Characterization, modeling, and design of airbags and woven expansible fabrics

Airbag technology relies on woven fabrics as the material of construction. Knowledge pertaining to the fabric's permeability as a function of pressure drop and inflating gas temperature under biaxial conditions is crucial from an energy dissipation point of view. An expansible fabric stretched biaxially will tend to open up and become more permeable. The extent to which fabric porosity changes with temperature, pressure drop, polymeric fiber source of the fabric, fabric weave, fabric finish and fabric denier is difficult to determine a priori. However, these material properties of the fabric significantly contribute to the safety of the vehicle occupant as he/she interacts with the deployed airbag.; In order to quantify these parameters, a novel blister-inflation technique was developed to deform a fabric biaxially. Three different types of polymeric fabrics woven from nylon 6,6, nylon 6 and high strength polyester fibers with various constructions and finishes were investigated in this study. A highly reliable fabric material model (FMRM) for biaxial deformation was developed based on the semi-empirical approach called artificial neural networks.; The role played by the four different mechanisms in overall energy dissipation in an airbag was modeled based on the kinetic energy changes which occur as the occupant interacts with the airbag (KEAM). The KEAM model highlights the various mechanisms and the synergistic role they play on energy dissipation. Finally, energy dissipation of an airbag made from a particular fabric was related to the airbag volume required for safe operation.; These two models, FMRM and KEAM, were then integrated with a passenger restraint action model (PRAM) that was developed for investigating the restraint action of the occupant on impact. PRAM is a numerical simulation model for investigating interaction forces experienced after impact between the airbag and the occupant. The prediction of this model has shown good agreement with experimental sled and dummy data.; Finally, the possibility of using fabrics made of discontinuous fibers, such as cotton, was also investigated. On the basis of the understanding of the overall phenomena and the variables affecting them, a new generation of fabrics called 'Smart-fabrics' that would behave in a desired manner are being hypothesized.