A new method and instrument is discussed for dynamic air permeability testing of airbag fabrics. This new method provides for much more representative test results as the commonly used static, low pressure air permeability test. The use and significance of the dynamic air permeability and air permeability curve exponent are explained for both, the airbag system designer and the airbag fabric designer.
1. CURRENT METHOD FOR DETERMINATION OF THE AIR PERMEABILITY
Undoubtedly, the air permeability is one of the most important properties of airbag fabrics, and to ensure the proper function of the airbag, it is necessary to control this fabric property both accurately and regularly.
The standard method for determination of the air permeability of airbag fabrics is the same as the one being used for determination of the air permeability of other industrial fabrics. This method determines the velocity at which air passes through the fabric at a given pressure differential across the fabric. Such tests can easily and quickly be conducted with commercial air permeability testers, such as the Textest FX 3300 Air Permeability Tester.
Unfortunately, the various test standards used internationally do not prescribe the same test parameters. Consequently, the test results obtained using different test standards do not agree. More important, they cannot easily be compared with each other or converted into each other, if the test methods prescribe different test pressures, which is almost always the case. Figure 2 shows the test parameters prescribed by the most important test standards used for determination of the air permeability of airbag fabrics.