BRITISH STANDARD AEROSPACE SERIES BS EN 2155 21 1989 Test methods for transparent materials for aircraft glazing — Part 21 Determination of resistance to crack propagation (K factor) This European Sta[.]
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 580 17926 Oesterreichisches Normungsinstitut Institut belge de normalisation Dansk Standardiseringsraad Suomen Standardisoimisliito, r.y Association franỗaise de normalisation Deutsches Institut fỹr 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 Espol 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 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 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 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 Contents Brief history Scope and field of application Definitions Apparatus Specimens Conditioning Procedure Expression of results Test report Figure — Driving yoke and blade for initiating cracks in toughness specimens Figure — Toughness specimen Figure — The fracture zones on a failed specimen Table — Values of Z Page 3 3 3 4 5 © BSI 01-2000 EN 2155-21:1989 Scope and field of application This standard specifies how the resistance to crack propagation of rigid transparent sheet is to be determined 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 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 to 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 Specimens Test specimens shall conform to Figure 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 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 prior to testing 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 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 to 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 refers) The average crack length shall be recorded to the nearest 0,2 mm Figure is a sketch of the cross section of the specimen after failure taken at the centreline of the hole 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 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 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 Figure — Driving yoke and blade for initiating cracks in toughness specimens © BSI 01-2000 EN 2155-21:1989 Dimensions in millimetres Figure — Toughness specimen D imensions in millimetres Figure — The fracture zones on a failed specimen © BSI 01 - 000 EN 2155-21:1989 Table — 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 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 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 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 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 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 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 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 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 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 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 BSI — British Standards Institution BSI is the independent national body responsible for preparing British Standards It presents the UK view on standards in Europe and at the international level It is incorporated by Royal Charter Revisions British Standards are updated by amendment or revision Users of British Standards should make sure that they possess the latest amendments or editions It is the constant aim of BSI to improve the quality of our products and services We would be 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