1、ST5-AECMA PREN 2155-20-ENGL 2000 In12311 00LdLL hTL m Edition approved for publication 2000-10-31 - AECMA STANDARD NORME AECMA AECMA NORM Comments should be sent within six months aier the date of publication lo Guiledelle 94 C7 Chairman AECMA Mr Wright 8-1200 BRUXELLES prEN 21 55-20 Editlon P 1 Oct
2、ober 2000 PUBLISHED BY THE EUROPEAN ASSOCIATION OF AEROSPACE INDUSTRIES (AECMA) Gulledelle 94 - 8-1200 BRUXELLES - Tel. (+32) 2 75 81 1 O - Fax. (+32) 2 775 81 11 ICs: Descriptors: ENGLISH VERSION Aerospace series Test methods for transparent materials for aircraft glazing Part 20: Determination of
3、retention of strength after crazing for as-cast acrylics Srie arospatiale Luft- und Raumfahrt Mthodes dessais pour matriaux transparents pour vitrages aronautiques Pattie 20: Dtermination de la rsistance rsiduelle des acryliques couls aprs fendillement Prfverfahren fr transparente Werkstoffe zur Ver
4、glasung von Luftfahrzeugen Teil 20: Bestimmung der bleibenden Festigkelt von Acrylglasern nach Spannungsriblldung This “Aerospace Series” Prestandard has been drawn up under the responsibility of AECMA (The European Association of Aerospace Industries). It is published on green paper for the needs o
5、f AECMA- Members. It has been technically approved by the experts of the concerned Technical Committee following comment 6y the Member countries. Subsequent to the publication of this frestandard, the technical content shall not be changed to an extent that interchangeability is affected, physicaliy
6、 or functionally, wifhout re-identification of the standard. After examination and signature of the AECMA Standard Checking Centre (NPS) and formai agreement of the Official Services of the Member countries it will be submitfed as a draff European Standard to CEN (European Committee for Standardizat
7、ion) for formal vote. Nota - Extra copies can be supplied by B.N.A.E. - Technopolis 54 - 199, rua Jean-Jacques Rousseau - 92138 ICSY-LES-MOULINEAUX CEDEX STD-AECMA PREN 2155-20-ENGL 2000 m 10123LL OOLBBb7 538 m Page 2 prEN 21 55-20: 2000 Contents Definition 3 Test specimens . 3 Apparatus and materia
8、ls . 4 STD-AECMA PREN 2L55-20-ENGL 2000 = LOL23LL OLBBbB q74 I Page 3 prEN 2155-20: 2000 1 Scope This standard specifies the method to determine the retention of strength ater crazing of as-cast acrylics for aerospace applications. 2 Definit ion For the purpose of this standard the following definit
9、ion applies: Retention of strength after crazing is the capability of as-cast acrylic to maintain a specified strength over a period of 24 h at (35 f 3) OC in spite of possible inception of crazing at the commencement of this period. Acetone is applied under controlled conditions to induce crazing,
10、and the specimen is loaded to develop an outer fibre stress (o) of 10,4 MPa. 3 Apparatus and materials - Fixture to enable the specimens to be firmly clamped between rigid supports at one end and to be loaded by the application of weights suspended from the other end of the specimen (see figure 2).
11、- Acetone of an analytical reagent standard. - Vernier callipers capable of measuring to an accuracy of 0,Ol mm. - An air oven capable of maintaining a temperature of (155 f 2) OC. - A conditioning cabinet capable of maintaining a temperature of (35 f 3) OC and RH of (50 f 5)%. - A desiccator contai
12、ning silica gel. 4 Test specimens The specimen shall consist of a strip of the material of dimensions given in figure 1, cut from sheet of nominal thickness 6,O mm. Thicker material shall be machined on one face to 6,O mm and this shall be face i3 (see figure 2). (For sheet thinner than 6,O mm, the
13、original thickness shall be used.) The edges of the strip shall have a polished finish and be free from chipping and a hole shall be drilled, as shown in figure 1 to facilitate loading. The protective film shall be removed and the specimen washed in clean water, which may contain approximately 1 YO
14、detergent, at (30 - 40) OC. 5 Procedure 5.1 Removal of residual stresses 5.1.1 The specimens shall be freely suspended in an air circulating oven and maintained at a temperature of (155 $: 2) OC for a period of 30 min and then annealed in an air circulating oven in accordance with the manufacturers
15、instructions. 5.1.2 0,02 mm at the fulcrum. After annealing, the width and thickness of the specimens shall be measured to an accuracy of STDqAECMA PREN ZL55-20-ENGL 2000 LOLZ3LL OOLBBb7 300 = Page 4 prEN 21 55-20: 2000 5.2 Tests 5.2.1 and a relative humidity of (50 k 5) % for a period of 24 h (mini
16、mum) to 96 h (maximum). The specimens and equipment shall be conditioned before the test at a temperature of (35 f 3) OC 5.2.2 Immediately after conditioning, the test specimen shall be rigidly clamped in a support and loaded with a weight suspended from the hole, in accordance with figure 2. The ap
17、plied load shall be calculated by the following formula: o Wh2 Load (N) = - 6L where: a = stress of outer fibres in MPa W = width of specimen at fulcrum in mm h = thickness of specimen at fulcrum in mm L = distance from fulcrum to loading point, measured to an accuracy of k Oll mm. 5.2.3 Acetone at
18、(35 f 3) “C shall be liberally applied to face A (see figure 2) continuously for 5 min with a soft brush, care being taken to ensure that the acetone wetted area extends to the face of the support, above the fulcrum. 5.2.4 The specimen shall then be left in the above conditions for 24 h. 5.2.5 Ten s
19、pecimens shall be tested. 6 Test report The test report shall include: - reference to this standard; - material type; - tested thickness and, if different, original thickness of the sheet; - numbers of batch and sheet from which the specimens have been taken; - the number of specimens fractured duri
20、ng the test; - decision to accept or reject, taken in accordance with the material standard. Page 5 prEN 21 55-20: 2000 175 06 _- - 35 -. L =125 - 15 Dimensions in millimetres (Nominal unless staded) I II 2 +i Il q - t L =125*i - r“ Face B Figure 1 - lest specimen C! t t II .E Dimensions in millimetres Figure 2 - Loading geometry
