ASTM D6671/D6671M-22

Standard Test Method for Mixed Mode I-Mode II Interlaminar Fracture Toughness of Unidirectional Fiber Reinforced Polymer Matrix Composites

SIGNIFICANCE AND USE
5.1 Susceptibility to delamination is one of the major weaknesses of many advanced laminated composite structures. Knowledge of the interlaminar fracture resistance of composites is useful for product development and material selection. Since delaminations can be subjected to and extended by loadings with a wide range of mode mixtures, it is important that the composite toughness be measured at various mode mixtures. The toughness contour, in which fracture toughness is plotted as a function of mode mixtures (see Fig. 3), is useful for establishing failure criterion used in damage tolerance analyses of composite structures made from these materials.
FIG. 3 Mixed-Mode Summary Graph  
5.2 This test method can serve the following purposes:  
5.2.1 To establish quantitatively the effects of fiber surface treatment, local variations in fiber volume fraction, and processing and environmental variables on Gc of a particular composite material at various mode mixtures,  
5.2.2 To compare quantitatively the relative values of Gc versus mode mixture for composite materials with different constituents, and  
5.2.3 To develop delamination failure criteria for composite damage tolerance and durability analyses.  
5.3 This method can be used to determine the following delamination toughness values:  
5.3.1 Delamination Initiation—Two values of delamination initiation shall be reported: (1) at the point of deviation from linearity in the load-displacement curve (NL) and (2) at the point at which the compliance has increased by 5 % or the load has reached a maximum value (5%/max) depending on which occurs first along the load deflection curve (see Fig. 4). Each definition of delamination initiation is associated with its own value of Gc and  GII/G calculated from the load at the corresponding critical point. The 5%/Max  Gc value is typically the most reproducible of the three Gc values. The NL value is, however, the more conservative number. When the option of collecting ...
SCOPE
1.1 This test method covers the determination of interlaminar fracture toughness, Gc, of continuous fiber-reinforced composite materials at various Mode I to Mode II loading ratios using the Mixed-Mode Bending (MMB) Test.  
1.2 This test method is limited to use with composites consisting of unidirectional carbon fiber tape laminates with brittle and tough single-phase polymer matrices. This test method is further limited to the determination of fracture toughness as it initiates from a delamination insert. This limited scope reflects the experience gained in round robin testing. This test method may prove useful for other types of toughness values and for other classes of composite materials; however, certain interferences have been noted (see Section 6). This test method has been successfully used to test the toughness of both glass fiber composites and adhesive joints.  
1.3 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Jan-2022
• ICS: 19.060 - Mechanical testing
• ICS: 83.120 - Reinforced plastics
• Technical Committee: D30 - Composite Materials
• Drafting Committee: D30.06 - Interlaminar Properties

Relations

• Refers: ASTM D5229/D5229M-20 - Standard Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials
• Effective Date: 01-Mar-2020

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D6671/D6671M − 22
Standard Test Method for
Mixed Mode I-Mode II Interlaminar Fracture Toughness of
1
Unidirectional Fiber Reinforced Polymer Matrix Composites
This standard is issued under the fixed designation D6671/D6671M; 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 2. Referenced Documents
2
2.1 ASTM Standards:
1.1 This test method covers the determination of interlami-
D883Terminology Relating to Plastics
nar fracture toughness, G , of continuous fiber-reinforced
c
D2651GuideforPreparationofMetalSurfacesforAdhesive
composite materials at various Mode I to Mode II loading
Bonding
ratios using the Mixed-Mode Bending (MMB) Test.
D2734TestMethodsforVoidContentofReinforcedPlastics
1.2 This test method is limited to use with composites
D3171Test Methods for Constituent Content of Composite
consisting of unidirectional carbon fiber tape laminates with
Materials
brittle and tough single-phase polymer matrices. This test
D3878Terminology for Composite Materials
method is further limited to the determination of fracture
D5229/D5229MTestMethodforMoistureAbsorptionProp-
toughness as it initiates from a delamination insert. This
erties and Equilibrium Conditioning of Polymer Matrix
limited scope reflects the experience gained in round robin
Composite Materials
testing. This test method may prove useful for other types of
D5528TestMethodforModeIInterlaminarFractureTough-
toughness values and for other classes of composite materials;
ness of Unidirectional Fiber-Reinforced Polymer Matrix
however,certaininterferenceshavebeennoted(seeSection6).
Composites
This test method has been successfully used to test the
E4Practices for Force Calibration and Verification of Test-
toughness of both glass fiber composites and adhesive joints.
ing Machines
E6Terminology Relating to Methods of MechanicalTesting
1.3 Units—The values stated in either SI units or inch-
E122PracticeforCalculatingSampleSizetoEstimate,With
pound units are to be regarded separately as standard. The
Specified Precision, the Average for a Characteristic of a
values stated in each system are not necessarily exact equiva-
Lot or Process
lents; therefore, to ensure conformance with the standard, each
E177Practice for Use of the Terms Precision and Bias in
system shall be used independently of the other, and values
ASTM Test Methods
from the two systems shall not be combined.
E456Terminology Relating to Quality and Statistics
1.4 This standard does not purport to address all of the
3. Terminology
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 3.1 Terminology D3878 defines terms relating to high-
priate safety, health, and environmental practices and deter-
modulus fibers and their composites. Terminology D883 de-
mine the applicability of regulatory limitations prior to use. fines terms relating to plastics. Terminology E6 defines terms
relating to mechanical testing. Terminology E456 and Practice
1.5 This international standard was developed in accor-
E177 define terms relating to statistics. In the event of conflict
dance with internationally recognized principles on standard-
between terms, Terminology D3878 shall have precedence
ization established in the Decision on Principles for the
over the other terminology standards.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
NOTE 1—If the term represents a physical quantity, its analytical
Barriers to Trade (TBT) Committee.
dimensionsarestatedimmediatelyfollowingtheterm(orlettersymbol)in
fundamental dimension form, using the following ASTM standard sym-
bology for fundamental dimensions, shown within square brackets: [M]
for mass, [L] for length, [T] for time, [u] for thermodynamic temperature,
1
This test method is under the jurisdiction of ASTM Committee D30 on
Composite Materials and is the direct responsibility of Subcommittee D30.06 on
2
Interlaminar Properties. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Feb. 1, 2022. Published March 2022. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2001. Last previous edition approved in 2019 as D6671/D6671M–19. Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D6671_D6671M-22. the ASTM website.
Copyright © A
...

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: D6671/D6671M − 19 D6671/D6671M − 22
Standard Test Method for
Mixed Mode I-Mode II Interlaminar Fracture Toughness of
1
Unidirectional Fiber Reinforced Polymer Matrix Composites
This standard is issued under the fixed designation D6671/D6671M; 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 interlaminar fracture toughness, G , of continuous fiber-reinforced composite
c
materials at various Mode I to Mode II loading ratios using the Mixed-Mode Bending (MMB) Test.
1.2 This test method is limited to use with composites consisting of unidirectional carbon fiber tape laminates with brittle and
tough single-phase polymer matrices. This test method is further limited to the determination of fracture toughness as it initiates
from a delamination insert. This limited scope reflects the experience gained in round robin testing. This test method may prove
useful for other types of toughness values and for other classes of composite materials; however, certain interferences have been
noted (see Section 6). This test method has been successfully used to test the toughness of both glass fiber composites and adhesive
joints.
1.3 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in
each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used
independently of the other, and values from the two systems shall not be combined.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.5 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.
2. Referenced Documents
2
2.1 ASTM Standards:
D883 Terminology Relating to Plastics
D2651 Guide for Preparation of Metal Surfaces for Adhesive Bonding
D2734 Test Methods for Void Content of Reinforced Plastics
D3171 Test Methods for Constituent Content of Composite Materials
D3878 Terminology for Composite Materials
1
This test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.06 on Interlaminar
Properties.
Current edition approved March 15, 2019Feb. 1, 2022. Published April 2019March 2022. Originally approved in 2001. Last previous edition approved in 20132019 as
ε1
D6671/D6671M – 13D6671/D6671M – 19. . DOI: 10.1520/D6671_D6671M-19.10.1520/D6671_D6671M-22.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. 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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D6671/D6671M − 22
D5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite
Materials
D5528 Test Method for Mode I Interlaminar Fracture Toughness of Unidirectional Fiber-Reinforced Polymer Matrix Composites
E4 Practices for Force Calibration and Verification of Testing Machines
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. Terminology
3.1 Terminology D3878 defines terms relating to high-modulus fibers and their composites. 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 conflict between
...