile loading were examined using molecular dynamics simulations. We consider vitreous systems obtained in the process of phase separation after a rapid isochoric quench of a glass-forming liquid to a temperature below the glass transition. The porous structure in undeformed samples varies from a connected porous network to a random distribution of isolated pores upon increasing average glass density. We find that at small strain, the elastic modulus follows a power-law dependence on the average glass density and the pore size distribution remains nearly the same as in quiescent samples. Upon further loading, the pores become significantly deformed and coalesce into larger voids that leads to formation of system-spanning empty regions associated with breaking of the material.

Structural transformations in porous glasses under mechanical loading. II. Compression

“…In our previous study, it was demonstrated that the distribution of pore sizes in the absence of deformation is well described by a scaling relation at small length scales and the average glass density ρσ 3 0.8 [18]. In agreement with our previous studies [18,20], the variation of the elastic modulus as a function of the average glass density follows a power-law increase with the exponent of 2.41…”

“…It was shown that PSDs are narrow at high glass densities and they become broader as the average glass density decreases; various features of PSDs were discussed in the same reference. In the past, we have also investigated evolutions of PSDs in porous glasses undergoing shear [19] and tensile [20] loadings. This allows for a comparative analysis of the data, obtained on different types of mechanical loading.…”

“…Following the preparation protocol used in the previous studies [16][17][18][19][20], the system was first equilibrated at constant volume during 3 × 10 4 τ . At this stage, the temperature of…”

“…In both cases it was found that the porous structure becomes significantly modified due to pore redistribution and coalescence into large voids upon increasing strain [19,20]. The analysis of local density profiles during tensile loading showed that necking develops in the low-density regions leading to an extended plastic strain and ultimate breaking of the material [20].…”

“…Interestingly, it was shown that the pore-size distribution functions obey a single scaling relation at small length scales for systems with high porosity, while the local density of the solid phase remains relatively insensitive to the total pore volume [18]. Later studies have examined the dynamic response of porous glasses subjected to either steady shear [19] or tensile [20] deformation.…”