1、 STD-AECMA PREN 2850-ENGL 1777 LOL23LL OOLLiO84 7T0 = Edition approved for publication 1997-1 1-28 AECMA STANDARD NORME AECMA AECMA NORM C7 Chairman Comments should be sent within six months after the date of publication to Gulledelle 94 AECMA Mr Wright B-1200 BRUXELLES prEN 2850 Edition P 2 Novembe
2、r 1997 PUBLISHED BY THE EUROPEAN ASSOCIATION OF AEROSPACE INDUSTRIES (AECMA) Gulledelle 94 - 8-1200 BRUXELLES - Tel. (+32i 2 775 81 10 - Fax. (+32) 2 775 81 11 ICs: ENGLISH VERSION Aerospace series Carbon fibre thermosetting resin unidirectional laminates Compression test parallel to fibre direction
3、 Supersedes issue P 1 November 1991 Srie arospatiale Stratifis unidirectionnels Fibres de carbone/rsine thermodurcissable Essai de compression paralllement au sens des fibres Luft- und Raumfahrt Unidirektionale Kohlenstoffaser- Duroplast Verbundwerkstoffe Druckversuch parallel zur Faserrichtung This
4、 “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 concerned Technical Committee folio wing comme
5、nt 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 examination and signature of the AECMA Standard Che
6、cking 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. COPYRIGHT Association Europeene Des Constructeurs de Materiel AerospaceLicensed by Information H
7、andling ServicesSTD-AECMA PREN 285U-ENGL 1777 10123LL 0014085 b37 Page 3 prEN 2850: 1997 1 Scope This specification defines a method for the determination of stress at failure and Youngs modulus in compression of carbon thermosetting resin unidirectional laminates. The method only covers test pieces
8、 the axis of which is parallel to the fibre direction. This method covers fibres (or fabrics) other than carbon, when the relevant technical specification explicitly mentions it. 2 Normative references This European Standard incorporates by dated or undated reference provisions from other publicatio
9、ns. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. Fo
10、r undated references the latest edition of the publication referred to applies. EN 2372 Aerospace series - Nuts, hexagon, thin steel, cadmium-plated - Classification 1100 MPa/235 OC EN 2489 Aerospace series - Fibre reinforced plastics - Determination of the action of liquid chemicals 2, EN 2565 Aero
11、space series - Preparation of carbon fibre reinforced resin panels for test purposes 2) EN 2743 Aerospace series - Reinforced plastics - Standard procedures for conditioning prior to testing 2) EN 2744 Aerospace series - Non-metallic materials preferred test temperatures EN 2823 Aerospace series - F
12、ibre reinforced plastics - Test method for the determination of the effect of exposure to humid atmospheres on physical and mechanical characteristics 2, EN 2859 Aerospace series - Bolts, hexagonal normal head, close tolerance shank, short thread in cadmium-plated steel - Classification 1 1 O0 MPa/2
13、35 OC 2, EN 3783 Aerospace series - Procedure of the normalisation of test results of fibre dominated composite mechanical properties 2, 3 Principle of the method The method consists in recording and measuring the longitudinal strain of the material as a function of the applied load during a compres
14、sion test carried out at a constant rate until failure. The load applied to the material may be introduced in two different ways : - either mainly in shear through co-cured or bonded tabs (Method A) ; - or exclusively in compression by direct end loading of the test piece (Method B). It is important
15、 to note that the test results obtained using different test pieces are not comparable. Published as AECMA Standard at the date of publication of this standard 2, Published as AECMA Prestandard at the date of publication of this standard Previous page is blank COPYRIGHT Association Europeene Des Con
16、structeurs de Materiel AerospaceLicensed by Information Handling ServicesSTD-AECMA PREN 2850-ENGL 1797 m LOL23LL OOL4OAb 573 m Page 4 prEN 2850: 1997 4 Definitions For the purposes of this standard, the following definitions apply. 4.1 Compression stress at any point in time during the test (ac) Com
17、pression load per initial unit cross-sectional area in the gauge length sustained by the test piece at any point in time during the test. 4.2 Compression stress at the moment of failure. It is calculated using the formula given in 10.1. Compression stress at failure (ocl 4.3 Strain (E 1) Change in t
18、he distance between reference points within the gauge length of the test piece produced by a compression load expressed in relation to the original distance between these points. E is the strain measured parallel to the fibre axis. 11 4.4 Secant compression modulus Two methods of calculation are pos
19、sible. The one based on strain shall be preferred. Otherwise, the one based on the forces shall be used. 4.4.1 Secant compression modulus (EC11 (a,) Slope of the straight line passing through the stress/longitudinal strain diagram at a point corresponding to a % strain with respect to the gauge leng
20、th of the test piece and a point corresponding to % strain on the same diagram. a and are defined in the material standard. In the absence of a material standard, a = 0,l % and = 0,5 % shall be chosen. It is calculated using the formula in 10.2.1. 4.4.2 Secant compression modulus (Ec1 (PR/lO, PR/) S
21、lope of the straight line passing through the stress/longitudinal strain diagram at a point corresponding to a stress calculated from PRAO, and a point corresponding to a stress calculated from PR/2 , where PR is the load at failure of the test piece. It is calculated using the formula in 10.2.2. CO
22、PYRIGHT Association Europeene Des Constructeurs de Materiel AerospaceLicensed by Information Handling Services STD-AECMA PREN 28.50-ENGL 1777 M 1OL2311 0014087 40T Page 5 prEN 2850: 1997 5 Designation Designation of the method shall be in accordance with the following example : Number of this standa
23、rd Type of test piece (see 6.2) 6 Test pieces 6.1 Preparation of test panels Test panels shall be prepared according to EN 2565. Manufacturing parameters, such as environmental products, curing cycle, etc. shall comply with the applicable technical specification. 6.2 Shape and dimension Two types of
24、 test pieces are given : - Type A (see example in annex A) ; - Type B (see example in annex B). Alternatives to type A are possible if they atisfy he f - Gauge length g = 10 k 0,25 mm - Thickness h = (2 i 0,2) mm - Total thickness H = (4,5 k 0,5)mm - Width b = (10 * O, 2)mm - Tab length t =250 mm -
25、Distance between grips K = 13 i Oll mm Ilowing requiremen s: Detail of the encircled area 4-b Figure 1 Angle of misalignment of the fibres with respect to the compression loading axis shall be less than f 0,5O. COPYRIGHT Association Europeene Des Constructeurs de Materiel AerospaceLicensed by Inform
26、ation Handling Services6.3 Tabs 6.3.1 Bonded tabs In the case of bonded tabs, a check shall be made that the temperature of the bonding cycle does not induce any undesirable post-curing effect in the laminate. The material forming the tabs shall preferably be the same as that of the test pieces. It
27、is preferable to form the tabs in a co-curing operation when testing at high temperature and/or after humidity ageing. 6.3.2 Integral tabs The test piece is made up of n plies at Oo at its center and of m plies at f 45O each side of the plies at OO. n is such that n plies are 2,25 mm to 2,5 mm thick
28、. m is such that (n + 2 m) plies are 4 mm to 5 mm thick. The integral tabs are machined to provide the gauge length of the test piece (see annex A - Test pieces A21A4). NOTE : Where the grips slip, a ply of dry glass may be added to the surface of the tabs, prior to the curing of the panel. 6.4 Numb
29、er The number of test pieces to be used is defined in the technical specification. If it is not the case, 5 test pieces shall be used. 7 Apparatus 7.1 Micrometer with flat faces 6 mm in diameter ; accurate to within 0,Ol mm 1. 7.2 Test machine accurate to within 1 % in the load range used. 7.3 .ensu
30、red in a suitable way. In order to avoid any buckling, which would affect the test, an accurate alignment shall be An example of grip alignment guidance is given in annex A or B and C. 7.4 Device for recording strain as a function of load accurate to within 1 % in the strain range used. This equipme
31、nt shall not produce marks on the test piece likely to cause premature failures. The chosen device shall allow any possible buckling during the test to be detected by the separate recording of the strain on each face of the test piece (eg. strain gauges). 7.5 tests at temperatures (in accordance wit
32、h EN 2744) other than ambient. If required, a controlled temperature cabinet and recording thermocouple may be used for Note 1 : For method B, a micrometer with flat faces 2 mm in diameter is allowed. COPYRIGHT Association Europeene Des Constructeurs de Materiel AerospaceLicensed by Information Hand
33、ling ServicesSTD-AECMA PREN 2850-ENGL 1777 = 1012311 001q089 282 Page 7 prEN 2850: 1997 8 Conditioning Where testing is carried out in the initial state, conditioning shall be in accordance with EN 2743. Where testing is carried out after immersion, conditioning shall be in accordance with EN 2489.
34、Where testing is carried out after exposure to humid heat, conditioning shall be in accordance with EN 2823. 9 Procedure 9.1 Measure the thickness twice to the nearest 0,Ol mm and the width to the nearest 0,Ol rnm in the gauge length of the test piece. 9.2 Position the strain measuring device (see 7
35、.4) on the test piece. 9.3 of the test shall meet the following requirements : For tests at a temperature other than ambient, the time between conditioning and the start 9.3.1 For test pieces that have neither been subjected to ageing nor immersion, the period during which they are maintained at the
36、 test temperature shall be determined by preliminary tests and be noted in the report. 9.3.2 For test pieces that have undergone immersion, follow the procedure described in EN 2489. 9.3.3 described in EN 2823. For test pieces that have undergone ageing in a humid environment, follow the procedure 9
37、.4 The grips (if part of the jig) shall cover the tabs in accordance with Figure 1. In the case of type 6, apply a gripping load of 0,5 mN, using standard fasteners, according to EN 2859-050 and EN 2372, for example. 9.5 Apply load at a constant speed .e. a closing speed of the grips of 1 mm/min. 9.
38、6 Recording of strain 9.6.1 Type A test piece Record throughout the test the strains E“, = strain parallel to axis of the test piece (other face). COPYRIGHT Association Europeene Des Constructeurs de Materiel AerospaceLicensed by Information Handling ServicesSTD-AECMA PREN 2850-ENGL 1777 1012111 OOL
39、i070 TTV W Page 8 prEN 2850: 1997 9.6.2 Specimen type B On the modulus test piece, only 9.7 needs to be recorded. Note the load at failure PR 10 Calculation of results 10.1 Stress at failure (ocl,) - PR OcIl - - bh Where : PR = load at failure, in newtons ; b = width, in millimetres ; h = thickness,
40、 in millimetres. NOTE : According to the type of test piece, oCl1 may be calculated as a function of the measured thickness, and/or the theoretical thickness, and/or nominal thickness in accordance with EN 3783. 10.2 Secant modulus (E Measured from the loadhtrain recording, the secant compression mo
41、dulus is given by the formulae : 10.2.1 Figure 2 Where : a = = Pa = load corresponding to a, in newtons ; P = load corresponding to , in newtons ; b = width, in millimetres ; h = thickness, in millimetres. strain parallel to the axis of the test piece (lower limit) ; strain parallel to the axis of t
42、he test piece (upper limit) ; COPYRIGHT Association Europeene Des Constructeurs de Materiel AerospaceLicensed by Information Handling ServicesPage 9 prEN 2850: 1997 10.2.2 Figure 3 Where : PR = load at failure, in newtons ; )B = )A = strain parallel to the test piece axis corresponding to PR/2 ; str
43、ain parallel to the test piece axis corresponding to P/10 ; b = width, in millimetres ; h = thickness, in millimetres. NOTE : According to the type of test piece, (Ec,) may be calculated as a function of the measured thickness, and/or theoretical thickness and/or nominal thickness in accordance with
44、 EN 3783. 11 Validity The test is only valid if failure occurs in the free length of the test piece. There shall be no bushing of the ends. For type A test pieces, buckling is acceptable if the difference between strains measured on each face of the test piece in the load range 0,1 PR - 0,9 PR remai
45、ns such that : 200 n E.10-6 - 0.1 PR - 200 - 400 - 600 - 800 - 1000 - 0.9 PR - no0 - 1400 -16000 -14000 -I2000 -10000 -8000 -6W -4000 -2000 O Figure 4 COPYRIGHT Association Europeene Des Constructeurs de Materiel AerospaceLicensed by Information Handling Services STD-AECMA PREN 2850-ENGL 1997 101231
46、1 0014092 877 I Page 10 prEN 2850: 1997 12 Test report The test report shall give the following information : 12.1 and other details concerning the tested material. Reference to this standard, the trade mark, identification marking, origin, date of receipt 12.2 All information regarding the preparat
47、ion of the test pieces, the tabs and their bonding. 12.3 Measured dimensions of the test pieces and the type of test pieces chosen. 12.4 specification. The test conditions, for example temperature, relative humidity if they deviate from the 12.5 when testing after immersion (see EN 2489) or exposure
48、 to humid heat (see EN 2823). The period of time during which the test pieces were maintained at the test temperature 12.6 strain. Present a diagram giving the recorded load as a function of time or displacement, or the 12.7 The stress at failure (ac, 1 and the mode of failure. 12.8 The secant modul
49、us Ec,l) and the mode of calculation. 12.9 The individual values, the arithmetic mean and the standard deviation shall be quoted. Indicate whether the individual values are calculated with the measured thickness or the theoretical thickness according to EN 3783. 12.10 Comments on all circumstances that might have influenced the results. COPYRIGHT Association Europeene Des Constructeurs de Materiel AerospaceLicensed by Information Handling ServicesPage 11 prEN 2850: 1997 STDmAECMA PREN 2850-ENGL A777 m LOL23LL OOLLiO73 703 m Tab type h H b r Notes Nor
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