ASTM C364/C364M-16
(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
5.1 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.
5.2 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.
5.3 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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Designation: C364/C364M − 16
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 Composite Materials
D5687/D5687M Guide for Preparation of Flat Composite
1.1 This test method covers the compressive properties of
Panels with Processing Guidelines for Specimen Prepara-
structural sandwich construction in a direction parallel to the
tion
sandwichfacingplane.Permissiblecorematerialformsinclude
E4 Practices for Force Verification of Testing Machines
those with continuous bonding surfaces (such as balsa wood
E6 Terminology Relating to Methods of Mechanical Testing
and foams) as well as those with discontinuous bonding
E122 Practice for Calculating Sample Size to Estimate,With
surfaces (such as honeycomb).
Specified Precision, the Average for a Characteristic of a
1.2 The values stated in either SI units or inch-pound units
Lot or Process
are to be regarded separately as standard. Within the text the
E177 Practice for Use of the Terms Precision and Bias in
inch-pound units are shown in brackets. The values stated in
ASTM Test Methods
each system are not exact equivalents; therefore, each system
E456 Terminology Relating to Quality and Statistics
must be used independently of the other. Combining values
E1012 Practice for Verification of Testing Frame and Speci-
from the two systems may result in nonconformance with the
men Alignment Under Tensile and Compressive Axial
standard.
Force Application
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3. Terminology
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
3.1 Definitions—Terminology D3878 defines terms relating
bility of regulatory limitations prior to use.
to high-modulus fibers and their composites, as well as terms
relating to sandwich constructions. Terminology D883 defines
2. Referenced Documents
E6 defines terms
terms relating to plastics. Terminology
2.1 ASTM Standards:
relating to mechanical testing. Terminolgoy E456 and Practice
D792 Test Methods for Density and Specific Gravity (Rela-
E177 define terms relating to statistics. In the event of a
tive Density) of Plastics by Displacement
conflict between terms, Terminology D3878 shall have prece-
D883 Terminology Relating to Plastics
dence over the other terminologies.
D2584 Test Method for Ignition Loss of Cured Reinforced
3.2 Symbols: b = width of specimen
Resins
D2734 TestMethodsforVoidContentofReinforcedPlastics CV = coefficient of variation statistic of a sample population
D3039/D3039M Test Method for Tensile Properties of Poly- for a given property (in percent)
mer Matrix Composite Materials
L = length of specimen
D3171 Test Methods for Constituent Content of Composite
P = force on specimen
Materials
S = standard deviation statistic of a sample population for
n-1
D3878 Terminology for Composite Materials
a given property
D5229/D5229M Test Method for MoistureAbsorption Prop-
t = core thickness
erties and Equilibrium Conditioning of Polymer Matrix c
t = nominal facesheet thickness
fs
x = test result for an individual specimen from the sample
i
This test method is under the jurisdiction of ASTM Committee D30 on
population for a given property
Composite Materials and is the direct responsibility of Subcommittee D30.09 on
x¯5 mean or average (estimate of mean) of a sample
Sandwich Construction.
Current edition approved April 1, 2016. Published April 2016. Originally
population for a given property
approved in 1955. Last previous edition approved in 2012 as C364/
C364M – 07(2012). DOI: 10.1520/C0364_C0364M-16. σ = facesheet compressive stress
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C364/C364M − 16
4. Summary of Test Method specimen preparation, or poor alignment of the loading fixture.
If there is any doubt as to the alignment inherent in a given test
4.1 Thistestmethodconsistsofsubjectingasandwichpanel
machine, then the alignment should be checked as discussed in
to monotonically increasing compressive force parallel to the
Test Method D3039/D3039M.
plane of its faces. The force is transmitted to the panel through
either clamped or bonded end supports. Stress and strength are 6.3 Geometry—Specific geometric factors that affect edge-
reported in terms of the nominal cross-sectional area of the two 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
adhesive thickness.
4.2 The only acceptable failure modes for edgewise com-
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;
7.1 Micrometers—The micrometer(s) shall use a 4- to 6-mm
or by failure in the facing-to-core bond and associated
[0.16- to 0.25-in.] nominal diameter ball-interface on irregular
facesheet buckling.
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
6.1 MaterialandSpecimenPreparation—Poormaterialfab- exceeding the specimen end tolerances shown in Fig. 2 and
rication practices, lack of control of fiber alignment, and Fig. 3.
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
joints, voids or other core and facing discontinuities, out-of-
controlled velocity with respect to the stationary head. The
plane curvature, facing thickness variation, and surface rough-
velocity of the movable head shall be capable of being
ness.
regulated in accordance with 11.6.
6.2 System Alignment—Unintended loading eccentricities 7.3.3 Force Indicator—The testing machine force-sensing
will cause premature failure. Every effort should be made to device shall be capable of indicating the total force being
eliminate undesirable eccentricities from the test system. Such carried by the test specimen. This device shall be essentially
eccentricities may occur as a result of misaligned grips, poor free from inertia lag at the specified rate of testing and shall
C364/C364M − 16
FIG. 1 Edgewise Compression Test Setup
indicate the force with an accuracy over the force range(s) of 8.2 Geometry—The test specimens shall be as shown in Fig.
interest of within 61 % of the indicated value. 2 (inch-pound units) and Fig. 3 [SI units].
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
7.4 Conditioning Chamber—When conditioning materials flatness and parallelism of the sandwich panel, as denoted in
at non-laboratory environments, a temperature/vapor-level Fig. 2 and Fig. 3.
controlledenvironmentalconditioningchamberisrequiredthat 8.3.1 Labeling—Label the test specimens so that they will
shall be capable of maintaining the required temperature to be distinct from each other and traceable back to the panel of
within 63°C [65°F] and the required relative humidity level origin, and will neither influence the test nor be affected by it.
to within 63 %. Chamber conditions shall be monitored either
9. Calibration
on an automated continuous basis or on a manual basis at
regular intervals. 9.1 The accuracy of all measuring equipment shall have
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
testing laboratory conditions. This chamber shall be capable of
10. Conditioning
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
established by Test Method D5229/D5229M; however, it the
8. Sampling and Test Specimens
test requester does not specify a pre-test conditioning
8.1 Sampling—Test at least five specimens per test condi-
environment, conditioning is not required and the test speci-
tion unless valid results can be gained through the use of fewer
mens may be tested as prepared.
specimens, as in the case of a designed experiment. For
NOTE 1—The term moisture, as used in Test Method D5229/D5229M,
statistically significant data, consult the procedures outlined in
includes not only the vapor of a liquid and its condensate, but the liquid
Practice E122. Report the method of sampling. itself in large quantities, as for immersion.
C364/C364M − 16
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)
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 being tested. Specific
gravity and density may be evaluated in accordance with Test
11. Procedure
Methods D792. Volume percent of composite facing constitu-
ents may be evaluated by one of the matrix digestion proce-
11.1 Parameters to be Specified Before Test:
dures of Test Method D3171, or, for certain reinforcement
11.1.1 The specimen sampling method, specimen geometry,
materials such as glass and ceramics, by the matrix burn-off
and conditioning travelers (if required).
technique in accordance with Test Method D2584. The void
11.1.2 The properties and data reporting format desired.
content equati
...
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.
Designation: C364/C364M − 07 (Reapproved 2012) C364/C364M − 16
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
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.
2. Referenced Documents
2.1 ASTM Standards:
C274 Terminology of Structural Sandwich Constructions (Withdrawn 2016)
D792 Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement
D883 Terminology Relating to Plastics
D2584 Test Method for Ignition Loss of Cured Reinforced Resins
D2734 Test Methods for Void Content of Reinforced Plastics
D3039/D3039M Test Method for Tensile Properties of Polymer Matrix Composite Materials
D3171 Test Methods for Constituent Content of Composite Materials
D3878 Terminology for Composite Materials
D5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite
Materials
D5687/D5687M Guide for Preparation of Flat Composite Panels with Processing Guidelines for Specimen Preparation
E4 Practices for Force Verification of Testing Machines
E6 Terminology Relating to Methods of Mechanical Testing
E122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or
Process
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E456 Terminology Relating to Quality and Statistics
E1012 Practice for Verification of Testing Frame and Specimen Alignment Under Tensile and Compressive Axial Force
Application
E1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in Databases (Withdrawn 2015)
E1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases (Withdrawn 2015)
E1471 Guide for Identification of Fibers, Fillers, and Core Materials in Computerized Material Property Databases (Withdrawn
2015)
This test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.09 on Sandwich
Construction.
Current edition approved Aug. 1, 2012April 1, 2016. Published December 2012April 2016. Originally approved in 1955. Last previous edition approved in 20072012 as
C364/C364M– 07. – 07(2012). DOI: 10.1520/C0364_C0364M-07R12.10.1520/C0364_C0364M-16.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C364/C364M − 16
3. Terminology
3.1 Definitions—Terminology D3878 defines terms relating to high-modulus fibers and their composites.
Terminologycomposites, as C274 defineswell as terms relating to structural sandwich constructions. Terminology D883 defines
terms relating to plastics. Terminology E6 defines terms relating to mechanical testing. Terminolgoy E456 and Practice E177 define
terms relating to statistics. In the event of a conflict between terms, Terminology D3878 shall have precedence over the other
terminologies.
3.2 Symbols: b = width of specimen
CV = coefficient of variation statistic of a sample population for a given property (in percent)
L = length of specimen
P = force on specimen
S = standard deviation statistic of a sample population for a given property
n-1
t = core thickness
c
t = nominal facesheet thickness
fs
x = test result for an individual specimen from the sample population for a given property
i
x¯5 mean or average (estimate of mean) of a sample population for a given property
σ = facesheet compressive stress
4. Summary of Test Method
4.1 This test method consists of subjecting a sandwich panel to monotonically increasing compressive force parallel to the plane
of its faces. The force is transmitted to the panel through either clamped or bonded end supports. Stress and strength are reported
in terms of the nominal cross-sectional area of the two facesheets, rather than total sandwich panel thickness, although alternate
stress calculations may be optionally specified.
4.2 The only acceptable failure modes for edgewise compressive strength of sandwich constructions are those occurring away
from the supported ends. The sandwich column, no matter how short, usually is subjected to a buckling type of failure unless the
facings are so thick that they themselves are in the short column class. The failure of the facings manifests itself by wrinkling of
the facing, in which the core deforms to the wavy shape of the facings; by dimpling of the facings into the honeycomb cells; by
bending of the sandwich, resulting in crimping near the ends as a result of shear failure of the core; or by failure in the
facing-to-core bond and associated facesheet buckling.
5. Significance and Use
5.1 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.
5.2 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.
5.3 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, environ-
mental conditions, speed of testing, failure mode, and failure location.
6. Interferences
6.1 Material and Specimen Preparation—Poor material fabrication practices, lack of control of fiber alignment, and damage
induced by improper specimen machining are known causes of high data scatter in composites in general. Specific material factors
that affect sandwich composites include variability in core density and degree of cure of resin in both facing matrix material and
core bonding adhesive. Important aspects of sandwich panel specimen preparation that contribute to data scatter are incomplete
or nonuniform core bonding to facings, misalignment of core and facing elements, the existence of joints, voids or other core and
facing discontinuities, out-of-plane curvature, facing thickness variation, and surface roughness.
6.2 System Alignment—Unintended loading eccentricities will cause premature failure. Every effort should be made to eliminate
undesirable eccentricities from the test system. Such eccentricities may occur as a result of misaligned grips, poor specimen
preparation, or poor alignment of the loading fixture. If there is any doubt as to the alignment inherent in a given test machine,
then the alignment should be checked as discussed in Test Method D3039/D3039M.
6.3 Geometry—Specific geometric factors that affect edgewise compressive strength of sandwich panels include facesheet fiber
waviness, core cell geometry (shape, density, orientation), core thickness, specimen shape (L/W ratio), and adhesive thickness.
6.4 Environment—Results are affected by the environmental conditions under which the tests are conducted. Specimens tested
in various environments can exhibit significant differences in both static strength and failure mode. Critical environments must be
assessed independently for each sandwich construction tested.
C364/C364M − 16
7. Apparatus
7.1 Micrometers—The micrometer(s) shall use a 4- to 6-mm [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 surfaces.
The accuracy of the instrument(s) shall be suitable for reading to within 1 % of the sample length, width and thickness. For typical
specimen geometries, an instrument with an accuracy of 625 μm [60.001 in.] is desirable for thickness, length and width
measurement. .
7.2 Test Fixtures:
7.2.1 Spherical Bearing Block, preferably of the suspended, self-aligning type.
7.2.2 Lateral End Supports—Via (1) clamps made of rectangular steel bars fastened together so as to clamp the specimen lightly
between them (the cross-sectional dimensions of each of these bars shall be not less than 6 mm [0.25 in.], such as that shown in
Fig. 1; (2) fitting the specimen snugly into a lengthwise slot in a round steel bar, where such bars shall have a diameter not less
than the thickness of the sandwich plus 6 mm [0.25 in.], and are suitably retained on the spherical bearing block surfaces; or (3)
casting the ends of the specimens in resin or other suitable molding material. The cast ends of the specimen should be ground flat
and parallel, meeting or exceeding the specimen end tolerances shown in Fig. 2 and Fig. 3.
7.3 Testing Machine—The testing machine shall be in accordance with Practices E4 and shall satisfy the following
requirements:
7.3.1 Testing Machine Configuration—The testing machine shall have both an essentially stationary head and a movable head.
7.3.2 Drive Mechanism—The testing machine drive mechanism shall be capable of imparting to the movable head a controlled
velocity with respect to the stationary head. The velocity of the movable head shall be capable of being regulated in accordance
with 11.6.
7.3.3 Force Indicator—The testing machine force-sensing device shall be capable of indicating the total force being carried by
the test specimen. This device shall be essentially free from inertia lag at the specified rate of testing and shall indicate the force
with an accuracy over the force range(s) of interest of within 61 % of the indicated value.
7.3.4 Strain Gage—Capable of measuring strain to at least 0.0001 mm/mm [0.0001 in./in.] and having a gage length not greater
than two thirds of the unsupported length of the specimens to be tested, nor less than three unit cells if the facesheet is a composite
fabric material form.
FIG. 1 Edgewise Compression Test Setup
C364/C364M − 16
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)
7.4 Conditioning Chamber—When conditioning materials at non-laboratory environments, a temperature/vapor-level controlled
environmental conditioning chamber is required that shall be capable of maintaining the required temperature to within 63°C
[65°F] and the required relative humidity level to within 63 %. Chamber conditions shall be monitored either on an automated
continuous basis or on a manual basis at regular intervals.
7.5 Environmental Test Chamber—An environmental test chamber is required for test environments other than ambient testing
laboratory conditions. This chamber shall be capable of maintaining the entire test specimen at the required test environment during
the mechanical test.
8. Sampling and Test Specimens
8.1 Sampling—Test at least five specimens per test condition unless valid results can be gained through the use of fewer
specimens, as in the case of a designed experiment. For statistically significant data, consult the procedures outlined in Practice
E122. Report the method of sampling.
8.2 Geometry—The test specimens shall be as shown in Fig. 2 (inch-pound units) and Fig. 3 [SI units].
8.3 Specimen Preparation and Machining—Guide D5687/D5687M provides recommended specimen preparation practices and
should be followed where practical. Of particular note in this end-loaded compression test is the machining quality and dimensional
accuracy of the loaded ends, and the overall flatness and parallelism of the sandwich panel, as denoted in Fig. 2 and Fig. 3.
8.3.1 Labeling—Label the test specimens so that they will be distinct from each other and traceable back to the panel of origin,
and will neither influence the test nor be affected by it.
9. Calibration
9.1 The accuracy of all measuring equipment shall have certified calibrations that are current at the time of use of the equipment.
C364/C364M − 16
Dimension Recommended Range
Length, L (mm) L # 8 × t
Width, W (mm) 50 # W # L; W $ 2 × t; W $ 4 × cell widths (honeycomb only)
t, total panel thickness (mm) As required, in order to be representative of intended use
Facesheet thickness, t (mm) As required, in order to be representative of intended use
fs
Core thickness, t (mm) As required, in order to be representative of intended use
c
FIG. 3 Test Specimen Dimensions (SI version)
10. Conditioning
10.1 The recommended pre-test specimen condition is effective moisture equilibrium at a specific relative humidity as
established by Test Method D5229/D5229M; however, it the test requester does not specify a pre-test conditioning environment,
conditioning is not required and the test specimens may be tested as prepared.
NOTE 1—The term moisture, as used in Test Method D5229/D5229M, includes not only th
...
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
Designation: C364/C364M − 16
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 Composite Materials
D5687/D5687M Guide for Preparation of Flat Composite
1.1 This test method covers the compressive properties of
Panels with Processing Guidelines for Specimen Prepara-
structural sandwich construction in a direction parallel to the
tion
sandwich facing plane. Permissible core material forms include
E4 Practices for Force Verification of Testing Machines
those with continuous bonding surfaces (such as balsa wood
E6 Terminology Relating to Methods of Mechanical Testing
and foams) as well as those with discontinuous bonding
E122 Practice for Calculating Sample Size to Estimate, With
surfaces (such as honeycomb).
Specified Precision, the Average for a Characteristic of a
1.2 The values stated in either SI units or inch-pound units
Lot or Process
are to be regarded separately as standard. Within the text the
E177 Practice for Use of the Terms Precision and Bias in
inch-pound units are shown in brackets. The values stated in
ASTM Test Methods
each system are not exact equivalents; therefore, each system
E456 Terminology Relating to Quality and Statistics
must be used independently of the other. Combining values
E1012 Practice for Verification of Testing Frame and Speci-
from the two systems may result in nonconformance with the
men Alignment Under Tensile and Compressive Axial
standard.
Force Application
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3. Terminology
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
3.1 Definitions—Terminology D3878 defines terms relating
bility of regulatory limitations prior to use.
to high-modulus fibers and their composites, as well as terms
relating to sandwich constructions. Terminology D883 defines
2. Referenced Documents
terms relating to plastics. Terminology E6 defines terms
2.1 ASTM Standards:
relating to mechanical testing. Terminolgoy E456 and Practice
D792 Test Methods for Density and Specific Gravity (Rela-
E177 define terms relating to statistics. In the event of a
tive Density) of Plastics by Displacement
conflict between terms, Terminology D3878 shall have prece-
D883 Terminology Relating to Plastics
dence over the other terminologies.
D2584 Test Method for Ignition Loss of Cured Reinforced
3.2 Symbols: b = width of specimen
Resins
CV = coefficient of variation statistic of a sample population
D2734 Test Methods for Void Content of Reinforced Plastics
D3039/D3039M Test Method for Tensile Properties of Poly- for a given property (in percent)
mer Matrix Composite Materials
L = length of specimen
D3171 Test Methods for Constituent Content of Composite
P = force on specimen
Materials
S = standard deviation statistic of a sample population for
n-1
D3878 Terminology for Composite Materials
a given property
D5229/D5229M Test Method for Moisture Absorption Prop-
t = core thickness
erties and Equilibrium Conditioning of Polymer Matrix c
t = nominal facesheet thickness
fs
x = test result for an individual specimen from the sample
i
This test method is under the jurisdiction of ASTM Committee D30 on
population for a given property
Composite Materials and is the direct responsibility of Subcommittee D30.09 on
x¯5 mean or average (estimate of mean) of a sample
Sandwich Construction.
Current edition approved April 1, 2016. Published April 2016. Originally
population for a given property
approved in 1955. Last previous edition approved in 2012 as C364/
C364M – 07(2012). DOI: 10.1520/C0364_C0364M-16. σ = facesheet compressive stress
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C364/C364M − 16
4. Summary of Test Method specimen preparation, or poor alignment of the loading fixture.
If there is any doubt as to the alignment inherent in a given test
4.1 This test method consists of subjecting a sandwich panel
machine, then the alignment should be checked as discussed in
to monotonically increasing compressive force parallel to the
Test Method D3039/D3039M.
plane of its faces. The force is transmitted to the panel through
either clamped or bonded end supports. Stress and strength are 6.3 Geometry—Specific geometric factors that affect edge-
reported in terms of the nominal cross-sectional area of the two wise compressive strength of sandwich panels include
facesheets, rather than total sandwich panel thickness, 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
adhesive thickness.
4.2 The only acceptable failure modes for edgewise com-
pressive strength of sandwich constructions are those occurring 6.4 Environment—Results are affected by the environmental
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;
7.1 Micrometers—The micrometer(s) shall use a 4- to 6-mm
or by failure in the facing-to-core bond and associated
[0.16- to 0.25-in.] nominal diameter ball-interface on irregular
facesheet buckling.
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. The accuracy of the instrument(s) shall be suitable for
5.1 The edgewise compressive strength of short sandwich
reading to within 1 % of the 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 into a lengthwise slot in a round steel bar, where such bars shall
details, specimen dimensions and associated measurement have a diameter not less than the thickness of the sandwich plus
accuracy, environmental conditions, speed of testing, failure
6 mm [0.25 in.], and are suitably retained on the spherical
mode, and failure location. bearing block surfaces; or (3) casting the ends of the specimens
in resin or other suitable molding material. The cast ends of the
6. Interferences
specimen should be ground flat and parallel, meeting or
6.1 Material and Specimen Preparation—Poor material fab- exceeding the specimen end tolerances shown in Fig. 2 and
rication practices, lack of control of fiber alignment, and Fig. 3.
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:
ability in core density and degree of cure of resin in both facing
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
joints, voids or other core and facing discontinuities, out-of-
controlled velocity with respect to the stationary head. The
plane curvature, facing thickness variation, and surface rough-
velocity of the movable head shall be capable of being
ness.
regulated in accordance with 11.6.
6.2 System Alignment—Unintended loading eccentricities 7.3.3 Force Indicator—The testing machine force-sensing
will cause premature failure. Every effort should be made to device shall be capable of indicating the total force being
eliminate undesirable eccentricities from the test system. Such carried by the test specimen. This device shall be essentially
eccentricities may occur as a result of misaligned grips, poor free from inertia lag at the specified rate of testing and shall
C364/C364M − 16
FIG. 1 Edgewise Compression Test Setup
indicate the force with an accuracy over the force range(s) of 8.2 Geometry—The test specimens shall be as shown in Fig.
interest of within 61 % of the indicated value. 2 (inch-pound units) and Fig. 3 [SI units].
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
tices and should be followed where practical. Of particular note
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
7.4 Conditioning Chamber—When conditioning materials flatness and parallelism of the sandwich panel, as denoted in
at non-laboratory environments, a temperature/vapor-level Fig. 2 and Fig. 3.
controlled environmental conditioning chamber is required that 8.3.1 Labeling—Label the test specimens so that they will
shall be capable of maintaining the required temperature to be distinct from each other and traceable back to the panel of
within 63°C [65°F] and the required relative humidity level origin, and will neither influence the test nor be affected by it.
to within 63 %. Chamber conditions shall be monitored either
9. Calibration
on an automated continuous basis or on a manual basis at
regular intervals. 9.1 The accuracy of all measuring equipment shall have
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
testing laboratory conditions. This chamber shall be capable of
10. Conditioning
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
established by Test Method D5229/D5229M; however, it the
8. Sampling and Test Specimens
test requester does not specify a pre-test conditioning
8.1 Sampling—Test at least five specimens per test condi-
environment, conditioning is not required and the test speci-
tion unless valid results can be gained through the use of fewer
mens may be tested as prepared.
specimens, as in the case of a designed experiment. For
NOTE 1—The term moisture, as used in Test Method D5229/D5229M,
statistically significant data, consult the procedures outlined in
includes not only the vapor of a liquid and its condensate, but the liquid
Practice E122. Report the method of sampling. itself in large quantities, as for immersion.
C364/C364M − 16
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)
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 being tested. Specific
gravity and density may be evaluated in accordance with Test
11. Procedure
Methods D792. Volume percent of composite facing constitu-
ents may be evaluated by one of the matrix digestion proce-
11.1 Parameters to be Specified Before Test:
dures of Test Method D3171, or, for certain reinforcement
11.1.1 The specimen sampling method, specimen geometry,
materials such as glass and ceramics, by the matrix burn-off
and conditioning travelers (if required).
technique in accordance with Test Method D2584. The void
11.1.2 The properties and data reporting format desired.
c
...
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