EN 2746-1998 en Aerospace Series - Glass Fibre Reinforced Plastics - Flexural Test - Three Point Bend Method《航空航天系列 玻璃纤维增强塑料 弯曲试验 三点弯曲法》.pdf

1、BRITISH STANDARD AEROSPACE SERIES Glass fibre reinforced plastics - Flexural test - Three point bend method The European Standard EN 27461998 has the status of a British Standard ICs 49.025.40 BS EN 2 746: 1998 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS EN 27461998 dir

2、ection of the Engineering Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15 November 1998 Amd. No. National foreword Date Text affected This British Standard is the English language version of EN 27461998. The UK participation in its preparati

3、on was entrusted to Technical Committee ACW64, Aerospace structural reinforced plastics, which has the responsibility to: - aid enquirers to understand the text; - present to the responsible intedonaUEuropean committee any enquhies on the interpretation, or proposals for change, and keep the UK inte

4、rests informed; - monitor related international and European developments and promulgate them in the UK A iist of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications ref

5、erred to in this document may be found in the BSI Standards Catalogue under the section entitled “Intedonal Standards Correspondence Index“, or by using the “Find“ facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include al the necessary provisions of a cont

6、ract. 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 fiont cover, an inside hnt cover, the EN title page, pages 2 to 8, an inside back c

7、over and a back cover. O BSI 1998 ISBN O 580 30716 8 I I EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 2746 August 1998 ICs 49.025.40 Descriptors: Aircraft industry, reinforced plastics, glass reinforced plastics, tests, bend tests English version Aerospace series - Glass fibre reinforced pla

8、stics - Flexural test - Three point bend method Srie arospatiale - Plastiques renforcs au verre textile - Essai de flexion - Mthode des trois pannes Luft- und Raumfahrt - GlasfaserversrMe Kunststoffe - Begeversuch - Dreipunkwerfahren This European Standard was approved by CEN on 15 May 1998. CEN mem

9、bers are bound to comply with the CEWCENELEC Intemal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibiiographical references concerning such national standards may be obtained on applicatio

10、n to the 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 the Central Secretariat has the sa

11、me status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal. Spain, Sweden, SWeriand and Uniied Kingdom. EUROPEAN COMMiTEE FOR STAN

12、DARDIZAiON EUROPISCHES KOMITEE FOR NORMUNG COMITE EUROPEEN DE NORMALISATION Central Secretariat: rue de Stassart, 36 8-1050 Bruswls 0 1998 CEN All rights of exploitation in any form and by any means resewed worldwide for CEN national Members. Ref. No. EN 2746:1998 E STDDBSI BS EN 27Lib-ENGL Page 2 E

13、N 2746:1998 Foreword This European Standard has been prepared by the European Association of Aerospace Manufacturers (AECMA). After inquiries and votes carried out in accordance with the rules of this Association, this Standard has received the approval of the National Associations and the official

14、Sewices of the member countries of AECMA, prior to its presentation to CEN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by February 1999, and conflicting national standards shall be withdrawn at

15、the latest by February 1999. According to the CENICENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, itaiy, Luxembo

16、urg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. * * 02 Page 3 EN 2746:1998 1 scope This standard specifies the three point bend method for the determination of the flexural properties of glass fibre reinforced plastics for aerospace applications. 2 Normative re

17、ferences This European Standard incorporates by dated or undated reference provisions from other publications. 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 t

18、hese publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. EN 2374 Aerospace series - Glass fibre reinforced mouldings and sandwich composites - Production of test panels E

19、N 2489 Aerospace series - Fibre reinforced plastics - Determination of the action of liquid chemicals EN 2743 Aerospace series - Reinforced plastics - Standard procedures for conditioning prior to testing 1) EN 2823 Aerospace series - Fibre reinforced plastics - Test method for the determination of

20、the effect of exposure to humid atmosphere on physical and mechanical characteristics 1) 3 Definitions For the purpose of this standard the following definitions apply: 3.1 Deflection The distance travelled during the test by a point on the upper or lower face of the specimen at the centre of its sp

21、an measured from its initial position. 3.2 Conventional deflection Unless otherwise specified, a deflection equal to 1,5 times the specimen thickness. 3.3 Flexural stress The stress at the surface of the material in the middle of the span of the specimen between the supports at any time during the t

22、est. 3.4 Flexural strength Flexural stress at the moment when the applied force reaches the maximum value. 3.5 Flexural stress at failure Flexural stress at the moment of failure of the specimen. 3.6 Flexural modulus Slope of the tangent at the origin of the stresdstrain curve calculated from the fo

23、rce/deflection recording. 1) Published as AECMA Prestandard at the date of publication of the present standard. Page 4 EN 2746: 1998 4 Principle The method consists of the measurement of the deflection at the central loading nose as a function of the applied force during a flexural test carried out

24、at constant speed until failure occurs. The strain parallel to the specimen iengh is calculated as a function of the applied flexural stress. The following properties may be determined: - flexural stress and deflection at failure of specimens which break before or on reaching conventional deflection

25、; - flexural stress at conventional deflection of specimens which break beyond conventional deflection; - flexural strength of specimens which reach maximum laad before or at conventional deflection; - flxural strength or flexural stress at failure if this is required by the material standard; - fle

26、xural modulus. NOTE: The flexural modulus is only an approximate value of YOUNGS modulus of elasticity. 5 Apparatus A test machine, allowing relative displacement of the loading nose with respect to the supports at a constant speed, and indicating forces to i 1 % and deflections to f 2 %. The suppor

27、ts and the loading nose shall be at least as wide as the specimen and shall be parallel to one another. The radius, 4, of the loading nose and the radius, 4, of the supports shall be as follows: 4 = (5 f 0,l) mm; is the thickness of the specimen, in millimetres. Measure the span to I 0,5 %. Page 6 E

28、N 2746:1998 7.4 Test speed - visspecified; - the rate of strain is specified; - calculate it Set the test machine to the speed V; according to one of the following: where: V st. i h is the test speed, in millimetres per minute; is the rate of strain, in units per minute; is the span, in millimetres;

29、 is the thickness of the specimen, in millimetres. If there is no requirement, calculate K where: V h K = 0,5 min-. V= K. h is the test speed, in millimetres per minute; is the thickness of the specimen, in millimetres; 7.5 Test atmosphere Carry out the tests at (23 f 2) OC and (50 f 5) % relative h

30、umidity. 7.6 Tests Position the specimen symmetrically with respect to the supports, ensuring that its length is perpendicular to these supports. Ensure that the loading nose is placed exactly in the middle of the span and apply force at a constant speed, avoiding shock loading. The force and deflec

31、tion shall be simultaneously recorded. Note the values of the required characteristics: - at conventional deflection; - at maximum force; - at failure. 0 Expression of results 8.1 flexural stress 3 FL Uf = - 2bh2 where: of F L b h is the flexural stress, in megapascals; is the force applied, in newt

32、ons; is the span, in millimetres; is the width of the specimen, in millimetres; is the thickness of the specimen, in millimetres. * * m STDmBSI BS EN 274b-ENGL 1998 Lb2qbbS 0732b43 734 Page 7 EN 2746:1998 NOTE: A more precise calculation of the flexural stress takes into account the horizontal compo

33、nent of the flexural moment: 3 FL 4d2 26H at where: d is the deflection, in millimetres. 8.2 Flexural modulus Examine the force/deflection curve and determine the modulus from the initial rectilinear part, using at least five points. If the initial part of the curve is not linear, then a straight li

34、ne shall be drawn between 10 % and 25 % of the maximum force, see figure 2. Figure 2: Forcddeflection curve 13 AF - 4bN Ad where: 6 i b b AF Ad is the modulus, in megapascals; is the span, in millimetres; is the width of the specimen, in millimetres; is the thickness of the specimen, in millimetres;

35、 is a chosen difference in force, in newtons; is the difference in deflection corresponding to the difference in force AF; in millimetres. Page 8 EN 2746:1998 0.3 Modes of failure During the fiexural test, three different modes of failure may occur: - failure initiated at the surface by the tensile

36、stresses; - failure initiated at the surface by the compression stresses; - internal failure due to the shear stresses. For each specimen, indicate the mode(s) of failure. If the modes of failure of specimens of the same set are different, the calculated values of the flexural stress are no longer s

37、tatistically homogeneous and great care is needed in the evaluation of the results. If specimens fail in an area other than the area of the loading nose, the results shall not be taken into consideration. Carry out a set of retests Ni this case. 9 Test report It shall include the following: - number

38、 of this standard; - all data ensuring the traceability of the material (trade mark, identification marking, date of receipt, batch number, etc.); - all infomation regarding specimen preparation; - specimen dimensions; - span; - radius of supports if it differs from 2 mm; - test conditions; - exposu

39、re time at the test temperature; - specimen face in contact with the loading nose; - test speed; - forcddeflection curve; - flexural stress at conventional deflection; - flexural strength; - flexural stress at failure and mode of failure; - flexural modulus: - individual values, arithmetic mean and

40、standard deviation of results of tests or retests (if applicable): - any incident which may have affected the results. STD BS EN 2746:1998 BSI 389 Chiswick High Road London w4 4AL BSI BS EN 274b-ENGL 1778 Lb24bbS 0732b45 507 BSI - British Standards Institution BSI is the independent national body re

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