Paper and board -- Determination of fracture toughness -- Constant rate of elongation method (1,7 mm/s)

ISO/TS 17958:2013 describes a method for determining the fracture toughness of paper and board using a tensile testing machine operated with a constant rate of elongation. ISO/TS 17958:2013 also describes the determination of the fracture strength and fracture strain of a notched paper web with an assigned standard web geometry. This information is used to rank the fracture properties of paper materials. ISO/TS 17958:2013 is applicable to all kinds of paper and paperboard, except for certain special grades, such as creped paper and other paper materials that significantly deviate from exhibiting monotonically decreasing tangential stiffness during tensile testing. ISO/TS 17958:2013 does not apply to corrugated fibreboard.

Papier et carton -- Détermination de la résistance à la rupture -- Méthode à gradient d'allongement constant (1,7 mm/s)

General Information

Status
Published
Publication Date
10-Apr-2013
Current Stage
6060 - International Standard published
Start Date
10-Apr-2013
Completion Date
11-Apr-2013
Ref Project

Buy Standard

Technical specification
ISO/TS 17958:2013 - Paper and board -- Determination of fracture toughness -- Constant rate of elongation method (1,7 mm/s)
English language
16 pages
sale 15% off
Preview
sale 15% off
Preview

Standards Content (sample)

TECHNICAL ISO/TS
SPECIFICATION 17958
First edition
2013-04-15
Paper and board — Determination of
fracture toughness — Constant rate of
elongation method (1,7 mm/s)
Papier et carton — Détermination de la résistance à la rupture —
Méthode à gradient d’allongement constant (1,7 mm/s)
Reference number
ISO/TS 17958:2013(E)
ISO 2013
---------------------- Page: 1 ----------------------
ISO/TS 17958:2013(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2013

All rights reserved. Unless otherwise specified, 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
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2013 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TS 17958:2013(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 3

5 Apparatus ..................................................................................................................................................................................................................... 3

6 Calibration and adjustment of apparatus .................................................................................................................................. 5

7 Sampling and preparation of test pieces ..................................................................................................................................... 5

7.1 Sampling ....................................................................................................................................................................................................... 5

7.2 Conditioning .............................................................................................................................................................................................. 5

7.3 Determination of grammage ....................................................................................................................................................... 6

7.4 Preparation of test pieces for tensile testing ................................................................................................................ 6

7.5 Preparation of test pieces for fracture toughness testing .................................................................................. 6

8 Procedure..................................................................................................................................................................................................................... 6

8.1 Tensile testing .......................................................................................................................................................................................... 6

8.2 Fracture toughness testing ........................................................................................................................................................... 6

9 Calculations................................................................................................................................................................................................................ 7

9.1 General ........................................................................................................................................................................................................... 7

9.2 Tensile testing and evaluation of tensile properties ............................................................................................... 7

9.3 Fracture toughness testing and evaluation of fracture toughness ............................................................. 8

9.4 Determination of ISO fracture strength and ISO fracture strain .................................................................. 9

9.5 Indexed parameters .........................................................................................................................................................................11

10 Report ...........................................................................................................................................................................................................................11

Annex A (normative) Uncertainty determination ...............................................................................................................................13

Bibliography .............................................................................................................................................................................................................................16

© ISO 2013 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/TS 17958:2013(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. 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. 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.

The committee responsible for this document is ISO/TC 6, Paper, board and pulps, Subcommittee SC 2,

Test methods and quality specifications for paper and board.
iv © ISO 2013 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/TS 17958:2013(E)
Introduction

The essence of fracture mechanics theory is that the material parameter fracture toughness is determined

by controlled laboratory testing before it is used to predict the fracture properties of structures or

structural components containing defects. This Technical Specification describes a laboratory test

method for determination of the fracture toughness of paper materials and a numerical method to

predict the fracture strength and fracture strain of notched paper webs for a given reference paper

web geometry called ISO paper web geometry. The specified methods are based on nonlinear fracture

[1] [2] [3]
mechanics theory (J-integral theory).

The experimental procedure for determining the fracture toughness of this Technical Specification

consists of two material tests: tensile testing and fracture toughness testing. Both these tests are

performed following ISO 1924-3, with the exception that 50 mm wide test pieces containing 20 mm-

wide centre notches are used in the fracture toughness test.

For material ranking and material development purposes, it is advantageous to define a notched

reference geometry for predictions of fracture strength (stress at break) and fracture strain (strain at

break). Such notched reference geometry makes it easier to compare fracture properties of different

paper materials and to communicate results in reports and articles. The main application of fracture

mechanics to paper materials is related to breaks in continuous web handling operations, such as in

manufacture, winding, and printing. The characteristic dimensions of paper webs in such operations

generally are in the order of metres, while defects in the paper webs commonly have a characteristic

size in the order of millimetres. Furthermore, the most severe defects from a web break perspective

are located in the region of the edges of the paper web. In this Technical Specification, a 2 m long and

1 m wide paper web, containing a 10 mm edge notch, is used as the notched ISO paper web geometry

for predicting and ranking of the fracture properties of paper materials. The terms ISO fracture

strength and ISO fracture strain are used to indicate that the fracture properties are determined for

this particular notched ISO paper web geometry following this Technical Specification. A successful

experimental validation of the procedure for determining the fracture properties for the assigned ISO

[1] [2] [3]
web geometry has been performed.

NOTE 1 The determined fracture toughness may also be utilized to predict fracture properties of paper webs

and paper products that have different dimensions and shapes than the introduced ISO paper web geometry. The

procedure for such predictions is given in References [1], [2], and [3].

NOTE 2 The fracture toughness alone does not constitute sufficient information to determine the fracture

behaviour of structures or structural components. Consider the stress/strain curves for two materials, A

and B, obtained by tensile testing of notched test pieces (see Figure 1). The exemplified materials have equal

fracture toughness but different fracture strengths and fracture strains. Materials A and B, which have different

stress/strain behaviours, could for instance originate from machine direction (MD) and cross-machine direction

(CD) of a particular paper grade or could be two papers of different origin. Clearly, materials A and B are expected

to behave very differently in converting operations, although they have equal fracture toughness. This example

illustrates that the fracture toughness cannot be used to rank the fracture properties of papers that show different

stress/strain behaviour. However, the ISO fracture strength and ISO fracture strain, according to this Technical

Specification, can be used to accurately rank the fracture properties of materials A and B.

© ISO 2013 – All rights reserved v
---------------------- Page: 5 ----------------------
ISO/TS 17958:2013(E)

Figure 1 — Stress/strain curves for two materials, A and B, obtained by tensile testing of

notched test pieces
vi © ISO 2013 – All rights reserved
---------------------- Page: 6 ----------------------
TECHNICAL SPECIFICATION ISO/TS 17958:2013(E)
Paper and board — Determination of fracture toughness —
Constant rate of elongation method (1,7 mm/s)
1 Scope

This Technical Specification describes a method for determining the fracture toughness of paper and

board using a tensile testing machine operated with a constant rate of elongation. This Technical

Specification also describes the determination of the fracture strength and fracture strain of a notched

paper web with an assigned standard web geometry. This information is used to rank the fracture

properties of paper materials.

This Technical Specification is applicable to all kinds of paper and paperboard, except for certain special

grades, such as creped paper and other paper materials that significantly deviate from exhibiting

monotonically decreasing tangential stiffness during tensile testing. This Technical Specification does

not apply to corrugated fibreboard.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 186, Paper and board — Sampling to determine average quality

ISO 187, Paper, board and pulps — Standard atmosphere for conditioning and testing and procedure for

monitoring the atmosphere and conditioning of samples
ISO 536, Paper and board — Determination of grammage

ISO 1924-3, Paper and board — Determination of tensile properties — Part 3: Constant rate of elongation

method (100 mm/min)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
tensile stiffness

maximum slope of the curve obtained when tensile force per unit width is plotted versus strain

[SOURCE: ISO 1924-3:2005, definition 3.8]
3.2
tensile strength

maximum tensile force per unit width that paper and board will withstand before breaking under the

conditions defined in this Technical Specification
[SOURCE: ISO 1924-3:2005, definition 3.1]
© ISO 2013 – All rights reserved 1
---------------------- Page: 7 ----------------------
ISO/TS 17958:2013(E)
3.3
tensile energy absorption

amount of energy per unit surface area (test length × width) of a test piece when it is strained to the

maximum tensile force
[SOURCE: ISO 1924-3:2005, definition 3.6]
3.4
strain at break
strain at the maximum tensile force
[SOURCE: ISO 1924-3:2005, definition 3.5]
3.5
strain-hardening exponent

mathematically determined exponent describing the non-linear part of the stress/strain curve of the

test material
Note 1 to entry: The strain–hardening exponent is dimensionless.
3.6
strain-hardening modulus

mathematically determined modulus describing the non-linear part of the stress/strain curve of the

test material

Note 1 to entry: The strain–hardening modulus is expressed in newtons per metre (N/m).

3.7
apparent tensile strength
tensile strength of the centre-notched fracture toughness test piece

Note 1 to entry: The apparent tensile strength is reported in newtons per metre (N/m).

3.8
apparent strain at break
strain at break of the centre-notched fracture toughness test piece

Note 1 to entry: The apparent strain at break is dimensionless and usually reported as a percentage.

3.9
fracture toughness

energy release rate at structural instability of notched paper or board panels under in-plane tensile loading

3.10
ISO fracture strength
ISO

tensile strength of the edge-notched ISO paper web geometry used in this Technical Specification

2 © ISO 2013 – All rights reserved
---------------------- Page: 8 ----------------------
ISO/TS 17958:2013(E)
3.11
ISO fracture strain
ISO

strain at break of the edge-notched ISO paper web geometry used in this Technical Specification

4 Principle

Two different kinds of test pieces, un-notched and notched, of given dimensions are subjected to

constant rate of elongation using a tensile testing machine recording the tensile force and elongation.

From the recorded data of the un-notched test pieces, the tensile strength, strain at break, tensile energy

absorption, and tensile stiffness are determined. From the recorded data of the notched test pieces,

the apparent tensile strength and apparent strain at break are determined. The parameters of the un-

notched test pieces in combination with the parameters of the notched test pieces are used to calculate

the fracture toughness of the material. The required calculations are treated in Clause 9.

5 Apparatus

5.1 Tensile testing machine, as described in ISO 1924-3. The tensile testing machine shall be capable

of testing both 15 mm wide and 50 mm wide test pieces.

5.2 Anti-buckling guide, used to keep the notched region of the fracture toughness test piece flat

during the fracture toughness test. The anti-buckling guide shall consist of two supports with parallel,

flat, smooth low-friction surfaces, preferably made of steel or aluminium that shall cover the total width

of the test piece and a length of 15 mm on each side of the notch. A compression force of (0,6 ± 0,2) N

shall be applied to the fracture toughness test piece by the supports, before the separation of the supports

is fixed. The fixed separation of the supports shall then be retained during the reminder of the fracture

toughness test.

One possible solution to prevent out-of-plane buckling of the fracture toughness test piece is shown in

Figure 2. The paper test piece (1) is placed between a stationary upper support (2) and a movable lower

support (3). The lower support, which is free to slide vertically on roller bearings (7), is brought into

contact with the test piece. The specified compression force is applied by the spring (5) to the paper test

piece via the lower support. The position of the lower support is then fixed by the pneumatic cylinder

(4) via the thin metal blade (6).
© ISO 2013 – All rights reserved 3
---------------------- Page: 9 ----------------------
ISO/TS 17958:2013(E)
Key
1 paper test piece
2 upper support
3 lower support
4 pneumatic cylinder
5 spring
6 thin metal blade
7 roller bearings
Figure 2 — Illustration of one possible solution to achieve anti-buckling

5.3 Computer, means for numerical calculation of fracture toughness and predictions of fracture

strength and fracture strain, in accordance with the formulae given in this Technical Specification.

5.4 Cutting device(s), used for cutting tensile and fracture toughness test pieces. The cutting device(s)

shall be able to cut (15 ± 0,1) mm wide tensile test pieces and (50 ± 0,1) mm wide fracture toughness

...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.