1、BRITISH STANDARD AEROSPACE SERIES BS EN 2746:1998 Glass fibre reinforced plastics Flexural test Three point bend method The European Standard EN2746:1998 has the status of a British Standard ICS 49.025.40BSEN 2746:1998 This British Standard, having been prepared under the directionof the Engineering
2、 SectorCommittee, was publishedunder the authority ofthe Standards Committee andcomes into effect on 15November1998 BSI 05-1999 ISBN 0 580 30715 8 National foreword This British Standard is the English language version of EN2746:1998. The UK participation in its preparation was entrusted to Technica
3、l Committee ACE/64, Aerospace structural reinforced plastics, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor r
4、elated international and European developments and promulgate them in the UK. A list 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 referred to in this document
5、may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of Britis
6、h 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, pages2 to 6 and a back cover. Thi
7、s 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. Amendments issued since publication Amd. No. Date CommentsBSEN2746:1998 BSI 05-1999 i Contents Page National foreword Inside front cover
8、 Foreword 2 Text of EN2746 3ii blankEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN2746 August1998 ICS 49.025.40 Descriptors: Aircraft industry, reinforced plastics, glass reinforced plastics, tests, bend tests English version Aerospace series Glass fibre reinforced plastics Flexural test Three
9、 point bend method Srie arospatiale Plastiques renforcs au verre textile Essai de flexion Mthode des trois pannes Luft- und Raumfahrt Glasfaserverstrkte Kunststoffe Biegeversuch Dreipunktverfahren This European Standard was approved by CEN on15 May1998. CEN members are bound to comply with the CEN/C
10、ENELEC 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 Central Secretariat or to an
11、y 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 same status as the official versions. C
12、EN members are the national standards bodies of Austria, Belgium, CzechRepublic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de N
13、ormalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1998 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 2746:1998 EEN 2746:1998 BSI 05-1999 2 Foreword This European Standard has bee
14、n 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 Services of the member countries of AECMA, prior to
15、 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 February1999, and conflicting national standards shall be withdrawn at the latest by February1999. According to the CEN/CE
16、NELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, CzechRepublic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Sw
17、itzerland and the United Kingdom. Contents Page Foreword 2 1 Scope 3 2 Normative references 3 3 Definitions 3 4 Principle 3 5 Apparatus 3 6 Specimens 4 7 Procedure 4 8 Expression of results 5 9 Test report 6 Figure 1 Detail of test apparatus 4 Figure 2 Force/deflection curve 5EN 2746:1998 BSI 05-199
18、9 3 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 references This European Standard incorporates by dated or undated reference provisions from other publications.
19、 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. For u
20、ndated references the latest edition of the publication referred to applies. EN2374, Aerospace series Glass fibre reinforced mouldings and sandwich composites Production of test panels. EN2489, Aerospace series Fibre reinforced plastics Determination of the action of liquid chemicals. EN2743, Aerosp
21、ace series Reinforced plastics Standard procedures for conditioning prior to testing 1) . EN2823, Aerospace series Fibre reinforced plastics Test method for the determination of the effect of exposure to humid atmosphere on physical and mechanical characteristics 1) . 3 Definitions For the purpose o
22、f 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 span measured from its initial position 3.2 conventional deflection unless otherwise specified, a deflection equal to1,5 t
23、imes 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 test 3.4 flexural strength flexural stress at the moment when the applied force reaches the maximum value 3.5 flexural stres
24、s 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 stress/strain curve calculated from the force/deflection recording 4 Principle The method consists of the measurement of the deflection at the central loading nose as
25、a function of the applied force during a flexural test carried out at constant speed until failure occurs. The strain parallel to the specimen length is calculated as a function of the applied flexural stress. The following properties may be determined: flexural stress and deflection at failure of s
26、pecimens which break before or on reaching conventional deflection; flexural stress at conventional deflection of specimens which break beyond conventional deflection; flexural strength of specimens which reach maximum load before or at conventional deflection; flexural strength or flexural stress a
27、t failure if this is required by the material standard; flexural modulus. NOTEThe 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 indica
28、ting forces to 1% and deflections to2%. The supports and the loading nose shall be at least as wide as the specimen and shall be parallel to one another. The radius, r 1 , of the loading nose and the radius, r 2 , of the supports shall be as follows: r 1 =(5 0,1)mm; r 2 =(2 0,2)mm. It shall be possi
29、ble to adjust the span (see Figure 1). 1) Published as AECMA Prestandard at the date of publication of the present standard.EN 2746:1998 4 BSI 05-1999 6 Specimens 6.1 Dimensions NOTEIf it is impossible to obtain specimens from the finished component, prepare test panels according to EN2374 or to a s
30、uitable method by agreement between the parties concerned. If it is necessary to use a thickness of specimen greater than3mm or if a failure in compression is expected, the radius of the supports may be increased on condition that: r 2 # 1,5h 6.2 Number Minimum of five. 7 Procedure 7.1 Conditioning
31、EN2743 for tests in the initial state. EN2489 for tests after immersion. EN2823 for tests after exposure to humid atmosphere. 7.2 Specimen measurement In the central section of the specimen, measure the width b to 0,1mm, then make three measurements of the thickness h to 0,02mm and calculate their a
32、rithmetic mean. 7.3 Support span Adjust the span, L, to comply with the following equation: L=(16 h) 1 where: Measure the span to 0,5%. 7.4 Test speed Set the test machine to the speed V, according to one of the following: V is specified; the rate of strain is specified; calculate V: where: Figure 1
33、 Detail of test apparatus Thickness “h”: (3 0,2)mm Width “b”: (15 0,5)mm Length “l”: (20 h) 1mm L is the span, in millimetres; h is the thickness of the specimen, in millimetres. V is the test speed, in millimetres per minute; Sr is the rate of strain, in units per minute; L is the span, in millimet
34、res; h is the thickness of the specimen, in millimetres.EN 2746:1998 BSI 05-1999 5 If there is no requirement, calculate V: V = K h where: 7.5 Test atmosphere Carry out the tests at (23 2)C and (50 5)% relative humidity. 7.6 Tests Position the specimen symmetrically with respect to the supports, ens
35、uring 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 deflection shall be simultaneously recorded. Note the values of the required characteristics:
36、at conventional deflection; at maximum force; at failure. 8 Expression of results 8.1 Flexural stress where: NOTEA more precise calculation of the flexural stress takes into account the horizontal component of the flexural moment: where: 8.2 Flexural modulus Examine the force/deflection curve and de
37、termine 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 line shall be drawn between10% and25% of the maximum force, see Figure 2. V is the test speed, in millimetres per minute; h is the thickness of the speci
38、men, in millimetres; K =0,5min 1 . B f is the flexural stress, in megapascals; F is the force applied, in newtons; L is the span, in millimetres; b is the width of the specimen, in millimetres; h is the thickness of the specimen, in millimetres. d is the deflection, in millimetres. Figure 2 Force/de
39、flection curveEN 2746:1998 6 BSI 05-1999 where: 8.3 Modes of failure During the flexural test, three different modes of failure may occur: failure initiated at the surface by the tensile stresses; failure initiated at the surface by the compression stresses; internal failure due to the shear stresse
40、s. 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 statistically homogeneous and great care is needed in the evaluation of the results. If specimens fail in an area othe
41、r than the area of the loading nose, the results shall not be taken into consideration. Carry out a set of retests in this case. 9 Test report It shall include the following: number of this standard; all data ensuring the traceability of the material (trade mark, identification marking, date of rece
42、ipt, batch number, etc.); all information regarding specimen preparation; specimen dimensions; span; radius of supports if it differs from2mm; test conditions; exposure time at the test temperature; specimen face in contact with the loading nose; test speed; force/deflection curve; flexural stress a
43、t conventional deflection; flexural strength; flexural stress at failure and mode of failure; flexural modulus; individual values, arithmetic mean and standard deviation of results of tests or retests (if applicable); any incident which may have affected the results. E f is the modulus, in megapasca
44、ls; L is the span, in millimetres; b is the width of the specimen, in millimetres; h is the thickness of the specimen, in millimetres; %F is a chosen difference in force, in newtons; %d is the difference in deflection corresponding to the difference in force%F, in millimetres.blankBS EN 2746:1998 BS
45、I 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions BritishStandards are up
46、dated by amendment or revision. Users of BritishStandards 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 grateful if anyone finding an inaccuracy or ambiguity while using this Britis
47、hStandard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover. Tel:02089969000. Fax:02089967400. BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest e
48、ditions of standards. Buying standards Orders for all BSI, international and foreign standards publications should be addressed to Customer Services. Tel:02089969001. Fax:02089967001. In response to orders for international standards, it is BSI policy to supply the BSI implementation of those that h
49、ave been published as BritishStandards, unless otherwise requested. Information on standards BSI provides a wide range of information on national, European and international standards through its Library and its Technical Help to Exporters Service. Various BSI electronic information services are also available which give details on all its products and services. Contact the Information Centre. Tel:02089967111. Fax:02089967048.
