1、DD CEN/TS15866:2009ICS 81.060.30NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWDRAFT FOR DEVELOPMENTAdvanced technicalceramics Ceramiccomposites Determination of thethermal diffusivity ofceramic fibresThis Draft for Developmentwas published under theauthority of the StandardsP
2、olicy and StrategyCommittee on 30 April2009 BSI 2009ISBN 978 0 580 63939 5Amendments/corrigenda issued since publicationDate CommentsDD CEN/TS 15866:2009National forewordThis Draft for Development is the UK implementation of CEN/TS15866:2009.This publication is not to be regarded as a British Standa
3、rd.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.Comments arising from the use of this Draft for Development arereques
4、ted 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 international organization so that a decision can betaken on its st
5、atus. 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 whether to support theconversion into an international Standard
6、, 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 participation in its preparation was entrusted to TechnicalCommittee RPI/13
7、, 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 for its correct application.Compliance with a British Standard
8、cannot confer immunityfrom legal obligations.DD CEN/TS 15866:2009TECHNICAL SPECIFICATIONSPCIFICATION TECHNIQUETECHNISCHE SPEZIFIKATIONCEN/TS 15866March 2009ICS 81.060.30English VersionAdvanced technical ceramics - Ceramic composites -Determination of the thermal diffusivity of ceramic fibresCramique
9、s techniques avances - Cramiquescomposites - Dtermination de la diffusion thermique desfibres cramiquesHochleistungskeramik - Keramische Verbundwerkstoffe -Bestimmung der Temperaturleitfhigkeit von keramischenFasernThis Technical Specification (CEN/TS) was approved by CEN on 3 February 2009 for prov
10、isional application.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
11、the existence of 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/
12、TS into an EN is 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, Slov
13、akia, Slovenia, 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
14、CEN national Members.Ref. No. CEN/TS 15866:2009: EDD CEN/TS 15866:2009CEN/TS 15866:2009 (E) 2 Contents Page Foreword 31 Scope 42 Normative references 43 Terms and definitions .44 Principle 55 Apparatus .55.1 Heat pulse source 55.2 Test chamber 55.3 Detectors 55.4 Data acquisition .66 Test specimens
15、67 Test specimen preparation .77.1 Machining and preparation .77.2 Number of test specimens 78 Procedure .78.1 Calibration of apparatus .78.2 Test procedure .79 Test validity 910 Results 911 Test report . 10Annex A (informative) Uni-dimensional thermal model . 11Annex B (informative) Methods 1 and 2
16、 . 13B.1 Method 1 13B.2 Method 2 15Bibliography . 17DD CEN/TS 15866:2009CEN/TS 15866:2009 (E) 3 Foreword This document (CEN/TS 15866:2009) 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
17、 that some of the elements 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 boun
18、d to announce this Technical 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, Swede
19、n, Switzerland and the United Kingdom. DD CEN/TS 15866:2009CEN/TS 15866:2009 (E) 4 1 Scope This Technical Specification specifies the conditions for the determination of the thermal diffusivity of single filaments of ceramic fibres parallel to the fibre axis. This Technical Specification applies to
20、continuous ceramic filaments taken from tows, yarns, braids and knittings. The experimental conditions are such that the material behaves in a homogeneous manner and that the heat transfer occurs only by thermal conduction. The method is applicable to materials which are physically and chemically st
21、able during the measurement, and covers the range of temperature between 100 K and 600 K. It is suitable for the measurement of thermal diffusivity values in the range between 10-4ms-1and 10-7m2s-1. 2 Normative references The following referenced documents are indispensable for the application of th
22、is document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 843-5:2006, Advanced technical ceramics Mechanical properties of monolithic ceramics at room temperature Part 5: Statistical
23、 analysis CEN/TR 13233:2007, Advanced technical ceramics Notations and symbols EN 60584-1, Thermocouples Part 1: Reference tables (IEC 60584-1:1995) EN ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories (ISO/IEC 17025:2005) ISO 3611, Micrometer callipers f
24、or external measurement 3 Terms and definitions For the purposes of this document, the terms and definitions given in CEN/TR 13233:2007 and the following apply. 3.1 thermal diffusivity a ratio of the thermal conductivity to the product of the bulk density and the specific heat capacity 3.2 transient
25、 half time ttime from the initiation of the pulse until the increase of the temperature on the back face of the test specimen reaches one half of the maximum temperature increase 3.3 thickness h dimension of the test specimen in the direction of heat transfer measurement DD CEN/TS 15866:2009CEN/TS 1
26、5866:2009 (E) 5 4 Principle One side of a plane and parallel test specimen is exposed to a uniformly distributed energy pulse that is of very short duration compared to the transient half time. The transient temperature rise, T, on the opposite face (back face) or a quantity directly proportional to
27、 T is recorded as a function of time, t (see Figure 1). The thermal diffusivity is obtained by comparing the experimental thermogram with a theoretical model, which is a uni-dimensional analytical thermal model, with two parameters, as described in Annex A. If other models are used, they are to be s
28、pecified in the test report. 5 Apparatus 5.1 Heat pulse source The heat pulse source may be a flash tube or a pulse laser. The pulse energy shall be as uniform as possible over the front face of the test specimen. 5.2 Test chamber The test chamber shall be a furnace or a cryostat, capable of operati
29、on within the temperature range required, or a draught proof enclosure for ambient temperature measurement. The design of the furnace shall meet the following requirements: a) homogeneous temperature on the test piece; b) in steady state conditions, the drift in temperature shall be less than 0,01 K
30、/s; c) the heat pulse source may be placed either inside the furnace or outside the furnace. In that case, the furnace shall be fitted with a window, transparent to the pulse radiation; d) the furnace shall contain a working area in which the spatial temperature gradient is sufficiently low ( 5 K) t
31、o ensure a consistent temperature across the sample. In addition, it shall provide suitable access for measurement of T or a quantity directly proportional to T on the back face of the test piece. NOTE 1 Measurement under vacuum reduces convection losses. NOTE 2 When the test is performed under gas,
32、 the test piece should be in a horizontal position in order to reduce convection effects of the gas on the specimen. 5.3 Detectors 5.3.1 Measurement of absolute temperature The temperature of the test piece shall be measured either with a thermocouple, in accordance with EN 60584-1, or with an optic
33、al pyrometer. 5.3.2 Transient detectors The detector shall be either an infrared detector or a thermocouple or any other means that does not disturb the measurement of the transient response of the specimen. It shall be capable of detecting changes of 0,05 K in the temperature of the test piece, wit
34、h a linear response over the range of temperature change less than or equal to 5 K. DD CEN/TS 15866:2009CEN/TS 15866:2009 (E) 6 It shall have a response time calculated as follows: ahtd2002,0 (1) where tdis the response time, in second (s); h is the thickness, in metre (m); a is the thermal diffusiv
35、ity, in square metre per second (m2.s-1). This condition shall be verified afterwards and if it is not met, the size of the specimen shall be increased. The infrared detector, when used, shall be of a type appropriate to the minimum test piece temperature, for example: a) Hg/Cd/Te cell, liquid nitro
36、gen cooled, for test specimen temperatures within the range 300 K to 800 K; b) PbS cell for test specimen temperatures above 500 K. Care shall be taken that the signal comes only from the central area of the back face, that is with a tolerance of 5 % of the diameter of the test specimen. Thermocoupl
37、es, when used, shall be of the separated junction type, the hot junction being the back face of the test piece. They shall be in accordance with EN 60584-1. Electrically non-conductive material shall be coated on the front face and on the rear face, with a thin coating of high thermal conductivity m
38、aterial in order to ensure accurate measurement of surface temperatures. In order to minimize heat losses, the use of the thermocouples with wires of the smallest possible diameter is recommended. NOTE The thermocouple type most often used is chromel-alumel for measurements from room temperature up
39、to 1 100 K. Semi-conducting couples may also be used: Bi2Te3from 90 K to 400 K. 5.4 Data acquisition The data acquisition system used may be analogue or digital. It shall be equipped with means of recording the temperature change versus time (before, during and after the pulse) and the time origin.
40、These means shall be accurate to within 0,02 ms. 6 Test specimens The size of the test specimens shall be fixed to meet the requirements for application of the chosen thermal model (for example like those described in Annex B). Generally, a disc-shape test specimen with a diameter between 8 mm and 2
41、5 mm is used. The thickness of the specimen shall be sufficient in order to avoid influence of material homogeneity. This shall be ensured by performing tests on two series of test specimens with a thickness ratio of about 2. Recommended starting thickness are between 1 mm and 10 mm. Homogeneous mat
42、erial behaviour can be assumed when the mean values of the thermal diffusivity determined from each series do not differ by more than 10 %. DD CEN/TS 15866:2009CEN/TS 15866:2009 (E) 7 7 Test specimen preparation 7.1 Machining and preparation Test specimens made from fibres shall be cut with their lo
43、ngitudinal axis coinciding with the fibre axis. A suggested method to prepare such test specimens is described in Annex B. It essentially consists of introducing fibres with a needle in a thermoplastic tube (as for example those used to protect electric cables). Once the required volume of fibres is
44、 reached, the plastic tube is heated and then shrinks, thereby exerting a sufficient pressure on the packed fibres to obtain a good degree of compaction as shown in the figures of Annex B. Disks can be cut to the desired thickness. The faces shall be flat and parallel. The plan parallelism of the tw
45、o faces shall be better than 0,05 mm. If the test specimen is transparent to the infra red radiation at the considered wavelength of the laser, a coating is necessary. This coating shall be opaque, absorbent, adherent and compatible with the test specimen. If the test specimen is non conductive and
46、if a thermocouple is used to measure the temperature on the back face, an adequate conductive coating shall be used. 7.2 Number of test specimens A minimum of three test specimens shall be tested at each test temperature. If a statistical evaluation is required, the number of test specimens shall be
47、 in accordance with EN 843-5:2006. 8 Procedure 8.1 Calibration of apparatus Although the measurement of thermal diffusivity is an absolute method, reference type materials with known diffusivities can be used to check the system. The homogeneity of the laser beam can be verified by photographic pape
48、r (Polaroid type). NOTE There is no recognized standard reference material for thermal diffusivity measurements, although several materials are used (for example POCO graphite, ARMCO iron). 8.2 Test procedure 8.2.1 The pulse duration shall be less than or equal to ah2003,0 to allow for direct applic
49、ation of the theoretical model. In general, this corresponds to a period less than 1/50 of transient half time (t1/2). NOTE When this condition is not met, a correction of the thermogram is possible by placing the time origin at the energetic barycentre tbof pulse (see Figure 1). DD CEN/TS 15866:2009CEN/TS 15866:2009 (E) 8 Key T temperature t time a pulse triggering b no heat losses Figure 1 Schematic representation of the temperature rise of the back face of the te
