Head impact evaluation onto conventional tempered glass and laminated glass car windows in side impact and rollover accidents
The occupant injuries in the side impact crash and rollover are more severe than those in frontal impacts as the occupant is partially or fully ejected through the side window and comes in contact with foreign objects such as poles, trees, other vehicles, etc. Since ejections are mainly caused by failure of side window glass conventionally made of tempered glass, the vehicle side window glass is increasingly being replaced with laminated glazing by the automotive industry. Laminated glass does not break upon impact and helps in keeping the occupant from ejecting out of the car in side impact or rollover. In this research, the impact injury potential to the human head is studied and quantified for both tempered glass and laminated glass windows. First, the finite element (FE) models of tempered glass and laminated glass are developed in Hypermesh. These FE models are quasi-statically tested with a hybrid III dummy free-motion head-form (FMH). Force versus displacement graphs are plotted and validated with the results obtained from a physical static experiment. A series of impact test simulations are conducted on both tempered and laminated glass with the H-III FMH at varying impact speeds. Acceleration and the head injury criteria (HIC) values are determined for each impact test simulation. The simulations clearly indicate that the tempered glass fails upon impact and the FMH ejects; however the laminated glass does not break and contains the FMH. A second series of impact test simulations involve a FE model of a rigid pole placed behind the two glass types to study the secondary head impacts. The results show that the tempered glass breaks and allows head to strike the pole with high head injury potential, whereas the laminated glass contains the head. Based on the results, this study demonstrates the laminated glass acts as a shield between the occupant and the surrounding objects and protects the occupant from ejecting.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.