The Internal Tensile Strength of a Borosilicate Glass Determined from Laser Shock Experiments and Computational Analysis

It is of interest to determine the internal tensile strength of glass because it is used in material models to understand and design transparent armor. It is difficult to determine this strength because surface conditions limit the ability to apply large tensile stresses needed to cause internally located crack initiation. This article presents a novel approach to estimate the internal tensile strength of glass using a combination of laser shock experiments and computational analysis. Laser shock produces a unique loading condition that causes maximum tension to occur in the interior of the glass without destroying the target. Several laser shock experiments were performed on a plate of borosilicate glass at varying levels of peak pressure. In one experiment, damage was produced only in the interior of the plate (there was no damage on either the front or rear surfaces). This experiment was singled out for analysis because surface flaws did not influence the internal crack initiation event. Computational analysis indicated that the internal tensile strength of this borosilicate glass is approximately 1.2GPa. The computed results produced damage only in the interior of the glass plate, similar to experimental observation. A similar failure stress was obtained using the Griffith criterion.