SIST-TS CEN/TS 1007-7:2007

SLOVENSKI STANDARD
SIST-TS CEN/TS 1007-7:2007
01-januar-2007
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Advanced technical ceramics - Ceramic composites. Methods of test for reinforcements -
Part 7: Determination of the distribution of tensile strength and of tensile strain to failure
of filaments within a multifilament tow at high temperature
Hochleistungskeramik - Keramische Verbundwerkstoffe - Verfahren zur Prüfung von
Verstärkungen - Teil 7: Bestimmung der Verteilung von Zugfestigkeit und Zugdehnung
von Fasern im Faserbündel bei hoher Temperatur
Céramiques techniques avancées - Céramiques composites - Méthodes d'essai pour
renforts - Partie 7 : Détermination de la distribution de la résistance en traction et de la
déformation de traction a la rupture des filaments dans un fil a haute température
Ta slovenski standard je istoveten z: CEN/TS 1007-7:2006
ICS:
81.060.30 Sodobna keramika Advanced ceramics
SIST-TS CEN/TS 1007-7:2007 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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TECHNICAL SPECIFICATION
CEN/TS 1007-7
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
September 2006
ICS 81.060.30

English Version
Advanced technical ceramics - Ceramic composites. Methods of
test for reinforcements - Part 7: Determination of the distribution
of tensile strength and of tensile strain to failure of filaments
within a multifilament tow at high temperature
Céramiques techniques avancées - Céramiques Hochleistungskeramik - Keramische Verbundwerkstoffe -
composites - Méthodes d'essai pour renforts - Partie 7 : Verfahren zur Prüfung von Verstärkungen - Teil 7:
Détermination de la distribution de la résistance en traction Bestimmung der Verteilung von Zugfestigkeit und
et de la déformation de traction à la rupture des filaments Zugdehnung von Fasern im Faserbündel bei hoher
dans un fil à haute température Temperatur
This Technical Specification (CEN/TS) was approved by CEN on 17 July 2006 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, 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.
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Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2006 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 1007-7:2006: E
worldwide for CEN national Members.

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CEN/TS 1007-7:2006 (E)
Contents Page
Foreword.3
1 Scope .4
2 Normative references .4
3 Terms and definitions .5
4 Symbols and abbreviations .7
5 Principle.7
6 Significance and use .8
7 Apparatus .8
7.1 Test machine.8
7.2 Load train.8
7.3 Adhesive .8
7.4 Test chamber.9
7.5 Set-up for heating .9
7.6 Temperature measurement.9
7.7 Data recording system .9
8 Test procedure.9
8.1 Test specimens.9
8.2 Test specimen preparation.10
8.3 Number of test specimens.12
8.4 Test Procedure.13
8.5 Calculation of results .16
Annex A (informative) Derivation of the Young’s modulus of the hot part of the tow .25
Bibliography .26

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CEN/TS 1007-7:2006 (E)
Foreword
This document (CEN/TS 1007-7:2006) has been prepared by Technical Committee CEN/TC 184 “Advanced
technical ceramics”, the secretariat of which is held by BSI.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to announce this Technical Specification: Austria, Belgium, 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.
EN 1007 Advanced technical ceramics — Ceramic composites. Methods of test for reinforcements has been
prepared in 7 parts:
Part 1: Determination of size content
Part 2: Determination of linear density
Part 3: Determination of filament diameter and cross-section area
Part 4: Determination of tensile properties of filaments at ambient temperature
Part 5: Determination of distribution of tensile strength and of tensile strain to failure of filaments within a
multifilament tow at ambient temperature
Part 6: Determination of tensile properties of filaments at high temperature
Part 7: Determination of the distribution of tensile strength and tensile strain to failure of filaments within a
multifilament tow at high temperature
At the time of publication of this Technical Specification, Part 6 was available as a European Prestandard.

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CEN/TS 1007-7:2006 (E)
1 Scope
This Technical Specification specifies the conditions, apparatus and procedure for determining the distribution
of tensile strength and tensile strain to failure of ceramic filaments in multifilament tows at high temperature in
air, vacuum or a controlled inert atmosphere.
This Technical Specification applies to tows of continuous ceramic filaments, which are assumed to act freely
and independently under loading and behave linearly elastic up to failure.
Two methods are proposed depending on the temperature of the ends of the tow:
a) hot end method;
NOTE 1 The application of the hot end method is restricted by ceramic glues with sufficient shear strengths at the
test temperature. Current experience with this technique is limited to 1 300 °C, because of the maximum application
temperature of ceramic glues.
b) cold end method.
NOTE 2 The cold-end method is limited to 1 700 °C in air and 2 000 °C in inert atmosphere because of the limits of
furnaces.
Both methods allow for a failure rate in the determination of distribution of tensile strain and tensile strength.
2 Normative references
This Technical Specification 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 these publications apply to
this Technical Specification only when incorporated in it by amendment or revision. For undated references
the latest edition of the publication referred to applies (including amendments).
ENV 843-5, Advanced technical ceramics — Monolithic ceramics. Mechanical tests at room temperature —
Statistical analysis
EN 1007-2, Advanced technical ceramics — Ceramic composites — Methods of test for reinforcement —
Part 2: Determination of linear density
EN 60584-1, Thermocouples — Part 1: reference tables (IEC 60584-1:1995)
EN 60584-2, Thermocouples — Part 2: tolerances (IEC 60584-2:1982 + A1:1989)
EN ISO 7500-1, Metallic materials — Verification of static uniaxial testing machines — Part 1: Tension
compression testing machines — Verification and calibration of the force-measuring system (ISO 7500-
1:2004)
ENV 13233:1998, Advanced technical ceramics — Ceramic composites — Notations and symbols
ISO 10119, Carbon fibre — Determination of density
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CEN/TS 1007-7:2006 (E)
3 Terms and definitions
For the purposes of this Technical Specification, the terms and definitions given in ENV 13233:1998 and the
following apply.
3.1
test temperature
T
temperature of the filament at the centre of the gauge length
3.2
lengths
initial distances between two reference points on the tow, disregarding thermal and mechanical strains
3.2.1
gauge length
L

0
part of the tow between the gripped ends, where the temperature variation is within 20 K of the test
temperature
3.2.2
test specimen length
L .
f
initial distance between the gripped ends of the tow
3.2.3
uniformly heated length
L
h
length of the heated zone within which the temperature variation is within 20 K of the test temperature
3.2.4
cold zone length
L
c
length of the tow, which is not uniformly heated
3.3
initial cross sectional area
A
0
sum of the cross sectional areas of all the filaments in the tow
3.4
tow elongation
∆L
increase of the gauge length between the two reference points on the tow
3.5
tow strain
ε
ratio of the tow elongation ∆L to the gauge length L
o
3.6
tow maximum tensile force
F
tow
highest recorded tensile force on the test specimen when tested to failure
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CEN/TS 1007-7:2006 (E)
3.7
tow strength
σ

tow
ratio of the tow maximum tensile force to the cross sectional area of all unbroken filaments at maximum
tensile force, F

tow
3.8
force at step j
F
j
force applied on the test specimen at step j
3.9
filament strain
ε
j
strain at step j in the non-linear parts of the force-displacement curve
3.10
filament strength
σ
j
ratio of the tensile force to the cross sectional area of all unbroken filaments at step j in the non-linear parts of
the force-displacement curve
3.11
average filament rupture strain

ε
r
statistical average rupture strain of the filaments in the tow for each test determined from the Weibull strain
distribution parameters of the filaments
3.12
overall average filament rupture strain

ε
r
arithmetic mean of the average filament rupture strains
3.13
average filament strength

σ
r
statistical average strength of the filaments in the tow for each test determined from the Weibull strength
distribution parameters of the filaments
3.14
overall average filament strength

σ
r
arithmetic mean of the average filament strengths
3.15 Compliances
3.15.1
initial total compliance
C
t
inverse  slope of the linear part of the force-displacement curve
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CEN/TS 1007-7:2006 (E)

3.15.2
instantaneous total compliance
C
t,j
inverse slope of the secant at any point j in the non-linear part of the force-displacement curve
NOTE The slope is taken from a line through any point of the force-displacement curve and the intersection point of
the line of the initial total compliance with the abscissa (true origin).
3.15.3
load train compliance
C
l
ratio of the cross head displacement to the force, excluding any contribution of the test specimen to the
displacement during the tensile test
3.15.4
cold zone compliance
C
c
ratio of the increase in test specimen length in the cold zone length L to the corresponding force during the
c
tensile test
3.15.5
hot zone compliance
C
h
ratio of the increase in test specimen length in the uniformly heated length L to the corresponding force
h
during the tensile test
4 Symbols and abbreviations
C is the instantaneous total compliance of the tow at maximum tensile force.
tow
 is the elastic modulus (Young’s modulus) of the uniformly heated part of the tow.
E
h
E is the elastic modulus (Young’s modulus) of the cold part of the tow.
c
5 Principle
A multifilament tow is heated to the test temperature and loaded in tension. The test is performed at a
constant displacement rate up to failure. Force and cross-head displacement are measured and recorded
simultaneously. When required, the longitudinal deformation is derived from the cross-head displacement
using a compliance correction. From the force-displacement curve, the two-parameter Weibull distribution of
the rupture strain and distribution of the rupture strength of the filaments is obtained by sampling the non-
linear parts of the curve at discrete intervals j, which correspond to an increasing number of failed filaments in
the tow. The test duration is limited to reduce time dependent effects.
Two methods can be used. The first method (hot-end method) consists of heating the tow over its total length.
The second method (cold end method) consists of heating only a part of the test specimen length, the
temperature profile of which is used to define the gauge length. The application of this method requires the
realisation of three different heated zone lengths.
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CEN/TS 1007-7:2006 (E)
6 Significance and use
The measurement of strain directly on the tow is difficult, so it is usually achieved indirectly via a compliance
measurement which includes contributions of the loading train, grips, tab materials, etc. These contributions
shall be taken into account to achieve a correct analysis. When it is possible to measure the tow elongation
directly (by using a suitable extensometer system) this correction is not needed. The calculation of the results
in clause 7 also applies in this case by setting the load train compliance equal to zero.
The evaluation method is based on an analysis of the non-linear increasing and decreasing parts of the force
displacement curve. These parts are caused by progressive filament failures during the test, which is
encouraged by a high stiffness of the loading and gripping system. When the force-displacement curve does
not show these non-linear parts, the evaluation method of this Technical Specification cannot be applied.
The distribution of filament failure strains does not depend on the number of filaments in the tow and is hence
not affected by the number of filaments which are broken before the test. The determination of the filament
strength distribution requires knowledge of the initial cross sectional area of the tow and because the number
of unbroken filaments within the tow prior to the test is usually unknown, the values for the filament strength
represent a lower bound to these quantities. Also, the variation in the filament diameter which affects the
strength values, is not accounted for.
a) Hot end method: for the hot end method, the gauge length, defined as the uniformly heated length, equals
the test specimen length.
NOTE 1 Subjecting the whole length of a tow to temperatures well above 1 000 °C, however, makes it difficult to
fix the ends of the test specimen into appropriate temperature proof extensions.
b) Cold end method: for the cold end method, the test specimen length is the sum of the cold and the hot
parts of the tow, with the gauge length is defined as the uniformly heated length. The temperature
gradient zones along the tow axis are neglected.
NOTE 2 In this method, the problems associated with heating the clamps are avoided by heating only a central
part of the tow and by keeping the junction at the ends of the test specimen at room temperature. This allows similar test
specimen designs and organic resins to be used as in the room temperature test method (EN 1007-5). The interpretation
of the results can be complicated by the superposition of the contributions from the cold and the hot tow zones.
The ratio of the hot part of the tow and the test specimen length is to be adjusted so as to keep the grips at
room temperature, whilst the uniformly heated zone shall not be too short, in order to ensure a significant
influence of the hot part on the overall failure behaviour of the tow.
7 Apparatus
7.1 Test machine
The test machine shall be equipped with a system for measuring the force applied to the test specimen, which
shall conform to grade 1 according to EN ISO 7500-1. Additionally, the machine shall be equipped with a
system for measuring the cross head displacement with an accuracy better than 1 µm.
7.2 Load train
The grips shall align the test specimen with the direction of the force. Slippage of the test specimen in the
grips shall be prevented as well as avoiding pre-damage due to gripping. The load train performance including
the alignment system and the force transmitting system shall not change because of heating.
7.3 Adhesive
A suitable adhesive for fixing the tow ends to the grip, such as ceramic cement (hot-end method) or epoxy
resin (cold-end method).
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CEN/TS 1007-7:2006 (E)
7.4 Test chamber
7.4.1 General
When testing under inert conditions, a gas-tight chamber allows for proper control of the test environment. The
installation shall be such that the variation of the load due to the variation of pressure is less than 1 % of the
scale of the load cell being used.
7.4.2 Gaseous environment
The gaseous environment shall be chosen depending on the material to be tested and on the test temperature.
The level of pressure shall be chosen based on the material to be tested, the test temperature, and on the
type of gas. The gaseous environment shall not induce chemical and/or physical instability to the filament
material.
7.4.3 Vacuum chamber
The level of vacuum shall not induce chemical and/or physical instability of the filament material.
7.5 Set-up for heating
The set-up for heating shall be constructed in such a way that in a sufficiently extended gauge length the
temperature variation is minimised and less than 20 K at the test temperature.
7.6 Temperature measurement
For temperature measurement, either thermocouples conforming to EN 60584 Parts 1 and 2 shall be used or,
where thermocouples not conforming to EN 60584 or pyrometers are used, they shall be appropriately
calibrated.
7.7 Data recording system
A calibrated recorder may be used to record force-displacement curves. The use of a digital data recording
system combined with an analogue recorder is recommended.
8 Test procedure
8.1 Test specimens
Hot end method
In high temperature hot end tests, it is assumed that the test specimen is exposed to isothermal conditions
along its whole length and that the test temperature is equal to the furnace temperature. According to these
hypotheses, the gauge length L is equal to the test specimen length L .
0 f
Test specimens with a gauge length of 100 mm shall be used to establish force-displacement curves. To
determine the load train compliance C additional test specimens with gauge lengths of 50 mm and 150 mm
l
shall be used.
The gauge length shall be measured with an accuracy of ± 1 mm.


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CEN/TS 1007-7:2006 (E)
Cold end method
In the cold end method, the sum of the lengths of the cold and the uniformly heated part of the tow equals the
test specimen length L = L + L and the length of the hot part defines the gauge length, i.e. gradient zones
f c h
are neglected. Therefore, the compliance method shall be modified accordingly. Three different lengths of the
hot part of the tow should be used, e.g. 20 mm, 40 mm, and 60 mm, with the medium length used to establish
the force displacement curves.
NOTE The maximum length of the tow is determined by the apparatus used. The choice of the minimum length of the
uniformly heated part of the tow is made with a view to minimizing uncertainties of the characteristics of the hot part, which
are due to parasitic influences from the not uniformly heated parts.
8.2 Test specimen preparation
Extreme care shall be taken while preparing the test specimen to ensure that the procedure is repeatable for
all test specimens and to avoid handling damage. When a ceramic cement is used, the same type of cement
and bonding length shall be used to prepare all test specimen of a given series. Specimens shall be handled
with care during preparation to avoid breaking filaments.
High repeatability in specimen preparation is required in order to allow the correct determination of the load
train compliance.
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CEN/TS 1007-7:2006 (E)
Hot end method
An example for hot end gripping is given in Figure 1. The appropriate glue (e.g. polymeric with graphite filler)
is introduced by syringe into two graphite cylinders at each end of the test specimen.
Dimensions in millimetres

(actual example)

Key
a High temperature glue
b Filament tow test piece

NOTE 1 The material is graphite.
Figure 1 — Example of hot end gripping
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CEN/TS 1007-7:2006 (E)
Cold end method
An example of a prepared cylindrical end type specimen is shown in Figure 2. While using an appropriate glue
for gripping, care shall be taken to obtain a well defined fibre length L . For this purpose, additional transparent
f
heat shrinks are fixed to the untwisted multifilament stretched tow at a well defined position with superglue.
These heat shrinks also prevent the fibres from coming into contact with the glue. Both ends of the tow are
fixed in small diameter cylindrical tubes with the glue. The diameter of the cylindrical tubes shall be as small
as possible, compatible with the size of the tow.

Key
a Superglue, defines L
f
b Transparent heat shrink
c Specimen fixing
d Fibre bundle
e Transparent heat shrink
f Tube
g Heat shrink
Figure 2 — Example of a cold end gripping
8.3 Number of test specimens
For each test condition, three valid test results at an intermediate gauge length (100 mm for the hot end
method), as specified in 8.4.4, are required. Three additional valid test results at a shorter gauge length
(50 mm for hot end), and three valid test results at a longer gauge length (150 mm for hot end) are required in
order to establish the load-train compliance C .
l
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CEN/TS 1007-7:2006 (E)
8.4 Test Procedure
8.4.1 Determination of the temperature profile
a) Hot end method
The following procedures shall be carried out under actual test conditions. Prior to testing, the temperature
profile inside the furnace shall be established over the temperature range of interest. This shall be done by
measuring the temperature at a minimum of three locations within the furnace, which correspond to the ends
and the centre of the maximum gauge length.
NOTE 1 The temperature profile may be determined without the test specimen mounted inside the furnace, at the
anticipated position of the ends of the test specimen corresponding to the maximum gauge length and mid-way between
them.
During a series of tests, the test temperature is determined indirectly from the temperature indicated by the
temperature control device. The relation between the control temperature and the test temperature is
established over the range of temperatures of interest.
NOTE 2 Usually the determination of the temperature profile and the relation between control temperature and
test temperature are established simultaneously.
b) Cold end method

Key
a Coil
b Susceptor
c Specimen
d Grip
Figure 3 — Schematic drawing of a cold end method device
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CEN/TS 1007-7:2006 (E)

Figure 4 — Example of a temperature profile measured along the susceptor axis in a cold end method
device
NOTE 3 For the cold end method, only the central part of the tow is heated, e.g. indirectly by induction heating. In
this case, a thermally insulated susceptor with a sufficiently small diameter is heated by induction and heats up the
specimen and environment within the susceptor. The length of the coil exceeds the maximum susceptor length to provide
a homogenous temperature of the susceptor (see Figure 3).
The axial temperature profile can be measured by thermocouples which are moved along the tow axis. An
example of such a temperature profile is given in Figure 4 where the length of the susceptor,
l = 20 mm. The gauge length, defined as the part of the tow L , where the axial variation of the
susceptor h
temperature is less than 20 K, is to be extracted separately for each susceptor length from the appropriate
temperature profile. The offset, ∆T between the control temperature of the susceptor and the maximum
offset
temperature measured along the centre axis of the susceptor depends on the thermal conductivity of the
specimen. Therefore, ∆T during an actual test with a ceramic tow tends to be smaller than what is
offset
measured by a metallic thermocouple.
8.4.2 Test set-up: other considerations
8.4.2.1 Determination of the initial cross sectional area
To determining the filament strength distribution, as well as the elastic modulus on the specimens with the
intermediate gauge length, the initial cross sectional area of the multifilament tow is calculated from the linear
density which is determined according to EN 1007-2 and from the density determined by ISO 10119.
Alternatively, the initial cross sectional area can be determined by measuring the number and the average
diameter of the filaments in the tow, for instance through image analysis.
8.4.2.2 Determination of the test specimen
As the dimensions of the test specimen vary with temperature, the variation is very difficult to measure.
Therefore, the gauge length is measured to an accuracy of ± 1 mm at room temperature (hot end method) or
derived from the measured temperature profile (cold end method).
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CEN/TS 1007-7:2006 (E)
8.4.3 Testing technique
8.4.3.1 General
Perform the following steps in sequential order.
8.4.3.2 Test specimen mounting
Mount the test specimen in the load train with its longitudinal axis coinciding with that of the test machine.
Care shall be taken not to induce torsional loads or damage to the test specimen.
8.4.3.3 Selection of strain rate (displacement rate)
-4 -1 -5 -1
A strain rate between 10 s and 10 s shall be used for all the tests. The corresponding crosshead
displacement rate is determined from a test on a specimen with the intermediate gauge length (100 mm for
hot end) performed according to 8.4. The force-displacement curve obtained from this test shall have the
appearance shown in Figure 6. In particular, the curve shall be linear followed by a non-linear rising part, as
well as a non-linear decreasing part. When the force-displacement curve does not meet these criteria, tests
...