ASTM D6476-12(2017)
(Test Method)Standard Test Method for Determining Dynamic Air Permeability of Inflatable Restraint Fabrics
Standard Test Method for Determining Dynamic Air Permeability of Inflatable Restraint Fabrics
SIGNIFICANCE AND USE
5.1 For matters relating to lot acceptance of commercial shipments 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 design validation of permeable, uncoatable fabrics used in inflatable restraint cushions. The dynamic conditions and higher pressure differentials of this test method may better simulate the inflation and deflation cycle of an airbag module during deployment than do the steady-state conditions of Test Method D737.
5.2.1 Only uncoated, permeable fabrics should be used. Use of coated fabrics may yield invalid results and potentially damage the test apparatus.
5.3 Within the limits of variance expressed in Section 12, this test method is useful for design validation and may be suitable for incorporation in a material specification or for lot acceptance testing of commercial shipments. Caution is advised on very low permeability fabrics or with the 200 cm3. size test heat because between-laboratory precision as presented in Section 12 may be as high as 21 %.
5.4 This test method may be used for materials other than inflatable restraint fabrics which experience dynamic air permeability in sudden bursts. In such cases, the physical apparatus or its software algorithms may require modification to provide suitability for use.
5.5 Due to the split-second time interval for testing, the pressure versus time data is subject to recording anomalies and electronic noise. The data should be digitally filtered to obtain the underlying smooth pressure curve prior to data analysis. The software in the apparatus includes a reliable algorithm both to smooth the curve and to determine the exponent of air permeability.
5.6 It is inherent in the design and operation of this equipment that major components key to the calibration and measurements are specific to the individual test head. The size or permeability measuring range of the test head is typically chosen to...
SCOPE
1.1 This test method covers the procedures used to determine under dynamic airflow conditions the high pressure permeability of permeable, uncoated fabrics typically used for inflatable restraints. For the determination of air permeability of inflatable restraint fabrics under low pressure conditions at steady-state air flow, refer to Test Method D737.
1.2 Procedures and apparatus other than those stated in this test method may be used by agreement of purchaser and supplier with the specific deviations from the standard acknowledged in the report.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:D6476 −12 (Reapproved 2017)
Standard Test Method for
Determining Dynamic Air Permeability of Inflatable Restraint
Fabrics
This standard is issued under the fixed designation D6476; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This test method covers the procedures used to deter- 3.1 For all terminology relating to D13.20, Inflatable
mine under dynamic airflow conditions the high pressure restraints, refer to Terminology D6799.
permeability of permeable, uncoated fabrics typically used for 3.1.1 The following terms are relevant to this standard:
inflatable restraints. For the determination of air permeability average dynamic air permeability (ADAP), dynamic air per-
of inflatable restraint fabrics under low pressure conditions at meability (DAP), cushion, exponent of dynamic air permeabil-
steady-state air flow, refer to Test Method D737. ity (EXP, ) inflatable restrain, inflator, module, standard atmo-
sphere for testing textiles
1.2 Procedures and apparatus other than those stated in this
test method may be used by agreement of purchaser and 3.2 For all other terms related to textiles, see Terminology
supplier with the specific deviations from the standard ac- D123.
knowledged in the report.
4. Summary of Test Method
1.3 The values stated in SI units are to be regarded as
4.1 A volume of dessicated compressed air at known vol-
standard. No other units of measurement are included in this
ume and pressure passes through a fabric specimen into the
standard.
standard atmosphere for testing textiles. During the portion of
1.4 This standard does not purport to address all of the
the test cycle which simulates airbag inflation, the pressure
safety concerns, if any, associated with its use. It is the
differential pressure across the specimen rises to a value
responsibility of the user of this standard to establish appro-
corresponding to a peak inflation pressure. During the portion
priate safety and health practices and determine the applica-
of the test cycle which simulates airbag deflation, the pressure
bility of regulatory limitations prior to use.
differential drops to 0 kPa as the air passes through the
specimen. The time to reach the maximum pressure and the
2. Referenced Documents
subsequent time to correspond to similar times in an airbag
2.1 ASTM Standards:
deployment.
D123 Terminology Relating to Textiles
4.2 Software algorithms integral to the apparatus smooth
D737 Test Method for Air Permeability of Textile Fabrics
out the pressure data and determine the values for ADAP and
D1776 Practice for Conditioning and Testing Textiles
EXP.
D2904 Practice for Interlaboratory Testing of a Textile Test
Method that Produces Normally Distributed Data (With-
5. Significance and Use
drawn 2008)
D6799 Terminology Relating to Inflatable Restraints
5.1 For matters relating to lot acceptance of commercial
E691 Practice for Conducting an Interlaboratory Study to
shipments and conformity to specification or other standard,
Determine the Precision of a Test Method
refer to Section 13 of this test method.
5.2 This test method is useful in the selection and design
1 validation of permeable, uncoatable fabrics used in inflatable
This test method is under the jurisdiction ofASTM Committee D13 on Textiles
and is the direct responsibility of Subcommittee D13.20 on Inflatable Restraints.
restraint cushions.The dynamic conditions and higher pressure
Current edition approved Feb. 1, 2017. Published March 2017. Originally
differentials of this test method may better simulate the
approved in 2000. Last previous edition approved in 2012 as D6476–12. DOI:
inflation and deflation cycle of an airbag module during
10.1520/D6476-12R17.
deployment than do the steady-state conditions of Test Method
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contactASTM Customer Service at service@astm.org. ForAnnual Book ofASTM
D737.
Standards volume information, refer to the standard’s Document Summary page on
5.2.1 Only uncoated, permeable fabrics should be used. Use
the ASTM website.
of coated fabrics may yield invalid results and potentially
The last approved version of this historical standard is referenced on
www.astm.org. damage the test apparatus.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6476−12 (2017)
5.3 Within the limits of variance expressed in Section 12, 6.5 ElectricalFiringPulseSource,suitableforactuatingthe
this test method is useful for design validation and may be inflation and for communicating with the data acquisition
suitable for incorporation in a material specification or for lot system dependent on an electrical signal.
acceptance testing of commercial shipments. Caution is ad-
6.6 Data Acquisition System, suitable for recording the
vised on very low permeability fabrics or with the 200 cm .
output of the pressure transducers versus elapsed time of
size test heat because between-laboratory precision as pre-
airflow.
sented in Section 12 may be as high as 21 %.
6.7 Filter Requirements, data sampling rate, transducer
5.4 This test method may be used for materials other than
frequency response, and amplifier frequency response shall be
inflatable restraint fabrics which experience dynamic air per-
such that minimal effect on accuracy of the data occurs. The
meability in sudden bursts. In such cases, the physical appa-
accuracy of the pressure transducers, amplifiers, and timers
ratus or its software algorithms may require modification to
within the test apparatus shall be calibrated to within 63%.
provide suitability for use.
7. Sampling
5.5 Due to the split-second time interval for testing, the
pressure versus time data is subject to recording anomalies and
7.1 Dynamic air permeability testing is a destructive test
electronic noise. The data should be digitally filtered to obtain
and therefore necessitates sampling procedures if used in
the underlying smooth pressure curve prior to data analysis.
conjunction with lot acceptance of commercial shipments.
The software in the apparatus includes a reliable algorithm
7.2 Lot Sample:
both to smooth the curve and to determine the exponent of air
7.2.1 For acceptance testing, the lot size is the quantity of
permeability.
fabric finished in one production day or as agreed upon
5.6 It is inherent in the design and operation of this
between the purchaser and the supplier.
equipment that major components key to the calibration and
7.2.2 Unless otherwise agreed upon between the purchaser
measurements are specific to the individual test head. The size
and the supplier, take as a lot sample all the rolls in a
or permeability measuring range of the test head is typically
commercial shipment. Consider the rolls to be the primary
chosen to correspond to the fabric specimen to be tested. The
sampling units.
precision of this test method is highly dependent on the size of
7.3 Laboratory Sample
the test head. The precision of the data collected using one test
7.3.1 Anentirerolloffabricorafull-widthcutfromtheend
head should be used to estimate the precision of data collected
of a roll within a lot sample constitutes a laboratory sample.
using a different test head, even on the same apparatus.
7.4 Test Specimens:
5.7 Itismandatorythatfabricspecimensbeconditionedand
7.4.1 Test specimens are the pieces of fabric that actually
tested in standard atmosphere for testing textiles.
undergo testing. Cut or mark specimens from the end of each
roll of fabric in the laboratory sample, as indicated in the
6. Apparatus
material specification or equivalent. Cut 165 by 330 mm
6.1 Removable Test Head, containing a Pressure Vessel of
rectangular specimens from the full-width fabric sample, or
known volume capable of being charged pneumatically from 0
mark similarly sized areas across the full-width fabric sample
to no less than 400 kPa with a tolerance of 6 3.0 %, of
without cutting individual specimens.
sufficient volume to challenge adequately the fabric being
7.4.2 If areas of full width fabric are tested without cutting
tested, equipped with a solenoid release valve mechanism, a
individual specimens, position test areas representing a broad
test chamber, and a circular orifice with an area of 50 cm ; and
distribution across the length and width, preferably along the
equippedwithameansofmeasuringandadjustingthepressure
diagonal of the laboratory sample, and no nearer the edge than
range in increments of 1 kPa, a minimum range between
one tenth its width.
pressure set points of 5 kPa and rise and fall ranges in ms
8. Conditioning
sufficient to meet the conditions of a material specification for
dynamic air permeability testing of inflatable restraint fabrics.
8.1 Precondition test specimens in accordance with Practice
D1776 or as agreed upon between the the purchaser and the
6.2 Pressure Transducers and Rigid Wall Pickup Tubes,
supplier.
suitable for measuring the pressure differential of the fabric
specimen in a range sufficient to meet the conditions of a
8.2 Prior to testing, bring the test specimens to moisture
material specification for dynamic air permeability testing of
equilibrium at ambient atmospheric pressure, at 21 6 1°C, and
inflatable restraint fabrics, with a tolerance of 6 2 %, mounted
at 65 6 2 % relative humidity, unless directed to do otherwise
in a static or low pressure area in the test fixture that does not
by an agreement by the purchaser and supplier.
interfere with airflow.
8.3 Equilibrium is considered to have been reached when
6.3 Air Compressor andAir Desiccating Cartridge, capable
the increase in mass of the specimen in successive weighings
of charging the pressure vessel in the test head to the specified
made at intervals of not less than 2 h does not exceed 0.1 % of
pressure up to 400 kPa.
the mass of the specimen.
6.4 Mounting Fixture, capable of retaining the fabric speci-
9. Procedure
men over the test orifice without stretching the specimen and
without air leakage at the periphery of the test area. 9.1 Select and condition specimens in accordance with 8.1.
D6476−12 (2017)
9.2 Mount the fabric specimen on the test fixture, ensuring 11.2 The purchaser and supplier shall determine the exact
that the retention mechanism clamps the fabric tightly with form of the test report. Unless otherwise specified, report the
minimal tension and without damage or wrinkling. following information:
11.2.1 Fabric designation,
9.3 Perform all system calibrations.
11.2.2 Lot identification,
9.4 Enter the specimen number into recording portions of
11.2.3 Date of report,
the data acquisition.
11.2.4 Name of person certifying report,
11.2.5 Relevant specification,
9.5 Ensurethepressurevesselispressurizedwithdesiccated
11.2.6 Number of specimens used in each test,
airtoapressuresufficientlyhightotestthespecimenwithinthe
11.2.7 Tests performed and data obtained,
pressure ranges specified.
11.2.8 Laboratory conditions if other than standard, and
9.6 In accordance with the applicable material specification
11.2.9 Deviations from standard procedures and apparatus.
or laboratory guideline, select and install the appropriate test
head for the fabric type to be measured.
12. Precision and Bias
9.7 Preset the start, upper, and lower pressure limits.
12.1 Bias—For multifilament fabrics such as those used for
9.7.1 Unless otherwise stated in the customer specification,
inflatable restraints, there is no standard reference material
the test head size, and starting pressure should be selected such
availabletoserveasanacceptedstandardvaluefordynamicair
that an average peak pressure of 100 6 10 kPa is reached
permeability testing. In the absence of a known true value, the
during the test. Also unless otherwise stated in the customer
accuracy of this test method cannot be determined.
specification, the Lower Limit should be set to 30 kPa and the
12.2 The analysis of precision of test results using this test
Upper Limit should be set to 70 kPa.
method is meaningful both within-laboratory and between-
9.8 Establish data acquisition system response to pressure laboratory with multiple operators.
inputs. 4
12.3 An Interlaboratory Test was planned and conducted
on uncoated fabrics covering a range of permeabilities typi-
9.9 Initiate the starting sequence and note the response of
cally used in inflatable restraint cushions in accordance with
the data acquisition system to verify successful airflow.
Practice E691 and Practice D2904. For inflatable restraint
9.10 Record maximum differential pressure in kPa, time to
fabrics, the typical range of permeabilities is between zero and
maximum pressure in ms, or whatever data points are required
10 cfm when measured in accordance with Test Method D737.
by the material specification.
Two variables,ADAPand EXPONENTwere studied.Analysis
was done using SAS 6.1, PROC. GLM, and PROC.
9.11 Remove the specimen from the test stand and mark it
as having been tested. VARCOMP. Three components of variance - single-operator,
within-laboratory, and between-laboratory - were statistically
9.12 On the test report, record the data required by the
calculated to determine precision of this test method.
material specification.
12.4 Precision of ADAP—For the components of variance
NOTE 1—The unit of permeability commonly used forADAPmeasure-
listed in Table 1, two averages of observed values should be
ment is mm/s. A velocity of 1 mm/s is the mathematical equivalent of a
considered significantly different at the 95 % probability level
3 2.
permeability of 0.1 cm /(cm s). Permeability and velocity are considered
if the difference equals or exceeds the critical differences listed
interchangeable terms.
in Table 2
12.4.1 Primary source of variance of ADAP is between
10. Equipment Calibration
laboratories.
10.1 For inflatable restraints, all test equipment used in
12.4.2 The critical differences forADAPvalues as a percent
accordance with these test methods shall be certified for
of the ADAP average at the 95 % probability level for single
calibration annually by an independent agency or equipment
operator, within laboratory, and between laboratory generally
manufacturer whose results are traceable to the National
varied inversely with the head size, the air permeability rate,
Institute of Science and Technology (NIST) or other national
and the number of observations.
standards laboratory. The test parameters of the equipment
12.4.3 The critical differences forADAPvalues as a percent
shall be
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D6476 − 12 D6476 − 12 (Reapproved 2017)
Standard Test Method for
Determining Dynamic Air Permeability of Inflatable Restraint
Fabrics
This standard is issued under the fixed designation D6476; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers the procedures used to determine under dynamic airflow conditions the high pressure permeability
of permeable, uncoated fabrics typically used for inflatable restraints. For the determination of air permeability of inflatable
restraint fabrics under low pressure conditions at steady-state air flow, refer to Test Method D737.
1.2 Procedures and apparatus other than those stated in this test method may be used by agreement of purchaser and supplier
with the specific deviations from the standard acknowledged in the report.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D123 Terminology Relating to Textiles
D737 Test Method for Air Permeability of Textile Fabrics
D1776 Practice for Conditioning and Testing Textiles
D2904 Practice for Interlaboratory Testing of a Textile Test Method that Produces Normally Distributed Data (Withdrawn 2008)
D6799 Terminology Relating to Inflatable Restraints
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 For all terminology relating to D13.20, Inflatable restraints, refer to Terminology D6799.
3.1.1 The following terms are relevant to this standard: average dynamic air permeability (ADAP), dynamic air permeability
(DAP), cushion, exponent of dynamic air permeability (EXP, ) inflatable restrain, inflator, module, standard atmosphere for testing
textiles
3.2 For all other terms related to textiles, see Terminology D123.
4. Summary of Test Method
4.1 A volume of dessicated compressed air at known volume and pressure passes through a fabric specimen into the standard
atmosphere for testing textiles. During the portion of the test cycle which simulates airbag inflation, the pressure differential
pressure across the specimen rises to a value corresponding to a peak inflation pressure. During the portion of the test cycle which
simulates airbag deflation, the pressure differential drops to 0 kPa as the air passes through the specimen. The time to reach the
maximum pressure and the subsequent time to correspond to similar times in an airbag deployment.
4.2 Software algorithms integral to the apparatus smooth out the pressure data and determine the values for ADAP and EXP.
This test method is under the jurisdiction of ASTM Committee D13 on Textiles and is the direct responsibility of Subcommittee D13.20 on Inflatable Restraints.
Current edition approved July 1, 2012Feb. 1, 2017. Published August 2012March 2017. Originally approved in 2000. Last previous edition approved in 20082012 as
D6476–08.–12. DOI: 10.1520/D6476-12.10.1520/D6476-12R17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6476 − 12 (2017)
5. Significance and Use
5.1 For matters relating to lot acceptance of commercial shipments 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 design validation of permeable, uncoatable fabrics used in inflatable restraint
cushions. The dynamic conditions and higher pressure differentials of this test method may better simulate the inflation and
deflation cycle of an airbag module during deployment than do the steady-state conditions of Test Method D737.
5.2.1 Only uncoated, permeable fabrics should be used. Use of coated fabrics may yield invalid results and potentially damage
the test apparatus.
5.3 Within the limits of variance expressed in Section 12, this test method is useful for design validation and may be suitable
for incorporation in a material specification or for lot acceptance testing of commercial shipments. Caution is advised on very low
permeability fabrics or with the 200 cm . size test heat because between-laboratory precision as presented in Section 12 may be
as high as 21 %.
5.4 This test method may be used for materials other than inflatable restraint fabrics which experience dynamic air permeability
in sudden bursts. In such cases, the physical apparatus or its software algorithms may require modification to provide suitability
for use.
5.5 Due to the split-second time interval for testing, the pressure versus time data is subject to recording anomalies and
electronic noise. The data should be digitally filtered to obtain the underlying smooth pressure curve prior to data analysis. The
software in the apparatus includes a reliable algorithm both to smooth the curve and to determine the exponent of air permeability.
5.6 It is inherent in the design and operation of this equipment that major components key to the calibration and measurements
are specific to the individual test head. The size or permeability measuring range of the test head is typically chosen to correspond
to the fabric specimen to be tested. The precision of this test method is highly dependent on the size of the test head. The precision
of the data collected using one test head should be used to estimate the precision of data collected using a different test head, even
on the same apparatus.
5.7 It is mandatory that fabric specimens be conditioned and tested in standard atmosphere for testing textiles.
6. Apparatus
6.1 Removable Test Head, containing a Pressure Vessel of known volume capable of being charged pneumatically from 0 to no
less than 400 kPa with a tolerance of 6 3.0 %, of sufficient volume to challenge adequately the fabric being tested, equipped with
a solenoid release valve mechanism, a test chamber, and a circular orifice with an area of 50 cm ; and equipped with a means of
measuring and adjusting the pressure range in increments of 1 kPa, a minimum range between pressure set points of 5 kPa and
rise and fall ranges in ms sufficient to meet the conditions of a material specification for dynamic air permeability testing of
inflatable restraint fabrics.
6.2 Pressure Transducers and Rigid Wall Pickup Tubes, suitable for measuring the pressure differential of the fabric specimen
in a range sufficient to meet the conditions of a material specification for dynamic air permeability testing of inflatable restraint
fabrics, with a tolerance of 6 2 %, mounted in a static or low pressure area in the test fixture that does not interfere with airflow.
6.3 Air Compressor and Air Desiccating Cartridge, capable of charging the pressure vessel in the test head to the specified
pressure up to 400 kPa.
6.4 Mounting Fixture, capable of retaining the fabric specimen over the test orifice without stretching the specimen and without
air leakage at the periphery of the test area.
6.5 Electrical Firing Pulse Source, suitable for actuating the inflation and for communicating with the data acquisition system
dependent on an electrical signal.
6.6 Data Acquisition System, suitable for recording the output of the pressure transducers versus elapsed time of airflow.
6.7 Filter Requirements, data sampling rate, transducer frequency response, and amplifier frequency response shall be such that
minimal effect on accuracy of the data occurs. The accuracy of the pressure transducers, amplifiers, and timers within the test
apparatus shall be calibrated to within 6 3 %.
7. Sampling
7.1 Dynamic air permeability testing is a destructive test and therefore necessitates sampling procedures if used in conjunction
with lot acceptance of commercial shipments.
7.2 Lot Sample:
7.2.1 For acceptance testing, the lot size is the quantity of fabric finished in one production day or as agreed upon between the
purchaser and the supplier.
7.2.2 Unless otherwise agreed upon between the purchaser and the supplier, take as a lot sample all the rolls in a commercial
shipment. Consider the rolls to be the primary sampling units.
D6476 − 12 (2017)
7.3 Laboratory Sample
7.3.1 An entire roll of fabric or a full-width cut from the end of 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 actually undergo testing. Cut or mark specimens from the end of each roll of
fabric in the laboratory sample, as indicated in the material specification or equivalent. Cut 165 by 330 mm rectangular specimens
from the full-width fabric sample, or mark similarly sized areas across the full-width fabric sample without cutting individual
specimens.
7.4.2 If areas of full width fabric are tested without cutting individual specimens, position test areas representing a broad
distribution across the length and width, preferably along the diagonal of the laboratory sample, and no nearer the edge than one
tenth its width.
8. Conditioning
8.1 Precondition test specimens in accordance with Practice D1776 or as agreed upon between the the purchaser and the
supplier.
8.2 Prior to testing, bring the test specimens to moisture equilibrium at ambient atmospheric pressure, at 21 6 1°C, and at 65
6 2 % relative humidity, unless directed to do otherwise by an agreement by the purchaser and supplier.
8.3 Equilibrium is considered to have been reached when the increase in mass of the specimen in successive weighings made
at intervals of not less than 2 h does not exceed 0.1 % of the mass of the specimen.
9. Procedure
9.1 Select and condition specimens in accordance with 8.1.
9.2 Mount the fabric specimen on the test fixture, ensuring that the retention mechanism clamps the fabric tightly with minimal
tension and without damage or wrinkling.
9.3 Perform all system calibrations.
9.4 Enter the specimen number into recording portions of the data acquisition.
9.5 Ensure the pressure vessel is pressurized with desiccated air to a pressure sufficiently high to test the specimen within the
pressure ranges specified.
9.6 In accordance with the applicable material specification or laboratory guideline, select and install the appropriate test head
for the fabric 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 such that
an average peak pressure of 100 6 10 kPa is reached during the test. Also unless otherwise stated in the customer specification,
the Lower Limit should be set to 30 kPa and the Upper Limit should be set to 70 kPa.
9.8 Establish data acquisition system response to pressure inputs.
9.9 Initiate the starting sequence and note the response of the data acquisition system to verify successful airflow.
9.10 Record maximum differential pressure in kPa, time to maximum pressure in ms, or whatever data points are required by
the material specification.
9.11 Remove the specimen from the test stand and mark it as having been tested.
9.12 On the test report, record the data required by the material specification.
NOTE 1—The unit of permeability commonly used for ADAP measurement is mm/s. A velocity of 1 mm/s is the mathematical equivalent of a
3 2.
permeability of 0.1 cm /(cm s). Permeability and velocity are considered interchangeable terms.
10. Equipment Calibration
10.1 For inflatable restraints, all test equipment used in accordance with these test methods shall be certified for calibration
annually by an independent agency or equipment manufacturer whose results are traceable to the National Institute of Science and
Technology (NIST) or other national standards laboratory. The test parameters of the equipment shall be tested within the operating
ranges covered in the material specification or equivalent document.
11. Report
11.1 State that the tests were conducted in accordance with this test method for determining the dynamic air permeability of
inflatable restraints fabrics.
11.1.1 If deviation from this test method occurred, any reference to this test method shall state: “Testing was performed in
accordance with ASTM D6476, with the following changes:”
D6476 − 12 (2017)
11.2 The purchaser and supplier shall determine the exact form of the test report. Unless otherwise specified, report the
following 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 Laboratory conditions if other than standard, and
11.2.9 Deviations from standard procedures and apparatus.
12. Precision and Bias
12.1 Bias—For multifilament fabrics such as those used for inflatable restraints, there is no standard reference material available
to serve as an accepted standard value for dynamic air permeability testing. In the absence of a known true value, the accuracy
of this test method cannot be determined.
12.2 The analysis of precision of test results using this test method is meaningful both within-laboratory and between-laboratory
with multiple operators.
12.3 An Interlaboratory Test was planned and conducted on uncoated fabrics covering a range of permeabilities typically used
in inflatable restraint cushions in accordance with Practice E691 and Practice D2904. For inflatable restraint fabrics, the typical
range of permeabilities is between zero and 10 cfm when measured in accordance with Test Method D737. Two variables, ADAP
and EXPO
...
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