Elasticity and strength of silica aerogels: A molecular dynamics study on large volumes. (15th February 2018)

• Record Type: Journal Article
• Authors: Gonçalves, William; Morthomas, Julien; Chantrenne, Patrice; Perez, Michel; Foray, Geneviève; Martin, Christophe L.
• Is Part Of: Acta materialia. Volume 145(2018)
• Page Start: 165
• Page End: 174
• Publication Date: 2018-02-15
• Subjects: Silica aerogels -- Mechanical behavior -- Nanoscale -- Molecular dynamics; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2017.12.005
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: The nanoporous structure and the mechanical properties of silica aerogels are studied by molecular dynamics simulations on large samples. For the first time, atomistic simulations are able to reproduce a pore size distribution, centered on 10 nm, comparable to experimental values. Using an unprecedented combination for silica aerogels of large volumes, large strains, and relatively small strain-rates, direct evidence of their peculiar mechanical behavior at the nanoscale is provided, from elasticity to fracture. The surface stress that silica ligaments experience produces a significant tension-compression asymmetry and an unusual discontinuity in the Poisson effect. The ductility of highly porous silica aerogels arises from an interplay between surface stress and a significant amount of reorganization in ligaments. Taking advantage of the large volumes accessible here, the very heterogeneous nature of low-density silica aerogels is reproduced, with an impact both on their elasticity and on their strength. In particular, a clear dependence between tensile strength and sample volume is uncovered, which opens perspectives for the elaboration of multi-scale models. Graphical abstract: Image 1