ISO 13586:2018
(Main)Plastics — Determination of fracture toughness (GIC and KIC) — Linear elastic fracture mechanics (LEFM) approach
Plastics — Determination of fracture toughness (GIC and KIC) — Linear elastic fracture mechanics (LEFM) approach
This document specifies the principles for determining the fracture toughness of plastics in the crack-opening mode (mode I) under defined conditions. Two test methods with cracked specimens are defined, namely three-point-bending tests and compact-specimen tensile tests in order to suit different types of equipment available or different types of material. The methods are suitable for use with the following range of materials, including their compounds containing short fibres of the length ≤ 7,5 mm: — rigid and semi-rigid thermoplastic moulding, extrusion and casting materials; — rigid and semi-rigid thermosetting moulding and casting materials. In general, short fibre lengths of 0,1 mm to 7,5 mm are known to cause heterogeneity and anisotropy in the crack tip fracture process zone. Therefore, where relevant, Annex B offers some guidelines to extend the application of the same testing procedure, with some reservations, to rigid and semi-rigid thermoplastic or thermosetting plastics containing such short fibres. Certain restrictions on the linearity of the load-displacement diagram, on the specimen width and on the thickness are imposed to ensure validity (see 6.4) since the scheme used assumes linear elastic behaviour of the cracked material and a state of plane strain at the crack tip. Finally, the crack needs to be sharp enough so that an even sharper crack does not result in significantly lower values of the measured properties.
Plastiques — Détermination de la ténacité à la rupture (GIC et KIC) — Application de la mécanique linéaire élastique de la rupture (LEFM)
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 13586
Second edition
2018-08
Plastics — Determination of fracture
toughness (G and K ) — Linear
IC IC
elastic fracture mechanics (LEFM)
approach
Plastiques — Détermination de la ténacité à la rupture (G et K ) —
IC IC
Application de la mécanique linéaire élastique de la rupture (LEFM)
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Test specimens. 4
4.1 Shape and size . 4
4.2 Preparation . 4
4.3 Notching . 5
4.4 Conditioning . 6
5 Testing . 6
5.1 Testing machine . 6
5.2 Load indicator . 6
5.3 Displacement transducer . 6
5.4 Loading rigs . 6
5.5 Displacement correction . 7
5.6 Test atmosphere .10
5.7 Thickness, width and crack length of test specimens .10
5.8 Test conditions .10
6 Expression of results .10
6.1 Determination of F .10
Q
6.2 Provisional result G .11
Q
6.3 Provisional result K .11
Q
6.4 Size criteria and validation of results .11
6.5 Cross-check of results .12
7 Precision .13
8 Test report .13
Annex A (normative) Calibration factors .15
Annex B (informative) Testing of plastics containing short fibres .17
Bibliography .22
Foreword
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This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 2,
Mechanical behaviour.
This second edition cancels and replaces the first edition (ISO 13586:2000), which has been technically
revised. It also incorporates the Amendment ISO 13586:2000/Amd.1:2003, with the introduction of a
new Annex B.
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iv © ISO 2018 – All rights reserved
Introduction
This document is based on a testing protocol developed by the European Structural Integrity Society
(ESIS), Technical Committee 4, Polymers, Polymer Composites and Adhesives, who carried out the
preliminary enabling research through a series of round-robin exercises which covered a range of
material samples, specimen geometries, test instruments and operational conditions. This activity
involved nearly 10 laboratories from different countries. See References [1] and [3].
INTERNATIONAL STANDARD ISO 13586:2018(E)
Plastics — Determination of fracture toughness (G and
IC
K ) — Linear elastic fracture mechanics (LEFM) approach
IC
1 Scope
This document specifies the principles for determining the fracture toughness of plastics in the crack-
opening mode (mode I) under defined conditions. Two test methods with cracked specimens are
defined, namely three-point-bending tests and compact-specimen tensile tests in order to suit different
types of equipment available or different types of material.
The methods are suitable for use with the following range of materials, including their compounds
containing short fibres of the length ≤ 7,5 mm:
— rigid and semi-rigid thermoplastic moulding, extrusion and casting materials;
— rigid and semi-rigid thermosetting moulding and casting materials.
In general, short fibre lengths of 0,1 mm to 7,5 mm are known to cause heterogeneity and anisotropy
in the crack tip fracture process zone. Therefore, where relevant, Annex B offers some guidelines to
extend the application of the same testing procedure, with some reservations, to rigid and semi-rigid
thermoplastic or thermosetting plastics containing such short fibres.
Certain restrictions on the linearity of the load-displacement diagram, on the specimen width and on
the thickness are imposed to ensure validity (see 6.4) since the scheme used assumes linear elastic
behaviour of the cracked material and a state of plane strain at the crack tip. Finally, the crack needs
to be sharp enough so that an even sharper crack does not result in significantly lower values of the
measured properties.
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 527-1, Plastics — Determination of tensile properties — Part 1: General principles
ISO 604, Plastics — Determination of compressive properties
ISO 2818, Plastics — Preparation of test specimens by machining
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 terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:/ /www. iso. org/obp
— IEC Electropedia: available at http:/ /www.e lectropedia. org/
3.1
energy release rate
G
change in the external work δU and strain energy δU of a deformed body due to enlargement of the
ext s
cracked area δA
δU δU
exts
G=−
δA δA
Note 1 to entry: It is expressed in joules per square metre, J/m .
3.2
critical energy release rate
G
IC
value of the energy release rate (3.1) in a precracked specimen under plane-strain loading conditions,
when the crack starts to grow
Note 1 to entry: It is expressed in joules per square metre, J/m .
3.3
stress intensity factor
K
limiting value of the product of the stress σ(r) perpendicular to the crack area at a distance r from the
crack tip and of the square root of 2πr, for small values of r
Kr=limσ × 2πr
()
r→0
Note 1 to entry: It is expressed in Pa × √m.
Note 2 to entry: The term factor is used here because it is common usage, even though the value has dimensions.
3.4
critical stress intensity factor
K
IC
value of the stress intensity factor (3.3) when the crack under load actually starts to enlarge under a
plane-strain loading condition around the crack tip
Note 1 to entry: It is expressed in Pa × √m.
Note 2 to entry: The critical stress intensity factor K of a material is related to its critical energy release rate G
IC IC
by the formula:
GK= E
IC IC
where E is the modulus of elasticity, determined under similar conditions of loading time (up to crack initiation)
and temperature.
In the case of plane-strain conditions:
...
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