ISO 15024:2023
(Main)Fibre-reinforced plastic composites — Determination of mode I interlaminar fracture toughness, GIC, for unidirectionally reinforced materials
Fibre-reinforced plastic composites — Determination of mode I interlaminar fracture toughness, GIC, for unidirectionally reinforced materials
This document specifies a method for the determination of mode I interlaminar fracture toughness (critical energy release rate), GIC, of unidirectional fibre-reinforced plastic composites using a double cantilever beam (DCB) specimen.
Composites plastiques renforcés de fibres — Détermination de la ténacité à la rupture interlaminaire en mode I, GIC, de matériaux composites à matrice polymère renforcés de fibres unidirectionnelles
1.1 La présente Norme internationale spécifie une méthode de détermination de la ténacité à la rupture interlaminaire en mode I (taux de restitution d'énergie critique), GIC, des matériaux composites à matrice polymère renforcés de fibres unidirectionnelles, en utilisant une éprouvette double poutre encastrée (DCB). 1.2 Elle s'applique aux thermoplastiques et thermodurcissables renforcés de fibres de carbone et de fibres de verre.
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INTERNATIONAL ISO
STANDARD 15024
Second edition
2023-02
Fibre-reinforced plastic composites —
Determination of mode I interlaminar
fracture toughness, G , for
IC
unidirectionally reinforced materials
Composites plastiques renforcés de fibres — Détermination de la
ténacité à la rupture interlaminaire en mode I, G , de matériaux
IC
composites à matrice polymère renforcés de fibres unidirectionnelles
Reference number
ISO 15024:2023(E)
© ISO 2023
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ISO 15024:2023(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
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ISO 15024:2023(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 6
5.1 Test machine . 6
5.1.1 General . 6
5.1.2 Speed of testing . 7
5.1.3 Fixture . 7
5.1.4 Load and displacement measurements . 7
5.1.5 Recorder . 7
5.2 Load blocks or piano hinges . 7
5.3 Measuring apparatus . 7
5.4 Travelling microscope (optional) . 7
5.5 Non-adhesive insert film . 7
5.6 Ancillary equipment . 8
6 Test specimen . 8
6.1 Test plate preparation . 8
6.2 Specimen preparation . 8
6.2.1 Preferred specimens . 8
6.2.2 Alternative specimens . 9
6.3 Checking and measurement of the test specimens . 9
6.4 Attachment of loading points . 9
6.5 Measurement of delamination length . 9
7 Number of specimens . .9
8 Conditioning .10
9 Test procedure .10
9.1 Test set-up . 10
9.2 Initial loading . 10
9.3 Re-loading . 11
10 Calculation of G .11
IC
10.1 Interpretation of test results . 11
10.2 Data reduction .12
10.2.1 General .12
10.2.2 Method A: Corrected beam theory (CBT) .12
10.2.3 Method B: Modified compliance calibration (MCC) . 14
10.3 Data sheets, data plots and statistical calculation . 14
11 Precision .18
12 Test report .19
Annex A (normative) Preparation and bonding of the load blocks or piano hinges.21
Annex B (informative) Recommendations for testing .22
Annex C (informative) Recommended test result sheet .25
Annex D (informative) DCB test with flat insert hinge .28
Bibliography .32
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ISO 15024:2023(E)
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, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely 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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions 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.
This second edition cancels and replaces the first edition (ISO 15024:2001), which has been technically
revised.
The main changes are as follows:
— a new double cantilever beam (DCB) has been added [Figure 1 c)].
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
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INTERNATIONAL STANDARD ISO 15024:2023(E)
Fibre-reinforced plastic composites — Determination
of mode I interlaminar fracture toughness, G , for
IC
unidirectionally reinforced materials
1 Scope
This document specifies a method for the determination of mode I interlaminar fracture toughness
(critical energy release rate), G , of unidirectional fibre-reinforced plastic composites using a double
IC
cantilever beam (DCB) specimen.
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 291, Plastics — Standard atmospheres for conditioning and testing
ISO 527-1, Plastics — Determination of tensile properties — Part 1: General principles
ISO 1268 (all parts), Fibre-reinforced plastics — Methods of producing test plates
ISO 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:
Tension/compression testing machines — Calibration and verification of the force-measuring system
ISO 9513, Metallic materials — Calibration of extensometer systems used in uniaxial testing
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
mode I interlaminar fracture toughness
critical energy release rate
G
IC
resistance to the initiation and propagation of a delamination crack in unidirectional fibre-reinforced
polymer matrix composite laminates under mode I opening load
Note 1 to entry: It is measured in joules per square metre.
3.2
mode I crack opening
crack-opening mode due to a load applied perpendicular to the plane of delamination using the double
cantilever beam specimen
Note 1 to entry: The double cantilever beam specimen shown in Figure 1 is shown in Figure 1.
1
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ISO 15024:2023(E)
3.3
NL point
point of deviation from linearity on the load versus displacement trace
Note 1 to entry: As shown in Figure 2.
3.4
VIS point
point of the onset of delamination, as determined by visual observation, at the edge of the specimen,
marked on the load-displacement trace
Note 1 to entry: As shown in Figure 2.
3.5
5 % / MAX point
point which occurs first on loading the specimen between:
a) the point of 5 % increase in compliance (C ) from its initial value (C ); and
5 % 0
b) the maximum load point.
Note 1 to entry: See Figure 2.
3.6
PROP points
points of discrete delamination length increments beyond the tip of the insert or starter crack tip
marked on the load-displacement trace, points where the crack has been arrested being excluded
Note 1 to entry: See Figure 2.
3.7
delamination-resistance curve
R curve
cross-plot of G for initiation and subsequent propagation values for mode I crack opening (3.2) as a
IC
function of delamination length
Note 1 to entry: See Clause 10.
4 Principle
A mode I double cantilever beam (DCB) specimen, as shown in Figure 1, is used to determine G , the
IC
critical energy release rate, or interlaminar fracture toughness, of fibre-reinforced plastic composites.
Figure 1 represents three different loading arrangement for the specimen as following, a) Specimen
loading using load blocks, b) Specimen loading using piano hinges, c) Specimen loading using insert
hinges (see Annex D). The test method is limited to zero-degree unidirectional lay-ups only (see B.1).
Data reduction yields initiation and subsequent propagation values of G for mode I opening fracture
IC
toughness. A delamination-resistance curve, or R curve, is generated by plotting G on the ordinate as a
IC
function of delamination length plotted on the abscissa.
The aim of the test method is to determine initiation values for the composite material tested. Fibre
bridging is observed in a DCB test and it might not be representative of the composite material tested.
Fibre bridging is considered to be the main cause for the observed shape of the R curve, which typically
rises before reaching a roughly constant value of G for long delamination lengths. A crack-opening
IC
load is applied to the DCB specimen, perpendicular to the plane of delamination, through load blocks
or piano hinges under displacement control at a constant rate. The DCB specimen contains a thin, non-
adhesive starter film embedded at the midplane as shown in Figure 3, which is used to simulate an
initial delamination. The specimen is precracked by unloading the DCB specimen immediately after
the first increment of delamination growth from the insert, followed by re-loading. The onset of stable
delamination growth is monitored, and the delamination initiation and propagation readings are
recorded. The R curve is plotted with the initiation values from both the insert and the mode I precrack,
2
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ISO 15024:2023(E)
and with the propagation from the precrack. Under certain prescribed circumstances (see 9.2.7), an
alternative wedge precracking procedure can be used but is not recommended.
a) Specimen loading using load blocks
b) Specimen loading using piano hinges
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ISO 15024:2023(E)
c) Specimen loading using insert hinges
Key
b specimen width
2h specimen thickness
a initial delamination length
0
a total delamination length
A insert length
l specimen length
l distance from the loading pin (or piano hinge axis) to the midplane of the half-beam to which the load block (or
1
piano hinge) is attached
l distance from centre of loading pin (or piano hinge axis) to edge of load block (or piano hinge)
2
l block length
3
H block thickness
1 centres of hinge axis
NOTE 1 Alternative loading arrangements are (a) load blocks and (b) piano hinges.
NOTE 2 The fibre orientation is parallel to the length l.
NOTE 3 Details of DCB test with insert hinges are described in Annex D.
Figure 1 — Geometry for the double cantilever beam (DCB) specimen with a starter
delamination
4
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ISO 15024:2023(E)
Key
X displacement, in millimetres
Y load, in newtons
1 crack initiation followed by unloading
2 crack propagation by re-initiation from the resulting mode I precrack
3 crack propagation markers
4 NL point
5 VIS point
6 MAX point
7 C
0
8 C
5 %
NOTE Figure shows case where 5 % values follow maximum load, and reload curve has been offset 5 mm for
clarity
Figure 2 — Load-displacement curve for a DCB test
5
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ISO 15024:2023(E)
Dimensions in millimetres
Key
1 film insert
2 fibre direction
d margin to allow for initial trimming
Figure 3 — Example of test plate preparation showing the laminate structure, the dimensions
and the position of the film insert
5 Apparatus
5.1 Test machine
5.1.1 General
The testing machine shall be in accordance with the following requirements.
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ISO 15024:2023(E)
5.1.2 Speed of testing
The testing machine shall be capable of maintaining the constant displacement rate required in 9.2.1
and 9.3.1 within a tolerance of ±20 %, as specified in ISO 527-1.
5.1.3 Fixture
The test machine shall be equipped with a fixture to introduce the load to the pins inserted into the
load blocks or with grips to hold the piano hinges. In each case, rotation of the specimen end shall be
allowed. The axis of the load-introduction fixtures shall be aligned with the loading axis of the test
machine.
5.1.4 Load and displacement measurements
The force measurement system shall be in accordance with class 1 as defined in ISO 7500-1. The
displacement measurement shall be in accordance with class 2 of ISO 9513 within the relevant range
used for results determination. Apply machine compliance compensation if the crosshead monitor is
used, to ensure that the required accuracy level is as well achieved under loading conditions.
5.1.5 Recorder
The test machine shall allow the displacement and corresponding load to be measured and recorded,
preferably on a continuous basis.
5.2 Load blocks or piano hinges
Load blocks or piano hinges, as shown in Figure 1, may be used for introducing the load into the
specimen. They shall be at least as wide as the specimen. For the load blocks in Figure 1 a), the maximum
value of l shall be 15 mm. The hole to inset the loading pin shall be at the centre of l .
3 3
5.3 Measuring apparatus
5.3.1 Micrometer, or equivalent, capable of reading to 0,02 mm or less, suitable for measuring the
thickness of the specimen. The micrometer shall have contact faces appropriate to the surface being
measured (i.e. flat faces for flat, polished surfaces and hemispherical faces for irregular surfaces).
5.3.2 Vernier calipers, or equivalent, capable of reading to 0,05 mm or less, for measuring the width
of the specimen.
5.3.3 Linear scale (ruler), with 1 mm divisions, for measuring the specimen length and marking the
edges of the specimen to monitor the delamination crack growth.
5.4 Travelling microscope (optional)
A travelling microscope may be used to measure the delamination length. If used, it shall have a travel
range of 0 mm to 200 mm, have a magnification no greater than × 70 and be readable to 0,05 mm.
5.5 Non-adhesive insert film
A polymer film of thickness not exceeding 13 µm shall be used as a non-adhesive insert. For epoxy
resin matrix composites cured at temperatures below 180 °C, a film of polytetrafluoroethylene (PTFE)
is recommended. For composites cured at temperatures above 180 °C (for example those including
polyimide or bismaleimide thermoplastics), a film of polyimide is recommended (see B.2).
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ISO 15024:2023(E)
5.6 Ancillary equipment
5.6.1 Desiccator, for storing the test specimens after conditioning, including a suitable desiccant
such as silica gel or anhydrous calcium chloride.
5.6.2 Mould release agent. When a polyimide film is used as the non-adhesive insert film, a mould
release agent of the polytetrafluoroethylene (PTFE) type is recommended (see B.2).
5.6.3 Adhesive. A cyanoacrylate adhesive or epoxy adhesive of the two-component room-
temperature-cure type to bond the load blocks or piano hinges to the test specimen (see Annex A).
5.6.4 Solvent. Organic solvent such as acetone or ethanol (see Annex A).
5.6.5 Sandpaper (abrasive paper), with 500 grade grit or finer (see Annex A).
5.6.6 White ink. Water-soluble typewriter correction fluid.
6 Test specimen
6.1 Test plate preparation
A test plate shall first be prepared in accordance with the part of ISO 1268 appropriate to the production
process used. The recommended plate thickness is 3 mm for 60 % by volume carbon-fibre-reinforced
composites and 5 mm for 60 % by volume glass-fibre-reinforced composites.
An even number of unidirectionally aligned layers shall be used (seeB.1). The non-adhesive film insert
shall be placed at laminate mid-thickness during lay-up. The insert shall not exceed 13 µm, in order
to simulate a sharp crack and cause minimum disturbance of the individual plies of the laminate.
Guidelines for the insert material and its preparation are given in B.2.
If a polyimide film is used, the film shall be painted or sprayed with a mould release agent before
insertion into the laminate. The film shall be cut to the proper size for insertion into the laminate
before applying the mould release agent. Mould release agents containing silicone may contaminate
the laminate by migration through the individual layers. Baking of the film will help to prevent silicone
migration within the composite. The film shall be coated and baked twice for 30 min at 130 °C. Care
shall be exercised in handling the film so that the coated layer of release agent is not damaged or
removed from the film.
Figure 3 shows an example of how the test plate can be configured. The positioning of the insert shall
allow for the initial trimming of the test plate.
6.2 Specimen preparation
6.2.1 Preferred specimens
Machine the test specimens from the trimmed test plate, with their longitudinal axes parallel to the
fibre direction in the test plate. Specimens shall be identified to indicate their original position in the
test plate. The specimen configuration and dimensions are illustrated in Figure 1. The dimensions and
tolerances for the preferred specimens are shown in Table 1. Specimen surfaces shall not be machined
to meet the thickness requirement.
The thickness and width of individual specimens shall not vary by more than ±1 % of the mean value
for that type of specimen.
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ISO 15024:2023(E)
Table 1 — Recommended specimen dimensions and tolerances
Unit Carbon fibre Glass fibre Tolerance
Width, b mm 20 20 ±0,5
Minimum length, l mm 125 125 —
Thickness, 2h mm 3 5 ±0,1
6.2.2 Alternative specimens
Other specimen thicknesses may be used, depending on the tensile modulus of elasticity and the
anticipated interlaminar fracture toughness of the specimen. Guidelines for choosing a specimen
thickness that will yield negligible displacement corrections based on the anticipated interlaminar
fracture toughness are given in B.3.
Other specimen widths between 15 mm and 30 mm may be used. Increasing the length of the
specimen is not critical. However, shortening is not recommended because it will reduce the maximum
delamination length that can be investigated and thus yield too few data points for the analysis.
6.3 Checking and measurement of the test specimens
After machining the specimens, check that they are free from twist and warpage, and free from
machining damage. Check that the cut edges are suitably smooth to allow preparation for monitoring
the crack length in accordance with B.4 and B.5.
Measure and record the length, l, of each specimen to the nearest millimetre. Measure the width, b, to
the nearest 0,02 mm at three evenly spaced points along the length. Measure the thickness, 2h, to the
nearest 0,02 mm at these three points along the centreline of the specimen, and at two additional points
near the edge at the middle measurement point, to check for tapering of the specimen.
Record the mean thickness and width of each specimen and check that the values are within the range
given in Table 1. Check also that the variations along the specimen are within the range given in Table 1.
Discard specimens not meeting these requirements.
Measure the length of the insert at both side edges of the specimen. Record the average value, but if
the insert length measurements differ by more than 1 mm on the two edges this shall be noted in the
report. The minimum distance of the tip of each insert edge from the near ends of the load blocks or
piano hinges shall be 45 mm.
6.4 Attachment of loading points
Bond the load blocks or piano hinges for load introduction on the surfaces at the end of the specimen
where the insert has been placed, as shown in Figure 1. The load-introduction fixtures shall be well
aligned with the specimen, and with each other, and held in position with clamps while the adhesive
sets. The requirements for bonding the load blocks or piano hinges given in Annex A shall be followed.
6.5 Measurement of delamination length
For the measurement of the delamination lengths, marks shall be drawn at 5 mm intervals along the
edge of the specimen, extending at least 55 mm beyond of the tip of the insert. Additionally, the first
10 mm and last 5 mm shall be marked at 1 mm intervals.
7 Number of specimens
A minimum number of five specimens shall be tested. Specimens found to be invalid (see 9.3.6) shall be
discarded and new specimens tested in their place.
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ISO 15024:2023(E)
8 Conditioning
The specimens shall be dried using the drying temperature and duration recommended by the resin
supplier. This conditioning shall be performed after bonding of the load blocks or piano hinges. After
conditioning, the specimens may be stored in a desiccator for not more than 24 h before testing.
Conditioning is required to obtain baseline data on test specimens with a uniform moisture content,
because the interlaminar fracture toughness of polymer-matrix composites is sensitive to the amount
of moisture present in the resin. Hence, a dry condition is recommended for this document. Guidelines
for conditioning are given in B.6.
9 Test procedure
9.1 Test set-up
9.1.1 The test shall be performed under standard conditions in accordance with ISO 291 [i.e.
23 °C ± 2 °C, (50 ± 5) % relative humidi
...
DRAFT INTERNATIONAL STANDARD ISO/DIS 15024:2022(E)
ISO/DIS 15024:2022(E)
Style Definition: Heading 1
ISO TC 61/SC 13/WG 2 Style Definition: Heading 2
Style Definition: Heading 3
Secretariat: JISC
Style Definition: Heading 4
Date: 2022-03-07
Style Definition: Heading 5
Fibre-reinforced plastic composites — Determination of mode I interlaminar fracture
toughness, G , for unidirectionally reinforced materials Style Definition: Heading 6
IC
Style Definition: Default Paragraph Font
Style Definition: ANNEX
Style Definition: AMEND Terms Heading
Style Definition: AMEND Heading 1 Unnumbered
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ISO/DIS 15024:2022(E)
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Exactly 11 pt
© ISO 2022
Formatted: Font: 11 pt
Formatted: Section start: Even page
All rights reserved. Unless otherwise specified, or required in the context of its implementation,
no part of this publication may be reproduced or utilized otherwise in any form or by any means,
electronic or mechanical, including photocopying, or posting on the internet or an intranet,
without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
Formatted: Normal, Space Before: 18 pt
Formatted: Font: 9 pt
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ISO/DIS 15024:2022(E)
Formatted: Font: 11 pt
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pt
Contents
Foreword . iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 6
5.1 Test machine . 6
5.2 Load blocks or piano hinges . 7
5.3 Measuring apparatus . 7
5.4 Travelling microscope (optional) . 7
5.5 Non-adhesive insert film . 7
5.6 Ancillary equipment . 7
6 Test specimen . 8
6.1 Test plate preparation . 8
6.2 Specimen preparation . 8
6.4 Attachment of loading points . 9
6.5 Measurement of delamination length . 9
7 Number of specimens . 9
8 Conditioning . 9
9 Test procedure . 10
9.1 Test set-up . 10
9.2 Initial loading . 10
9.3 Re-loading . 10
10 Calculation of G . 11
IC
10.1 Interpretation of test results . 11
10.2 Data reduction . 11
10.3 Data sheets, data plots and statistical calculation . 14
11 Precision . 16
12 Test report . 16
Annex A (normative) Preparation and bonding of the load blocks or piano hinges . 18
Annex B (informative) Recommendations for testing . 19
Annex C (informative) Recommended test result sheet . 22
Annex D (normative) DCB test with flat insert hinge . 25
Formatted: Font: 9 pt
Bibliography . 28
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ISO/DIS 15024:2022(E)
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Formatted: Justified, Space After: 30 pt, Line spacing:
Exactly 11 pt
Formatted: Font: 11 pt
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, governmental and non-governmental, in liaison with ISO, also take part in
the work. ISO collaborates closely 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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions 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.
This second edition cancels and replaces the first edition (ISO 15024:2001), which has been technically
revised.
The main changes are as follows:
— a new double cantilever beam (DCB) is added [Figure 1 c)].
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.
Formatted: Normal, Space Before: 18 pt
Formatted: Font: 9 pt
iv © ISO 2022 – All rights reserved
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DRAFT INTERNATIONAL STANDARD ISO/DIS 15024:2022(E)
Formatted: Left
Fibre-reinforced plastic composites — Determination of mode I
interlaminar fracture toughness, G , for unidirectionally
IC
reinforced materials
1 Scope
This document specifies a method for the determination of mode I interlaminar fracture toughness
(critical energy release rate), GIC, of unidirectional fibre-reinforced plastic composites using a double
cantilever beam (DCB) specimen.
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 291, Plastics — Standard atmospheres for conditioning and testing
ISO 527--1, Plastics — Determination of tensile properties — Part 1: General principles
Formatted: std_docPartNumber
Formatted: std_docTitle, Font: Not Italic
ISO 1268 (all parts), Fibre-reinforced plastics — Methods of producing test plates
Formatted: std_publisher
ISO 4588, Adhesives — Guidelines for the surface preparation of metals
ISO 5893, Rubber and plastics test equipment — Tensile, flexural and compression types (constant rate of
traverse) — Specification
ISO 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part
1: Tension/compression testing machines — Calibration and verification of the force-measuring system
ISO 9513, Metallic materials — Calibration of extensometer systems used in uniaxial testing
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
Formatted: Hyperlink, No underline, English (United
States)
— IEC Electropedia: available at https://www.electropedia.org/
Formatted: Hyperlink, No underline, English (United
States)
3.1
mode I interlaminar fracture toughness
critical energy release rate
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ISO/DIS 15024:2022(E)
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G
IC
Exactly 11 pt
resistance to the initiation and propagation of a delamination crack in unidirectional fibre-reinforced
polymer matrix composite laminates under mode I opening load
Note 1 to entry: It is measured in joules per square metre.
3.2
mode I crack opening
crack-opening mode due to a load applied perpendicular to the plane of delamination using the double
cantilever beam specimen
Note 1 to entry: The double cantilever beam specimen shown in Figure 1 is shown in Figure 1.
Formatted: Don't adjust space between Latin and Asian
text, Don't adjust space between Asian text and
3.3
numbers, Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1
NL point cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left +
point of deviation from linearity on the load versus displacement trace 4.9 cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left
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Note 1 to entry: As shown in Figure 2.
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3.4
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VIS point
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point of the onset of delamination, as determined by visual observation, at the edge of the specimen,
text, Don't adjust space between Asian text and
marked on the load-displacement trace
numbers, Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1
cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left +
Note 1 to entry: As shown in Figure 2.
4.9 cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left
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3.5
text, Don't adjust space between Asian text and
5 % / MAX point
numbers, Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1
point which occurs first on loading the specimen between:
cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left +
4.9 cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left
a) the point of 5 % increase in compliance (C5 %) from its initial value (C0); and
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b) the maximum load point.
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Note 1 to entry: See Figure 2.
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text, Don't adjust space between Asian text and
3.6 numbers, Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1
PROP points cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left +
points of discrete delamination length increments beyond the tip of the insert or starter crack tip 4.9 cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left
marked on the load-displacement trace, points where the crack has been arrested being excluded
Formatted: cite_fig
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Note 1 to entry: See Figure 2.
text, Don't adjust space between Asian text and
numbers, Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1
3.7
cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left +
delamination-resistance curve
4.9 cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left
R curve
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cross-plot of GIC for initiation and subsequent propagation values for mode I crack opening (3.2) as a
function of delamination length
Formatted: cite_sec
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Note 1 to entry: See Clause 10.
text, Don't adjust space between Asian text and
numbers, Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1
cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left +
4.9 cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left
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ISO/DIS 15024:2022(E)
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4 Principle
pt
A mode I double cantilever beam (DCB) specimen, as shown in Figure 1, is used to determine G , the
IC
critical energy release rate, or interlaminar fracture toughness, of fibre-reinforced plastic composites.
Figure 1 represents three different loading arrangement for the specimen as following, a) Specimen
Formatted: cite_fig
loading using load blocks, b) Specimen loading using piano hinges, c) Specimen loading using insert
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hinges (Seesee Annex D). The test method is limited to zero-degree unidirectional lay-ups only (see
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Annex B.1). Data reduction yields initiation and subsequent propagation values of G for mode I
IC
opening fracture toughness. A delamination-resistance curve, or R curve, is generated by plotting GIC on
Formatted: cite_app
the ordinate as a function of delamination length plotted on the abscissa.
The aim of the test method is to determine initiation values for the composite material tested. Fibre
bridging is observed in a DCB test and it might not be representative of the composite material tested.
Fibre bridging is considered to be the main cause for the observed shape of the R curve, which typically
rises before reaching a roughly constant value of GIC for long delamination lengths. A crack-opening load
is applied to the DCB specimen, perpendicular to the plane of delamination, through load blocks or
piano hinges under displacement control at a constant rate. The DCB specimen contains a thin, non-
adhesive starter film embedded at the midplane as shown in Figure 3, which is used to simulate an
initial delamination. The specimen is precracked by unloading the DCB specimen immediately after the
first increment of delamination growth from the insert, followed by re-loading. The onset of stable
delamination growth is monitored, and the delamination initiation and propagation readings are
recorded. The R curve is plotted with the initiation values from both the insert and the mode I precrack,
and with the propagation from the precrack. Under certain prescribed circumstances (see 9.2.7), an
alternative wedge precracking procedure can be used but is not recommended.
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ISO/DIS 15024:2022(E)
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a) Specimen loading using load blocks
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ISO/DIS 15024:2022(E)
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pt
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b) Specimen loading using piano hinges
1
A
a
0
a
l
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ISO/DIS 15024:2022(E)
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c) Specimen loading using insert hinges
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Key
b specimen width l distance from centre of loading pin (or piano hinge axis) to
1
Formatted Table
midplane of the half-beam to which the load block (or piano
hinge) is attached
2h specimen thickness l distance from centre of loading pin (or piano hinge axis) to edge
2
of load block (or piano hinge)
a initial delamination length l block length
0 3 Formatted: Subscript
a total delamination length H block thickness
A insert length 1 centres of hinge axis
l specimen length
NOTE 1 Alternative loading arrangements are (a) load blocks and (b) piano hinges.
NOTE 2 The fibre orientation is parallel to the length l.
NOTE 3 Details of DCB test with insert hinges is described in Annex D.
Figure 1 — — Geometry for the double cantilever beam (DCB) specimen with a starter
delamination
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ISO/DIS 15024:2022(E)
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ISO/DIS 15024:2022(E)
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Key
Y load, in newtons
X displacement, in millimetres
Y load, in newtons
1 crack initiation followed by unloading
2 crack propagation by re-initiation from the resulting mode I precrack
3 crack propagation markers
4 NL point
5 VIS point
6 MAX point
7 C
0
8 C
5 %
NOTE Figure shows case where 5 % values follow maximum load, and reload curve has been offset 5 mm for
clarity
Figure 2 — — Load-displacement curve for a DCB test
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ISO/DIS 15024:2022(E)
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ISO/DIS 15024:2022(E)
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Key
1 film insert
2 fibre direction
d margin to allow for initial trimming
Figure 3 — Example of test plate preparation showing the laminate structure, the dimensions
and the position of the film insert
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ISO/DIS 15024:2022(E)
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5 Apparatus
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5.1 Test machine
5.1.1 General
The testing machine shall be in accordance with the following requirements.
5.1.2 Speed of testing
The testing machine shall be capable of maintaining the constant displacement rate required in 9.2.1
and 9.3.1 within a tolerance of ±20 %, as specified in ISO 527-1.
5.1.3 Fixture
The test machine shall be equipped with a fixture to introduce the load to the pins inserted into the load
blocks or with grips to hold the piano hinges. In each case, rotation of the specimen end shall be
allowed. The axis of the load-introduction fixtures shall be aligned with the loading axis of the test
machine.
5.1.4 Load and displacement measurements
The force measurement system shall be in accordance with class 1 as defined in ISO 7500-1. The
displacement measurement shall be in accordance with class 2 of ISO 9513 within the relevant range
used for results determination. Apply machine compliance compensation if the crosshead monitor is
used, to ensure that the required accuracy level is as well achieved under loading conditions.
5.1.5 Recorder
The test machine shall allow the displacement and corresponding load to be measured and recorded,
preferably on a continuous basis.
5.2 Load blocks or piano hinges
Load blocks or piano hinges, as shown in Figure 1, may be used for introducing the load into the
specimen. They shall be at least as wide as the specimen. For the load blocks in Figure 1 a), the
maximum value of l shall be 15 mm. The hole to inset the loading pin shall be at the centre of l .
3 3
5.3 Measuring apparatus
5.3.1 Micrometer, or equivalent, capable of reading to 0,02 mm or less, suitable for measuring the
thickness of the specimen. The micrometer shall have contact faces appropriate to the surface being
measured (i.e. flat faces for flat, polished surfaces and hemispherical faces for irregular surfaces).
5.3.2 Vernier calipers, or equivalent, capable of reading to 0,05 mm or less, for measuring the width
of the specimen.
5.3.3 Linear scale (ruler), with 1 mm divisions, for measuring the specimen length and marking the
edges of the specimen to monitor the delamination crack growth.
5.4 Travelling microscope (optional)
A travelling microscope may be used to measure the delamination length. If used, it shall have a travel
range of 0 mm to 200 mm, have a magnification no greater than × 70 and be readable to 0,05 mm.
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ISO/DIS 15024:2022(E)
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5.5 Non-adhesive insert film
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A polymer film of thickness not exceeding 13 µm shall be used as a non-adhesive insert. For epoxy resin
matrix composites cured at temperatures below 180 °C, a film of polytetrafluoroethylene (PTFE) is
recommended. For composites cured at temperatures above 180 °C (for example those including
polyimide or bismaleimide thermoplastics), a film of polyimide is recommended (see Annex B.2).
5.6 Ancillary equipment
5.6.1 Desiccator, for storing the test specimens after conditioning, including a suitable desiccant such
as silica gel or anhydrous calcium chloride.
5.6.2 Mould release agent. When a polyimide film is used as the non-adhesive insert film, a mould
release agent of the polytetrafluoroethylene (PTFE) type is recommended (see Annex B.2).
5.6.3 Adhesive. A cyanoacrylate adhesive or epoxy adhesive of the two-component room-
temperature-cure type to bond the load blocks or piano hinges to the test specimen (see Annex A).
Formatted: cite_app
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5.6.4 Solvent. Organic solvent such as acetone or ethanol (see Annex A).
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5.6.5 Sandpaper (abrasive paper), with 500 grade grit or finer (see Annex A).
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5.6.6 White ink. Water-soluble typewriter correction fluid.
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6 Test specimen
6.1 Test plate preparation
A test plate shall first be prepared in accordance with the part of ISO 1268 appropriate to the
production process used. The recommended plate thickness is 3 mm for 60 % by volume carbon-fibre-
reinforced composites and 5 mm for 60 % by volume glass-fibre-reinforced composites.
An even number of unidirectionally aligned layers shall be used (see Annex BseeB.1). The non-adhesive
film insert shall be placed at laminate mid-thickness during lay-up. The insert shall not exceed 13 µm, in
order to simulate a sharp crack and cause minimum disturbance of the individual plies of the laminate.
Guidelines for the insert material and its preparation are given in Annex B.2.
If a polyimide film is used, the film shall be painted or sprayed with a mould release agent before
insertion into the laminate. The film shall be cut to the proper size for insertion into the laminate before
applying the mould release agent. Mould release agents containing silicone may contaminate the
laminate by migration through the individual layers. Baking of the film will help to prevent silicone
migration within the composite. The film shall be coated and baked twice for 30 min at 130 °C. Care
shall be exercised in handling the film so that the coated layer of release agent is not damaged or
removed from the film.
Figure 3 shows an example of how the test plate can be configured. The positioning of the insert shall
allow for the initial trimming of the test plate.
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ISO/DIS 15024:2022(E)
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6.2 Specimen preparation
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6.2.1 Preferred specimens
Machine the test specimens from the trimmed test plate, with their longitudinal axes parallel to the
fibre direction in the test plate. Specimens shall be identified to indicate their original position in the
test plate. The specimen configuration and dimensions are illustrated in Figure 1. The dimensions and
tolerances for the preferred specimens are shown in Table 1. Specimen surfaces shall not be machined
to meet the thickness requirement.
The thickness and width of individual specimens shall not vary by more than ±1 % of the mean value
for that type of specimen.
Table 1 — Recommended specimen dimensions and tolerances
Unit Carbon fibre Glass fibre Tolerance
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Width, b mm 20 20 ±0,5
Minimum length, l mm 125 125 —
Thickness, 2h mm 3 5 ±0,1
6.2.2 Alternative specimens
Other specimen thicknesses may be used, depending on the tensile modulus of elasticity and the
anticipated interlaminar fracture toughness of the specimen. Guidelines for choosing a specimen
thickness that will yield negligible displacement corrections based on the anticipated interlaminar
fracture toughness are given in Annex B.3.
Other specimen widths between 15 mm and 30 mm may be used. Increasing the length of the specimen
is not critical. However, shortening is not recommended because it will reduce the maximum
delamination length that can be investigated and thus yield too few data points for the analysis.
6.3 Checking and measurement of the test specimens
After machining the specimens, check that they are free from twist and warpage, and free from
machining damage. Check that the cut edges are suitably smooth to allow preparation for monitoring
the crack length in accordance with Annex B.4 and Annex B.5.
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Measure and record the length, l, of each specimen to the nearest millimetre. Measure the width, b, to Formatted: Default Paragraph Font
the nearest 0,02 mm at three evenly spaced points along the length. Measure the thickness, 2h, to the
nearest 0,02 mm at these three points along the centreline of the specimen, and at two additional points
near the edge at the middle measurement point, to check for tapering of the specimen.
Record the mean thickness and width of each specimen and check that the values are within the range
given
...
INTERNATIONAL ISO
STANDARD 15024
Second edition
Fibre-reinforced plastic composites —
Determination of mode I interlaminar
fracture toughness, GIC, for
unidirectionally reinforced materials
Composites plastiques renforcés de fibres — Détermination de la
ténacité à la rupture interlaminaire en mode I, GIC, de matériaux
composites à matrice polymère renforcés de fibres unidirectionnelles
PROOF/ÉPREUVE
Reference number
ISO 15024:2022(E)
© ISO 2022
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ISO 15024:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
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Phone: +41 22 749 01 11
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Published in Switzerland
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ISO 15024:2022(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 6
5.1 Test machine . 6
5.1.1 General . 6
5.1.2 Speed of testing . 7
5.1.3 Fixture . 7
5.1.4 Load and displacement measurements . 7
5.1.5 Recorder . 7
5.2 Load blocks or piano hinges . 7
5.3 Measuring apparatus . 7
5.4 Travelling microscope (optional) . 7
5.5 Non-adhesive insert film . 7
5.6 Ancillary equipment . 8
6 Test specimen . 8
6.1 Test plate preparation . 8
6.2 Specimen preparation . 8
6.2.1 Preferred specimens . 8
6.2.2 Alternative specimens . 9
6.3 Checking and measurement of the test specimens . 9
6.4 Attachment of loading points . 9
6.5 Measurement of delamination length . 9
7 Number of specimens . .9
8 Conditioning .10
9 Test procedure .10
9.1 Test set-up . 10
9.2 Initial loading . 10
9.3 Re-loading . 11
10 Calculation of G .11
IC
10.1 Interpretation of test results . 11
10.2 Data reduction .12
10.2.1 General .12
10.2.2 Method A: Corrected beam theory (CBT) .12
10.2.3 Method B: Modified compliance calibration (MCC) . 14
10.3 Data sheets, data plots and statistical calculation . 14
11 Precision .18
12 Test report .19
Annex A (normative) Preparation and bonding of the load blocks or piano hinges.21
Annex B (informative) Recommendations for testing .22
Annex C (informative) Recommended test result sheet .25
Annex D (informative) DCB test with flat insert hinge .29
Bibliography .32
iii
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ISO 15024:2022(E)
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, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely 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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions 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.
This second edition cancels and replaces the first edition (ISO 15024:2001), which has been technically
revised.
The main changes are as follows:
— a new double cantilever beam (DCB) is added [Figure 1 c)].
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
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INTERNATIONAL STANDARD ISO 15024:2022(E)
Fibre-reinforced plastic composites — Determination
of mode I interlaminar fracture toughness, GIC, for
unidirectionally reinforced materials
1 Scope
This document specifies a method for the determination of mode I interlaminar fracture toughness
(critical energy release rate), GIC, of unidirectional fibre-reinforced plastic composites using a double
cantilever beam (DCB) specimen.
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 291, Plastics — Standard atmospheres for conditioning and testing
ISO 527-1, Plastics — Determination of tensile properties — Part 1: General principles
ISO 1268 (all parts), Fibre-reinforced plastics — Methods of producing test plates
ISO 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:
Tension/compression testing machines — Calibration and verification of the force-measuring system
ISO 9513, Metallic materials — Calibration of extensometer systems used in uniaxial testing
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
mode I interlaminar fracture toughness
critical energy release rate
G
IC
resistance to the initiation and propagation of a delamination crack in unidirectional fibre-reinforced
polymer matrix composite laminates under mode I opening load
Note 1 to entry: It is measured in joules per square metre.
3.2
mode I crack opening
crack-opening mode due to a load applied perpendicular to the plane of delamination using the double
cantilever beam specimen
Note 1 to entry: The double cantilever beam specimen shown in Figure 1 is shown in Figure 1.
1
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ISO 15024:2022(E)
3.3
NL point
point of deviation from linearity on the load versus displacement trace
Note 1 to entry: As shown in Figure 2.
3.4
VIS point
point of the onset of delamination, as determined by visual observation, at the edge of the specimen,
marked on the load-displacement trace
Note 1 to entry: As shown in Figure 2.
3.5
5 % / MAX point
point which occurs first on loading the specimen between:
a) the point of 5 % increase in compliance (C ) from its initial value (C ); and
5 % 0
b) the maximum load point.
Note 1 to entry: See Figure 2.
3.6
PROP points
points of discrete delamination length increments beyond the tip of the insert or starter crack tip
marked on the load-displacement trace, points where the crack has been arrested being excluded
Note 1 to entry: See Figure 2.
3.7
delamination-resistance curve
R curve
cross-plot of GIC for initiation and subsequent propagation values for mode I crack opening (3.2) as a
function of delamination length
Note 1 to entry: See Clause 10.
4 Principle
A mode I double cantilever beam (DCB) specimen, as shown in Figure 1, is used to determine G , the
IC
critical energy release rate, or interlaminar fracture toughness, of fibre-reinforced plastic composites.
Figure 1 represents three different loading arrangement for the specimen as following, a) Specimen
loading using load blocks, b) Specimen loading using piano hinges, c) Specimen loading using insert
hinges (see Annex D). The test method is limited to zero-degree unidirectional lay-ups only (see
Annex B.1). Data reduction yields initiation and subsequent propagation values of G for mode I opening
IC
fracture toughness. A delamination-resistance curve, or R curve, is generated by plotting G on the
IC
ordinate as a function of delamination length plotted on the abscissa.
The aim of the test method is to determine initiation values for the composite material tested. Fibre
bridging is observed in a DCB test and it might not be representative of the composite material tested.
Fibre bridging is considered to be the main cause for the observed shape of the R curve, which typically
rises before reaching a roughly constant value of G for long delamination lengths. A crack-opening
IC
load is applied to the DCB specimen, perpendicular to the plane of delamination, through load blocks
or piano hinges under displacement control at a constant rate. The DCB specimen contains a thin, non-
adhesive starter film embedded at the midplane as shown in Figure 3, which is used to simulate an
initial delamination. The specimen is precracked by unloading the DCB specimen immediately after
the first increment of delamination growth from the insert, followed by re-loading. The onset of stable
delamination growth is monitored, and the delamination initiation and propagation readings are
recorded. The R curve is plotted with the initiation values from both the insert and the mode I precrack,
2
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ISO 15024:2022(E)
and with the propagation from the precrack. Under certain prescribed circumstances (see 9.2.7), an
alternative wedge precracking procedure can be used but is not recommended.
a) Specimen loading using load blocks
b) Specimen loading using piano hinges
c) Specimen loading using insert hinges
3
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ISO 15024:2022(E)
Key
b specimen width l distance from centre of loading pin (or piano hinge axis) to
1
midplane of the half-beam to which the load block (or piano
hinge) is attached
2h specimen thickness l distance from centre of loading pin (or piano hinge axis) to
2
edge of load block (or piano hinge)
a initial delamination length l block length
0 3
a total delamination length H block thickness
A insert length 1 centres of hinge axis
l specimen length
NOTE 1 Alternative loading arrangements are (a) load blocks and (b) piano hinges.
NOTE 2 The fibre orientation is parallel to the length l.
NOTE 3 Details of DCB test with insert hinges is described in Annex D.
Figure 1 — Geometry for the double cantilever beam (DCB) specimen with a starter
delamination
4
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ISO 15024:2022(E)
Key
X displacement, in millimetres
Y load, in newtons
1 crack initiation followed by unloading
2 crack propagation by re-initiation from the resulting mode I precrack
3 crack propagation markers
4 NL point
5 VIS point
6 MAX point
7 C
0
8 C
5 %
NOTE Figure shows case where 5 % values follow maximum load, and reload curve has been offset 5 mm for
clarity
Figure 2 — Load-displacement curve for a DCB test
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ISO 15024:2022(E)
Key
1 film insert
2 fibre direction
d margin to allow for initial trimming
Figure 3 — Example of test plate preparation showing the laminate structure, the dimensions
and the position of the film insert
5 Apparatus
5.1 Test machine
5.1.1 General
The testing machine shall be in accordance with the following requirements.
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5.1.2 Speed of testing
The testing machine shall be capable of maintaining the constant displacement rate required in 9.2.1
and 9.3.1 within a tolerance of ±20 %, as specified in ISO 527-1.
5.1.3 Fixture
The test machine shall be equipped with a fixture to introduce the load to the pins inserted into the
load blocks or with grips to hold the piano hinges. In each case, rotation of the specimen end shall be
allowed. The axis of the load-introduction fixtures shall be aligned with the loading axis of the test
machine.
5.1.4 Load and displacement measurements
The force measurement system shall be in accordance with class 1 as defined in ISO 7500-1. The
displacement measurement shall be in accordance with class 2 of ISO 9513 within the relevant range
used for results determination. Apply machine compliance compensation if the crosshead monitor is
used, to ensure that the required accuracy level is as well achieved under loading conditions.
5.1.5 Recorder
The test machine shall allow the displacement and corresponding load to be measured and recorded,
preferably on a continuous basis.
5.2 Load blocks or piano hinges
Load blocks or piano hinges, as shown in Figure 1, may be used for introducing the load into the
specimen. They shall be at least as wide as the specimen. For the load blocks in Figure 1 a), the maximum
value of l shall be 15 mm. The hole to inset the loading pin shall be at the centre of l .
3 3
5.3 Measuring apparatus
5.3.1 Micrometer, or equivalent, capable of reading to 0,02 mm or less, suitable for measuring the
thickness of the specimen. The micrometer shall have contact faces appropriate to the surface being
measured (i.e. flat faces for flat, polished surfaces and hemispherical faces for irregular surfaces).
5.3.2 Vernier calipers, or equivalent, capable of reading to 0,05 mm or less, for measuring the width
of the specimen.
5.3.3 Linear scale (ruler), with 1 mm divisions, for measuring the specimen length and marking the
edges of the specimen to monitor the delamination crack growth.
5.4 Travelling microscope (optional)
A travelling microscope may be used to measure the delamination length. If used, it shall have a travel
range of 0 mm to 200 mm, have a magnification no greater than × 70 and be readable to 0,05 mm.
5.5 Non-adhesive insert film
A polymer film of thickness not exceeding 13 µm shall be used as a non-adhesive insert. For epoxy
resin matrix composites cured at temperatures below 180 °C, a film of polytetrafluoroethylene (PTFE)
is recommended. For composites cured at temperatures above 180 °C (for example those including
polyimide or bismaleimide thermoplastics), a film of polyimide is recommended (see B.2).
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ISO 15024:2022(E)
5.6 Ancillary equipment
5.6.1 Desiccator, for storing the test specimens after conditioning, including a suitable desiccant
such as silica gel or anhydrous calcium chloride.
5.6.2 Mould release agent. When a polyimide film is used as the non-adhesive insert film, a mould
release agent of the polytetrafluoroethylene (PTFE) type is recommended (see B.2).
5.6.3 Adhesive. A cyanoacrylate adhesive or epoxy adhesive of the two-component room-
temperature-cure type to bond the load blocks or piano hinges to the test specimen (see Annex A).
5.6.4 Solvent. Organic solvent such as acetone or ethanol (see Annex A).
5.6.5 Sandpaper (abrasive paper), with 500 grade grit or finer (see Annex A).
5.6.6 White ink. Water-soluble typewriter correction fluid.
6 Test specimen
6.1 Test plate preparation
A test plate shall first be prepared in accordance with the part of ISO 1268 appropriate to the production
process used. The recommended plate thickness is 3 mm for 60 % by volume carbon-fibre-reinforced
composites and 5 mm for 60 % by volume glass-fibre-reinforced composites.
An even number of unidirectionally aligned layers shall be used (seeB.1). The non-adhesive film insert
shall be placed at laminate mid-thickness during lay-up. The insert shall not exceed 13 µm, in order
to simulate a sharp crack and cause minimum disturbance of the individual plies of the laminate.
Guidelines for the insert material and its preparation are given in B.2.
If a polyimide film is used, the film shall be painted or sprayed with a mould release agent before
insertion into the laminate. The film shall be cut to the proper size for insertion into the laminate
before applying the mould release agent. Mould release agents containing silicone may contaminate
the laminate by migration through the individual layers. Baking of the film will help to prevent silicone
migration within the composite. The film shall be coated and baked twice for 30 min at 130 °C. Care
shall be exercised in handling the film so that the coated layer of release agent is not damaged or
removed from the film.
Figure 3 shows an example of how the test plate can be configured. The positioning of the insert shall
allow for the initial trimming of the test plate.
6.2 Specimen preparation
6.2.1 Preferred specimens
Machine the test specimens from the trimmed test plate, with their longitudinal axes parallel to the
fibre direction in the test plate. Specimens shall be identified to indicate their original position in the
test plate. The specimen configuration and dimensions are illustrated in Figure 1. The dimensions and
tolerances for the preferred specimens are shown in Table 1. Specimen surfaces shall not be machined
to meet the thickness requirement.
The thickness and width of individual specimens shall not vary by more than ±1 % of the mean value
for that type of specimen.
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ISO 15024:2022(E)
Table 1 — Recommended specimen dimensions and tolerances
Unit Carbon fibre Glass fibre Tolerance
Width, b mm 20 20 ±0,5
Minimum length, l mm 125 125 —
Thickness, 2h mm 3 5 ±0,1
6.2.2 Alternative specimens
Other specimen thicknesses may be used, depending on the tensile modulus of elasticity and the
anticipated interlaminar fracture toughness of the specimen. Guidelines for choosing a specimen
thickness that will yield negligible displacement corrections based on the anticipated interlaminar
fracture toughness are given in B.3.
Other specimen widths between 15 mm and 30 mm may be used. Increasing the length of the
specimen is not critical. However, shortening is not recommended because it will reduce the maximum
delamination length that can be investigated and thus yield too few data points for the analysis.
6.3 Checking and measurement of the test specimens
After machining the specimens, check that they are free from twist and warpage, and free from
machining damage. Check that the cut edges are suitably smooth to allow preparation for monitoring
the crack length in accordance with B.4 and B.5.
Measure and record the length, l, of each specimen to the nearest millimetre. Measure the width, b, to
the nearest 0,02 mm at three evenly spaced points along the length. Measure the thickness, 2h, to the
nearest 0,02 mm at these three points along the centreline of the specimen, and at two additional points
near the edge at the middle measurement point, to check for tapering of the specimen.
Record the mean thickness and width of each specimen and check that the values are within the range
given in Table 1. Check also that the variations along the specimen are within the range given in Table 1.
Discard specimens not meeting these requirements.
Measure the length of the insert at both side edges of the specimen. Record the average value, but if
the insert length measurements differ by more than 1 mm on the two edges this shall be noted in the
report. The minimum distance of the tip of each insert edge from the near ends of the load blocks or
piano hinges shall be 45 mm.
6.4 Attachment of loading points
Bond the load blocks or piano hinges for load introduction on the surfaces at the end of the specimen
where the insert has been placed, as shown in Figure 1. The load-introduction fixtures shall be well
aligned with the specimen, and with each other, and held in position with clamps while the adhesive
sets. The requirements for bonding the load blocks or piano hinges given in Annex A shall be followed.
6.5 Measurement of delamination length
For the measurement of the delamination lengths, marks shall be drawn at 5 mm intervals along the
edge of the specimen, extending at least 55 mm beyond of the tip of the insert. Additionally, the first
10 mm and last 5 mm shall be marked at 1 mm intervals.
7 Number of specimens
A minimum number of five specimens shall be tested. Specimens found to be invalid (see 9.3.6) shall be
discarded and new specimens tested in their place.
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8 Conditioning
The specimens shall be dried using the drying temperature and duration recommended by the resin
supplier. This conditioning shall be performed after bonding of the load blocks or piano hinges. After
conditioning, the specimens may be stored in a desiccator for not more than 24 h before testing.
Conditioning is required to obtain baseline data on test specimens with a uniform moisture content,
because the interlaminar fracture toughness of polymer-matrix composites is sensitive to the amount
of moisture present in the resin. Hence, a dry condition is recommended for this document. Guidelines
for conditioning are given in B.6.
9 Test procedure
9.1 Test set-up
9.1.
...
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