Shock Tube Testing and Modelling of Annealed Float Glass

Abstract

Failure of glass is dominantly brittle, and is caused by microscopic flaws randomly distributed on the surface. Fracture mainly initiates in these flaws, and this leads to a high variability in the glass strength, which depends on geometry, boundary conditions and loading situation. Consequently, the identification of the fracture strength, in e.g. finite element analyses, is not straightforward. For rapid loading conditions, as for blast loading situations, the glass strength is generally increased because flaws need time to grow into cracks. The current study aims to identify the probabilistic fracture strength of glass plates under blast loading as a function of the plate?s boundary conditions, geometry and loading by using a newly proposed strength prediction model. To validate this model in some measure, 12 blast tests on annealed float glass were performed in a shock tube. As expected, the tests showed a large scatter in fracture strength. The strength prediction model captured the main trends found in the experimental tests, but a closer investigation of the strain rate sensitivity of glass was deemed necessary. Finally, the results from the strength prediction model were used as input in a simulation of annealed float glass under blast pressure in the finite element program IMPETUS Afea Solver. By use of a node splitting technique, the simulations captured the behaviour displayed in the experimental tests to a great extent.