Bsi bs en 02155 21 1989 (2000)

BRITISH STANDARD AEROSPACE SERIES

Test methods for
transparent materials
for aircraft glazing —
Part 21: Determination of resistance to
crack propagation (K factor)

This European Standard EN 2155-2 has the status of a
British Standard.

UDC 629.73.023.26:620.191.33

BS EN
2155-21:1989


BS EN 2155-21:1989

Cooperating organizations
The European Committee for Standardization, under whose supervision this
European Standard was prepared, comprises the national standards
organizations of the following Western European countries.
Austria
Belgium
Denmark
Finland
France
Germany
Greece
Iceland

Ireland
Italy
Luxemburg
Netherlands
Norway
Portugal
Spain
Sweden
Switzerland
United Kingdom

This British Standard, having
been prepared under the
direction of the Aerospace
Standards Policy Committee,
was published under the
authority of the Board of BSI
and comes into effect on
31 October 1989
© BSI 01-2000
The following BSI references
relate to the work on this
standard:
Committee reference ACE/62
Draft for comment 88/70404 DC

ISBN 0 580 17926 5

Oesterreichisches Normungsinstitut
Institut belge de normalisation

Dansk Standardiseringsraad
Suomen Standardisoimisliito, r.y.
Association franỗaise de normalisation
Deutsches Institut für Normung e.V.
Hellenic Organization for Standardization
Icelandic Council for Standardization
National Standards Authority of Ireland
Ente Nazionale Italiano di Unificazione
Inspection des travails et des mines
Nederlands Normalisatie-instituut
Norges Standardiseringsforbund
Instituto Português da Qualidade
Instituto Español de Normalización
Standardiseringskommissionen i Sverige
Association suisse de normalisation
British Standards Institution

Amendments issued since publication
Amd. No.

Date of issue

Comments


BS EN 2155-21:1989

Contents
Cooperating organizations
National foreword

Brief history
Text of EN 2155-21
National appendix A

© BSI 01-2000

Page
Inside front cover
ii
2
3
Inside back cover

i


BS EN 2155-21:1989

National foreword
This British Standard has been prepared under the direction of the Aerospace
Standards Policy Committee and is the English language version of
EN 2155 “Aerospace series. Test methods for transparent materials for aircraft
glazing” Part 21 “Determination of resistance to crack propagation (K factor)”
published by the European Committee for Standardization (CEN). EN 2155-21
was produced as a result of international discussion in which the UK took an
active part.
A British Standard does not purport to include all the necessary provisions of a
contract. Users of British Standards are responsible for their correct application.

Compliance with a British Standard does not of itself confer immunity

from legal obligations.

Summary of pages

This document comprises a front cover, an inside front cover, pages i and ii,
the EN title page, pages 2 to 6, an inside back cover and a back cover.
This standard has been updated (see copyright date) and may have had
amendments incorporated. This will be indicated in the amendment table on the
inside front cover.
ii

© BSI 01-2000


EN 2155-21

EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM

March 1989

UDC: 629.73.023.26:620.191.33
Key words: Aircraft industry, glazing, transparent plastics, glass, tests, strength, crack propagation

English version

Aerospace series
Test methods for transparent materials
for aircraft glazing

Part 21: Determination of resistance
to crack propagation (K factor)
Luft- und Raumfahrt
Prüfverfahren für transparente Werkstoffe
zur Verglasung von Luftfahrzeugen
Teil 21: Bestimmung des
Ri¶fortpflanzungswiderstandes (K-Faktor)

Série ắrospatiale
Méthodes d’essais pour matériaux
transparents pour vitrages aéronautiques
Partie 21: Détermination de la résistance
à la propagation des criques (Facteur K)

This European Standard was accepted by CEN on 1988-03-17. CEN members
are bound to comply with the requirements of CEN 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 Central Secretariat 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 CEN
Central Secretariat has the same status as the official versions.
CEN members are the national standards organizations of Austria, Belgium,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy,
Luxemburg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and
United Kingdom.

CEN
European Committee for Standardization
Comité Européen de Normalisation
Europäisches Komitee für Normung

Central Secretariat: rue de Stassart 36, B-1050 Brussels
© CEN 1989 Copyright reserved to all CEN members

Ref. No. EN 2155-21:1989 E


EN 2155-21:1989

Brief history
This European Standard has been prepared by the
European Association of Aerospace Manufacturers
(AECMA).
After enquiries and votes carried out in accordance
with the rules of this Association, this Standard has
successively received the approval of the National
Associations and the Official Services of the member
countries of AECMA, prior to its presentation to
CEN.
According to the Common CEN/CENELEC Rules,
following countries are bound to implement this
European Standard: Austria, Belgium, Denmark,
Finland, France, Germany, Greece, Iceland,
Ireland, Italy, Luxemburg, Netherlands, Norway,
Portugal, Spain, Sweden, Switzerland and the
United Kingdom.

2

Contents
Brief history
1
Scope and field of application
2
Definitions
3
Apparatus
4
Specimens
5
Conditioning
6
Procedure
7
Expression of results
8
Test report
Figure 1 — Driving yoke and blade for
initiating cracks in toughness specimens
Figure 2 — Toughness specimen
Figure 3 — The fracture zones on
a failed specimen
Table 1 — Values of Z

Page
2

3
3
3
3
3
3
3
4
4
5
5
6

© BSI 01-2000


EN 2155-21:1989

1 Scope and field of application

This standard specifies how the resistance to crack
propagation of rigid transparent sheet is to be
determined.
2 Definitions

Resistance to crack propagation is defined either by
fracture toughness K at failure, or by strain energy
¹W
release rate ¹ A at failure.
The values of failing load and length of crack at fast

fracture shall be determined by tensile tests with a
specified constant rate loading using a pre-cracked
standard specimen.
3 Apparatus
3.1 A tensile testing machine shall be provided such
that the specimen can be loaded at a constant rate
which will cause fracture in 3 to 5 min.
3.2 Suitable grips shall be provided on this machine
of sufficient width to grip the specimen i.e. at
least 50 mm in width. Self-tightening wedge grips
have been found suitable but great care shall be
taken to avoid damaging the specimen.
3.3 A driving yoke and blade for initiating cracks in
the specimens shall be provided to the dimensions
as illustrated in Figure 1.

4 Specimens

Test specimens shall conform to Figure 2. The
specimen’s width shall be measured to the
nearest 0,2 mm and their thickness at the centre
shall be measured to the nearest 0,02 mm. Five
specimens shall be cut from each sample.
5 Conditioning
5.1 For testing at (23 ± 2) ° C, (50 ± 5) % relative
humidity the specimens shall be conditioned for at
least 48 h at this condition prior to testing.
5.2 For testing at (– 18 ± 1) ° C the specimens shall
be conditioned at this temperature for at
least 30 min prior to testing.

6 Procedure

The distance between the heads of the initial cracks
shall be between 12,5 mm and 25,0 mm so that the
crack length at the point of instability will be
between 1/4 and 1/2 of the specimen width. In
initiating the cracks, the following procedure is
recommended. A fine slot, approximately 0,8 mm
deep is made with a jeweller’s saw. The driving yoke
and blade shown in the Figure 1 are employed in
initiating the cracks.
With the specimen held firmly in a vertical position
with its length horizontal, the blade is inserted
through the central hole and seated in the saw cut.
The yoke straddles the specimen and engages the
blade in the squared notches.
A light hammer tapping on the yoke is used to
initiate the crack.
Cracks shall be initiated under conditions of
conditioning according to clause 5.1 for testing
under these conditions. For low temperature
testing, cracks are initiated prior to conditioning at
low temperature according to clause 5.2 .
6.3 Gripping and loading

The specimen shall be gripped to
approximately 25 mm from the ends. Care shall be
taken to ensure proper alignment of the specimen.
The specimen shall be loaded at a constant rate that

will cause failure in 3 to 5 min; (2,8 ± 0,5) kN/min
will be suitable for most thicknesses.
6.4 Crack length

The failing load, crack length at onset of fast
fracture and test temperature shall be recorded. The
crack length at onset of fast fracture may be
determined by closely following the progress of the
crack front during slow fracture and examination of
the fracture surface (Figure 3 refers).
The average crack length shall be recorded to the
nearest 0,2 mm. Figure 3 is a sketch of the cross
section of the specimen after failure taken at the
centreline of the hole.
7 Expression of results
7.1 Fracture toughness

Fracture toughness K shall be computed from the
equation:

6.1 The resistance to crack propagation (toughness)
of the material shall be determined as follows:
6.2 Initiation of cracks

Cracks shall be initiated on opposite sides of the
centrally located hole in the specimen so as to be
oriented in the width direction.

© BSI 01-2000

3


EN 2155-21:1989

7.2 Strain energy release rate

An alternative method of assessment is to use strain
¹W
energy release rate ¹ A computed from the
equation:

Dimensions in millimetres

where:
P = failure load in N
t = thickness of the specimen in mm
B = specimen width in mm
of elasticity in MPa, determined in
E = amodulus
tensile test under a stress of 10 MPa
; = 3,141
Z =

(see Table 1)

Y = ---XB
X = crack length at onset of fracture in mm
W = strain energy
A = fracture area

8 Test report

The test report shall include:

8.1 the fracture toughness expressed in MPa.mm1/2
at (23 ± 2) °C and at (– 18 ± 1) °C.
8.2 and/or the strain energy release rate expressed
in kJ/m2 at (23 ± 2) °C and at (– 18 ± 1) °C.

4

Figure 1 — Driving yoke and blade for
initiating cracks in toughness specimens

© BSI 01-2000


EN 2155-21:1989

Dimensions in millimetres

Figure 2 — Toughness specimen
D imensions in millimetres

Figure 3 — The fracture zones on a failed specimen

© BSI 01 - 2 000

5

EN 2155-21:1989

Table 1 — Values of Z
Example: When Y = X
---- = 0,146, Z = 0,0746
B
Y

0,070
0,080
0,090
0,100
0,110
0,120
0,130
0,140
0,150
0,160
0,170
0,180
0,190
0,200
0,210
0,220
0,230
0,240
0,250
0,260

0,270
0,280
0,290
0,300
0,310
0,320
0,330
0,340
0,350
0,360
0,370
0,380
0,390

6

O

0,0352
0,0403
0,0454
0,0505
0,0557
0,0609
0,0661
0,0714
0,0768
0,0822
0,0876
0,0931

0,0987
0,1044
0,1101
0,1159
0,1219
0,1279
0,1340
0,1402
0,1466
0,1531
0,1597
0,1665
0,1735
0,1807
0,1880
0,1955
0,2033
0,2113
0,2196
0,2281
0,2370

1

0,0357
0,0408
0,0459
0,0510
0,0562
0,0614

0,0667
0,0720
0,0773
0,0827
0,0882
0,0937
0,0993
0,1049
0,1107
0,1165
0,1225
0,1285
0,1346
0,1409
0,1472
0,1538
0,1604
0,1672
0,1742
0,1814
0,1887
0,1963
0,2041
0,2121
0,2204
0,2290
0,2379

2

0,0362
0,0413
0,0464
0,0515
0,0567
0,0619
0,0672
0,0725
0,0778
0,0833
0,0887
0,0942
0,0998
0,1055
0,1113
0,1171
0,1231
0,1291
0,1352
0,1415
0,1479
0,1544
0,1611
0,1679
0,1749
0,1821
0,1895
0,1971
0,2049
0,2129

0,2213
0,2299
0,2388

3

0,0367
0,0418
0,0469
0,0521
0,0572
0,0625
0,0677
0,0730
0,0784
0,0838
0,0893
0,0948
0,1004
0,1061
0,1119
0,1177
0,1237
0,1297
0,1359
0,1421
0,1485
0,1551
0,1617
0,1686

0,1756
0,1828
0,1902
0,1979
0,2057
0,2138
0,2221
0,2307
0,2397

4

0,0372
0,0423
0,0474
0,0526
0,0578
0,0630
0,0683
0,0736
0,0789
0,0843
0,0898
0,0953
0,1010
0,1067
0,1124
0,1183
0,1243
0,1303

0,1365
0,1428
0,1492
0,1557
0,1623
0,1693
0,1763
0,1836
0,1910
0,1986
0,2065
0,2146
0,2230
0,2316
0,2406

5

0,0377
0,0428
0,0479
0,0531
0,0583
0,0635
0,0688
0,0741
0,0795
0,0849
0,0904
0,0959

0,1015
0,1072
0,1130
0,1189
0,1249
0,1309
0,1371
0,1434
0,1498
0,1564
0,1630
0,1700
0,1771
0,1843
0,1917
0,1994
0,2073
0,2154
0,2238
0,2325
0,2415

6

0,0382
0,0433
0,0485
0,0536
0,0588
0,0640

0,0693
0,0746
0,0800
0,0854
0,0909
0,0965
0,1021
0,1078
0,1136
0,1195
0,1255
0,1315
0,1377
0,1440
0,1505
0,1571
0,1637
0,1707
0,1778
0,1850
0,1925
0,2002
0,2081
0,2162
0,2247
0,2334
0,2424

7

0,0387
0,0438
0,0490
0,0541
0,0593
0,0646
0,0698
0,0752
0,0805
0,0860
0,0915
0,0970
0,1027
0,1084
0,1142
0,1201
0,1261
0,1321
0,1384
0,1447
0,1511
0,1577
0,1644
0,1714
0,1785
0,1858
0,1933
0,2010
0,2089
0,2171

0,2255
0,2343
0,2433

8

0,0392
0,0443
0,0495
0,0546
0,0598
0,0651
0,0704
0,0757
0,0811
0,0865
0,0920
0,0976
0,1032
0,1090
0,1148
0,1207
0,1267
0,1328
0,1390
0,1453
0,1518
0,1584
0,1651
0,1721

0,1792
0,1865
0,1940
0,2017
0,2097
0,2179
0,2264
0,2352
0,2443

9

0,0398
0,0449
0,0500
0,0552
0,0604
0,0656
0,0709
0,0762
0,0816
0,0871
0,0926
0,0982
0,1038
0,1095
0,1154
0,1213
0,1273
0,1334

0,1396
0,1460
0,1524
0,1594
0,1658
0,1728
0,1799
0,1873
0,1948
0,2025
0,2105
0,2187
0,2273
0,2361
0,2452

© BSI 01-2000


BS EN 2155-21:1989

National appendix A

The United Kingdom participation in the preparation of this European Standard was entrusted by the
Aerospace Standards Policy Committee (ACE/-) to Technical Committee ACE/62 upon which the following
bodies were represented:
British Plastics Federation
Ministry of Defence
Society of British Aerospace Companies Limited

© BSI 01-2000


BS EN
2155-21:1989

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