ISO 8065:2024

Composites and reinforcements fibres — Mechanoluminescent visualization method of crack propagation for joint evaluation

This document applies to the measurement of crack tip position and crack propagation on the bonding surface of carbon fibre reinforced plastic (CFRPs) and metal assemblies bonded panels. This document does not apply to the visualization measurement of strain distribution or defects during load application to specimens. This document does not intend to: a) omit relevant field tests for CFRP related engineering; b) generally specify the dimensions of test specimen to represent CFRPs related bonded or fastened structures; c) superimpose test results for specific applications of the parameters that exceed the range of this document.

Composites et fibres de renforts — Méthode de visualisation mécanoluminescente de la propagation des fissures pour l'évaluation des assemblages

General Information

• Status: Published
• Publication Date: 21-May-2024
• ICS: 83.120 - Reinforced plastics
• Technical Committee: ISO/TC 61/SC 13 - Composites and reinforcement fibres
• Drafting Committee: ISO/TC 61/SC 13 - Composites and reinforcement fibres
• Current Stage: 6060 - International Standard published
• Start Date: 22-May-2024
• Due Date: 06-Aug-2024
• Completion Date: 22-May-2024

Standards Content (Sample)

International
Standard
ISO 8065
First edition
Composites and reinforcements
2024-05
fibres — Mechanoluminescent
visualization method of crack
propagation for joint evaluation
Composites et fibres de renforts — Méthode de visualisation
mécanoluminescente de la propagation des fissures pour
l'évaluation des assemblages
Reference number
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© ISO 2024
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2  Normative references . 1
3  Terms and definitions . 1
4  Principle . 1
5 Specimen preparation . . 2
5.1 Specimen .2
5.2 Surface pre-treatment .2
5.3 Preparation for mechanoluminescence paint .2
5.4 Method of applying mechanoluminescence paint .2
5.5 Post-treatment .2
5.6 Scale labelling on specimen .2
6  Test equipment and testing procedure . . 4
6.1 Measurement equipment for mechanoluminescence .4
6.2 Test conditions .4
6.3 Recording conditions of mechanoluminescence .5
7  Data analysis . 5
7.1 Position of crack tip .5
7.2 Delamination analysis.7
8 Test report . 7
Annex A (informative)  Mechanoluminescence (ML) material . 9
Annex B (informative)  Example of conditions for ML measurements .13
Annex C (informative)  Demonstration: Effect on quality of mechanoluminescent paint coating
for monitoring performance of crack tip . 19
Annex D (informative)  Examples of determination methods of the highest ML point .20
Annex E (informative)  Demonstration — Synchronising ML line on adherend and failure from
in bond line .21
Annex F (informative)  List of samples in DCB testing .23
Annex G (informative)  Results of interlaboratory tests in DCB and SLS test .25
Bibliography .26

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
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with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
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constitute an endorsement.
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related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 13, Composites
and reinforcement fibres.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
This document specifies a method for mechanoluminescent visualization of position of crack tip and crack
propagation for joint evaluation of the bonded plates of carbon fibre reinforced plastics (CFRPs) to metal
assemblies, with a standard specimen and under specified conditions of preparation, conditioning and
testing. This method is intended for testing only those bonded plates used in bonding carbon fibre reinforced
plastics (CFRPs) to metal assemblies.
The potential benefits to the users of mechanoluminescent visualization method of crack propagation for
joint evaluation of the bonded plates of carbon fibre reinforced plastics (CFRPs) to metal assemblies based
on this document are:
a) providing precise position and amount of crack propagation, required for quantitatively calculating
evaluation of the fracture toughness energy through double cantilever beam (DCB) test for opening mode.
b) providing precise position and amount of crack propagation for end notched flexure (ENF) test and end-
loaded split (ELS) test, which evaluate the fracture toughness (mode II) of crack propagation without
opening against shear stress.
c) providing visual information of crack propagation behaviour that occurs around adhesive bond layer
inside the joint during the adhesive evaluation test, such as tensile shear test, cross tension, etc;
d) for reliable evaluation, providing visual information of asymmetric behaviour of deformation in both
adherends, originated from asymmetric flexural rigidity of both adherends, which occurs especially
when joining dissimilar materials;
e) for reliable evaluation to confirm health of adherend, providing of visual information of minor damage
and fracture in one or both adherends, which causes scattering in the evaluation value of adhesive
strength and performance, originated from asymmetric flexural rigidity of both adherends, especially
in joining dissimilar materials;
f) expanding CFRP applications to the fields of the combinations with metallic components;
g) the detection or the prevention of physical properties loss - such as ion migration and time-related
degradation in sealant film, injected calking layer and glass fibre reinforced plastics (GFRPs) layer;
h) demonstrating the conformity to specified conditions for type certification requirements in the
engineering such as aircraft developments;
i) evaluating the procedures for maintenance, repair and overhaul (MRO) in the engineering operations
such of CFRP aircrafts.
v
International Standard ISO 8065:2024(en)
Composites and reinforcements fibres —
Mechanoluminescent visualization method of crack
propagation for joint evaluation
1 Scope
This document applies to the measurement of crack tip position and crack propagation on the bonding
surface of carbon fibre reinforced plastic (CFRPs) and metal assemblies bonded panels.
This document does not apply to the visualization measurement of strain distribution or defects during load
application to specimens.
This document does not intend to:
a) omit relevant field tests for CFRP related engineering;
b) generally specify the dimensions of test specimen to represent CFRPs related bonded or fastened
structures;
c) superimpose test results for specific applications of the parameters that exceed the range of this
document.
2  Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 10365, Adhesives — Designation of main failure patterns
3  Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 10365 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
mechanoluminescence
ML
luminescence generated by mechanical stimulation
4  Principle
Mechanoluminescence (ML) intensity is proportional to the strain energy of measurement object. Therefore,
at crack tip, strain is concentrated under loading, and intense mechanoluminescence can be generated
reflecting the strain concentration at the crack tip to visualize the position of the crack tip.

5 Specimen preparation
5.1 Specimen
Various type of bonded plates can be used, such as double-cantilever beam (DCB) specimen, end-notch
flexure (ENF) specimen, single lap shear (SLS), end-load split (ELS), double lap shear (DLS), cross tension
(CT), etc. (see Figure 1).
DCB specimen SLS specimen CT specimen
Key
1 ML paint
Figure 1 — Examples of test specimens for mechanoluminescence visualization of crack tip and
crack propagation such as DCB, SLS and CT test
5.2  Surface pre-treatment
Surface pre-treatment can be used to make fine adhesion between mechanoluminescence (ML) paint and
surface of specimen, but it is not mandatory. As the method of surface pre-treatment, solvent degreasing,
sanding, atmospheric pressure plasma treatment, etc. can be used. However, a method that does not affect
the adhesive bonding performance and the strength of the adherend should be selected.
5.3  Preparation for mechanoluminescence paint
Mechanoluminescence (ML) paint is prepared by mixing ML material and polymer resin. It is possible to use
any ML materials and polymer materials. Candidate ML material is shown in Annex A.
5.4  Method of applying mechanoluminescence paint
Mechanoluminescence (ML) paint can be apply on the surface of specimen by spraying, dipping, or brushing,
etc. It is preferable that the film thickness is uniform, however, even if it is not uniform, it does not affect the
crack tip monitoring mechanoluminescence.
NOTE Conditions for applying mechanoluminescence paint are shown in Annex B (B.1 for DCB test, B.2 for SLS
test, B.3 for CT test). Effect on quality of mechanoluminescent paint coating is described for monitoring performance
of crack tip in Annex C.
5.5  Post-treatment
As a post-treatment, in order to cure the mechanoluminescent (ML) paint, thermosetting, photocuring, room
temperature curing, etc. can be performed depending on the polymer material of the ML paint. However,
condition of the post-treatment should be selected within a range of conditions that does not affect the test
piece and bonding performance.
5.6  Scale labelling on specimen
In case it is necessary to determine the length of crack propagation from initial, for example for calculating
fracture energy and toughness in DCB test, ENF and c-ELS test, scale labelling from initial crack should be

marked with black pen at least every 10 mm (see Figure 2). The scale labelling should be beneficial not
only at only one side but also other surface. For example, the scale inside surface can be used to determine
crack length and the ones on top and bottom surface should be beneficial to identify the position of
mechanoluminescent (ML) line reflecting fracture front in bond line.
a) Photo in sideview
b) Side and top views under UV light
c) ML image
Key
1 metal plate A position of initial crack
2 adhesive layer B scale labelling
3 CFRTP plate C direction of crack propagation
4 ML paint D ML line
Figure 2 — Example of scale labelling for DCB testing

6  Test equipment and testing procedure
6.1  Measurement equipment for mechanoluminescence
A four-way camera setup of the test piece is recommended (see Figure 3), but at least the tip of the crack to
be monitored should be set up with the camera facing the position where it can be recorded.
NOTE 4-way camera system is not mandatory. Number of cameras depends on which face of specimen you want
to focus and record.
Key
1 camera 1
2 camera 2
3 camera 3
4 camera 4
F load
Figure 3 — Example of equipment for mechanoluminescence visualization of crack tip and crack
propagation
6.2 Test conditions
Mechanical conditions of testing bonded samples should follow the respective joining test standards:
— ISO 22838
— ISO 22841
6.3  Recording conditions of mechanoluminescence
Recording rate, frame-per-second (fps), should be determined in consideration of the crack growth rate in
each adhesion evaluation test. In addition, frame-per-second (fps), exposure time, gain, etc. are determined
in consideration of the characteristics of the applied mechanoluminescent material. Specifically, the
conditions can be set, in which mechanoluminescence should be recorded during crack growth from the
initial crack to the end of the testing.
NOTE Examples of recording conditions responding to each testing are shown in Annex B (B.1 for DCB test, B.2
for SLS test, B.3 for CT test).
7  Data analysis
7.1  Position of crack tip
Position of crack tip during testing can be determined as a point with highest mechanoluminescent (ML)
luminance in adhesive layer, by reading the position of the rearmost edge (see Figure 4). The ML contour
image converted from raw image should be easier to identifying highest ML point reflecting position of
crack tip (see Figure 5 and Annex D). From this information of crack tip position, the crack length can be
calculated and used to evaluate the adhesive fracture toughness energy in DCB test, ENF test, c-ELS test, etc.
In addition, by visualizing the crack tip by mechanoluminescence, it is possible to identify the fracture origin
point and propagation of the adhesive bond during joint evaluation (see Figure 6).
a) ML images at 120 and 420 s loading b) Microscopic image at crack tip
Key
1 metal plate
2 adhesive layer
3 metal plate
A ML points
B position of crack tip
F load
Figure 4 — Example of crack tip monitoring using mechanoluminescence (DCB test)

a) DCB test b) ENF test
Key
1 metal plate
2 adhesive layer
3 CFRTP plate
A ML point reflecting position of crack tip
F load
Figure 5 — Mechanoluminescent (ML) image in raw and contour map in luminance
Key
1 metal plate
2 adhesive layer
3 metal plate
A ML points reflecting crack tip
F load
t time during SLS test
Figure 6 — Example of identifying of fracture origin using mechanoluminescence (SLS test)

7.2  Delamination analysis
During delamination, adhesive failure front in bond line can be identified by using mechanoluminescence
(ML) line on the outside surface of the adherend (see Figure 7). The validity of ML line is additionally
explained to reflect adhesive failure front in bond line in Annex E.
a) DCB test
b) SLS test c) CT test
Key
1 metal plate
2 adhesive layer
3 CFRTP plate
4 plastic plate
A ML line reflect adhesive failure front in bond line
F load
Figure 7 — Example of visualising of fracture process using mechanoluminescence
8 Test report
The test report shall contain at least the following information:
a) a reference to this document, i.e. ISO 8065:2024;
b) the bonding specimen employed;
c) the pre-treatment and post treatment employed;
d) the mechanoluminescent (ML) materials, polymer material employed;
e) the camera used;
f) the recording condition of mechanoluminescence;
g) the conditions of mechanical testing;
...