Modelling the age-related decrease in ballistic limit velocity of polycarbonate vision panels using a Johnson-Cook material model coupled with variable failure criteria

Machine tools are equipped with polycarbonate vision panels that allow the operator to observe the machining process and protect him from ejected fragments. Adequate protection is demonstrated by impact tests. However, polycarbonate is subject to aging processes, which diminish the protective performance of such panels. This paper presents an approach for modelling aging effects on the ballistic limit velocity of polycarbonate using Finite Element simulations. A Johnson-Cook material model in conjunction with variable failure criteria was used for the simulations. Aging effects on the ballistic limit velocity were included in the model by adjusting the failure criteria. Material parameters and failure criteria were derived from experimental impact and tensile tests on unaged and aged polycarbonate specimen. The numerical results predict the ballistic limit velocity with a maximum deviation of 0.98%. The model provides a more in-depth understanding of the aging effects on the safety performance of polycarbonate vision panels.