INTERNATIONAL
`STANDARD
`
`ISO
`178
`
`Sixth edition
`2019-04
`
`Plastics - Determination of flexural
`properties
`Plastiques - Determination des proprietes en flexion
`
`Reference number
`ISO 178:2019(E)
`
`© ISO 2019
`
`ClearCorrect Exhibit 1054, Page 1 of 32
`
`

`

`ISO 178:2019(E)
`
`COPYRIGHT PROTECTED DOCUMENT
`
`© ISO 2019
`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: +4122 749 0111
`Fax: +41 22 749 09 47
`Email: copyright@iso.org
`Website: www.iso.org
`Published in Switzerland
`
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`© ISO 2019 -All rights reserved
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`

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`ISO 178:2019(E)
`
`Page
`
`Contents
`Foreword ........................................................................................................................................................................................................................................ iv
`Scope ................................................................................................................................................................................................................................. 1
`1
`Normative references ...................................................................................................................................................................................... 1
`2
`Terms, definitions and symbols ............................................................................................................................................................ 2
`3
`Principle ........................................................................................................................................................................................................................ 5
`4
`Test machine ............................................................................................................................................................................................................. 5
`5
`General ........................................................................................................................................................................................................... 5
`5.1
`Test speed .................................................................................................................................................................................................... 6
`5.2
`Supports and loading edge ........................................................................................................................................................... 6
`5.3
`Force- and deflection-measuring systems ...................................................................................................................... 6
`5.4
`Introductory remarks .................................................................................................................................................. 6
`5.4.1
`5.4.2 Definition of precision and accuracy requirements .......................................................................... 6
`5.4.3 Deflection measurement ........................................................................................................................................... 8
`Equipment for measuring the width and thickness of the test specimens ......................................... 9
`5.5
`Test specimens ........................................................................................................................................................................................................ 9
`Shape and dimensions ...................................................................................................................................................................... 9
`6.1
`General. ..................................................................................................................................................................................... 9
`6.1.1
`Preferred specimen type ........................................................................................................................................... 9
`6.1.2
`6.1. 3 Other test specimens ................................................................................................................................................. 10
`Anisotropic materials ..................................................................................................................................................................... 10
`Preparation of test specimens ................................................................................................................................................ 11
`From moulding, extrusion and casting compounds ....................................................................... 11
`6.3.1
`From sheets ....................................................................................................................................................................... 11
`6.3.2
`Specimen inspection ....................................................................................................................................................................... 11
`6.4
`Number of test specimens .......................................................................................................................................................... 12
`6.5
`Atmosphere for conditioning and testing ............................................................................................................................... 12
`Procedure .................................................................................................................................................................................................................. 12
`Calculation and expression ofresults .......................................................................................................................................... 16
`Flexural stress ....................................................................................................................................................................................... 16
`9.1
`Flexural strain ....................................................................................................................................................................................... 16
`9.2
`Flexural modulus ............................................................................................................................................ , ................................... 16
`9.3
`Statistical parameters .................................................................................................................................................................... 17
`9.4
`Significant figures .............................................................................................................................................................................. 17
`9.5
`Precision .................................................................................................................................................................................................................... 17
`10
`Test report ................................................................................................................................................................................................................ 17
`11
`Annex A (informative) Precision statement. .............................................................................................................................................. 19
`Annex B (informative) Influence of changes in test speed on the measured values of
`flexural properties ........................................................................................................................................................................................... 21
`Annex C (normative) Compliance correction for Type IIl-tests ............................................................................................. 22
`Annex D (informative) Relation between tensile and flexural modulus: Theoretical
`expectations and experimental observations ..................................................................................................................... 24
`Bibliography ............................................................................................................................................................................................................................. 2 5
`
`6.2
`6.3
`
`6
`
`7
`8
`9
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`ISO 178:2019(E)
`
`Foreword
`
`ISO (the International Organization for Standardization) is a worldwide federation ofnational 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 standardiz;ition.
`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 ofthP. ISO/TEC Directives, Part 2 (see www.iso.org/dircctivcs).
`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 on the voluntary nature of standards, the meaning of ISO specific terms and
`expressions related Lo 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 the following
`URL: www.iso.org/iso/foreword.html.
`This document was prepared by ISO/TC 61, Plastics, Subcommittee SC 2, Mechanical properties.
`This sixth edition cancels and replaces the fifth edition (ISO 178:2010), which has been technically
`revised. It also incorporates the Amendment ISO 178:2010/Amd.1:2013. The main changes compared to
`the previous edition are as follows:
`differentiating calibration requirements according to the type of test;
`the introduction of deflectometers;
`the reinstatement of procedures for compliance correction;
`the addition of a new Annex D showing the relation between tensile and flexural modulus.
`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.
`
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`INTERNATIONAL STANDARD
`
`ISO 178:2019(E)
`
`Plastics - Determination of flexural properties
`
`1 Scope
`This document specifies a method for determining the flexural properties of rigid and semi-rigid
`plastics under defined conditions. A preferred 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.
`In agreement with ISO 10350-1[5.] and ISO 10350-2[.6.], this document applies to fibre-reinforced
`compounds with fibre lengths :,;7,5 mm prior to processing. For long-fibre-reinforced materials
`(laminates) with fibre lengths >7,5 mm, see ISO 14125[1].
`The method is not normally suitable for use with rigid cellular materials or sandwich structures
`containing cellular material. In such cases, ISO 1209-1[1] and/or ISO 1209-2[.±l can be used.
`For certain types of textile-fibre-reinforced plastic, a four-point bending test is used. This is described
`NOTE 1
`in ISO 14125.
`The method is performed using specimens which can 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.
`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.
`Especially for injection moulded semi-crystalline polymers, the thickness of the oriented skin layer,
`NOTE 2
`which is dependent on the moulding conditions, also affects the flexural properties.
`The method is not suitable for the determination of design parameters but can be used in materials
`testing and as a quality control test.
`
`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 293, Plastics - Compression moulding of test specimens of thermoplastic materials
`Injection moulding of test specimens of thermoplastic materials - Part 1:
`ISO 294-1:2017, Plastics -
`General principles, and moulding of multipurpose and bar test specimens
`
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`ISO 178:2019(E)
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`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 - 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
`ISO 10724-1, Plastics -
`Injection moulding of test specimens of thermosetting powder moulding compounds
`(PM Cs) - 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
`
`3 Terms, definitions and symbols
`For the purposes of this document, the following terms and definitions apply.
`ISO and !EC maintain terminological databases for use in standardization at the following addresses:
`ISO Online browsing platform: available at https://www.iso.org/obp
`!EC Electropedia: available at http://www.electropedia.org
`
`3.1
`test speed
`V
`rate ofrelative movement between the specimen supports and the loading edge
`Note 1 to entry: It is expressed in millimetres per minute (mm/min).
`3.2
`flexural stress
`O"f
`nominal stress at the outer surface of the test specimen at midspan
`Note 1 to entry: It is calculated from the relationship given in Formula (5).
`Note 2 to entry: It is expressed in megapascals (MPa).
`3.3
`flexural stress at break
`O"fB
`flexural stress at break of the test specimen
`
`Note 1 to entry: It is expressed in megapascals (MPa).
`
`Note 2 to entry: See Figure 1. curves a and b.
`
`3.4
`flexural strength
`O"fM
`maximum flexural stress (.3..1) sustained by the test specimen during a bending test
`Note 1 to entry: It is expressed in megapascals (MPa).
`
`Note 2 to entry: See Figure 1. curves a and b.
`
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`ISO 178:2019(E)
`
`3.5
`flexural stress at conventional deflection
`Gfc
`flexural stress at the conventional deflection, sc (ll)
`Note 1 to entry: It is expressed in megapascals (MPa).
`
`Note 2 to entry: See also Figure 1. curve c.
`
`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 1 to entry: It is expressed in millimetres (mm).
`
`3.7
`conventional deflection
`sc
`deflection (.3...6) equal to 1,5 times the thickness, h, of the test specimen
`Note 1 to entry: It is expressed in millimetres (mm).
`Note 2 to entry: Using a span, L, of 16h, the conventional deflection corresponds to a flexural strain (3...8.) of 3,5 %.
`
`3.8
`flexural strain
`£f
`nominal fractional change in length of an element of the outer surface of the test specimen at midspan
`Note 1 to entry: It is expressed as a dimensionless ratio or a percentage (%).
`Note 2 to entry: It is calculated in accordance with the relationships given in Formulae (6) and .(Z)..
`
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`ISO 178:2019(E)
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`s -
`
`sc = 1,Sh
`
`Key
`curve a
`curve b
`curve c
`
`specimen that breaks before yielding
`specimen that gives a maximum and then breaks before the conventional deflection, sc
`specimen that neither gives a maximum nor breaks before the conventional deflection, sc
`
`Figure 1-Typical curves of flexural stress, O"f, versus flexural strain, Ef, and deflection, s
`
`3.9
`flexural strain at break
`EfB
`flexural strain at which the test specimen breaks
`Note 1 to entry: It is expressed as a dimensionless ratio or a percentage (%).
`Note 2 to entry: See Figure 1. curves a and b.
`
`3.10
`flexural strain at flexural strength
`EfM
`flexural strain at maximum flexural stress
`
`Note 1 to entry: It is expressed as a dimensionless ratio or a percentage (%).
`Note 2 to entry: See Figure 1. curves a and b.
`3.11
`modulus of elasticity in flexure
`flexural modulus
`Ef
`ratio of
`the
`stress difference, O"f2
`Ef2 (= 0,002 5) - Ef1 (= 0,000 5)
`
`the corresponding strain difference,
`
`an,
`
`to
`
`Note 1 to entry: It is expressed in megapascals (MPa).
`Note 2 to entry: The flexural modulus is only an approximate value of Young's modulus.
`Note 3 to entry: See Formula (9).
`
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`ISO 178:2019(E)
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`3.12
`rigid plastic
`plastic that has a modulus of elasticity in flexure (3.11) or, if that is not applicable, then in tension, greater
`than 700 MPa under a given set of conditions
`[SOURCE: ISO 472:2013, 2.884, modified - Note to entry has been omitted.]
`
`3.13
`semi rigid plastic
`plastic that has a modulus of elasticity in flexure (3.11) or, if that is not applicable, then in tension,
`between 70 MPa and 700 MPa under a given set of conditions
`[SOURCE: ISO 472:2013, 2.909, modified - Note to entry has been omitted.]
`
`3.14
`span between specimen supports
`L
`distance between the points of contact between the test specimen and the test specimen supports
`
`Note 1 to entry: It is expressed in millimetres (mm).
`
`Note 2 to entry: See Figure 2.
`
`3.15
`flexural strain rate
`r
`rate at which the flexural strain (.3....8.) increases during a test
`
`Note 1 to entry: It is expressed in percent per minute(%· min-1).
`
`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.
`This document specifies two methods: method A and method B. Method A 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.
`The strain rates mentioned above are to be interpreted as nominal ones. Nominal test speeds are
`NOTE 1
`calculated using Formula (4) . For the machine settings the best fitting ones are selected from Ia.b.k_l.
`For materials exhibiting nonlinear stress/strain behaviour, the flexural properties are only
`NOTE 2
`nominal. The formulae 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 x 10 mm x 4 mm) at the conventional flexural strain of 3,5 % and a span-to-thickness ratio, L/h, of 16, the
`deflection is 1,Sh. Flexural tests are more appropriate for stiff and brittle materials showing small deflections at
`break than for very soft and ductile ones.
`
`5 Test machine
`
`5.1 General
`The machine shall comply with ISO 7500-1 and ISO 9513 and the requirements given in i l to .5.A.
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`ISO 178:2019(E)
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`5.2 Test speed
`The test machine shall be capable of maintaining the test speed, as specified in Table 1.
`
`Table 1- Recommended values of the test speed, v
`Test speed, v
`Tolerance
`mm/min
`%
`1a
`±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).
`
`5.3 Supports and loading edge
`Two supports and a central loading edge shall be arranged as shown in Figure z". The supports and the
`loading edge shall be parallel to within ±0,2 mm over the width of the test specimen.
`The radius, R1, of the loading edge and the radius, R2, of the supports shall be as follows:
`R1 == 5,0 mm ± 0,2 mm;
`
`R2 == 2,0 mm ± 0,2 mm for test specimen thicknesses s3 mm;
`R2 == 5,0 mm ± 0,2 mm for test specimen thicknesses >3 mm.
`The span, L, shall be adjustable.
`
`5.4 Force- and deflection-measuring systems
`
`5.4.1
`
`Introductory remarks
`Flexural tests, according to the specific requirements on the data to be obtained, can be differentiated in
`several classes, comprising different complexity and requirements on accuracy. This starts with simple
`tests for obtaining flexural strength only on the one hand and on the other hand necessitates the use of
`a deflectometer to obtain the deflection accurately and free of compliance effects of the machine. The
`compliance of flexural testing machines has several possible sources (play and deformations in fixtures,
`deformations in the load train, and deformations of the load cell). Precise and true determination of
`deflection is especially important for the determination of the flexural modulus, for which the use of
`uncorrected crosshead displacement is not suitable. For a repeatable determination of flexural modulus
`results a compliance correction shall be applied or, preferably, a deflectometer shall be used.
`
`5.4.2 Definition of precision and accuracy requirements
`Table 2 defines objectives of testing in increasing order of test complexity and appertaining need for
`accuracy. A good precision without absolute accuracy as indicated in type III-tests can be sufficient in
`many quality control environments when properties are to be supervised over periods of time only.
`Accurate, meaning true and precise, results as indicated in type IV-tests are needed if the results are to
`be compared between laboratories. Differ.ent types of deflection measurement and different accuracy
`
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`

`requirements for the deflection measurement are therefore defined, based on the needs on precision
`and trueness of the test results.
`
`ISO 178:2019(E)
`
`1
`
`3
`
`L/2
`
`L
`
`..r:::
`
`4
`
`2
`
`[ 2 < ~ ~ / 2 ' ]
`
`3
`
`Key
`1
`2
`3
`4
`R1
`
`test specimen
`support base plate
`deflectometer position
`supports
`radius ofloading edge
`
`h
`F
`
`L
`Rz
`
`thickness of specimen
`applied force
`length of specimen
`length of span between supports
`radius of supports
`
`Figure 2 - Position of test specimen and deflectometer at start of test
`
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`ISO 178:2019(E)
`
`Property
`
`Table 2 -Types of tests and calibration requirements
`Types (I-IV)
`of tests in increasing order of complexity and requirements for accuracy
`Required objective Stress/strength only
`Stress/strength/
`Stress/strength/
`Stress/strength/
`of testing
`strains> 1 %
`strains/repeat-
`strains/true and
`able and precise
`precise = accurate
`modulus
`modulus
`III
`IV
`
`I
`
`II
`
`CTfB
`
`CTfM
`
`CTfC
`sc
`
`EfB
`
`EfM
`Et
`
`X
`
`X
`
`X
`
`X
`
`X
`
`X
`
`X
`
`X
`
`Calibration requirement
`
`X
`
`X
`
`X
`
`X
`
`X
`
`X
`
`X
`
`X
`
`X
`
`X
`
`X
`
`X
`
`X
`
`X
`
`Force
`Deflection measure-
`ment
`Type of deflection
`measurement
`
`ISO 7500-1, class 1
`-
`
`-
`
`ISO 9513, Class 2
`
`ISO 9513, Class 2 plus ISO 9513, Class 1 plus
`condition set in 5..4...3. condition set in 5..4...3.
`Crosshead displace- Crosshead displace- Direct measurement
`ment
`ment with compli-
`using a deflectometer
`ance correction
`
`5.4.3 Deflection measurement
`The machine shall be capable of continuously recording the crosshead displacement with an accuracy
`conforming to the class of ISO 9513 indicated in Table 2. 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.
`When determining the flexural modulus as indicated in type IV, the deflection-measuring system, in
`accordance with ISO 9513 Class 1, 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).
`For type III tests the deflection-measuring system, in accordance with ISO 9513 Class 2, shall be
`capable of measuring the change in deflection to an accuracy of 2 % of the relevant value or better,
`corresponding to ±6,8 µm for a support span, L, of 64 mm and a specimen thickness, h, of 4,0 mm.
`Other support spans and specimen thicknesses will lead to different requirements for the accuracy of
`the deflection-measuring system.
`For the determination of the flexural modulus using the crosshead displacement as indicated in Type III,
`the latter shall be corrected for the compliance of the machine. If the machine is equipped with built in
`routines for compliance correction these shall preferably be applied. If such routines are not available,
`the procedure given in Annex C shall be used.
`Annex C also gives some explanation of the possible sources of machine compliance.
`NOTE
`The use of a deflectometer further reduces errors introduced by the test setup and is therefore
`preferred.
`Any deflection indicator capable of measuring deflection to the accuracy specified above is suitable.
`
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`ISO 178:2019(E)
`
`a
`
`l:J.E
`
`b
`<I
`
`/:J.a
`E=-
`l:J.E
`
`0,05%
`
`, .
`
`341µm ± 3,4µm
`
`0, 085mm
`
`.,
`
`0,25%
`
`E
`..
`0,426mm s
`
`Key
`a
`e
`s
`
`flexural stress
`flexural strain
`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
`Use micrometres with an accuracy of ±0,01 mm.
`Use measuring tips that allow to determine the thickness centrally within the measuring range and the
`width at half height as indicated in Figure 5.
`Different geometry of the contact faces of the measuring tips, i.e. circular, rectangular or sharp edges,
`are acceptable. Spherical tip faces shall have a radius <".50 mm. Flat tips are recommended. The face
`diameter of cylindrical measuring tips shall be between 1,5 mm and 6,4 mm. Rectangular faces of
`measuring tips shall have a long side of 4 mm to 6,4 mm length.
`It is recommended to use such a configuration that allows determining the width and the thickness
`with the same instrument.
`
`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,/:
`
`width, b:
`
`80 ± 2
`
`10,0 ± 0,2
`
`thickness, h:
`
`4,0 ± 0,2
`
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`ISO 178:2019(E)
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`In any one test specimen, the thickness within the central one 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 shall preferably be rectangular, with no
`rounded edges, except as explained in the NOTE in 6.4.
`The preferred specimen can be machined from the central part of a multipurpose test specimen
`complying with ISO 20753.
`
`6.1.3 Other test specimens
`If it is not possible or desirable to use the preferred test specimen, use a specimen with the dimensions
`given in Table 3.
`
`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 3 - Values of specimen width, b, in relation to thickness, h
`Dimensions in millimetres
`Nominal thickness
`Width
`h
`ba (±0,5)
`1ShS3
`25,0
`3<hS5
`10,0
`S<hS10
`15,0
`10 < h s 20
`20,0
`20 < h s 35
`35,0
`35 < h s 50
`50,0
`For materials with very coarse fillers, the minimum width shall be 30 mm.
`
`a
`
`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.
`
`© ISO 2019 -All rights reserved
`
`ClearCorrect Exhibit 1054, Page 14 of 32
`
`

`

`6.2.2 When the material shows a significant difference (>20 %) in flexural properties in two principal
`directions, it shall be tested in these two directions. The orientation of the test specimen relative to the
`principal directions shall be recorded (see Figure 4).
`
`ISO 178:2019(E)
`
`Key
`product length direction
`L
`W produ