Multi-instrumented dynamic experiments on laminated glass

Laminated glass, a composite made of two or more different glass sheets, interleaved with thin polymeric layers, is a widely used material for building or automotive applications.Used as glazing, laminated glass is designed to insure the user safety by preventing large glass chip ejection during an impact and by dissipating the kinetic energy.The composite response to dynamic loads is therefore a crucial issue to validate the safety of its use through many standards implying a wide variety of tests.Resisting small impacts like graveling is also at stake for such glazings.It is proposed to study the star crack formation by designing a new device. The set-up is composed of a spring-loaded projectile that mimics a gravel momentum and a mini-Hopkinson input bar equipped with strain gauges, whose end is an indenter initially in contact with the sample. A synchronized high-speed camera, used to measure the crack propagation, is combined with the indenter force and velocity measured at the indenter tip.A simulation analyzes the non-linear local behavior accounting for the sample dynamic bending.This work is a prelude to the crack length prediction on windshields submitted to gravel pitting.Hard-body blunt impact are representative of anti-burglary testing.During a ball-drop test, the glass layers are cracked and a global large strain regime, driven by the newly formed polymeric bridges, is activated. A large amount of impact energy is dissipated thanks to the stretching of the interlayer and delamination.To estimate the composite behavior after glass breakage, stereo-digital image correlation analyses, introducing axial regularization, are carried out from high-speed camera images to extract the kinematic information of the sample motion.Leads are proposed to design a predictive model with regards to the observations.Repetitive impacts are also studied as the crack pattern and the delamination history are crucial to evaluate the laminated glass residual resistance.