Designation: C 365/C 365M – 05

Standard Test Method for

Flatwise Compressive Properties of Sandwich Cores1
This standard is issued under the fixed designation C 365/C 365M; 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.
--`,,```,,,,````-`-`,,`,,`,`,,`---

1. Scope E 6 Terminology Relating to Methods of Mechanical Test-

1.1 This test method covers the determination of compres- ing
sive strength and modulus of sandwich cores. These properties E 122 Practice for Calculation of Sample Size. Within a
are usually determined for design purposes in a direction Specified Tolerable Error, the Average for Characteristic of
normal to the plane of facings as the core would be placed in a Lot or Process
a structural sandwich construction. The test procedures pertain E 177 Practice for Use of the Terms Precision and Bias in
to compression in this direction in particular, but also can be ASTM Test Methods
applied with possible minor variations to determining compres- E 456 Terminology Relating to Quality and Statistics
sive properties in other directions. Permissible core material E 1309 Guide for Identification of Fiber-Reinforced
forms include those with continuous bonding surfaces (such as Polymer-Matrix Composite Materials in Databases
balsa wood and foams) as well as those with discontinuous E 1434 Guide for Recording Mechanical Test Data of Fiber-
bonding surfaces (such as honeycomb). Reinforced Composite Materials in Databases
1.2 The values stated in either SI units or inch-pound units E 1471 Guide for Identification of Fibers, Fillers, and Core
are to be regarded separately as standard. Within the text the Materials in Computerized Material Property Databases
inch-pound units are shown in brackets. The values stated in 3. Terminology
each system are not exact equivalents; therefore, each system
must be used independently of the other. Combining values 3.1 Definitions—Terminology D 3878 defines terms relating
from the two systems may result in nonconformance with the to high-modulus fibers and their composites. Terminology
standard. C 274 defines terms relating to structural sandwich construc-
1.3 This standard does not purport to address all of the tions. Terminology D 883 defines terms relating to plastics.
safety concerns, if any, associated with its use. It is the Terminology E 6 defines terms relating to mechanical testing.
responsibility of the user of this standard to establish appro- Terminology E 456 and Practice E 177 define terms relating to
priate safety and health practices and determine the applica- statistics. In the event of a conflict between terms, Terminology
bility of regulatory limitations prior to use. D 3878 shall have precedence over the other terminologies.
3.2 Symbols:
2. Referenced Documents A = cross-sectional area of a test specimen
2.1 ASTM Standards: 2 CV = coefficient of variation statistic of a sample population
C 271 Test Method for Density of Sandwich Core Materials for a given property (in percent)
C 274 Terminology of Structural Sandwich Constructions Ezfc = flatwise compressive modulus
D 883 Terminology Relating to Plastics Fzfcu = ultimate flatwise compressive strength
D 3878 Terminology for Composite Materials Fzfc0.02 = flatwise compressive strength at 2 % LVDT/
D 5229/D 5229M Test Method for Moisture Absorption compressometer deflection
Properties and Equilibrium Conditioning of Polymer Ma- Pmax = maximum force carried by test specimen before
trix Composite Materials failure
E 4 Practices for Force Verification of Testing Machines P0.02 = force carried by test specimen at 2 % LVDT/
compressometer deflection
Sn–1 = standard deviation statistic of a sample population for
1
This test method is under the jurisdiction of ASTM Committee D30 on a given property
Composite Materials and is the direct responsibility of Subcommittee D30.09 on t = thickness of a test specimen
Sandwich Construction.
Current edition approved Oct. 1, 2005. Published October 2005. Originally x1 = test result for an individual specimen from the sample
approved in 1955. Last previous edition approved in 2003 as C 365 – 03. population for a given property
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or –x = mean or average (estimate of mean) of a sample popu-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on lation for a given property
the ASTM website.

Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.

Copyright ASTM International 1

Reproduced by IHS under license with ASTM Copyright by ASTM Int'l (all rights reserved);
No reproduction or networking permitted without license from IHS Not for Resale
Reproduction authorized per License Agreement with Kathe Hooper (ASTMIHS Account); Mon Oct 31 11:05:36 EST 2005
 C 365/C 365M – 05
d = LVDT or compressometer deflection Flatwise compressive strength and modulus measurements are
s z fc0.02 = flatwise compressive stress at 2 % LVDT/ particularly sensitive to thickness variations over the cross-
compressometer deflection sectional area of the specimen, which can cause local loading
eccentricities, as well as toe regions in the force versus
4. Summary of Test Method displacement curves due to specimen seating.
4.1 This test method consists of subjecting a sandwich core 6.4 Environment—Results are affected by the environmen-
to a uniaxial compressive force normal to the plane of the tal conditions under which specimens are conditioned, as well
facings as the core would be placed in a structural sandwich as the conditions under which the tests are conducted. Speci-
construction. The force is transmitted to the sandwich core mens tested in various environments can exhibit significant
using loading platens attached to the testing machine. differences in both strength behavior and failure mode. Critical
environments must be assessed independently for each core
5. Significance and Use material tested.
5.1 Flatwise compressive strength and modulus are funda- 7. Apparatus
mental mechanical properties of sandwich cores that are used
in designing sandwich panels. Deformation data can be ob- 7.1 Micrometers and Calipers—A micrometer having a flat
tained, and from a complete force versus deformation curve, it anvil interface, or a caliper of suitable size, shall be used. The
is possible to compute the compressive stress at any applied accuracy of the instrument(s) shall be suitable for reading to
force (such as compressive stress at proportional limit force or within 1 % of the sample length and width (or diameter) and
compressive strength at the maximum force) and to compute thickness. For typical specimen geometries, an instrument with
the effective modulus of the core. an accuracy of 612 µm [60.0005 in.] is desirable for thickness
5.2 This test method provides a standard method of obtain- measurement, whereas an instrument with an accuracy of
ing the flatwise compressive strength and modulus for sand- 6250 µm [60.010 in.] is acceptable for length and width (or
wich core structural design properties, material specifications, diameter) measurement.
research and development applications, and quality assurance. 7.2 Loading Platens—Force shall be introduced into the
5.3 In order to prevent local crushing at the edges of some specimen using one fixed flat platen and one spherical seat
honeycomb cores, it is often desirable to stabilize the edges (self-aligning) platen. The platens shall be well-aligned and
with a suitable material, such as a thin layer of resin or thin shall not apply eccentric forces. A satisfactory type of appara-
facings. Flatwise compressive strength data may be generated tus is shown in Figs. 1 and 2. The platen surfaces shall extend
using either stabilized specimens (reported as stabilized com-
pression 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.
5.4 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.

6. Interferences
6.1 Material and Specimen Preparation—Poor material
fabrication practices and damage induced by improper speci-
men machining are known causes of high data scatter in
composites and sandwich structures in general. A specific
material factor that affects sandwich cores is variability in core
density. Important aspects of sandwich core specimen prepa-
ration that contribute to data scatter include the existence of
joints, voids or other core discontinuities, out-of-plane curva-
ture, and surface roughness.
6.2 System Alignment—Non-uniform loading over the sur-
face of the test specimen may cause premature failure. Non-
uniform loading may result from non-uniform specimen thick-
ness, failure to locate the specimen concentrically in the
fixture, or system or fixture misalignment.
6.3 Geometry—Specific geometric factors that affect sand-
wich flatwise compressive strength include core cell geometry,
core thickness, and specimen shape (square or circular). FIG. 1 Platen, Transducer, and Rod Setup
--`,,```,,,,````-`-`,,`,,`,`,,`---

Copyright ASTM International 2

Copyright by ASTM Int'l (all rights reserved);
Reproduced by IHS under license with ASTM
No reproduction or networking permitted without license from IHS Not for Resale
Reproduction authorized per License Agreement with Kathe Hooper (ASTMIHS Account); Mon Oct 31 11:05:36 EST 2005
 C 365/C 365M – 05
2, has been found to work satisfactorily. In the example shown,
a small hole is drilled in the center of the core specimen and in
the bottom loading platen, and a transducer rod is inserted
through the hole, such that it contacts the upper loading platen.
NOTE 1—Bonded resistance strain gages are not usually considered
satisfactory for measuring strain in this application because of their
stiffness. The reinforcing effect of bonding gages to some cores can lead
to large errors in measurement of strain.
7.5 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.
7.6 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 gage section of the 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 condi-
tion 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
FIG. 2 Close-up of Specimen Between Loading Platens
Practice E 122. Report the method of sampling.
8.2 Geometry—Test specimens shall have a square or cir-
cular cross-section not exceeding 10 000 mm2 [16.0 in.2], and
beyond the test specimen periphery. If the platens are not shall be equal in thickness to the sandwich core thickness.
sufficiently hardened, or simply to protect the platen surfaces, Minimum specimen cross-sectional areas for various types of
a hardened plate (with parallel surfaces) can be inserted core materials are as follows:
between each end of the fixture and the corresponding platen. NOTE 2—The specimen’s cross-sectional area is defined in the facing
7.3 Testing Machine—The testing machine shall be in plane, in regard to the orientation that the core would be placed in a
accordance with Practices E 4 and shall satisfy the following structural sandwich construction. For example, for a honeycomb core the
requirements: cross-sectional area is defined in the plane of the cells, which is
7.3.1 Testing Machine Configuration—The testing machine perpendicular to the orientation of the cell walls.
shall have both an essentially stationary head and a movable 8.2.1 Continuous Bonding Surfaces (for example, Balsa
head. Wood, Foams)—The minimum facing area of the specimen
7.3.2 Drive Mechanism—The testing machine drive mecha- shall be 625 mm2 [1.0 in.2].
nism shall be capable of imparting to the movable head a 8.2.2 Discontinuous Cellular Bonding Surfaces (for ex-
controlled velocity with respect to the stationary head. The ample, Honeycomb)—The required facing area of the speci-
velocity of the movable head shall be capable of being men is dependent upon the cell size, to ensure a minimum --`,,```,,,,````-`-`,,`,,`,`,,`---

regulated in accordance with 11.5. number of cells are tested. Minimum facing areas are recom-
7.3.3 Force Indicator—The testing machine load-sensing mended in Table 1 for the more common cell sizes. These are
device shall be capable of indicating the total force being intended to provide approximately 60 cells minimum in the test
carried by the test specimen. This device shall be essentially specimen. The largest facing area listed in the table (5625
free from inertia lag at the specified rate of testing and shall mm2 [9.0 in.2]) is a practical maximum for this test method.
indicate the force with an accuracy over the force range(s) of
interest of within 61 % of the indicated value.
7.4 Crosshead Displacement Indicator—The testing ma- TABLE 1 Recommended Minimum Specimen Cross-Sectional
chine shall be capable of monitoring and recording the cross- Area
head displacement (stroke) with a precision of at least 61 %. Minimum Cell Size Maximum Cell Size Minimum Cross-Sectional
(mm [in.]) (mm [in.]) Area (mm2 [in.2])
If machine compliance is significant, it is acceptable to
measure the displacement of the movable head using an LVDT, ... 3.0 [0.125] 625 [1.0]
3.0 [0.125] 6.0 [0.250] 2500 [4.0]
compressometer, or similar device with 61 % precision on 6.0 [0.250] 9.0 [0.375] 5625 [9.0]
displacement. A transducer and rod setup, shown in Figs. 1 and

Copyright ASTM International 3

Copyright by ASTM Int'l (all rights reserved);
Reproduced by IHS under license with ASTM
No reproduction or networking permitted without license from IHS Not for Resale
Reproduction authorized per License Agreement with Kathe Hooper (ASTMIHS Account); Mon Oct 31 11:05:36 EST 2005
 C 365/C 365M – 05
Cores with cell sizes larger than 9 mm [0.375 in.] may require 11.1.3 The environmental conditioning test parameters.
a smaller number of cells to be tested in the specimen. 11.2 General Instructions:
8.3 Specimen Preparation and Machining—Prepare the test 11.2.1 Report any deviations from this test method, whether
specimens so that the loaded surfaces will be parallel to each intentional or inadvertent.
other and perpendicular to the sides of the specimen. Take 11.2.2 If core density is to be reported, then obtain these
precautions when cutting specimens from large sheets of core samples from the same sheet of core being tested. Density may
to avoid notches, undercuts, and rough or uneven surfaces due be evaluated in accordance with Test Method C 271.
to inappropriate machining methods. Obtain final dimensions
11.2.3 Following final specimen machining, but before
by water-lubricated precision sawing, milling, or grinding. The
conditioning and testing, measure the specimen length and
use of diamond tooling has been found to be extremely
width (or diameter) and thickness. The accuracy of these
effective for many material systems. Record and report the
measurements shall be within 1.0 % of the dimension. Measure
specimen cutting preparation method.
the specimen length and width (or diameter) with an accuracy
NOTE 3—In order to prevent local crushing at the edges of some of 6250 µm [60.010 in.]. Measure the specimen thickness
honeycomb cores, it is often desirable to reinforce the edges with a with an accuracy of 613 µm [60.0005 in.]. Record the
suitable material. In such instances, the edges may be dipped in a thin dimensions to three significant figures in units of millimetres
layer of resin, or thin facings may be bonded to the core. When either of
these stabilization techniques is used, the test shall be reported as a
[inches].
stabilized compression test, and the method, configuration, and process of 11.3 Condition the specimens as required. Store the speci-
stabilization utilized shall be reported. When honeycomb cell edges are mens in the conditioned environment until test time, if the test
not stabilized, the test shall be reported as a bare compression test. It is environment is different than the conditioning environment.
customary aerospace industry practice to determine compression modulus
11.4 Following final specimen conditioning, but before
only when using stabilized specimens.
NOTE 4—Testing of core materials with typical manufacturing thick- testing, re-measure the specimen length and width (or diam-
ness tolerances (60.08 to 60.13 mm [60.003 to 60.005 in.]) may eter) and thickness as in 11.2.3.
produce variant flatwise compressive modulus values, as this tolerance is 11.5 Speed of Testing—Set the speed of testing so as to
too large to preclude specimen seating effects within the specified produce failure within 3 to 6 min. If the ultimate strength of the
displacement range. Such effects are often characterized by the presence material cannot be reasonably estimated, initial trials should be
of toe regions in the force versus displacement data (see Annex Annex
conducted using standard speeds until the ultimate strength of
A1). To minimize the toe region and provide Hookean (linear) behavior in
the specified displacement range, it is recommended that the core be the material and the compliance of the system are known, and
produced or machined with a facing area thickness tolerance equal to speed of testing can be adjusted. The suggested standard head
60.05 % of the nominal core thickness (for example, 60.013 mm displacement rate is 0.50 mm/min [0.020 in./min].
[60.0005 in.] for 1.0 inch thick core). 11.6 Test Environment—If possible, test the specimen under
8.4 Labeling—Label the test specimens so that they will be the same fluid exposure level used for conditioning. However,
distinct from each other and traceable back to the sheet of cases such as elevated temperature testing of a moist specimen
origin, and will neither influence the test nor be affected by it. place unrealistic requirements on the capabilities of common
testing machine environmental chambers. In such cases, the
9. Calibration mechanical test environment may need to be modified, for
9.1 The accuracy of all measuring equipment shall have example, by testing at elevated temperature with no fluid
certified calibrations that are current at the time of use of the exposure control, but with a specified limit on time to failure
equipment. from withdrawal from the conditioning chamber. Record any
modifications to the test environment.
10. Conditioning 11.7 Specimen Installation—Mark a rectangle or circle
(depending upon the specimen’s cross-sectional shape) on the
10.1 Standard Conditioning Procedure—Unless a different
lower platen to help center the specimen between the platens.
environment is specified as part of the experiment, condition
Place the specimen on the lower platen, accommodating the
the test specimens in accordance with Procedure C of Test
LVDT or compressometer as necessary.
Method D 5229/D 5229M, and store and test at standard
laboratory atmosphere (23 6 3°C [73 6 5°F] and 50 6 5 % NOTE 6—Take care to align specimens well between the platens, in
relative humidity). order to distribute the applied force as uniformly as possible over the
entire loading surface. This will help to ensure that the specimen edges are
11. Procedure loaded uniformly. Non-uniform loading often results in failures that are
confined to one corner or one edge of the specimen.
11.1 Parameters to be Specified Before Test:
11.1.1 The specimen sampling method, specimen geometry, 11.8 Pre-loading—Move the actuator or crosshead such that
and conditioning travelers (if required). the loading platen contacts the LVDT/compressometer and
11.1.2 The properties and data reporting format desired. specimen, and apply a standard initial load of 45 N [10 lbf].
Zero and balance the LVDT or compressometer.
NOTE 5—Determine specific material property, accuracy, and data
reporting requirements prior to test for proper selection of instrumentation
11.9 Loading—Apply a compressive force to the specimen
and data recording equipment. Estimate the specimen strength to aid in at the specified rate while recording data. Load the specimen
transducer selection, calibration of equipment, and determination of until failure, or until the measured LVDT/compressometer
equipment settings. deflection equals 2 % of the initial core thickness.
--`,,```,,,,````-`-`,,`,,`,`,,`---

Copyright ASTM International 4

Copyright by ASTM Int'l (all rights reserved);
Reproduced by IHS under license with ASTM
No reproduction or networking permitted without license from IHS Not for Resale
Reproduction authorized per License Agreement with Kathe Hooper (ASTMIHS Account); Mon Oct 31 11:05:36 EST 2005
 C 365/C 365M – 05
11.10 Data Recording—Record force versus head displace- deflection range of 25 to 50 % of ultimate is recommended.
ment and force versus LVDT/compressometer deflection data However, for some other materials, another range may be more
continuously, or at frequent regular intervals; for this test appropriate. Other definitions of chord modulus may be evalu-
method, a sampling rate of 2 to 3 data recordings per second, ated and reported at the user’s discretion. If such data are
and a target minimum of 100 data points per test are recom- generated and reported, report also the definitions used, the
mended. If a compliance change or initial failures are noted, deflection range used, and the results to three significant
record the force, displacement, and mode of damage at such figures.
points. Record the maximum force, the failure force, the head NOTE 7—To account for seating effects related to specimen thickness
displacement and the LVDT/compressometer deflection at, or variance, toe: compensation may be made in accordance with Annex A1,
as near as possible to, the moment of failure. Also record the unless it is shown that the toe region of the curve is not due to the take-up
force and head displacement at 2 % deflection, if that deflection of slack, seating of the specimen, or other artifact, but rather is an
level is achieved prior to failure. authentic material response.
--`,,```,,,,````-`-`,,`,,`,`,,`---

11.11 Failure Modes—Uniform compressive failure of the

Ezfc 5 ~~P0.003 2 P0.001! · t!/~~d0.003 2 d0.001! · A! (3)
sandwich core is the only acceptable failure mode. Compres-
sive failures confined to one corner or edge of the specimen where:
shall be considered invalid. Ezfc = core flatwise compressive chord modulus, MPa
[psi],
12. Validation P0.003 = applied force corresponding to d0.003, N [lbf],
12.1 Values for ultimate properties shall not be calculated P0.001 = applied force corresponding to d0.001, N [lbf],
for any specimen that breaks at some obvious flaw, unless such d0.003 = recorded deflection value such that d/t is closest
flaw constitutes a variable being studied. Retests shall be to 0.003, and
performed for any specimen on which values are not calcu- d0.001 = recorded deflection value such that d/t is closest
lated. to 0.001.
12.2 A significant fraction of failures in a sample population 13.4 Statistics—For each series of tests calculate the aver-
occurring along one corner or one edge shall be cause to age value, standard deviation, and coefficient of variation (in
re-examine the means of force introduction into the specimen. percent) for ultimate flatwise compressive strength and modu-
Factors considered should include the loading platen align- lus:
ment, specimen surface characteristics, and uneven machining –x 5
n

of specimen surfaces and edges. ~ ( xi!/n (4)

i51

13. Calculation
13.1 Ultimate Strength—Calculate the ultimate flatwise
Sn21 Œ( ~
n

i51
xi2 2 –x2!/~n 2 1! (5)

compressive strength using Eq 1 and report the results to three CV 5 100 3 Sn21/x– (6)
significant figures.
where:
Fzfcu 5 Pmax / A (1) –x = sample mean (average),
where: Sn-1 = sample standard deviation,
Fzfcu = ultimate flatwise compressive strength, MPa [psi], CV = sample coefficient of variation, %,
Pmax = ultimate force prior to failure, N [lbf], and n = number of specimens, and
A = cross-sectional area, mm2 [in.2]. xi = measured or derived property.
13.2 2 % Deflection Stress—If 2 % deflection is achieved
prior to stopping the test, calculate the flatwise compressive 14. Report
stress at 2 % deflection using Eq 2 and report the results to 14.1 Report the following information, or references point-
three significant figures. ing to other documentation containing this information, to the
szfc0.02 5 P0.02 / A (2) maximum extent applicable (reporting of items beyond the
control of a given testing laboratory, such as might occur with
where: material details or panel fabrication parameters, shall be the
szfc0.02 = ultimate flatwise compressive strength, MPa responsibility of the requestor):
[psi],
P0.02 = applied force corresponding to d0.02, N [lbf], NOTE 8—Guides E 1309, E 1434 and E 1471 contain data reporting
recommendations for composite materials and composite materials me-
d0.02 = recorded deflection value such that d/t is closest
chanical testing.
to 0.02, and
t = measured thickness of core specimen prior to 14.1.1 The revision level or date of issue of this test method.
loading, mm [in.]. 14.1.2 The name(s) of the test operator(s).
13.3 Compressive Modulus—Calculate the flatwise com- 14.1.3 Any variations to this test method, anomalies noticed
pressive chord modulus using Eq 3 and report the results to during testing, or equipment problems occurring during testing.
three significant figures. The deflection values selected are 14.1.4 Identification of all the materials constituent to the
intended to represent the lower half of the core’s stress-strain sandwich core specimen tested (including stabilization materi-
curve. For core materials which fall bellow d/t = 0.006, a als if utilized), including for each: material specification,

Copyright ASTM International 5

Reproduced by IHS under license with ASTM Copyright by ASTM Int'l (all rights reserved);
No reproduction or networking permitted without license from IHS Not for Resale
Reproduction authorized per License Agreement with Kathe Hooper (ASTMIHS Account); Mon Oct 31 11:05:36 EST 2005
 C 365/C 365M – 05
material type, manufacturer’s material designation, manufac- 14.1.15 Weight of specimen.
turer’s batch or lot number, source (if not from manufacturer), 14.1.16 Conditioning parameters and results.
date of certification, and expiration of certification. 14.1.17 Relative humidity and temperature of the testing
14.1.5 Description of the fabrication steps used to prepare laboratory.
the sandwich core including: fabrication start date, fabrication 14.1.18 Environment of the test machine environmental
end date, process specification, and a description of the chamber (if used) and soak time at environment.
equipment used. 14.1.19 Number of specimens tested.
14.1.6 If requested, core density test method, specimen 14.1.20 Speed of testing.
sampling method and geometries, test parameters, and test 14.1.21 Individual ultimate flatwise compressive strengths
results. and average value, standard deviation, and coefficient of
14.1.7 Method of preparing the test specimen, including variation (in percent) for the population.
specimen labeling scheme and method, specimen geometry, 14.1.22 Individual ultimate flatwise compressive modulus
sampling method, and specimen cutting method. values and average value, standard deviation, and coefficient of
14.1.8 For honeycomb core specimens, method of stabiliz- variation (in percent) for the population.
ing the specimen (if performed), including material(s), process- 14.1.23 Force versus crosshead displacement data for each
ing cycle, specimen geometry after stabilization, and so forth. specimen so evaluated.
14.1.9 Results of any nondestructive evaluation tests. 14.1.24 Force versus recorded LVDT/compressometer de-
14.1.10 Calibration dates and methods for all measurements flection data for each specimen so evaluated.
and test equipment. 14.1.25 Failure mode, location of failure, and percentage of
14.1.11 Details of loading platens and apparatus, including failure area of core for each specimen.
dimensions and material(s) used. 15. Precision and Bias
14.1.12 Type of test machine, alignment results, and data 15.1 Precision—The data required for the development of a
acquisition sampling rate and equipment type. precision statement is not available for this test method.
14.1.13 Type, range, and sensitivity of LVDT or compres- 15.2 Bias—Bias cannot be determined for this method as no
someter, or any other instruments used to measure loading acceptable reference standards exist.
platen deflection.
14.1.14 Measured length and width (or diameter) and thick- 16. Keywords
ness for each specimen (prior to and after conditioning, if 16.1 compressive modulus; compressive strength; core; flat-
appropriate). wise compression; sandwich

ANNEX

(Mandatory Information)

A1. TOE COMPENSATION

A1.1 In a typical force versus displacement curve (see Fig.

--`,,```,,,,````-`-`,,`,,`,`,,`---
A1.1), there is a toe region, AC, that does not represent a
property of the material. It is an artifact caused by a take-up of
slack and alignment or seating of the specimen. In order to
obtain correct compressive modulus values, this artifact must
be compensated for to give the corrected zero point on the
displacement axis.
A1.2 For core materials exhibiting a region of Hookean
(linear) behavior (see Fig. Fig. A1.1), a continuation of the
linear (CD) region of the curve may be constructed through the
zero-force axis. This intersection (B) is the corrected zero
displacement point (d = 0.000) from which all displacements
must be measured.
A1.3 For core modulus measurement, it is preferable that
FIG. A1.1 Core Material with Hookean Region
the toe region fall below d0.001.

Copyright ASTM International 6

Copyright by ASTM Int'l (all rights reserved);
Reproduced by IHS under license with ASTM
No reproduction or networking permitted without license from IHS Not for Resale
Reproduction authorized per License Agreement with Kathe Hooper (ASTMIHS Account); Mon Oct 31 11:05:36 EST 2005
 C 365/C 365M – 05

ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned
in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk
of infringement of such rights, are entirely their own responsibility.

This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and
if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards
and should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the
responsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you should
make your views known to the ASTM Committee on Standards, at the address shown below.

This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,
United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the above
address or at 610-832-9585 (phone), 610-832-9555 (fax), or service@astm.org (e-mail); or through the ASTM website
(www.astm.org).
--`,,```,,,,````-`-`,,`,,`,`,,`---

Copyright ASTM International 7

Reproduced by IHS under license with ASTM Copyright by ASTM Int'l (all rights reserved);
No reproduction or networking permitted without license from IHS Not for Resale
Reproduction authorized per License Agreement with Kathe Hooper (ASTMIHS Account); Mon Oct 31 11:05:36 EST 2005