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

SIGNIFICANCE AND USE
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. 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 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 Ultimate tensile strength,
5.1.2 Ultimate tensile strain,  
5.1.3 Tensile chord modulus of elasticity, and  
5.1.4 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 D 3039/D 3039M and D 3916.
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/or a coating of bonded particles 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 are provided in .
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.
This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the inch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
1.5 This annex describes the recommended anchor to facilitate gripping of FRP bar specimens for various types of tests performed under tensile loading. It also specifies preparation of the specimens. Other types of anchors may be used provided it is demonstrated that (a) failure of the bar occurs outside the anchors and (b) the anchors prevent excessive slip of the bar prior to tensile failure.
1.6 This annex provides recommendations for testing bars in conditions that are other than standard laboratory conditions. These conditions may include immersion in water or other aqueous solution and/or elevated temperature or moisture conditions.

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D7205/D7205M–06
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 must be used independently of the other. Combining values
from the two systems may result in nonconformance with the
1.1 Thistestmethoddeterminesthequasi-staticlongitudinal
standard.
tensile strength and elongation properties of fiber reinforced
polymer matrix (FRP) composite bars commonly used as
2. Referenced Documents
tensile elements in reinforced, prestressed, or post-tensioned
2.1 ASTM Standards:
concrete.
A615/A615M Specification for Deformed and Plain
NOTE 1—Additional procedures for determining tensile properties of
Carbon-Steel Bars for Concrete Reinforcement
polymermatrixcompositesmaybefoundintestmethodsD3039/D3039M
D792 Test Methods for Density and Specific Gravity (Rela-
and D3916.
tive Density) of Plastics by Displacement
1.2 Linear elements used for reinforcing Portland cement
D883 Terminology Relating to Plastics
concrete are referred to as bars, rebar, rods, or tendons,
D3039/D3039M Test Method for Tensile Properties of
depending on the specific application. This test method is
Polymer Matrix Composite Materials
applicable to all such reinforcements within the limitations
D3171 Test Methods for Constituent Content of Composite
noted in the method. The test articles are referred to as bars in
Materials
this test method. In general, bars have solid cross-sections and
D3878 Terminology for Composite Materials
a regular pattern of surface undulations and/or a coating of
D3916 Test Method for Tensile Properties of Pultruded
bonded particles that promote mechanical interlock between
Glass-Fiber-Reinforced Plastic Rod
the bar and concrete. The test method is also appropriate for
D5229/D5229M Test Method for Moisture Absorption
use with linear segments cut from a grid. Specific details for
Properties and Equilibrium Conditioning of Polymer Ma-
preparing and testing of bars and grids are provided. In some
trix Composite Materials
cases, anchors may be necessary to prevent grip-induced
E4 Practices for Force Verification of Testing Machines
damagetotheendsofthebarorgrid.Recommendeddetailsfor
E6 TerminologyRelatingtoMethodsofMechanicalTesting
the anchors are provided in Annex A1.
E83 Practice for Verification and Classification of Exten-
1.3 The strength values provided by this method are short-
someter Systems
term static strengths that do not account for sustained static or
E122 Practice for Calculating Sample Size to Estimate,
fatigue loading. Additional material characterization may be
With Specified Precision, the Average for a Characteristic
required, especially for bars that are to be used under high
of a Lot or Process
levels of sustained or repeated loading.
E456 Terminology Relating to Quality and Statistics
1.4 This standard does not purport to address all of the
E1012 PracticeforVerificationofTestFrameandSpecimen
safety problems, if any, associated with its use. It is the
Alignment Under Tensile and Compressive Axial Force
responsibility of the user of this standard to establish appro-
Application
priate safety and health practices and determine the applica-
E1309 Guide for Identification of Fiber-Reinforced
bility of regulatory limitations prior to use.
Polymer-Matrix Composite Materials in Databases
1.5 The values stated in either SI units or inch-pound units
E1434 Guide for Recording Mechanical Test Data of Fiber-
are to be regarded separately as standard. Within the text, the
Reinforced Composite Materials in Databases
inch-pound units are shown in brackets. The values stated in
E1471 Guide for Identification of Fibers, Fillers, and Core
each system are not exact equivalents; therefore, each system
Materials in Computerized Material Property Databases
This test method is under the jurisidiction of ASTM Committee D30 on
Composite Materials and is the direct responsibility of Subcommittee D30.05 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Structural Test Methods. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved March 15, 2006. PublishedApril 2006. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
D7205_D7205M-06. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7205/D7205M–06
3. Terminology
L = anchor length.
a
L = extensometer gage length.
g
3.1 Terminology in D3878 defines terms relating to high-
n = number of specimens.
modulus fibers and their composites. Terminology in D883
P = force carried by specimen.
defines terms relating to plastics. Terminology in E6 defines
P = maximum load carried by a test coupon before
max
terms relating to mechanical testing. Terminology in E456 and
failure.
in Practice E122 define terms relating to statistics and the
S = sample standard deviation.
n–1
selection of sample sizes. In the event of a conflict between
x = measured or derived property.
i
terms, Terminology in D3878 shall have precedence over the
x¯ = sample mean (average).
other terminology standards.
d = extensional displacement.
3.2 Definitions of Terms Specific to This Standard:
´ = indicated normal strain from strain transducer.
3.2.1 anchor, n—a protective device placed on each end of
s = normal stress.
a bar, between the bar and the grips of the tensile testing
4. Summary of Test Method
machine, to prevent grip-induced damage. Usually used on
bars with irregular surfaces, as opposed to flat strips where
4.1 A fiber reinforced polymer (FRP) bar, preferably fitted
bonded tabs are more typical.
with anchors, is mounted in a mechanical testing machine and
3.2.2 bar, n—a linear element, often with surface undula-
monotonically loaded in tension to failure while recording
tions or a coating of particles that promote mechanical inter-
force, longitudinal strain, and longitudinal displacement.
lock with concrete
4.2 Anchors as described in Annex A1 are recommended
3.2.3 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
5. Significance and Use
individual bars. The grid bar elements have transverse dimen-
sions typically greater than 3 mm [0.125 in.].
5.1 This test method is designed to produce longitudinal
3.2.4 effective diameter, n—a geometric value representing
tensile strength and elongation data. From a tension test, a
the diameter of a circle which has an enclosed area equal to the
variety of data are acquired that are needed for design
nominal cross-sectional area of a bar.
purposes. Material-related factors that influence the tensile
3.2.5 nominal cross-sectional area, n—a measure of cross- response of bars and should therefore be reported include the
sectional area of a bar, determined over at least one represen- following: constituent materials, void content, volume percent
tative length, used to calculate stress. reinforcement, methods of fabrication, and fiber reinforcement
3.2.6 nominal value, n—a value, existing in name only, architecture. Similarly, test factors relevant to the measured
tensile response of bars include specimen preparation, speci-
assigned to a measurable property for the purpose of conve-
nient designation. Tolerances may be applied to a nominal men conditioning, environment of testing, specimen alignment
and gripping, and speed of testing. Properties, in the test
value to define an acceptable range for the property.
direction, that may be obtained from this test method include:
3.2.7 representative length, n—the minimum length of a bar
5.1.1 Ultimate tensile strength,
that contains a repeating geometric pattern that, placed end-to-
5.1.2 Ultimate tensile strain,
end, reproduces the geometric pattern of a continuous bar
5.1.3 Tensile chord modulus of elasticity, and
(usually used in reference to bars having surface undulations
5.1.4 Stress-strain curve.
for enhancing interlock with concrete).
3.2.8 standard cross-sectional area, n—the cross-sectional
6. Interferences
area of a standard numbered steel concrete reinforcing bar as
6.1 The results from the procedures presented are limited to
given in ASTM A615/A615M, Table 1.
the material and test factors listed in Section 5.
3.2.9 surface undulation, n—variation in the area, orienta-
6.2 Gripping—The method of gripping has been known to
tion, or shape of cross-section of a bar along its length,
cause premature tensile failures in bars. Anchors, if used,
intended to enhance mechanical interlock between a bar and
should be designed in such a way that the full tensile capacity
concrete, made by any of a number of processes such as, for
can be achieved without slip throughout the length of the
example, indentation, addition of extra materials, and twisting.
anchor during the test.
3.3 Symbols:
6.3 System Alignment—Excessive bending may cause pre-
mature failure, as well as a highly inaccurate modulus of
A = nominal cross-sectional area of a bar.
elasticity determination. Every effort should be made to elimi-
CV = sample coefficient of variation, in percent.
nate bending from the test system. Bending may occur due to
d = effective bar diameter
misalignment of the bar within anchors or grips or associated
E = chord modulus of elasticity in the test direction.
chord
fixturing, or from the specimen itself if improperly installed in
F = ultimate tensile strength.
tu
the grips or if it is out-of-tolerance due to poor specimen
L = free length of specimen (length between an-
preparation. See ASTM E1012 for verification of specimen
chors).
alignment under tensile loading.
D7205/D7205M–06
6.4 Measurement of Cross-Sectional Area—The nominal 7.3.1 Attachment of anchors to loading heads shall be by
cross-sectional area of the bar is measured by immersing a threaded connectors between the anchors and loading head or
prescribed length of the specimen in water to determine its by grips. Details of this attachment are shown in Fig. A1.3.
buoyant weight. Bar configurations that trap air during immer- 7.4 Strain-Indicating Device—Longitudinal strain shall be
sion (aside from minor porosity) cannot be assessed using this measured by an appropriate strain transducer as long as
method.This method may not be appropriate for bars that have attachmentofthisdevicedoesnotcausedamagetothebar(see
large variations in cross-sectional area along the length of the Note 3).
bar.
NOTE 3—For most bars the application of surface-bonded strain gages
is impractical due to surface undulations (for example, braided, twisted,
7. Apparatus
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
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 section
anvil interface on machined edges or very-smooth tooled
7.4.1.
surfaces. The accuracy of the instruments shall be suitable for
7.4.1 Extensometers—Extensometers shall satisfy, at a
reading to within 1 % of the intended measurement.
minimum, Practice E83, Class B-2 requirements for the strain
7.2 Testing Machine—The testing machine shall be in
range of interest, and shall be calibrated over that strain range
conformance with Practice E4, and shall satisfy the following
in accordance with Practice E83. The extensometer shall be
requirements:
essentially free of inertia-lag at the specified speed of testing.
7.2.1 Testing Machine Heads—The testing machine shall
The gage length of the extensometer, L , shall be not less than
g
have both an essentially stationary head and a movable head.
eight times the effective bar diameter, nor less than one
7.2.2 Drive Mechanism—The testing machine drive mecha-
representative length. The extensometer shall be centered on
nism shall be capable of imparting to the movable head a the mid-length position of the bar, not less than eight effective
controlled displacement rate with respect to the stationary
bar diameters from either anchor
head. The displacement rate of the movable head shall be
7.4.1.1 Temperature compensation is recommended when
capable of being regulated as specified in 11.3.
not testing at Standard Laboratory Atmosphere. When appro-
priate, use either (a) a traveler specimen (dummy specimen)
7.2.3 Force Indicator—The testing machine force-sensing
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
from inertia-lag at the specified rate of testing and shall
chamber is required for conditioning and test environments
indicate the force with an accuracy over the load range(s) of
otherthanambientlaboratoryconditions.Thesechambersshall
interest of within 6 1 % of the indicated value, as specified by
be 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
NOTE 2—Obtainingprecisionforcedataoveralargerangeofinterestin
exposure or relative humidity during the conditioning and
the same test, such as when both elastic modulus and ultimate force are
testing (see Sections 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 me
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