ASTM D7956/D7956M-16
(Practice)Standard Practice for Compressive Testing of Thin Damaged Laminates Using a Sandwich Long Beam Flexure Specimen
Standard Practice for Compressive Testing of Thin Damaged Laminates Using a Sandwich Long Beam Flexure Specimen
SIGNIFICANCE AND USE
5.1 This practice provides a standard method of testing damaged composite laminates which are too thin to be tested using typical anti-buckling fixtures, such as those used in Test Method D7137/D7137M. The laminate is first impacted or indented in order to produce a damage state representative of actual monolithic solid laminate structure. Impacting or static indentation is not performed on an assembled sandwich panel, as the damage state is altered by energy absorption in the core and by support of the core during the impact or indentation event. After damaging, the laminate is bonded onto the core with the impacted or indentation side of the laminate against the core, and with a localized un-bonded area encompassing the damage site. Fig. 1 illustrates the adhesive removal to avoid the damaged area and the assembly of the sandwich specimen with the impacted damaged laminate flipped over from the impacting or indentation orientation. The final assembled sandwich specimen is then tested using a long beam flexure setup with the damaged laminate being on the compression side. The sandwich panel configuration is used as a form of anti-buckling support for the thin damaged laminate.
5.2 Susceptibility to damage from concentrated out-of-plane forces is one of the major design concerns of many structures made of advanced composite laminates. Knowledge of the damage resistance and damage tolerance properties of a laminated composite plate is useful for product development and material selection.
5.3 The residual strength data obtained using this test method is used in research and development activities as well as for design allowables; however the results are specific to the geometry and physical conditions tested and are generally not scalable to other configurations.
5.4 The properties obtained using this test method can provide guidance in regard to the anticipated damage tolerance capability of composite structures of similar material, thickness, stacking sequ...
SCOPE
1.1 This practice covers an approach for compressive testing thin damaged multidirectional polymer matrix composite laminates reinforced by high-modulus fibers using a sandwich long beam flexure specimen. It provides a test configuration in which the core does not constrain any protruding back side damage. It is limited to testing of monolithic solid laminates which are too thin to be tested using typical anti-buckling fixtures. It does not cover compressive testing of damaged sandwich panel facings. The composite material forms are limited to continuous-fiber or discontinuous-fiber (tape or fabric, or both) reinforced composites in which the laminate is balanced and symmetric with respect to the test direction
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.
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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: D7956/D7956M − 16
Standard Practice for
Compressive Testing of Thin Damaged Laminates Using a
1
Sandwich Long Beam Flexure Specimen
This standard is issued under the fixed designation D7956/D7956M; 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 Matrix Composite Materials with Unsupported Gage Sec-
tion by Shear Loading
1.1 This practice covers an approach for compressive test-
D6264/D6264M Test Method for Measuring the Damage
ing thin damaged multidirectional polymer matrix composite
Resistance of a Fiber-Reinforced Polymer-Matrix Com-
laminates reinforced by high-modulus fibers using a sandwich
posite to a Concentrated Quasi-Static Indentation Force
long beam flexure specimen. It provides a test configuration in
D7136/D7136M Test Method for Measuring the Damage
which the core does not constrain any protruding back side
Resistance of a Fiber-Reinforced Polymer Matrix Com-
damage. It is limited to testing of monolithic solid laminates
posite to a Drop-Weight Impact Event
which are too thin to be tested using typical anti-buckling
D7137/D7137M Test Method for Compressive Residual
fixtures. It does not cover compressive testing of damaged
StrengthPropertiesofDamagedPolymerMatrixCompos-
sandwich panel facings. The composite material forms are
ite Plates
limited to continuous-fiber or discontinuous-fiber (tape or
D7249/D7249M Test Method for Facing Properties of Sand-
fabric, or both) reinforced composites in which the laminate is
wich Constructions by Long Beam Flexure
balanced and symmetric with respect to the test direction
E6 Terminology Relating to Methods of Mechanical Testing
1.2 The values stated in either SI units or inch-pound units
E122 Practice for Calculating Sample Size to Estimate,With
are to be regarded separately as standard. The values stated in
Specified Precision, the Average for a Characteristic of a
each system may not be exact equivalents; therefore, each
Lot or Process
system shall be used independently of the other. Combining
E177 Practice for Use of the Terms Precision and Bias in
values from the two systems may result in non-conformance
ASTM Test Methods
with the standard.
E456 Terminology Relating to Quality and Statistics
1.2.1 Within the text the inch-pound units are shown in
brackets.
3. Terminology
1.3 This standard does not purport to address all of the
3.1 Definitions—Terminology D3878 defines terms relating
safety concerns, if any, associated with its use. It is the
to high-modulus fibers and their composites, as well as terms
responsibility of the user of this standard to establish appro-
relating to sandwich constructions. Terminology D883 defines
priate safety and health practices and determine the applica-
terms relating to plastics. Terminology E6 defines terms
bility of regulatory limitations prior to use.
relating to mechanical testing. Terminology E456 and Practice
E177 define terms relating to statistics. In the event of a
2. Referenced Documents
conflict between terms, Terminology D3878 shall have prece-
2
2.1 ASTM Standards:
dence over the other terminologies.
D883 Terminology Relating to Plastics
D3878 Terminology for Composite Materials
4. Summary of Practice
D3410 Test Method for Compressive Properties of Polymer
4.1 This practice consists of fabricating a composite
laminate, damaging the laminate using either Test Method
D6264/D6264M or Test Method D7136/D7136M, bonding the
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 impacted or indented side of the laminate onto core and a back
Sandwich Construction.
side facing to form a sandwich panel, and testing the damaged
Current edition approved Sept. 1, 2016. Published September 2016. Originally
laminate in compression using Test Method D7249/D7249M.
approved in 2014. Last previous edition approved in 2014 as -14. DOI: 10.1520/
D7956_D7956M-16.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 5. Significance and Use
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
5.1 This practice provides a standard method of testing
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. damaged composite laminates which are too thin to be tested
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
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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: D7956/D7956M − 14 D7956/D7956M − 16
Standard Practice for
Compressive Testing of Thin Damaged Laminates Using a
1
Sandwich Long Beam FixtureFlexure Specimen
This standard is issued under the fixed designation D7956/D7956M; 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 practice covers an approach for compressive testing thin damaged multidirectional polymer matrix composite
laminates reinforced by high-modulus fibers using a sandwich long beam flexure specimen. It provides a test configuration in
which the core does not constrain any protruding back side damage. It is limited to testing of monolithic solid laminates which
are too thin to be tested using typical anti-buckling fixtures. It does not cover compressive testing of damaged sandwich panel
facings. The composite material forms are limited to continuous-fiber or discontinuous-fiber (tape or fabric, or both) reinforced
composites in which the laminate is balanced and symmetric with respect to the test direction
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.
2. Referenced Documents
2
2.1 ASTM Standards:
3
C274 Terminology of Structural Sandwich Constructions (Withdrawn 2016)
D883 Terminology Relating to Plastics
D3878 Terminology for Composite Materials
D3410 Test Method for Compressive Properties of Polymer Matrix Composite Materials with Unsupported Gage Section by
Shear Loading
D6264/D6264M Test Method for Measuring the Damage Resistance of a Fiber-Reinforced Polymer-Matrix Composite to a
Concentrated Quasi-Static Indentation Force
D7136/D7136M Test Method for Measuring the Damage Resistance of a Fiber-Reinforced Polymer Matrix Composite to a
Drop-Weight Impact Event
D7137/D7137M Test Method for Compressive Residual Strength Properties of Damaged Polymer Matrix Composite Plates
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
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, 2014Sept. 1, 2016. Published September 2014September 2016. Originally approved in 2014. Last previous edition approved in 2014
as -14. DOI: 10.1520/D7956_D7956M-14.10.1520/D7956_D7956M-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
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D7956/D7956M − 16
3. Terminology
3.1 Definitions—Terminology D3878 defines terms relating to high-modulus fibers and their composites.
Terminologycomposites, as C274 defineswell as terms relating to structural sandwich constructions. Terminology D883 defines
terms relating to plastics. Terminology E6 defines terms relating to mechanical testing. Terminology E456 and Practice E177 define
terms relating to statistics. In the event
...
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