ASTM_D_6476_-_12.pdf

Designation:D647612Standard Test Method forDetermining Dynamic Air Permeability of Inflatable RestraintFabrics1This standard is issued under the fixed designation D6476;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the procedures used to deter-mine under dynamic airflow conditions the high pressurepermeability of permeable,uncoated fabrics typically used forinflatable restraints.For the determination of air permeabilityof inflatable restraint fabrics under low pressure conditions atsteady-state air flow,refer to Test Method D737.1.2 Procedures and apparatus other than those stated in thistest method may be used by agreement of purchaser andsupplier with the specific deviations from the standard ac-knowledged in the report.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D123 Terminology Relating to TextilesD737 Test Method for Air Permeability of Textile FabricsD1776 Practice for Conditioning and Testing TextilesD2904 Practice for Interlaboratory Testing of a Textile TestMethod that Produces Normally Distributed Data(With-drawn 2008)3D6799 Terminology Relating to Inflatable RestraintsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 For all terminology relating to D13.20,Inflatablerestraints,refer to Terminology D6799.3.1.1 The following terms are relevant to this standard:average dynamic air permeability(ADAP),dynamic air per-meability(DAP),cushion,exponent of dynamic air permeabil-ity(EXP,)inflatable restrain,inflator,module,standard atmo-sphere for testing textiles3.2 For all other terms related to textiles,see TerminologyD123.4.Summary of Test Method4.1 A volume of dessicated compressed air at known vol-ume and pressure passes through a fabric specimen into thestandard atmosphere for testing textiles.During the portion ofthe test cycle which simulates airbag inflation,the pressuredifferential pressure across the specimen rises to a valuecorresponding to a peak inflation pressure.During the portionof the test cycle which simulates airbag deflation,the pressuredifferential drops to 0 kPa as the air passes through thespecimen.The time to reach the maximum pressure and thesubsequent time to correspond to similar times in an airbagdeployment.4.2 Software algorithms integral to the apparatus smoothout the pressure data and determine the values for ADAP andEXP.5.Significance and Use5.1 For matters relating to lot acceptance of commercialshipments and conformity to specification or other standard,refer to Section 13 of this test method.5.2 This test method is useful in the selection and designvalidation of permeable,uncoatable fabrics used in inflatablerestraint cushions.The dynamic conditions and higher pressuredifferentials of this test method may better simulate theinflation and deflation cycle of an airbag module duringdeployment than do the steady-state conditions of Test MethodD737.5.2.1 Only uncoated,permeable fabrics should be used.Useof coated fabrics may yield invalid results and potentiallydamage the test apparatus.1This test method is under the jurisdiction ofASTM Committee D13 on Textilesand is the direct responsibility of Subcommittee D13.20 on Inflatable Restraints.Current edition approved July 1,2012.Published August 2012.Originallyapproved in 2000.Last previous edition approved in 2008 as D647608.DOI:10.1520/D6476-12.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.3 Within the limits of variance expressed in Section 12,this test method is useful for design validation and may besuitable for incorporation in a material specification or for lotacceptance testing of commercial shipments.Caution is ad-vised on very low permeability fabrics or with the 200 cm3.size test heat because between-laboratory precision as pre-sented in Section 12 may be as high as 21%.5.4 This test method may be used for materials other thaninflatable restraint fabrics which experience dynamic air per-meability in sudden