SIST EN ISO 178:2011
(Main)Plastics - Determination of flexural properties (ISO 178:2010)
Plastics - Determination of flexural properties (ISO 178:2010)
This International Standard specifies a method for determining the flexural properties of rigid (see 3.12) and semi-rigid plastics under defined conditions. A standard test specimen is defined, but parameters are included for alternative specimen sizes for use where appropriate. A range of test speeds is included. The method is used to investigate the flexural behaviour of the test specimens and to determine the flexural strength, flexural modulus and other aspects of the flexural stress/strain relationship under the conditions defined. It applies to a freely supported beam, loaded at midspan (three-point loading test). The method is suitable for use with the following range of materials: - thermoplastic moulding, extrusion and casting materials, including filled and reinforced compounds in addition to unfilled types; rigid thermoplastics sheets; - thermosetting moulding materials, including filled and reinforced compounds; thermosetting sheets.
Kunststoffe - Bestimmung der Biegeeigenschaften (ISO 178:2010)
Diese Internationale Norm legt ein Verfahren zur Ermittlung der Biegeeigenschaften von steifen (siehe
3.12) und halbsteifen Kunststoffen unter definierten Bedingungen fest. Ein genormter Probekörper wird
festgelegt, jedoch sind die Parameter für andere gegebenenfalls anzuwendende Probekörpergrößen
enthalten. Ein Bereich von Prüfgeschwindigkeiten ist enthalten.
1.2 Das Verfahren wird für die Untersuchung des Biegeverhaltens der Probekörper und für die Bestimmung
der Biegefestigkeit, des Biegemoduls und anderer Gesichtspunkte der Biegespannungs-Biegedehnungs-
Beziehung unter den definierten Bedingungen eingesetzt. Es wendet einen frei unterstützten Balken an, der in
der Mitte der Auflagedistanz belastet wird (Dreipunktbiegeversuch).
1.3 Das Prüfverfahren ist zur Anwendung auf folgende Werkstoffgruppen geeignet:
⎯ thermoplastische Formmassen, Extrudiermassen und Gussmassen, einschließlich gefüllter und
verstärkter Compounds in Ergänzung zu den ungefüllten Sorten; steife thermoplastische Platten;
⎯ duroplastische Formmassen, einschließlich gefüllter und verstärkter Compounds; duroplastische Platten.
In Übereinstimmung mit ISO 10350-1 [5] und ISO 10350-2 [6] gilt diese Internationale Norm für
faserverstärkte Compounds mit Faserlängen ≤ 7,5 mm vor der Verarbeitung. In Bezug auf langfaserverstärkte
Werkstoffe (Laminate) mit Faserlängen > 7,5 mm siehe ISO 14125 [7].
Das Verfahren ist üblicherweise nicht für harte Schaumstoffe oder Schicht-Verbundwerkstoffe geeignet, die
Schaumstoffe enthalten. In diesen Fällen kann ISO 1209-1 [3] und/oder ISO 1209-2 [4] angewendet werden.
ANMERKUNG Für bestimmte Sorten textilfaserverstärkter Kunststoffe ist ein Vierpunktbiegeversuch vorzuziehen. Dies
ist in ISO 14125 beschrieben.
Plastiques - Détermination des propriétés en flexion (ISO 178:2010)
L'ISO 178:2010 spécifie une méthode pour la détermination des propriétés en flexion des plastiques rigides et semi-rigides dans des conditions définies. Une éprouvette normalisée est définie, mais des paramètres sont inclus pour d'autres dimensions d'éprouvettes lorsque l'usage est approprié. Une gamme de vitesses d'essai est incluse.
La méthode est utilisée pour l'étude du comportement en flexion des éprouvettes et pour la détermination de la résistance en flexion, du module en flexion et d'autres aspects des relations entre la contrainte et la déformation en flexion dans les conditions définies. Elle s'applique à une poutre supportée sans contrainte, chargée au milieu de sa portée (essai de chargement en trois points).
La méthode est adaptée à la gamme de matériaux suivants:
matériaux thermoplastiques pour moulage, extrusion et coulée, y compris les compositions chargées et renforcées en plus des types non chargés; feuilles thermoplastiques rigides;
matériaux thermodurcissables pour moulage, y compris les compositions chargées et renforcées; feuilles thermodurcissables.
L'ISO 178:2010 s'applique aux compositions renforcées avec des fibres dont les longueurs avant mise en œuvre sont inférieures ou égales à 7,5 mm. Pour les matériaux renforcés de fibres longues (stratifiés) avec des longueurs de fibres supérieures à 7,5 mm, voir l'ISO 14125.
La méthode n'est normalement pas adaptée à l'utilisation de matériaux alvéolaires rigides et de structures sandwichs contenant des matériaux alvéolaires. Dans ces cas, l'ISO 1209-1 et/ou l'ISO 1209-2 peuvent être utilisées.
Contrairement aux éditions précédentes de la présente Norme internationale, la présente édition spécifie deux méthodes, la méthode A et la méthode B. La méthode A est identique à la méthode des éditions précédentes de la présente Norme internationale, c'est-à-dire qu'elle utilise un taux de déformation de 1 %/min durant tout l'essai. La méthode B utilise deux taux de déformation différents, 1 %/min pour la détermination du module en flexion et 5 %/min ou 50 %/min, en fonction de la ductilité du matériau, pour la détermination du reste de la courbe contrainte en flexion-déformation.
Polimerni materiali - Določanje upogibnih lastnosti (ISO 178:2010)
Ta mednarodni standard določa metodo za določanje upogibnih lastnosti trdih (glej točko 3.12) in poltrdih polimernih materialov pod določenimi pogoji. Opredeljen je standardni preskušanec, vendar so vključeni parametri za druge velikosti preskušanca, ki se uporabijo, kjer je to primerno. Vključen je razpon preskusnih hitrosti. Ta metoda se uporablja za preučevanje upogibnega obnašanja preskušanca in za določanje upogibne trdnosti, upogibnih modulov in drugih vidikov razmerja med upogibno napetostjo/raztezkov pod opredeljenimi pogoji. Velja za prosto podprt tram, obremenjen na sredini (tritočkovni obremenitveni preskus). Ta metoda je primerna za uporabo pri naslednjih materialih: – plastomerni materiali za brizganje, materiali za iztiskanje in vlivanje, vključno s polnjenimi in ojačanimi spojinami poleg nepolnjenih vrst; trdi plastomerni trakovi; termoreaktivni materiali za brizganje, vključno s polnjenimi in ojačanimi spojinami; termoreaktivni trakovi.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 178:2011
01-julij-2011
1DGRPHãþD
SIST EN ISO 178:2003
SIST EN ISO 178:2003/A1:2005
3ROLPHUQLPDWHULDOL'RORþDQMHXSRJLEQLKODVWQRVWL ,62
Plastics - Determination of flexural properties (ISO 178:2010)
Kunststoffe - Bestimmung der Biegeeigenschaften (ISO 178:2010)
Plastiques - Détermination des propriétés en flexion (ISO 178:2010)
Ta slovenski standard je istoveten z: EN ISO 178:2010
ICS:
83.080.01 Polimerni materiali na Plastics in general
splošno
SIST EN ISO 178:2011 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 178:2011
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SIST EN ISO 178:2011
EUROPEAN STANDARD
EN ISO 178
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2010
ICS 83.080.01 Supersedes EN ISO 178:2003
English Version
Plastics - Determination of flexural properties (ISO 178:2010)
Plastiques - Détermination des propriétés en flexion (ISO Kunststoffe - Bestimmung der Biegeeigenschaften (ISO
178:2010) 178:2010)
This European Standard was approved by CEN on 14 December 2010.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2010 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 178:2010: E
worldwide for CEN national Members.
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SIST EN ISO 178:2011
EN ISO 178:2010 (E)
Contents Page
Foreword .3
2
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SIST EN ISO 178:2011
EN ISO 178:2010 (E)
Foreword
This document (EN ISO 178:2010) has been prepared by Technical Committee ISO/TC 61 “Plastics” in
collaboration with Technical Committee CEN/TC 249 “Plastics” the secretariat of which is held by NBN.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by June 2011, and conflicting national standards shall be withdrawn at
the latest by June 2011.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 178:2003.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 178:2010 has been approved by CEN as a EN ISO 178:2010 without any modification.
3
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SIST EN ISO 178:2011
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SIST EN ISO 178:2011
INTERNATIONAL ISO
STANDARD 178
Fifth edition
2010-12-15
Plastics — Determination of flexural
properties
Plastiques — Détermination des propriétés en flexion
Reference number
ISO 178:2010(E)
©
ISO 2010
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SIST EN ISO 178:2011
ISO 178:2010(E)
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Published in Switzerland
ii © ISO 2010 – All rights reserved
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SIST EN ISO 178:2011
ISO 178:2010(E)
Contents Page
Foreword .iv
1 Scope.1
2 Normative references.2
3 Terms and definitions .2
4 Principle .5
5 Test machine.5
5.1 General .5
5.2 Test speed.5
5.3 Supports and loading edge .6
5.4 Force- and deflection-measuring systems .6
5.5 Equipment for measuring the width and thickness of the test specimens.7
6 Test specimens.8
6.1 Shape and dimensions .8
6.2 Anisotropic materials.9
6.3 Preparation of test specimens .9
6.4 Specimen inspection.10
6.5 Number of test specimens.10
7 Atmosphere for conditioning and testing.10
8 Procedure.10
9 Calculation and expression of results .13
9.1 Flexural stress .13
9.2 Flexural strain .13
9.3 Flexural modulus.14
9.4 Statistical parameters .14
9.5 Significant figures .14
10 Precision .15
11 Test report.15
Annex A (informative) Precision statement.16
Annex B (informative) Influence of changes in test speed on the measured values of flexural
properties .18
Bibliography.19
© ISO 2010 – All rights reserved iii
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SIST EN ISO 178:2011
ISO 178:2010(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 178 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 2, Mechanical
properties.
This fifth edition cancels and replaces the fourth edition (ISO 178:2001), which has been technically revised to
[2]
harmonize it with ISO 527-2 with respect to the test speeds used for the determination of the flexural
modulus and for the determination of other flexural properties. This has been done by specifying two methods,
method A and method B. Method A is identical to the method specified in previous editions of ISO 178, i.e. it
uses the same strain rate throughout the test, whereas method B uses two different strain rates (see 1.8 for
details).
It also incorporates the Amendment ISO 178:2001/Amd.1:2004.
iv © ISO 2010 – All rights reserved
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SIST EN ISO 178:2011
INTERNATIONAL STANDARD ISO 178:2010(E)
Plastics — Determination of flexural properties
1 Scope
1.1 This International Standard specifies a method for determining the flexural properties of rigid (see 3.12)
and semi-rigid plastics under defined conditions. A standard test specimen is defined, but parameters are
included for alternative specimen sizes for use where appropriate. A range of test speeds is included.
1.2 The method is used to investigate the flexural behaviour of the test specimens and to determine the
flexural strength, flexural modulus and other aspects of the flexural stress/strain relationship under the
conditions defined. It applies to a freely supported beam, loaded at midspan (three-point loading test).
1.3 The method is suitable for use with the following range of materials:
⎯ thermoplastic moulding, extrusion and casting materials, including filled and reinforced compounds in
addition to unfilled types; rigid thermoplastics sheets;
⎯ thermosetting moulding materials, including filled and reinforced compounds; thermosetting sheets.
[5] [6]
In agreement with ISO 10350-1 and ISO 10350-2 , this International Standard applies to fibre-reinforced
compounds with fibre lengths u 7,5 mm prior to processing. For long-fibre-reinforced materials (laminates)
[7]
with fibre lengths > 7,5 mm, see ISO 14125 .
The method is not normally suitable for use with rigid cellular materials or sandwich structures containing
[3] [4]
cellular material. In such cases, ISO 1209-1 and/or ISO 1209-2 can be used.
NOTE For certain types of textile-fibre-reinforced plastic, a four-point bending test is preferred. This is described in
ISO 14125.
1.4 The method is performed using specimens which may be either moulded to the specified dimensions,
machined from the central section of a standard multipurpose test specimen (see ISO 20753) or machined
from finished or semi-finished products, such as mouldings, laminates, or extruded or cast sheet.
1.5 The method specifies the preferred dimensions for the test specimen. Tests which are carried out on
specimens of different dimensions, or on specimens which are prepared under different conditions, can
produce results which are not comparable. Other factors, such as the test speed and the conditioning of the
specimens, can also influence the results.
NOTE Especially for semi-crystalline polymers, the thickness of the oriented skin layer, which is dependent on the
moulding conditions, also affects the flexural properties.
1.6 The method is not suitable for the determination of design parameters but can be used in materials
testing and as a quality control test.
1.7 For materials exhibiting non-linear stress/strain behaviour, the flexural properties are only nominal. The
equations given have been derived assuming linear elastic behaviour and are valid for deflections of the
specimen that are small compared to its thickness. With the preferred specimen (which measures
80 mm × 10 mm × 4 mm) at the conventional flexural strain of 3,5 % and a span-to-thickness ratio, L/h, of 16,
the deflection is 1,5h. Flexural tests are more appropriate for stiff and brittle materials showing small
deflections at break than for very soft and ductile ones.
© ISO 2010 – All rights reserved 1
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SIST EN ISO 178:2011
ISO 178:2010(E)
1.8 Contrary to the previous editions of this International Standard, this edition specifies two methods,
method A and method B. Method A is identical to the method in previous editions of this International
Standard, i.e. it uses a strain rate of 1 %/min throughout the test. Method B uses two different strain rates:
1 %/min for the determination of the flexural modulus and 5 %/min or 50 %/min, depending on the ductility of
the material, for the determination of the remainder of the flexural stress-strain curve.
2 Normative references
The following referenced documents are indispensable for the application 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 293, Plastics — Compression moulding of test specimens of thermoplastic materials
ISO 294-1:1996, Plastics — Injection moulding of test specimens of thermoplastic materials — Part 1: General
principles, and moulding of multipurpose and bar test specimens
ISO 295, Plastics — Compression moulding of test specimens of thermosetting materials
ISO 2602, Statistical interpretation of test results — Estimation of the mean — Confidence interval
ISO 2818, Plastics — Preparation of test specimens by machining
ISO 7500-1, Metallic materials — Verification of static uniaxial testing machines — Part 1:
Tension/compression testing machines — Verification and calibration of the force-measuring system
ISO 9513, Metallic materials — Calibration of extensometers used in uniaxial testing
ISO 10724-1, Plastics — Injection moulding of test specimens of thermosetting powder moulding compounds
(PMCs) — Part 1: General principles, and moulding of multipurpose test specimens
ISO 16012, Plastics — Determination of linear dimensions of test specimens
ISO 20753, Plastics — Test specimens
ISO 23529, Rubber — General procedures for preparing and conditioning test pieces for physical test
methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
test speed
v
rate of relative movement between the specimen supports and the loading edge
NOTE It is expressed in millimetres per minute (mm/min).
3.2
flexural stress
σ
f
nominal stress at the outer surface of the test specimen at midspan
NOTE It is calculated from the relationship given in 9.1, Equation (5), and is expressed in megapascals (MPa).
2 © ISO 2010 – All rights reserved
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SIST EN ISO 178:2011
ISO 178:2010(E)
3.3
flexural stress at break
σ
fB
flexural stress at break of the test specimen (see Figure 1, curves a and b)
NOTE It is expressed in megapascals (MPa).
3.4
flexural strength
σ
fM
maximum flexural stress sustained by the test specimen during a bending test (see Figure 1, curves a and b)
NOTE It is expressed in megapascals (MPa).
3.5
flexural stress at conventional deflection
σ
fc
flexural stress at the conventional deflection, s , defined in 3.7 (see also Figure 1, curve c)
C
NOTE It is expressed in megapascals (MPa).
3.6
deflection
s
distance over which the top or bottom surface of the test specimen at midspan deviates from its original
position during flexure
NOTE It is expressed in millimetres (mm).
3.7
conventional deflection
s
C
deflection equal to 1,5 times the thickness, h, of the test specimen
NOTE 1 It is expressed in millimetres (mm).
NOTE 2 Using a span, L, of 16h, the conventional deflection corresponds to a flexural strain (see 3.8) of 3,5 %.
3.8
flexural strain
ε
f
nominal fractional change in length of an element of the outer surface of the test specimen at midspan
NOTE 1 It is expressed as a dimensionless ratio or a percentage (%).
NOTE 2 It is calculated in accordance with the relationships given in 9.2, Equations (6) and (7).
© ISO 2010 – All rights reserved 3
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SIST EN ISO 178:2011
ISO 178:2010(E)
Curve a Specimen that breaks before yielding.
Curve b Specimen that gives a maximum and then breaks before the conventional deflection, s .
C
Curve c Specimen that neither gives a maximum nor breaks before the conventional deflection, s .
C
Figure 1 — Typical curves of flexural stress, σ , versus flexural strain, ε , and deflection, s
f f
3.9
flexural strain at break
ε
fB
flexural strain at which the test specimen breaks (see Figure 1, curves a and b)
NOTE It is expressed as a dimensionless ratio or a percentage (%).
3.10
flexural strain at flexural strength
ε
fM
flexural strain at maximum flexural stress (see Figure 1, curves a and b)
NOTE It is expressed as a dimensionless ratio or a percentage (%).
3.11
modulus of elasticity in flexure
flexural modulus
E
f
ratio of the stress difference, σ − σ , to the corresponding strain difference, ε (= 0,002 5) − ε (= 0,000 5)
f2 f1 f2 f1
[see 9.3, Equation (9)]
NOTE 1 It is expressed in megapascals (MPa).
NOTE 2 The flexural modulus is only an approximate value of Young's modulus of elasticity.
4 © ISO 2010 – All rights reserved
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SIST EN ISO 178:2011
ISO 178:2010(E)
3.12
rigid plastic
plastic that has a modulus of elasticity in flexure or, if that is not applicable, then in tension, greater than
700 MPa
[1]
[ISO 472 ]
3.13
span between specimen supports
L
distance between the points of contact between the test specimen and the test specimen supports (see
Figure 2)
NOTE It is expressed in millimetres (mm).
3.14
flexural strain rate
r
rate at which the flexural strain (see 3.8) increases during a test
−1 −1
NOTE It is expressed in reciprocal seconds (s ) or percent per second (%⋅s ).
4 Principle
A test specimen of rectangular cross-section, resting on two supports, is deflected by means of a loading edge
acting on the specimen midway between the supports. The test specimen is deflected in this way at a
constant rate at midspan until rupture occurs at the outer surface of the specimen or until a maximum strain of
5 % (see 3.8) is reached, whichever occurs first. During this procedure, the force applied to the specimen and
the resulting deflection of the specimen at midspan are measured.
5 Test machine
5.1 General
The machine shall comply with ISO 7500-1 and ISO 9513 and the requirements given in 5.2 to 5.4.
5.2 Test speed
The test machine shall be capable of maintaining the test speed (see 3.1), as specified in Table 1.
Table 1 — Recommended values of the test speed, v
Test speed, v Tolerance
mm/min %
a
1 ±20
2 ±20
5 ±20
10 ±20
20 ±10
50 ±10
100 ±10
200 ±10
500 ±10
a
The lowest speed is used for specimens with thicknesses between 1 mm
and 3,5 mm (see also 8.5).
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SIST EN ISO 178:2011
ISO 178:2010(E)
5.3 Supports and loading edge
Two supports and a central loading edge shall be arranged as shown in Figure 2. The supports and the
loading edge shall be parallel to within ±0,2 mm over the width of the test specimen.
The radius, R , of the loading edge and the radius, R , of the supports shall be as follows:
1 2
R = 5,0 mm ± 0,2 mm;
1
R = 2,0 mm ± 0,2 mm for test specimen thicknesses u 3 mm;
2
R = 5,0 mm ± 0,2 mm for test specimen thicknesses > 3 mm.
2
The span, L, shall be adjustable.
Key
1 test specimen h thickness of specimen
F applied force l length of specimen
R radius of loading edge L length of span between supports
1
R radius of supports
2
Figure 2 — Position of test specimen at start of test
5.4 Force- and deflection-measuring systems
5.4.1 Force-measuring system
The force-measuring system shall comply with the requirements of class 1 as defined in ISO 7500-1.
5.4.2 Deflection-measuring system
The deflection-measuring system shall comply with the requirements of class 1 as defined in ISO 9513. This
shall be valid over the whole range of deflections to be measured. Non-contact systems may be used
provided they meet the accuracy requirements stated above. The measurement system shall not be
influenced by machine compliance.
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SIST EN ISO 178:2011
ISO 178:2010(E)
When determining the flexural modulus, the deflection-measuring system shall be capable of measuring the
change in deflection to an accuracy of 1 % of the relevant value or better, corresponding to ±3,4 µm for a
support span, L, of 64 mm and a specimen thickness, h, of 4,0 mm (see Figure 3). Other support spans and
specimen thicknesses will lead to different requirements for the accuracy of the deflection-measuring system.
Any deflection indicator capable of measuring deflection to the accuracy specified above is suitable.
NOTE The crosshead displacement includes not only the specimen deflection but also the indentation of the loading
edge and the supports into the specimen and deformation of the machine. The last of these is machine-dependent as well
as load-dependent. Results determined on different types of machine are therefore not comparable.
In general, measurement of crosshead displacement is not suitable for modulus determination unless a
compliance correction is applied.
Key
σ flexural stress
ε flexural strain
s corresponding deflection for a specimen thickness of 4 mm and a span between supports of 64 mm
Figure 3 — Accuracy requirements for determination of flexural modulus
5.5 Equipment for measuring the width and thickness of the test specimens
5.5.1 Rigid materials
5.5.1.1 Specimen thickness
Measure the thickness using a micrometer, at points lying within ±2 mm of the centre of the specimen, in
accordance with ISO 16012, but using a micrometer that has an accuracy of ±0,01 mm as opposed to the
accuracy of ±0,02 mm specified in ISO 16012. The presser foot shall have a flat, circular contact face with a
diameter of W 4 mm and the anvil shall have a spherical contact face of radius 50 mm to avoid errors caused
by misalignment with the test piece.
5.5.1.2 Specimen width
Measure the width in accordance with ISO 16012, using a micrometer that has an accuracy of ±0,02 mm as
specified in ISO 16012. The presser foot shall have either a flat contact face which is circular with a diameter
of 1 mm or a rectangular contact face with the side which will be parallel to the specimen thickness direction
1 mm long.
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SIST EN ISO 178:2011
ISO 178:2010(E)
5.5.2 Flexible materials
Measure the dimensions of the test specimens in accordance with ISO 23529.
6 Test specimens
6.1 Shape and dimensions
6.1.1 General
The dimensions of the test specimens shall comply with the relevant material standard and, as applicable,
with 6.1.2 or 6.1.3. Otherwise, the type of specimen shall be agreed between the interested parties.
6.1.2 Preferred specimen type
The dimensions, in millimetres, of the preferred test specimen are:
length, l: 80 ± 2
width, b: 10,0 ± 0,2
thickness, h: 4,0 ± 0,2
In any one test specimen, the thickness within the central third of the length shall not deviate by more than
2 % from its mean value. The width shall not deviate from its mean value within this part of the specimen by
more than 3 %. The specimen cross section should preferably be rectangular, with no rounded edges, except
as noted in 6.4.
The preferred specimen may be machined from the central part of a multipurpose test specimen complying
with ISO 20753.
6.1.3 Other test specimens
When it is not possible or desirable to use the preferred test specimen, use a specimen with the dimensions
given in Table 2.
NOTE Certain specifications require that test specimens from sheets of thickness greater than a specified upper limit
be reduced to a standard thickness by machining one face only. In such cases, it is conventional practice to place the test
specimen such that the original surface of the specimen is in contact with the two supports and the force is applied by the
central loading edge to the machined surface of the specimen.
Table 2 — Values of specimen width, b, in relation to thickness, h
Dimensions in millimetres
a
Nominal Width, b
thickness, h (±0,5)
1 < h u 3 25,0
3 < h u 5 10,0
5 < h u 10 15,0
10 < h u 20 20,0
20 < h u 35 35,0
35 < h u 50 50,0
a
For materials with very coarse fillers, the minimum width shall be 30 mm.
8 © ISO 2010 – All rights reserved
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SIST EN ISO 178:2011
ISO 178:2010(E)
6.2 Anisotropic materials
6.2.1 In the case of materials having flexural properties that depend on direction, the test specimens shall
be chosen so that the flexural stress will be applied in the same manner and direction as would be
experienced in the end-use application, if known. The relationship between the test specimen and the end-
product envisaged will determine the feasibility of using standard test specimens.
NOTE The position or orientation and the dimensions of the test specimens sometimes have a very significant
influence on the test results.
6.2.2 When the
...
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