ASTM C366/C366M-16(2022)e1
(Test Method)Standard Test Methods for Measurement of Thickness of Sandwich Cores
Standard Test Methods for Measurement of Thickness of Sandwich Cores
SIGNIFICANCE AND USE
5.1 Normally, a close tolerance is desirable for core thickness so that sandwich panels may be manufactured with all the sandwich components fitting properly and without crushing the core.
5.2 These test methods are designed for measuring thickness of core as it is produced and are not intended for use in determining dimensions of core specimens for other tests.
5.3 These test methods provide standard methods of obtaining the core thickness of flat sandwich core materials, and provide a basis for determining average thickness dimensions. The thickness properties derived may be used in design properties, material specifications, research and development applications, and quality assurance.
5.4 Factors that influence core thickness measurement and shall therefore be reported include the following: core material through-thickness rigidity, surface roughness, specimen geometry (including warpage), specimen preparation, methods of dimensional measurement, specimen conditioning, and moisture content during dimensional measurements.
SCOPE
1.1 These test methods cover plant manufacturing procedures for measuring the thickness of flat sandwich cores. 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). The two test methods covered include the following:
1.1.1 Test Method A—Roller-Type Thickness Tester.
1.1.2 Test Method B—Disk-Type Thickness Tester.
Note 1: These test methods are designed for measuring thickness of core as it is produced and are not intended for use in determining dimensions of core specimens for other tests.
1.2 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.
1.2.1 Within the text, the inch-pound units are shown in brackets.
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: C366/C366M − 16 (Reapproved 2022)
Standard Test Methods for
Measurement of Thickness of Sandwich Cores
This standard is issued under the fixed designation C366/C366M; 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 U.S. Department of Defense.
ε NOTE—Editorial corrections were made in Section 1 in May 2022.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 These test methods cover plant manufacturing proce-
D883 Terminology Relating to Plastics
dures for measuring the thickness of flat sandwich cores.
D3878 Terminology for Composite Materials
Permissible core material forms include those with continuous
D5229/D5229M Test Method for MoistureAbsorption Prop-
bonding surfaces (such as balsa wood and foams) as well as
erties and Equilibrium Conditioning of Polymer Matrix
those with discontinuous bonding surfaces (such as honey-
Composite Materials
comb). The two test methods covered include the following:
E122 Practice for Calculating Sample Size to Estimate,With
1.1.1 Test Method A—Roller-Type Thickness Tester.
Specified Precision, the Average for a Characteristic of a
1.1.2 Test Method B—Disk-Type Thickness Tester.
Lot or Process
E171 Practice for Conditioning and Testing Flexible Barrier
NOTE 1—These test methods are designed for measuring thickness of
Packaging
core as it is produced and are not intended for use in determining
dimensions of core specimens for other tests.
E177 Practice for Use of the Terms Precision and Bias in
ASTM Test Methods
1.2 Units—The values stated in either SI units or inch-
E456 Terminology Relating to Quality and Statistics
pound units are to be regarded separately as standard. The
values stated in each system are not necessarily exact equiva-
3. Terminology
lents; therefore, to ensure conformance with the standard, each
system shall be used independently of the other, and values 3.1 Definitions—Terminology D3878 defines terms relating
to high-modulus fibers and their composites, as well as terms
from the two systems shall not be combined.
relating to sandwich constructions. Terminology D883 defines
1.2.1 Within the text, the inch-pound units are shown in
termsrelatingtoplastics.TerminologyE456andPracticeE177
brackets.
define terms relating to statistics. In the event of a conflict
1.3 This standard does not purport to address all of the
between terms, Terminology D3878 shall have precedence
safety concerns, if any, associated with its use. It is the
over the other terminologies.
responsibility of the user of this standard to establish appro-
3.2 Symbols:
priate safety, health, and environmental practices and deter-
3.2.1 CV—coefficient of variation statistic of a sample
mine the applicability of regulatory limitations prior to use.
population for a given property (in percent)
1.4 This international standard was developed in accor-
3.2.2 S —standard deviation statistic of a sample popula-
dance with internationally recognized principles on standard- n-1
tion for a given property
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
3.2.3 X —test result for an individual specimen from the
i
mendations issued by the World Trade Organization Technical
sample population for a given property
Barriers to Trade (TBT) Committee.
3.2.4 x¯—mean or average (estimate of mean) of a sample
population for a given property
These test methods are under the jurisdiction of ASTM Committee D30 on
Composite Materials and are the direct responsibility of Subcommittee D30.09 on
Sandwich Construction. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 1, 2022. Published May 2022. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1955. Last previous edition approved in 2016 as C366/C366M – 16. Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/C0366_C0366M-16R22E01. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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C366/C366M − 16 (2022)
4. Summary of Test Methods
4.1 These test methods consist of environmentally condi-
tioning a sandwich core specimen, zeroing a thickness tester,
placing the core underneath the tester, and measuring the core
thickness by sliding the core underneath the tester. Procedures
are provided for thickness measurement using both roller-type
and disk-type thickness testers.
5. Significance and Use
5.1 Normally, a close tolerance is desirable for core thick-
ness so that sandwich panels may be manufactured with all the
sandwich components fitting properly and without crushing the
core.
5.2 These test methods are designed for measuring thick-
ness of core as it is produced and are not intended for use in
determining dimensions of core specimens for other tests.
5.3 These test methods provide standard methods of obtain-
ing the core thickness of flat sandwich core materials, and
provide a basis for determining average thickness dimensions.
The thickness properties derived may be used in design
properties, material specifications, research and development
applications, and quality assurance.
5.4 Factors that influence core thickness measurement and
shall therefore be reported include the following: core material
through-thickness rigidity, surface roughness, specimen geom-
etry (including warpage), specimen preparation, methods of
dimensional measurement, specimen conditioning, and mois-
ture content during dimensional measurements.
6. Interferences
6.1 Material and Specimen Preparation—Poormaterialfab-
FIG. 1 Roller-Type Thickness Tester
rication practices and damage induced by improper specimen
machining are known causes of high data scatter in composites
and sandwich structures in general. Important aspects of
dial gage, calibrated in 0.01 mm [0.001 in.] increments, that
sandwich core specimen preparation that contribute to data
registers the amount of variation above or below a preset
scatter include the existence of joints, voids or other core
nominal dimension. The lower roller shall be fixed in position
discontinuities, out-of-plane curvature/warpage, and surface
so that it projects 6 mm [0.25 in.] above the measurement
roughness.
surface. The upper roller shall exert a force of 18 N [4 lbf] on
the core material.
6.2 Measurement Equipment and Procedures—Results are
affected by the method of thickness measurement, use of
7.2 Method B—Disk-Type Thickness Tester:
pressure to flatten warped core, and the distance along which
7.2.1 Disk-Type Thickness Tester—The tester shall consist
thickness is measured.
of a flat table with a rigid yoke framework attached, as shown
in Fig. 2. A 25 mm [1 in.] diameter presser disk movable in a
6.3 Environment—Resultsareaffectedbytheenvironmental
vertical direction shall be mounted on the yoke. The vertical
conditions under which specimens are conditioned, as well as
movement of the disk shall be translated to a dial gage,
the conditions under which the tests are conducted. Specimens
calibrated in 0.01 mm [0.001 in.] increments, that registers the
testedinvariousenvironments,withdifferentambientmoisture
amount of variation above or below a preset nominal dimen-
contents, can exhibit significant differences in measured thick-
sion. The disk shall exert a force of 24 N [5.5 lbf] on the core
ness.
material.
7. Apparatus
7.3 Measurement Surface—A flat, rigid surface shall be
positioned such that the specimen can be supported underneath
7.1 Test Method A—Roller-Type Thickness Tester:
the thickness tester without bending or warping.
7.1.1 Roller-Type Thickness Tester—The tester shall consist
of a flat table with a rigid yoke framework attached, as shown
8. Sampling and Test Specimens
in Fig. 1. Two rollers shall be mounted on this yoke, one fixed
in position and one movable in the vertical direction. The 8.1 Sampling—Test at least five specimens per test
vertical movement of the upper roller shall be translated to a condition, or take five readings from alternative locations on a
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C366/C366M − 16 (2022)
FIG. 2 Disk-Type Thickness Tester
single large specimen, unless valid results can be gained explicitly specify a pre-test conditioning environment, no
through the use of fewer specimens, as in the case of a conditioning is required and the test specimens may be tested
designed experiment. For statistically significant data, consult as prepare
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