CEN TS 15881-2009 Advanced technical ceramics - Ceramic composites - Determination of the fibre matrix interfacial frictional shear stress at room temperature by tensile tests on m.pdf

1、DD CEN/TS15881:2009ICS 81.060.30NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWDRAFT FOR DEVELOPMENTAdvanced technicalceramics Ceramiccomposites Determination of thefibre/matrix interfacialfrictional shear stressat room temperatureby tensile tests onmini-compositesThis Draft f

2、or Developmentwas published under theauthority of the StandardsPolicy and StrategyCommittee on 30 June2009. BSI 2009ISBN 978 0 580 63938 8Amendments/corrigenda issued since publicationDate CommentsDD CEN/TS 15881:2009National forewordThis Draft for Development is the UK implementation of CEN/TS15881

3、:2009.This publication is not to be regarded as a British Standard.It is being issued in the Draft for Development series of publications andis of a provisional nature. It should be applied on this provisional basis,so that information and experience of its practical application can beobtained.Comme

4、nts arising from the use of this Draft for Development arerequested so that UK experience can be reported to the internationalorganization responsible for its conversion to an international standard.A review of this publication will be initiated not later than 3 years afterits publication by the int

5、ernational organization so that a decision can betaken on its status. Notification of the start of the review period will bemade in an announcement in the appropriate issue of Update Standards.According to the replies received by the end of the review period,the responsible BSI Committee will decide

6、 whether to support theconversion into an international Standard, to extend the life of theTechnical Specification or to withdraw it. Comments should be sent tothe Secretary of the responsible BSI Technical Committee at BritishStandards House, 389 Chiswick High Road, London W4 4AL.The UK participati

7、on in its preparation was entrusted to TechnicalCommittee RPI/13, Advanced technical ceramics.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are responsible

8、 for its correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.DD CEN/TS 15881:2009TECHNICAL SPECIFICATIONSPCIFICATION TECHNIQUETECHNISCHE SPEZIFIKATIONCEN/TS 15881May 2009ICS 81.060.30English VersionAdvanced technical ceramics - Ceramic composites -Dete

9、rmination of the fibre/matrix interfacial frictional shear stressat room temperature by tensile tests on mini-compositesCramiques techniques avances - Cramiquescomposites - Dtermination de la contrainte de frottementen cisaillement linterface fibre/matrice tempratureambiante - Essais de traction sur

10、 minicompositesHochleistungskeramik - Keramische Verbundwerkstoffe -Bestimmung der Reibschubspannung an der GrenzflcheFaser/Matrix bei Raumtemperatur mit Hilfe vonZugversuchen an Mini-VerbundwerkstoffenThis Technical Specification (CEN/TS) was approved by CEN on 28 March 2009 for provisional applica

11、tion.The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to submit theircomments, particularly on the question whether the CEN/TS can be converted into a European Standard.CEN members are required to announce the existence o

12、f this CEN/TS in the same way as for an EN and to make the CEN/TS availablepromptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the CEN/TS)until the final decision about the possible conversion of the CEN/TS into an EN i

13、s reached.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia,

14、 Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: Avenue Marnix 17, B-1000 Brussels 2009 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Me

15、mbers.Ref. No. CEN/TS 15881:2009: EDD CEN/TS 15881:2009CEN/TS 15881:2009 (E) 2 Contents Page Foreword 3 1 Scope 4 2 Normative references 4 3 Terms, definitions and symbols .4 4 Principle 6 4.1 Method A .6 4.2 Method B .7 5 Significance and use .7 6 Apparatus .8 6.1 Test machine 8 6.2 Load train 8 6.

16、3 Data recording system 8 7 Test specimens 8 8 Test specimen preparation .9 8.1 General 9 8.2 Window type specimen .9 8.3 Cylindrical end type specimen 10 9 Number of test specimens . 10 10 Test procedure 10 10.1 Determination of the gauge length . 10 10.2 Determination of the cross section area 10

17、10.3 Determination of the fibre volume fraction 10 10.4 Determination of the matrix volume fraction . 10 10.5 Determination of the number of cracks at saturation, N 10 11 Testing technique . 11 12 Test validity . 11 13 Calculations . 11 13.1 Tensile stress 11 13.2 Method A 12 13.3 Method B 12 14 Tes

18、t report . 15 Bibliography . 16 DD CEN/TS 15881:2009CEN/TS 15881:2009 (E) 3 Foreword This document (CEN/TS 15881:2009) has been prepared by Technical Committee CEN/TC 184 “Advanced technical ceramics”, the secretariat of which is held by BSI. Attention is drawn to the possibility that some of the el

19、ements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to announce this T

20、echnical Specification: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and t

21、he United Kingdom. DD CEN/TS 15881:2009CEN/TS 15881:2009 (E) 4 1 Scope This CEN Technical Specification specifies a method to determine the fibre-matrix bonding characteristics of ceramic matrix composite materials at room temperature, by the measurement of the interfacial frictional shear stress ob

22、tained by cycled tension on mini-composites. A mini-composite is a unidirectional composite reinforced with a single tow. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undate

23、d references, the latest edition of the referenced document (including any amendments) applies. CEN/TR 13233:2007, Advanced technical ceramics Notations and symbols EN ISO 7500-1, Metallic materials Verification of static uniaxial testing machines Part 1: Tension/compression testing machines Verific

24、ation and calibration of the force measuring system (ISO 7500-1:2004) 3 Terms, definitions and symbols For the purposes of this European Technical Specification, the terms, definitions and symbols given in CEN/TR 13233:2007 and the following apply. 3.1 fibre radius Rffor circular fibres Rf is the me

25、an radius of the fibres; for non circular fibres, Rf is replaced by FS3.2 fibre cross-section area SFmean cross section area of the fibre 3.3 cross section area A0cross section area of the test specimen 3.4 gauge length L0 initial distance between the two gripped ends of the test specimen 3.5 Volume

26、 fraction 3.5.1 fibre volume fraction Vffraction of fibre content in the test specimen that can be determined using microscopy and image analysis or any other adequate method DD CEN/TS 15881:2009CEN/TS 15881:2009 (E) 5 3.5.2 matrix volume fraction Vmfraction of matrix content in the test specimen th

27、at can be determined using microscopy and image analysis or any other adequate method 3.6 tensile force Ftensile force on the test specimen 3.7 maximum tensile force FM highest recorded tensile force on the test specimen when tested to failure 3.8 initial tensile force at unloading Fp tensile force

28、on the test specimen at initiation of unloading 3.9 tensile force at matrix crack saturation Fs tensile force on the test specimen at the end of the non linear domain of the force-displacement curve (see Figure 1) 3.10 cycle or hysteresis loop force-displacement curve obtained when loading the test

29、specimen up to a given defined load and then unloading it to zero load (see Figure 2) 3.11 area of the hysteresis loop S area comprised between the unloading and the reloading force-displacement curve during a cycle (see Figure 2) 3.12 width of a hysteresis loop difference in measured displacements

30、on unloading and reloading, at a same force, during a cycle (see Figure 2) 3.13 tensile stress tensile force in the unloading-reloading sequence that corresponds to divided by the cross section area Ao 3.14 initial stress at unloading ptensile force at initiation of unloading divided by the cross se

31、ction area Ao3.15 stress at matrix crack saturation stensile force at the end of non linear domain of the monotonic loaded force-displacement curve, divided by the cross-section area Ao(force level Fsin Figure 1) DD CEN/TS 15881:2009CEN/TS 15881:2009 (E) 6 3.16 longitudinal deformation L increase of

32、 the gauge length under a given force 3.17 total compliance Ctinverse of the slope in the initial linear part of the force/displacement curve 3.18 load train compliance Clratio of the cross-head displacement to the force excluding any test specimen contribution to the corresponding force during the

33、tensile test 3.19 interfacial frictional shear stress finterfacial frictional shear stress at initiation of sliding between fibre and matrix 3.20 mean spacing distance of matrix cracks lsmean spacing distance between transverse cracks after matrix cracking saturation 4 Principle The mini-composite i

34、s loaded monotonically in tension parallel to the fibre direction at a constant displacement rate. 4.1 Method A If saturation of matrix cracking can be detected on the force-displacement curve, then the interfacial frictional shear stress is obtained from the force at crack saturation, Fs(see Figure

35、 1). YXKey X Displacement Y Force Figure 1 Force-displacement curve obtained during a tensile test (Method A) DD CEN/TS 15881:2009CEN/TS 15881:2009 (E) 7 4.2 Method B If crack saturation cannot be detected, tensile test shall be performed with unloading/reloading cycles with increasing force amplitu

36、de. The area or the width of the hysteresis loops is directly related to the interfacial frictional shear stress (see Figure 2). YX1201 0009008007006005004003002001000 0,1 0,2 0,3 0,4 0,50,6 0,7 0,8 0,9 1Key X Displacement (mm) Y Force (N) 1 reloading 2 unloading Figure 2 Schematic diagram showing l

37、oading-unloading cycles (hysteresis loops) obtained during a tensile test (Method B) 5 Significance and use Ceramic matrix composites display non-brittle behaviour under tensile loading conditions only when the fibre/matrix bond is carefully designed. It is essential that the fibre matrix bond is no

38、t too strong, which would cause the composite to be brittle. It should also not be too weak, which would cause the composite to be unable to withstand high stresses. Interfaces must exhibit a certain resistance to cracking to allow, firstly, matrix crack arrest and damage tolerance, and secondly, lo

39、ad transfers from the fibre to the matrix. Characteristics of fibre/matrix interfaces are therefore of primary importance in composite engineering, in composite evaluation and in prediction of behaviour and performance. A mini-composite is a unidirectional composite reinforced with a bundle of paral

40、lel fibres. Mini-composites are a simplification of composites. They contain the basic constituents of composites and their response under load is not obscured by texture effects. They are thus used in the investigation of microstructure-property relationships in textile composites and in the determ

41、ination of interface characteristics. The important characteristic in the mechanical behaviour of composites is the interfacial frictional shear stress. It measures the ability of an interface to arrest the matrix cracks, and then to transfer stresses from the fibre to the matrix. High interface she

42、ar stresses denote efficient load transfers; they reflect the presence of short debond cracks which is indicative of a strong fibre matrix bond. On the contrary, low interface shear stresses denote poor load transfer; they reflect the presence of long debond cracks which is indicative of a weak fibr

43、e matrix bond. DD CEN/TS 15881:2009CEN/TS 15881:2009 (E) 8 The presence of strong interfaces is therefore sought for those composites with a stiff matrix which is able to share the applied load. The corresponding force-displacement curve exhibits a non-linear domain. The hysteresis loops are more or

44、 less widely opened depending on the magnitude of interfacial frictional shear stress. Tensile tests on mini-composites are thus appropriate to evaluate the capability of the matrix to carry a fraction of applied load, and to determine the interfacial frictional shear stress. When the matrix is comp

45、liant compared to the fibres, most of the load is carried by the fibres and the interface does not play a significant role in the composite mechanical behaviour. The interfacial frictional shear stresses are low. The force-displacement curves are predominantly linear. Three different situations may

46、arise: a) the force-displacement curve is predominantly linear. If the matrix is stiffer than the fibres, this indicates a brittle behaviour. The fibres are too strongly bonded to the matrix, and the composite behaviour controlled by fibres cannot be achieved. In this case, the strain-to-failure is

47、generally as small as 0,1 %. b) the force-displacement curve is predominantly linear but the matrix is far less stiff than the fibres. Most of the load is thus carried by fibres. Interface does not play a significant role when cracks appear in the matrix. The interfacial frictional shear stress is l

48、ow. c) the force-displacement curve is predominantly non-linear. This is obtained with a matrix stiffer than the fibres. The matrix is able to carry a significant fraction of the applied load. Interfaces play a significant role when cracks are created in the matrix. They allow load transfer and part

49、ially unloading of the matrix. Therefore, this test allows the class of material to be identified when stiffness of the matrix is not known and the interfacial frictional shear stress to be measured when a non-linear behaviour is obtained. If a compliant matrix behaviour is evident, then an alternative method should be used to determine the interfacial frictional shear stress. 6 Apparatus 6.1 Test machine The machine shall be equipped with a system for measuring the force applied to the test specimen which shall conform to grade 1 according t