Abstract
There are two established but fundamentally different empirical approaches to parametrize the rate of subcritical fracture in brittle materials. While both are relying on a thermally activated reaction of bond rupture, the difference lies in the way as to how the externally applied stresses affect the local energy landscape. In the consideration of inorganic glasses, the strain energy is typically taken as an off-set on the activation barrier. As an alternative interpretation, the system’s volumetric strain-energy is added to its thermal energy. Such an interpretation is consistent with the democratic fiber bundle model. Here, we test this approach of concerted activation against macroscopic data of bond cleavage activation energy, and also against ab initio quantum chemical simulation of the energy barrier for cracking in silica. The fact that both models are able to reproduce experimental observation to a remarkable degree highlights the importance of a holistic consideration towards non-empirical understanding.
Highlights
The chemistry of glass fracture has been under scientific debate for a long time (Fairbarn and Tate, 1859; Griffith, 1921)
A quantitative description of the underlying mechanisms of crack propagation, critical to the further development of crack-resistant glasses, is presently unavailable (Wondraczek et al, 2011; Freiman, 2012). This is largely due to the fundamental nature of cracking as it occurs in the broad group of brittle oxides, and especially in glassy silicates: crack propagation reflects a complex and, as of yet, not fully understood interplay of chemical and physical interactions (Ciccotti, 2009)
This interpretation is a natural result of the democratic fiber bundle model (DFBM), in which the material is represented as a series of springs connecting two parallel bars and oriented perpendicular to the direction of crack propagation
Summary
The chemistry of glass fracture has been under scientific debate for a long time (Fairbarn and Tate, 1859; Griffith, 1921). A quantitative description of the underlying mechanisms of crack propagation, critical to the further development of crack-resistant glasses, is presently unavailable (Wondraczek et al, 2011; Freiman, 2012). This is largely due to the fundamental nature of cracking as it occurs in the broad group of brittle oxides, and especially in glassy silicates: crack propagation reflects a complex and, as of yet, not fully understood interplay of chemical and physical interactions (Ciccotti, 2009). Parametric knowledge is needed for the focused development of new material compositions and toughening procedures and for enabling better time-to-failure estimations (Freiman et al, 2009). For the case of molecular water as the reaction partner, a theoretical framework has been
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