1、Designation: D6476 12 (Reapproved 2017)Standard 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 rev
2、ision, 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
3、 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
4、 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 purp
5、ort 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:2D12
6、3 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 Inf
7、latable 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 per
8、meability (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 dessicat
9、ed 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 infla
10、tion 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 algorit
11、hms 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 i
12、s 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 stea
13、dy-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 of ASTM Committee D13 on Textilesand is the direct responsibility of Subco
14、mmittee D13.20 on Inflatable Restraints.Current edition approved Feb. 1, 2017. Published March 2017. Originallyapproved in 2000. Last previous edition approved in 2012 as D647612. DOI:10.1520/D6476-12R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Se
15、rvice 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 Co
16、nshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade
17、Organization Technical Barriers to Trade (TBT) Committee.15.3 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-vi
18、sed 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 b
19、ursts. In such cases, the physical appa-ratus or its software algorithms may require modification toprovide suitability for use.5.5 Due to the split-second time interval for testing, thepressure versus time data is subject to recording anomalies andelectronic noise. The data should be digitally filt
20、ered to obtainthe underlying smooth pressure curve prior to data analysis.The software in the apparatus includes a reliable algorithmboth to smooth the curve and to determine the exponent of airpermeability.5.6 It is inherent in the design and operation of thisequipment that major components key to
21、the calibration andmeasurements are specific to the individual test head. The sizeor permeability measuring range of the test head is typicallychosen to correspond to the fabric specimen to be tested. Theprecision of this test method is highly dependent on the size ofthe test head. The precision of
22、the data collected using one testhead should be used to estimate the precision of data collectedusing a different test head, even on the same apparatus.5.7 It is mandatory that fabric specimens be conditioned andtested in standard atmosphere for testing textiles.6. Apparatus6.1 Removable Test Head,
23、containing a Pressure Vessel ofknown volume capable of being charged pneumatically from 0to no less than 400 kPa with a tolerance of 6 3.0 %, ofsufficient volume to challenge adequately the fabric beingtested, equipped with a solenoid release valve mechanism, atest chamber, and a circular orifice wi
24、th an area of 50 cm2; andequipped with a means of measuring and adjusting the pressurerange in increments of 1 kPa, a minimum range betweenpressure set points of 5 kPa and rise and fall ranges in mssufficient to meet the conditions of a material specification fordynamic air permeability testing of i
25、nflatable restraint fabrics.6.2 Pressure Transducers and Rigid Wall Pickup Tubes,suitable for measuring the pressure differential of the fabricspecimen in a range sufficient to meet the conditions of amaterial specification for dynamic air permeability testing ofinflatable restraint fabrics, with a
26、tolerance of 6 2 %, mountedin a static or low pressure area in the test fixture that does notinterfere with airflow.6.3 Air Compressor and Air Desiccating Cartridge, capableof charging the pressure vessel in the test head to the specifiedpressure up to 400 kPa.6.4 Mounting Fixture, capable of retain
27、ing the fabric speci-men over the test orifice without stretching the specimen andwithout air leakage at the periphery of the test area.6.5 Electrical Firing Pulse Source, suitable for actuating theinflation and for communicating with the data acquisitionsystem dependent on an electrical signal.6.6
28、Data Acquisition System, suitable for recording theoutput of the pressure transducers versus elapsed time ofairflow.6.7 Filter Requirements, data sampling rate, transducerfrequency response, and amplifier frequency response shall besuch that minimal effect on accuracy of the data occurs. Theaccuracy
29、 of the pressure transducers, amplifiers, and timerswithin the test apparatus shall be calibrated to within 6 3%.7. Sampling7.1 Dynamic air permeability testing is a destructive testand therefore necessitates sampling procedures if used inconjunction with lot acceptance of commercial shipments.7.2 L
30、ot Sample:7.2.1 For acceptance testing, the lot size is the quantity offabric finished in one production day or as agreed uponbetween the purchaser and the supplier.7.2.2 Unless otherwise agreed upon between the purchaserand the supplier, take as a lot sample all the rolls in acommercial shipment. C
31、onsider the rolls to be the primarysampling units.7.3 Laboratory Sample7.3.1 An entire roll of fabric or a full-width cut from the endof a roll within a lot sample constitutes a laboratory sample.7.4 Test Specimens:7.4.1 Test specimens are the pieces of fabric that actuallyundergo testing. Cut or ma
32、rk specimens from the end of eachroll of fabric in the laboratory sample, as indicated in thematerial specification or equivalent. Cut 165 by 330 mmrectangular specimens from the full-width fabric sample, ormark similarly sized areas across the full-width fabric samplewithout cutting individual spec
33、imens.7.4.2 If areas of full width fabric are tested without cuttingindividual specimens, position test areas representing a broaddistribution across the length and width, preferably along thediagonal of the laboratory sample, and no nearer the edge thanone tenth its width.8. Conditioning8.1 Precond
34、ition test specimens in accordance with PracticeD1776 or as agreed upon between the the purchaser and thesupplier.8.2 Prior to testing, bring the test specimens to moistureequilibrium at ambient atmospheric pressure, at 21 6 1C, andat 65 6 2 % relative humidity, unless directed to do otherwiseby an
35、agreement by the purchaser and supplier.8.3 Equilibrium is considered to have been reached whenthe increase in mass of the specimen in successive weighingsmade at intervals of not less than 2 h does not exceed 0.1 % ofthe mass of the specimen.9. Procedure9.1 Select and condition specimens in accorda
36、nce with 8.1.D6476 12 (2017)29.2 Mount the fabric specimen on the test fixture, ensuringthat the retention mechanism clamps the fabric tightly withminimal tension and without damage or wrinkling.9.3 Perform all system calibrations.9.4 Enter the specimen number into recording portions ofthe data acqu
37、isition.9.5 Ensure the pressure vessel is pressurized with desiccatedair to a pressure sufficiently high to test the specimen within thepressure ranges specified.9.6 In accordance with the applicable material specificationor laboratory guideline, select and install the appropriate testhead for the f
38、abric type to be measured.9.7 Preset the start, upper, and lower pressure limits.9.7.1 Unless otherwise stated in the customer specification,the test head size, and starting pressure should be selected suchthat an average peak pressure of 100 6 10 kPa is reachedduring the test. Also unless otherwise
39、 stated in the customerspecification, the Lower Limit should be set to 30 kPa and theUpper Limit should be set to 70 kPa.9.8 Establish data acquisition system response to pressureinputs.9.9 Initiate the starting sequence and note the response ofthe data acquisition system to verify successful airflo
40、w.9.10 Record maximum differential pressure in kPa, time tomaximum pressure in ms, or whatever data points are requiredby the material specification.9.11 Remove the specimen from the test stand and mark itas having been tested.9.12 On the test report, record the data required by thematerial specific
41、ation.NOTE 1The unit of permeability commonly used for ADAP measure-ment is mm/s. A velocity of 1 mm/s is the mathematical equivalent of apermeability of 0.1 cm3/(cm2.s). Permeability and velocity are consideredinterchangeable terms.10. Equipment Calibration10.1 For inflatable restraints, all test e
42、quipment used inaccordance with these test methods shall be certified forcalibration annually by an independent agency or equipmentmanufacturer whose results are traceable to the NationalInstitute of Science and Technology (NIST) or other nationalstandards laboratory. The test parameters of the equi
43、pmentshall be tested within the operating ranges covered in thematerial specification or equivalent document.11. Report11.1 State that the tests were conducted in accordance withthis test method for determining the dynamic air permeabilityof inflatable restraints fabrics.11.1.1 If deviation from thi
44、s test method occurred, anyreference to this test method shall state: “Testing was per-formed in accordance with ASTM D6476, with the followingchanges:”11.2 The purchaser and supplier shall determine the exactform of the test report. Unless otherwise specified, report thefollowing information:11.2.1
45、 Fabric designation,11.2.2 Lot identification,11.2.3 Date of report,11.2.4 Name of person certifying report,11.2.5 Relevant specification,11.2.6 Number of specimens used in each test,11.2.7 Tests performed and data obtained,11.2.8 Laboratory conditions if other than standard, and11.2.9 Deviations fr
46、om standard procedures and apparatus.12. Precision and Bias12.1 BiasFor multifilament fabrics such as those used forinflatable restraints, there is no standard reference materialavailable to serve as an accepted standard value for dynamic airpermeability testing. In the absence of a known true value
47、, theaccuracy of this test method cannot be determined.12.2 The analysis of precision of test results using this testmethod is meaningful both within-laboratory and between-laboratory with multiple operators.12.3 An Interlaboratory Test4was planned and conductedon uncoated fabrics covering a range o
48、f permeabilities typi-cally used in inflatable restraint cushions in accordance withPractice E691 and Practice D2904. For inflatable restraintfabrics, the typical range of permeabilities is between zero and10 cfm when measured in accordance with Test Method D737.Two variables, ADAP and EXPONENT were
49、 studied.Analysiswas done using SAS 6.1, PROC. GLM, and PROC.VARCOMP. Three components of variance - single-operator,within-laboratory, and between-laboratory - were statisticallycalculated to determine precision of this test method.12.4 Precision of ADAPFor the components of variancelisted in Table 1, two averages of observed values should beconsidered significantly different at the 95 % probability levelif the difference equals or exceeds the critical differences listedin Table 212.4.1 Primary source of variance of ADAP is betweenlaboratories.12.4.2 The critical differences for
