Evolution of the crack network in glass samples submitted to brittle creep conditions

A crack network is introduced in glass by quenching heated samples. The sharp variation of temperature at the sample boundaries leads to tensile stresses that nucleate cracks. Then, they propagate in the entire sample. Quenching has been performed at 100, 200 and 300∘C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$300\,^\circ \hbox {C}$$\end{document}. Cracks have been imaged with a scanning electron microscope. A transverse isotropic crack network is observed. Crack length and orientation have been measured. Obtained crack density has been compared to that inferred from elastic wave velocity measurements using effective medium theory. Cracked samples have been then submitted to creep tests. Two samples have been recovered, one before its failure and another after. Our observations show that vertical crack propagation takes place during brittle creep and that tertiary creep leads to a localized failure in a shear plane. The damaged and post-mortem microstructural networks have been documented.