An investigation on the behaviour of toughened monolithic and layered glass under low velocity impact load

The experiment focused on the large-deformation behaviour of monolithic and laminated toughened glass under high-energy impact (940 J) using a 70 kg mass hemispherical impactor. The study provides a direct comparison of impact resistance between 12 mm monolithic glass (1.22 × 1.22 m size 12 mm) and 15.2 mm laminated glass (3 layer of glass + 2 layer of PVB and each layer having 3.04 mm thickness), highlighting their distinct load-transfer and deformation responses is the novelty of the present study. The resistance offered by the layered glass was found to be 7.44 kN whereas, the average peak impact force on the monolithic target found to be 19.3 kN. It is observed that the resistance of monolithic glass found to be increased by 160% as compared to layered glass. The monolithic glass exhibited brittle failure characterized by the ejection of fine fragments and detachment of large glass pieces, whereas the laminated glass showed a ductile-like response by undergoing significant deformation and retaining the fractured fragments within the interlayer, thereby reducing the risk of injury under impact loading. The peak strain in the monolithic and laminated glass was found to be 51 and 41 micro strain, respectively. The persistence of 29% load at 10,000 μs demonstrates the ability of the laminated system to continue carrying load long after crack initiation, whereas the monolithic glass loses almost all resistance within 4240 μs due to brittle fragmentation. Further the numerical simulation was performed on monolithic glass under different conditions using ABAQUS commercial software considering constitutive behaviour of the glass through brittle fracture model and behaviour of interlayer material is modelled using linear elastic model. The predicted results were found in good agreement with the experimental results. Further, the simulations were performed on monolithic glass considering varying thickness, mass of impactor, velocity and angle of obliquity. On varying mass, the force due to least mass was found more significant, whereas significant increase in force and decrease in displacement was found in case of maximum thickness. It was also observed that a significant increase in displacement against varying velocity of the impactor whereas an increasing angle of obliquity found to reduce the stresses significantly.