ASTM C365/C365M-05
(Test Method)Standard Test Method for Flatwise Compressive Properties of Sandwich Cores
Standard Test Method for Flatwise Compressive Properties of Sandwich Cores
SIGNIFICANCE AND USE
Flatwise compressive strength and modulus are fundamental mechanical properties of sandwich cores that are used in designing sandwich panels. Deformation data can be obtained, and from a complete force versus deformation curve, it is possible to compute the compressive stress at any applied force (such as compressive stress at proportional limit force or compressive strength at the maximum force) and to compute the effective modulus of the core.
This test method provides a standard method of obtaining the flatwise compressive strength and modulus for sandwich core structural design properties, material specifications, research and development applications, and quality assurance.
In order to prevent local crushing at the edges of some honeycomb cores, it is often desirable to stabilize the edges with a suitable material, such as a thin layer of resin or thin facings. Flatwise compressive strength data may be generated using either stabilized specimens (reported as stabilized compression strength) or non-stabilized specimens (reported as bare compression strength). It is customary aerospace industry practice to determine compression modulus only when using stabilized specimens.
Factors that influence the flatwise compressive strength and shall therefore be reported include the following: core material, methods of material fabrication, core geometry (cell size), core density, specimen geometry, specimen preparation, specimen conditioning, environment of testing, specimen alignment, loading procedure, and speed of testing.
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.
General Information
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Standards Content (Sample)
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Designation:C365/C365M–05
Standard Test Method for
1
Flatwise Compressive Properties of Sandwich Cores
This standard is issued under the fixed designation C365/C365M; 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.
1. Scope D5229/D5229M Test Method for Moisture Absorption
Properties and Equilibrium Conditioning of Polymer Ma-
1.1 This test method covers the determination of compres-
trix Composite Materials
sive strength and modulus of sandwich cores. These properties
E4 Practices for Force Verification of Testing Machines
are usually determined for design purposes in a direction
E6 TerminologyRelatingtoMethodsofMechanicalTesting
normal to the plane of facings as the core would be placed in
E122 Practice for Calculating Sample Size to Estimate,
a structural sandwich construction. The test procedures pertain
With Specified Precision, the Average for a Characteristic
to compression in this direction in particular, but also can be
of a Lot or Process
appliedwithpossibleminorvariationstodeterminingcompres-
E177 Practice for Use of the Terms Precision and Bias in
sive properties in other directions. Permissible core material
ASTM Test Methods
forms include those with continuous bonding surfaces (such as
E456 Terminology Relating to Quality and Statistics
balsa wood and foams) as well as those with discontinuous
E1309 Guide for Identification of Fiber-Reinforced
bonding surfaces (such as honeycomb).
Polymer-Matrix Composite Materials in Databases
1.2 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
must be used independently of the other. Combining values
from the two systems may result in nonconformance with the
3. Terminology
standard.
3.1 Definitions—Terminology D3878 defines terms relating
1.3 This standard does not purport to address all of the
to high-modulus fibers and their composites. Terminology
safety concerns, if any, associated with its use. It is the
C274 defines terms relating to structural sandwich construc-
responsibility of the user of this standard to establish appro-
tions. Terminology D883 defines terms relating to plastics.
priate safety and health practices and determine the applica-
Terminology E6 defines terms relating to mechanical testing.
bility of regulatory limitations prior to use.
Terminology E456 and Practice E177 define terms relating to
2. Referenced Documents statistics.Intheeventofaconflictbetweenterms,Terminology
2
D3878 shall have precedence over the other terminologies.
2.1 ASTM Standards:
3.2 Symbols:
C271/C271M Test Method for Density of Sandwich Core
A = cross-sectional area of a test specimen
Materials
CV = coefficient of variation statistic of a sample population
C274 Terminology of Structural Sandwich Constructions
for a given property (in percent)
D883 Terminology Relating to Plastics
fc
E = flatwise compressive modulus
z
D3878 Terminology for Composite Materials
fcu
F = ultimate flatwise compressive strength
z
fc0.02
F = flatwise compressive strength at 2 % LVDT/
z
1
This test method is under the jurisdiction of ASTM Committee D30 on
compressometer deflection
Composite Materials and is the direct responsibility of Subcommittee D30.09 on
P = maximum force carried by test specimen before
max
Sandwich Construction.
failure
Current edition approved Oct. 1, 2005. Published October 2005. Originally
P = force carried by test specimen at 2 % LVDT/
approved in 1955. Last previous edition approved in 2003 as C365 – 03. DOI:
0.02
10.1520/C0365_C0365M-05.
compressometer deflection
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
S = standard deviation statistic of a sample population for
n–1
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
a given property
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. t = thickness of a test specimen
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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C365/C365M–05
x = test result for an individual specimen from the sample 6.3 Geometry—Specific geom
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