Star Crack Formation via Low-Velocity Impact on Glass Windows

The resistance to crack formation induced by gravel impacts on laminated glass windshields is a crucial issue for windshield manufacturers. It is proposed to study the star crack formation on polyvinyl butyral (PVB) laminated glass by designing a new highly-instrumented device that can break the glass under dynamic loading. The set-up is composed of a spring-loaded projectile that mimics a gravel momentum and an input bar equipped with strain gauges, whose end is an indenter initially in contact with the laminated glass sample. A synchronized high-speed camera allows for the observation of the crack growth. A unidimensional model introduces the local non-linear behavior of the indented zone. Crack monitoring synchronized with the Force and Velocity measurements are presented. Live-indentation depth measurements are performed. Experimental results are used in a dynamic simulation to analyze the non-linear damage behavior under the indenter tip. Dynamic and well-instrumented indentation experiments on the laminated glass are performed to investigate the star-shaped crack formation and describe the indented zone. This work is a prelude to the crack length prediction on windshields submitted to gravel pitting.