ASTM D6272-02(2008)e1
(Test Method)Standard Test Method for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials by Four-Point Bending
Standard Test Method for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials by Four-Point Bending
SIGNIFICANCE AND USE
Flexural properties determined by this test method are especially useful for quality control and specification purposes.
This test method may be more suited for those materials that do not fail within the strain limits imposed by Test Method D 790. The major difference between four point and three point bending modes is the location of the maximum bending moment and maximum axial fiber stress. In four point bending the maximum axial fiber stress is uniformly distributed between the loading noses. In three point bending the maximum axial fiber stress is located immediately under the loading nose.
Flexural properties may vary with specimen depth, temperature, atmospheric conditions, and the difference in rate of straining specified in Procedures A and B.
Before proceeding with this test method, reference should be made to the specification of the material being tested. Any test specimen preparation, conditioning, dimensions, or testing parameters covered in the material specification, or both, shall take precedence over those mentioned in this test method. If there are no material specifications, then these default conditions apply. Table 1 in Classification D 4000 lists the ASTM materials standards that currently exist.
SCOPE
1.1 This test method covers the determination of flexural properties of unreinforced and reinforced plastics, including high-modulus composites and electrical insulating materials in the form of rectangular bars molded directly or cut from sheets, plates, or molded shapes. These test methods are generally applicable to rigid and semirigid materials. However, flexural strength cannot be determined for those materials that do not break or that do not fail in the outer fibers. This test method utilizes a four point loading system applied to a simply supported beam.
1.2 This test method may be used with two procedures:
1.2.1 Procedure A, designed principally for materials that break at comparatively small deflections.
1.2.2 Procedure B, designed particularly for those materials that undergo large deflections during testing.
1.2.3 Procedure A shall be used for measurement of flexural properties, particularly flexural modulus, unless the material specification states otherwise. Procedure B may be used for measurement of flexural strength.
1.3 Comparative tests may be run according to either procedure, provided that the procedure is found satisfactory for the material being tested.
1.4 The values stated in SI units are to be regarded as the standard. The values provided in parentheses are for information only.
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 and health practices and determine the applicability of regulatory limitations prior to use.
Note 1—This test method is equivalent to ISO 14125 (Method B).
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´1
Designation:D6272–02 (Reapproved 2008)
Standard Test Method for
Flexural Properties of Unreinforced and Reinforced Plastics
and Electrical Insulating Materials by Four-Point Bending
This standard is issued under the fixed designation D6272; 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.
´ NOTE—Editorially changed Note 1 in April 2008.
1. Scope* 2. Referenced Documents
1.1 This test method covers the determination of flexural 2.1 ASTM Standards:
properties of unreinforced and reinforced plastics, including D618 Practice for Conditioning Plastics for Testing
high-modulus composites and electrical insulating materials in D638 Test Method for Tensile Properties of Plastics
theformofrectangularbarsmoldeddirectlyorcutfromsheets, D790 Test Methods for Flexural Properties of Unreinforced
plates, or molded shapes. These test methods are generally and Reinforced Plastics and Electrical Insulating Materials
applicable to rigid and semirigid materials. However, flexural D883 Terminology Relating to Plastics
strength cannot be determined for those materials that do not D4000 Classification System for Specifying Plastic Materi-
break or that do not fail in the outer fibers. This test method als
utilizes a four point loading system applied to a simply D4066 Classification System for Nylon Injection and Ex-
supported beam. trusion Materials (PA)
1.2 This test method may be used with two procedures: D5947 Test Methods for Physical Dimensions of Solid
1.2.1 Procedure A, designed principally for materials that Plastics Specimens
break at comparatively small deflections. E4 Practices for Force Verification of Testing Machines
1.2.2 Procedure B, designed particularly for those materials E83 Practice for Verification and Classification of Exten-
that undergo large deflections during testing. someter Systems
1.2.3 ProcedureAshall be used for measurement of flexural E691 Practice for Conducting an Interlaboratory Study to
properties, particularly flexural modulus, unless the material Determine the Precision of a Test Method
specification states otherwise. Procedure B may be used for 2.2 ISO Standard:
measurement of flexural strength. ISO 14125 (Method B)
1.3 Comparative tests may be run according to either
3. Terminology
procedure, provided that the procedure is found satisfactory for
the material being tested. 3.1 Definitions:
3.1.1 Definitions of terms applying to these test methods
1.4 The values stated in SI units are to be regarded as the
standard. The values provided in parentheses are for informa- appear in Terminology D883 and Annex A2 of Test Method
D638.
tion only.
1.5 This standard does not purport to address all of the
4. Summary of Test Method
safety concerns, if any, associated with its use. It is the
4.1 A bar of rectangular cross section rests on two supports
responsibility of the user of this standard to establish appro-
and is loaded at two points (by means of two loading noses),
priate safety and health practices and determine the applica-
each an equal distance from the adjacent support point. The
bility of regulatory limitations prior to use.
distancebetweentheloadingnoses(theloadspan)iseitherone
NOTE 1—This test method is equivalent to ISO 14125 (Method B).
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method is under the jurisdiction ofASTM Committee D20 on Plastics contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
and is the direct responsibility of Subcommittee D20.10 on Mechanical Properties. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved April 1, 2008. Published July 2008. Originally the ASTM website.
approved in 1998. Last previous edition approved in 2002 as D6272 - 02. DOI: Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/D6272-02R08E01. 4th Floor, New York, NY 10036, http://www.ansi.org.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
´1
D6272–02 (2008)
third or one half of the support span (see Fig. 1). A support default conditions apply. Table 1 in Classification D4000 lists
span-to-depth ratio of 16:1 shall be used unless there is reason the ASTM materials standards that currently exist.
to suspect that a larger span-to-depth ratio may be required, as
6. Apparatus
may be the case for certain laminated materials (see Section 7
and Note 8 for guidance). 6.1 Testing Machine—A properly calibrated testing ma-
chinethatcanbeoperatedatconstantratesofcrossheadmotion
4.2 The specimen is deflected until rupture occurs in the
outer fibers or until the maximum fiber strain (see 12.7)of5% over the range indicated, and in which the error in the load
measuring system shall not exceed 6 1 % of maximum load
is reached, whichever occurs first.
expected to be measured. It shall be equipped with a deflection
5. Significance and Use measuring device. The stiffness of the testing machine shall be
such that the total elastic deformation of the system does not
5.1 Flexural properties determined by this test method are
exceed 1 % of the total deflection of the test specimen during
especially useful for quality control and specification purposes.
testing, or appropriate corrections shall be made. The load
5.2 This test method may be more suited for those materials
indicating mechanism shall be essentially free from inertial lag
that do not fail within the strain limits imposed byTest Method
at the crosshead rate used.The accuracy of the testing machine
D790. The major difference between four point and three point
shall be verified in accordance with Practices E4.
bending modes is the location of the maximum bending
6.2 Loading Noses and Supports—The loading noses and
moment and maximum axial fiber stress. In four point bending
supports shall have cylindrical surfaces. In order to avoid
the maximum axial fiber stress is uniformly distributed be-
excessive indentation, or failure due to stress concentration
tween the loading noses. In three point bending the maximum
directly under the loading noses, the radii of the loading noses
axialfiberstressislocatedimmediatelyundertheloadingnose.
and supports shall be 5.0 6 0.1 mm (0.197 6 0.004 in.) unless
5.3 Flexural properties may vary with specimen depth,
otherwise specified or agreed upon between the interested
temperature, atmospheric conditions, and the difference in rate
parties. When other loading noses and supports are used they
of straining specified in Procedures A and B.
must comply with the following requirements: they shall be at
5.4 Before proceeding with this test method, reference
least 3.2 mm ( ⁄8 in.) for all specimens, and for specimens 3.2
shouldbemadetothespecificationofthematerialbeingtested.
mm ( ⁄8 in.) or greater in depth, the radius of the supports may
Any test specimen preparation, conditioning, dimensions, or
be up to 1.6 times the specimen depth. They shall be this large
testing parameters covered in the material specification, or
ifsignificantindentationorcompressivefailureoccurs.Thearc
both, shall take precedence over those mentioned in this test
of the loading noses in contact with the specimen shall be
method. If there are no material specifications, then these
sufficiently large to prevent contact of the specimen with the
sides of the noses (see Fig. 2).
NOTE 2—Test data have shown that the loading noses and support
dimensions can influence the flexural modulus and flexural strength
values. The loading noses dimension has the greater influence. Dimen-
sions of loading noses and supports must be specified for material
specifications.
6.3 Deflection Measuring Device—A properly calibrated
device to measure the deflection of the beam at the common
center of the loading span, that meets or exceeds Practice E83,
Class C, shall be used. The device shall automatically and
continuously record the deflection during the test.
6.4 Micrometers—Suitable micrometers for measuring the
width and thickness of the test specimen to an incremental
discrimination of at least 0.025 mm (0.001 in.) should be used.
All width and thickness measurements of rigid and semi-rigid
plastics may be measured with a hand micrometer with ratchet.
Asuitable instrument for measuring the thickness of non-rigid
NOTE 1—Default radii 5.0 mm; see 6.2.
FIG. 2 Loading Noses and Supports (Example of One Third
FIG. 1 Loading Diagram Support Span)
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D6272–02 (2008)
test specimens shall have: a contact measuring pressure of 25 7.3 Laminated Thermosetting Materials and Sheet and
6 2.5 kPa (3.6 6 0.036 psi), a movable circular contact foot Plate Materials Used for Electrical Insulation, Including
6.35 6 0,025 mm (0.250 6 0.001 in.) in diameter and a fixed
Vulcanized Fiber and Glass-Bonded Mica—For paper-base
anvil 6.35 6 0,025 mm (0.250 6 0.001 in.) in diameter and
and fabric-base grades over 25.4 mm (1 in.) in nominal
being parallel to the contact foot within 0.005 mm (0.0002 in.)
thickness, the specimens shall be machined on both surfaces to
over the entire foot area. Flatness of foot and anvil shall
a depth of 25.4 mm. For glass-base and nylon-base grades,
conform to the portion of the calibration section of Test
specimens over 12.7 mm ( ⁄2 in.) in nominal depth shall be
Method D5947.
machined on both surfaces to a depth of 12.7 mm. The support
span-to-depth ratio shall be chosen such that failures occur in
7. Test Specimen
the outer fibers of the specimens, due only to the bending
7.1 The specimens may be cut from sheets, plates, or
moment (see Note 8). Three recommended support span-to-
molded shapes, or may be molded to the desired finished
depth ratios are 16, 32, and 40 to 1. When laminated materials
dimensions. The actual dimensions used in Section 12 (Calcu-
exhibit low compressive strength perpendicular to the lamina-
lation) shall be measured in accordance with Test Method
tions,theyshallbeloadedwithalargeradiusloadingnoses(up
D5947.
to 1.5 times the specimen depth) to prevent premature damage
to the outer fibers.
NOTE 3—Any necessary polishing of specimens shall be done only in
the lengthwise direction of the specimen.
7.4 Molding Materials (Thermoplastics and Thermosets)—
The recommended specimen for molding materials is 127 by
7.2 Sheet Materials (Except Laminated Thermosetting Ma-
1 1
terials and Certain Materials Used for Electrical Insulation, 12.7 by 3.2 mm (5 by ⁄2 by ⁄8 in.) tested flatwise on a support
Including Vulcanized Fiber and Glass Bonded Mica): span, resulting in a support span-to-depth ratio of 16 (tolerance
7.2.1 Materials 1.6 mm ( ⁄16 in.) or Greater in Thickness—
+ 4 or – 2). Thicker specimens should be avoided if they
For flatwise tests, the depth of the specimen shall be the
exhibit significant shrink marks or bubbles when molded.
thickness of the material. For edgewise tests, the width of the
7.5 High-Strength Reinforced Composites, Including Highly
specimenshallbethethicknessofthesheet,andthedepthshall
Orthotropic Laminates—The support span-to-depth ratio shall
not exceed the width (see Notes 5 and 6). For all tests, the
be chosen such that failures occur in the outer fibers of the
support span shall be 16 (tolerance 6 1) times the depth of the
specimens, due only to the bending moment (Note 8). Three
beam. Specimen width shall not exceed one fourth of the
recommended support span-to-depth ratios are 16:1, 32:1, and
support span for specimens greater than 3.2 mm ( ⁄8 in.) in
40:1. However, for some highly anisotropic composites, shear
depth. Specimens 3.2 mm or less in depth shall be 12.7 mm ( ⁄2
deformation can significantly influence modulus measure-
in.) in width. The specimen shall be long enough to allow for
ments, even at span-to-depth ratios as high as 40:1. Hence, for
overhanging on each end of at least 10 % of the support span,
these materials, an increase in span-to-depth ratio to 60:1 is
but in no case less than 6.4 mm ( ⁄4 in.) on each end. Overhang
recommendedtoeliminatesheareffectswhenmodulusdataare
shall be sufficient to prevent the specimen from slipping
required. It should also be noted that the flexural modulus of
through the supports.
highly anisotropic laminates is a strong function of ply-
NOTE 4—Whenever possible, the original surface of the sheet shall be
stacking sequence and will not necessarily correlate with
unaltered. However, where testing machine limitations make it impossible
tensile modulus, that is not stacking-sequence dependent.
to follow the above criterion on the unaltered sheet, one or both surfaces
shall be machined to provide the desired dimensions, and the location of
NOTE 8—As a general rule, support span-to-depth ratios of 16 to 1 are
the specimens with reference to the total depth shall be noted. The value
satisfactory when the ratio of the tensile strength to shear strength is less
obtained on specimens with machined surfaces may differ from those
than 8 to 1, but the support span-to-depth ratio must be increased for
obtained on specimens with original surfaces. Consequently, any specifi-
composite laminates having relatively low shear strength in the plane of
cations for flexural properties on the thicker sheets must state whether the
the laminate and relatively high tensile strength parallel to the support
original surfaces are to be retained or not. When only one surface was
span.
machined, it must be stated whether the machined surface was on the
tension or compression side of the beam.
8. Number of Test Specimens
NOTE 5—Edgewise tests are not applicable for sheets that are so thin
that specimens meeting these requirements cannot be cut. If specimen
8.1 Atleastfivespecimensshallbetestedforeachsamplein
depth exceeds the width, buckling may occur.
the case of isotropic materials or molded specimens.
7.2.2 Materials Less than 1.6 m ( ⁄16 in.) in Thickness—The
8.2 For each sample of anisotropic material in sheet form, at
specimen shall be 50.8 mm (2 in.) long by 12.7 mm ( ⁄2 in.)
least five specimens shall be tested for each of the following
wide, tested flatwise on a 25.4-mm (1-in.) support span.
conditions. Recommended conditions are flatwise and edge-
NOTE 6—Use of the formulas for simple beams cited in these test wise tests on specimens cut in lengthwise and crosswise
methods for calculating results presumes that beam width is small in
directions of the sheet. For the purposes of this test, “length-
comparison with the support spa
...
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.
e1
Designation:D6272–00 Designation:D6272–02 (Reapproved 2008)
Standard Test Method for
Flexural Properties of Unreinforced and Reinforced Plastics
and Electrical Insulating Materials by Four-Point Bending
This standard is issued under the fixed designation D 6272; 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.
e NOTE—Editorially changed Note 1 in April 2008.
1. Scope*
1.1 This test method covers the determination of flexural properties of unreinforced and reinforced plastics, including
high-modulus composites and electrical insulating materials in the form of rectangular bars molded directly or cut from sheets,
plates, or molded shapes. These test methods are generally applicable to rigid and semirigid materials. However, flexural strength
cannot be determined for those materials that do not break or that do not fail in the outer fibers. This test method utilizes a four
point loading system applied to a simply supported beam.
1.2 This test method may be used with two procedures:
1.2.1 Procedure A, designed principally for materials that break at comparatively small deflections.
1.2.2 Procedure B, designed particularly for those materials that undergo large deflections during testing.
1.2.3 Procedure A shall be used for measurement of flexural properties, particularly flexural modulus, unless the material
specification states otherwise. Procedure B may be used for measurement of flexural strength.
1.3 Comparative tests may be run according to either procedure, provided that the procedure is found satisfactory for the
material being tested.
1.4 The values stated in SI units are to be regarded as the standard.The values provided in parentheses are for information only.
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 and health practices and determine the applicability of regulatory
limitations prior to use.
NOTE1—This test method is equivalent to, but not identical to ISO 14125 (Method B). 1—This test method is equivalent to ISO 14125 (Method B).
2. Referenced Documents
2.1 ASTM Standards:
D 618Practice for Conditioning Plastics and Electrical Insulating Materials for Testing Practice for Conditioning Plastics for
Testing
D 638 Test Method for Tensile Properties of Plastics
D 790 Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials
D 883 Terminology Relating to Plastics
D 4000 Classification System for Specifying Plastic Materials
D 4066 Classification System for Nylon Injection and Extrusion Materials (PA)
D 5947Methods for Physical Dimensions of Solid Plastic Specimens Test Methods for Physical Dimensions of Solid Plastics
Specimens
E 4 Practices for LoadForce Verification of Testing Machines
E 83 Practice for Verification and Classification of Extensometer Systems
E 691 Practice for Conducting an Interlaboratory Test Program Study to Determine the Precision of a Test MethodsMethod
2.2 ISO Standard:
ISO 14125 (Method B)
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.10 on Mechanical Properties.
Current edition approved July 10, 2000. Published October 2000. Originally published as D6272–98. Last previous edition D6272–98.
Current edition approved April 1, 2008. Published July 2008. Originally approved in 1998. Last previous edition approved in 2002 as D 6272 - 02.
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
, Vol 08.01.volume information, refer to the standard’s Document Summary page on the ASTM website.
Annual Book of ASTM Standards, Vol 08.02.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
e1
D6272–02 (2008)
3. Terminology
3.1 Definitions:
3.1.1 Definitions of terms applying to these test methods appear in Terminology D 883 and Annex A2 of Test Method D 638.
4. Summary of Test Method
4.1 Abar of rectangular cross section rests on two supports and is loaded at two points (by means of two loading noses), each
an equal distance from the adjacent support point. The distance between the loading noses (the load span) is either one third or
one half of the support span (see Fig. 1).Asupport span-to-depth ratio of 16:1 shall be used unless there is reason to suspect that
a larger span-to-depth ratio may be required, as may be the case for certain laminated materials (see Section 7 and Note 8 for
guidance).
4.2 The specimen is deflected until rupture occurs in the outer fibers or until the maximum fiber strain (see 12.7) of 5 % is
reached, whichever occurs first.
5. Significance and Use
5.1 Flexural properties determined by this test method are especially useful for quality control and specification purposes.
5.2 This test method may be more suited for those materials that do not fail within the strain limits imposed by Test Method
D 790. The major difference between four point and three point bending modes is the location of the maximum bending moment
and maximum axial fiber stress. In four point bending the maximum axial fiber stress is uniformly distributed between the loading
noses. In three point bending the maximum axial fiber stress is located immediately under the loading nose.
5.3 Flexural properties may vary with specimen depth, temperature, atmospheric conditions, and the difference in rate of
straining specified in Procedures A and B.
5.4 Before proceeding with this test method, reference should be made to the specification of the material being tested.Any test
specimen preparation, conditioning, dimensions, or testing parameters covered in the material specification, or both, shall take
precedence over those mentioned in this test method. If there are no material specifications, then these default conditions apply.
Table 1 in Classification D 4000 lists the ASTM materials standards that currently exist.
6. Apparatus
6.1 Testing Machine— A properly calibrated testing machine that can be operated at constant rates of crosshead motion over
the range indicated, and in which the error in the load measuring system shall not exceed 6 1 % of maximum load expected to
FIG. 1 Loading Diagram
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D6272–02 (2008)
be measured. It shall be equipped with a deflection measuring device. The stiffness of the testing machine shall be such that the
totalelasticdeformationofthesystemdoesnotexceed1 %ofthetotaldeflectionofthetestspecimenduringtesting,orappropriate
corrections shall be made. The load indicating mechanism shall be essentially free from inertial lag at the crosshead rate used. The
accuracy of the testing machine shall be verified in accordance with Practices E 4.
6.2 Loading Noses and Supports —The loading noses and supports shall have cylindrical surfaces. In order to avoid excessive
indentation, or failure due to stress concentration directly under the loading noses, the radii of the loading noses and supports shall
be 5.0 6 0.1 mm (0.197 6 0.004 in.) unless otherwise specified or agreed upon between the interested parties.When other loading
noses and supports are used they must comply with the following requirements: they shall be at least 3.2 mm ( ⁄8 in.) for all
specimens, and for specimens 3.2 mm ( ⁄8 in.) or greater in depth, the radius of the supports may be up to 1.6 times the specimen
depth. They shall be this large if significant indentation or compressive failure occurs. The arc of the loading noses in contact with
the specimen shall be sufficiently large to prevent contact of the specimen with the sides of the noses (see Fig. 2).
NOTE 2—Test data have shown that the loading noses and support dimensions can influence the flexural modulus and flexural strength values. The
loading noses dimension has the greater influence. Dimensions of loading noses and supports must be specified for material specifications.
6.3 Deflection Measuring Device —A properly calibrated device to measure the deflection of the beam at the common center
of the loading span, that meets or exceeds Practice E 83, Class C, shall be used. The device shall automatically and continuously
record the deflection during the test.
6.4 Micrometers— Suitable micrometers for measuring the width and thickness of the test specimen to an incremental
discrimination of at least 0.025 mm (0.001 in.) should be used. All width and thickness measurements of rigid and semi-rigid
plastics may be measured with a hand micrometer with ratchet.Asuitable instrument for measuring the thickness of non-rigid test
specimens shall have: a contact measuring pressure of 25 6 2.5 kPa (3.6 6 0.036 psi), a movable circular contact foot 6.35 6
0,025 mm (0.250 6 0.001 in.) in diameter and a fixed anvil 6.35 6 0,025 mm (0.250 6 0.001 in.) in diameter and being parallel
to the contact foot within 0.005 mm (0.0002 in.) over the entire foot area. Flatness of foot and anvil shall conform to the portion
of the calibration section of Test Method D 5947.
7. Test Specimen
7.1 The specimens may be cut from sheets, plates, or molded shapes, or may be molded to the desired finished dimensions.The
actual dimensions used in Section 12 (Calculation) shall be measured in accordance with Test Method D 5947.
NOTE 3—Any necessary polishing of specimens shall be done only in the lengthwise direction of the specimen.
7.2 Sheet Materials (Except Laminated Thermosetting Materials and Certain Materials Used for Electrical Insulation,
Including Vulcanized Fiber and Glass Bonded Mica):
7.2.1 Materials 1.6 mm ( ⁄16 in.) or Greater in Thickness—For flatwise tests, the depth of the specimen shall be the thickness
of the material. For edgewise tests, the width of the specimen shall be the thickness of the sheet, and the depth shall not exceed
the width (see Notes 5 and 6). For all tests, the support span shall be 16 (tolerance 6 1) times the depth of the beam. Specimen
width shall not exceed one fourth of the support span for specimens greater than 3.2 mm ( ⁄8 in.) in depth. Specimens 3.2 mm or
less in depth shall be 12.7 mm ( ⁄2 in.) in width. The specimen shall be long enough to allow for overhanging on each end of at
least 10 % of the support span, but in no case less than 6.4 mm ( ⁄4 in.) on each end. Overhang shall be sufficient to prevent the
specimen from slipping through the supports.
NOTE 4—Whenever possible, the original surface of the sheet shall be unaltered. However, where testing machine limitations make it impossible to
follow the above criterion on the unaltered sheet, one or both surfaces shall be machined to provide the desired dimensions, and the location of the
specimens with reference to the total depth shall be noted. The value obtained on specimens with machined surfaces may differ from those obtained on
specimens with original surfaces. Consequently, any specifications for flexural properties on the thicker sheets must state whether the original surfaces
are to be retained or not. When only one surface was machined, it must be stated whether the machined surface was on the tension or compression side
of the beam.
NOTE 5—Edgewise tests are not applicable for sheets that are so thin that specimens meeting these requirements cannot be cut. If specimen depth
exceeds the width, buckling may occur.
1 1
7.2.2 Materials Less than 1.6 m ( ⁄16 in.) in Thickness—The specimen shall be 50.8 mm (2 in.) long by 12.7 mm ( ⁄2 in.) wide,
tested flatwise on a 25.4-mm (1-in.) support span.
NOTE 1—Default radii 5.0 mm; see 6.2.
FIG. 2 Loading Noses and Supports (Example of One Third
Support Span)
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D6272–02 (2008)
NOTE 6—Use of the formulas for simple beams cited in these test methods for calculating results presumes that beam width is small in comparison
with the support span. Therefore, the formulas do not apply rigorously to these dimensions.
NOTE 7—Wheremachinesensitivityissuchthatspecimensofthesedimensionscannotbemeasured,widerspecimensorshortersupportspans,orboth,
may be used, provided the support span-to-depth ratio is at least 14 to 1. All dimensions must be stated in the report (see also Note 6).
7.3 Laminated Thermosetting Materials and Sheet and Plate Materials Used for Electrical Insulation, Including Vulcanized
Fiber and Glass-Bonded Mica—For paper-base and fabric-base grades over 25.4 mm (1 in.) in nominal thickness, the specimens
shall be machined on both surfaces to a depth of 25.4 mm. For glass-base and nylon-base grades, specimens over 12.7 mm ( ⁄2
in.) in nominal depth shall be machined on both surfaces to a depth of 12.7 mm. The support span-to-depth ratio shall be chosen
such that failures occur in the outer fibers of the specimens, due only to the bending moment (see Note 8). Three recommended
support span-to-depth ratios are 16, 32, and 40 to 1. When laminated materials exhibit low compressive strength perpendicular to
the laminations, they shall be loaded with a large radius loading noses (up to 1.5 times the specimen depth) to prevent premature
damage to the outer fibers.
7.4 Molding Materials (Thermoplastics and Thermosets)—The recommended specimen for molding materials is 127 by 12.7
1 1
by 3.2 mm (5 by ⁄2 by ⁄8 in.) tested flatwise on a support span, resulting in a support span-to-depth ratio of 16 (tolerance + 4 or
– 2). Thicker specimens should be avoided if they exhibit significant shrink marks or bubbles when molded.
7.5 High-Strength Reinforced Composites, Including Highly Orthotropic Laminates—The support span-to-depth ratio shall be
chosen such that failures occur in the outer fibers of the specimens, due only to the bending moment (Note 8).Three recommended
support span-to-depth ratios are 16:1, 32:1, and 40:1. However, for some highly anisotropic composites, shear deformation can
significantly influence modulus measurements, even at span-to-depth ratios as high as 40:1. Hence,
...
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