ASTM D7205/D7205M-21

Standard Test Method for Tensile Properties of Fiber Reinforced Polymer Matrix Composite Bars

SIGNIFICANCE AND USE
5.1 This test method is designed to produce longitudinal tensile strength and elongation data. From a tension test, a variety of data are acquired that are needed for design purposes. Test factors relevant to the measured tensile response of bars include specimen preparation, specimen conditioning, environment of testing, specimen alignment and gripping, and speed of testing. Properties, in the test direction, that may be obtained from this test method include:  
5.1.1 Maximum tensile force,  
5.1.2 Ultimate tensile strength,  
5.1.3 Ultimate tensile strain,  
5.1.4 Tensile chord modulus of elasticity, and  
5.1.5 Stress-strain curve.
SCOPE
1.1 This test method determines the quasi-static longitudinal tensile strength and elongation properties of fiber reinforced polymer matrix (FRP) composite bars commonly used as tensile elements in reinforced, prestressed, or post-tensioned concrete.
Note 1: Additional procedures for determining tensile properties of polymer matrix composites may be found in Test Methods D3039/D3039M and D3916.  
1.2 Linear elements used for reinforcing Portland cement concrete are referred to as bars, rebar, rods, or tendons, depending on the specific application. This test method is applicable to all such reinforcements within the limitations noted in the method. The test articles are referred to as bars in this test method. In general, bars have solid cross-sections and a regular pattern of surface undulations or a coating of bonded particles, or both, that promote mechanical interlock between the bar and concrete. The test method is also appropriate for use with linear segments cut from a grid. Specific details for preparing and testing of bars and grids are provided. In some cases, anchors may be necessary to prevent grip-induced damage to the ends of the bar or grid. Suggestions for a grouted type of anchor are provided in Appendix X1.  
1.3 The strength values provided by this method are short-term static strengths that do not account for sustained static or fatigue loading. Additional material characterization may be required, especially for bars that are to be used under high levels of sustained or repeated loading.  
1.4 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.  
1.4.1 Within the text, the inch-pound units are shown in brackets.  
1.5 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.  
1.6 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: 14-May-2021
• ICS: 91.100.40 - Products in fibre-reinforced cement
• Technical Committee: D30 - Composite Materials
• Drafting Committee: D30.10 - Composites for Civil Structures

Relations

• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM D5229/D5229M-20 - Standard Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials
• Effective Date: 01-Mar-2020
• Refers: ASTM D883-20 - Standard Terminology Relating to Plastics
• Effective Date: 01-Jan-2020
• Refers: ASTM D3878-19a - Standard Terminology for Composite Materials
• Effective Date: 15-Oct-2019
• Refers: ASTM D883-19c - Standard Terminology Relating to Plastics
• Effective Date: 01-Aug-2019
• Refers: ASTM D3878-19 - Standard Terminology for Composite Materials
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19a - Standard Terminology Relating to Plastics
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2019
• Refers: ASTM D883-18a - Standard Terminology Relating to Plastics
• Effective Date: 01-Dec-2018
• Refers: ASTM D883-18 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2018
• Refers: ASTM D3878-18 - Standard Terminology for Composite Materials
• Effective Date: 01-Apr-2018
• Refers: ASTM E456-13A(2017)e3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E456-13A(2017)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017

Overview

ASTM D7205/D7205M-21 is the Standard Test Method for Tensile Properties of Fiber Reinforced Polymer (FRP) Matrix Composite Bars. Developed by ASTM International, this test method provides procedures for determining quasi-static longitudinal tensile strength and elongation properties of FRP composite bars, mainly used in reinforced, prestressed, and post-tensioned concrete. By specifying standardized procedures for specimen preparation, conditioning, testing, and data reporting, ASTM D7205/D7205M-21 ensures reliable tensile property data for critical structural applications.

Key Topics

• Tensile Testing of FRP Bars: The standard focuses on measuring the ultimate tensile strength, maximum tensile force, ultimate tensile strain, modulus of elasticity, and stress-strain response of composite bars.
• Specimen Preparation and Conditioning: Proper specimen preparation, environmental conditioning, and alignment are critical for accurate test results. The document outlines clear requirements for labeling, geometry, and conditioning of specimens.
• Testing Procedures: The method details apparatus specifications, including micrometers, testing machines, grips, extensometers, and environmental chambers, emphasizing alignment and gripping to avoid premature failures.
• Data Collection and Reporting: Stress, strain, modulus of elasticity, and failure mode are recorded, with statistical analysis such as average values, standard deviation, and coefficient of variation to ensure robust data for design and quality assurance.
• Applicability: The method applies to FRP bars, rods, tendons, and linear elements with solid cross-sections, suitable for all such reinforcements within the limitations noted. It covers both standard and custom geometries, including linear grid segments.

Applications

The tensile properties determined by ASTM D7205/D7205M-21 are critical for:

• Structural Concrete Reinforcement: FRP bars tested to this standard are used as structural reinforcement in buildings, bridges, parking structures, marine environments, and other reinforced concrete applications, offering corrosion resistance and enhanced performance over steel rebar.
• Material Qualification and Quality Control: The method is necessary for manufacturers and engineers to qualify new FRP bar materials, compare products, and monitor production quality.
• Design and Engineering: Accurate tensile property data inform structural design calculations, ensuring the safe and effective use of FRP bars in prestressed, post-tensioned, and conventionally reinforced concrete elements.
• Research and Innovation: The standard is widely used in academic and industrial research to study novel fiber-reinforced composite formulations or compare new reinforcement technologies.

Related Standards

ASTM D7205/D7205M-21 references several other key standards for testing, terminology, and specification of composite materials:

• ASTM D3039/D3039M: Test Method for Tensile Properties of Polymer Matrix Composite Materials
• ASTM D3916: Test Method for Tensile Properties of Pultruded Glass-Fiber-Reinforced Plastic Rod
• ASTM D7957/D7957M: Specification for Solid Round Glass Fiber Reinforced Polymer Bars for Concrete Reinforcement
• ASTM D3171: Test Methods for Constituent Content of Composite Materials
• ASTM D792: Test Methods for Density and Specific Gravity of Plastics
• ASTM A615/A615M: Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement

By following ASTM D7205/D7205M-21, stakeholders in construction, materials science, and civil engineering sectors can ensure that FRP composite bars are tested and reported consistently and accurately, supporting both regulatory compliance and safe, optimized structural design.

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: D7205/D7205M − 21
Standard Test Method for
Tensile Properties of Fiber Reinforced Polymer Matrix
Composite Bars
This standard is issued under the fixed designation D7205/D7205M; 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 1.4.1 Within the text, the inch-pound units are shown in
brackets.
1.1 Thistestmethoddeterminesthequasi-staticlongitudinal
1.5 This standard does not purport to address all of the
tensile strength and elongation properties of fiber reinforced
safety concerns, if any, associated with its use. It is the
polymer matrix (FRP) composite bars commonly used as
responsibility of the user of this standard to establish appro-
tensile elements in reinforced, prestressed, or post-tensioned
priate safety, health, and environmental practices and deter-
concrete.
mine the applicability of regulatory limitations prior to use.
NOTE 1—Additional procedures for determining tensile properties of
1.6 This international standard was developed in accor-
polymer matrix composites may be found in Test Methods D3039/
dance with internationally recognized principles on standard-
D3039M and D3916.
ization established in the Decision on Principles for the
1.2 Linear elements used for reinforcing Portland cement
Development of International Standards, Guides and Recom-
concrete are referred to as bars, rebar, rods, or tendons,
mendations issued by the World Trade Organization Technical
depending on the specific application. This test method is
Barriers to Trade (TBT) Committee.
applicable to all such reinforcements within the limitations
noted in the method. The test articles are referred to as bars in
2. Referenced Documents
this test method. In general, bars have solid cross-sections and
2.1 ASTM Standards:
a regular pattern of surface undulations or a coating of bonded
D792 Test Methods for Density and Specific Gravity (Rela-
particles, or both, that promote mechanical interlock between
tive Density) of Plastics by Displacement
the bar and concrete. The test method is also appropriate for
D883 Terminology Relating to Plastics
use with linear segments cut from a grid. Specific details for
D3039/D3039M Test Method for Tensile Properties of Poly-
preparing and testing of bars and grids are provided. In some
mer Matrix Composite Materials
cases, anchors may be necessary to prevent grip-induced
D3878 Terminology for Composite Materials
damagetotheendsofthebarorgrid.Suggestionsforagrouted
D3916 Test Method for Tensile Properties of Pultruded
type of anchor are provided in Appendix X1.
Glass-Fiber-Reinforced Plastic Rod
1.3 The strength values provided by this method are short-
D5229/D5229M TestMethodforMoistureAbsorptionProp-
term static strengths that do not account for sustained static or
erties and Equilibrium Conditioning of Polymer Matrix
fatigue loading. Additional material characterization may be
Composite Materials
required, especially for bars that are to be used under high
D7957/D7957M Specification for Solid Round Glass Fiber
levels of sustained or repeated loading.
Reinforced Polymer Bars for Concrete Reinforcement
E4 Practices for Force Verification of Testing Machines
1.4 Units—The values stated in either SI units or inch-
E6 Terminology Relating to Methods of Mechanical Testing
pound units are to be regarded separately as standard. The
E83 Practice for Verification and Classification of Exten-
values stated in each system are not necessarily exact equiva-
someter Systems
lents; therefore, to ensure conformance with the standard, each
E122 Practice for Calculating Sample Size to Estimate,With
system shall be used independently of the other, and values
Specified Precision, the Average for a Characteristic of a
from the two systems shall not be combined.
Lot or Process
E456 Terminology Relating to Quality and Statistics
This test method is under the jurisidiction of ASTM Committee D30 on
Composite Materials and is the direct responsibility of Subcommittee D30.10 on
Composites for Civil Structures. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 15, 2021. Published June 2021. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2006. Last previous edition approved in 2016 as D7205/ Standards volume information, refer to the standard’s Document Summary page on
D7205M – 06(2016). DOI: 10.1520/D7205_D7205M-21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7205/D7205M − 21
E1012 Practice for Verification of Testing Frame and Speci-
A = cross-sectional area of a bar.
men Alignment Under Tensile and Compressive Axial
CV = sample coefficient of variation, in percent.
Force Application
d = effective diameter of a bar.
E = modulus of elasticity in the test direction.
3. Terminology
F = ultimate tensile strength.
tu
K = total number of stress-strain data points used in the
3.1 Terminology D3878 defines terms relating to high-
modulus calculation.
modulus fibers and their composites. Terminology D883 de-
L = free length of specimen (length between anchors).
fines terms relating to plastics. Terminology E6 defines terms
L = anchor length.
a
relating to mechanical testing. Terminology E456 and Practice
L = extensometer gage length.
g
E122 define terms relating to statistics and the selection of
n = number of specimens.
sample sizes. In the event of a conflict between terms,
P = force carried by specimen.
Terminology D3878 shall have precedence over the other
P = maximum force carried by a test coupon before
max
terminology standards.
failure.
3.2 Definitions of Terms Specific to This Standard: r = coefficient of determination.
s = sample standard deviation.
3.2.1 anchor, n—a protective device placed on each end of
n–1
x = measured or derived property.
a bar, between the bar and the grips of the tensile testing
i
x¯ = sample mean (average).
machine, to prevent grip-induced damage. Usually used on
δ = extensional displacement.
bars with irregular surfaces, as opposed to flat strips where
ε = indicated normal strain from strain transducer.
bonded tabs are more typical.
σ = normal stress.
3.2.2 bar, n—a linear element, often with surface undula-
tions or a coating of particles that promote mechanical inter-
4. Summary of Test Method
lock with concrete.
4.1 A fiber reinforced polymer (FRP) bar, preferably fitted
3.2.3 effective bar diameter, n—ageometricvaluerepresent-
with anchors, is mounted in a mechanical testing machine and
ing the diameter of a circle which has an enclosed area equal
monotonically loaded in tension to failure while recording
to the nominal cross-sectional area of a bar or the measured
force, longitudinal strain, and longitudinal displacement.
cross-sectional area of a bar, as appropriate.
4.2 AnchorsasdescribedinAppendixX1arerecommended
3.2.4 grid, n—a two-dimensional (planar) or three-
but not required. Alternative methods for attaching the speci-
dimensional (spatial) rigid array of interconnected FRP bars
mens to the testing machine are acceptable, but must allow for
that form a contiguous lattice that can be used to reinforce
the full strength of the bar to be developed and for the failure
concrete. The lattice can be manufactured with integrally
of the specimens to occur away from the attachments.
connected bars or constructed of mechanically connected
individual bars. The grid bar elements have transverse dimen-
5. Significance and Use
sions typically greater than 3 mm [0.125 in.].
5.1 This test method is designed to produce longitudinal
3.2.5 measured cross-sectional area, n—cross-sectional
tensile strength and elongation data. From a tension test, a
area of a bar, including any bond enhancing surface treatments
variety of data are acquired that are needed for design
such as deformations, lugs, and sand coating, determined over
purposes.Testfactorsrelevanttothemeasuredtensileresponse
at least one representative length, measured according to
of bars include specimen preparation, specimen conditioning,
11.2.4.1.
environment of testing, specimen alignment and gripping, and
3.2.6 nominal cross-sectional area, n—the cross-sectional
speed of testing. Properties, in the test direction, that may be
area of a standard FRP concrete reinforcing bar as originally
obtained from this test method include:
developedforglassFRPbarsinSpecificationD7957/D7957M.
5.1.1 Maximum tensile force,
5.1.2 Ultimate tensile strength,
3.2.7 nominal value, n—a value, existing in name only,
5.1.3 Ultimate tensile strain,
assigned to a measurable property for the purpose of conve-
5.1.4 Tensile chord modulus of elasticity, and
nient designation. Tolerances may be applied to a nominal
5.1.5 Stress-strain curve.
value to define an acceptable range for the property.
3.2.8 representative length, n—the minimum length of a bar
6. Interferences
that contains a repeating geometric pattern that, placed end-to-
6.1 The results from the procedures presented are limited to
end, reproduces the geometric pattern of a continuous bar
the material and test factors listed in Section 5.
(usually used in reference to bars having surface undulations
for enhancing interlock with concrete).
6.2 Gripping—The method of gripping has been known to
3.2.9 surface undulation, n—variation in the area, cause premature tensile failures in bars. Anchors, if used,
orientation, or shape of cross section of a bar along its length, should be designed in such a way that the full tensile capacity
intended to enhance mechanical interlock between a bar and can be achieved without slip throughout the length of the
concrete, made by any of a number of processes such as, for anchor during the test.
example, indentation, addition of extra materials, and twisting.
6.3 System Alignment—Excessive bending may cause pre-
3.3 Symbols: mature failure, as well as a highly inaccurate modulus of
D7205/D7205M − 21
elasticity determination. Every effort should be made to elimi- prevent slippage between the grip face and the specimen or
nate bending from the test system. Bending may occur due to anchor. It is highly desirable to use grips that are rotationally
misalignment of the bar within anchors or grips or associated self-aligning to minimize bending stresses in the specimen.
fixturing, or from the specimen itself if improperly installed in The grips shall be aligned in accordance with Practice E1012
the grips or if it is out-of-tolerance due to poor specimen and shall not bias failure location in the bar.
preparation. See Practice E1012 for verification of specimen
7.3 Anchors—Use of a rigid pipe-shaped anchor as an
alignment under tensile loading.
interface between the bar and the grips or loading head of the
6.4 Measurement of Cross-Sectional Area—The measured
testing machine is recommended to prevent stress concentra-
cross-sectional area of the bar is determined by immersing a
tions and consequent downward biasing of measured strength.
prescribed length of the specimen in water to determine its
SuggestionsforagroutedanchorareprovidedinAppendixX1.
buoyant weight. Bar configurations that trap air during immer-
7.3.1 Attachment of anchors to loading heads shall be by
sion (aside from minor porosity) cannot be assessed using this
threaded connectors between the anchors and loading head or
method.This method may not be appropriate for bars that have
by grips. Details of this attachment are shown in Fig. X1.3.
large variations in cross-sectional area along the length of the
7.4 Strain-Indicating Device—Longitudinal strain shall be
bar.
measured by an appropriate strain transducer as long as
6.5 Material-Related Factors—Material-related factors
attachmentofthisdevicedoesnotcausedamagetothebar(see
such as constituent materials, void volume content, reinforce-
Note 3).
ment volume content, methods of fabrication, and fiber rein-
forcement architecture can affect the tensile properties of bars. NOTE 3—For most bars, the application of surface-bonded strain gages
is impractical due to surface undulations (for example, braided, twisted,
and indented bars). Strain gages of a suitable gage length can be used if
7. Apparatus
the surface of the bar can be smoothed with a polymer resin such as epoxy
to provide a suitable bonding surface so that measurements are equivalent
7.1 Micrometers—The micrometer(s) shall use a suitable
to those provided by an extensometer meeting the requirements of 7.4.1.
size diameter ball-interface on irregular surfaces and a flat
anvil interface on machined edges or very-smooth tooled
7.4.1 Extensometers—Extensometers shall satisfy, at a
surfaces. The accuracy of the instruments shall be suitable for
minimum, Practice E83, Class B-2 requirements for the strain
reading to within 1 % of the intended measurement.
range of interest, and shall be calibrated over that strain range
in accordance with Practice E83. The extensometer shall be
7.2 Testing Machine—The testing machine shall be in con-
essentially free of inertia-lag at the specified speed of testing.
formance with Practices E4, and shall satisfy the following
The gage length of the extensometer, L , shall be not less than
requirements: g
eight times the effective bar diameter, nor less than one
7.2.1 Testing Machine Heads—The testing machine shall
representative length. The extensometer shall be centered on
have both an essentially stationary head and a movable head.
the mid-length position of the bar, not less than eight effective
7.2.2 Drive Mechanism—The testing machine drive mecha-
bar diameters from either anchor.
nism shall be capable of imparting to the movable head a
7.4.1.1 Temperature compensation is recommended when
controlled displacement rate with respect to the stationary
not testing at Standard Laboratory Atmosphere. When
head. The displacement rate of the movable head shall be
appropriate, use either (a) a traveler specimen (dummy speci-
capable of being regulated as specified in 11.3.
men) with identical bar material and extensometer(s) or (b)an
7.2.3 Force Indicator—The testing machine force-sensing
extensometer calibrated for temperature changes.
device shall be capable of indicating the total force being
carried by the specimen. This device shall be essentially free
7.5 Environmental Test Chamber—Anenvironmentalcham-
from inertia-lag at the specified rate of testing and shall
ber is required for conditioning and test environments other
indicate the force with an accuracy over the load range(s) of
than ambient laboratory conditions. These chambers shall be
interest of within 6 1 % of the indicated value, as specified by
capable of maintaining the required relative temperature to
Practices E4. The force range(s) of interest may be fairly low
within 63°C[65 °F] and the required relative humidity level
formodulusevaluation,muchhigherforstrengthevaluation,or
to within 65 %RH. In addition, the chambers may have to be
both, as required.
capable of maintaining environmental conditions such as fluid
exposure or relative humidity during the conditioning and
NOTE2—Obtainingprecisionforcedataoveralargerangeofinterestin
the same test, such as when both elastic modulus and ultimate force are testing (see Section 10 and 11.4).
being determined, place extreme requirements on the force transducer and
its calibration. For some equipment, a special calibration may be required.
8. Sampling and Test Specimens
For some combinations of material and force transducer, simultaneous
precision measurement of both elastic modulus and ultimate strength may
8.1 Sampling—Test at least five specimens per test condi-
notbepossible,andmeasurementofmodulusandstrengthmayhavetobe
tion unless valid results can be gained through the use of fewer
performed in separate tests using a different force transducer range for
specimens, such as in the case of a designed experiment. For
each test.
statistically significant data, the procedures outlined in Practice
7.2.4 Grips—If grips are used, each head of the testing
E122 should be consulted. The method of sampling shall be
machine shall carry one grip for holding the specimen so that
reported.
the loading direction is coincident with the longitudinal axis of
thespecimen.Thegripsshallapplysufficientlateralpressureto 8.2 Geometry:
D7205/D7205M − 21
8.2.1 Overall Specimen Length and Gage Length—Thetotal 11.1.3 The environmental conditioning test parameters and
length of the specimen shall be the free length plus two times sealant used for the ends of the specimens.
the anchor length, L . The free length between the anchors, L,
a
11.2 General Instructions:
shallbenotlessthan380 mm[15 in.]norlessthan40timesthe
11.2.1 Report any deviations from this test method, whether
effective bar diameter for bars with effective diameter of
intentional or inadvertent.
26 mm [1.02 in.] or less. For bars with an effective diameter
11.2.2 Condition the specimens (specify either before or
larger than 26 mm [1.02 in.], the free length shall not be less
after attachment of anchors), as required. If test conditions are
than 20 times the effective bar diameter. The length of the
to be different from ambient laboratory conditions, it is
specimen in the grips and anchors (if used) shall be sufficient
recommended that anchors be applied before conditioning.
for adequate anchorage.
Condition the traveler coupons if they are to be used.
8.2.2 Labeling—The specimens shall be labeled so that they
11.2.3 Following final specimen machining and any
will be distinct from each other and traceable back to the raw
conditioning,butbeforethetensiontesting,measureandreport
material, and in a manner that will both be unaffected by the
the free length of specimen.
test and not influence the test.
11.2.4 Bar Area and Diameter—Either the measured cross-
sectional area or the nominal cross-sectional area as described
9. Calibration
in Specification D7957/D7957M is used to calculate stress and
9.1 The accuracy of all measuring equipment shall have
modulus of elasticity for any type of FRP bar. In either case,
certified calibrations that are current at the time of use of the
the measured cross-sectional area must be calculated and
equipment.
reported. If the measured cross-sectional area is not within
minimum and maximum area limits provided in Specification
10. Conditioning
D7957/D7957M, the nominal cross-sectional area may not be
used.
10.1 If not otherwise specified, the recommended pre-test
11.2.4.1 Measured Cross-sectional Area—The measured
condition is effective moisture equilibrium at a specific relative
area is calculated as the average of 5 representative specimens
humidity as established by Test Method D5229/D5229M;
however, if the test requestor does not explicitly specify a cut from the same bar stock as that used for the tensile test.
Conditioning of the cross-sectional area specimens is the same
pre-test conditioning environment, no conditioning is required
and the specimens may be tested as prepared. as that for the bars used for the tensile test.The volume of each
specimen shall be measured indirectly by the difference in
NOTE 4—The term “moisture,” as used in Test Method D5229/
mass of the specimen in the dry and fully immersed states
D5229M, includes not only the vapor of a liquid and its condensate, but
(refer to Test Methods D792 for test methods). The volume of
the liquid itself in large quantities, as for immersion.
the specimen is the mass of the specimen divided by the
10.2 The pre-test specimen conditioning process, to include
densityasmeasuredbyTestMethodsD792.Themeasuredarea
specified environmental exposure levels shall be reported with
is then found by dividing volume by the average length of the
the test data.
specimen. The average length of a typical bar specimen (for
10.3 If no explicit conditioning process is performed, the
example, circular or polygonal cross section) is found by
specimen conditioning process shall be reported as uncondi-
measuring the length of the outer edge of the specimen three
tioned and the moisture content as unknown.
times at the outer edge, rotating the specimen by 120 degrees
NOTE 5—If tensile specimens are to undergo environmental condition- 2 2
for each measurement. Record the area in units of mm [in. ].
ing to equilibrium, and are of such type or geometry that the weight
Effective bar diameter, d, is found by Eq 1:
change of the material cannot be properly measured by weighing the
specimen itself (such as a bar with anchors), then a traveler specimen of
d 5 2=~A/3.1416! (1)
the same cross-section geometry and appropriate size (but without
NOTE 7—The use of effective bar diameter may not be appropriate for
anchors)shallbeusedtodeterminewhenequilibriumhasbeenreachedfor
bars that are not solid and not substantially round in cross section.
the specimens being conditioned. The ends of tensile specimens and
NOTE 8—For a representative determination of area, specimens of at
traveler specimens shall be sealed with a water resistant sealant such as a
least 100 mm [4 in.] or one representative length (whichever is greater)
high grade, room-temperature curing epoxy to avoid end effects during
shall be used. The mass of a specimen may exceed the limit imposed by
conditioning.
Test Methods D792 (50 grams) for large diameter bars, but the procedure
may still be used.
11. Procedure
11.2.4.2 Nominal Cross-sectional Area—The nominal
11.1 Parameters to be specified prior to test:
cross-sectional area for FRP bars is described in Specification
11.1.1 The specimen sampling method, specimen type and
D7957/D7957M.
geometry, conditioning, and if required, traveler specimen
NOTE 9—For some applications, it is considered appropriate to use the
geometry.
nominal area for calculating stress and modulus of elasticity in FRP bars,
11.1.2 The tensile properties and data reporting format
as this is the practice for glass FRP bars. While Specification D7957/
desired.
D7957M was developed for glass FRP bars, the nominal cross-sectional
areas in the specification are considered suitable for any composite bar.
NOTE 6—Determine specific material property, accuracy, and data
reporting requirements before test for proper selection of instrumentation 11.2.5 Apply extensometers or strain gages to the specimen.
and data-recording equipment. Estimate operating stress and strain levels
11.3 Speed of Testing—The speed of testing shall be set to
to aid in transducer selection, calibration of equipment, and determination
of equipment settings. effect a nearly constant strain or stress rate in the gage section.
D7205/D7205M − 21
The speed of testing rate shall be selected so as to produce 13. Calculation
failure within 1 to 10 minutes from the beginning of force
13.1 Tensile Stress/Tensile Strength—Calculate the ultimate
application.
tensile strength using Eq 2and report the results to three
-1
11.3.1 The suggested standard strain rate is 0.01 min. If
significant figures. If the tensile modulus is to be calculated,
straincontrolisnotavailableonthetestingmachine,anominal
determinethetensilestressateachrequireddatapointusingEq
-1
cross-head speed of 0.01 min. times the specimen free length
3.
selected according to 8.2.1 can be used.
F 5 P /A (2)
tu max
11.3.2 The suggested standard stress rate is 300 MPa/min.
σ 5 P /A (3)
i i
[44 ksi/min.].
11.3.3 If the ultimate strength and strain of the material
where:
cannot be reasonably estimated, conduct initial trials using
F = Ultimate tensile strength, MPa [psi],
tu
standard speeds until failure is produced in 1 to 10 minutes
P = Maximum force prior to failure, N [lbf],
max
from the beginning of force application.
σ = Tensile stress at i-th data point, MPa [psi],
i
P = Force at i-th data point, N [lbf], and
i
11.4 Test Environment—Test at Standard Laboratory Atmo-
A = Cross-sectional area of the bar from 11.2.4,mm
sphere (2363 °C [7365 °F] and 50610 % RH) unless a
[in. ].
differ
...

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: D7205/D7205M − 06 (Reapproved 2016) D7205/D7205M − 21
Standard Test Method for
Tensile Properties of Fiber Reinforced Polymer Matrix
Composite Bars
This standard is issued under the fixed designation D7205/D7205M; 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 determines the quasi-static longitudinal tensile strength and elongation properties of fiber reinforced polymer
matrix (FRP) composite bars commonly used as tensile elements in reinforced, prestressed, or post-tensioned concrete.
NOTE 1—Additional procedures for determining tensile properties of polymer matrix composites may be found in test methodsTest Methods
D3039/D3039M and D3916.
1.2 Linear elements used for reinforcing Portland cement concrete are referred to as bars, rebar, rods, or tendons, depending on
the specific application. This test method is applicable to all such reinforcements within the limitations noted in the method. The
test articles are referred to as bars in this test method. In general, bars have solid cross-sections and a regular pattern of surface
undulations and/oror a coating of bonded particles particles, or both, that promote mechanical interlock between the bar and
concrete. The test method is also appropriate for use with linear segments cut from a grid. Specific details for preparing and testing
of bars and grids are provided. In some cases, anchors may be necessary to prevent grip-induced damage to the ends of the bar
or grid. Recommended details for the anchors Suggestions for a grouted type of anchor are provided in Annex A1Appendix X1.
1.3 The strength values provided by this method are short-term static strengths that do not account for sustained static or fatigue
loading. Additional material characterization may be required, especially for bars that are to be used under high levels of sustained
or repeated loading.
1.4 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in
each system mayare not benecessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be
used independently of the other. Combiningother, and values from the two systems may result in non-conformance with the
standard.shall not be combined.
1.4.1 Within the text, the inch-pound units are shown in brackets.
1.5 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 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.
This test method is under the jurisidiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.10 on Composites
for Civil Structures.
Current edition approved Nov. 1, 2016May 15, 2021. Published November 2016June 2021. Originally approved in 2006. Last previous edition approved in 20112016 as
D7205/D7205M–06(2011).D7205/D7205M – 06(2016). DOI: 10.1520/D7205_D7205M-06R16.10.1520/D7205_D7205M-21.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7205/D7205M − 21
2. Referenced Documents
2.1 ASTM Standards:
A615/A615M Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement
D792 Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement
D883 Terminology Relating to Plastics
D3039/D3039M Test Method for Tensile Properties of Polymer Matrix Composite Materials
D3171 Test Methods for Constituent Content of Composite Materials
D3878 Terminology for Composite Materials
D3916 Test Method for Tensile Properties of Pultruded Glass-Fiber-Reinforced Plastic Rod
D5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite
Materials
D7957/D7957M Specification for Solid Round Glass Fiber Reinforced Polymer Bars for Concrete Reinforcement
E4 Practices for Force Verification of Testing Machines
E6 Terminology Relating to Methods of Mechanical Testing
E83 Practice for Verification and Classification of Extensometer Systems
E122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or
Process
E456 Terminology Relating to Quality and Statistics
E1012 Practice for Verification of Testing Frame and Specimen Alignment Under Tensile and Compressive Axial Force
Application
E1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in Databases (Withdrawn 2015)
E1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases (Withdrawn 2015)
E1471 Guide for Identification of Fibers, Fillers, and Core Materials in Computerized Material Property Databases (Withdrawn
2015)
3. Terminology
3.1 Terminology in D3878 defines terms relating to high-modulus fibers and their composites. Terminology in D883 defines terms
relating to plastics. Terminology in E6 defines terms relating to mechanical testing. Terminology in E456 and in Practice E122
define terms relating to statistics and the selection of sample sizes. In the event of a conflict between terms, Terminology in D3878
shall have precedence over the other terminology standards.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 anchor, n—a protective device placed on each end of a bar, between the bar and the grips of the tensile testing machine, to
prevent grip-induced damage. Usually used on bars with irregular surfaces, as opposed to flat strips where bonded tabs are more
typical.
3.2.2 bar, n—a linear element, often with surface undulations or a coating of particles that promote mechanical interlock with
concreteconcrete.
3.2.3 effective bar diameter, n—a geometric value representing the diameter of a circle which has an enclosed area equal to the
nominal cross-sectional area of a bar or the measured cross-sectional area of a bar, as appropriate.
3.2.4 grid, n—a two-dimensional (planar) or three-dimensional (spatial) rigid array of interconnected FRP bars that form a
contiguous lattice that can be used to reinforce concrete. The lattice can be manufactured with integrally connected bars or
constructed of mechanically connected individual bars. The grid bar elements have transverse dimensions typically greater than
3 mm [0.125 in.].
3.2.5 effective diameter, measured cross-sectional area, n—a geometric value representing the diameter of a circle which has an
enclosed area equal to the nominal cross-sectional area of a bar.cross-sectional area of a bar, including any bond enhancing surface
treatments such as deformations, lugs, and sand coating, determined over at least one representative length, measured according
to 11.2.4.1.
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.
D7205/D7205M − 21
3.2.6 nominal cross-sectional area, n—a measure of the cross-sectional area of a bar, determined over at least one representative
length, used to calculate stress.standard FRP concrete reinforcing bar as originally developed for glass FRP bars in Specification
D7957/D7957M.
3.2.7 nominal value, n—a value, existing in name only, assigned to a measurable property for the purpose of convenient
designation. Tolerances may be applied to a nominal value to define an acceptable range for the property.
3.2.8 representative length, n—the minimum length of a bar that contains a repeating geometric pattern that, placed end-to-end,
reproduces the geometric pattern of a continuous bar (usually used in reference to bars having surface undulations for enhancing
interlock with concrete).
3.2.8 standard cross-sectional area, n—the cross-sectional area of a standard numbered steel concrete reinforcing bar as given in
ASTM A615/A615M, Table 1.
3.2.9 surface undulation, n—variation in the area, orientation, or shape of cross-section cross section of a bar along its length,
intended to enhance mechanical interlock between a bar and concrete, made by any of a number of processes such as, for example,
indentation, addition of extra materials, and twisting.
3.3 Symbols:
A = nominal cross-sectional area of a bar.
A = cross-sectional area of a bar.
CV = sample coefficient of variation, in percent.
d = effective bar diameter
d = effective diameter of a bar.
E = chord modulus of elasticity in the test direction.
chord
E = modulus of elasticity in the test direction.
F = ultimate tensile strength.
tu
K = total number of stress-strain data points used in the modulus calculation.
L = free length of specimen (length between anchors).
L = anchor length.
a
L = extensometer gage length.
g
n = number of specimens.
P = force carried by specimen.
P = maximum load carried by a test coupon before failure.
max
P = maximum force carried by a test coupon before failure.
max
r = coefficient of determination.
S = sample standard deviation.
n–1
s = sample standard deviation.
n–1
x = measured or derived property.
i
x¯ = sample mean (average).
δ = extensional displacement.
ε = indicated normal strain from strain transducer.
σ = normal stress.
4. Summary of Test Method
4.1 A fiber reinforced polymer (FRP) bar, preferably fitted with anchors, is mounted in a mechanical testing machine and
monotonically loaded in tension to failure while recording force, longitudinal strain, and longitudinal displacement.
4.2 Anchors as described in Annex A1Appendix X1 are recommended but not required. Alternative methods for attaching the
specimens to the testing machine are acceptable, but must allow for the full strength of the bar to be developed and for the failure
of the specimens to occur away from the attachments.
5. Significance and Use
5.1 This test method is designed to produce longitudinal tensile strength and elongation data. From a tension test, a variety of data
D7205/D7205M − 21
are acquired that are needed for design purposes. Material-related factors that influence the tensile response of bars and should
therefore be reported include the following: constituent materials, void content, volume percent reinforcement, methods of
fabrication, and fiber reinforcement architecture. Similarly, test factors Test factors relevant to the measured tensile response of bars
include specimen preparation, specimen conditioning, environment of testing, specimen alignment and gripping, and speed of
testing. Properties, in the test direction, that may be obtained from this test method include:
5.1.1 Maximum tensile force,
5.1.2 Ultimate tensile strength,
5.1.3 Ultimate tensile strain,
5.1.4 Tensile chord modulus of elasticity, and
5.1.5 Stress-strain curve.
6. Interferences
6.1 The results from the procedures presented are limited to the material and test factors listed in Section 5.
6.2 Gripping—The method of gripping has been known to cause premature tensile failures in bars. Anchors, if used, should be
designed in such a way that the full tensile capacity can be achieved without slip throughout the length of the anchor during the
test.
6.3 System Alignment—Excessive bending may cause premature failure, as well as a highly inaccurate modulus of elasticity
determination. Every effort should be made to eliminate bending from the test system. Bending may occur due to misalignment
of the bar within anchors or grips or associated fixturing, or from the specimen itself if improperly installed in the grips or if it
is out-of-tolerance due to poor specimen preparation. See ASTMPractice E1012 for verification of specimen alignment under
tensile loading.
6.4 Measurement of Cross-Sectional Area—The nominalmeasured cross-sectional area of the bar is measureddetermined by
immersing a prescribed length of the specimen in water to determine its buoyant weight. Bar configurations that trap air during
immersion (aside from minor porosity) cannot be assessed using this method. This method may not be appropriate for bars that
have large variations in cross-sectional area along the length of the bar.
6.5 Material-Related Factors—Material-related factors such as constituent materials, void volume content, reinforcement volume
content, methods of fabrication, and fiber reinforcement architecture can affect the tensile properties of bars.
7. Apparatus
7.1 Micrometers—The micrometer(s) shall use a suitable size diameter ball-interface on irregular surfaces and a flat anvil interface
on machined edges or very-smooth tooled surfaces. The accuracy of the instruments shall be suitable for reading to within 1 %
of the intended measurement.
7.2 Testing Machine—The testing machine shall be in conformance with PracticePractices E4, and shall satisfy the following
requirements:
7.2.1 Testing Machine Heads—The testing machine shall have both an essentially stationary head and a movable head.
7.2.2 Drive Mechanism—The testing machine drive mechanism shall be capable of imparting to the movable head a controlled
displacement rate with respect to the stationary head. The displacement rate of the movable head shall be capable of being
regulated as specified in 11.3.
7.2.3 Force Indicator—The testing machine force-sensing device shall be capable of indicating the total force being carried by the
specimen. This device shall be essentially free from inertia-lag at the specified rate of testing and shall indicate the force with an
accuracy over the load range(s) of interest of within 6 1 % of the indicated value, as specified by Practices E4. The force range(s)
of interest may be fairly low for modulus evaluation, much higher for strength evaluation, or both, as required.
D7205/D7205M − 21
NOTE 2—Obtaining precision force data over a large range of interest in the same test, such as when both elastic modulus and ultimate force are being
determined, place extreme requirements on the force transducer and its calibration. For some equipment, a special calibration may be required. For some
combinations of material and force transducer, simultaneous precision measurement of both elastic modulus and ultimate strength may not be possible,
and measurement of modulus and strength may have to be performed in separate tests using a different force transducer range for each test.
7.2.4 Grips—If grips are used, each head of the testing machine shall carry one grip for holding the specimen so that the loading
direction is coincident with the longitudinal axis of the specimen. The grips shall apply sufficient lateral pressure to prevent
slippage between the grip face and the specimen or anchor. It is highly desirable to use grips that are rotationally self-aligning to
minimize bending stresses in the specimen. The grips shall be aligned in accordance with ASTMPractice E1012 and shall not bias
failure location in the bar.
7.3 Anchors—Use of a rigid pipe-shaped anchor as an interface between the bar and the grips or loading head of the testing
machine is recommended to prevent stress concentrations and consequent downward biasing of measured strength. Details of
recommended anchors Suggestions for a grouted anchor are provided in Annex A1Appendix X1.
7.3.1 Attachment of anchors to loading heads shall be by threaded connectors between the anchors and loading head or by grips.
Details of this attachment are shown in Fig. X1.3Fig. A1.3. .
7.4 Strain-Indicating Device—Longitudinal strain shall be measured by an appropriate strain transducer as long as attachment of
this device does not cause damage to the bar (see Note 3).
NOTE 3—For most bars, the application of surface-bonded strain gages is impractical due to surface undulations (for example, braided, twisted, and
indented bars). Strain gages of a suitable gage length can be used if the surface of the bar can be smoothed with a polymer resin such as epoxy to provide
a suitable bonding surface so that measurements are equivalent to those provided by an extensometer meeting the requirements of section 7.4.1.
7.4.1 Extensometers—Extensometers shall satisfy, at a minimum, Practice E83, Class B-2 requirements for the strain range of
interest, and shall be calibrated over that strain range in accordance with Practice E83. The extensometer shall be essentially free
of inertia-lag at the specified speed of testing. The gage length of the extensometer, L , shall be not less than eight times the
g
effective bar diameter, nor less than one representative length. The extensometer shall be centered on the mid-length position of
the bar, not less than eight effective bar diameters from either anchoranchor.
7.4.1.1 Temperature compensation is recommended when not testing at Standard Laboratory Atmosphere. When appropriate, use
either (a)(a) a traveler specimen (dummy specimen) with identical bar material and extensometer(s) or (b)(b) an extensometer
calibrated for temperature changes.
7.5 Environmental Test Chamber—An environmental chamber is required for conditioning and test environments other than
ambient laboratory conditions. These chambers shall be capable of maintaining the required relative temperature to within 63°C
[65°F]63 °C [65 °F] and the required relative humidity level to within 65 %RH. In addition, the chambers may have to be
capable of maintaining environmental conditions such as fluid exposure or relative humidity during the conditioning and testing
(see SectionsSection 10 and 11.4).
8. Sampling and Test Specimens
8.1 Sampling—Test at least five specimens per test condition unless valid results can be gained through the use of fewer specimens,
such as in the case of a designed experiment. For statistically significant data, the procedures outlined in Practice E122 should be
consulted. The method of sampling shall be reported.
8.2 Geometry:
8.2.1 Overall Specimen Length and Gage Length—The total length of the specimen shall be the free length plus two times the
anchor length, L . The free length between the anchors, L, shall be not less than 380 mm [15 in.] 380 mm [15 in.] nor less than
a
40 times the effective bar diameter for bars with effective diameter of 26 mm [1.02 in.] or less. For bars with an effective diameter
larger than 26 mm [1.02 in.], the free length shall not be less than 20 times the effective bar diameter. The length of the specimen
in the grips and anchors (if used) shall be sufficient for adequate anchorage.
D7205/D7205M − 21
8.2.2 Labeling—The specimens shall be labeled so that they will be distinct from each other and traceable back to the raw material,
and in a manner that will both be unaffected by the test and not influence the test.
9. Calibration
9.1 The accuracy of all measuring equipment shall have certified calibrations that are current at the time of use of the equipment.
10. Conditioning
10.1 Standard Conditioning Procedure—Condition per Procedure C of If not otherwise specified, the recommended pre-test
condition is effective moisture equilibrium at a specific relative humidity as established by Test Method D5229/D5229M; store at
Standard Laboratory Atmosphere (2363° C [7365° F] and 50610 % RH) unless a different conditioning environment is specified
as part of the experiment.however, if the test requestor does not explicitly specify a pre-test conditioning environment, no
conditioning is required and the specimens may be tested as prepared.
NOTE 4—If tensile specimens are to undergo environmental conditioning to equilibrium, and are of such type or geometry that the weight change of the
material cannot be properly measured by weighing the specimen itself (such as a bar with anchors), then a traveler specimen of the same cross-section
geometry and appropriate size (but without anchors) shall be used to determine whenThe term “moisture,” as used in Test Method D5229/
D5229Mequilibrium has been reached for the specimens being conditioned. The ends of tensile specimens and traveler specimens shall be sealed with
a water resistant sealant such as a high grade, room-temperature curing epoxy to avoid end effects during conditioning., includes not only the vapor of
a liquid and its condensate, but the liquid itself in large quantities, as for immersion.
10.2 The pre-test specimen conditioning process, to include specified environmental exposure levels shall be reported with the test
data.
10.3 If no explicit conditioning process is performed, the specimen conditioning process shall be reported as unconditioned and
the moisture content as unknown.
NOTE 5—If tensile specimens are to undergo environmental conditioning to equilibrium, and are of such type or geometry that the weight change of the
material cannot be properly measured by weighing the specimen itself (such as a bar with anchors), then a traveler specimen of the same cross-section
geometry and appropriate size (but without anchors) shall be used to determine when equilibrium has been reached for the specimens being conditioned.
The ends of tensile specimens and traveler specimens shall be sealed with a water resistant sealant such as a high grade, room-temperature curing epoxy
to avoid end effects during conditioning.
11. Procedure
11.1 Parameters to be specified prior to test:
11.1.1 The specimen sampling method, specimen type and geometry, conditioning, and if required, traveler specimen geometry.
11.1.2 The tensile properties and data reporting format desired.
NOTE 6—Determine specific material property, accuracy, and data reporting requirements before test for proper selection of instrumentation and
data-recording equipment. Estimate operating stress and strain levels to aid in transducer selection, calibration of equipment, and determination of
equipment settings.
11.1.3 The environmental conditioning test parameters and sealant used for the ends of the specimens.
11.1.4 If performed, the sampling method, specimen geometry, and test methods used to determine density, void fraction, and
reinforcement volume.
11.2 General Instructions:
11.2.1 Report any deviations from this test method, whether intentional or inadvertent.
11.2.2 If specific gravity, density, reinforcement volume or void volume are to be reported, use ASTM D792 (specific gravity,
density) and ASTM D3171 (reinforcement volume, void volume) for the determination of these properties and select specimens
from the same batch of bar as that used for the tensile and traveler specimens.
D7205/D7205M − 21
11.2.2 Condition the specimens (specify either before or after attachment of anchors), as required. If test conditions are to be
different from ambient laboratory conditions, it is recommended that anchors be applied before conditioning. Condition the traveler
coupons if they are to be used.
11.2.3 Following final specimen machining and any conditioning, but before the tension testing, measure and report the free length
of specimen.
11.2.4 Bar areaArea and diameter—Diameter—Either the nominal measured cross-sectional area or the standardnominal
cross-sectional area as givendescribed in ASTMSpecification A615/A615MD7957/D7957M is used to calculate stress and
modulus of elasticity. elasticity for any type of FRP bar. In either case, the nominalmeasured cross-sectional area must be
measuredcalculated and reported. If the nominalmeasured cross-sectional area differs from the standard cross-sectional area for the
given baris not within minimum and maximum area limits provided in Specification D7957/D7957Msize by more than 20 percent,
standard , the nominal cross-sectional area may not be used.
11.2.4.1 Nominal cross-sectional area—Measured Cross-sectional Area—The nominalmeasured area is calculated as the average
of 5 representative specimens cut from the same bar stock as that used for the tensile test. Conditioning of the cross-sectional area
specimens is the same as that for the bars used for the tensile test. The volume of each specimen shall be measured indirectly by
the difference in mass of the specimen in the dry and fully immersed states (refer to ASTM Test Methods D792 for test methods).
The volume of the specimen is the mass of the specimen divided by the density as measured by ASTM Test Methods D792.
Nominal The measured area is then found by dividing volume by the average length of the specimen. The average length of a
typical bar specimen (e.g., (for example, circular or polygonal cross-section) cross section) is found by measuring the length of
the outer edge of the specimen three times at the outer edge, rotating the specimen by 120 degrees for each measurement. Record
2 2
the area in units of mm [in. ]. Effective bar diameter, d, is found by Eq 1equation (1)::
d 5 2=~A/3.1416! (1)
NOTE 7—The use of effective bar diameter may not be appropriate for bars that are not solid and not substantially round in cross section.
NOTE 8—For a representative determination of area, specimens of at least 100 mm [4 in.] or one representative length (whichever is greater) shall be used.
The mass of a specimen may exceed the limit imposed by ASTM Test Methods D792 (50 grams) for large diameter bars, but the procedure may still be
used.
11.2.4.2 Standard cross-sectional area—Nominal Cross-sectional Area—The standardnominal cross-sectional area is the
conventionally acceptedfor FRP bars is described in Specification D7957/D7957Marea of a steel bar with the same number
designation as a FRP bar being tested.
NOTE 9—Standard cross-sectional areas are taken as the cross-sectional areas of steel reinforcing bars as given in ASTM A615/A615M. FRP bars are often
manufactured as substitutions for steel reinforcing bars, and are typically numbered using the same designations as steel bars, for example, a No. 4 bar
2 2
has an effective diameter of 13 mm [0.5 in.] and a standard cross-sectional area of 129 mm [0.20 in. ]. For some applications, it is considered appropriate
to use the standardnominal area for calculating stress and modulus of elasticity in FRP bars, as this is the practice for steel bars. glass FRP bars. While
Specification D7957/D7957M was developed for glass FRP bars, the nominal cross-sectional areas in the specification are considered suitable for any
composite bar.
11.2.5 Apply extensometers or strain gages to the specimen.
11.3 Speed of Testing—The speed of testing shall be set to effect a nearly constant strain or stress rate in the gage section. The
strain speed of testing rate shall be selected so as to produce failure within 1 to 10 minutes from the beginning of force application.
If the ultimate strain of the material cannot be reasonably estimated, conduct initial trials using standard speeds until the ultimate
strain of the material and the compliance of the system are known, and the strain rate can be adjusted. The suggested standard strain
-1 -1
rate is 0.01 min. . If strain control is not available on the testing machine, a nominal cross-head speed of 0.01 min. times the
specimen free length selected according to Section 8.2.1 shall be used.
-1
11.3.1 The suggested standard strain rate is 0.01 min. If strain control is not available on the testing machine, a nominal
-1
cross-head speed of 0.01 min. times the specimen free length selected according to 8.2.1 can be used.
11.3.2 The suggested standard stress rate is 300 MPa/min. [44 ksi/min.].
11.3.3 If the ultimate strength and strain of the material cannot be reasonably estimated, conduct initial trials using standard speeds
until failure is produced in 1 to 10 minutes from the beginning of force application.
D7205/D7205M − 21
11.4 Test Environment—Test at Standard Laboratory Atmosphere (2363° C [7365° F] (2363 °C [7365 °F] and 50610 % RH)
unless a different environment is specified as part of the experiment. Recommendations for testing at other than standard laboratory
conditions are given in Annex A2A1.
11.5 Specimen Insertion
11.5.1 If grips are used, place the specimen in the grips of the testing machine, taking care to align the longitudinal axis of the
gripped specimen with the test direction. Tighten the grips, recording the pressure used on pressure controllable (hydraulic or
pneumatic) grips.
11.5.2 If the anchor is attached to the loading head by threading or clevis, attach the specimen to the loading heads and removed
any excess slack from the test fixture.
11.6 Testing—Apply extension to the specimen at the specified rate until failure occurs, while recording data.
11.7 Data Recording—Record force versus strain (or transducer displacement) continuously, or at frequent regular intervals; for
this test method, a minimum sampling rate of 2 to 3 data recordings per second, and a target minimum of 100 data points per test
are second is recommended. If the specimen is to be failed, record the maximum force, the failure force, and the strain (or
transducer displacement) at, or as near as possible to, the moment of rupture.
NOTE 10—Other valuable data that can be useful in understanding testing anomalies and gripping or specimen slipping problems includes force versus
head displacement data and force versus time data.
11.8 Failure Modes—Record the mode and the location of failure of the specimen.
12. Validation
12.1 Values for ultimate properties shall not be calculated for any specimen that fails at some obvious flaw, unless such a flaw
constitutes a variable being studied. Retests shall be performed for any specimen on which values are not calculated.
12.2 Re-examine the means of force introduction into the material if a significant fraction of failures in a sample population occur
within or just outside any anchor or grip. Factors considered should include the anchor-to-test frame alignment, anchor material,
anchor-to-specimen alignment, anchor filler and bonding agent, grip type, grip pressure, and grip alignment.
13. Calculation
13.1 Tensile Stress/Tensile Strength—Calculate the ultimate tensile strength using Eq 2and report the results to three significant
figures. If the tensile modulus is to be calculated, determine the tensile stress at each required data point using Eq 3.
F 5 P /A (2)
tu max
σ 5 P /A (3)
i i
where:
F = Ultimate tensile strength, MPa [psi],
tu
P = Maximum force prior to failure, N [lbf],
max
σ = Tensile stress at i-th data point, MPa [psi]
i
σ = Tensile stress at i-th data point, MPa [psi],
i
P = Force at i-th data point, N [lbf], and
i
P = Force at i-th data point, N [lbf], and
i
2 2
A = Cross-sectional area of the bar from 11.2.5, mm [in. ].
2 2
A = Cross-sectional area of the bar from 11.2.4, mm [in. ].
13.2 Tensile Strain/Ultimate Tensile Strain—If tensile modulus or ultimate tensile strain is to be calculated, and material response
is bei
...