MATHEMATICAL MODELLING OF THE EARLY PHASE DEPLOYMENT OF A PASSENGER AIRBAG – FOLDING USING ORIGAMI THEORY AND INFLATION USING LS-DYNA PARTICLE METHOD

Initial evaluation of the particle method for mathematical out-of-position simulations was performed. The evaluation was carried out by means of static inflation and impactor tests. In the out-of-position load case, the occupant is initially positioned very close to airbag module and the interaction airbag-occupant occurs during the early deployment phase of the airbag. Thus a realistic representation of the folding pattern together with an explicit modelling of the gas flow and the non-uniform pressure distribution play an important role. The first folding step of a 3D passenger airbag concerns the flattening to a 2D shape. The method used in this study was based on mathematical origami theory. The method consists of an initial user specification of one or a few main constraint folds. The remaining creases, which are needed to flatten the 3D airbag to a 2D state with a minimum area loss, were generated using the origami theory. The actual flattening was performed by solving a nonlinear optimization problem. The subsequent folding of the flat 2D airbag into a housing module was carried out by commercially available software. In the mechanical impactor tests, the airbag was inflated with chest and head shaped impactors resting on top of the airbag. The tests were modelled using the particle method for the gas flow and the predictions from the models were compared to the results from the mechanical tests. Good agreement between predictions and test results were obtained. Next step will be to evaluate the method by means of airbag inflation with an occupant positioned close to the airbag.