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 Bars1
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
1.1 This test method determines the quasi-static longitudinal brackets.
tensile strength and elongation properties of fiber reinforced 1.5 This standard does not purport to address all of the
polymer matrix (FRP) composite bars commonly used as safety concerns, if any, associated with its use. It is the
tensile elements in reinforced, prestressed, or post-tensioned responsibility of the user of this standard to establish appro-
concrete. priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
NOTE 1—Additional procedures for determining tensile properties of
polymer matrix composites may be found in Test Methods D3039/
1.6 This international standard was developed in accor-
D3039M and D3916. dance with internationally recognized principles on standard-
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
iTeh Standards
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
Barriers to Trade (TBT) Committee.

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2. Referenced Documents
this test method. In general, bars have solid cross-sections and
a regular pattern of surface undulations or a coating of bonded 2.1 ASTM Standards:2

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particles, or both, that promote mechanical interlock between D792 Test Methods for Density and Specific Gravity (Rela-
the bar and concrete. The test method is also appropriate for tive Density) of Plastics by Displacement
use with linear segments cut from a grid. Specific details for D883 Terminology Relating to Plastics
preparing and testing of bars and grids are provided. In some D3039/D3039M Test Method for Tensile Properties of Poly-
ASTM
cases, anchors may be necessary to prevent grip-induced D7205/D7205M-21
mer Matrix Composite Materials
D3878 Terminology for Composite Materials
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damage to the ends of the bar or grid. Suggestions for a grouted
type of anchor are provided in Appendix X1. D3916 Test Method for Tensile Properties of Pultruded
Glass-Fiber-Reinforced Plastic Rod
1.3 The strength values provided by this method are short- D5229/D5229M Test Method for Moisture Absorption Prop-
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
1.4 Units—The values stated in either SI units or inch- E4 Practices for Force Verification of Testing Machines
pound units are to be regarded separately as standard. The E6 Terminology Relating to Methods of Mechanical Testing
values stated in each system are not necessarily exact equiva- E83 Practice for Verification and Classification of Exten-
lents; therefore, to ensure conformance with the standard, each someter Systems
system shall be used independently of the other, and values E122 Practice for Calculating Sample Size to Estimate, With
from the two systems shall not be combined. Specified Precision, the Average for a Characteristic of a
Lot or Process
E456 Terminology Relating to Quality and Statistics
1
This test method is under the jurisidiction of ASTM Committee D30 on
Composite Materials and is the direct responsibility of Subcommittee D30.10 on
2
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 service@astm.org. 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

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 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 Ftu = ultimate tensile strength.
3.1 Terminology D3878 defines terms relating to high- K = total number of stress-strain data points used in the
modulus fibers and their composites. Terminology D883 de- modulus calculation.
fines terms relating to plastics. Terminology E6 defines terms L = free length of specimen (length between anchors).
relating to mechanical testing. Terminology E456 and Practice La = anchor length.
E122 define terms relating to statistics and the selection of Lg = extensometer gage length.
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 Pmax = maximum force carried by a test coupon before
terminology standards. failure.
3.2 Definitions of Terms Specific to This Standard: r2 = coefficient of determination.
3.2.1 anchor, n—a protective device placed on each end of sn–1 = sample standard deviation.
a bar, between the bar and the grips of the tensile testing xi = measured or derived property.
machine, to prevent grip-induced damage. Usually used on x̄ = sample mean (average).
bars with irregular surfaces, as opposed to flat strips where δ = extensional displacement.
bonded tabs are more typical. ε = indicated normal strain from strain transducer.
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—a geometric value represent- 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
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to the nominal cross-sectional area of a bar or the measured
cross-sectional area of a bar, as appropriate.
force, longitudinal strain, and longitudinal displacement.
4.2 Anchors as described in Appendix X1 are recommended
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3.2.4 grid, n—a two-dimensional (planar) or three-
dimensional (spatial) rigid array of interconnected FRP bars
but not required. Alternative methods for attaching the speci-
mens to the testing machine are acceptable, but must allow for
that form a contiguous lattice that can be used to reinforce
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concrete. The lattice can be manufactured with integrally
connected bars or constructed of mechanically connected
the full strength of the bar to be developed and for the failure
of the specimens to occur away from the attachments.
individual bars. The grid bar elements have transverse dimen- 5. Significance and Use
sions typically greater than 3 mm [0.125 in.].ASTM D7205/D7205M-21
5.1 This test method is designed to produce longitudinal
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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. Test factors relevant to the measured tensile response
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:
developed for glass FRP bars in Specification D7957/D7957M. 5.1.1 Maximum tensile force,
3.2.7 nominal value, n—a value, existing in name only, 5.1.2 Ultimate tensile strength,
assigned to a measurable property for the purpose of conve- 5.1.3 Ultimate tensile strain,
nient designation. Tolerances may be applied to a nominal 5.1.4 Tensile chord modulus of elasticity, and
value to define an acceptable range for the property. 5.1.5 Stress-strain curve.
3.2.8 representative length, n—the minimum length of a bar
that contains a repeating geometric pattern that, placed end-to- 6. Interferences
end, reproduces the geometric pattern of a continuous bar 6.1 The results from the procedures presented are limited to
(usually used in reference to bars having surface undulations the material and test factors listed in Section 5.
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

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 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 Suggestions for a grouted anchor are provided in Appendix X1.
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
bar. 7.4 Strain-Indicating Device—Longitudinal strain shall be
measured by an appropriate strain transducer as long as
6.5 Material-Related Factors—Material-related factors attachment of this device does not cause damage to the bar (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
7.1 Micrometers—The micrometer(s) shall use a suitable to provide a suitable bonding surface so that measurements are equivalent
size diameter ball-interface on irregular surfaces and a flat to those provided by an extensometer meeting the requirements of 7.4.1.
anvil interface on machined edges or very-smooth tooled 7.4.1 Extensometers—Extensometers shall satisfy, at a
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surfaces. The accuracy of the instruments shall be suitable for
reading to within 1 % of the intended measurement.
minimum, Practice E83, Class B-2 requirements for the strain
range of interest, and shall be calibrated over that strain range

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7.2 Testing Machine—The testing machine shall be in con-
formance with Practices E4, and shall satisfy the following
in accordance with Practice E83. The extensometer shall be
essentially free of inertia-lag at the specified speed of testing.

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requirements: The gage length of the extensometer, Lg, shall be not less than
7.2.1 Testing Machine Heads—The testing machine shall eight times the effective bar diameter, nor less than one
have both an essentially stationary head and a movable head. representative length. The extensometer shall be centered on
7.2.2 Drive Mechanism—The testing machine drive mecha- the mid-length position of the bar, not less than eight effective
ASTM D7205/D7205M-21
nism shall be capable of imparting to the movable head a bar diameters from either anchor.
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controlled displacement rate with respect to the stationary 7.4.1.1 Temperature compensation is recommended when
head. The displacement rate of the movable head shall be not testing at Standard Laboratory Atmosphere. When
capable of being regulated as specified in 11.3. appropriate, use either (a) a traveler specimen (dummy speci-
7.2.3 Force Indicator—The testing machine force-sensing men) with identical bar material and extensometer(s) or (b) an
device shall be capable of indicating the total force being extensometer calibrated for temperature changes.
carried by the specimen. This device shall be essentially free 7.5 Environmental Test Chamber—An environmental cham-
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
for modulus evaluation, much higher for strength evaluation, or to within 65 %RH. In addition, the chambers may have to be
both, as required. capable of maintaining environmental conditions such as fluid
NOTE 2—Obtaining precision force data over a large range of interest in exposure or relative humidity during the conditioning and
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.
For some combinations of material and force transducer, simultaneous
8. Sampling and Test Specimens
precision measurement of both elastic modulus and ultimate strength may 8.1 Sampling—Test at least five specimens per test condi-
not be possible, and measurement of modulus and strength may have to be
performed in separate tests using a different force transducer range for
tion unless valid results can be gained through the use of fewer
each test. specimens, such as in the case of a designed experiment. For
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
the specimen. The grips shall apply sufficient lateral pressure to 8.2 Geometry:

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 D7205/D7205M − 21
8.2.1 Overall Specimen Length and Gage Length—The total 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, La. The free length between the anchors, L, 11.2 General Instructions:
shall be not less than 380 mm [15 in.] nor less than 40 times the
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
will be distinct from each other and traceable back to the raw 11.2.3 Following final specimen machining and any
material, and in a manner that will both be unaffected by the conditioning, but before the tension testing, measure and report
test and not influence the test. the free length of specimen.
11.2.4 Bar Area and Diameter—Either the measured cross-
9. Calibration sectional area or the nominal cross-sectional area as described
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
10.1 If not otherwise specified, the recommended pre-test used.
condition is effective moisture equilibrium at a specific relative 11.2.4.1 Measured Cross-sectional Area—The measured
humidity as established by Test Method D5229/D5229M; area is calculated as the average of 5 representative specimens

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however, if the test requestor does not explicitly specify a
pre-test conditioning environment, no conditioning is required
cut from the same bar stock as that used for the tensile test.
Conditioning of the cross-sectional area specimens is the same
and the specimens may be tested as prepared. as that for the bars used for the tensile test. The volume of each
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NOTE 4—The term “moisture,” as used in Test Method D5229/
D5229M, includes not only the vapor of a liquid and its condensate, but
specimen shall be measured indirectly by the difference in
mass of the specimen in the dry and fully immersed states

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the liquid itself in large quantities, as for immersion.
10.2 The pre-test specimen conditioning process, to include
(refer to Test Methods D792 for test methods). The volume of
the specimen is the mass of the specimen divided by the
specified environmental exposure levels shall be reported with density as measured by Test Methods D792. The measured area
is then found by dividing volume by the average length of the
the test data. ASTM D7205/D7205M-21
specimen. The average length of a typical bar specimen (for
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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- for each measurement. Record the area in units of mm2 [in.2].
ing to equilibrium, and are of such type or geometry that the weight
change of the material cannot be properly measured by weighing the Effective bar diameter, d, is found by Eq 1:
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) shall be used to determine when equilibrium has been reached for 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
geometry. NOTE 9—For some applications, it is considered appropriate to use the
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
to aid in transducer selection, calibration of equipment, and determination 11.3 Speed of Testing—The speed of testing shall be set to
of equipment settings. effect a nearly constant strain or stress rate in the gage section.

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 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
11.3.1 The suggested standard strain rate is 0.01 min.-1 If significant figures. If the tensile modulus is to be calculated,
strain control is not available on the testing machine, a nominal determine the tensile stress at each required data point using Eq
cross-head speed of 0.01 min.-1 times the specimen free length 3.
selected according to 8.2.1 can be used.
F tu 5 P max/A (2)
11.3.2 The suggested standard stress rate is 300 MPa/min.
[44 ksi/min.]. σ i 5 P i /A (3)
11.3.3 If the ultimate strength and strain of the material where:
cannot be reasonably estimated, conduct initial trials using Ftu = Ultimate tensile strength, MPa [psi],
standard speeds until failure is produced in 1 to 10 minutes Pmax = Maximum force prior to failure, N [lbf],
from the beginning of force application. σi = Tensile stress at i-th data point, MPa [psi],
11.4 Test Environment—Test at Standard Laboratory Atmo- Pi = Force at i-th data point, N [lbf], and
A = Cross-sectional area of the bar from 11.2.4, mm2
sphere (2363 °C [7365 °F] and 50610 % RH) unless a
[in.2].
different environment is specified as part of the experiment.
Recommendations for testing at other than standard laboratory 13.2 Tensile Strain/Ultimate Tensile Strain—If tensile
conditions are given in Annex A1. modulus or ultimate tensile strain is to be calculated, and
material response is being determined by an extensometer,
11.5 Specimen Insertion determine the tensile strain from the indicated displacement at
11.5.1 If grips are used, place the specimen in the grips of each required data point using Eq 4 and report the results to
the testing machine, taking care to align the longitudinal axis of three significant figures.
the gripped specimen with the test direction. Tighten the grips,
ε i 5 δ i /L g (4)
recording the pressure used on pressure controllable (hydraulic
or pneumatic) grips.
iTeh Standards
where:
11.5.2 If the anchor is attached to the loading head by ε = tensile strain at i-th data point, mm/mm [in./in.],
i
threading or clevis, attach the specimen to the loading heads δ = extensometer displacement at i-th data point, mm [in.],
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i
and removed any excess slack from the test fixture. and
L = extensometer gage length, mm [in.].
g
11.6 Testing—Apply extension to the specimen at the speci-
Document
fied rate until failure occurs, while recording data.
11.7 Data Recording—Record force versus strain (or trans-
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13.3 Tensile Modulus of Elasticity:
13.3.1 Tensile Modulus of Elasticity by the Method of Least
Squares—Calculate the tensile modulus of elasticity, E, and the
ducer displacement) at frequent regular intervals; for this test coefficient of determination, r2, by fitting a straight line to the
method, a minimum sampling rate of 2 data ASTM D7205/D7205M-21
recordings per data using the method of linear least squares regression
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second is recommended. If the specimen is to be failed, record analysis (Annex A2). The strain range selected for fitting the
the maximum force, the failure force, and the strain (or line is to be within the lower half of the stress-strain curve,
transducer displacement) at, or as near as possible to, the with the start point being a strain of 0.001 and the end point
moment of rupture. being a strain of 0.006. For materials that fail at a strain below
NOTE 10—Other valuable data that can be useful in understanding 0.012, the end point shall be 50 % of ultimate strain. If data are
testing anomalies and gripping or specimen slipping problems includes not available at the exact strain range start and end points (as
force versus head displacement data and force versus time data. often occurs with digital data), use the closest available data
11.8 Failure Modes—Record the mode and the location of point. Report E to three significant figures and r2 to four
failure of the specimen. significant figures. The value of r2 can be used as a diagnostic
aid to determine how well the straight line fits the stress-strain
12. Validation data. At best, the value of r2 is exactly 1. Values of r2 less than
approximately 0.995 call for a visual examination of the
12.1 Values for ultimate properties shall not be calculated quality of fit to determine whether the stress-strain data should
for any specimen that fails at some obvious flaw, unless such a be represented by a straight line. Possible reasons for low
flaw constitutes a variable being studied. Retests shall be coefficients of determination include nonlinearity and sudden
performed for any specimen on which values are not calcu- jumps in the numerical stress-strain data. If a jump occurs
lated. within the recommended strain range, then a more suitable
12.2 Re-examine the means of force introduction into the strain range shall be used and reported.
material if a significant fraction of failures in a sample 13.4 Statistics—For each series of tests, calculate the aver-
population occur within or just outside any anchor or grip. age value, standard deviation, and coefficient of variation (in
Factors considered should include the anchor-to-test frame percent) for each property determined:
alignment, anchor material, anchor-to-specimen alignment, n
x̄ 5 ~ Σ i51 x i ! /n (5)
anchor filler and bonding agent, grip type, grip pressure, and
grip alignment. s n21 5 =~ Σ i51
n
x i2 2 nx̄ 2 ! / ~ n 2 1 ! (6)

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 D7205/D7205M − 21
CV 5 100 3 s n21 /x̄ (7) 14.1.14 Results of system alignment evaluations, if any
such evaluations were done.
where:
14.1.15 Dimensions of each test specimen.
x̄ = sample mean (average), 14.1.16 Conditioning parameters (environments,
sn-1 = sample standard deviation,
temperatures, relative humidities, durations) if other than that
CV = sample coefficient of variation, in percent,
n = number of tested specimens, and specified in the test method.
xi = measured or derived property. 14.1.17 Relative humidity and temperature of the testing
laboratory.
14. Report 14.1.18 Environment of the test machine environmental
14.1 Report the following information, or references point- chamber (if used).
ing to other documentation containing this information, to the 14.1.19 Number of specimens tested.
maximum extent applicable (reporting of items beyond the 14.1.20 Speed of testing.
control of a given testing laboratory, such as might occur with 14.1.21 Transducer placement on the specimen and trans-
material details or bar fabrication parameters, shall be the ducer type for each transducer used.
responsibility of the requestor). 14.1.22 Type of area used for stress-strain curve calculation:
14.1.1 The revision level or date of issue of this test method. measured area or nominal area.
14.1.2 The date(s) and location(s) of the test. 14.1.23 Stress-strain curves and tabulated data of stress
14.1.3 The name(s) of the test operator(s). versus strain for each specimen.
14.1.4 Any variations to this test method, anomalies noticed 14.1.24 Maximum force prior to failure and ultimate tensile
during testing or equipment problems occurring during testing. strength values for each specimen, average values, standard
14.1.5 Identification of the material tested including (if deviations, and coefficients of variation (in percent) for the
available): material specification, material type, material sample. Note if the failure force was less than the maximum
designation, manufacturer, manufacturer’s lot or batch number, force prior to failure.
source (if not from manufacturer), date of certification, expi- 14.1.25 Individual strains at failure and the average value,
standard deviation, and coefficient of variation (in percent) for
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ration of certification, filament diameter, tow or yarn filament
count and twist, sizing, form or weave, and matrix type. the sample.
14.1.6 If available, description of the fabrication steps used 14.1.26 If another definition of modulus of elasticity is used

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to prepare the bar including fabrication start date, fabrication
end date, process specification, cure cycle, consolidation
in addition to modulus of elasticity by least squares, describe
the method used, the resulting coefficient of determination (if

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method, and a description of the equipment used. applicable), and the strain range used for the evaluation.
14.1.7 Description of fiber architecture and surface charac- 14.1.27 Individual values of modulus of elasticity and
teristics of the bar. Indicate the representative length of the bar, coefficient of determination, and the average value, standard
if appropriate. deviation, and coefficient of variation (in percent) for the
ASTM
14.1.8 Minimum, maximum, and average value of the D7205/D7205M-21
sample.
14.1.28 Failure mode and location of failure for each
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measured area of the bar and the average effective bar
diameter. specimen.
14.1.9 Definition of cross-sectional area used in stress
calculations: measured area or nominal area. 15. Precision and Bias
14.1.10 Results of any nondestructive evaluation tests. 15.1 Precision—The data required for the development of a
14.1.11 Method of preparing the test specimen, including precision statement is not available for this test method.
specimen labeling scheme and method, specimen geometry Precision, defined as the degree of mutual agreement between
(including free length, L), sampling method, and bar cutting individual measurements, cannot yet be estimated because of
method. Identification of anchor material, geometry, bonding an insufficient amount of data.
agent such as expansive cementitious material, and bonding
agent preparation and curing information. 15.2 Bias—Bias cannot be determined for this test method
14.1.12 Calibration dates and methods for all measurement as no acceptable reference standard exists.
and test equipment.
14.1.13 Type of test machine, grips, jaws, grip pressure, grip 16. Keywords
length and texture of grip faces, and data acquisition sampling 16.1 bars; composite bars; composite materials; tensile
rate and equipment type. modulus of elasticity; tensile properties; tensile strength

6
 D7205/D7205M − 21
ANNEXES

(Mandatory Information)

A1. RECOMMENDED PROCEDURES FOR TESTING BARS AT OTHER THAN STANDARD LABORATORY CONDITIONS

A1.1 Scope In addition, fixtures may be preheated, temperature may be

A1.1.1 This annex provides recommendations for testing ramped up quickly, and hold time at temperature may be
bars in conditions that are other than standard laboratory minimized prior to testing. Environmentally conditioned trav-
conditions. These conditions may include immersion in water eler specimens, consisting of a bare bar with a length equal to
or other aqueous solution or elevated temperature or moisture one or more representative lengths with the cut ends protected
conditions, or both. from moisture transmission with a high grade moisture resis-
tant resin, may be used to measure moisture loss during
A1.2 Conditioning exposure to the test environment. Weigh a traveler specimen
A1.2.1 Condition the specimen in the desired environment. prior to testing and place it in the test chamber at the same time
Store the specimen in the conditioned environment until test as the specimen. Remove the traveler specimen immediately
time, if the testing environment is different than the condition- after fracture and reweigh it to determine moisture loss. Record
ing environment. modifications to the test environment.
A1.3.3 Monitor test temperature by placing an appropriate
A1.3 Test Environment thermocouple within 25 mm [1.0 in.] of the gage section of the
A1.3.1 Test under the specified exposure condition (for specimen. Maintain temperature of the specimen and the
example, temperature, relative humidity, fluid exposure). traveler bar if one is being used for thermal strain compensa-
A1.3.2 Testing at Elevated Moisture Levels—Cases such as tion or moisture loss evaluation, within 63 °C [65 °F] of the
elevated temperature testing of a moist specimen may be required condition. Taping thermocouple(s) to the test speci-
iTeh Standards
beyond the capabilities of common testing machine environ-
mental chambers. In such cases, testing at elevated temperature
men (and the traveler) is an effective measurement method.
A1.3.4 Required Dimensions of Environmental Exposure

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with no fluid exposure control may be necessary, and moisture
loss during mechanical testing may occur. This loss can be
Chamber—Common testing machine environmental chambers
are unlikely to be of sufficient size to hold the entire specimen

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minimized by reducing exposure time in the test chamber; at the specified test conditions. Non-uniform thermal and
although care should be taken to ensure that the specimen moisture profiles can be minimized by reducing exposure time
temperature is at equilibrium. This loss may be further mini- in the test chamber. Report the dimensions of the environmen-
mized by increasing the relative humidity in an uncontrolled tal exposure chamber. Record the location of specimen failures
chamber by hanging wet, coarse fabric inside ASTM D7205/D7205M-21
the chamber, and and report the location of these failures relative to the position
keeping it moist with a drip bottle placed outside the chamber. of the environmental chamber on the specimen.
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A2. LINEAR LEAST SQUARES REGRESSION ANALYSIS

A2.1 Scope However, the equations used by the software should be verified
A2.1.1 This annex provides the method of calculation of the and the equations defined herein are to be utilized in the event
tensile modulus of elasticity, E, and the coefficient of of any differences.
determination, r2, in 13.3 using the method of linear least A2.2.2 Calculate the tensile modulus of elasticity, E, using
squares regression analysis. A linear least squares regression Eq A2.1:
analysis minimizes the sum of the squared residuals, where a
K
residual is defined as the difference between the fitted line and Σ i51 ~ ε i σ i ! 2 nσ̄ε̄
E5 K (A2.1)
the actual stress data point at each strain data point. The Σ i51 ε i2 2 nε̄ 2
coefficient of determination of the fit, r2, indicates the goodness where:
of fit achieved in a single test. K = total number of stress-strain data pairs used in the
A2.2 Calculation modulus calculation,
ɛ̄ = 1 Σ K ε , the average of the strain points used in the
A2.2.1 The equations that follow are standard expressions K i51 i
and should correspond to those used in commercially available modulus calculation, and
software packages that fit a linear equation to a set of data.