Elastic properties of glasses: a multiscale approach
Résumé
Very different materials are named 'Glass', with Young's modulus E and Poisson's ratio v extending from 5 to 180 GPa. and from 0.1 to 0.4, respectively, in the case of bulk inorganic glasses. Glasses have in common the lack of long range order in the atomic organization. Beside the essential role of elastic properties for materials selection in mechanical design, we show in this analysis that macroscopical elastic characteristics (E, nu) provide an interesting way to get insight into the short- and medium-range orders existing in glasses. In particular, nu, the packing density (C-g) and the glass network dimensionality appear to be strongly correlated. Networks consisting primarily of chains and layers units (chalcogenides, low Si-content silicate glasses) correspond to nu > 0.25 and C-g > 0.56, with maximum values observed for metallic glasses (nu similar to 0.4 and C-g > 0.7). On the contrary, nu < 0.25 is associated to a highly cross-linked network with a tri-dimensional organization resulting in a low packing density. Moreover, the temperature dependence of the elastic moduli brings a new light on the 'fragility' of glasses (as introduced by Angell) and on the level of cooperativity of atomic movements at the source of the deformation process. (c) 2006 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.