ASTM D7264/D7264M-06
(Test Method)Standard Test Method for Flexural Properties of Polymer Matrix Composite Materials
Standard Test Method for Flexural Properties of Polymer Matrix Composite Materials
SCOPE
1.1 This test method determines the flexural stiffness and strength properties of polymer matrix composites.
1.1.1 Procedure AA three-point loading system utilizing center loading on a simply supported beam.
1.1.2 Procedure BA four-point loading system utilizing two load points equally spaced from their adjacent support points, with a distance between load points of one-half of the support span.Note 1
Unlike Test Method D 6272, which allows loading at both one-third and one-half of the support span, in order to standardize geometry and simplify calculations this standard permits loading at only one-half the support span.
1.2 For comparison purposes, tests may be conducted according to either test procedure, provided that the same procedure is used for all tests, since the two procedures generally give slightly different property values.
1.3 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.
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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D 7264/D 7264M – 06
Standard Test Method for
Flexural Properties of Polymer Matrix Composite Materials
This standard is issued under the fixed designation D 7264/D 7264M; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 3878 Terminology for Composite Materials
D 5229/D 5229M Test Method for Moisture Absorption
1.1 This test method determines the flexural stiffness and
Properties and Equilibrium Conditioning of Polymer Ma-
strength properties of polymer matrix composites.
trix Composite Materials
1.1.1 Procedure A—A three-point loading system utilizing
D 5687/D 5687M Guide for Preparation of Flat Composite
center loading on a simply supported beam.
Panels with Processing Guidelines for Specimen Prepara-
1.1.2 Procedure B—A four-point loading system utilizing
tion
two load points equally spaced from their adjacent support
D 6272 Test Method for Flexural Properties of Unrein-
points, with a distance between load points of one-half of the
forced and Reinforced Plastics and Electrical Insulating
support span.
Materials by Four-Point Bending
NOTE 1—Unlike Test Method D 6272, which allows loading at both
D 6856 Guide for Testing Fabric-Reinforced “Textile”
one-third and one-half of the support span, in order to standardize
Composite Materials
geometry and simplify calculations this standard permits loading at only
E4 Practices for Force Verification of Testing Machines
one-half the support span.
E6 Terminology Relating to Methods of Mechanical Test-
1.2 For comparison purposes, tests may be conducted ac-
ing
cording to either test procedure, provided that the same
E18 Test Methods for Rockwell Hardness and Rockwell
procedure is used for all tests, since the two procedures
Superficial Hardness of Metallic Materials
generally give slightly different property values.
E 122 Practice for Calculating Sample Size to Estimate,
1.3 The values stated in either SI units or inch-pound units
With a Specified Tolerable Error, the Average for a
are to be regarded separately as standard. Within the text, the
Characteristic of a Lot or Process
inch-pound units are shown in brackets. The values stated in
E 177 Practice for Use of the Terms Precision and Bias in
each system are not exact equivalents; therefore, each system
ASTM Test Methods
must be used independently of the other. Combining values
E 456 Terminology Relating to Quality and Statistics
from the two systems may result in nonconformance with the
E 1309 Guide for Identification of Fiber-Reinforced
standard.
Polymer-Matrix Composite Materials in Databases
1.4 This standard does not purport to address all of the
E 1434 GuideforRecordingMechanicalTestDataofFiber-
safety concerns, if any, associated with its use. It is the
Reinforced Composite Materials in Databases
responsibility of the user of this standard to establish appro-
2.2 Other Documents:
priate safety and health practices and determine the applica-
ANSI Y14.5-1999 Dimensioning and Tolerancing—
bility of regulatory limitations prior to use.
Includes Inch and Metric
ANSI B46.1-1995 Surface Texture (Surface Roughness,
2. Referenced Documents
Waviness and Lay)
2.1 ASTM Standards:
D 790 TestMethodsforFlexuralPropertiesofUnreinforced
3. Terminology
and Reinforced Plastics and Electrical Insulating Materials
3.1 Definitions—Terminology D 3878 defines the terms re-
D 2344/D 2344M Test Method for Short-Beam Strength of
lating to high-modulus fibers and their composites. Terminol-
Polymer Matrix Composite Materials andTheir Laminates
ogy E6 defines terms relating to mechanical testing. Termi-
nology E 456 and Practice E 177 define terms relating to
statistics.Intheeventofaconflictbetweenterms,Terminology
This test method is under the jurisdiction of ASTM Committee D30 on
D 3878 shall have precedence over the other documents.
Composite Materials and is the direct responsibility of Subcommittee D30.04 on
Lamina and Laminate Test Methods. 3.2 Definitions of Terms Specific to This Standard:
Current edition approved Nov. 1, 2006. Published December 2006.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
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D 7264/D 7264M – 06
3.2.1 flexural strength, n—the maximum stress at the outer
surface of a flexure test specimen corresponding to the peak
applied force prior to flexural failure.
3.2.2 flexural modulus, n—the ratio of stress range to
corresponding strain range for a test specimen loaded in
flexure.
3.3 Symbols:
b = specimen width
CV = sample coefficient of variation, in percent
chord FIG. 2 Procedure B—Loading Diagram
E = flexural chord modulus of elasticity
f
secant
E = flexural secant modulus of elasticity
f
h = specimen thickness
three-point and four-point configurations is the presence of
L = support span
resultant vertical shear force in the three-point configuration
m = slope of the secant of the load-deflection curve
everywhere in the beam except right under the mid-point force
n = number of specimens
application member whereas in the four-point configuration,
P = applied force
the area between the central force application members has no
s = sample standard deviation
n-1
resultant vertical shear force. The distance between the outer
x = measured or derived property
i
support members is the same as in the equivalent three-point
x = sample mean
configuration.
d = mid-span deflection of the specimen
4.4 The test geometry is chosen to limit out-of-plane shear
e = strain at the outer surface at mid-span of the specimen
deformations and avoid the type of short beam failure modes
s = stress at the outer surface at mid-span of the specimen
that are interrogated in Test Method D 2344/D 2344M.
4. Summary of Test Method
5. Significance and Use
4.1 Abar of rectangular cross section, supported as a beam,
5.1 This test method determines the flexural properties
is deflected at a constant rate as follows:
(including strength, stiffness, and load/deflection behavior) of
4.1.1 Procedure A—The bar rests on two supports and is
polymer matrix composite materials under the conditions
loaded by means of a loading nose midway between the
defined. Procedure A is used for three-point loading and
supports (see Fig. 1).
Procedure B is used for four-point loading. This test method
4.1.2 Procedure B—The bar rests on two supports and is
was developed for optimum use with continuous-fiber-
loaded at two points (by means of two loading noses), each an
reinforced polymer matrix composites and differs in several
equal distance from the adjacent support point. The distance
respects from other flexure methods, including the use of a
between the loading noses (that is, the load span) is one-half of
standard span-to-thickness ratio of 32:1 versus the 16:1 ratio
the support span (see Fig. 2).
used by Test Methods D 790 (a plastics-focused method
4.2 Force applied to the specimen and resulting specimen
covering three-point flexure) and D 6272 (a plastics-focused
deflection at the center of span are measured and recorded until
method covering four-point flexure).
the failure occurs on either one of the outer surfaces, or the
5.2 This test method is intended to interrogate long-beam
deformation reaches some pre-determined value.
strength in contrast to the short-beam strength evaluated by
4.3 The major difference between four-point and three-point
Test Method D 2344/D 2344M.
loading configurations is the location of maximum bending
5.3 Flexural properties determined by these procedures can
moment and maximum flexural stress. With the four-point
be used for quality control and specification purposes, and may
configuration the bending moment is constant between the
find design applications.
central force application members. Consequently, the maxi-
5.4 These procedures can be useful in the evaluation of
mum flexural stress is uniform between the central force
multiple environmental conditions to determine which are
application members. In the three-point configuration, the
design drivers and may require further testing.
maximum flexural stress is located directly under the center
5.5 Theseproceduresmayalsobeusedtodetermineflexural
force application member. Another difference between the
properties of structures.
6. Interferences
6.1 Flexural properties may vary depending on which sur-
face of the specimen is in compression, as no laminate is
perfectly symmetric (even when full symmetry is intended);
such differences will shift the neutral axis and will be further
affected by even modest asymmetry in the laminate. Flexural
properties may also vary with specimen thickness, condition-
ing and/or testing environments, and rate of straining. When
evaluating several datasets these parameters should be equiva-
FIG. 1 Procedure A—Loading Diagram lent for all data in the comparison.
D 7264/D 7264M – 06
6.2 For multidirectional laminates with a small or moderate uniform contact can affect flexural properties by initiating
number of laminae, flexural modulus and flexural strength may damage by crushing and by non-uniformly loading the beam.
be affected by the ply-stacking sequence and will not neces- Formulas used in this standard assume a uniform line loading
sarily correlate with extensional modulus, which is not at the specimen supports across the entire specimen width;
stacking-sequence dependent. deviations from this type of loading is beyond the scope of this
6.3 The calculation of the flexural properties in Section 13 standard.
of this standard is based on beam theory, while the specimens
7. Apparatus
in general may be described as plates. The differences may in
some cases be significant, particularly for laminates containing 7.1 Testing Machine—Properly calibrated, which can be
a large number of plies in the 645° direction. The deviations operated at a constant rate of crosshead motion, and in which
from beam theory decrease with decreasing width. the error in the force application system shall not exceed 61%
6.4 Loading noses may be fixed, rotatable or rolling. Typi- of the full scale. The force indicating mechanism shall be
cally, for testing composites, fixed or rotatable loading noses essentially free of inertia lag at the crosshead rate used. Inertia
are used. The type of loading nose can affect results, since lag shall not exceed 1 % of the measured force. The accuracy
non-rolling paired supports on either the tension or compres- of the testing machine shall be verified in accordance with
sion side of the specimen introduce slight longitudinal forces PracticesE4.
and resisting moments on the beam, which superpose with the 7.2 Loading Noses and Supports—The loading noses and
intended loading.The type of supports used is to be reported as supports shall have cylindrical contact surfaces of radius 3.00
described in Section 14. The loading noses should also mm [0.125 in.] as shown in Fig. 3, with a hardness of 60 to 62
uniformly contact the specimen across its width. Lack of HRC, as specified in Test MethodsE18, and shall have finely
FIG. 3 Example Loading Nose and Supports for Procedures A (top) and B (bottom)
D 7264/D 7264M – 06
ground surfaces free of indentation and burrs with all sharp within 63°C [65°F] and the required vapor level to within
edgesrelieved.Loadingnosesandsupportsmaybearrangedin 65 % relative humidity.
a fixed, rotatable or rolling arrangement. Typically, with
composites, rotatable or fixed arrangements are used. 8. Test Specimens
7.3 Micrometers—For width and thickness measurements
8.1 Specimen Preparation—Guide D 5687/D 5687M pro-
the micrometers shall usea4to7mm [0.16 to 0.28 in.]
vides recommended specimen preparation practices and should
nominal diameter ball-interface on an irregular surface such as
be followed when practical.
the bag side of a laminate, and a flat anvil interface on
8.2 Specimen Size is chosen such that the flexural properties
machined edges or very smooth tooled surfaces.Amicrometer
are determined accurately from the tests. For flexural strength,
or caliper with flat anvil faces shall be used to measure the
the standard support span-to-thickness ratio is chosen such that
length of the specimen.The accuracy of the instrument(s) shall
failure occurs at the outer surface of the specimens, due only to
be suitable for reading to within 1 % or better of the specimen
the bending moment (see Notes 2 and 3). The standard
dimensions. For typical section geometries, an instrument with
span-to-thicknessratiois32:1,thestandardspecimenthickness
an accuracy of 60.02 mm [60.001 in.] is desirable for
is 4 mm [0.16 in.], and the standard specimen width is 13 mm
thickness and width measurement, while an instrument with an
[0.5 in.] with the specimen length being about 20 % longer
accuracy of 60.1 mm [60.004 in.] is adequate for length
than the support span. See Figs. 4 and 5 for a drawing of the
measurement.
standardtestspecimeninSIandinch-poundunits,respectively.
7.4 Deflection Measurement—Specimen deflection at the
For fabric-reinforced textile composite materials, the width of
common center of the loading span shall be measured by a
thespecimenshallbeatleasttwounitcells,asdefinedinGuide
properly calibrated device having an accuracy of 61% or
D 6856. If the standard specimen thickness cannot be obtained
better of the expected maximum displacement. The device
in a given material system, an alternate specimen thickness
shall automatically and continuously record the deflection
shall be used while maintaining the support span-to-thickness
during the test.
ratio [32:1] and specimen width. Optional support span-to-
7.5 Conditioning Chamber—When conditioning materials
thickness ratios of 16:1, 20:1, 40:1, and 60:1 may also be used
at non-laboratory environments, a temperature/vapor-level
provided it is so noted in the report. Also, the data obtained
controlledenvironmentalconditioningchamberisrequiredthat
from a test using one support span-to-thickness ratio may not
shall be capable of maintaining the required temperature to
be compared with the data from another test using a different
within 61°C [62°F] and the required vapor level to within
support span-to
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