SIST EN 13234:2007
(Main)Advanced technical ceramics - Mechanical properties of ceramic composites at ambient temperature - Evaluation of the resistance to crack propagation by notch sensitivity testing
Advanced technical ceramics - Mechanical properties of ceramic composites at ambient temperature - Evaluation of the resistance to crack propagation by notch sensitivity testing
This European Standard describes a method for the classification of ceramic matrix composite (CMC) materials with respect to their sensitivity to crack propagation using tensile tests on notched specimens with different notch depths. Two classes of ceramic matrix composite materials can be distinguished: materials whose strength is sensitive to the presence of notches and materials whose strength is not affected. For sensitive materials, this European Standard defines a method for determining equivalent fracture toughness.
The parameter, Keq, is defined as the fracture toughness of a homogeneous material which presents the same sensitivity to crack propagation as the ceramic matrix composite material which is being considered. The definition of the Keq parameter offers the possibility to compare ceramic matrix composite materials with other materials with respect to sensitivity to crack propagation.
For notch insensitive materials, the concept of Keq does not apply.
This European Standard applies to all ceramic matrix composites with a continuous fibre reinforcement, unidirectional (1 D), bidirectional (2 D), and tridirectional (x D, where 2 < x ? 3), loaded along one principal axis of reinforcement.
Hochleistungskeramik - Mechanische Eigenschaften von keramischen Verbundwerkstoffen bei Umgebungstemperatur - Beurteilung der Rissausbreitungsbeständigkeit durch die Kerbempfindlichkeitsprüfung
Le présent document décrit une méthode pour la classification des matériaux composites a matrice céramique (CMC) selon leur sensibilité a la propagation de fissure en utilisant des essais de traction effectués sur des éprouvettes entaillées avec différentes profondeurs d'entailles. Deux classes de matériaux composites a matrices céramiques peuvent etre distinguées : les matériaux dont la résistance est sensible a la présence d'entailles et les matériaux dont la résistance n'est pas affectée. Pour les matériaux sensibles, la présente Norme européenne définit une méthode pour la détermination de la ténacité équivalente.
Le parametre, Keq, est défini comme étant la ténacité d'un matériau homogene qui présente la meme sensibilité a la propagation de la fissure que le matériau composite a matrice céramique étudié. La définition du parametre Keq offre la possibilité de comparer des matériaux composites a matrice céramique avec d'autres matériaux quant a la sensibilité a la propagation de fissure.
Pour les matériaux insensibles a l'entaille, le concept de Keq ne s'applique pas.
La présente Norme européenne s'applique a tous les composites a matrices céramiques a renfort fibreux continu, unidirectionnels (1 D), bidirectionnels (2 D), et tridirectionnels (x D, avec 2 x 3), sollicités suivant un axe principal de renfort.
Céramiques techniques avancées - Propriétés mécaniques des céramiques composites a température ambiante - Evaluation de la résistance a la propagation de fissure par un essai de sensibilité a l'entaille
Sodobna tehnična keramika - Mehanske lastnosti keramičnih kompozitov pri temperaturi okolice - Ovrednotenje odpornosti proti širjenju razpoke s preskušanjem občutljivosti zareze
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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Advanced technical ceramics - Mechanical properties of ceramic composites at ambient temperature - Evaluation of the resistance to crack propagation by notch sensitivity testingCéramiques techniques avancées - Propriétés mécaniques des céramiques composites a température ambiante - Evaluation de la résistance a la propagation de fissure par un essai de sensibilité a l'entailleHochleistungskeramik - Mechanische Eigenschaften von keramischen Verbundwerkstoffen bei Umgebungstemperatur - Beurteilung der Rissausbreitungsbeständigkeit durch die KerbempfindlichkeitsprüfungTa slovenski standard je istoveten z:EN 13234:2006SIST EN 13234:2007en81.060.30Sodobna keramikaAdvanced ceramicsICS:SIST ENV 13234:20001DGRPHãþDSLOVENSKI
STANDARDSIST EN 13234:200701-januar-2007
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 13234October 2006ICS 81.060.30Supersedes ENV 13234:1998
English VersionAdvanced technical ceramics - Mechanical properties of ceramiccomposites at ambient temperature - Evaluation of theresistance to crack propagation by notch sensitivity testingCéramiques techniques avancées - Propriétés mécaniquesdes céramiques composites à température ambiante -Evaluation de la résistance à la propagation de fissure parun essai de sensibilité à l'entailleHochleistungskeramik - Mechanische Eigenschaften vonkeramischen Verbundwerkstoffen beiUmgebungstemperatur - Beurteilung derRissausbreitungsbeständigkeit durch dieKerbempfindlichkeitsprüfungThis European Standard was approved by CEN on 11 September 2006.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.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.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2006 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 13234:2006: E
EN 13234:2006 (E) 2 Contents
Page Foreword.3 1 Scope.4 2 Normative references.4 3 Principle.4 4 Significance and use.5 5 Terms, definitions and symbols.6 6 Apparatus.7 6.1 Test machine.7 6.2 Load train.7 6.3 Data recording system.7 6.4 Micrometers.8 6.5 Ligament size measuring device.8 7 Specimens.8 7.1 Un-notched test specimens.8 7.2 Notched test specimens.8 7.3 Notches.10 8 Test specimen preparation.10 8.1 Machining and preparation.10 8.2 Number of test specimens.10 9 Test procedure.10 9.1 Test on reference specimen.10 9.2 Test on notched specimen.10 10 Calculation of results.11 10.1 Test specimen origin.11 10.2 Tensile strength of un-notched specimen.11 10.3 Tensile strength of the notched specimen.12 10.4 Plotting of notch sensitivity diagram.12 10.5 Calculation of equivalent fracture toughness for the different classes of behaviour.13 11 Test report.13 Bibliography.15
EN 13234:2006 (E) 3 Foreword This document (EN 13234:2006) 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 April 2007, and conflicting national standards shall be withdrawn at the latest by April 2007. This document supersedes ENV 13234:1998. ENV 13234 was approved by CEN/TC 184 for development into a full European Standard. The principal changes to the ENV are in the normative references, as follows: - in 6.1, reference to EN 10002-2 has been replaced by reference to EN ISO 7500-1; - in 6.2.1, reference to WI 136 has been removed. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: 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 13234:2006 (E) 4 1 Scope This European Standard describes a method for the classification of ceramic matrix composite (CMC) materials with respect to their sensitivity to crack propagation using tensile tests on notched specimens with different notch depths. Two classes of ceramic matrix composite materials can be distinguished: materials whose strength is sensitive to the presence of notches and materials whose strength is not affected. For sensitive materials, this European Standard defines a method for determining equivalent fracture toughness. The parameter, Keq, is defined as the fracture toughness of a homogeneous material which presents the same sensitivity to crack propagation as the ceramic matrix composite material which is being considered. The definition of the Keq parameter offers the possibility to compare ceramic matrix composite materials with other materials with respect to sensitivity to crack propagation. For notch insensitive materials, the concept of Keq does not apply. This European Standard applies to all ceramic matrix composites with a continuous fibre reinforcement, unidirectional (1 D), bidirectional (2 D), and tridirectional (x D, where 2 < x ≤ 3), loaded along one principal axis of reinforcement. 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 658-1:1998, Advanced technical ceramics — Mechanical properties of ceramic composites at room temperature — Part 1: Determination of tensile properties 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) ISO 3611, Micrometer callipers for external measurement 3 Principle Tensile tests are carried out on double edge notched test specimens with notches of different depths. The results of these tests are compared with the results of tensile tests on specimens without notches. The cross sectional dimensions of the notched specimens between the notches are equal to those of the un-notched specimens. The strength values observed on both types of specimens as a function of notch depth allow the determination of the range of notch size for which the tested composite is sensitive to the presence of notches.
EN 13234:2006 (E) 5 4 Significance and use The fracture toughness is a material property which characterises the initiation of fracture from a sharp crack (usually obtained by fatigue cracking under plane strain conditions). The fracture toughness of materials at the onset of crack extension from a pre-existing fatigue crack is characterised by the value of one of the following parameters: i) KΙc, a critical value of KΙ (the stress intensity factor of the elastic stress field in the vicinity of the crack front), at the point of instability of the crack extension; ii) GΙc, a critical value of GΙ (the strain-energy release rate with crack extension per unit area of newly created crack surface) at the point of instability of the crack extension; iii) JΙc, a critical value of JΙ (a line or surface integral used to characterise the local stress-strain field around the crack front) at the onset of stable crack extension. The J integral plays an important role in non-linear fracture mechanics. It applies to non-linear elastic bodies, whereas linear elastic fracture mechanics (KΙc and GΙc) consider linear elastic bodies. Several problems arise in determining and even in defining KΙc, GΙc and JΙc in fibre reinforced ceramic matrix composites, as a result of the following features: 1) CMC are generally highly heterogeneous, consisting of different constituents (fibres and matrix), and containing pores and cracks; 2) in some CMC a damage zone of multiple matrix cracks forms ahead of a notch prior to ultimate failure; 3) the associated deformations are non-linear. The load versus load line displacement curve from a fracture test on a notched specimen involves a non-linear domain induced by diffuse micro-cracking within the matrix at the notch tip. The damage zone is in the millimetre to centimetre scale (from one to several tow diameters). At maximum load, a macroscopic crack is created from the random failure of fibres within those tows located in the damage zone. Crack extension in CMC, hence, does not result from the mechanism of extension of a single macroscopic crack as observed in monolithic materials. Because of the presence of the damage zone and of heterogeneous microstructure, the stress distribution in the damage zone differs from the one induced ahead of the crack tip in linear elastic bodies. The KΙ parameter does not describe the stress field in the region ahead of the crack tip. A critical value KΙc cannot be defined. The main difficulty in the determination of the strain energy release rate GΙ, as well as the J integral, results from the presence of the micro-cracked zone at the notch tip (which is not small compared with the specimen dimensions) and the jagged surface of the macroscopic crack. As a consequence an increase in crack length can neither be easily defined nor measured. Tensile tests performed on specimens containing holes or notches have demonstrated that many CMC are relatively notch-insensitive over a range of notch sizes. The net-section stress at fracture is typically (80 to 100) % of the un-notched strength. Notch insensitivity result
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