Fracture mode of glass plate subject to low-velocity impact: experimental investigation and finite element simulation

Abstract

An understanding of the impact response of glass plates is important to protect people from injury. We investigated the fracture mode of a float glass plate that fractured under a low-velocity impact and conducted a numerical simulation. First, an impact fracture experiment of a float glass plate was carried out using a dropping weight, and crack development in the thickness direction of the glass plate was observed by a shadowgraph method. Then the numerical simulation was conducted applying two types of material models to the float glass: the Johnson-Holmquist model and the elastic model with tensile pressure failure. The two models were used in a simulation and the results were compared with the experimental result. At an impact velocity of 4.43 m/s, which correspond to the deformation velocity of the glass plate of 6.1 m/s in deflection, simulation with the Johnson-Holmquist model could reproduce the strain response of the glass plate but it could not reproduce the fracture mode of the glass plate. This result implied the limitation of applying the damage model to low-velocity impact for simulating the fracture mode of a glass plate. In the material model with elastic as the constitutive law and tensile pressure failure as the failure model, the simulated fracture strength of the glass plate was the same as the experimental fracture strength, and the fracture mode showed characteristics of the bending fracture mode that was observed in the experiment, although the fracture initiation time of the glass plate was slightly delayed in the strain history. In the low-velocity impact where the influence of inertia was small, the glass plate response could be reproduced easily using the elastic model. The efficacy of the model was confirmed in the simulation result with several deformation velocities. the impact object is large so that the loading area is large, and it is caused by the tensile stress acting on the non-impact surface by bending deformation. Additionally, the range in which breakage occurs is wide. The Hertzian fracture mode occurs when the impact speed is fast, the impact object is small so that the loading area is small, and it is caused by shear stress from the stress concentration on the impact surface. This fracture mode is characterized by a small fracture area and a conical fragment of the Hertzian cone. In our previous study, we conducted a low-velocity impact test of the float glass plate at a colliding velocity of 4.43 m/s. The test result implied that the fracture mode of the glass plate is a mixed-mode of bending and Hertzian fractures under this condition (Kojima et al. 2018). Further study is necessary to investigate how it changes according to the velocity. So far, we also conducted the quasi-static indentation test and the three-point bending test to observe the fracture mode of the float glass. It was confirmed that the glass was fractured in the bending mode in quasi-static conditions. The trapezoidal crack which is the characteristic of the Hertzian mode fracture did not appear (Momo...

Numerical Simulation on Dynamic Fracture of Glass Plate Fitted with Polymeric Film

“…1. The model was one-quarter of the planar symmetry built based on the numerical model in the previous study [11] which refers to the experiment in the previous study [9]. Impact load was generated by the collision of the steel ball and the steel incident bar, then it applied to a glass plate through the incident bar.…”

“…Kojima et al quantitatively evaluated the improvement of impact strength by fitting the polymeric film to the glass plate through a drop-weight test [9]. They also clarified the fracture mode of the glass plate fitted with the film subjected to a low-velocity impact by the shadowgraph method with high-speed photography [10]. Owing to these studies, it has been proved that the impact resistance of a glass plate can be improved easily by fitting a thin polymeric film.…”

Effect of shatterproof polymer film application on the fracture types and strength of glass subject to bending load

“…Van Dam et al [19] conducted small-scale drop weight tests using polymer film-applied glass plates and studied in detail how the velocity of the impactor was attenuated. Kojima et al [20,21] quantitatively evaluated the improvement in impact strength when a polymer film was attached to a glass plate by a puncture impact test using a drop weight. In addition, the failure modes of glass plates with polymer films were investigated using high-speed imaging with the shadowgraph method; the glass plates broke in a mixed mode of bending fracture owing to deflection and Hertzian fracture owing to contact with the impactor [22,23].…”

“…Kojima et al [20,21] quantitatively evaluated the improvement in impact strength when a polymer film was attached to a glass plate by a puncture impact test using a drop weight. In addition, the failure modes of glass plates with polymer films were investigated using high-speed imaging with the shadowgraph method; the glass plates broke in a mixed mode of bending fracture owing to deflection and Hertzian fracture owing to contact with the impactor [22,23]. These studies proved that the impact resistance of glass plates can be easily improved by applying a polymer film.…”