ASTM D6476-12(2021)

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 head 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Jun-2021
• ICS: 43.040.60 - Bodies and body components
• ICS: 59.080.30 - Textile fabrics
• Technical Committee: D13 - Textiles
• Drafting Committee: D13.20 - Inflatable Restraints

Relations

• Refers: ASTM D1776/D1776M-20 - Standard Practice for Conditioning and Testing Textiles
• Effective Date: 01-Feb-2020
• Refers: ASTM D123-17 - Standard Terminology Relating to Textiles
• Effective Date: 01-Mar-2017
• Refers: ASTM D737-04(2016) - Standard Test Method for Air Permeability of Textile Fabrics
• Effective Date: 01-Jul-2016
• Refers: ASTM D1776/D1776M-16 - Standard Practice for Conditioning and Testing Textiles
• Effective Date: 01-Jan-2016
• Refers: ASTM D123-15b - Standard Terminology Relating to Textiles
• Effective Date: 15-Sep-2015
• Refers: ASTM D123-15a - Standard Terminology Relating to Textiles
• Effective Date: 01-Sep-2015
• Refers: ASTM D123-15 - Standard Terminology Relating to Textiles
• Effective Date: 01-Apr-2015
• Refers: ASTM D1776/D1776M-15 - Standard Practice for Conditioning and Testing Textiles
• Effective Date: 01-Feb-2015
• Refers: ASTM D123-13a - Standard Terminology Relating to Textiles
• Effective Date: 15-Jun-2013
• Refers: ASTM D123-13ae1 - Standard Terminology Relating to Textiles
• Effective Date: 15-Jun-2013
• Refers: ASTM D123-13 - Standard Terminology Relating to Textiles
• Effective Date: 15-May-2013
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM D6799-13e1 - Standard Terminology Relating to Inflatable Restraints
• Effective Date: 01-Jan-2013
• Refers: ASTM D6799-13 - Standard Terminology Relating to Inflatable Restraints
• Effective Date: 01-Jan-2013
• Refers: ASTM D737-04(2012) - Standard Test Method for Air Permeability of Textile Fabrics
• Effective Date: 01-Jul-2012

Overview

ASTM D6476-12(2021), published by ASTM International, specifies the standard test method for determining the dynamic air permeability of inflatable restraint fabrics. This method is essential for evaluating high-pressure air permeability under dynamic airflow conditions, particularly for permeable, uncoated fabrics used in airbag modules and other inflatable restraints. The dynamic conditions and higher pressure differentials offered by this method better simulate the actual inflation and deflation cycle experienced during airbag deployment compared to steady-state methods.

The standard supports design validation, lot acceptance, and conformance testing processes, providing a uniform approach for manufacturers, suppliers, and quality assurance teams involved in automotive safety textiles. This method requires equipment specific to the type and range of fabric being tested, and emphasizes the necessity of standardized laboratory conditions and accurate calibration.

Key Topics

• Dynamic Testing Conditions: Simulates real-world airbag deployment by exposing fabric samples to high-pressure air bursts rather than steady airflow.
• Fabric Requirements: Applicable only to permeable, uncoated fabrics; use of coated materials may produce invalid results and damage testing equipment.
• Sampling and Conditioning: Test specimens must be conditioned in a standard atmosphere (21°C and 65% relative humidity) for reliable and consistent results.
• Apparatus and Calibration: Utilizes specialized test heads, pressure transducers, data acquisition systems, and annual equipment calibration to national standards.
• Test Procedure: The process involves mounting the fabric sample, applying dynamic air pressure, and recording data such as pressure-time curves using digital filtering algorithms.
• Data Analysis and Reporting: Results must include average dynamic air permeability (ADAP), time to peak pressure, and detailed reporting of testing conditions and any deviations from the standard.
• Precision and Bias: The standard provides guidance on evaluating within-laboratory and between-laboratory precision, noting particular variance for low permeability fabrics and smaller test heads.
• Conformance and Dispute Resolution: Establishes protocols for lot acceptance, reporting non-conformities, and resolving differences between laboratories.

Applications

The ASTM D6476-12(2021) dynamic air permeability test serves as a critical tool in several contexts:

• Automotive Safety: Supports the selection, development, and quality control of fabrics for airbags and other inflatable safety restraints by replicating real-world deployment stresses.
• Material Development: Aids textile engineers and designers in validating new permeable, uncoated fabrics for suitability in inflatable restraint systems.
• Quality Assurance: Enables manufacturers and suppliers to ensure their products conform to customer specifications and regulatory standards for high-pressure performance.
• Commercial Shipments: Used for lot acceptance testing, providing confidence in the consistency and reliability of delivered fabric batches.
• Broader Textile Testing: May be adapted for other permeable textile products that require assessment of dynamic air permeability, provided necessary equipment modifications are made.

Related Standards

• ASTM D737 - Standard Test Method for Air Permeability of Textile Fabrics (steady-state, low-pressure conditions)
• ASTM D123 - Terminology Relating to Textiles
• ASTM D1776/D1776M - Practice for Conditioning and Testing Textiles
• ASTM D6799 - Terminology Relating to Inflatable Restraints
• ASTM E691 - Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method

Practical Value

Implementing ASTM D6476-12(2021) ensures a consistent, reliable measurement of dynamic air permeability for automotive safety textiles. Its adoption reduces variability between suppliers and laboratories, mitigates potential quality failures, and ensures that inflatable restraint fabrics perform to the stringent demands of real-world airbag deployment. Using this method helps safeguard vehicle occupants and meets rigorous industry and regulatory expectations for safety-critical textile components.

Keywords: dynamic air permeability, inflatable restraint fabrics, ASTM D6476, airbag fabrics, high-pressure permeability testing, textile standards, automotive safety testing.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:D6476 −12 (Reapproved 2021)
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 D2904 Practice for Interlaboratory Testing of a Textile Test
Method that Produces Normally Distributed Data (With-
1.1 This test method covers the procedures used to deter-
drawn 2008)
mine under dynamic airflow conditions the high pressure
D6799 Terminology Relating to Inflatable Restraints
permeability of permeable, uncoated fabrics typically used for
E691 Practice for Conducting an Interlaboratory Study to
inflatable restraints. For the determination of air permeability
Determine the Precision of a Test Method
of inflatable restraint fabrics under low pressure conditions at
steady-state air flow, refer to Test Method D737.
3. Terminology
1.2 Procedures and apparatus other than those stated in this
3.1 For all terminology relating to D13.20, Inflatable
test method may be used by agreement of purchaser and
restraints, refer to Terminology D6799.
supplier with the specific deviations from the standard ac-
3.1.1 The following terms are relevant to this standard:
knowledged in the report.
average dynamic air permeability (ADAP), dynamic air per-
1.3 The values stated in SI units are to be regarded as
meability (DAP), cushion, exponent of dynamic air permeabil-
standard. No other units of measurement are included in this
ity (EXP), inflatable restraint, inflator, module, standard atmo-
standard.
sphere for testing textiles
1.4 This standard does not purport to address all of the
3.2 For all other terms related to textiles, see Terminology
safety concerns, if any, associated with its use. It is the
D123.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
4. Summary of Test Method
mine the applicability of regulatory limitations prior to use.
4.1 A volume of desiccated compressed air at known
1.5 This international standard was developed in accor-
volume and pressure passes through a fabric specimen into the
dance with internationally recognized principles on standard-
standard atmosphere for testing textiles. During the portion of
ization established in the Decision on Principles for the
the test cycle which simulates airbag inflation, the pressure
Development of International Standards, Guides and Recom-
differential pressure across the specimen rises to a value
mendations issued by the World Trade Organization Technical
corresponding to a peak inflation pressure. During the portion
Barriers to Trade (TBT) Committee.
of the test cycle which simulates airbag deflation, the pressure
differential drops to 0 kPa as the air passes through the
2. Referenced Documents
specimen. The time to reach the maximum pressure and the
2.1 ASTM Standards:
subsequent time for the pressure to decrease correspond to
D123 Terminology Relating to Textiles
similar times in an airbag deployment.
D737 Test Method for Air Permeability of Textile Fabrics
4.2 Software algorithms integral to the apparatus smooth
D1776/D1776M Practice for Conditioning and Testing Tex-
out the pressure data and determine the values for ADAP and
tiles
EXP.
5. Significance and Use
This test method is under the jurisdiction ofASTM Committee D13 on Textiles
5.1 For matters relating to lot acceptance of commercial
and is the direct responsibility of Subcommittee D13.20 on Inflatable Restraints.
Current edition approved July 1, 2021. Published July 2021. Originally approved
shipments and conformity to specification or other standard,
ɛ1
in 2000. Last previous edition approved in 2017 as D6476–12 (2017) . DOI:
refer to Section 13 of this test method.
10.1520/D6476-12R21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contactASTM Customer Service at [e-mail]. ForAnnual Book ofASTM
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
theASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6476−12 (2021)
5.2 This test method is useful in the selection and design specimen in a range sufficient to meet the conditions of a
validation of permeable, uncoatable fabrics used in inflatable material specification for dynamic air permeability testing of
restraint cushions.The dynamic conditions and higher pressure inflatable restraint fabrics, with a tolerance of 62 %, mounted
differentials of this test method may better simulate the in a static or low pressure area in the test fixture that does not
inflation and deflation cycle of an airbag module during interfere with airflow.
deployment than do the steady-state conditions of Test Method
6.3 Air Compressor andAir Desiccating Cartridge, capable
D737.
of charging the pressure vessel in the test head to the specified
5.2.1 Only uncoated, permeable fabrics should be used. Use
pressure up to 400 kPa.
of coated fabrics may yield invalid results and potentially
6.4 Mounting Fixture, capable of retaining the fabric speci-
damage the test apparatus.
men over the test orifice without stretching the specimen and
5.3 Within the limits of variance expressed in Section 12,
without air leakage at the periphery of the test area.
this test method is useful for design validation and may be
6.5 ElectricalFiringPulseSource,suitableforactuatingthe
suitable for incorporation in a material specification or for lot
inflation and for communicating with the data acquisition
acceptance testing of commercial shipments. Caution is ad-
system dependent on an electrical signal.
visedonverylowpermeabilityfabricsorwiththe200cm size
test head because between-laboratory precision as presented in 6.6 Data Acquisition System, suitable for recording the
output of the pressure transducers versus elapsed time of
Section 12 may be as high as 21 %.
airflow.
5.4 This test method may be used for materials other than
6.7 Filter Requirements, data sampling rate, transducer
inflatable restraint fabrics which experience dynamic air per-
frequency response, and amplifier frequency response shall be
meability in sudden bursts. In such cases, the physical appa-
such that minimal effect on accuracy of the data occurs. The
ratus or its software algorithms may require modification to
accuracy of the pressure transducers, amplifiers, and timers
provide suitability for use.
within the test apparatus shall be calibrated to within 63%.
5.5 Due to the split-second time interval for testing, the
pressure versus time data is subject to recording anomalies and
7. Sampling
electronic noise. The data should be digitally filtered to obtain
7.1 Dynamic air permeability testing is a destructive test
the underlying smooth pressure curve prior to data analysis.
and therefore necessitates sampling procedures if used in
The software in the apparatus includes a reliable algorithm
conjunction with lot acceptance of commercial shipments.
both to smooth the curve and to determine the exponent of air
7.2 Lot Sample:
permeability.
7.2.1 For acceptance testing, the lot size is the quantity of
5.6 It is inherent in the design and operation of this
fabric finished in one production day or as agreed upon
equipment that major components key to the calibration and
between the purchaser and the supplier.
measurements are specific to the individual test head. The size
7.2.2 Unless otherwise agreed upon between the purchaser
or permeability measuring range of the test head is typically
and the supplier, take as a lot sample all the rolls in a
chosen to correspond to the fabric specimen to be tested. The
commercial shipment. Consider the rolls to be the primary
precision of this test method is highly dependent on the size of
sampling units.
the test head. The precision of the data collected using one test
7.3 Laboratory Sample
head should be used to estimate the precision of data collected
7.3.1 Anentirerolloffabricorafull-widthcutfromtheend
using a different test head, even on the same apparatus.
of a roll within a lot sample constitutes a laboratory sample.
5.7 Itismandatorythatfabricspecimensbeconditionedand
7.4 Test Specimens:
tested in standard atmosphere for testing textiles.
7.4.1 Test specimens are the pieces of fabric that actually
undergo testing. Cut or mark specimens from the end of each
6. Apparatus
roll of fabric in the laboratory sample, as indicated in the
6.1 Removable Test Head, containing a Pressure Vessel of
material specification or equivalent. Cut 165 mm by 330 mm
known volume capable of being charged pneumatically from 0
rectangular specimens from the full-width fabric sample, or
to no less than 400 kPa with a tolerance of 63.0 %, of
mark similarly sized areas across the full-width fabric sample
sufficient volume to challenge adequately the fabric being
without cutting individual specimens.
tested, equipped with a solenoid release valve mechanism, a
7.4.2 If areas of full width fabric are tested without cutting
test chamber, and a circular orifice with an area of 50 cm ; and
individual specimens, position test areas representing a broad
equippedwithameansofmeasuringandadjustingthepressure
distribution across the length and width, preferably along the
range in increments of 1 kPa, a minimum range between
diagonal of the laboratory sample, and no nearer the edge than
pressure set points of 5 kPa and rise and fall ranges in ms
one tenth its width.
(milliseconds) sufficient to meet the conditions of a material
specification for dynamic air permeability testing of inflatable
8. Conditioning
restraint fabrics.
8.1 Precondition test specimens in accordance with Practice
6.2 Pressure Transducers and Rigid Wall Pickup Tubes, D1776/D1776M or as agreed upon between the purchaser and
suitable for measuring the pressure differential of the fabric the supplier.
D6476−12 (2021)
8.2 Prior to testing, bring the test specimens to moisture 11. Report
equilibrium at ambient atmospheric pressure, at 21 °C 6 1 °C,
11.1 State that the tests were conducted in accordance with
and at 65 % 6 2 % relative humidity, unless directed to do
this test method for determining the dynamic air permeability
otherwise by an agreement by the purchaser and supplier.
of inflatable restraints fabrics.
8.3 Equilibrium is considered to have been reached when 11.1.1 If deviation from this test method occurred, any
the increase in mass of the specimen in successive weighings reference to this test method shall state: “Testing was per-
made at intervals of not less than 2 h does not exceed 0.1 % of formed in accordance with ASTM D6476, with the following
the mass of the specimen. changes:”
11.2 The purchaser and supplier shall determine the exact
9. Procedure
form of the test report. Unless otherwise specified, report the
9.1 Select and condition specimens in accordance with 8.1.
following information:
9.2 Mount the fabric specimen on the test fixture, ensuring
11.2.1 Fabric designation,
that the retention mechanism clamps the fabric tightly with
11.2.2 Lot identification,
minimal tension and without damage or wrinkling. 11.2.3 Date of report,
11.2.4 Name of person certifying report,
9.3 Perform all system calibrations.
11.2.5 Relevant specification,
9.4 Enter the specimen number into recording portions of
11.2.6 Number of specimens used in each test,
the data acquisition.
11.2.7 Tests performed, and data obtained,
9.5 Ensurethepressurevesselispressurizedwithdesiccated 11.2.8 Laboratory conditions if other than standard, and
airtoapressuresufficientlyhightotestthespecimenwithinthe
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