Standard Test Method for Flexural Strength of Manufactured Carbon and Graphite Articles Using Four-Point Loading at Room Temperature

ABSTRACT
This test method details the standard procedures for determining the flexural strength of manufactured carbon and graphite articles using a simple beam in four-point loading at room temperature. The four-point loading fixture shall consist of spherical bearing blocks of hardened steel or its equivalent to ensure that forces applied to the beam are normal only and without eccentricity, and distortion of the loading member is prevented. Judicious use of linkages, rocker bearings, and flexure plates may maintain the parallel direction of loads and reactions. The test specimens shall be prepared to yield a parallelepiped with cross sections that are rectangular, faces that are parallel and flat, and edges that are free from visible flaws and chips.
SCOPE
1.1 This test method covers determination of the flexural strength of manufactured carbon and graphite articles using a simple beam in four-point loading at room temperature.  
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
1.3 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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Publication Date
30-Apr-2010
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ASTM C651-91(2010)e1 - Standard Test Method for Flexural Strength of Manufactured Carbon and Graphite Articles Using Four-Point Loading at Room Temperature
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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
An American National Standard
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Designation:C651–91 (Reapproved 2010)
Standard Test Method for
Flexural Strength of Manufactured Carbon and Graphite
Articles Using Four-Point Loading at Room Temperature
This standard is issued under the fixed designation C651; 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.
This standard has been approved for use by agencies of the Department of Defense.
´ NOTE—Updated 9.1.10 and Fig. 1 editorially in May 2010.
1. Scope 3.2 Definitions of Terms Specific to This Standard:
3.2.1 flexural strength—a measure of the ultimate load-
1.1 This test method covers determination of the flexural
carrying capacity of a specified beam in bending.
strength of manufactured carbon and graphite articles using a
simple beam in four-point loading at room temperature.
4. Apparatus
1.2 The values stated in inch-pound units are to be regarded
4.1 The testing machine shall conform to the requirements
as standard. The values given in parentheses are mathematical
of Practices E4.
conversions to SI units that are provided for information only
4.2 The four-point loading fixture shall consist of bearing
and are not considered standard.
blocks which ensure that forces applied to the beam are normal
1.3 This standard does not purport to address all of the
only and without eccentricity. (See Test Method C78.)
safety concerns, if any, associated with its use. It is the
4.2.1 The bearing block diameter shall be between 1/10 and
responsibility of the user of this standard to establish appro-
1/20 of the specimen support span. A hardened steel bearing
priate safety and health practices and determine the applica-
block or its equivalent is necessary to prevent distortion of the
bility of regulatory limitations prior to use.
loading member.
2. Referenced Documents 4.3 The directions of loads and reactions may be maintained
parallel by judicious use of linkages, rocker bearings, and
2.1 ASTM Standards:
flexure plates. Eccentricity of loading can be avoided by the
C78 Test Method for Flexural Strength of Concrete (Using
use of spherical bearings. Provision must be made in fixture
Simple Beam with Third-Point Loading)
design for relief of torsional loading to less than 5 % of the
C709 Terminology Relating to Manufactured Carbon and
nominal specimen strength. Refer to the attached figure for a
Graphite
suggested four-point loading fixture.
E4 Practices for Force Verification of Testing Machines
E177 Practice for Use of the Terms Precision and Bias in
5. Test Specimen
ASTM Test Methods
5.1 Preparation—The test specimen shall be prepared to
E691 Practice for Conducting an Interlaboratory Study to
yield a parallelepiped of rectangular cross section. The faces
Determine the Precision of a Test Method
shall be parallel and flat within 0.001 in. (0.025 mm)/in. of
3. Terminology length. In addition, the samples having a maximum particle
size less than 0.006-in. (0.152-mm) diameter must be finished
3.1 Definitions—For definitions of terms relating to manu-
so that the surface roughness is less than 125 µin.AA. Sample
factured carbon and graphite, see Terminology C709.
edges should be free from visible flaws and chips.
5.2 Size—The size of the test specimen shall be selected
This test method is under the jurisdiction of ASTM Committee D02 on
such that the minimum dimension of the specimen is greater
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
than 5 times the largest particle dimension. The test specimen
D02.F0 on Manufactured Carbon and Graphite Products.
shall have a length to thickness ratio of at least 8, and a width
Current edition approved May 1, 2010. Published December 2010. Originally
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approved in 1970. Last previous edition approved in 2005 as C651–91(2005) .
to thickness ratio not greater than 2.
DOI:10.1520/C0651–91R10E01.
5.3 Measurements—All dimensions shall be measured to
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
the nearest 0.5 %.
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
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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C651–91 (2010)
5.4 Orientation—The specimen shall be marked on the end 7. Test Data Record
to denote its orientation with respect to the parent stock.
7.1 Measurements to 0.001 in. (0.025 mm) shall be made to
5.5 Drying—Each specimen must be dried in a vented oven
determine the average width and thickness of the specimen at
at 120 to 150°C for a period of 2 h. The sample must then be
the section of failure.
cooled to room temperature in a desiccator and held there prior
7.2 The load at failure must be recor
...

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