ASTM C364/C364M-07(2012)
(Test Method)Standard Test Method for Edgewise Compressive Strength of Sandwich Constructions
Standard Test Method for Edgewise Compressive Strength of Sandwich Constructions
SIGNIFICANCE AND USE
The edgewise compressive strength of short sandwich construction specimens provides a basis for judging the load-carrying capacity of the construction in terms of developed facing stress.
This test method provides a standard method of obtaining sandwich edgewise compressive strengths for panel design properties, material specifications, research and development applications, and quality assurance.
The reporting section requires items that tend to influence edgewise compressive strength to be reported; these include materials, fabrication method, facesheet lay-up orientation (if composite), core orientation, results of any nondestructive inspections, specimen preparation, test equipment details, specimen dimensions and associated measurement accuracy, environmental conditions, speed of testing, failure mode, and failure location.
SCOPE
1.1 This test method covers the compressive properties of structural sandwich construction in a direction parallel to the sandwich facing plane. Permissible core material forms include those with continuous bonding surfaces (such as balsa wood and foams) as well as those with discontinuous bonding surfaces (such as honeycomb).
1.2 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.
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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Standards Content (Sample)
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Designation: C364/C364M − 07(Reapproved 2012)
Standard Test Method for
Edgewise Compressive Strength of Sandwich
Constructions
This standard is issued under the fixed designation C364/C364M; 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.
1. Scope erties and Equilibrium Conditioning of Polymer Matrix
Composite Materials
1.1 This test method covers the compressive properties of
D5687/D5687M Guide for Preparation of Flat Composite
structural sandwich construction in a direction parallel to the
Panels with Processing Guidelines for Specimen Prepara-
sandwichfacingplane.Permissiblecorematerialformsinclude
tion
those with continuous bonding surfaces (such as balsa wood
E4 Practices for Force Verification of Testing Machines
and foams) as well as those with discontinuous bonding
E6 Terminology Relating to Methods of Mechanical Testing
surfaces (such as honeycomb).
E122 Practice for Calculating Sample Size to Estimate,With
1.2 The values stated in either SI units or inch-pound units
Specified Precision, the Average for a Characteristic of a
are to be regarded separately as standard. Within the text the
Lot or Process
inch-pound units are shown in brackets. The values stated in
E177 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
E456 Terminology Relating to Quality and Statistics
from the two systems may result in nonconformance with the
E1012 Practice for Verification of Testing Frame and Speci-
standard.
men Alignment Under Tensile and Compressive Axial
1.3 This standard does not purport to address all of the Force Application
safety concerns, if any, associated with its use. It is the
E1309 Guide for Identification of Fiber-Reinforced
responsibility of the user of this standard to establish appro- Polymer-Matrix Composite Materials in Databases
priate safety and health practices and determine the applica-
E1434 Guide for Recording Mechanical Test Data of Fiber-
bility of regulatory limitations prior to use. Reinforced Composite Materials in Databases
E1471 Guide for Identification of Fibers, Fillers, and Core
2. Referenced Documents
Materials in Computerized Material Property Databases
2.1 ASTM Standards:
3. Terminology
C274 Terminology of Structural Sandwich Constructions
D792 Test Methods for Density and Specific Gravity (Rela-
3.1 Definitions—Terminology D3878 defines terms relating
tive Density) of Plastics by Displacement
to high-modulus fibers and their composites. Terminology
D883 Terminology Relating to Plastics
C274 defines terms relating to structural sandwich construc-
D2584 Test Method for Ignition Loss of Cured Reinforced
tions. Terminology D883 defines terms relating to plastics.
Resins
Terminology E6 defines terms relating to mechanical testing.
D2734 TestMethodsforVoidContentofReinforcedPlastics
Terminolgoy E456 and Practice E177 define terms relating to
D3039/D3039M Test Method for Tensile Properties of Poly-
statistics.Intheeventofaconflictbetweenterms,Terminology
mer Matrix Composite Materials
D3878 shall have precedence over the other terminologies.
D3171 Test Methods for Constituent Content of Composite
3.2 Symbols:
Materials
b = width of specimen
D3878 Terminology for Composite Materials
CV = coefficient of variation statistic of a sample population
D5229/D5229M Test Method for MoistureAbsorption Prop-
for a given property (in percent)
L = length of specimen
1 P = force on specimen
This test method is under the jurisdiction of ASTM Committee D30 on
Composite Materials and is the direct responsibility of Subcommittee D30.09 on
S = standard deviation statistic of a sample population for
n-1
Sandwich Construction.
a given property
Current edition approved Aug. 1, 2012. Published December 2012. Originally
t = core thickness
approved in 1955. Last previous edition approved in 2007 as C364/C364M– 07. c
DOI: 10.1520/C0364_C0364M-07R12. t = nominal facesheet thickness
fs
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C364/C364M − 07 (2012)
x = test result for an individual specimen from the sample joints, voids or other core and facing discontinuities, out-of-
i
population for a given property plane curvature, facing thickness variation, and surface rough-
x¯5 mean or average (estimate of mean) of a sample ness.
population for a given property
6.2 System Alignment—Unintended loading eccentricities
σ = facesheet compressive stress will cause premature failure. Every effort should be made to
eliminate undesirable eccentricities from the test system. Such
4. Summary of Test Method eccentricities may occur as a result of misaligned grips, poor
specimen preparation, or poor alignment of the loading fixture.
4.1 Thistestmethodconsistsofsubjectingasandwichpanel
If there is any doubt as to the alignment inherent in a given test
to monotonically increasing compressive force parallel to the
machine, then the alignment should be checked as discussed in
plane of its faces. The force is transmitted to the panel through
Test Method D3039/D3039M.
either clamped or bonded end supports. Stress and strength are
reported in terms of the nominal cross-sectional area of the two 6.3 Geometry—Specific geometric factors that affect edge-
wise compressive strength of sandwich panels include
facesheets,ratherthantotalsandwichpanelthickness,although
facesheet fiber waviness, core cell geometry (shape, density,
alternate stress calculations may be optionally specified.
orientation), core thickness, specimen shape (L/W ratio), and
4.2 The only acceptable failure modes for edgewise com-
adhesive thickness.
pressivestrengthofsandwichconstructionsarethoseoccurring
6.4 Environment—Resultsareaffectedbytheenvironmental
away from the supported ends. The sandwich column, no
conditions under which the tests are conducted. Specimens
matter how short, usually is subjected to a buckling type of
tested in various environments can exhibit significant differ-
failure unless the facings are so thick that they themselves are
ences in both static strength and failure mode. Critical envi-
in the short column class. The failure of the facings manifests
ronments must be assessed independently for each sandwich
itself by wrinkling of the facing, in which the core deforms to
construction tested.
the wavy shape of the facings; by dimpling of the facings into
the honeycomb cells; by bending of the sandwich, resulting in
7. Apparatus
crimping near the ends as a result of shear failure of the core;
or by failure in the facing-to-core bond and associated 7.1 Micrometers—The micrometer(s) shall use a 4- to 6-mm
facesheet buckling. [0.16- to 0.25-in.] nominal diameter ball-interface on irregular
surfaces such as the bag-side of a facing laminate, and a flat
anvil interface on machined edges or very smooth-tooled
5. Significance and Use
surfaces.Theaccuracyoftheinstrument(s)shallbesuitablefor
5.1 The edgewise compressive strength of short sandwich
reading to within1%ofthe sample length, width and
construction specimens provides a basis for judging the load-
thickness. For typical specimen geometries, an instrument with
carrying capacity of the construction in terms of developed
an accuracy of 625 µm [60.001 in.] is desirable for thickness,
facing stress.
length and width measurement. .
5.2 This test method provides a standard method of obtain-
7.2 Test Fixtures:
ing sandwich edgewise compressive strengths for panel design
7.2.1 Spherical Bearing Block, preferably of the suspended,
properties, material specifications, research and development
self-aligning type.
applications, and quality assurance.
7.2.2 Lateral End Supports—Via (1) clamps made of rect-
5.3 The reporting section requires items that tend to influ-
angular steel bars fastened together so as to clamp the
ence edgewise compressive strength to be reported; these
specimen lightly between them (the cross-sectional dimensions
include materials, fabrication method, facesheet lay-up orien-
of each of these bars shall be not less than 6 mm [0.25 in.],
tation (if composite), core orientation, results of any nonde-
such as that shown in Fig. 1;(2) fitting the specimen snugly
structive inspections, specimen preparation, test equipment
intoalengthwiseslotinaroundsteelbar,wheresuchbarsshall
details, specimen dimensions and associated measurement
haveadiameternotlessthanthethicknessofthesandwichplus
accuracy, environmental conditions, speed of testing, failure
6 mm [0.25 in.], and are suitably retained on the spherical
mode, and failure location.
bearingblocksurfaces;or(3)castingtheendsofthespecimens
in resin or other suitable molding material.The cast ends of the
6. Interferences specimen should be ground flat and parallel, meeting or
exceeding the specimen end tolerances shown in Fig. 2 and
6.1 MaterialandSpecimenPreparation—Poormaterialfab-
Fig. 3.
rication practices, lack of control of fiber alignment, and
damage induced by improper specimen machining are known 7.3 Testing Machine—The testing machine shall be in ac-
causes of high data scatter in composites in general. Specific cordance with Practices E4 and shall satisfy the following
material factors that affect sandwich composites include vari- requirements:
abilityincoredensityanddegreeofcureofresininbothfacing 7.3.1 Testing Machine Configuration—The testing machine
matrix material and core bonding adhesive. Important aspects shall have both an essentially stationary head and a movable
of sandwich panel specimen preparation that contribute to data head.
scatter are incomplete or nonuniform core bonding to facings, 7.3.2 Drive Mechanism—The testing machine drive mecha-
misalignment of core and facing elements, the existence of nism shall be capable of imparting to the movable head a
C364/C364M − 07 (2012)
FIG. 1 Edgewise Compression Test Setup
controlled velocity with respect to the stationary head. The 8. Sampling and Test Specimens
velocity of the movable head shall be capable of being
8.1 Sampling—Test at least five specimens per test condi-
regulated in accordance with 11.6.
tion unless valid results can be gained through the use of fewer
7.3.3 Force Indicator—The testing machine force-sensing
specimens, as in the case of a designed experiment. For
device shall be capable of indicating the total force being
statistically significant data, consult the procedures outlined in
carried by the test specimen. This device shall be essentially
Practice E122. Report the method of sampling.
free from inertia lag at the specified rate of testing and shall
8.2 Geometry—The test specimens shall be as shown in Fig.
indicate the force with an accuracy over the force range(s) of
2 (inch-pound units) and Fig. 3 [SI units].
interest of within 61 % of the indicated value.
7.3.4 Strain Gage—Capable of measuring strain to at least 8.3 Specimen Preparation and Machining—Guide D5687/
0.0001 mm/mm [0.0001 in./in.] and having a gage length not D5687M provides recommended specimen preparation prac-
greater than two thirds of the unsupported length of the ticesandshouldbefollowedwherepractical.Ofparticularnote
specimens to be tested, nor less than three unit cells if the in this end-loaded compression test is the machining quality
facesheet is a composite fabric material form. and dimensional accuracy of the loaded ends, and the overall
flatness and parallelism of the sandwich panel, as denoted in
7.4 Conditioning Chamber—When conditioning materials
Fig. 2 and Fig. 3.
at non-laboratory environments, a temperature/vapor-level
8.3.1 Labeling—Label the test specimens so that they will
controlledenvironmentalconditioningchamberisrequiredthat
be distinct from each other and traceable back to the panel of
shall be capable of maintaining the required temperature to
origin, and will neither influence the test nor be affected by it.
within 63°C [65°F] and the required relative humidity level
to within 63 %. Chamber conditions shall be monitored either
9. Calibration
on an automated continuous basis or on a manual basis at
9.1 The accuracy of all measuring equipment shall have
regular intervals.
certified calibrations that are current at the time of use of the
7.5 Environmental Test Chamber—An environmental test
equipment.
chamber is required for test environments other than ambient
10. Conditioning
testing laboratory conditions. This chamber shall be capable of
maintaining the entire test specimen at the required test 10.1 The recommended pre-test specimen condition is ef-
environment during the mechanical test. fective moisture equilibrium at a specific relative humidity as
C364/C364M − 07 (2012)
Dimension Recommended Range
Length, L (in.) L#8× t
Width, W (in.) 2.00# W# L; W$2× t;W$ 4 × cell widths (honeycomb only)
t, total panel thickness (in.) As required, in order to be representative of intended use
Facesheet thickness, t (in.) As required, in order to be representative of intended use
fs
Core thickness, t (in.) As required, in order to be representative of intended use
c
FIG. 2 Test Specimen Dimension (inch-pound version)
and data recording equipment. Estimate the specimen strength to aid in
established by Test Method D5229/D5229M; however, it the
transducer selection, calibration of equipment, and determination of
test requester does not specify a pre-test conditioning
equipment settings.
environment, conditioning is not required and the test speci-
11.1.3 The environmental conditioning parameters.
mens may be tested as prepared.
NOTE 1—The term moisture, as used in Test Method D5229/D5229M,
11.1.4 If performed, sampling method, specimen geometry,
includes not only the vapor of a liquid and its condensate, but the liquid
and test parameters used to determine facing density and
itself in large quantities, as for immersion.
reinforcement volume.
10.2 The pre-test specimen conditioning process, to include
11.2 General Instructions:
specified environmental exposure levels and resulting moisture
11.2.1 Report any deviations from this test method, whether
content, shall be reported with the data.
intentional or inadvertent.
10.3 If there is no explicit conditioning process, the condi-
11.2.2 If specific gravity, density, facing reinforcement
tioning process shall be reported as “unconditioned” and the
volume, or facing void volume are to be reported, then obtain
moisture content as “unknown.”
these samples from the same panels
...
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