SIST EN 1007-7:2010
(Main)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
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
This European standard 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 part of EN 1007 applies to tows of continuous ceramic filaments, which are assumed to act freely and independently under loading and behave linearly elastic up to failure.
Hochleistungskeramik - Keramische Verbundwerkstoffe - Verfahren zur Prüfung der Faserverstärkungen - Teil 7: Bestimmung der Verteilung von Zugfestigkeit und Zugdehnung von Fasern im Faserbündel bei hoher Temperatur
Diese Europäische Norm legt die Bedingungen, Geräte und das Verfahren zur Bestimmung der Verteilung der
Zugfestigkeit und Zugdehnung bis zum Bruch von keramischen Fasern in Faserbündeln bei hoher Temperatur
in Luft, unter Vakuum oder in einer geregelten inerten Atmosphäre fest.
Dieser Teil der EN 1007 gilt für Bündel keramischer Endlosfasern, von denen angenommen wird, dass sie
unter Beanspruchung frei und unabhängig sind und sich bis zum Bruch linear-elastisch verhalten.
In Abhängigkeit von der Temperatur der Enden des Faserbündels werden zwei Verfahren vorgeschlagen:
a) Verfahren mit erhitzten Probenenden;
ANMERKUNG 1 Die Anwendung des Verfahrens mit erhitzten Probenenden ist durch Keramikklebstoffe mit hinreichender
Scherfestigkeit bei der Prüftemperatur eingeschränkt. Derzeitige Erfahrungen mit diesem Verfahren beschränken
sich wegen der maximalen Anwendungstemperatur von Keramikklebstoffen auf eine Temperatur von
1 300 °C.
b) Verfahren mit kalten Probenenden.
ANMERKUNG 2 Das Verfahren mit kalten Probenenden ist bedingt durch die von den Öfen gesetzten Grenzen
auf Temperaturen von 1 700 °C in Luft und 2 000 °C in inerter Atmosphäre begrenzt.
Beide Verfahren ermöglichen die Bestimmung der Verteilung von Zugdehnung und Zugfestigkeit bis zum
Bruch.
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 à la rupture des filaments dans un fil à haute température
La présente Norme européenne spécifie les conditions, l'appareillage et le mode opératoire relatifs à la
détermination de la distribution de la résistance en traction et de la déformation de traction à la rupture des
filaments céramiques dans des fils multi-filaments à haute température par essai à l'air, sous vide ou dans
une atmosphère inerte contrôlée.
La présente partie de l'EN 1007 s'applique aux fils constitués de filaments continus de céramique qui sont
supposés se comporter librement et indépendamment les uns des autres lorsqu'ils sont soumis à une charge
et de façon élastique linéaire jusqu'à la rupture.
Deux méthodes sont proposées en fonction de la température des extrémités du fil :
a) méthode avec mors chauds ;
NOTE 1 L'application de la méthode avec mors chauds est limitée par les colles céramiques présentant des
résistances au cisaillement suffisantes à la température d'essai. L'expérience actuelle acquise avec cette technique se
limite à 1 300 °C du fait de la température d'application maximale des colles céramiques.
b) méthode avec mors froids.
NOTE 2 La méthode avec mors froids est limitée à 1 700 °C dans l'air et à 2 000 °C en atmosphère inerte du fait
des limites des fours.
Les deux méthodes permettent d'obtenir une vitesse de rupture dans le cadre de la détermination de la
distribution de la déformation de traction et de la résistance en traction
Sodobna tehnična keramika - Keramični kompoziti - Preskusne metode za ojačitve - 7. del: Ugotavljanje porazdelitve natezne trdnosti in deformacij/obremenitev vlaken v svežnjih pri visoki temperaturi
Ta evropski standard določa pogoje, aparat in postopek za ugotavljanje porazdelitve natezne trdnosti in deformacij/obremenitve vlaken v svežnjih pri visoki temperaturi v zraku, vakuumu ali nadzorovani inertni atmosferi. Ta del EN 1007 velja za svežnje neprekinjenih keramičnih vlaken, za katere se predpostavlja, da pod obremenitvijo delujejo prosto in neodvisno ter so do deformacije linearno elastične.
General Information
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Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.MREUHPHQLWHYHochleistungskeramik - Keramische Verbundwerkstoffe - Verfahren zur Prüfung der Faserverstärkungen - Teil 7: Bestimmung der Verteilung von Zugfestigkeit und Zugdehnung von Fasern im Faserbündel bei hoher TemperaturCéramiques 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 à la rupture des filaments dans un fil à haute températureAdvanced 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 temperature81.060.30Sodobna keramikaAdvanced ceramicsICS:Ta slovenski standard je istoveten z:EN 1007-7:2010SIST EN 1007-7:2010en01-oktober-2010SIST EN 1007-7:2010SLOVENSKI
STANDARDSIST-TS CEN/TS 1007-7:20071DGRPHãþD
SIST EN 1007-7:2010
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 1007-7
July 2010 ICS 81.060.30 Supersedes CEN/TS 1007-7:2006English 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 composites - Méthodes d'essai pour renforts - Partie 7: Détermination de la distribution de la résistance en traction et de la déformation de traction à la rupture des filaments dans un fil à haute température
Hochleistungskeramik - Keramische Verbundwerkstoffe - Verfahren zur Prüfung der Faserverstärkungen - Teil 7: Bestimmung der Verteilung von Zugfestigkeit und Zugdehnung von Fasern im Faserbündel bei hoher Temperatur This European Standard was approved by CEN on 4 June 2010.
CEN members are bound to comply with the CEN/CENELEC 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 CEN Management Centre or to any 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 CEN Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, 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 © 2010 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 1007-7:2010: ESIST EN 1007-7:2010
EN 1007-7:2010 (E) 2 Contents Page Foreword .31Scope .42Normative references .43Terms and definitions .54Symbols and abbreviations .75Principle .76Significance and use .87Apparatus .87.1Test machine .87.2Load train .87.3Adhesive .87.4Test chamber .97.5Set-up for heating .97.6Temperature measurement .97.7Data recording system .98Test procedure .98.1Test specimens .98.2Test specimen preparation . 108.3Number of test specimens . 128.4Test Procedure . 138.5Calculation of results . 17Annex A (informative)
Derivation of the Young’s modulus of the hot part of the tow . 25Bibliography . 26 SIST EN 1007-7:2010
EN 1007-7:2010 (E) 3 Foreword This document (EN 1007-7:2010) has been prepared by Technical Committee CEN/TC 184 “Advanced technical ceramics”, the secretariat of which is held by BSI. 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 January 2011, and conflicting national standards shall be withdrawn at the latest by January 2011. 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. This document supersedes CEN/TS 1007-7:2006. 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. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, 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.
SIST EN 1007-7:2010
EN 1007-7:2010 (E) 4 1 Scope This European standard 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 part of EN 1007 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 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 1007-2, Advanced technical ceramics — Ceramic composites — Methods of test for reinforcement — Part 2: Determination of linear density CEN/TR 13233:2007, Advanced technical ceramics — Notations and symbols 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 7500-1:2004, 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) ISO 10119, Carbon fibre — Determination of density SIST EN 1007-7:2010
EN 1007-7:2010 (E) 5 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 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 L0 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 Lf. initial distance between the gripped ends of the tow 3.2.3 uniformly heated length Lh length of the heated zone within which the temperature variation is within 20 K of the test temperature 3.2.4 cold zone length Lc length of the tow, which is not uniformly heated 3.3 initial cross sectional area A0 sum of the cross sectional areas of all the filaments in the tow 3.4 tow elongation ûL increase of the gauge length between the two reference points on the tow 3.5 tow strain 0 ratio of the tow elongation ûL to the gauge length Lo 3.6 tow maximum tensile force Ftow highest recorded tensile force on the test specimen when tested to failure SIST EN 1007-7:2010
EN 1007-7:2010 (E) 6 3.7 tow strength 1tow ratio of the tow maximum tensile force to the cross sectional area of all unbroken filaments at maximum tensile force, Ftow 3.8 force at step j Fj force applied on the test specimen at step j 3.9 filament strain 0j strain at step j in the non-linear parts of the force-displacement curve 3.10 filament strength 1j 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 rε 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 rε arithmetic mean of the average filament rupture strains 3.13 average filament strength rσ 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 rσ arithmetic mean of the average filament strengths 3.15 Compliances 3.15.1 initial total compliance Ct inverse slope of the linear part of the force-displacement curve SIST EN 1007-7:2010
EN 1007-7:2010 (E) 7
3.15.2 instantaneous total compliance Ct,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 Cl 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 Cc ratio of the increase in test specimen length in the cold zone length Lc to the corresponding force during the tensile test 3.15.5 hot zone compliance Ch ratio of the increase in test specimen length in the uniformly heated length Lh to the corresponding force during the tensile test 4 Symbols and abbreviations Ctow
is the instantaneous total compliance of the tow at maximum tensile force. Eh
is the elastic modulus (Young’s modulus) of the uniformly heated part of the tow. Ec
is the elastic modulus (Young’s modulus) of the cold part of the tow. 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. SIST EN 1007-7:2010
EN 1007-7:2010 (E) 8 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 part of EN 1007 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 7500-1:2004. 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). SIST EN 1007-7:2010
EN 1007-7:2010 (E) 9 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 60584-1 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 L0 is equal to the test specimen length Lf. Test specimens with a gauge length of 100 mm shall be used to establish force-displacement curves. To determine the load train compliance Cl additional test specimens with gauge lengths of 50 mm and 150 mm shall be used. The gauge length shall be measured with an accuracy of ± 1 mm.
SIST EN 1007-7:2010
EN 1007-7:2010 (E) 10 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 Lf = Lc
+ Lh and the length of the hot part defines the gauge length, i.e. gradient zones 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. SIST EN 1007-7:2010
EN 1007-7:2010 (E) 11 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 SIST EN 1007-7:2010
EN 1007-7:2010 (E) 12 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 Lf. For this purpose, additional transparent 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 Lf 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 Cl. SIST EN 1007-7:2010
EN 1007-7:2010 (E) 13 8.4 Test Procedure 8.4.1 Determination of the temperature profile 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. Cold end method 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). SIST EN 1007-7:2010
EN 1007-7:2010 (E) 14
Key a Coil b Susceptor c Specimen d Grip Figure 3 — Schematic drawing of a cold end method device 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, lsusceptor = 20 mm. The gauge length, defined as the part of the tow Lh, where the axial variation of the temperature is less than 20 K, is to be extracted separately for each susceptor length from the appropriate temperature profile. The offset, ûToffset between the control temperature of the susceptor and the maximum temperature measured along the centre axis of the susceptor depends on the thermal conductivity of the specimen. Therefore, ûToffset during an actual test with a ceramic tow tends to be smaller than what is measured by a metallic thermocouple. SIST EN 1007-7:2010
EN 1007-7:2010 (E) 15
Figure 4 — Example of a temperature profile measured along the susceptor axis in a cold end method device 8.4.2 Test set-up: other considerations 8.4.2.1 Determination of the initial cross sectional area To determine 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). 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) A strain rate between 10-4 s-1 and 10-5 s-1 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 at lower crosshead displacement rates shall be performed until this is the case. Calculate the strain rate from the SIST EN 1007-7:2010
EN 1007-7:2010 (E) 16 displacement rate and check whether it falls into the required range. If not, decrease the crosshead displacement rate until this is the case. Use this crosshead displacement rate in all subsequent tests, irrespective of the gauge length of the specimen, even if failure does not occur in a controlled manner. 8.4.3.4 Setting of controlled environment When testing in an inert environment, air and water vapour shall be removed before introducing the inert atmosphere. This can be done by establishing a vacuum (below 10 Pa) in the enclosure according to 7.4.3, and subsequently introducing the inert gas, or by circulating the inert gas (flushing). While setting the controlled atmosphere, care shall be taken not to introduce tensile forces on the test specimen. NOTE 1 In view of the extreme oxidation sensitivity of some filament materials, conventional flushing of the test chamber may not be sufficient to reduce the oxygen level to an acceptable limit. NOTE 2 Forces are introduced on the test specimen when an excessive pressure of the inert gas is applied, or a vacuum is established and the machine is operated und
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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.MREUHPHQLWHYHochleistungskeramik - Keramische Verbundwerkstoffe. Verfahren zur Prüfung von Verstärkungen - Teil 7: Bestimmung der Verteilung von Zugfestigkeit und Zugdehnung von Fasern im Faserbündel bei hoher TemperaturCéramiques 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 à la rupture des filaments dans un fil à haute températureAdvanced 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 temperature81.060.30Sodobna keramikaAdvanced ceramicsICS:Ta slovenski standard je istoveten z:FprEN 1007-7kSIST FprEN 1007-7:2010en,fr01-februar-2010kSIST FprEN 1007-7:2010SLOVENSKI
STANDARD
kSIST FprEN 1007-7:2010
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
FINAL DRAFT
FprEN 1007-7
December 2009 ICS 81.060.30 Will supersede CEN/TS 1007-7:2006English 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 composites - Méthodes d'essai pour renforts - Partie 7: Détermination de la distribution de la résistance en traction et de la déformation de traction à la rupture des filaments dans un fil à haute température
Hochleistungskeramik - Keramische Verbundwerkstoffe. Verfahren zur Prüfung von Verstärkungen - Teil 7: Bestimmung der Verteilung von Zugfestigkeit und Zugdehnung von Fasern im Faserbündel bei hoher Temperatur This draft European Standard is submitted to CEN members for unique acceptance procedure. It has been drawn up by the Technical Committee CEN/TC 184.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
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Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and shall not be referred to as a European Standard.
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FprEN 1007-7:2009 (E) 2 Contents Page Foreword .31Scope .42Normative references .43Terms and definitions .54Symbols and abbreviations .75Principle .76Significance and use .87Apparatus .87.1Test machine .87.2Load train .87.3Adhesive .87.4Test chamber .97.5Set-up for heating .97.6Temperature measurement .97.7Data recording system .98Test procedure .98.1Test specimens .98.2Test specimen preparation . 108.3Number of test specimens . 128.4Test Procedure . 138.5Calculation of results . 17Annex A (informative)
Derivation of the Young’s modulus of the hot part of the tow . 25Bibliography . 26 kSIST FprEN 1007-7:2010
FprEN 1007-7:2009 (E) 3 Foreword This document (FprEN 1007-7:2009) has been prepared by Technical Committee CEN/TC 184 “Advanced technical ceramics”, the secretariat of which is held by BSI. This document is currently submitted to the Unique Acceptance Procedure. This document will supersede CEN/TS 1007-7:2006. 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.
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FprEN 1007-7:2009 (E) 4 1 Scope This European standard 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 part of EN 1007 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 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, Advanced technical ceramics — Mechanical properties of monolithic ceramics at room temperature — Part 5: 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 7500-1:2004, 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) CEN/TR 13233:2007, Advanced technical ceramics — Notations and symbols ISO 10119, Carbon fibre — Determination of density kSIST FprEN 1007-7:2010
FprEN 1007-7:2009 (E) 5 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 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 L0 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 Lf. initial distance between the gripped ends of the tow 3.2.3 uniformly heated length Lh length of the heated zone within which the temperature variation is within 20 K of the test temperature 3.2.4 cold zone length Lc length of the tow, which is not uniformly heated 3.3 initial cross sectional area A0 sum of the cross sectional areas of all the filaments in the tow 3.4 tow elongation ûL increase of the gauge length between the two reference points on the tow 3.5 tow strain 0 ratio of the tow elongation ûL to the gauge length Lo 3.6 tow maximum tensile force Ftow highest recorded tensile force on the test specimen when tested to failure kSIST FprEN 1007-7:2010
FprEN 1007-7:2009 (E) 6 3.7 tow strength 1tow ratio of the tow maximum tensile force to the cross sectional area of all unbroken filaments at maximum tensile force, Ftow 3.8 force at step j Fj force applied on the test specimen at step j 3.9 filament strain 0j strain at step j in the non-linear parts of the force-displacement curve 3.10 filament strength 1j 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 rε 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 rε arithmetic mean of the average filament rupture strains 3.13 average filament strength rσ 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 rσ arithmetic mean of the average filament strengths 3.15 Compliances 3.15.1 initial total compliance Ct inverse
slope of the linear part of the force-displacement curve kSIST FprEN 1007-7:2010
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3.15.2 instantaneous total compliance Ct,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 Cl 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 Cc ratio of the increase in test specimen length in the cold zone length Lc to the corresponding force during the tensile test 3.15.5 hot zone compliance Ch ratio of the increase in test specimen length in the uniformly heated length Lh to the corresponding force during the tensile test 4 Symbols and abbreviations Ctow
is the instantaneous total compliance of the tow at maximum tensile force. Eh
is the elastic modulus (Young’s modulus) of the uniformly heated part of the tow. Ec
is the elastic modulus (Young’s modulus) of the cold part of the tow. 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. kSIST FprEN 1007-7:2010
FprEN 1007-7:2009 (E) 8 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 part of EN 1007 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 7500-1:2004. 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). kSIST FprEN 1007-7:2010
FprEN 1007-7:2009 (E) 9 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 60584-1 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 L0 is equal to the test specimen length Lf. Test specimens with a gauge length of 100 mm shall be used to establish force-displacement curves. To determine the load train compliance Cl additional test specimens with gauge lengths of 50 mm and 150 mm shall be used. The gauge length shall be measured with an accuracy of ± 1 mm.
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FprEN 1007-7:2009 (E) 10 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 Lf = Lc
+ Lh and the length of the hot part defines the gauge length, i.e. gradient zones 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. kSIST FprEN 1007-7:2010
FprEN 1007-7:2009 (E) 11 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 kSIST FprEN 1007-7:2010
FprEN 1007-7:2009 (E) 12 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 Lf. For this purpose, additional transparent 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 Lf 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 Cl. kSIST FprEN 1007-7:2010
FprEN 1007-7:2009 (E) 13 8.4 Test Procedure 8.4.1 Determination of the temperature profile 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. Cold end method 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). kSIST FprEN 1007-7:2010
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Key a Coil b Susceptor c Specimen d Grip Figure 3 — Schematic drawing of a cold end method device 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, lsusceptor = 20 mm. The gauge length, defined as the part of the tow Lh, where the axial variation of the temperature is less than 20 K, is to be extracted separately for each susceptor length from the appropriate temperature profile. The offset, ûToffset between the control temperature of the susceptor and the maximum temperature measured along the centre axis of the susceptor depends on the thermal conductivity of the specimen. Therefore, ûToffset during an actual test with a ceramic tow tends to be smaller than what is measured by a metallic thermocouple. kSIST FprEN 1007-7:2010
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Figure 4 — Example of a temperature profile measured along the susceptor axis in a cold end method device 8.4.2 Test set-up: other considerations 8.4.2.1 Determination of the initial cross sectional area To determine 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). 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) A strain rate between 10-4 s-1 and 10-5 s-1 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 at lower crosshead displacement rates shall be performed until this is the case. Calculate the strain rate from the kSIST FprEN 1007-7:2010
FprEN 1007-7:2009 (E) 16 displacement rate and check whether it falls into the required range. If not, decrease the crosshead displacement rate until this is the case. Use this crosshead displacement rate in all subsequent tests, irrespective of the gauge length of the specimen, even if failure does not occur in a controlled manner. 8.4.3.4 Setting of controlled environment When testing in an inert environment, air and water vapour shall be removed before introducing the inert atmosphere. This can be done by establishing a vacuum (below 10 Pa) in the enclosure according to 7.4.3, and subsequently introducing the inert gas, or by circulating the inert gas (flushing). While setting the controlled atmosphere, care shall be taken not to introduce tensile forces on the test specimen. NOTE 1 In view of the extreme oxidation sensitivity of some filament materials, conventional flushing of the test chamber may not be sufficient to reduce the oxygen level to an acceptable limit. NOTE 2 Forces are introduced on the test specimen when an excessive pressure of the inert gas is applied, or a vacuum is established and the machine is operated under load control (zero load) with the load cell mounted outside the test chamber, except in the case where automatic load-pressure compensation is available for the equipment. This can be overcome by using displacement control (zero displacement) during the introduction of the controlled atmosphere. Alternatively, the load cell can be mounted inside the chamber so that it is exposed to the same environment as the test specimen. 8.4.3.5 Heating of the t
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