Standard Test Method for Flatwise Compressive Properties of Sandwich Cores

SCOPE
1.1 This test method covers the determination of the compressive strength and modulus of sandwich cores. These properties are usually determined for design purposes, in a direction normal to the plane of facings as the core would be placed in a structural sandwich construction. The test procedures pertain to compression in this direction in particular, but also can be applied with possible minor variations to determining compressive properties in other directions.  
1.2 The values stated in SI units are to be regarded as the standard. The inch-pound units given may be approximate.  
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
09-Mar-2000
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ASTM C365-00 - Standard Test Method for Flatwise Compressive Properties of Sandwich Cores
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: C 365 – 00
Standard Test Method for
Flatwise Compressive Properties of Sandwich Cores
This standard is issued under the fixed designation C 365; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope be verified in accordance with Practices E 4.
4.2 Spherical Bearing Block, preferably of the suspended,
1.1 This test method covers the determination of the com-
self-aligning type.
pressive strength and modulus of sandwich cores. These
4.3 Deflectometer or Compressometer, capable of measur-
properties are usually determined for design purposes in a
ing the displacement with a precision of at least 61 %. Bonded
direction normal to the plane of facings as the core would be
resistance strain gages are not usually considered satisfactory
placed in a structural sandwich construction. The test proce-
because of their stiffness. The reinforcing effect of bonding
dures pertain to compression in this direction in particular, but
these gages to some cores leads to large errors in measurement
also can be applied with possible minor variations to determin-
of strains. Also, using the test machines cross-head travel
ing compressive properties in other directions.
reading is not satisfactory as large modulus errors can result. A
1.2 The values stated in SI units are to be regarded as the
transducer and rod setup as shown in Fig. 1 and Fig. 2 have
standard. The inch-pound units given may be approximate.
been found to work satisfactorily. Here a small hole is drilled
1.3 This standard does not purport to address all of the
in the center of the specimen and in the bottom loading platen,
safety concerns, if any, associated with its use. It is the
and a transducer rod is inserted that contacts the upper loading
responsibility of the user of this standard to establish appro-
platen.
priate safety and health practices and determine the applica-
4.4 Micrometer, Gage, or Caliper, capable of measuring
bility of regulatory limitations prior to use.
accurately to 0.025 mm (0.001 in.).
2. Referenced Documents
5. Test Specimens
2.1 ASTM Standards:
2 5.1 Test specimens shall be of core or of sandwich construc-
E 4 Practices for Force Verification of Testing Machines
tion and shall be of square or circular cross section having
2 2
3. Significance and Use areas not exceeding 400 mm (16 in. ), but not less than the
following minimum areas for various types of cores:
3.1 The flatwise compressive strength and modulus are
5.1.1 For continuous cores, such as balsa wood and foams,
fundamental mechanical properties of sandwich cores that are
2 2
the minimum cross-sectional area shall be 625 mm (1 in. ).
used in designing sandwich panels. Deformation data can be
5.1.2 For open-celled cores, such as honeycomb, having
obtained, and from a complete load-deformation curve it is
cells less than 6 mm ( ⁄2 in.) the minimum cross-sectional area
possible to compute the compressive stress at any load (such as
2 2
shall be 2580 mm (4 in. ) and for cells 6 mm ( ⁄2 in.) or greater
compressive stress at proportional limit load or compressive
2 2
the minimum cross-sectional area shall be 5800 mm (9 in. ).
strength at maximum load) and to compute the effective
5.2 The height of the specimen shall be as agreed upon by
modulus of the core.
the purchaser and the seller.
3.2 This test method provides a standard method of obtain-
5.3 The number of test specimens and the method of their
ing the flatwise compressive strength and modulus for sand-
selection depend on the purpose of the particular test under
wich panel design and research and development.
consideration, and no general rule can be given to cover all
4. Apparatus
cases. However, when specimens are to be used for acceptance
tests, not less than five specimens of a type shall be tested.
4.1 Testing Machine, capable of maintaining a controlled
5.4 Prepare the test specimens so that the loaded ends will
loading rate and indicating the load with an accuracy of 61%
be parallel to each other and perpendicular to the sides of the
of the indicated value. The accuracy of the test machine shall
specimen. To avoid local crushing at the ends of some
honeycomb cores, it is desirable to reinforce the ends with a
This specification is under the jurisdiction of ASTM Committee D-30 on
suitable material. The ends may be dipped in a thin layer of
Composite Materials and is the direct responsibility of Subcommittee D30.09 on
resin or thin facings bonded to the core. When either of these
Sandwich Construction.
Current edition approved March 10, 2000. Published April 2000. Originally
methods are used the test is called a stabilized compression
published as C 365 – 55T. Last previous edition C 365 – 94.
test. When the honeycomb cell edges are not stabilized, the test
Annual Book of AS
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