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INTERNATIONAL ISO
STANDARD 7854
Second edition
1995-08-15

Rubber- or plastics-coated fabrics -

Determination of resistance to darnage
by flexing

Supports textiles rev6tus de caoutchouc ou de plastique - Determination

de Ia rdsistance 2 Ia flexion

Reference number
ISO 7854:1995(E)
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ISO 7854:1995(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. Esch 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
(1EC) on all matters of electrotechnical standardization.

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.

International Standard ISO 7854 was prepared by Technical Committee

ISOJTC 45, Rubber and rubber products.

This second edition cancels and replaces the first edition (ISO 7854:
1984), which has been technically revised.

Annex A of this International Standard is for information only.

0 ISO 1995
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronie or mechanical, including photocopying and
mrcrofilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-l 211 Geneve 20 l Swi tzerlan d
Printed in Switzerland
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0 ISO ISO 7854: 1995(E)

Introduction
Investigation of dynamic-flex fatigue properties of coated fabrics has for
a number of years suffered from poor repeatability (due in part to the un-
known but inevitable variability of the material tested) and worse
reproducibility. Nevertheless, dynamic-flex performante of coated fabrics
has been long and widely used as a measure of the product quality.

The methods traditionally used suffered from the common deficiency of

testing only a small test piece. The De Mattia test is unsuitable for ma-
terials that exhibit “Set”, such as thermoplastics, and the Schildknecht
method has disadvantages when testing the heavier industrial fabrics and
also tends to require very high geometric ratios and consequently time-
consuming tests to verify results. In addition, the mounting of
Schildknecht test pieces tan seriously affect test results and repeatability.

Both the De Mattia and Schildknecht methods are also uni-directional,

which in some cases is advantageous, but in many cases is not appropri-
ate, e.g. where bi-directional Stresses are exerted during use.

This revised edition of ISO 7854 attempts to standardize the mounting

difficulties associated with the Schildknecht apparatus (method B) and in-
troduces a bi-directional flex fatigue test that provides a large test piece,
enabling post-flexing investigations, such as hydrostatic-head tests, to be
conducted. The apparatus is described in ISO 8096-3:1988, Rubber- or
plas tics-cos ted fabrics for wa ter-resis tan t clo thing - Specifica tion -
Part 3: Natura/ rubber- and synthetic rubber-coated fabrics. The apparatus
outlined there in illustrative form (see the note to F.l in annex F of
ISO 8096-3:1988) has been developed in more detail and is now widely
available commercially from a number of sources.

Flex testing tan provide a useful indication of the durability of coated fab-
ries. However, for most applications, flexing conditions induced by these
test methods are dissimilar to the conditions met in practice. In particular,
the micro-climate induced around the test piece and the thermal Stresses
induced in the molecular structure of the coating during flexing are unlikely
to be representative of practical situations. lt is important therefore that
these effects be kept to a minimum and their effect be given due con-
sideration when test results are being considered. Consequently, it is im-
portant to ensure that the air temperature around the test pieces is kept
constant during the test. This tan be achieved either by maintaining ade-
quate non-forced, open Ventilation around the test pieces or by controlling
the air temperature within any closed Container in which the test apparatus
may be mounted.

Three methods are described. Method A (De Mattia) may be found suit-
able for flex testing coated fabrics which cannot be constrained into the
configuration required by method B or where the amount of material
available for testing is too small to permit the other methods to be em-
ployed. Method B (Schildknecht) will be found useful for flex testing
coated fabrics of relatively lightweight construction or whose practical
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ISO 7854: 1995(E) 0 ISO

usage would be in the light to medium range in terms of severity of

flexing.

Method C (crumple/flex test) has been found useful in testing coated

fabrics which will be subject to severe usage in terms of their flexing ca-
pability under arduous conditions. The method requires a large test piece
but this provides certain advantages for selecting test pieces for related
testing after flexing, e.g. hydrostatic-head testing.
Some coated fabrics are more susceptible to delaminat ion when f lexed in
the wet state and attent on IS drawn to the information given in annex A .

Because of the differentes in the nature of the flexing in the three

methods, no true correlation of results between the different methods is
possible.

iv
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INTERNATIONAL STANDARD 0 ISO ISO 7854:1995(E)

Rubber- or plastics-coated fabrics - Determination

of resistance to darnage by flexing

1 Scope tween a pair of flat grips, one of which reciprocates,

causing the folded test piece to be bent outwards five
This International Standard describes three methods times per second. This high-speed folding of the test
of assessing the resistance of coated fabrics to dam- piece is continued for either a pre-set number of cy-
age by repeated flexing. cles or until darnage to the test piece is apparent.

2 Normative references 3.2 Apparatus

The following Standards contain provisions which, 3.21 Flex-testing machine, as specified in
through reference in this text, constitute provisions ISO 132, with pairs of flat grips. One of the grips of
of this lnternational Standard. At the time of publi- each pair is capable of a reciprocating motion in a
cation, the editions indicated were valid. All Standards vertical plane with a stroke length of (57 +it5) mm and
are subject to revision, and Parties to agreements a frequency of 5,0 Hz -+ 0,2 Hz.
based on this International Standard are encouraged
to investigate the possibility of applying the most re- Esch pair of grips is positioned so that they are
cent editions of the Standards indicated below. 70 mm -+ 1 mm apart when in the open Position and
Members of IEC and ISO maintain registers of cur- 13 mm -+ 0,5 mm apart when in the closed Position.
rently valid International Standards.

ISO 132: 1983, Rubber, vulcanized - Determination

3.3 Preparation of test pieces
of flex cracking (De Mattia).
Select six test pieces each 37,5 mm + 1 mm wide x
ISO 1420:1987, Rubber- or plastics-coated fabrics -
125 mm long from the usable width G the roll as de-
Determination of resis tance to pene tra tion by water.
fined in ISO 2286. Three test pieces shall be selected
with their longer dimension in the longitudinal direc-
ISO 2231: 1989, Rubber- or plastics-coated fabrics -
tion of the roll of coated fabric and three test pieces
Standard a tmospheres for conditioning and testing.
with the longer dimension in the transverse direction
ISO 2286: 1986, Rubber- or plastics-coated fabrics - of the roll of coated fabric. Test pieces shall be se-
Determination of roll charac teris tics. lected from positions evenly spaced across the full
width and length of the Sample.

NOTES
3 Method A - De Mattia method
1 In the case of woven-fabric Substrates, as far as possible
no two test pieces should contain the same threads of the
3.1 Principle fabric in the direction to be tested.
A rectangular Strip of coatedfabric is folded twice so 2 Together with suitable increases in the width of grips,
that its long edges meet forming a Strip measuring the test piece size may be increased so as to permit sub-
125 mm x 12,5 mm. This folded Strip is mounted be- sequent hydrostatic-head tests to be conducted.

1
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ISO 7854: 1995(E) 0 ISO

3.4 Conditioning and testing atmosphere or breakdown of the coated fabric is to be deter-
mined, stop the apparatus at predetermined intervals
Condition the test pieces in atmosphere A, B or C of to allow examination sf the test piece.
ISO 22319989, and conduct the test in that atmos-
phere.

3.5 Procedure 3.6 Examination of test pieces

Fold each test piece twice as illustrated in figure 1, Examine the test pieces initially whilst retained in the
with the coating to be tested outermost, along lines grips of the flexing apparatus or, if required, remove
12,5 mm from each of the longer edges and to a the test pieces from the grips for a more detailed in-
width of 12,5 mm. Mount each folded test piece be- spection in accordance with clause 6. Test pieces re-
tween a pair of grips whilst they are in the open pos- moved from the grips shall not be remounted.
ition so that the test piece is slightly taut and so that
the coating on the centre section of the test piece Terminate flexing either at the specified number of
will be subjected to an outward fold. Move the grips cycles or at the first inspection at which test pieces
together by hand and guide each test piece into a fold show signs of deterioration or cracking of the type
at approximately the midpoint (see figure 1). under investigation. Where relevant, record at each
examination the total number of flexes to which the
Set the apparatus in motion and stop it after the test pieces have been subjected and assess the flex-
specified number of cycles or, if the Point of failure ing darnage in accordance with clause 6.

Fold 1
____------------------------------------------------------------------------------

Fold 2
----------------------------------------------------------------------------------

All folded plies to

remain in contact

Figure 1 - Illustration of folding and configuration of test piece for De Mattia method