For pedestrian safety in car crashes, estimating the Head Injury Criterion (HIC) in head impact tests on windshields has significant importance. This requires evaluating the acceleration profile experienced by the head impactor over the entire crash duration. In a previous project, a stochastic failure model was developed to accurately simulate the behaviour of windshields up to the point of glass fracture. Automotive windshields are typically made of laminated safety glass (LSG), consisting of two glass layers bonded by a polymeric interlayer made of polyvinyl butyral (PVB). This laminate retains glass fragments post-breakage and provides a residual load bearing capacity. However, characterizing this post-fracture behaviour has not yet been adequately achieved.
A recent research project aims to develop an approach that accounts for the post-fracture behaviour of LSG in numerical simulation. For this purpose, the residual stiffness and load bearing capacity of fractured LSG will be measured on small samples under different strain rates and fragmentation grades. These results will then be incorporated into a numerical model, which will be validated through tests on full-scale windshields. A methodology will be established to predict the fracture pattern across the windshield, which depends on the elastic strain energy in the glass panes. As a first result of the research project, the paper presents the distribution of internal stresses across the windshield. These stresses arise from the production process, particularly the shaping process of the curved windshield, and play a crucial role in determining the fracture pattern. By analysing these internal stresses, the study focusses on insights into the mechanisms influencing glass failure, which is largely governed by the dissipation energy released upon impact.