1、AECMA STANDARD NORME AECMA AECMA NORM Edition approved for publication Comments should be sent within six months after the date of publication to 2000-1 0-31 AECMA Mr Wright Gulledelle 94 C7 Chairman 8-1200 BRUXELLES 0 aecrna 20( prEN 2155-22 Edition P 1 October 2M10 PUBLISHED BY THE EUROPEAN ASSOCI
2、ATION OF AEROSPACE INDUSTRIES (AECMA) Gulledelle 94 - 8-1200 BRUXELLES - Tel. (+32) 2 775 8110 - Fax. (+32) 2 775 811 1 ICs: Descriptors: ENGLISH VERSION Aerospace series Test methods for transparent materials for aircraft glazing Part 22: Determination of thermal relaxation of stretched acrylic she
3、et Srie arospatiale Luft- und Raumfahrt Mthodes dessais pour matriaux transparents pour vitrages aronautiques Partie 22: Dtermination de la relaxation thermique des feuilles tires en acrylique Prfverfahren fr transparente Werkstoffe zur Verglasung von Luftfahrzeugen Teil 22: Bestimmung der thermisch
4、en Relaxation von gerecktem Acrylglas 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 of AECMA- Members. It has been technically approved by the experts of the con
5、cerned Technical Committee following comment by the Member countries. Subsequent to the publication of this Prestandard, the technical content shall not be changed to an extent that interchangeability is affected, physically or functionally, without re-identification of the standard. After examinati
6、on and signature of the AECMA Standard Checking Centre (NPS) and formal agreement of the Official Services of the Member countries it will be submitted as a draft European Standard to CEN (European Committee for Standardization) for formal vote. Nota - Exira copies can be Supplied by B.N.A.E. - Tech
7、nopolis 54 - 199, nie Jean-Jacques Rousseau - 92138 ISSY-LES-MOULINEAUX CEDEX STD-AECMA PREN 2155-22-ENGL 2000 9 10323L3 0038872 T5 M Page 2 prEN 21 55-22: 2000 Contents Scope . 3 Definition . 3 . 3 Test specimens . 3 Test report . 4 . 3 SD-AECMA PREN 2155-22-ENGL 2000 D 1012311 0038873 831 D Page 3
8、 prEN 21 55-22: 2000 1 Scope This standard specifies the method to determine the thermal relaxation of stretched acrylic sheet for aerospace applications by an isothermal method, which measures surface shrinkback at 110 OC and 145 “C. 2 Def i n it ion For the purpose of this standard the following d
9、efinition applies: Thermal relaxation of stretched acrylic sheet is the dimensional change of the specimen caused by its reversion on being heated to a specified temperature. The thermal relaxation is determined as the percentage shrinkback of lengths marked on the specimens, compared to their origi
10、nal length. 3 Apparatus - Dividers - Vernier callipers or travelling microscope capable of measuring to an accuracy of i 0,Ol mm. - An air circulating oven capable of maintaining the temperature at (1 10 i 1) OC and (145 f 2) OC. - A sheet of de-volatilised felt for supporting the specimens in the o
11、ven. - A temperature measuring device for monitoring the temperature in the oven, capable of reading to an accuracy of f 0,5 OC. - A desiccator containing silica gel. 4 Test specimens Two specimens, (75 f 1) mm x (75 f 1) mm, shall be cut from the material under test. If the thickness of the materia
12、l is 3 mm or less, the specimen thickness (h) shall be that of the material. If thicker material is to be used, the thickness may be reduced to (3 f Oll) mm by machining one face only. A circle of diameter (50 I 1) mm shall be scribed with dividers on each test specimen, in accordance with figure 1.
13、 The scribed line shall not exceed 0,l mm in width. For machined specimens, the circle shall be scribed on the unmachined face. 5 Procedure 5.1 Conditioning of test specimens Thermal relaxation depends on the moisture content and on the thickness of the material, therefore a standard thickness and c
14、onditioning treatment of the specimens are required. Prior to testing, the specimens shall be dried for (96 ? 1) h at (80 f 2) OC in an air circulating oven, then cooled to room temperature in a desiccator over silica gel. If an immediate test is not possible after cooling the specimens, they shall
15、be stored in a desiccator over silica gel until testing can be done. Page 4 prEN 21 55-22: 2000 5.2 Method Prior to test, the circle diameters, marked A and 6 in figure 1, shall be measured to an accuracy of 0,l mm and designated A and B. The test specimens, conditioned in accordance with 5.1, shall
16、 be wrapped in a sheet of devolatilised felt and placed in an oven at 110 OC for (24 f 1) h. They shall then be cooled to room temperature and stored for 3 h at room temperature. The circle diameters, A and BI, shall be re-measured to an accuracy of 0,1 mm and designated Allo and Bllo. The same spec
17、imens shall then be placed in an oven at 145 OC for (24 f 1) h, thereafter be cooled to and stored for 3 h at room temperature, and then re-measured. The diameters now measured, shall be designated and 8145. 5.3 Calculation The thermal relaxation, Rt, of each specimen at each temperature, t, shall b
18、e calculated as follows: B Rt = - 2 where: Rt is the thermal relaxation at temperature t in %, A is original diameter in mm, At is diameter A at temperature t in rnm, B is original diameter in mm, - material type and thickness; - numbers of batch and sheet from which the specimens have been taken; -
19、 thermal relaxation, for each being reported; - a record of any distortion of the specimens, whether caused by dishing or uneven retraction; - compliance with or failure to meet the requirements of the material standard. and R145, expressed as percentage, the average value and individual values STD*AECMA PREN 2155-22-ENGL 2000 m LU1231l 0018875 bOq m Page 5 prEN 21 55-22: 2000 Dimensions in millimetres Figure 1 -Test speciment for the determination of thermal relaxation
