1、Designation: D 6476 05Standard Test Method forDetermining Dynamic Air Permeability of Inflatable RestraintFabrics1This standard is issued under the fixed designation D 6476; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 pressurepermea
3、bility 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 D 737.1.2 Procedures and apparatus other than those stated in thistest m
4、ethod 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 either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system are not exact equivalents; therefo
5、re, each systemmust be used independently of the other.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
6、 of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 123 Terminology Relating to TextilesD 737 Test Method for Air Permeability of Textile ProductsD 1776 Practice for Conditioning Textiles for TestingD 2904 Practice for Interlaboratory Testing of a Textile TestMethod
7、that Produces Normally Distributed DataD 2906 Practice for Statements on Precision and Bias forTextilesD 6799 Terminology Relating to Inflatable RestraintsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 For definiti
8、ons of other textile and statistical termsused in this standard, refer to Terminology D 123, D 2906 andTerminology D 6799.4. 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
9、. 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 t
10、he 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
11、 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
12、 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 MethodD 737.5.2.1 Only uncoated, permeable fabrics should be used. Useof coated fabrics may yield inv
13、alid results and potentiallydamage the test apparatus.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
14、on very low permeability fabrics or with the 200 cm3.1This test method is under the jurisdiction of ASTM Committee D13 on Textilesand is the direct responsibility of Subcommittee D13.20 on Inflatable Restraints.Current edition approved April 1, 2005. Published May 2005. Originallyapproved in 2000. L
15、ast previous edition approved in 2002 as D 647602.2For 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.1Copyright
16、ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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 e
17、xperience dynamic air per-meability in sudden bursts. 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 andelec
18、tronic noise. The data should be digitally filtered 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
19、 of thisequipment that major components key to 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
20、 on the size ofthe test head. The precision of 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
21、 textiles.6. Apparatus6.1 Removable Test Head, containing a Pressure Vessel ofknown volume capable of being charged pneumatically from 0to no less than 400 kPa (0 to no less than 58 psi) with atolerance of 6 3.0 %, of sufficient volume to challengeadequately the fabric being tested, equipped with a
22、solenoidrelease valve mechanism, a test chamber, and a circular orificewith an area of 50 cm2; and equipped with a means ofmeasuring and adjusting the pressure range in increments of 1kPa (0.1 psi), a minimum range between pressure set points of5 kPa (1 psi) and rise and fall ranges in ms sufficient
23、 to meetthe conditions of a material specification for dynamic airpermeability testing of inflatable 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
24、 specification for dynamic air permeability testing ofinflatable restraint fabrics, with a 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 t
25、he test head to the specifiedpressure up to 400 kPa.6.4 Mounting Fixture, capable of retaining 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 a
26、nd for communicating with the data acquisitionsystem dependent on an electrical signal.6.6 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 freq
27、uency response shall besuch that minimal effect on accuracy of the data occurs. Theaccuracy 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
28、sampling procedures if used inconjunction with lot acceptance of commercial shipments.7.2 Lot 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 t
29、he purchaserand the supplier, take as a lot sample all the rolls in acommercial shipment. Consider 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 Spec
30、imens:7.4.1 Test specimens are the pieces of fabric that actuallyundergo testing. Cut or mark specimens from the end of eachroll of fabric in the laboratory sample, as indicated in thematerial specification or equivalent. Cut 165mm by 330 mmrectangular specimens from the full-width fabric sample, or
31、mark similarly sized areas across the full-width fabric samplewithout cutting individual specimens.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
32、 laboratory sample, and no nearer the edge thanone tenth its width.8. Conditioning8.1 Precondition test specimens in accordance with PracticeD 1776 or as agreed upon between the the purchaser and thesupplier.8.2 Prior to testing, bring the test specimens to moistureequilibrium at ambient atmospheric
33、 pressure, at 21 6 1C (706 2F), and at 65 6 2 % relative humidity, unless directed todo otherwise by an 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 do
34、es not exceed 0.1 % ofthe mass of the specimen.9. Procedure9.1 Select and condition specimens in accordance with 8.1.9.2 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 s
35、ystem calibrations.9.4 Enter the specimen number into recording portions ofthe data acquisition.9.5 Ensure the pressure vessel is pressurized with desiccatedair to a pressure sufficiently high to test the specimen within thepressure ranges specified.D64760529.6 In accordance with the applicable mate
36、rial specificationor laboratory guideline, select and install the appropriate testhead for the fabric type to be measured.9.7 Preset the start, upper, and lower pressure limits.9.8 Establish data acquisition system response to pressureinputs.9.9 Initiate the starting sequence and note the response o
37、fthe data acquisition system to verify successful airflow.9.10 Record maximum differential pressure in kPa (psi),time to maximum pressure in ms, or whatever data points arerequired by the material specification.9.11 Remove the specimen from the test stand and mark itas having been tested.9.12 On the
38、 test report, record the data required by thematerial specification.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. E
39、quipment Calibration10.1 For inflatable restraints, all test equipment 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
40、 nationalstandards laboratory. The test parameters of the equipmentshall 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 permeabilit
41、yof inflatable restraints fabrics.11.1.1 If deviation from this test method occurred, anyreference to this test method shall state: “Testing was per-formed in accordance with ASTM D 6476, with the followingchanges:”11.2 The purchaser and supplier shall determine the exactform of the test report. Unl
42、ess otherwise specified, report thefollowing information:11.2.1 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 Labora
43、tory conditions if other than standard, and11.2.9 Deviations from 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 dynami
44、c airpermeability testing. In the absence of a known true value, 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 Test3
45、was planned and conductedon uncoated fabrics covering a range of permeabilities typi-cally used in inflatable restraint cushions in accordance withPractice E 691 and Practice D 2904. For inflatable restraintfabrics, the typical range of permeabilities is between zero and10 cfm when measured in accor
46、dance with Test Method D 737.Two variables, ADAP and EXPONENT were 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.1
47、2.4 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 bet
48、weenlaboratories.12.4.2 The critical differences for ADAP values as a percentof the ADAP average at the 95 % probability level for singleoperator, within laboratory, and between laboratory generally3A research report detailing the interlaboratory test is available from ASTMHeadquarters. Request RR:D
49、131104.TABLE 1 Components of Variance as Standard Deviations,Percentage PointsADAP Single-Operator Within-Laboratory Between-LaboratoryMaterial A:420 d. Nylon200 cc. Head466 mm/sAverage ADAP6.15 % 0.00 % 4.13 %Material B:650 d. Polyester200 cc. Head525 mm/sAverage ADAP2.78 % 0.00 % 3.83 %Material C:420 d. Nylon400 cc. Head799 mm/sAverage ADAP3.67 % 0.00 % 0.00 %Material D:630 d. Nylon400 cc. Head1197 mm/sAverage ADAP3.53 % 0.00 % 4.04 %Material E:630 d. Nylon400 cc. Head1187 mm/sAverage ADAP3.58 % 0.00 % 1.30 %Material F:840 d. Nylon800 cc. Head1814 mm/sAverage ADAP2.75 % 0.00 %
