CEN/TS 15866:2009

SLOVENSKI STANDARD
01-maj-2009
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Advanced technical ceramics - Ceramic composites - Determination of the thermal
diffusivity of ceramic fibres
Hochleistungskeramik - Keramische Verbundwerkstoffe - Bestimmung der
Temperaturleitfähigkeit von keramischen Fasern
Céramiques techniques avancées - Céramiques composites - Détermination de la
diffusion thermique des fibres céramiques
Ta slovenski standard je istoveten z: CEN/TS 15866:2009
ICS:
81.060.30 Sodobna keramika Advanced ceramics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL SPECIFICATION
CEN/TS 15866
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
March 2009
ICS 81.060.30
English Version
Advanced technical ceramics - Ceramic composites -
Determination of the thermal diffusivity of ceramic fibres
Céramiques techniques avancées - Céramiques Hochleistungskeramik - Keramische Verbundwerkstoffe -
composites - Détermination de la diffusion thermique des Bestimmung der Temperaturleitfähigkeit von keramischen
fibres céramiques Fasern
This Technical Specification (CEN/TS) was approved by CEN on 3 February 2009 for provisional 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 their
comments, particularly on the question whether the CEN/TS can be converted into a European Standard.
CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS available
promptly 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 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, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2009 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 15866:2009: E
worldwide for CEN national Members.

Contents Page
Foreword .3
1 Scope .4
2 Normative references .4
3 Terms and definitions .4
4 Principle .5
5 Apparatus .5
5.1 Heat pulse source .5
5.2 Test chamber .5
5.3 Detectors .5
5.4 Data acquisition .6
6 Test specimens .6
7 Test specimen preparation .7
7.1 Machining and preparation .7
7.2 Number of test specimens .7
8 Procedure .7
8.1 Calibration of apparatus .7
8.2 Test procedure .7
9 Test validity .9
10 Results .9
11 Test report . 10
Annex A (informative) Uni-dimensional thermal model . 11
Annex B (informative) Methods 1 and 2 . 13
B.1 Method 1 . 13
B.2 Method 2 . 15
Bibliography . 17

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 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 bound 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,
Sweden, Switzerland and the United Kingdom.
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 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 stable during the measurement,
and covers the range of temperature between 100 K and 600 K. It is suitable for the measurement of thermal
-4 -1 -7 2 -1
diffusivity values in the range between 10 m²·s and 10 m·s .
2 Normative references
The following referenced documents are indispensable for the application of this 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 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 for 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 half time
t
½
time 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
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 ∆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 specified 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 operation 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/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) to 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, 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 optical 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, with a linear response over the range of temperature change less
than or equal to 5 K.
It shall have a response time calculated as follows:
h
t ≤ 0,002 (1)
d
a
where
t is the response time, in second (s);
d
h is the thickness, in metre (m);
2 -1
a is the thermal diffusivity, in square metre per second (m .s ).
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 nitrogen 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.
Thermocouples, 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 material 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 to
1 100 K. Semi-conducting couples may also be used: Bi Te from 90 K to 400 K.
2 3
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. 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 25 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 material behaviour can be as
...