ASTM D7269/D7269M-20

Standard Test Methods for Tensile Testing of Aramid Yarns

SIGNIFICANCE AND USE
5.1 The levels of tensile properties obtained when testing aramid yarns and cords are dependent on the age and history of the specimen and on the specific conditions used during the test. Among these conditions are rate of stretching, type of clamps, gauge length of specimen, temperature and humidity of the atmosphere, rate of airflow across the specimen, and temperature and moisture content of the specimen. Testing conditions accordingly are specified precisely to obtain reproducible test results on a specific sample.  
5.2 Because the force-bearing ability of a reinforced product is related to the strength of the yarn or cord used as a reinforcing material, breaking force is used in engineering calculations when designing various types of textile reinforced products. When needed to compare intrinsic strength characteristics of yarns or cords of different sizes or different types of fiber, breaking tenacity is very useful because, for a given type of fiber, breaking force is approximately proportional to linear density.  
5.3 Elongation of yarn or cord is taken into consideration in the design and engineering of reinforced products because of its effect on uniformity of the finished product and its dimensional stability during service.  
5.4 The FASE is used to monitor changes in characteristics of the textile material during the various stages involved in the processing and incorporation of yarn or cord into a product.  
5.5 Modulus is a measure of the resistance of yarn or cord to extension as a force is applied. It is useful for estimating the response of a textile reinforced structure to the application of varying forces and rates of stretching. Although modulus may be determined at any specified force, initial modulus is the value most commonly used.  
5.6 Work-to-break is dependent on the relationship of force to elongation. It is a measure of the ability of a textile structure to absorb mechanical energy. Breaking toughness is work-to-break per unit mas...
SCOPE
1.1 These test methods cover the tensile testing of aramid yarns, cords twisted from such yarns, and fabrics woven from such cords. The yarn or cord may be wound on cones, tubes, bobbins, spools, or beams; may be woven into fabric; or may be in some other form. The methods include testing procedure only and include no specifications or tolerances.  
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.  
1.3 This standard includes the following test methods:    
Section  
Breaking Force  
11  
Breaking Tenacity  
12  
Breaking Toughness  
17  
Elongation at Break  
13  
Force at Specified Elongation (FASE)  
14  
Linear Density  
10  
Modulus  
15  
Stress at Break  
12  
Work-to-Break  
16  
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: 31-Jan-2020
• ICS: 59.080.20 - Yarns
• Technical Committee: D13 - Textiles
• Drafting Committee: D13.19 - Industrial Fibers and Metallic Reinforcements

Relations

• Replaces: ASTM D7269/D7269M-17 - Standard Test Methods for Tensile Testing of Aramid Yarns
• Effective Date: 01-Feb-2020
• Refers: ASTM E23-24 - Standard Test Methods for Notched Bar Impact Testing of Metallic Materials
• Effective Date: 01-Apr-2024
• Refers: ASTM D4848-98(2018) - Standard Terminology Related to Force, Deformation and Related Properties of Textiles
• Effective Date: 01-Sep-2018
• Refers: ASTM D6587-12(2018) - Standard Test Method for Yarn Number Using Automatic Tester
• Effective Date: 01-Jul-2018
• Refers: ASTM D123-17 - Standard Terminology Relating to Textiles
• Effective Date: 01-Mar-2017
• Refers: ASTM E23-16a - Standard Test Methods for Notched Bar Impact Testing of Metallic Materials
• Effective Date: 01-Apr-2016
• Refers: ASTM E23-16 - Standard Test Methods for Notched Bar Impact Testing of Metallic Materials
• 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 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 E23-12c - Standard Test Methods for Notched Bar Impact Testing of Metallic Materials
• Effective Date: 15-Nov-2012
• Refers: ASTM E23-12b - Standard Test Methods for Notched Bar Impact Testing of Metallic Materials
• Effective Date: 01-Jul-2012

Overview

ASTM D7269/D7269M-20: Standard Test Methods for Tensile Testing of Aramid Yarns describes procedures for evaluating the tensile properties of aramid yarns, cords twisted from aramid yarns, and fabrics woven from such cords. The standard outlines reliable test methods to measure critical mechanical properties, such as breaking force, tenacity, modulus, elongation, and more. By specifying these methods, the standard ensures consistent, reproducible results for manufacturers, engineers, and testing laboratories involved in textile reinforcement, industrial textiles, and high-performance applications.

These test methods apply to aramid materials in various forms, including yarns on cones, tubes, bobbins, spools, beams, as well as woven fabrics and other configurations. The document is designed for international use and complies with the principles established by the World Trade Organization's Technical Barriers to Trade (TBT) Committee.

Key Topics

• Tensile Properties Evaluation: The standard defines the testing procedures for measuring breaking force, breaking tenacity, and breaking toughness of aramid yarns and cords.
• Elongation at Break: Guidance is provided for determining elongation at break, a crucial parameter for uniformity and stability of textile-reinforced products.
• Force at Specified Elongation (FASE): FASE testing tracks changes in material characteristics during processing and incorporation into finished products.
• Modulus Measurement: The resistance of aramid yarns and cords to extension under applied force is tested, providing valuable input for reinforcement design.
• Work-to-Break: Procedures to quantify the energy absorption capability of yarn structures, indicating mechanical toughness.
• Sample Preparation and Conditioning: Instructions for moisture equilibration, mechanical twisting, and specimen handling help minimize testing variability.
• Precision and Bias: The standard discusses repeatability, reproducibility, and interlaboratory testing, helping resolve discrepancies between test results from different labs.
• Safety Considerations: Users must establish their own safety protocols and ensure compliance with health and environmental regulations.

Applications

The ASTM D7269/D7269M-20 standard is widely applicable in industries where aramid yarn performance is critical:

• Textile Reinforced Composites: Used in the design and quality assurance of products such as tires, hoses, conveyer belts, and high-strength fabrics.
• Industrial Textiles: Provides data necessary for engineering calculations and product development for fire-resistant, ballistic, or cut-resistant materials.
• Quality Control and R&D: Enables manufacturers and research institutions to benchmark materials, compare different aramid types, or optimize textile processing parameters.
• Material Certification: Supports procurement specifications by ensuring that aramid products meet consistent tensile properties.
• Product Development: Facilitates selection and optimization of yarns and cords based on tensile strength, elongation, and toughness characteristics.

By following this standard, organizations can achieve reliable, comparable test results essential for engineering safe, high-performance textile-reinforced products.

Related Standards

Several ASTM standards are referenced within ASTM D7269/D7269M-20 and are integral to ensuring comprehensive testing and reporting in textile applications:

• ASTM D76: Specification for Tensile Testing Machines for Textiles
• ASTM D123: Terminology Relating to Textiles
• ASTM D1776: Practice for Conditioning and Testing Textiles
• ASTM D1907: Test Method for Linear Density of Yarn (Skein Method)
• ASTM D2258: Practice for Sampling Yarn for Testing
• ASTM D3800: Test Method for Density of High-Modulus Fibers
• ASTM D4848: Terminology Related to Force, Deformation, and Related Properties of Textiles
• ASTM D6587: Test Method for Yarn Number Using Automatic Tester

These related standards ensure compatibility, proper terminology, and accurate reporting across textile testing protocols.

Keywords: ASTM D7269, aramid yarn, tensile testing, breaking force, modulus, elongation, industrial textiles, textile reinforcement, quality control, test methods, FASE, linear density, ASTM textile standards.

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: D7269/D7269M − 20
Standard Test Methods for
Tensile Testing of Aramid Yarns
This standard is issued under the fixed designation D7269/D7269M; 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 2. Referenced Documents
2.1 ASTM Standards:
1.1 These test methods cover the tensile testing of aramid
D76 Specification for Tensile Testing Machines for Textiles
yarns, cords twisted from such yarns, and fabrics woven from
D123 Terminology Relating to Textiles
such cords. The yarn or cord may be wound on cones, tubes,
D1776 Practice for Conditioning and Testing Textiles
bobbins, spools, or beams; may be woven into fabric; or may
D1907 Test Method for Linear Density of Yarn (Yarn Num-
be in some other form. The methods include testing procedure
ber) by the Skein Method
only and include no specifications or tolerances.
D2258 Practice for Sampling Yarn for Testing
1.2 The values stated in either SI units or inch-pound units
D3800 Test Method for Density of High-Modulus Fibers
are to be regarded separately as standard. The values stated in
D4848 Terminology Related to Force, Deformation and
each system may not be exact equivalents; therefore, each
Related Properties of Textiles
system shall be used independently of the other. Combining
D6587 Test Method for Yarn Number Using Automatic
values from the two systems may result in non-conformance
Tester
with the standard.
E23 Test Methods for Notched Bar Impact Testing of Me-
tallic Materials
1.3 This standard includes the following test methods:
Section
Breaking Force 11
3. Terminology
Breaking Tenacity 12
3.1 Definitions:
Breaking Toughness 17
Elongation at Break 13
3.1.1 slippage, n—with tensile testing, insufficient quality of
Force at Specified Elongation (FASE) 14
clamping, resulting in movement of the test material through
Linear Density 10
Modulus 15
the total clamping surface. This can be visualized by the
Stress at Break 12
movement of markers at the clamp exit, or by sudden changes
Work-to-Break 16
in the strain-modulus curves (1st derivative of the strain-stress
1.4 This standard does not purport to address all of the
curve).
safety concerns, if any, associated with its use. It is the
3.2 The following terms are relevant to this standard:
responsibility of the user of this standard to establish appro-
aramid, breaking force, breaking tenacity, breaking toughness,
priate safety, health, and environmental practices and deter-
chord modulus, elongation, force at specified elongation
mine the applicability of regulatory limitations prior to use.
(FASE), industrial yarn, initial modulus, moisture equilibrium
1.5 This international standard was developed in accor-
for testing, standard atmosphere for testing textiles, work-to-
dance with internationally recognized principles on standard-
break.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
3.3 For definitions of terms related to force and deformation
mendations issued by the World Trade Organization Technical
in textiles, refer to Terminology D4848.
Barriers to Trade (TBT) Committee.
3.4 For definitions of other terms related to textiles, refer to
Terminology D123.
These test methods are under the jurisdiction of ASTM Committee D13 on
Textiles and are the direct responsibility of Subcommittee D13.19 on Industrial
Fibers and Metallic Reinforcements. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Feb. 1, 2020. Published February 2020. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2006. Last previous edition approved in 2017 as D7269/D7269M–17. Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D7269_D7269M-20. the ASTM website.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959. United States
D7269/D7269M − 20
4. Summary of Test Method 5.8 If there are differences of practical significance between
reported test results for two laboratories (or more), compara-
4.1 These test methods are used to determine the tensile
tive tests should be performed to determine if there is a
properties of aramid yarns or cords.
statistical bias between them, using competent statistical assis-
4.2 Aconditioned or oven-dried specimen of aramid yarn or
tance. As a minimum, test samples should be used that are as
cord is clamped in a tensile testing machine and then stretched
homogeneous as possible, that are drawn from the material
or loaded until broken. Breaking force, elongation, and force at
from which the disparate test results were obtained, and that
specified elongation (FASE) are determined directly. Modulus
are randomly assigned in equal numbers to each laboratory for
and work-to-break are calculated from the force-elongation
testing. Other materials with established test values may be
curve.Theoutputofaconstant-rate-of-extension(CRE)tensile
used for this purpose.The test results from the two laboratories
testingmachinecanbeconnectedwithelectronicrecordingand
should be compared using a statistical test for unpaired data, at
computing equipment, which may be programmed to calculate
a probability level chosen prior to the testing series. If a bias is
and print the test results of tensile properties of interest.
found, either its cause must be found and corrected, or future
test results must be adjusted in consideration of the known
5. Significance and Use
bias.
5.1 The levels of tensile properties obtained when testing
aramid yarns and cords are dependent on the age and history of
6. Apparatus
the specimen and on the specific conditions used during the
6.1 Tensile Testing Machine—Asingle-strand tensile testing
test. Among these conditions are rate of stretching, type of
machine of the constant rate of extension (CRE) type. The
clamps, gauge length of specimen, temperature and humidity
tensile testing equipment can be either manually operated or
of the atmosphere, rate of airflow across the specimen, and
can be an automated device.The specifications and methods of
temperature and moisture content of the specimen. Testing
calibration and verification of these machines shall conform to
conditions accordingly are specified precisely to obtain repro-
Specification D76. The tester shall be equipped with an
ducible test results on a specific sample.
electronic data acquisition and data evaluation system.
5.2 Becausetheforce-bearingabilityofareinforcedproduct
6.1.1 Clamps:
is related to the strength of the yarn or cord used as a
6.1.1.1 Manually Operated System—Bollardtypeclamps,in
reinforcing material, breaking force is used in engineering
which the specimen is gripped between plane-faced jaws and
calculations when designing various types of textile reinforced
then makes a partial turn (wrap angle) around a curved
products. When needed to compare intrinsic strength charac-
extension (or other type of snubbing device) of one jaw before
teristics of yarns or cords of different sizes or different types of
passing to the other similar clamp (see Fig. 1 and Fig. 2).
fiber, breaking tenacity is very useful because, for a given type
Clamps with a wrap angle of 180° are required for yarns with
of fiber, breaking force is approximately proportional to linear
a linear density up to 3500 decitex [3000 denier]. For linear
density.
densities above 3500 decitex [3000 denier], clamps with a
wrap angle of 270° are recommended to prevent slippage. See
5.3 Elongation of yarn or cord is taken into consideration in
Note 1.
the design and engineering of reinforced products because of
6.1.1.2 Automated Device—Use the clamping system sup-
its effect on uniformity of the finished product and its dimen-
plied. See Note 1.
sional stability during service.
6.1.1.3 Clampsshallgripthetestspecimenwithoutspurious
5.4 The FASE is used to monitor changes in characteristics
slippageordamagetothetestspecimenwhichcanresultinjaw
of the textile material during the various stages involved in the
breaks.The clamps shall maintain constant gripping conditions
processing and incorporation of yarn or cord into a product.
duringthetestbymeansofpneumaticorhydraulicclamps.The
5.5 Modulusisameasureoftheresistanceofyarnorcordto
surface of the jaws in contact with the specimen shall be of a
extension as a force is applied. It is useful for estimating the
material and configuration that minimizes slippage and/or
response of a textile reinforced structure to the application of
specimen failure in the clamping zone.
varying forces and rates of stretching. Although modulus may
be determined at any specified force, initial modulus is the
value most commonly used.
5.6 Work-to-break is dependent on the relationship of force
to elongation. It is a measure of the ability of a textile structure
to absorb mechanical energy. Breaking toughness is work-to-
break per unit mass.
5.7 It should be emphasized that, although the preceding
parameters are related to the performance of a textile-
reinforced product, the actual configuration of the product is
significant. Shape, size, and internal construction also can have
appreciable effect on product performance. It is not possible,
therefore, to evaluate the performance of a textile reinforced
product in terms of the reinforcing material alone. FIG. 1 Example Bollard Type Clamps
D7269/D7269M − 20
Place each laboratory sampling unit in a moisture-proof
polyethylene bag or other moisture-proof container to protect
the samples from atmospheric changes until ready to condition
the samples in the atmosphere for testing aramids. Take the
number of specimens for testing specified for the specific
property measurement to be made.
7.3 Cord:
7.3.1 Number of Samples and Specimens—The size of an
acceptance sampling lot of tire cord shall be not more than one
truck or rail car load or as determined by agreement between
the purchaser and the supplier. Take samples at random from
each of a number of cones, tubes, bobbins, or spools within a
lot to be as representative as possible within practical limita-
tions. Make only one observation on an individual package for
each physical property determination. Take the number of
samples, therefore, that will be sufficient to cover the total
number of specimens required for the determination of all
physical properties of the tire cord. The recommended number
of specimens is included in the appropriate sections of specific
test methods covered in this standard. Where such is not
specified, the number of specimens is as agreed upon between
buyer and supplier.
7.3.2 Preparation of Samples—If specimens are not taken
FIG. 2 Gauge Length in Bollard Type Jaws
directly from the original package, preferably wind the sample
on a tube or spool by means of a winder using a tension of 5
6.1.2 Gauge Length—The gauge length shall be the total
6 1 mN/tex [0.05 6 0.01 gf/den]. If the sample is collected as
length of yarn measured between the clamping point A of the
a loosely wound package, or in the form of a skein, some
first clamp and the point B of the second clamp in the starting
shrinkage invariably will occur, in which case, report that the
position (see Fig. 2).
observed results were determined on a relaxed sample. Use
care in handling the sample. Discard any sample subjected to
NOTE1—Theselectedtestingequipment(tester,clamp,gaugelength)is
any change of twist, kinking, or making any bend with a
known to have an influence on the properties measured (see Section 19,
Table 8). A method for eliminating the influences introduced by the
diameter less than 10 times the yarn/cord thickness (or diam-
selected testing equipment is given in Appendix X1.
eter). Place the sample in a moisture-proof polyethylene bag or
6.1.3 Use a crosshead travel rate in mm/min [in./min] of other moisture-proof container to protect it from atmospheric
changes until ready to condition the sample in the test
50 %ofthenominalgaugelengthinmillimeters[inches]ofthe
specimen for para-aramids; 120 % of the nominal gauge length atmosphere for aramids.
in millimeters [inches] of the specimen for meta-aramids.
8. Conditioning
7. Sampling
8.1 Bring all specimens of yarn and cord to moisture
7.1 Remove and discard a minimum of 25 m [27 yd] from
equilibrium for testing in the atmosphere for testing aramids as
the outside of the package before taking the sample or any
directed in Practice D1776. Report the option used.
specimens.
8.1.1 The moisture equilibrium of conditioned aramids can
be affected by heat and humidity conditions to which the
7.2 Yarn:
samples have been previously exposed.
7.2.1 Packages—For acceptance testing, sample each lot as
directed in Practice D2258. Place each laboratory sampling
9. Sample Preparation
unit in a moisture-proof polyethylene bag or other moisture-
proof container to protect the samples from atmospheric 9.1 Because of the difficulty of securing the same tension in
changes until ready to condition the samples in the atmosphere allthefilamentsandbecauseofslippageintheclamps,variable
for testing aramids. Take the number of specimens for testing results may be obtained when testing flat multifilament yarns.
specified for the specific property measurement to be made. Therefore, a defined amount of twist must be inserted prior to
7.2.2 Beams—For acceptance testing, sample by winding testing. Machine twisting by means of a ring twister is
yarns on a tube or spool by means of a winder using a tension recommended. The ring twisters can be equipped with a
of 5 6 1 mN/tex [0.05 6 0.01 gf/den]. Take the yarn from the guiding eyelet with either a variable or a fixed distance to the
outside beam layers unless there is a question or disagreement traveller (the latter resulting in a more uniform twist tension).
regarding the shipment; in this case, take the sample only after The twist tension should be approximately 10 mN/tex [0.10
removingyarnfromthe beam to a radial depth of 6 mm[ ⁄4 in.] gf/den]. If used, anti-balloon rings must be of a material that
or more to minimize the effects of handling and atmospheric will not damage the yarn. A manual or mechanical twister can
changes that may have occurred during shipment or storage. also be used in the absence of a ring twister, provided the RPM
D7269/D7269M − 20
is calibrated and verified with a tolerance of 20 6 0.1 machine. For meta-aramids, use 250 6 1 mm [10.00 6 0.05
revolutions at a frequency based on use. For meta-aramid, the in.]. For para-aramids, the gauge length is 500 6 2 mm [20.0
inserted twist is 120 tpm [3.0 tpi]. For para-aramid yarns the 6 0.1 in.]. For bollard type clamps with a wrap angle of 270°
amount of twist to be inserted depends upon the linear density agaugelengthof635 62mm[0.0 60.1in.]isrecommended.
and is approximately: Remove the test material from the specimen or sample and
handle it to prevent any change in twist prior to closing the
Linear density Twist
dtex tpm
jaws of the clamps. Do not touch that portion of the material
180 < LD < 240 230
thatwillbebetweentheclampswithbarehands.Dependingon
240 < LD < 380 190
the equipment being used and the availability of on-line
380 < LD < 500 160
500 < LD < 650 140
computer control and data processing, either can be used:
650 < LD < 775 125
Slack Start procedure (preferred procedure, see 11.3.1)or
775 < LD < 1050 110
Pretension–start procedure (see 11.3.2)
1050 < LD < 1400 95
1400 < LD < 2100 80
11.3.1 Slack Start Procedure—Thread one end of the speci-
2100 < LD < 4500 60
men between the jaws of one of the clamps and close it. Place
4500 < LD < 7000 45
7000 < LD < 9500 35
the other end of the specimen through the jaws of the second
9500 > LD 30
clamp and keep the specimen just slack (zero tension) and
NOTE 2—The twist level per range is based on the equation
close the clamp, taking care that the thread is positioned in the
twist@Tpm#5 .
centerline of the jaws of the clamp. Operate the testing
=LD@tex#
machine at the rate as specified in 6.1.3 and stretch the
9.2 Inserting twist for tensile testing has the following
specimen until it ruptures. When the specimen breaks, read the
effects on the test results:
breaking force (BF) (maximum force) in Newton [pounds-
9.2.1 Modestly increases breaking force; too much or too
force]. Discard tests that do not break within the free length
low twist reduces breaking force,
between the clamps. If the clamps are of the air-actuated type,
9.2.2 Increases elongation at break, and
adjust the air pressure to prevent specimens slipping in the
9.2.3 Reduces modulus.
jaws, but keep the air pressure below the level that will cause
specimens to break at the edge of the jaws. This slack start
10. Linear Density
procedure has the effect that the nominal gauge length of the
10.1 Scope—Thistestmethodisusedtodeterminethelinear
specimen will be slightly greater as specified in 11.3.
density of yarn or cord for use in the calculation of tensile
11.3.2 Pretension-Start Procedure—Useatensioningdevice
properties such as modulus and tenacity at break.
thatappliesapretensioncorrespondingto20 61mN/tex[0.20
6 0.01 gf/den] for aramid fibers. This device may be a weight,
10.2 Procedure:
a spring, or an air-actuated mechanism. Thread one end of the
10.2.1 Determine linear density as directed in Option 1 of
specimen between the jaws of the clamp connected to the
Test Method D1907 or use an Automated Tester as directed in
loading cell and close it. Place the other end through the jaw of
Test Method D6587. For both test methods, condition the yarn
the second clamp and fix a pretension weight to the unclamped
as specified in Section 8.
end or pull the end of the specimen until the specified
10.2.2 If scoured oven-dried linear density is needed, use
pretension is applied. Close the second clamp and operate the
Test Method D1907, Option 5.
testing machine at the rate specified in 6.1.3. When the
10.3 Report the method used and the average linear density
specimen breaks (ruptures), read the breaking force BF (maxi-
of the sample.
mum force), in Newton [pounds-force]. Discard tests that do
not break within the free length between the clamps. If the
11. Breaking Force of Conditioned Yarns and Cords
clamps are of the air-actuated type, adjust the air pressure so
11.1 Scope—This test method is used to determine the
that specimens will not slip in the jaws, but keep air pressure
breaking force of yarns and cords after conditioning in the
below the level that will cause specimens to break at the edge
atmosphere for testing aramids as defined in Practice D1776.
of the jaws. The following notes provide useful information in
Make all tests on the conditioned yarns and cords in the
obtaining more consistent results in tensile testing:
atmosphere for testing aramids as directed in Practice D1776.
NOTE 3—When arbitration of test data is involved, use care in the
11.2 Number of Specimens—Perform five tests per speci-
applicationofthepretensionforcethatmaybespecifiedbecausetheactual
men.
pretensioninthespecimencommonlyisdifferentfromtheamountapplied
externally because of losses due to friction in the clamp. Check the
11.3 Procedure—Selectaloadingcellandthesettingsofthe
pretension before starting the testing machine. The actual pretension can
tensile tester such that the estimated breaking force of the
be measured by strain gauges. Other tension-measuring instruments with
specimenwillfallintherangefrom10to90 %ofthefull-scale
sufficient accuracy may be used, provided that the specimen is threaded
through the instrument prior to being placed in the second clamp. This
force of the load cell used.This selection of the full scale force
procedure is necessary because many instruments require appreciable
may be done manually by the operator before the start of the
displacement of the specimen.
test or by electronic means or computer control during the test
NOTE 4—When arbitration is not involved, one of the following
by automatically adjusting the amplification of the load cell
approximations of the specified pretension may be used. Either exert a
amplifier. Adjust the distance between the clamps measured
force of 120 % of the nominal pretension to the unclamped end of the
from nip to nip of the jaws of the clamps (Fig. 2) on the testing specimen prior to closing the second grip, or apply one of the forces listed
D7269/D7269M − 20
as follows for the specified groups of yarn and cord sizes to secure the
12.4 Precision and Bias:
necessary pretension.
12.4.1 Precision—See Section 19.
Linear Density of Specimen Amount of Force
12.4.2 Bias—See Section 19.3.
N[gf]
Below 400 tex [3600 denier] 1 [100]
12.5 Stress or Break:
400 to 600 tex [3600 to 5400 denier] 2 [200]
12.5.1 Scope—This test method is used to determine the
600 to 800 tex [5400 to 7200 denier] 3 [300]
breaking force per cross-section area of yarns and cords after
Above 800 tex [7200 denier] 4 [400]
conditioning in the atmosphere for testing aramids.
NOTE 5—When using a CRE-type tensile machine, a third technique is
12.5.2 Calculate the specific stress at break using Eq 3:
toclosetheupperclamp,thenapplypretensionbypullingonthespecimen
until the recorder pen moves approximately ⁄2-chart division from the
Rho
SB 5 BT · (3)
zerolineonthechartwhenusingaforcescalethatisthesameasthatused n
for determining the breaking force.
where additonally:
11.3.3 The velocity of conditioned air flowing across a
SB = stress at break in MPa, and
specimen while determining tensile properties can have a
Rho = density in kg/m .
measurableeffectonthebreakingforceandelongationatbreak
because of the Gough-Joule effect. The magnitude ofthis effect
12.5.2.1 The density is either:
depends on the type of fiber, air velocity, and sample history.
(1) determined according to Test Method D3800, Proce-
Interlaboratory testing of nylon, polyester, and rayon cords
dure A—Buoyancy (Archimedes) Method; test temperature as
indicates that air velocities of less than 250 mm/s [50 ft/min]
in Section 8.
across the specimen will not significantly bias the comparison
(2) the value determined by the supplier (Test Method
of cord properties between laboratories.
D3800, see (1)).
(3) the nominal value for para-aramids fo 1440 kg/m .
11.4 Calculate the average and standard deviation of break-
12.5.3 Calculate the average and standard deviation of the
ing force from the individual breaking forces.
stress at break of the sample.
NOTE6—ThepreferredtermtouseisBF(BreakingForce),howeverthe
use of BS (Breaking Strength) for the average value is permitted.
12.5.4 Report results as stated in Section 18.
12.5.5 Precision and Bias:
11.5 Report results as stated in Section 18.
12.5.5.1 Precision—See Section 19.
11.6 Precision and Bias:
12.5.5.2 Bias—See 19.3.
11.6.1 Precision—See Section 19.
11.6.2 Bias—See 19.3.
13. Elongation at Break of Conditioned Yarns and Cords
12. Breaking Tenacity and Stress at Break of
13.1 Scope—This test method is used to determine the
Conditioned Yarns and Cords
elongation at break of yarns and cords after conditioning in the
12.1 Scope—This test method is used to determine the
atmosphere for testing aramids.
breaking tenacity of yarns and cords after conditioning in the
13.2 Procedure—Determine the elongation at break of each
atmosphere for testing aramids.
conditionedspecimenwhendeterminingitsbreakingforce(see
12.2 Calculation—Calculate the breaking tenacity of the
Section 11). Read the extension at the breaking force by
sampleintermsofmilli-Newtonpertex(mN/tex)[grams-force
electronic means. The general equation for elongation at break
per denier (gf/den)] from the breaking force and the linear
is given in Eq 4:
density using Eq 1 and 2:
E
bf
EB 5 ·100% (4)
S D
BF ·1000
n L
o
BT 5 (1)
n
LD
t
where:
BF·454
l
EB = elongation at break, %,
BT 5 (2)
g
LD
d
E = extension of specimen at the breaking force, mm [in.],
bf
where: and
L = length of the specimen, under specified pretension
o
BT = breaking tenacity, mN/tex,
n
measured from nip-to-nip of the holding clamps, mm
BT = breaking tenacity, gf/den,
g
[in.].
BF = breaking force, N,
n
BF = breaking force, lbf,
l
13.2.1 Pretension Start—Use Eq 4.
LD = average linear density of sample, tex, and
t
13.2.2 Slack Start—Calculate the gauge length (L)to
o
LD = average linear density of sample, denier.
d
include the slack using Eq 5:
12.2.1 Calculate the average and standard deviation of the
L 5 L 1DP (5)
o s
breaking tenacity of the sample.
where:
12.3 Report results as stated in Section 18.
L = length of the specimen, under specified pretension,
o
measured from nip-to-nip of the holding clamps, mm
Jones, R. E. and Desson, M. J., “Adiabatic Effects on Tensile Testing,” Journal
[in.],
of the I.R.I, June 1967.
D7269/D7269M − 20
13.4.1 Precision—See Section 19.
L = gauge length after clamping specimen (absolute dis-
s
13.4.2 Bias—See 19.3.
tance nip-to-nip before movement of crosshead), mm
[in.], and
14. Force at Specified Elongation (FASE) of Conditioned
DP = displacement of crosshead to reach the specified pre-
Yarns and Cords
tension of the specimen (see Fig. 3), mm [in.].
14.1 Scope—This test method is used to determine the force
13.2.2.1 Thepretensionforaramidcorrespondswith20 61
at specified elongation (FASE) of yarns and cords after
mN/tex [0.20 6 0.01 gf/den].
conditioning in the atmosphere for testing aramids.
13.2.2.2 Thegeneralequationforelongationatbreakforthe
slack start procedure is given in Eq 6: 14.2 Procedure—Determine the force at specified elonga-
tion (FASE) of each conditioned specimen when determining
E
bf
EB 5 ·100% (6)
itsbreakingforce(seeSection 11andFig.3).Readtheforceby
L 1DP
s
electronic means with an on-line computer at the specified
where:
value of elongation listed in Table 1.
EB = elongation at break, %,
NOTE 7—The preferred term to use is FASE (Force at Specified
E = extension of specimen at the breaking force, mm [in.],
bf
Elongation), however the use of LASE (Load at Specified Elongation) is
permitted.
L = gauge length after clamping specimen (absolute dis-
s
14.2.1 Ensurethatthedisplacement(DP)ofthecrossheadto
tance nip-to-nip before movement of crosshead), mm
remove slack is taken into account when using slack start
[in.], and
procedure. Follow same general procedure as for elongation at
DP = displacement of crosshead
...

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: D7269/D7269M − 17 D7269/D7269M − 20
Standard Test Methods for
Tensile Testing of Aramid Yarns
This standard is issued under the fixed designation D7269/D7269M; 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 These test methods cover the tensile testing of aramid yarns, cords twisted from such yarns, and fabrics woven from such
cords. The yarn or cord may be wound on cones, tubes, bobbins, spools, or beams; may be woven into fabric; or may be in some
other form. The methods include testing procedure only and include no specifications or tolerances.
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.
1.3 This standard includes the following test methods:
Section
Breaking Force 11
Breaking Tenacity 12
Breaking Toughness 17
Elongation at Break 13
Force at Specified Elongation (FASE) 14
Linear Density 10
Modulus 15
Stress at Break 12
Work-to-Break 16
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.
2. Referenced Documents
2.1 ASTM Standards:
D76 Specification for Tensile Testing Machines for Textiles
D123 Terminology Relating to Textiles
D1776 Practice for Conditioning and Testing Textiles
D1907 Test Method for Linear Density of Yarn (Yarn Number) by the Skein Method
D2258 Practice for Sampling Yarn for Testing
D3800 Test Method for Density of High-Modulus Fibers
D4848 Terminology Related to Force, Deformation and Related Properties of Textiles
D6587 Test Method for Yarn Number Using Automatic Tester
E23 Test Methods for Notched Bar Impact Testing of Metallic Materials
3. Terminology
3.1 Definitions:
These test methods are under the jurisdiction of ASTM Committee D13 on Textiles and are the direct responsibility of Subcommittee D13.19 on Industrial Fibers and
Metallic Reinforcements.
Current edition approved July 15, 2017Feb. 1, 2020. Published October 2017February 2020. Originally approved in 2006. Last previous edition approved in 20112017
as D7269/D7269M–11.–17. DOI: 10.1520/D7269_D7269M-17.10.1520/D7269_D7269M-20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7269/D7269M − 20
3.1.1 slippage, n—with tensile testing, insufficient quality of clamping, resulting in movement of the test material through the
total clamping surface. This can be visualized by the movement of markers at the clamp exit, or by sudden changes in the
strain-modulus curves (1st derivative of the strain-stress curve).
3.2 The following terms are relevant to this standard: aramid, breaking force, breaking tenacity, breaking toughness, chord
modulus, elongation, force at specified elongation (FASE), industrial yarn, initial modulus, moisture equilibrium for testing,
standard atmosphere for testing textiles, work-to-break.
3.3 For definitions of terms related to force and deformation in textiles, refer to Terminology D4848.
3.4 For definitions of other terms related to textiles, refer to Terminology D123.
4. Summary of Test Method
4.1 These test methods are used to determine the tensile properties of aramid yarns or cords.
4.2 A conditioned or oven-dried specimen of aramid yarn or cord is clamped in a tensile testing machine and then stretched or
loaded until broken. Breaking force, elongation, and force at specified elongation (FASE) are determined directly. Modulus and
work-to-break are calculated from the force-elongation curve. The output of a constant-rate-of-extension (CRE) tensile testing
machine can be connected with electronic recording and computing equipment, which may be programmed to calculate and print
the test results of tensile properties of interest.
5. Significance and Use
5.1 The levels of tensile properties obtained when testing aramid yarns and cords are dependent on the age and history of the
specimen and on the specific conditions used during the test. Among these conditions are rate of stretching, type of clamps, gauge
length of specimen, temperature and humidity of the atmosphere, rate of airflow across the specimen, and temperature and moisture
content of the specimen. Testing conditions accordingly are specified precisely to obtain reproducible test results on a specific
sample.
5.2 Because the force-bearing ability of a reinforced product is related to the strength of the yarn or cord used as a reinforcing
material, breaking force is used in engineering calculations when designing various types of textile reinforced products. When
needed to compare intrinsic strength characteristics of yarns or cords of different sizes or different types of fiber, breaking tenacity
is very useful because, for a given type of fiber, breaking force is approximately proportional to linear density.
5.3 Elongation of yarn or cord is taken into consideration in the design and engineering of reinforced products because of its
effect on uniformity of the finished product and its dimensional stability during service.
5.4 The FASE is used to monitor changes in characteristics of the textile material during the various stages involved in the
processing and incorporation of yarn or cord into a product.
5.5 Modulus is a measure of the resistance of yarn or cord to extension as a force is applied. It is useful for estimating the
response of a textile reinforced structure to the application of varying forces and rates of stretching. Although modulus may be
determined at any specified force, initial modulus is the value most commonly used.
5.6 Work-to-break is dependent on the relationship of force to elongation. It is a measure of the ability of a textile structure to
absorb mechanical energy. Breaking toughness is work-to-break per unit mass.
5.7 It should be emphasized that, although the preceding parameters are related to the performance of a textile-reinforced
product, the actual configuration of the product is significant. Shape, size, and internal construction also can have appreciable effect
on product performance. It is not possible, therefore, to evaluate the performance of a textile reinforced product in terms of the
reinforcing material alone.
5.8 If there are differences of practical significance between reported test results for two laboratories (or more), comparative
tests should be performed to determine if there is a statistical bias between them, using competent statistical assistance. As a
minimum, test samples should be used that are as homogeneous as possible, that are drawn from the material from which the
disparate test results were obtained, and that are randomly assigned in equal numbers to each laboratory for testing. Other materials
with established test values may be used for this purpose. The test results from the two laboratories should be compared using a
statistical test for unpaired data, at a probability level chosen prior to the testing series. If a bias is found, either its cause must be
found and corrected, or future test results must be adjusted in consideration of the known bias.
6. Apparatus
6.1 Tensile Testing Machine—A single-strand tensile testing machine of the constant rate of extension (CRE) type. The tensile
testing equipment can be either manually operated or can be an automated device. The specifications and methods of calibration
and verification of these machines shall conform to Specification D76. The tester shall be equipped with an electronic data
acquisition and data evaluation system.
6.1.1 Clamps:
D7269/D7269M − 20
6.1.1.1 Manually Operated System—Bollard type clamps, in which the specimen is gripped between plane-faced jaws and then
makes a partial turn (wrap angle) around a curved extension (or other type of snubbing device) of one jaw before passing to the
other similar clamp (see Fig. 1 and Fig. 2). Clamps with a wrap angle of 180° are required for yarns with a linear density up to
3500 decitex [3000 denier]. For linear densities above 3500 decitex [3000 denier], clamps with a wrap angle of 270° are
recommended to prevent slippage. See Note 1.
6.1.1.2 Automated Device—Use the clamping system supplied. See Note 1.
6.1.1.3 Clamps shall grip the test specimen without spurious slippage or damage to the test specimen which can result in jaw
breaks. The clamps shall maintain constant gripping conditions during the test by means of pneumatic or hydraulic clamps. The
surface of the jaws in contact with the specimen shall be of a material and configuration that minimizes slippage and/or specimen
failure in the clamping zone.
6.1.2 Gauge Length—The gauge length shall be the total length of yarn measured between the clamping point A of the first
clamp and the point B of the second clamp in the starting position (see Fig. 2).
NOTE 1—The selected testing equipment (tester, clamp, gauge length) is known to have an influence on the properties measured (see Section 19, Table
8). A method for eliminating the influences introduced by the selected testing equipment is given in Appendix X1.
6.1.3 Use a crosshead travel rate in mm/min [in./min] of 50 % of the nominal gauge length in millimeters [inches] of the
specimen for para-aramids; 120 % of the nominal gauge length in millimeters [inches] of the specimen for meta-aramids.
7. Sampling
7.1 Remove and discard a minimum of 25 m [27 yd] from the outside of the package before taking the sample or any specimens.
7.2 Yarn:
7.2.1 Packages—For acceptance testing, sample each lot as directed in Practice D2258. Place each laboratory sampling unit in
a moisture-proof polyethylene bag or other moisture-proof container to protect the samples from atmospheric changes until ready
to condition the samples in the atmosphere for testing aramids. Take the number of specimens for testing specified for the specific
property measurement to be made.
7.2.2 Beams—For acceptance testing, sample by winding yarns on a tube or spool by means of a winder using a tension of 5
6 1 mN/tex [0.05 6 0.01 gf/den]. Take the yarn from the outside beam layers unless there is a question or disagreement regarding
the shipment; in this case, take the sample only after removing yarn from the beam to a radial depth of 6 mm [ ⁄4 in.] or more to
minimize the effects of handling and atmospheric changes that may have occurred during shipment or storage. Place each
laboratory sampling unit in a moisture-proof polyethylene bag or other moisture-proof container to protect the samples from
atmospheric changes until ready to condition the samples in the atmosphere for testing aramids. Take the number of specimens for
testing specified for the specific property measurement to be made.
7.3 Cord:
7.3.1 Number of Samples and Specimens—The size of an acceptance sampling lot of tire cord shall be not more than one truck
or rail car load or as determined by agreement between the purchaser and the supplier. Take samples at random from each of a
number of cones, tubes, bobbins, or spools within a lot to be as representative as possible within practical limitations. Make only
one observation on an individual package for each physical property determination. Take the number of samples, therefore, that
will be sufficient to cover the total number of specimens required for the determination of all physical properties of the tire cord.
The recommended number of specimens is included in the appropriate sections of specific test methods covered in this standard.
Where such is not specified, the number of specimens is as agreed upon between buyer and supplier.
7.3.2 Preparation of Samples—If specimens are not taken directly from the original package, preferably wind the sample on a
tube or spool by means of a winder using a tension of 5 6 1 mN/tex [0.05 6 0.01 gf/den]. If the sample is collected as a loosely
wound package, or in the form of a skein, some shrinkage invariably will occur, in which case, report that the observed results
were determined on a relaxed sample. Use care in handling the sample. Discard any sample subjected to any change of twist,
kinking, or making any bend with a diameter less than 10 times the yarn/cord thickness (or diameter). Place the sample in a
FIG. 1 Example Bollard Type Clamps
D7269/D7269M − 20
FIG. 2 Gauge Length in Bollard Type Jaws
moisture-proof polyethylene bag or other moisture-proof container to protect it from atmospheric changes until ready to condition
the sample in the test atmosphere for aramids.
8. Conditioning
8.1 Bring all specimens of yarn and cord to moisture equilibrium for testing in the atmosphere for testing aramids as directed
in Practice D1776. Report the option used.
8.1.1 The moisture equilibrium of conditioned aramids can be affected by heat and humidity conditions to which the samples
have been previously exposed.
9. Sample Preparation
9.1 Because of the difficulty of securing the same tension in all the filaments and because of slippage in the clamps, variable
results may be obtained when testing flat multifilament yarns. Therefore, a defined amount of twist must be inserted prior to testing.
Machine twisting by means of a ring twister is recommended. The ring twisters can be equipped with a guiding eyelet with either
a variable or a fixed distance to the traveller (the latter resulting in a more uniform twist tension). The twist tension should be
approximately 10 mN/tex [0.10 gf/den]. If used, anti-balloon rings must be of a material that will not damage the yarn. A manual
or mechanical twister can also be used in the absence of a ring twister, provided the RPM is calibrated and verified with a tolerance
of 20 6 0.1 revolutions at a frequency based on use. For meta-aramid, the inserted twist is 120 tpm [3.0 tpi]. For para-aramid yarns
the amount of twist to be inserted depends upon the linear density and is approximately:
Linear density Twist
dtex tpm
180 < LD < 240 230
240 < LD < 380 190
380 < LD < 500 160
500 < LD < 650 140
650 < LD < 775 125
775 < LD < 1050 110
1050 < LD < 1400 95
1400 < LD < 2100 80
2100 < LD < 4500 60
4500 < LD < 7000 45
7000 < LD < 9500 35
9500 > LD 30
NOTE 2—The twist level per range is based on the equation twist@Tpm#5 .
=LD tex
@ #
9.2 Inserting twist for tensile testing has the following effects on the test results:
9.2.1 Modestly increases breaking force; too much or too low twist reduces breaking force,
9.2.2 Increases elongation at break, and
D7269/D7269M − 20
9.2.3 Reduces modulus.
10. Linear Density
10.1 Scope—This test method is used to determine the linear density of yarn or cord for use in the calculation of tensile
properties such as modulus and tenacity at break.
10.2 Procedure:
10.2.1 Determine linear density as directed in Option 1 of Test Method D1907 or use an Automated Tester as directed in Test
Method D6587. For both test methods, condition the yarn as specified in Section 8.
10.2.2 If scoured oven-dried linear density is needed, use Test Method D1907, Option 5.
10.3 Report the method used and the average linear density of the sample.
11. Breaking Force of Conditioned Yarns and Cords
11.1 Scope—This test method is used to determine the breaking force of yarns and cords after conditioning in the atmosphere
for testing aramids as defined in Practice D1776. Make all tests on the conditioned yarns and cords in the atmosphere for testing
aramids as directed in Practice D1776.
11.2 Number of Specimens—Perform five tests per specimen.
11.3 Procedure—Select a loading cell and the settings of the tensile tester such that the estimated breaking force of the specimen
will fall in the range from 10 to 90 % of the full-scale force of the load cell used. This selection of the full scale force may be done
manually by the operator before the start of the test or by electronic means or computer control during the test by automatically
adjusting the amplification of the load cell amplifier. Adjust the distance between the clamps measured from nip to nip of the jaws
of the clamps (Fig. 2) on the testing machine. For meta-aramids, use 250 6 1 mm [10.00 6 0.05 in.]. For para-aramids, the gauge
length is 500 6 2 mm [20.0 6 0.1 in.]. For bollard type clamps with a wrap angle of 270° a gauge length of 635 6 2 mm [0.0
6 0.1 in.] is recommended. Remove the test material from the specimen or sample and handle it to prevent any change in twist
prior to closing the jaws of the clamps. Do not touch that portion of the material that will be between the clamps with bare hands.
Depending on the equipment being used and the availability of on-line computer control and data processing, either can be used:
Slack Start procedure (preferred procedure, see 11.3.1) or
Pretension–start procedure (see 11.3.2)
11.3.1 Slack Start Procedure—Thread one end of the specimen between the jaws of one of the clamps and close it. Place the
other end of the specimen through the jaws of the second clamp and keep the specimen just slack (zero tension) and close the
clamp, taking care that the thread is positioned in the centerline of the jaws of the clamp. Operate the testing machine at the rate
as specified in 6.1.3 and stretch the specimen until it ruptures. When the specimen breaks, read the breaking force (BF) (maximum
force) in Newton [pounds-force]. Discard tests that do not break within the free length between the clamps. If the clamps are of
the air-actuated type, adjust the air pressure to prevent specimens slipping in the jaws, but keep the air pressure below the level
that will cause specimens to break at the edge of the jaws. This slack start procedure has the effect that the nominal gauge length
of the specimen will be slightly greater as specified in 11.3.
11.3.2 Pretension-Start Procedure—Use a tensioning device that applies a pretension corresponding to 20 6 1 mN/tex [0.20 6
0.01 gf/den] for aramid fibers. This device may be a weight, a spring, or an air-actuated mechanism. Thread one end of the
specimen between the jaws of the clamp connected to the loading cell and close it. Place the other end through the jaw of the
second clamp and fix a pretension weight to the unclamped end or pull the end of the specimen until the specified pretension is
applied. Close the second clamp and operate the testing machine at the rate specified in 6.1.3. When the specimen breaks (ruptures),
read the breaking force BF (maximum force), in Newton [pounds-force]. Discard tests that do not break within the free length
between the clamps. If the clamps are of the air-actuated type, adjust the air pressure so that specimens will not slip in the jaws,
but keep air pressure below the level that will cause specimens to break at the edge of the jaws. The following notes provide useful
information in obtaining more consistent results in tensile testing:
NOTE 3—When arbitration of test data is involved, use care in the application of the pretension force that may be specified because the actual pretension
in the specimen commonly is different from the amount applied externally because of losses due to friction in the clamp. Check the pretension before
starting the testing machine. The actual pretension can be measured by strain gauges. Other tension-measuring instruments with sufficient accuracy may
be used, provided that the specimen is threaded through the instrument prior to being placed in the second clamp. This procedure is necessary because
many instruments require appreciable displacement of the specimen.
NOTE 4—When arbitration is not involved, one of the following approximations of the specified pretension may be used. Either exert a force of 120
% of the nominal pretension to the unclamped end of the specimen prior to closing the second grip, or apply one of the forces listed as follows for the
specified groups of yarn and cord sizes to secure the necessary pretension.
Linear Density of Specimen Amount of Force
N [gf]
Below 400 tex [3600 denier] 1 [100]
400 to 600 tex [3600 to 5400 denier] 2 [200]
600 to 800 tex [5400 to 7200 denier] 3 [300]
Above 800 tex [7200 denier] 4 [400]
D7269/D7269M − 20
NOTE 5—When using a CRE-type tensile machine, a third technique is to close the upper clamp, then apply pretension by pulling on the specimen until
the recorder pen moves approximately ⁄2-chart division from the zero line on the chart when using a force scale that is the same as that used for
determining the breaking force.
11.3.3 The velocity of conditioned air flowing across a specimen while determining tensile properties can have a measurable
effect on the breaking force and elongation at break because of the Gough-Joule effect. The magnitude ofthis effect depends on
the type of fiber, air velocity, and sample history. Interlaboratory testing of nylon, polyester, and rayon cords indicates that air
velocities of less than 250 mm/s [50 ft/min] across the specimen will not significantly bias the comparison of cord properties
between laboratories.
11.4 Calculate the average and standard deviation of breaking force from the individual breaking forces.
NOTE 6—The preferred term to use is BF (Breaking Force), however the use of BS (Breaking Strength) for the average value is permitted.
11.5 Report results as stated in Section 18.
11.6 Precision and Bias:
11.6.1 Precision—See Section 19.
11.6.2 Bias—See 19.3.
12. Breaking Tenacity and Stress at Break of Conditioned Yarns and Cords
12.1 Scope—This test method is used to determine the breaking tenacity of yarns and cords after conditioning in the atmosphere
for testing aramids.
12.2 Calculation—Calculate the breaking tenacity of the sample in terms of milli-Newton per tex (mN/tex) [grams-force per
denier (gf/den)] from the breaking force and the linear density using Eq 1 and 2:
BF ·1000
n
BT 5 (1)
n
LD
t
BF ·454
l
BT 5 (2)
g
LD
d
where:
BT = breaking tenacity, mN/tex,
n
BT = breaking tenacity, gf/den,
g
BF = breaking force, N,
n
BF = breaking force, lbf,
l
LD = average linear density of sample, tex, and
t
LD = average linear density of sample, denier.
d
12.2.1 Calculate the average and standard deviation of the breaking tenacity of the sample.
12.3 Report results as stated in Section 18.
12.4 Precision and Bias:
12.4.1 Precision—See Section 19.
12.4.2 Bias—See Section 19.3.
12.5 Stress or Break:
12.5.1 Scope—This test method is used to determine the breaking force per cross-section area of yarns and cords after
conditioning in the atmosphere for testing aramids.
12.5.2 Calculate the specific stress at break using Eq 3:
Rho
SB 5 BT · (3)
n
where additonally:
SB = stress at break in MPa, and
Rho = density in kg/m .
12.5.2.1 The density is either:
(1) determined according to Test Method D3800, Procedure A—Buoyancy (Archimedes) Method; test temperature as in
Section 8.
(2) the value determined by the supplier (Test Method D3800, see (1)).
(3) the nominal value for para-aramids fo 1440 kg/m .
12.5.3 Calculate the average and standard deviation of the stress at break of the sample.
Jones, R. E. and Desson, M. J., “Adiabatic Effects on Tensile Testing,” Journal of the I.R.I, June 1967.
D7269/D7269M − 20
12.5.4 Report results as stated in Section 18.
12.5.5 Precision and Bias:
12.5.5.1 Precision—See Section 19.
12.5.5.2 Bias—See 19.3.
13. Elongation at Break of Conditioned Yarns and Cords
13.1 Scope—This test method is used to determine the elongation at break of yarns and cords after conditioning in the
atmosphere for testing aramids.
13.2 Procedure—Determine the elongation at break of each conditioned specimen when determining its breaking force (see
Section 11). Read the extension at the breaking force by electronic means. The general equation for elongation at break is given
in Eq 4:
E
bf
EB 5 ·100 % (4)
S D
L
o
where:
EB = elongation at break, %,
E = extension of specimen at the breaking force, mm [in.], and
bf
L = length of the specimen, under specified pretension measured from nip-to-nip of the holding clamps, mm [in.].
o
13.2.1 Pretension Start—Use Eq 4.
13.2.2 Slack Start—Calculate the gauge length (L ) to include the slack using Eq 5:
o
L 5 L 1DP (5)
o s
where:
L = length of the specimen, under specified pretension, measured from nip-to-nip of the holding clamps, mm [in.],
o
L = gauge length after clamping specimen (absolute distance nip-to-nip before movement of crosshead), mm [in.], and
s
DP = displacement of crosshead to reach the specified pretension of the specimen (see Fig. 3), mm [in.].
13.2.2.1 The pretension for aramid corresponds with 20 6 1 mN/tex [0.20 6 0.01 gf/den].
13.2.2.2 The general equation for elongation at break for the slack start procedure is given in Eq 6:
F = Pretension force
DP = Slack
BF = Breaking force
E = Extension at breaking force
BF
FASE = Force at specified elongation
FIG. 3 Force-Extension Curve
D7269/D7269M − 20
E
bf
EB 5 ·100 % (6)
L 1DP
s
where:
EB = elongation at break, %,
E = extension of specimen at the breaking force, mm [in.],
bf
L = gauge length after clamping specimen (absolute distance nip-to-nip before movement of crosshead), mm [in.], and
s
DP = displacement of crosshead to reach the specified pretension of the specimen (see Fig. 1), mm [in.].
13.2.3 Calculate the average and standard deviation of the elongation at break of the sample.
13.2.4 For calculating the FASE (Section 14), Chord Modulus (Section 15), and Work-to-Break (Section 16), it is required to
calculate the elongation at any force from the corresponding extension.
13.3 Report results as stated in Section 18.
13.4 Precision and Bias:
13.4.1 Precision—See Section 19.
13.4.2 Bias—See 19.3.
14. Force at Specified Elongation (FASE) of Conditioned Yarns and Cords
14.1 Scope—This test method is used to determine the force at specified
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