An Approach to Simulate the Residual Strength of Initially Damaged Laminated Safety Glass with LS-DYNA

Since March 2011, a newly released Federal Motor Vehicle Safety Standard 226 Ejection Mitigation (FMVSS 226) shall help to reduce the complete or partial ejection of vehicle occupants through side windows during rollover or side impact accidents. The rules apply to laminated safety glass windows - sandwich structures made out of polyvinyl butyral - foil and regular glass panes and have to be verified experimentally by car manufacturers from the year 2017 onwards. To be able to evaluate or even predict the experimental results with finite element analysis (FEA), a simulation model is built representing the material and structural behavior of the laminated safety glass during the testing procedures which include the impact of a regular head impactor at different velocities and positions on pre- damaged side windows. The main challenge for the model development is the consideration of a specific crack pattern on the in- and outside of the window given by a center punch procedure prior the impact test. In a first approach to understand the material behavior, full vehicle experiments are replaced by a simplified drop testing procedure. According to the FMVSS 226 rules, different velocities and impact positions are considered. In addition, a frame-like structure is built representing the constraints of a side window in a full vehicle testing procedure. During the model development different modeling techniques, element types and material models are tested. To analyze the dependency of the simulation results and the chosen mesh, different element sizes and orientations are considered. The simulation results gained with the finite element software LS-DYNA are compared with the experimental drop test results performed with three different side window geometries.