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Deployment of an airbag or charging of a tank by an inflator-canister system is a highly dynamic process. Quantification of energy storage, energy flux, work done, flow rates, thermodynamic properties, and energy conservation are essential to describe the deployment process. The concepts of available work and entropy production are presented as useful parameters when evaluating airbag aggressivity from tank test results for different types of inflators. This paper presents a computational methodology to simulate a pyro- and a hybrid-inflator-canister-airbag system to predict the force pattern that could occur on an out-of-position occupant when the airbag deploys. Comparisons with experimental data have been made in all cases where data were available. These include driver-, passenger-, and side-airbag designs.

The evaluation of the performance of a particular inflator for the design of the entire airbag system is typically carried out by examining the pressure pattern in a standard tank test. This study assesses the adequacy of the tank test as a true measure of the likely performance of the actual inflator-airbag system. Theoretical arguments, numerical experiments, and physical experiments show that the time rate of pressure change may be an appropriate measure to evaluate performance of a specific type of inflator, particularly if variations in the inflator design maintain the same working gas components. However, when evaluating and comparing the dynamic behavior between different types of inflators, the time rate of pressure change provides useful but incomplete information.