Bsi bs en 12814 4 2000 (2001)

Li ce ns ed C op y A ki n K ok sa l, B ec ht el L td , 1 2 D ec em be r 20 02 , U nc on tr ol le d C op y, ( c) B S I BRITISH STANDARD BS EN 12814 4 2001 Testing of welded joints of thermoplastic semi[.]

Part 4: Peel test

The European Standard EN 12814-4:2001 has the status of a

British Standard

ICS 83.080.20; 25.160.40

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This British Standard, having

been prepared under the

direction of the Sector Policy

and Strategy Committee for

Materials and Chemicals, was

published under the authority

of the Standards Policy and

Catalogue

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a contract Users of British Standards are responsible for their correct application

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Amendments issued since publication

NORME EUROPÉENNE

ICS 25.160.40

English version

Testing of welded joints of thermoplastics semi-finished products

- Part 4: Peel test

Essai des assemblages soudés sur produits semi-finis en

thermoplastiques - Partie 4: Essai de pelage

Prüfen von Schweißverbindungen aus thermoplastischen

Kunststoffen - Teil 4: Schälversuch

This European Standard was approved by CEN on 16 August 2001.

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 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 Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION

C O M I T É E U R O P É E N D E N O R M A L I S A T I O N

E U R O P Ä I S C H E S K O M I T E E F Ü R N O R M U N G

Management Centre: rue de Stassart, 36 B-1050 Brussels

© 2001 CEN All rights of exploitation in any form and by any means reserved

worldwide for CEN national Members.

Ref No EN 12814-4:2001 E

page

Foreword 3

1 Scope 4

2 Normative references 4

3 Terms and definitions 4

4 Symbols and designations 5

5 Peel test methods 5

6 T-peel test 5

6.1 Principle of the test 5

6.2 Sampling procedures 5

6.3 Dimensions of test specimens 6

6.4 Cutting of test specimens 7

6.5 Mechanical testing 7

6.6 Test equipment 8

6.7 Determination of the peel resistance 8

7 Decohesion test 9

7.1 Principle of the test 9

7.2 Sampling procedure 9

7.3 Conditioning 9

7.4 Preparation of test specimens 9

7.5 Test equipment 12

7.6 Mechanical testing 12

7.7 Calculation of joint toughness 12

8 Crush test 12

8.1 Principle of the test 12

8.2 Sampling procedure 13

8.3 Conditioning 14

8.4 Test equipment 14

8.5 Mechanical testing 14

9 Test report 15

Foreword

This European Standard has been prepared by Technical Committee CEN/TC 249 "Plastics", the secretariat ofwhich is held by IBN

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 March 2002, and conflicting national standards shall be withdrawn at the latest byMarch 2002

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the followingcountries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden,Switzerland and the United Kingdom

1 Scope

This standard specifies the dimensions, the method of sampling, the preparation of the test specimens, and alsothe conditions for performing the peel test perpendicular to the weld in order to determine the peel resistance andthe failure behaviour

A peel test may be used in conjunction with other tests (e.g tensile creep, macro ) to assess the performance ofwelded assemblies, made from thermoplastics materials

Peel tests are applicable to overlap welded assemblies made from thermoplastics materials, irrespective of thewelding process used

2 Normative references

This European Standard incorporates by dated or undated reference, provisions from other publications Thesenormative references are cited at the appropriate places in the text and the publications are listed hereafter Fordated references, subsequent amendments to, or revisions of, any of these publications apply to this standard onlywhen incorporated in it by amendment or revision For undated references the latest edition of the publicationreferred to applies (including amendments)

EN 12814-5, Testing of welded joints of thermoplastics semi-finished products — Part 5 : Macroscopicexamination

EN 13100-1, Non destructive testing of welded joints of thermoplastics semi-finished products — Part 1 : Visualexamination

ISO 5893, Rubber and plastics test equipment — Tensile, flexural and compression types (constant rate oftraverse) — Description

ISO 13954, Plastics pipes and fittings — Peel decohesion test for polyethylene (PE) electrofusion assemblies ofnominal outside diameter greater than or equal to 90 mm

3 Terms and definitions

For the purposes of this European standard, the following term and definition apply

3.1

peel resistance, f

the arithmetic mean of the force values divided by the width of the test specimen (only relevant for T-peel test)

4 Symbols and designations

Symbols and designations are given in Table 1

Table 1 — Test specimen designations Symbols and

abbreviations

an Nominal thickness of test piece millimetre

b Width of the test specimen millimetre

c Maximum width of the air channel (if applicable) millimetre

ci Initial crack size millimetre

Dn Nominal diameter of tube millimetre

Fw Maximum force measured during the test Newton

H Half thickness of decohesion test specimen millimetre

K Apparent toughness mega N.m-3/2

Lc Clamped length of test specimen ligament millimetre

Ld Length of fracture in the fusion plane millimetre

Li Free length of test specimen millimetre

Lwa Maximum width of the weld of the test specimen millimetre

a For welds containing an air channel, L w shall be taken as the width of the whole weld minus thewidth of the channel (c)

5 Peel test methods

Peel tests can be used to assess the performance of overlap joints in both welded sheet and pipe assemblies

For assessing welded sheet assemblies the T-peel test shall be used as defined in clause 6 This test is notapplicable to welded test pieces containing sheets of different nominal thickness

For electrofusion joints with nominal thickness of pipe/fitting greater than 10 mm, a decohesion test shall be used

as defined in ISO 13954 or in clause 7

For socket fusion joints, and for electrofusion joints with nominal outside diameter less than or equal to 90 mm, thecrush test shall be used, as defined in clause 8 The crush test can also be used for electrofusion joints with outsidediameters greater than 90 mm

6 T-peel test

6.1 Principle of the test

The test consists of peeling a test specimen at a constant rate of displacement until it fractures, peels or yields

6.2 Sampling procedures

The welded test specimens shall be cut perpendicular to the welded joint following a lapse of at least eight hoursfrom welding

Each test specimen shall be marked so that its original position in the test piece can be identified.

No heat treatment or mechanical straightening operations shall be carried out on the test specimen

6.3 Dimensions of test specimens

The test specimen is shown in Figure 1 and the dimensions are given in Table 2

Figure 1 — T-peel test specimen

The value of Lcshall be greater than, or equal to, b

Table 2 — Dimensions of test specimen

a For reinforced materials, b shall be 50 mm

The tolerance for b shall be ± 0,5 mm

6.4 Cutting of test specimens

The test specimens shall be cut with parallel sides as shown in Figure 1

During cutting, heating of the test specimen should be avoided

Cutting of the test specimen shall not produce notches

After cutting, a macroscopic examination of the weld should be carried out, according to EN 12814-5

6.5 Mechanical testing

The two unwelded ends of the test specimen shall be bent in opposite directions until each end is perpendicular tothe weld, to form a T-shaped specimen (see Figure 2) for clamping in the jaws of the test equipment Inserting thetest specimen into the test equipment shall not cause cracking at the weld If it does, the test is invalid

Test specimen shall be conditioned to a temperature of (23  2) °C and unless otherwise specified, the test shall becarried out at a room temperature of (2325

 ) °C.

The test speeds for some relevant thermoplastic materials are listed in Table 3

Table 3 — T-peel test speeds for some thermoplastics

For other materials, the test speed shall be agreed between the contracting parties

At least five test specimens shall be tested for each welded test piece

The force shall be measured and recorded with an accuracy of  2 %

1 jaws

2 jaws

Figure 2 — Peel test arrangement

In order to provide additional information, a graph of force versus crosshead displacement may be recorded foreach specimen

6.6 Test equipment

The test equipment shall conform to the requirements given in ISO 5893

The crosshead displacement shall be continuous, uniform and in accordance with Table 3

The test equipment shall be provided with a suitable self-aligning grip to hold the specimen

6.7 Determination of the peel resistance

The peel resistance is the arithmetic mean of the force values, FW, divided by the width of the test specimens, b,i.e

7 Decohesion test

7.1 Principle of the test

A fused socket joint is sectioned at four equidistant positions around the circumference of the fitting and subjected

to a longitudinal peel test, such that the resultant peel should be along the length of the fusion interface Separation

of the joint components is taken to completion and the parted surfaces shall be inspected for evidence of ductileand/or brittle failure along the joint interface

7.2 Sampling procedure

Each test specimen shall be cut from an assembly between a socket and a spigot end of a fitting or a pipe

The number of test specimens tested shall be as specified in the relevant application standard

7.3 Conditioning

Between the welding and machining operations, the test piece shall be conditioned for at least 8 h at the ambienttemperature of (23 ± 2) °C

After machining, the test specimen shall be continuously conditioned at the test temperature

7.4 Preparation of test specimens

Initially standard test specimens shall be used for the decohesion test If the joint cannot be broken, using this testspecimen, a side grooved test specimen shall be used (see 7.4.2)

7.4.1 Preparation of standard test specimens

Following jointing and cooling to (23 ± 2) °C, the welded assembly shall be cut into rectangular sections see

Figure 3

Figure 3 — Cutting test specimens

Test specimens shall be cut, using a bandsaw or equivalent, spaced at equidistant intervals around the jointcircumference The specimen length shall be half the length of the coupler

Test specimen shall not include terminals

To form a flat surface to act as a register for further machining, each test specimen shall be held flat on a linisher orworked with a saw or plane, in order to remove the curvature of the pipe surface see Figure 4

1 Linish/saw

2 Cut rectangular sample

Figure 4 — Preparing test specimen

A bandsaw or similar apparatus shall then be used to produce rectangular test specimens with flat parallel surfaces

1

2

Key

1 Loading pins

2 5 mm diameter holes in samples

Figure 5 — Loading arrangement

The holes shall be located as close to each other as possible

NOTE Standard dimensions are not specified as individual manufacturer's dimensions vary

7.4.2 Preparation of side grooved test specimens

A 5 mm wide side groove shall be machined in the test specimen, using a shaping machine (or similar apparatus)see Figure 6

Figure 6 — Side grooved test specimen

Grooves shall be machined into both faces of the test specimen, penetrating to a quarter of the specimen width.

The joint interface shall lie within the groove

7.5 Test equipment

All tests shall be conducted on a tensile testing machine conforming to the requirements given in ISO 5893

The tensile testing machine shall incorporate a means of providing a permanent record of the force/displacementhistory during the test

7.6 Mechanical testing

The test temperature shall be (23 ± 2) °C

Push fit metal pins shall be placed in the holes drilled in the test specimen and drilled side plates attached whichallow free movement during alignment see Figure 5

The tensile force shall be applied using a cross-head rate of displacement of (25 ± 2,5) mm/min

The test shall be continued until there is complete separation of the test specimen

A force/displacement graph shall be obtained for each test

The maximum force (Fw) obtained during the test shall be recorded

After failure has occurred, the size of the initial "crack" formed by the unfused section and cold zone shall bemeasured using a microscope and recorded

The initial "crack" size (ci) shall be taken as the distance from the centre-line of the loading pin hole to the start ofthe joint This is defined by the presence of first signs of stress whitening due either to the onset of slow crackgrowth or ductile yielding

NOTE Whatever the failure mode, a white zone can always by discerned at the origin of the initial "crack"

The mode of failure shall be recorded by noting the location and length of either brittle crack growth (with no signs

of macro-ductility) or ductile yielding as marked by intense white colouring and/or extensive cold-flow of the plasticmaterial

7.7 Calculation of joint toughness

For each joint tested, a value of the apparent toughness, K, shall be calculated using the equation :

) 38 , 2 46 , 3 (

i 2

/ 3 i w

c

H bH

c F

8.2 Sampling procedure

Each test specimen shall be cut from an assembly between a socket and a spigot end of a fitting or a pipe

Two test specimens shall be cut from each welded assembly An example of a test specimen is shown in Figure 7

The number of test specimens tested shall be as specified in the relevant application standard

5dn

Dimensions in millimetres

Key

1 Vice

Figure 8 — Crush test arrangement

For each test specimen, tests shall be performed on both ends of the socket

NOTE Caution should be taken since the specimen may spring out of the clamps during the test

9 Test report

The test report shall include the following general information :

a) reference to this standard and to the relevant application standard ;

b) description and identification of the test piece and test specimen ;

c) weld type ;

d) the welding conditions for test pieces (if known) ;

>5Dn

>5Dn1

<10

5 (approx)