Study On The Dynamic Permeability Of Airbag Fabrics

The permeability of airbag fabrics is one of the most important factors influencing the reliability of the airbag. Therefore, it is essential to measure and evaluate the permeability of the airbag fabrics precisely. The accepted standards for measuring fabric permeability have been recognized not ideal for airbag fabrics, as they were designed to measure clothing, tent fabric, parachutes working under relatively low pressure . The operating pressure of airbag fabrics is much higher than the value prescribed in the conventional standards. Moreover, the conventional methods are quasi-steady-state measurements and not suitable for the airbag impacted by the dynamic gas. The thesis focuses on the investigation of the measurement of the dynamic permeability of airbag fabrics.A new method is proposed for measuring the dynamic permeability of airbag fabrics. The measuring arrangement is composed of a driver chamber and a driven chamber separated by a polyester diaphragm. An airbag fabric sample is clamped at the end of the open driven chamber. When the driver chamber is charged with air to a pressure, the diaphragm ruptures. Meanwhile the air in the driver chamber discharges into the driven chamber and a high pressure is built up in the driven chamber very quickly. And then the pressure decreases gradually due to the permeable structure of airbag fabrics. The air permeability of the airbag fabric is thus determined by measuring the pressure trace in the driven chamber.Secondly, the relationship between the dynamic permeability of the airbag fabrics with the pressure drop through the fabric is investigated experimentally and the influence of the structure parameters . on the dynamic permeability is discussed. The results show the dynamic permeability of airbag fabrics increases linearly as the pressure drop increases. The denser the fabric is or the finer the filament is, the lower the permeability is.Thirdly, the dynamic permeability and the static permeability are compared. Both the dynamic permeability and the static permeability increases as the pressure drop increases. The dynamic permeability presents linear correlation with the pressure drop, while the static permeability has a non-linear relation with the pressure drop in whole. The dynamic permeability of airbag fabrics is lower than that the static permeability under a same pressure drop.Finally, the dynamic deformation of the airbag fabric impacted by high pressure gas flow is measured by the high speed camera and the stress-strain relationship is analyzed accordingly. In the dynamic deformation of the airbag fabric, the inflation height of the fabric increases linearly as the pressure increases. The relationship of the stress and the strain of the airbag fabric are non-linear in whole.