ASTM D7249/D7249M-16
(Test Method)Standard Test Method for Facing Properties of Sandwich Constructions by Long Beam Flexure
Standard Test Method for Facing Properties of Sandwich Constructions by Long Beam Flexure
SIGNIFICANCE AND USE
5.1 Flexure tests on flat sandwich construction may be conducted to determine the sandwich flexural stiffness, the core shear strength, and shear modulus, or the facings’ compressive and tensile strengths. Tests to evaluate core shear strength may also be used to evaluate core-to-facing bonds.
5.2 This test method is limited to obtaining the strength and stiffness of the sandwich panel facings, and to obtaining load-deflection data for use in calculating sandwich beam flexural and shear stiffness using Standard Practice D7250/D7250M. Due to the curvature of the flexural test specimen when loaded, facesheet compression strength from this test may not be equivalent to the facesheet compression strength of sandwich structures subjected to pure edgewise (in-plane) compression.
5.3 Core shear strength and shear modulus are best determined in accordance with Test Method C273 provided bare core material is available. Test Method C393 may also be used to determine core shear strength. Standard Practice D7250/D7250M may be used to calculate the flexural and shear stiffness of sandwich beams.
5.4 This test method can be used to produce facing strength data for structural design allowables, material specifications, and research and development applications; it may also be used as a quality control test for bonded sandwich panels.
5.5 Factors that influence the facing strength 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, 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 strength may be different between precured/bonded and co-cured facesheets of the same material.
Note 2: ...
SCOPE
1.1 This test method covers determination of facing properties of flat sandwich constructions subjected to flexure in such a manner that the applied moments produce curvature of the sandwich facing planes and result in compressive and tensile forces in the facings. 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. 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.
1.2.1 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 and health practices and determine the applicability of regulatory limitations prior to use.
Note 1: Alternate procedures for determining the compressive strength of unidirectional polymer matrix composites materials in a sandwich beam configuration may be found in Test Method D5467/D5467M.
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Designation: D7249/D7249M − 16
Standard Test Method for
Facing Properties of Sandwich Constructions by Long
1
Beam Flexure
This standard is issued under the fixed designation D7249/D7249M; 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 D5229/D5229MTestMethodforMoistureAbsorptionProp-
erties and Equilibrium Conditioning of Polymer Matrix
1.1 This test method covers determination of facing prop-
Composite Materials
erties of flat sandwich constructions subjected to flexure in
D5467/D5467MTest Method for Compressive Properties of
such a manner that the applied moments produce curvature of
Unidirectional Polymer Matrix Composite Materials Us-
the sandwich facing planes and result in compressive and
ing a Sandwich Beam
tensile forces in the facings. Permissible core material forms
D7250/D7250MPractice for Determining Sandwich Beam
include those with continuous bonding surfaces (such as balsa
Flexural and Shear Stiffness
wood and foams) as well as those with discontinuous bonding
E6Terminology Relating to Methods of Mechanical Testing
surfaces (such as honeycomb).
E122PracticeforCalculatingSampleSizetoEstimate,With
1.2 The values stated in either SI units or inch-pound units
Specified Precision, the Average for a Characteristic of a
are to be regarded separately as standard. The values stated in
Lot or Process
each system may not be exact equivalents; therefore, each
E177Practice for Use of the Terms Precision and Bias in
system shall be used independently of the other. Combining
ASTM Test Methods
values from the two systems may result in non-conformance
E251Test Methods for Performance Characteristics of Me-
with the standard.
tallic Bonded Resistance Strain Gages
1.2.1 Within the text, the inch-pound units are shown in
E456Terminology Relating to Quality and Statistics
brackets.
1.3 This standard does not purport to address all of the
3. Terminology
safety concerns, if any, associated with its use. It is the
3.1 Definitions—Terminology D3878 defines terms relating
responsibility of the user of this standard to establish appro-
to high-modulus fibers and their composites. Terminology E6
priate safety and health practices and determine the applica-
definestermsrelatingtomechanicaltesting.TerminologyE456
bility of regulatory limitations prior to use.
and Practice E177 define terms relating to statistics. In the
NOTE 1—Alternate procedures for determining the compressive event of a conflict between terms, Terminology D3878 shall
strength of unidirectional polymer matrix composites materials in a
have precedence over the other terminologies.
sandwich beam configuration may be found in Test Method D5467/
3.2 Symbols:
D5467M.
b = specimen width
2. Referenced Documents
c = core thickness
2
2.1 ASTM Standards:
CV = coefficient of variation statistic of a sample popu-
C393Test Method for Flexural Properties of Sandwich
lation for a given property (in percent)
Constructions
d = sandwich total thickness
F,nom
D3878Terminology for Composite Materials
D = effective sandwich flexural stiffness
f
E = effective facing chord modulus
ε = measuring strain in facing
u
1
This test method is under the jurisdiction of ASTM Committee D30 on
F = facing ultimate strength (tensile or compressive)
Composite Materials and is the direct responsibility of Subcommittee D30.09 on
F = core shear allowable strength
s
Sandwich Construction.
F = core compression allowable strength
c
CurrenteditionapprovedJuly1,2016.PublishedJuly2016.Originallyapproved
k = core shear strength factor to ensure facing failure
in 2006. Last previous edition approved in 2012 as D7249/D7249M–12. DOI:
l = length of loading span
10.1520/D7249_D7249M-16.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
L = length of support span
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
l = length of loading pad
pad
Standards volume information, refer to the standard’s Document Summary page on
n = number of specimens
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
D7249/D7249M − 16
specimen geometry, specimen preparation, specimen
P = applied force
conditioning, environment of testing, specimen alignment,
P = maximum force carried by test specimen before
max
loading procedure, speed of testing, facing void content,
failure
S = standard deviation statistic of a sample population adhesive void content, and facing volume percent reinforce-
n–1
ment. Further, facing strength may be diff
...
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.
´1
Designation: D7249/D7249M − 12 D7249/D7249M − 16
Standard Test Method for
Facing Properties of Sandwich Constructions by Long
1
Beam Flexure
This standard is issued under the fixed designation D7249/D7249M; 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
ε NOTE—Figure 6 was corrected editorially in March 2014.
1. Scope
1.1 This test method covers determination of facing properties of flat sandwich constructions subjected to flexure in such a
manner that the applied moments produce curvature of the sandwich facing planes and result in compressive and tensile forces in
the facings. 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. 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.
1.2.1 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 and health practices and determine the applicability of regulatory
limitations prior to use.
NOTE 1—Alternate procedures for determining the compressive strength of unidirectional polymer matrix composites materials in a sandwich beam
configuration may be found in Test Method D5467/D5467M.
2. Referenced Documents
2
2.1 ASTM Standards:
3
C274 Terminology of Structural Sandwich Constructions (Withdrawn 2016)
C393 Test Method for Flexural Properties of Sandwich Constructions
D3878 Terminology for Composite Materials
D5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite
Materials
D5467/D5467M Test Method for Compressive Properties of Unidirectional Polymer Matrix Composite Materials Using a
Sandwich Beam
D7250/D7250M Practice for Determining Sandwich Beam Flexural and Shear Stiffness
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
E251 Test Methods for Performance Characteristics of Metallic Bonded Resistance Strain Gages
E456 Terminology Relating to Quality and Statistics
3
E1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in Databases (Withdrawn 2015)
3
E1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases (Withdrawn 2015)
1
This test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.09 on Sandwich
Construction.
Current edition approved Aug. 1, 2012July 1, 2016. Published December 2012July 2016. Originally approved in 2006. Last previous edition approved in 20062012 as
D7249/D7249M – 06.D7249/D7249M – 12. DOI: 10.1520/D7249_D7249M-12.10.1520/D7249_D7249M-16.
2
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
1
---------------------- Page: 1 ----------------------
D7249/D7249M − 16
3. Terminology
3.1 Definitions—Terminology D3878 defines terms relating to high-modulus fibers and their composites. Terminology C274
defines terms relating to structural sandwich constructions. Terminology C393 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 terminologies.
3.2 Symbols:
b = specimen width
c = core thickness
CV = coefficient of variation statistic of a sample p
...
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