ASTM F521-22

Standard Test Methods for Bond Integrity of Transparent Laminates

SIGNIFICANCE AND USE
4.1 These test methods provide a means to measure quantitatively the bond integrity between the outer layers of the transparency and the interlayer, or to measure the cohesive properties of the interlayer, under various loading conditions.  
4.2 These test methods provide empirical results useful for control purposes, correlation with service results, and as quality control tests for acceptance of production parts.  
4.3 Test results obtained on small, laboratory-size samples shown herein are indicative of full-size part capability, but not necessarily usable for design purposes.
SCOPE
1.1 These test methods cover determination of the bond integrity of transparent laminates. The laminates are usually made of two or more glass or hard plastic sheets held together by an elastomeric material. These test methods are intended to provide a means of determining the strength of the bond between the glass or plastic and the elastomeric interlayer under various mechanical or thermal loading conditions.  
1.2 The test methods appear as follows:    
Test Methods  
Sections  
Test Method A—Flatwise Bond Tensile Strength  
5 – 11  
Test Method B—Interlaminar Shear Strength  
12 – 17  
Test Method C—Creep Rupture  
18 – 25  
Test Method D—Thermal Exposure  
26 – 30  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 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: 49.025.40 - Rubber and plastics
• Technical Committee: F07 - Aerospace and Aircraft
• Drafting Committee: F07.08 - Transparent Enclosures and Materials

Relations

• Refers: ASTM D952-10 - Standard Test Method for Bond or Cohesive Strength of Sheet Plastics and Electrical Insulating Materials
• Effective Date: 01-May-2010
• Refers: ASTM D952-02 - Standard Test Method for Bond or Cohesive Strength of Sheet Plastics and Electrical Insulating Materials
• Effective Date: 10-Apr-2002
• Refers: ASTM D952-95 - Standard Test Method for Bond or Cohesive Strength of Sheet Plastics and Electrical Insulating Materials
• Effective Date: 10-Apr-2002

Overview

ASTM F521-22: Standard Test Methods for Bond Integrity of Transparent Laminates is a vital standard developed by ASTM International for evaluating the bond integrity of transparent laminates. Transparent laminates are typically composed of two or more sheets of glass or hard plastics bonded by elastomeric interlayers, commonly found in aerospace transparencies, safety-glass applications, and other demanding environments. This standard provides robust and quantitative test methods to assess the bond strength between layers or the cohesive properties of the interlayer under a range of mechanical and thermal conditions.

Key Topics

• Purpose and Scope

  • Outlines quantitative techniques to measure bond integrity in transparent laminates
  • Addresses both adhesive strength and cohesive properties of the interlayer
  • Applies to laminates of glass or hard plastic with elastomeric interlayers

• Test Methods
  ASTM F521-22 specifies four main test methods:

  • Test Method A: Flatwise Bond Tensile Strength
    • Measures tensile strength perpendicular to the laminate surface
  • Test Method B: Interlaminar Shear Strength
    • Assesses shear strength parallel to the interlayer interface
  • Test Method C: Creep Rupture
    • Evaluates response to sustained load under various conditions over time
  • Test Method D: Thermal Exposure
    • Tests resistance to failure from extreme temperature cycles

• Empirical Results

  • Test data support quality control, process monitoring, and validation of new materials or production batches
  • Laboratory-scale specimen results indicate full-size part capability but are not directly intended for engineering design

• Reporting Requirements

  • Comprehensive reporting includes material identification, adhesive and specimen details, test conditions, and failure modes

Applications

• Aerospace and Aircraft Transparencies
  • Verification of the bond integrity in windshields, windows, and canopies for aircraft safety and performance
• Safety Glazing
  • Quality control for automotive and architectural glass where delamination or bond failure could compromise safety
• Material Development and Process Improvement
  • Evaluation of new interlayer materials or lamination methods
• Production Part Acceptance
  • Routine batch control and acceptance testing for transparent laminated parts
• Correlation with Service Performance
  • Empirical data help predict in-service durability of transparent laminated assemblies

Related Standards

• ASTM D952: Test Method for Bond or Cohesive Strength of Sheet Plastics and Electrical Insulating Materials
  • Provides a referenced method for evaluating bond integrity in related materials
• ANSI B1.1: Standard for Unified Screw Threads
  • Specifies thread forms referenced for test apparatus construction

Additional related standards may include those focusing on glass safety, polymer interlayers, and materials testing under environmental exposure. Users should refer to current ASTM and ANSI resources for the latest versions and companion standards.

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ASTM F521-22 is essential for manufacturers, suppliers, and quality assurance professionals involved in transparent laminate production or procurement. Implementing these standardized test methods ensures the reliability and safety of laminated glass and plastic assemblies in critical applications, supporting robust product performance and regulatory compliance. For further guidance, stakeholders are encouraged to consult the full standard and related ASTM and ANSI documents.

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: F521 − 22
Standard Test Methods for
Bond Integrity of Transparent Laminates
ThisstandardisissuedunderthefixeddesignationF521;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 These test methods cover determination of the bond 3.1 Definitions:
integrity of transparent laminates. The laminates are usually 3.1.1 delamination, n—a visible separation between two
made of two or more glass or hard plastic sheets held together layers of bonded material.
by an elastomeric material. These test methods are intended to
3.1.2 face plies, n—transparent glass or plastic outer mate-
provide a means of determining the strength of the bond
rials joined together with an interlayer.
between the glass or plastic and the elastomeric interlayer
3.1.3 interlayer, n—transparentmaterialusedasthebonding
under various mechanical or thermal loading conditions.
agent between two or more hard, transparent materials.
1.2 The test methods appear as follows:
3.2 Definitions of Terms Specific to This Standard:
Test Methods Sections
3.2.1 number of plies, n—a three-ply laminate is one having
Test MethodA—Flatwise Bond Tensile Strength 5–11
two transparent glass or plastic plies and one interlayer ply; a
Test Method B—Interlaminar Shear Strength 12–17
Test Method C—Creep Rupture 18–25
five-ply laminate has three glass or plastic plies and two
Test Method D—Thermal Exposure 26–30
interlayer plies.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Significance and Use
responsibility of the user of this standard to establish appro-
4.1 These test methods provide a means to measure quan-
priate safety, health, and environmental practices and deter-
titatively the bond integrity between the outer layers of the
mine the applicability of regulatory limitations prior to use.
transparency and the interlayer, or to measure the cohesive
1.4 This international standard was developed in accor-
properties of the interlayer, under various loading conditions.
dance with internationally recognized principles on standard-
4.2 These test methods provide empirical results useful for
ization established in the Decision on Principles for the
control purposes, correlation with service results, and as
Development of International Standards, Guides and Recom-
quality control tests for acceptance of production parts.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
4.3 Test results obtained on small, laboratory-size samples
shown herein are indicative of full-size part capability, but not
2. Referenced Documents
necessarily usable for design purposes.
2.1 ASTM Standards:
TEST METHOD A—FLATWISE BOND TENSILE
D952 Test Method for Bond or Cohesive Strength of Sheet
STRENGTH
Plastics and Electrical Insulating Materials
2.2 ANSI Standard:
5. Summary of Test Method
B1.1 Standard for Unified Screw Threads
5.1 Thebondissubjectedtoamechanicalloadinadirection
perpendicular to the plane of the bond. The adhesive or
cohesive strength between the interlayer and the outer layers
These test methods are under the jurisdiction of ASTM Committee F07 on
(flatwisetensilestrength)isdetermined,andexpressedinterms
Aerospace andAircraft and are the direct responsibility of Subcommittee F07.08 on
of pascals (or pounds-force per square inch).
Transparent Enclosures and Materials.
Current edition approved Feb. 1, 2022. Published February 2022. Originally
approved in 1977. Last previous edition approved in 2016 as F521 – 16. DOI:
6. Apparatus
10.1520/F0521-22.
6.1 Metal Blocks—A pair of 50 mm (2 in.) square metal
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
blocks of 24 ST aluminum alloy, each having a maximum
Standards volume information, refer to the standard’s Document Summary page on
height of 50 mm (2 in.). Each block shall have in one end a
the ASTM website.
hole (see Fig. 1) tapped 22.2 mm ( ⁄8 in.) in accordance with
Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. ANSI B1.1, to accommodate threaded 22.2 mm ( ⁄8-in.) studs
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959. United States
F521 − 22
FIG. 1 Test Assembly for Flatwise Tensile Strength Test
F521 − 22
of convenient length (see Test Method D952). Alternative 7. Test Specimen
metal blocks utilize an aluminum “T” section, cut to 50 mm
7.1 Thetestspecimenshallconsistofa50 mm(2 in.)square
(2 in.) square. A hole shall be drilled in the upright section of
sample of laminate prepared in such a manner as to produce
each “T” block (see Fig. 2) to accommodate a metal pin or
smooth edges to minimize the possibility of edge chipping
holding device compatible with the test machine used.
during testing. The thickness of the specimen shall be the
6.2 Testing Machine—Anysuitablemachineoftheconstant- thickness of the laminate. The upper and lower surfaces shall
rate-of-crossheadmovementtype.Thetestingmachineshallbe be parallel to each other and reasonably flat. Test five speci-
equipped with the necessary drive mechanism for imparting to mens.
the crosshead a uniform, controlled velocity with respect to the
base. The testing machine shall also be equipped with a 8. Preparation of Apparatus
load-indicating mechanism capable of showing the total load
8.1 Determine the cross-sectional area of the test specimen
applied to the test specimen. This mechanism shall be essen-
in a plane parallel to the surface.
tially free from inertial-lag at the specified rate of testing and
8.2 Gently abrade the bonding surfaces of the metal blocks
shall indicate the load with an accuracy of 61.0 % of the
and the specimen (except glass—see Note 1) using 200–400
indicated value, or better.
grit paper or light sandblasting. Do not abrade the edges and
6.3 Adhesive—Any suitable adhesive.
corners of the specimen or the metal blocks. Do not round the
corners.
Hysol Adhesive 907, a two-part epoxy adhesive available from E. V. Roberts
NOTE 1—Do not abrade glass surfaces unless absolutely necessary to
Co., 9601 West Jefferson Blvd., Culver City, CA90230, has been found satisfactory
obtain adhesion to the thoroughly cleaned surface.
for use in this test. The instructions in Section 8 for preparation of the test assembly
are based on the use of this material. Any adhesive that is found to perform
8.3 Clean all contact surfaces of the specimens and metal or
satisfactorily under this test may be used, provided that the procedure for the
“T” blocks with a soft cloth saturated with a suitable solvent or
preparation of the test assembly is suitably modified to follow the manufacturer’s
recommendation for the use of the adhesive. clean dry air blast. Thereafter, do not touch the cleaned
FIG. 2 Optional Tensile Strength Test Specimen
F521 − 22
surfaces with the hands. Apply a thin coating of adhesive to 13. Apparatus
both contact surfaces being careful to remove all air bubbles
13.1 Shear Tool—A shear test fixture of the sliding type
from the adhesive. Place the specimen between the coated
which is so constructed that the specimen faces are firmly
blocks, being certain the blocks are aligned, then clamp the
supported between the stationary and movable blocks to
assembly until the adhesive is cured.
minimize peel effects. Suitable forms of shear tools are shown
in Figs. 3 and 4, depending on specimen type.
9. Conditioning
13.2 Testing Machine—See 6.2.
9.1 Condition the test specimen at 23 6 2 °C (73.4 6
3.6 °F) and 50 6 5 % relative humidity for not less than 24 h
14. Test Specimen
prior to testing.
14.1 The test specimens shall be either three-ply or five-ply
9.2 Conduct tests in the Standard LaboratoryAtmosphere of
construction as shown in Figs. 5 and 6. The five-ply construc-
23 6 2 °C (73.4 6 3.6 °F) and 50 6 5 % relative humidity,
tion is preferred, especially for specimens with relatively thick
unless otherwise specified.
interlayers of 2.5 mm (0.1 in.) or more.
14.2 The test specimen shall be 50 mm (2 in.) square
10. Procedure
minimum. Increasing specimen size will give slightly better
10.1 Unless otherwise specified, test five specimens. Insert accuracy up to the point where the face plies begin to fracture.
the specimen assembly in the tension testing machine with Prepare the specimens in such a manner as to produce smooth
self-aligning holders and load to failure at a rate of 1.25 mm edges to minimize premature edge chipping during testing.
(0.05 in.)/min.
14.3 Orient the samples to duplicate the actual loading
conditions in service whenever possible.
10.2 If block adhesive failure occurs, discard the test and
test another specimen.
14.4 Number of Test Specimens:
14.4.1 Test at least five specimens for each sample in the
NOTE 2—This retest is only required if failure strength of the interlayer
case of isotropic materials.
is required. If the test is being used to meet some minimum failure
strength requirement and the specimen exceeds this value with a block
14.4.2 Test ten specimens, five normal to, and five parallel
adhesivefailure,additionaltestingisnotrequired.Thelocationandfailure
with the principal axis of anisotropy, for each sample of
mode shall be documented as required in 11.1.6.
anisotropic material.
NOTE 3—If aluminum blocks are to be reused, one method of removing
14.4.3 Discard specimens that break at some obvious flaw
the adhesive is to insert the blocks in an oven at 150 °C (300 °F) for 1.5
and retest, unless such flaws constitute a variable whose effect
h. When the blocks have cooled, the remaining portion of the test
specimen is easily removed by a surface sanding wheel or sandblast. In is desired for study.
order to maintain a plane surface, it is recommended that the metal blocks
be finished on a flat emery surface.
15. Conditioning
15.1 Condition the specimens in accordance with Section 9.
11. Report
11.1 The report shall include the following:
16. Procedure
11.1.1 Completeidentificationofthematerialtested,includ-
16.1 Measure and record the length and width of the bond
ing type or grade of substrate and interlayer, thickness,
area with a suitable micrometer to the nearest 0.025 mm
manufacturing history, and so forth,
(0.001 in.).
11.1.2 The block adhesive used,
16.2 Pl
...

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: F521 − 16 F521 − 22
Standard Test Methods for
Bond Integrity of Transparent Laminates
This standard is issued under the fixed designation F521; 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 These test methods cover determination of the bond integrity of transparent laminates. The laminates are usually made of two
or more glass or hard plastic sheets held together by an elastomeric material. These test methods are intended to provide a means
of determining the strength of the bond between the glass or plastic and the elastomeric interlayer under various mechanical or
thermal loading conditions.
1.2 The test methods appear as follows:
Test Methods Sections
Test Method A—Flatwise Bond Tensile Strength 5 – 11
Test Method B—Interlaminar Shear Strength 12 – 17
Test Method C—Creep Rupture 18 – 25
Test Method D—Thermal Exposure 26 – 30
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.
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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.4 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
2.1 ASTM Standards:
D952 Test Method for Bond or Cohesive Strength of Sheet Plastics and Electrical Insulating Materials
2.2 ANSI Standard:
B1.1 Standard for Unified Screw Threads
These test methods are under the jurisdiction of ASTM Committee F07 on Aerospace and Aircraft and are the direct responsibility of Subcommittee F07.08 on
Transparent Enclosures and Materials.
Current edition approved April 1, 2016Feb. 1, 2022. Published April 2016February 2022. Originally approved in 1977. Last previous edition approved in 20102016 as
F521 – 83 (2010).F521 – 16. DOI: 10.1520/F0521-16.10.1520/F0521-22.
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.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F521 − 22
3. Terminology
3.1 Definitions:
3.1.1 delamination, n—a visible separation between two layers of bonded material.
3.1.2 face plies, n—transparent glass or plastic outer materials joined together with an interlayer.
3.1.3 interlayer, n—transparent material used as the bonding agent between two or more hard, transparent materials.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 number of plies, n—a three-ply laminate is one having two transparent glass or plastic plies and one interlayer ply. Aply; a
five-ply laminate has three glass or plastic plies and two interlayer plies.
4. Significance and Use
4.1 These test methods provide a means to measure quantitatively the bond integrity between the outer layers of the transparency
and the interlayer, or to measure the cohesive properties of the interlayer, under various loading conditions.
4.2 These test methods provide empirical results useful for control purposes, correlation with service results, and as quality control
tests for acceptance of production parts.
4.3 Test results obtained on small, laboratory-size samples shown herein are indicative of full-size part capability, but not
necessarily usable for design purposes.
TEST METHOD A—FLATWISE BOND TENSILE STRENGTH
5. Summary of Test Method
5.1 The bond is subjected to a mechanical load in a direction perpendicular to the plane of the bond. The adhesive or cohesive
strength between the interlayer and the outer layers (flatwise tensile strength) is determined, and expressed in terms of pascals (or
pounds-force per square inch).
6. Apparatus
6.1 Metal Blocks—A pair of 50-mm (2-in.)50 mm (2 in.) square metal blocks of 24 ST aluminum alloy, each having a maximum
height of 50 mm (2 in.). Each block shall have in one end a hole (see Fig. 1) tapped 22.2 mm ( ⁄8 in.) in accordance with ANSI
B1.1, to accommodate threaded 22.2-mm22.2 mm ( ⁄8-in.) studs of convenient length (see Test Method D952). Alternative metal
blocks utilize an aluminum “T” section, cut to 50 mm (2 in.) square. A hole shall be drilled in the upright section of each “T” block
(see Fig. 2) to accommodate a metal pin or holding device compatible with the test machine used.
6.2 Testing Machine—Any suitable machine of the constant-rate-of-crosshead movement type. The testing machine shall be
equipped with the necessary drive mechanism for imparting to the crosshead a uniform, controlled velocity with respect to the base.
The testing machine shall also be equipped with a load-indicating mechanism capable of showing the total load applied to the test
specimen. This mechanism shall be essentially free from inertial-lag at the specified rate of testing and shall indicate the load with
an accuracy of 61.0 % of the indicated value, or better.
6.3 Adhesive—Any suitable adhesive.
7. Test Specimen
7.1 The test specimen shall consist of a 50-mm (2-in.)50 mm (2 in.) square sample of laminate prepared in such a manner as to
Hysol Adhesive 907, a two-part epoxy adhesive available from E. V. Roberts Co., 9601 West Jefferson Blvd., Culver City, CA 90230, has been found satisfactory for
use in this test. The instructions in Section 8 for preparation of the test assembly are based on the use of this material. Any adhesive that is found to perform satisfactorily
under this test may be used, provided that the procedure for the preparation of the test assembly is suitably modified to follow the manufacturer’s recommendation for the
use of the adhesive.
F521 − 22
FIG. 1 Test Assembly for Flatwise Tensile Strength Test
F521 − 22
FIG. 2 Optional Tensile Strength Test Specimen
produce smooth edges to minimize the possibility of edge chipping during testing. The thickness of the specimen shall be the
thickness of the laminate. The upper and lower surfaces shall be parallel to each other and reasonably flat. Test five specimens.
8. Preparation of Apparatus
8.1 Determine the cross-sectional area of the test specimen in a plane parallel to the surface.
8.2 Gently abrade the bonding surfaces of the metal blocks and the specimen (except glass—see Note 1) using 200–400 grit paper
or light sandblasting. Do not abrade the edges and corners of the specimen or the metal blocks. Do not round the corners.
NOTE 1—Do not abrade glass surfaces unless absolutely necessary to obtain adhesion to the thoroughly cleaned surface.
8.3 Clean all contact surfaces of the specimens and metal or “T” blocks with a soft cloth saturated with a suitable solvent or clean
dry air blast. Thereafter, do not touch the cleaned surfaces with the hands. Apply a thin coating of adhesive to both contact surfaces
being careful to remove all air bubbles from the adhesive. Place the specimen between the coated blocks, being certain the blocks
are aligned, then clamp the assembly until the adhesive is cured.
9. Conditioning
9.1 Condition the test specimen at 23 6 2°C2 °C (73.4 6 3.6°F)3.6 °F) and 50 6 5 % relative humidity for not less than 24 h
prior to testing.
F521 − 22
9.2 Conduct tests in the Standard Laboratory Atmosphere of 23 6 2°C2 °C (73.4 6 3.6°F)3.6 °F) and 50 6 5 % relative humidity,
unless otherwise specified.
10. Procedure
10.1 Unless otherwise specified, test five specimens. Insert the specimen assembly in the tension testing machine with
self-aligning holders and load to failure at a rate of 1.25 mm (0.05 in.)/min.
10.2 If block adhesive failure occurs, discard the test and test another specimen.
NOTE 2—This retest is only required if failure strength of the interlayer is required. If the test is being used to meet some minimum failure strength
requirement and the specimen exceeds this value with a block adhesive failure, additional testing is not required. The location and failure mode shall be
documented as required in 11.1.6.
NOTE 3—If aluminum blocks are to be reused, one method of removing the adhesive is to insert the blocks in an oven at 150°C (300°F)150 °C (300 °F)
for 1.5 h. When the blocks have cooled, the remaining portion of the test specimen is easily removed by a surface sanding wheel or sandblast. In order
to maintain a plane surface, it is recommended that the metal blocks be finished on a flat emery surface.
11. Report
11.1 The report shall include the following:
11.1.1 Complete identification of the material tested, including type or grade of substrate and interlayer, thickness, manufacturing
history, and so forth,
11.1.2 The block adhesive used,
11.1.3 The atmospheric conditions in the test room,
11.1.4 The total load, in newtons (or pounds-force), required to break each specimen,
11.1.5 The unit stress, in pascals (or pounds-force per square inch), required for failure (calculate the unit stress by dividing the
load by the area of the test specimen), and
11.1.6 Failure mode (such as within the interlayer, or at which interface).
TEST METHOD B—INTERLAMINAR SHEAR STRENGTH
12. Summary of Test Method
12.1 The bond is subjected to mechanical load in the direction of the plane of the interlayer. The maximum adhesive or cohesive
strength between the interlayer and the outer plies (shear strength) is determined, and is expressed in pascals (or pounds-force per
square inch).
13. Apparatus
13.1 Shear Tool—A shear test fixture of the sliding type which is so constructed that the specimen faces are firmly supported
between the stationary and movable blocks to minimize peel effects. Suitable forms of shear tools are shown in Figs. 3 and 4,
depending on specimen type.
13.2 Testing Machine—See 6.2.
14. Test Specimen
14.1 The test specimens shall be either three-ply or five-ply construction as shown in Figs. 5 and 6. The five-ply construction is
preferred, especially for specimens with relatively thick interlayers of 2.5 mm (0.1 in.) or more.
...