ASTM C480/C480M-16
(Test Method)Standard Test Method for Flexure Creep of Sandwich Constructions
Standard Test Method for Flexure Creep of Sandwich Constructions
SIGNIFICANCE AND USE
5.1 The determination of the creep rate provides information on the behavior of sandwich constructions under constant applied force. Creep is defined as deflection under constant force over a period of time beyond the initial deformation as a result of the application of the force. Deflection data obtained from this test method can be plotted against time, and a creep rate determined. By using standard specimen constructions and constant loading, the test method may also be used to evaluate creep behavior of sandwich panel core-to-facing adhesives.
5.2 This test method provides a standard method of obtaining flexure creep of sandwich constructions for quality control, acceptance specification testing, and research and development.
5.3 Factors that influence the sandwich construction creep response and shall therefore be reported include the following: facing material, core material, adhesive material, methods of material fabrication, facing stacking sequence and overall thickness, core geometry (cell size), core density, core thickness, adhesive thickness, specimen geometry, specimen preparation, specimen conditioning, environment of testing, specimen alignment, loading procedure, speed of testing, facing void content, adhesive void content, and facing volume percent reinforcement. Further, facing and core-to-facing strength and creep response may be different between precured/bonded and co-cured facesheets of the same material.
SCOPE
1.1 This test method covers the determination of the creep characteristics and creep rate of flat sandwich constructions loaded in flexure, at any desired temperature. 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 either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance 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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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.
Designation: C480/C480M − 16
Standard Test Method for
Flexure Creep of Sandwich Constructions
This standard is issued under the fixed designation C480/C480M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E122PracticeforCalculatingSampleSizetoEstimate,With
Specified Precision, the Average for a Characteristic of a
1.1 This test method covers the determination of the creep
Lot or Process
characteristics and creep rate of flat sandwich constructions
E177Practice for Use of the Terms Precision and Bias in
loaded in flexure, at any desired temperature. Permissible core
ASTM Test Methods
material forms include those with continuous bonding surfaces
E456Terminology Relating to Quality and Statistics
(such as balsa wood and foams) as well as those with
discontinuous bonding surfaces (such as honeycomb).
3. Terminology
1.2 The values stated in either SI units or inch-pound units
3.1 Definitions—Terminology D3878 defines terms relating
are to be regarded separately as standard. Within the text the
to high-modulus fibers and their composites, a well as terms
inch-pound units are shown in brackets. The values stated in
relating to sandwich constructions. Terminology D883 defines
eitherSIunitsorinch-poundunitsaretoberegardedseparately
terms relating to plastics. Terminology E6 defines terms
as standard.The values stated in each system may not be exact
relating to mechanical testing. Terminology E456 and Practice
equivalents;therefore,eachsystemshallbeusedindependently
E177 define terms relating to statistics. In the event of a
of the other. Combining values from the two systems may
conflict between terms, Terminology D3878 shall have prece-
result in non-conformance with the standard.
dence over the other terminology documents.
1.3 This standard does not purport to address all of the
3.2 Symbols:
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3.2.1 A—distance between pivot point and point of applied
priate safety and health practices and determine the applica- force on the specimen
bility of regulatory limitations prior to use.
3.2.2 b—specimen width
3.2.3 B—distancefrompivotpointtocenterofgravityofthe
2. Referenced Documents
loading arm
2.1 ASTM Standards:
3.2.4 c—core thickness
C393/C393MTest Method for Core Shear Properties of
Sandwich Constructions by Beam Flexure
3.2.5 CR —creep rate at time, i
I i
D883Terminology Relating to Plastics
3.2.6 d—sandwich total thickness
D3878Terminology for Composite Materials
D5229/D5229MTestMethodforMoistureAbsorptionProp-
3.2.7 d—initial static deflection under the same load and at
erties and Equilibrium Conditioning of Polymer Matrix
the same temperature
Composite Materials
3.2.8 D—total deflection at time, t
D7249/D7249MTestMethodforFacingPropertiesofSand-
3.2.9 F—applied facing stress
wich Constructions by Long Beam Flexure
f
E6Terminology Relating to Methods of Mechanical Testing
3.2.10 F —applied core shear stress
s
3.2.11 M—distance between point and weight point
This specification is under the jurisdiction of ASTM Committee D30 on
3.2.12 n—number of specimens
Composite Materials and is the direct responsibility of Subcommittee D30.09 on
3.2.13 p—mass of loading plate and rod
Sandwich Construction.
Current edition approved April 1, 2016. Published April 2016. Originally
3.2.14 P—applied force
approved in 1961. Last previous edition approved in 2015 as C480/
C480M–08(2015). DOI: 10.1520/C0480_C0480M-16.
3.2.15 S—length of support span
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
3.2.16 w—mass of lever arm
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 3.2.17 W—mass of weight (including tray mass)
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C480/C480M − 16
4. Summary of Test Method for thickness measurement, and an accuracy of 6250 µm
[60.010 in.] for length and width measurements.
4.1 This test method consists of subjecting a beam of
NOTE 1—The accuracies given above are based on achieving measure-
sandwich construction to a sustained force normal to the plane
ments that are within1%ofthe sample length, width and thickness.
of the sandwich, using either a 3-point or a 4-point loading
7.2 Loading Fixtures—The fixture for loading the specimen
fixture. Deflection versus time measurements are recorded.
shall be a 3-point loading configuration that conforms to either
4.2 For long beam specimens conforming to Test Method
Test Method D7249/D7249M (for a long beam test) or to Test
D7249/D7249M, the only acceptable failure modes for sand-
Method C393/C393M (for a short beam test) except that a
wich facesheet strength are those which are internal to one of
constantforceshallbeappliedbymeansofweightsandalever
the facesheets. Failure of the sandwich core or the core-to-
system.Fig.1showsaleverandweight-loadingapparatusthat
facesheetbondprecedingfailureofoneofthefacesheetsisnot
has been found satisfactory.
an acceptable failure mode for this specimen configuration.
7.3 Deflectometer (LVDT)—The deflection of the specimen
4.3 For short-beam specimens conforming to Test Method
shall be measured in the center of the support span by a
C393/C393M,theonlyacceptablefailuremodesarecoreshear
properly calibrated device having an accuracy of 60.025 mm
or core-to-facing bond. Failure of the sandwich facing preced-
[60.001 in.] or better.
ing failure of the core or core-to-facing bond is not an
7.4 Conditioning Chamber—When conditioning materials
acceptable failure mode for this specimen configuration.
at non-laboratory environments, a temperature/vapor-level
4.4 Careful post-test inspection of the specimen is required
controlledenvironmentalconditioningchamberisrequiredthat
as facing failure occurring in proximity to the loading points
shall be capable of maintaining the required temperature to
canbecausedbylocalthrough-thicknesscompressionorshear
within 63°C [65°F] and the required relative humidity level
failure of the core that precedes failure of the facing.
to within 63 %. Chamber conditions shall be monitored either
on an automated continuous basis or on a manual basis at
5. Significance and Use
regular intervals (a minimum of once daily checks are recom-
5.1 The determination of the creep rate provides informa- mended).
tion on the behavior of sandwich constructions under constant
7.5 Environmental Test Chamber—An environmental test
applied force. Creep is defined as deflection under constant
chamber is required for test environments other than ambient
force over a period of time beyond the initial deformation as a
testing laboratory conditions.This chamber shall be capable of
result of the application of the force. Deflection data obtained
maintaining the gage section of the test specimen at the
from this test method can be plotted against time, and a creep
required test environment during the mechanical test.
ratedetermined.Byusingstandardspecimenconstructionsand
constant loading, the test method may also be used to evaluate
8. Sampling and Test Specimens
creep behavior of sandwich panel core-to-facing adhesives.
8.1 Sampling—Test at least five specimens per test condi-
5.2 This test method provides a standard method of obtain-
tionunlessvalidresultscanbegainedthroughtheuseoffewer
ingflexurecreepofsandwichconstructionsforqualitycontrol,
specimens, as in the case of a designed experiment. For
acceptance specification testing, and research and develop-
statistically significant data, consult the procedures outlined in
ment.
Practice E122. Report the method of sampling.
5.3 Factors that influence the sandwich construction creep
8.2 Geometry, Facing, Core:
response and shall therefore be reported include the following:
8.2.1 Core or Core-to-Facing Failure Mode Desired—The
facing material, core material, adhesive material, methods of
testspecimenconfigurationshallbeasandwichconstructionof
material fabrication, facing stacking sequence and overall
a size and proportions conforming to the flexure test specimen
thickness, core geometry (cell size), core density, core
described in Test Method C393/C393M. The standard speci-
thickness, adhesive thickness, specimen geometry, specimen
men configuration should be used whenever the specimen
preparation, specimen conditioning, environment of testing,
designequationsinSection8.2.3ofC393/C393Mindicatethat
specimen alignment, loading procedure, speed of testing,
facing void content, adhesive void content, and facing volume
percent reinforcement. Further, facing and core-to-facing
strength and creep response may be different between
precured/bondedandco-curedfacesheetsofthesamematerial.
6. Interferences
6.1 The interferences listed in Test Methods C393/C393M
and D7249/D7249M are also applicable to this test method.
7. Apparatus
7.1 Micrometers and Calipers—Amicrometer having a flat
anvil interface, or a caliper of suitable size, shall be used. The
instruments(s) shall have an accuracy of 625 µm [60.001 in.] FIG. 1 Creep Test Apparatus and Loading System
C480/C480M − 16
acoreofcore-to-facingbondfailuremodeisexpected.Incases 11. Procedure
where the standard C393/C393M specimen configuration will
11.1 Parameters to Be Specified Before Test:
notproduceadesiredfailure,anon-standardspecimenshallbe
11.1.1 The specimen sampling method, specimen geometry,
designed to produce a core or bond failure mode.
and conditioning travelers (if required).
8.2.2 Facesheet Failure Mode Desired—The test specimen
11.1.2 Theloadingfixturesupportspan(andloadingspanif
configuration shall be a sandwich construction of a size and
a 4-point loading configuration is used).
proportions conforming to the flexure test specimen described
11.1.3 The force, P, to be applied to the specimen and the
in Test Method D7249/D7249M.Anon-standard 3-point load-
maximum time for the test.
ing specimen configuration shall be designed per Section 8.2.3
11.1.4 The properties and data reporting format desired.
of D7249/D7249M to achieve a facing failure mode. The
standard 4-point loading D7249/D7249M specimen configura- 11.1.5 The environmental conditioning test parameters.
tion may be used if a suitable creep loading apparatus is used.
11.1.6 The nominal thicknesses of the facing materials.
8.3 Compression Side Facing—Unless otherwise specified
NOTE 3—Determine specific material property, accuracy, and data
by the test requestor, the bag-side facing of a co-cured reportingrequirementspriortotestforproperselectionofinstrumentation
and data recording equipment. Estimate the maximum specimen deflec-
composite sandwich panel shall be placed as the upper,
tion to aid in transducer selection, calibration of equipment, and determi-
compression-loaded facing during test, as facing compression
nation of equipment settings.
strength is more sensitive to imperfections typical of bag-side
11.2 General Instructions:
surfaces (for example, intra-cell dimpling) than is facing
tensionstrength.Creepresponseisexpectedtofollowthesame 11.2.1 Reportanydeviationsfromthistestmethod,whether
trends as static strength.
intentional or inadvertent.
11.2.2 Conditionthespecimensasrequired.Storethespeci-
8.4 Specimen Preparation and Machining—Specimen
mens in the conditioned environment until test time, if the test
preparation is extremely important for this test method. Take
environment is different than the conditioning environment.
precautionswhencuttingspecimensfromlargepanelstoavoid
11.2.3 Before testing, measure and record the specimen
notches,undercuts,roughorunevensurfaces,ordelaminations
length, width and thickness at three places in the test section.
due to inappropriate machining methods. Obtain final dimen-
Measure the specimen length and width with an accuracy of
sions by water-lubricated precision sawing, milling, or grind-
6250 µm [60.010 in.]. Measure the specimen thickness with
ing. The use of diamond coated machining tools has been
anaccuracyof 625µm[60.001in.].Recordthedimensionsto
found to be extremely effective for many material systems.
three significant figures in units of millimeters [inches].
Edges should be flat and parallel within the specified toler-
ances. Record and report the specimen cutting preparation
11.3 Measure and record the length of the support and
method.
loading spans.
8.5 Labeling—Label the test specimens so that they will be
11.4 The weight required to apply the specified force to the
distinct from each other and traceable back to the panel of
specimen by the 3-point loading lever system shown in Fig. 1
origin, and will neither influence the test nor be affected by it.
may be calculated as follows:
P 2 p A 2 wB
~ !
9. Calibration
W 5 (1)
M
9.1 The accuracy of all measuring equipment shall have
where:
certified calibrations that are current at the time of use of the
W = mass of weight (including tray mass), N [lb],
equipment
P = force applied to specimen, N [lb],
p = mass of loading plate and rod, N [lb],
10. Conditioning
w = mass of lever arm, N [lb],
10.1 The recommended pre-test specimen condition is ef-
A = distance between pivot point and point of applied force
fective moisture equilibrium at a specific relative humidity per
on the specimen, mm [in.].
D5229/D5229M; however, if the test requestor does not B = distance from pivot point to center of gravity of the
explicitly specify a pre-test conditioning environment, condi- loading arm, mm [in.], and
tioning is not required and the test specimens may be tested as M = distance between pivot point and weight point, mm,
prepared.
11.5 Test Environment—If possible, test the specimen under
10.2 The pre-test specimen conditioning process, to include the same fluid exposure level used for conditioning. However,
specifiedenvironmentalexposurelevelsandresultingmoisture cases such as elevated temperature testing of a moist specimen
content, shall be reported with the test data. place unrealistic requirements on the capabilities of common
NOTE 2—The term moisture, as used in Test Method D5229/D5229M, testing machine environmental chambers. In such cases, the
includes not only the vapor of a liquid and its condensate, but the liquid
mechanical test environment may need to be modified, for
itself in large quantities, as for i
...
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: C480/C480M − 08 (Reapproved 2015) C480/C480M − 16
Standard Test Method for
Flexure Creep of Sandwich Constructions
This standard is issued under the fixed designation C480/C480M; 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 determination of the creep characteristics and creep rate of flat sandwich constructions loaded
in flexure, at any desired temperature. 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 either SI units or inch-pound units are to be regarded separately as
standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of
the other. Combining values from the two systems may result in non-conformance 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)
C393/C393M Test Method for Core Shear Properties of Sandwich Constructions by Beam Flexure
D883 Terminology Relating to Plastics
D3878 Terminology for Composite Materials
D5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite
Materials
D7249/D7249M Test Method for Facing Properties of Sandwich Constructions by Long Beam Flexure
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
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)
3. Terminology
3.1 Definitions—Terminology D3878 defines terms relating to high-modulus fibers and their composites.
Terminologycomposites, a C274 defineswell as terms relating to structural sandwich constructions. Terminology D883 defines
terms relating to plastics. Terminology E6 defines terms relating to mechanical testing. Terminology 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
terminology documents.
3.2 Symbols:
3.2.1 A—distance between pivot point and point of applied force on the specimen
This specification 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 July 1, 2015April 1, 2016. Published August 2015 April 2016. Originally approved in 1961. Last previous edition approved in 20082015 as
C480/C480M – 08.C480/C480M – 08(2015). DOI: 10.1520/C0480_C0480M-08R15.10.1520/C0480_C0480M-16.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 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 the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C480/C480M − 16
3.2.2 b—specimen width
3.2.3 B—distance from pivot point to center of gravity of the loading arm
3.2.4 c—core thickness
3.2.5 CR —creep rate at time, i
I i
3.2.6 d—sandwich total thickness
3.2.7 d—initial static deflection under the same load and at the same temperature
3.2.8 D—total deflection at time, t
3.2.9 F —applied facing stress
f
3.2.10 F —applied core shear stress
s
3.2.11 M—distance between point and weight point
3.2.12 n—number of specimens
3.2.13 p—mass of loading plate and rod
3.2.14 P—applied force
3.2.15 S—length of support span
3.2.16 w—mass of lever arm
3.2.17 W—mass of weight (including tray mass)
4. Summary of Test Method
4.1 This test method consists of subjecting a beam of sandwich construction to a sustained force normal to the plane of the
sandwich, using either a 3-point or a 4-point loading fixture. Deflection versus time measurements are recorded.
4.2 For long beam specimens conforming to Test Method D7249/D7249M, the only acceptable failure modes for sandwich
facesheet strength are those which are internal to one of the facesheets. Failure of the sandwich core or the core-to-facesheet bond
preceding failure of one of the facesheets is not an acceptable failure mode for this specimen configuration.
4.3 For short-beam specimens conforming to Test Method C393/C393M, the only acceptable failure modes are core shear or
core-to-facing bond. Failure of the sandwich facing preceding failure of the core or core-to-facing bond is not an acceptable failure
mode for this specimen configuration.
4.4 Careful post-test inspection of the specimen is required as facing failure occurring in proximity to the loading points can
be caused by local through-thickness compression or shear failure of the core that precedes failure of the facing.
5. Significance and Use
5.1 The determination of the creep rate provides information on the behavior of sandwich constructions under constant applied
force. Creep is defined as deflection under constant force over a period of time beyond the initial deformation as a result of the
application of the force. Deflection data obtained from this test method can be plotted against time, and a creep rate determined.
By using standard specimen constructions and constant loading, the test method may also be used to evaluate creep behavior of
sandwich panel core-to-facing adhesives.
5.2 This test method provides a standard method of obtaining flexure creep of sandwich constructions for quality control,
acceptance specification testing, and research and development.
5.3 Factors that influence the sandwich construction creep response and shall therefore be reported include the following: facing
material, core material, adhesive material, methods of material fabrication, facing stacking sequence and overall thickness, core
geometry (cell size), core density, core thickness, adhesive thickness, specimen geometry, specimen preparation, specimen
conditioning, environment of testing, specimen alignment, loading procedure, speed of testing, facing void content, adhesive void
content, and facing volume percent reinforcement. Further, facing and core-to-facing strength and creep response may be different
between precured/bonded and co-cured facesheets of the same material.
6. Interferences
6.1 The interferences listed in Test Methods C393/C393M and D7249/D7249M are also applicable to this test method.
7. Apparatus
7.1 Micrometers and Calipers—A micrometer having a flat anvil interface, or a caliper of suitable size, shall be used. The
instruments(s) shall have an accuracy of 625 μm [60.001 in.] for thickness measurement, and an accuracy of 6250 μm [60.010
in.] for length and width measurements.
NOTE 1—The accuracies given above are based on achieving measurements that are within 1 % of the sample length, width and thickness.
C480/C480M − 16
7.2 Loading Fixtures—The fixture for loading the specimen shall be a 3-point loading configuration that conforms to either Test
Method D7249/D7249M (for a long beam test) or to Test Method C393/C393M (for a short beam test) except that a constant force
shall be applied by means of weights and a lever system. Fig. 1 shows a lever and weight-loading apparatus that has been found
satisfactory.
7.3 Deflectometer (LVDT)—The deflection of the specimen shall be measured in the center of the support span by a properly
calibrated device having an accuracy of 60.025 mm [60.001 in.] or better.
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 (a minimum of once daily checks are recommended).
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 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 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, Facing, Core:
8.2.1 Core or Core-to-Facing Failure Mode Desired—The test specimen configuration shall be a sandwich construction of a size
and proportions conforming to the flexure test specimen described in Test Method C393/C393M. The standard specimen
configuration should be used whenever the specimen design equations in Section 8.2.3 of C393/C393M indicate that a core of
core-to-facing bond failure mode is expected. In cases where the standard C393/C393M specimen configuration will not produce
a desired failure, a non-standard specimen shall be designed to produce a core or bond failure mode.
8.2.2 Facesheet Failure Mode Desired—The test specimen configuration shall be a sandwich construction of a size and
proportions conforming to the flexure test specimen described in Test Method D7249/D7249M. A non-standard 3-point loading
specimen configuration shall be designed per Section 8.2.3 of D7249/D7249M to achieve a facing failure mode. The standard
4-point loading D7249/D7249M specimen configuration may be used if a suitable creep loading apparatus is used.
8.3 Compression Side Facing—Unless otherwise specified by the test requestor, the bag-side facing of a co-cured composite
sandwich panel shall be placed as the upper, compression-loaded facing during test, as facing compression strength is more
sensitive to imperfections typical of bag-side surfaces (for example, intra-cell dimpling) than is facing tension strength. Creep
response is expected to follow the same trends as static strength.
8.4 Specimen Preparation and Machining—Specimen preparation is extremely important for this test method. Take precautions
when cutting specimens from large panels to avoid notches, undercuts, rough or uneven surfaces, or delaminations due to
inappropriate machining methods. Obtain final dimensions by water-lubricated precision sawing, milling, or grinding. The use of
diamond coated machining tools has been found to be extremely effective for many material systems. Edges should be flat and
parallel within the specified tolerances. Record and report the specimen cutting preparation method.
8.5 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
FIG. 1 Creep Test Apparatus and Loading System
C480/C480M − 16
10. Conditioning
10.1 The recommended pre-test specimen condition is effective moisture equilibrium at a specific relative humidity per
D5229/D5229M; however, if the test requestor does not explicitly specify a pre-test conditioning environment, conditioning is not
required and the test specimens may be tested as prepared.
10.2 The pre-test specimen conditioning process, to include specified environmental exposure levels and resulting moisture
content, shall be reported with the test data.
NOTE 2—The term moisture, as used in Test Method D5229/D5229M, includes not only the vapor of a liquid and its condensate, but the liquid itself
in large quantities, as for immersion.
10.3 If no explicit conditioning process is performed, the specimen conditioning process shall be reported as “unconditioned”
and the moisture content as “unknown”.
11. Procedure
11.1 Parameters to Be Specified Before Test:
11.1.1 The specimen sampling method, specimen geometry, and conditioning travelers (if required).
11.1.2 The loading fixture support span (and loading span if a 4-point loading configuration is used).
11.1.3 The force, P, to be applied to the specimen and the maximum time for the test.
11.1.4 The properties and data reporting format desired.
11.1.5 The environmental conditioning test parameters.
11.1.6 The nominal thicknesses of the facing materials.
NOTE 3—Determine specific material property, accuracy, and data reporting requirements prior to test for proper selection of instrumentation and data
recording equipment. Estimate the maximum specimen deflection to aid in transducer selection, calibration of equipment, and determination of equipment
settings.
11.2 General Instructions:
11.2.1 Report any deviations from this test method, whether intentional or inadvertent.
11.2.2 Condition the specimens as required. Store the specimens in the conditioned environment until test time, if the test
environment is different than the conditioning environment.
11.2.3 Before testing, measure and record the specimen length, width and thickness at three places in the test section. Measure
the specimen length and width with an accuracy of 6250 μm [60.010 in.]. Measure the specimen thickness with an accuracy of
625 μm [60.001 in.]. Record the dimensions to three significant figure
...
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Designation: C480/C480M − 16
Standard Test Method for
Flexure Creep of Sandwich Constructions
This standard is issued under the fixed designation C480/C480M; 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 E122 Practice for Calculating Sample Size to Estimate, With
Specified Precision, the Average for a Characteristic of a
1.1 This test method covers the determination of the creep
Lot or Process
characteristics and creep rate of flat sandwich constructions
E177 Practice for Use of the Terms Precision and Bias in
loaded in flexure, at any desired temperature. Permissible core
ASTM Test Methods
material forms include those with continuous bonding surfaces
E456 Terminology Relating to Quality and Statistics
(such as balsa wood and foams) as well as those with
discontinuous bonding surfaces (such as honeycomb).
3. Terminology
1.2 The values stated in either SI units or inch-pound units
3.1 Definitions—Terminology D3878 defines terms relating
are to be regarded separately as standard. Within the text the
to high-modulus fibers and their composites, a well as terms
inch-pound units are shown in brackets. The values stated in
relating to sandwich constructions. Terminology D883 defines
either SI units or inch-pound units are to be regarded separately
terms relating to plastics. Terminology E6 defines terms
as standard. The values stated in each system may not be exact
relating to mechanical testing. Terminology E456 and Practice
equivalents; therefore, each system shall be used independently
E177 define terms relating to statistics. In the event of a
of the other. Combining values from the two systems may
conflict between terms, Terminology D3878 shall have prece-
result in non-conformance with the standard.
dence over the other terminology documents.
1.3 This standard does not purport to address all of the
3.2 Symbols:
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 3.2.1 A—distance between pivot point and point of applied
priate safety and health practices and determine the applica-
force on the specimen
bility of regulatory limitations prior to use.
3.2.2 b—specimen width
3.2.3 B—distance from pivot point to center of gravity of the
2. Referenced Documents
loading arm
2.1 ASTM Standards:
3.2.4 c—core thickness
C393/C393M Test Method for Core Shear Properties of
Sandwich Constructions by Beam Flexure
3.2.5 CR —creep rate at time, i
I i
D883 Terminology Relating to Plastics
3.2.6 d—sandwich total thickness
D3878 Terminology for Composite Materials
D5229/D5229M Test Method for Moisture Absorption Prop-
3.2.7 d—initial static deflection under the same load and at
erties and Equilibrium Conditioning of Polymer Matrix
the same temperature
Composite Materials
3.2.8 D—total deflection at time, t
D7249/D7249M Test Method for Facing Properties of Sand-
3.2.9 F —applied facing stress
wich Constructions by Long Beam Flexure
f
E6 Terminology Relating to Methods of Mechanical Testing
3.2.10 F —applied core shear stress
s
3.2.11 M—distance between point and weight point
This specification is under the jurisdiction of ASTM Committee D30 on 3.2.12 n—number of specimens
Composite Materials and is the direct responsibility of Subcommittee D30.09 on
3.2.13 p—mass of loading plate and rod
Sandwich Construction.
Current edition approved April 1, 2016. Published April 2016. Originally
3.2.14 P—applied force
approved in 1961. Last previous edition approved in 2015 as C480/
C480M – 08(2015). DOI: 10.1520/C0480_C0480M-16.
3.2.15 S—length of support span
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
3.2.16 w—mass of lever arm
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 3.2.17 W—mass of weight (including tray mass)
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C480/C480M − 16
4. Summary of Test Method for thickness measurement, and an accuracy of 6250 µm
[60.010 in.] for length and width measurements.
4.1 This test method consists of subjecting a beam of
NOTE 1—The accuracies given above are based on achieving measure-
sandwich construction to a sustained force normal to the plane
ments that are within 1 % of the sample length, width and thickness.
of the sandwich, using either a 3-point or a 4-point loading
7.2 Loading Fixtures—The fixture for loading the specimen
fixture. Deflection versus time measurements are recorded.
shall be a 3-point loading configuration that conforms to either
4.2 For long beam specimens conforming to Test Method
Test Method D7249/D7249M (for a long beam test) or to Test
D7249/D7249M, the only acceptable failure modes for sand-
Method C393/C393M (for a short beam test) except that a
wich facesheet strength are those which are internal to one of
constant force shall be applied by means of weights and a lever
the facesheets. Failure of the sandwich core or the core-to-
system. Fig. 1 shows a lever and weight-loading apparatus that
facesheet bond preceding failure of one of the facesheets is not
has been found satisfactory.
an acceptable failure mode for this specimen configuration.
7.3 Deflectometer (LVDT)—The deflection of the specimen
4.3 For short-beam specimens conforming to Test Method
shall be measured in the center of the support span by a
C393/C393M, the only acceptable failure modes are core shear
properly calibrated device having an accuracy of 60.025 mm
or core-to-facing bond. Failure of the sandwich facing preced-
[60.001 in.] or better.
ing failure of the core or core-to-facing bond is not an
7.4 Conditioning Chamber—When conditioning materials
acceptable failure mode for this specimen configuration.
at non-laboratory environments, a temperature/vapor-level
4.4 Careful post-test inspection of the specimen is required
controlled environmental conditioning chamber is required that
as facing failure occurring in proximity to the loading points
shall be capable of maintaining the required temperature to
can be caused by local through-thickness compression or shear
within 63°C [65°F] and the required relative humidity level
failure of the core that precedes failure of the facing.
to within 63 %. Chamber conditions shall be monitored either
on an automated continuous basis or on a manual basis at
5. Significance and Use
regular intervals (a minimum of once daily checks are recom-
5.1 The determination of the creep rate provides informa-
mended).
tion on the behavior of sandwich constructions under constant
7.5 Environmental Test Chamber—An environmental test
applied force. Creep is defined as deflection under constant
chamber is required for test environments other than ambient
force over a period of time beyond the initial deformation as a
testing laboratory conditions. This chamber shall be capable of
result of the application of the force. Deflection data obtained
maintaining the gage section of the test specimen at the
from this test method can be plotted against time, and a creep
required test environment during the mechanical test.
rate determined. By using standard specimen constructions and
constant loading, the test method may also be used to evaluate
8. Sampling and Test Specimens
creep behavior of sandwich panel core-to-facing adhesives.
8.1 Sampling—Test at least five specimens per test condi-
5.2 This test method provides a standard method of obtain-
tion unless valid results can be gained through the use of fewer
ing flexure creep of sandwich constructions for quality control,
specimens, as in the case of a designed experiment. For
acceptance specification testing, and research and develop-
statistically significant data, consult the procedures outlined in
ment.
Practice E122. Report the method of sampling.
5.3 Factors that influence the sandwich construction creep
8.2 Geometry, Facing, Core:
response and shall therefore be reported include the following:
8.2.1 Core or Core-to-Facing Failure Mode Desired—The
facing material, core material, adhesive material, methods of
test specimen configuration shall be a sandwich construction of
material fabrication, facing stacking sequence and overall
a size and proportions conforming to the flexure test specimen
thickness, core geometry (cell size), core density, core
described in Test Method C393/C393M. The standard speci-
thickness, adhesive thickness, specimen geometry, specimen
men configuration should be used whenever the specimen
preparation, specimen conditioning, environment of testing,
design equations in Section 8.2.3 of C393/C393M indicate that
specimen alignment, loading procedure, speed of testing,
facing void content, adhesive void content, and facing volume
percent reinforcement. Further, facing and core-to-facing
strength and creep response may be different between
precured/bonded and co-cured facesheets of the same material.
6. Interferences
6.1 The interferences listed in Test Methods C393/C393M
and D7249/D7249M are also applicable to this test method.
7. Apparatus
7.1 Micrometers and Calipers—A micrometer having a flat
anvil interface, or a caliper of suitable size, shall be used. The
instruments(s) shall have an accuracy of 625 µm [60.001 in.] FIG. 1 Creep Test Apparatus and Loading System
C480/C480M − 16
a core of core-to-facing bond failure mode is expected. In cases 11. Procedure
where the standard C393/C393M specimen configuration will
11.1 Parameters to Be Specified Before Test:
not produce a desired failure, a non-standard specimen shall be
11.1.1 The specimen sampling method, specimen geometry,
designed to produce a core or bond failure mode.
and conditioning travelers (if required).
8.2.2 Facesheet Failure Mode Desired—The test specimen
11.1.2 The loading fixture support span (and loading span if
configuration shall be a sandwich construction of a size and
a 4-point loading configuration is used).
proportions conforming to the flexure test specimen described
11.1.3 The force, P, to be applied to the specimen and the
in Test Method D7249/D7249M. A non-standard 3-point load-
maximum time for the test.
ing specimen configuration shall be designed per Section 8.2.3
11.1.4 The properties and data reporting format desired.
of D7249/D7249M to achieve a facing failure mode. The
11.1.5 The environmental conditioning test parameters.
standard 4-point loading D7249/D7249M specimen configura-
tion may be used if a suitable creep loading apparatus is used.
11.1.6 The nominal thicknesses of the facing materials.
8.3 Compression Side Facing—Unless otherwise specified
NOTE 3—Determine specific material property, accuracy, and data
by the test requestor, the bag-side facing of a co-cured
reporting requirements prior to test for proper selection of instrumentation
and data recording equipment. Estimate the maximum specimen deflec-
composite sandwich panel shall be placed as the upper,
tion to aid in transducer selection, calibration of equipment, and determi-
compression-loaded facing during test, as facing compression
nation of equipment settings.
strength is more sensitive to imperfections typical of bag-side
11.2 General Instructions:
surfaces (for example, intra-cell dimpling) than is facing
tension strength. Creep response is expected to follow the same
11.2.1 Report any deviations from this test method, whether
trends as static strength. intentional or inadvertent.
11.2.2 Condition the specimens as required. Store the speci-
8.4 Specimen Preparation and Machining—Specimen
mens in the conditioned environment until test time, if the test
preparation is extremely important for this test method. Take
environment is different than the conditioning environment.
precautions when cutting specimens from large panels to avoid
11.2.3 Before testing, measure and record the specimen
notches, undercuts, rough or uneven surfaces, or delaminations
length, width and thickness at three places in the test section.
due to inappropriate machining methods. Obtain final dimen-
Measure the specimen length and width with an accuracy of
sions by water-lubricated precision sawing, milling, or grind-
6250 µm [60.010 in.]. Measure the specimen thickness with
ing. The use of diamond coated machining tools has been
an accuracy of 625 µm [60.001 in.]. Record the dimensions to
found to be extremely effective for many material systems.
three significant figures in units of millimeters [inches].
Edges should be flat and parallel within the specified toler-
ances. Record and report the specimen cutting preparation
11.3 Measure and record the length of the support and
method.
loading spans.
8.5 Labeling—Label the test specimens so that they will be
11.4 The weight required to apply the specified force to the
distinct from each other and traceable back to the panel of
specimen by the 3-point loading lever system shown in Fig. 1
origin, and will neither influence the test nor be affected by it.
may be calculated as follows:
~P 2 p! A 2 wB
9. Calibration
W 5 (1)
M
9.1 The accuracy of all measuring equipment shall have
where:
certified calibrations that are current at the time of use of the
W = mass of weight (including tray mass), N [lb],
equipment
P = force applied to specimen, N [lb],
p = mass of loading plate and rod, N [lb],
10. Conditioning
w = mass of lever arm, N [lb],
10.1 The recommended pre-test specimen condition is ef-
A = distance between pivot point and point of applied force
fective moisture equilibrium at a specific relative humidity per
on the specimen, mm [in.].
D5229/D5229M; however, if the test requestor does not B = distance from pivot point to center of gravity of the
explicitly specify a pre-test conditioning environment, condi- loading arm, mm [in.], and
M = distance between pivot point and weight point, mm,
tioning is not required and the test specimens may be tested as
prepared.
11.5 Test Environment—If possible, test the specimen under
10.2 The pre-test specimen conditioning process, to include the same fluid exposure level used for conditioning. However,
specified environmental exposure levels and resulting moisture cases such as elevated temperature testing of a moist specimen
content, shall be reported with the test data. place unrealistic requirements on the capabilities of common
NOTE 2—The term moisture, as used in Test Method D5229/D5229M, testing machine environmental chambers. In such cases, the
includes not
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