CEN/TC 184/WG 3 - Monolithic ceramics

This European Standard describes requirements and methods for proof testing of advanced technical ceramic components. It provides general guidance concerning the design of the test and the methodology for the selection of loading conditions.

This European Standard describes a method for undertaking ultimate strength tests on slotted rings (C-rings) in order to determine the strength of ring or tube-shaped components in the manufactured geometry.

This Technical Specification describes requirements and methods for undertaking tests to determine the resistance of the edges of brittle ceramic materials to be damaged by chipping or flaking. It is limited to homogeneous monolithic ceramics with flat surfaces and straight sharp or chamfered edges.

This Part of EN 843 contains guidelines to be adopted when evaluating the appearance of the fracture surface of an advanced technical ceramic. The purpose in undertaking this procedure can be various, for example, for material development or quality assessment, to identify normal or abnormal causes of failure, or as a design aid.
NOTE   Not all advanced technical ceramics are amenable to fractography. In particular, coarse-grained ceramics can show such rough surfaces that identifying the fracture origin may be impossible. Similarly, porous materials, especially those of a granular nature, tend not to fracture in a continuous manner, making analysis difficult.

This European standard gives guidance on selection of test-pieces for the evaluation of properties. Important factors requiring attention in the preparation of test samples from large components or blocks of material are also described.

This Part of EN 820 describes a procedure for undertaking flexural creep tests at elevated temperatures on advanced technical ceramics, mainly for the purposes of comparison of deformation behaviour of materials under stressed conditions and under any appropriate atmospheric condition.
NOTE   This European Standard does not provide a method of acquiring engineering performance data since the stress distribution under flexural loading is indeterminate.

This part of EN 820 describes methods for determining the elastic moduli, specifically Young's modulus, shear modulus and Poisson's ratio, of advanced monolithic technical ceramics at temperatures above room temperature. The standard prescribes three alternative methods for determining some or all of these three parameters:
A   the determination of Young's modulus by static flexure of a thin beam in three- or four-point bending.
B   the determination of Young's modulus by forced longitudinal resonance, or Young's modulus, shear modulus and Poisson's ratio by forced flexural and torsional resonance, of a thin beam.
C   the determination of Young's modulus from the fundamental natural frequency of a struck bar (impulse excitation method).
This part of EN 820 extends the above-defined room-temperature methods described in EN 843-2 to elevated temperatures. All the test methods assume the use of homogeneous test pieces of linear elastic materials. The test assumes that the test piece has isotropic elastic properties. At high porosity levels all of the methods can become inappropriate. The maximum grain size (see EN 623-3), excluding deliberately added whiskers, should be less than 10 % of the minimum dimension of the test piece.
NOTE 1   Method C in EN 843-2 based on ultrasonic time of flight measurement has not been incorporated into this part of EN 820. Although the method is feasible to apply, it is specialised, and outside the capabilities of most laboratories. There are also severe restrictions on test piece geometries and methods of achieving pulse transmission. For these reasons this method has not been included in EN 820-5.
NOTE 2   The upper temperature limit for this test depends on the properties of the test pieces, and can be limited by softening within the timescale of the test. In addition, for method A there can be limits defined by the choice of test jig construction materials.

This part of EN 843 specifies methods for determining the elastic moduli, specifically Young’s modulus, shear modulus and Poisson’s ratio, of advanced monolithic technical ceramics at room temperature. This European Standard prescribes four alternative methods for determining some or all of these three parameters:
A   The determination of Young’s modulus by static flexure of a thin beam in three- or four-point flexure.
B   The determination of Young’s modulus by forced longitudinal resonance, or Young’s modulus, shear modulus and Poisson’s ratio by forced flexural and torsional resonance, of a thin beam.
C    The determination of Young’s modulus, shear modulus and Poisson’s ratio from the time-of-flight of an ultrasonic pulse.
D   The determination of Young’s modulus from the fundamental natural frequency of a struck bar (impulse excitation method).
All the test methods assume the use of homogeneous test pieces of linear elastic materials.
NOTE 1   Not all ceramic materials are equally and linearly elastic in tension and compression, such as some porous materials and some piezoelectric materials.
With the exception of Method C, the test assumes that the test piece has isotropic elastic properties. Method C may be used to determine the degree of anisotropy by testing in different orientations.
NOTE 2   An ultrasonic method for dealing with anisotropic materials (ceramic matrix composites) can be found in
ENV 14186 (see Bibliography). An alternative to Method D for isotropic materials using disc test pieces is given in
Annex A.
NOTE 3   At high porosity levels all of the methods except Method C can become inappropriate. The methods are only suitable for a maximum grain size (see EN 623-3), excluding deliberately added whiskers, of less than 10 % of the minimum dimension of the test piece.
NOTE 4   The different methods given in this European Standard can produce slightly different results on the same material owing to differences between quasi-isothermal quasi-static an

This part of EN 623 specifies qualitative methods for determination of the presence of defects in advanced technical ceramics by dye penetration tests. The results are reported as visual observations of dye penetration.
Three methods are described:
Method A:  A fuchsine dye test which is suitable for white or pale-coloured ceramic products, performed using an evacuation test.
Method B:  A fluorescent dye test which is suitable particularly for those products where the purple fuchsine has insufficient visual contrast with the ceramic material, performed using a proprietary test kit.
Method C:  A fuchsine dye test which is performed by simple immersion in or spraying with a dye solution, suitable for routine testing for major defects.

ISO 18756:2003 describes a test method that covers the determination of fracture toughness of monolithic ceramic materials at room temperature by the surface crack in flexure (SCF) method.
This International Standard is intended for use with monolithic ceramics and whisker- or particulate-reinforced ceramics that are regarded as macroscopically homogeneous. It does not include continuous-fiber reinforced ceramic composites.
The test method is applicable to materials with either flat or rising crack growth resistance curves.

ISO 15732:2003 describes a test method for the determination of fracture toughness of monolithic ceramic materials at room temperature by the Single-Edge-Precracked-Beam (SEPB) method.
This International Standard is intended for use with monolithic ceramics and whisker- or particulate-reinforced ceramics which are regarded as macroscopically homogeneous. It does not include continuous-fiber-reinforced ceramic composites.
ISO 15732:2003 is for material development, material comparison, quality assurance, characterization, reliability and design data generation.
Fracture toughness values determined with other test methods cannot be interchanged with KIpb as defined in this International Standard, and may not be interchangeable with each other.

This European Standard specifies a method for the determination of subcritical crack growth parameters of advanced monolithic technical ceramics in the temperature range 15 °C to 30 °C by measuring the dependence of mean fracture strength on the rate of loading. The method is based on strength test procedures described in EN 843-1. This European Standard is not applicable to test pieces with artificially introduced flaws or cracks.

This part of EN 623 concerns the use of conventional stylus type instruments for the measurement of surface texture of advanced monolithic technical ceramics, sets the test machine measuring parameters, and recommends the adoption of certain precautions and conditions of measurement.
NOTE   Non-contact optical methods of surface texture measurement employ a different concept using a narrow laser beam. The interaction of the beam with the surface is influenced by the angle of the surface to the beam and the reflectivity/translucence of the surface. The reflected beam is detected in a number of ways based on spot focus or beam deflection and converted into a height profile. Results from such a test are not directly equivalent to those obtained by the stylus method.

This Part of EN 820 specifies the principles of thermal shock testing, and provides a general method for conducting thermal shock tests by quenching into water for both test pieces and components by quenching into water.
NOTE   This document does not cover thermal stress developed as a result of steady inhomogeneous temperature within a ceramic body or of thermal expansion mismatch between joined bodies.

1.1   This part of prCEN/TS 14425 provides information on the comparative value, and guidance on the selection, of test methods for determining the apparent fracture toughness of monolithic advanced technical ceramics. For the purposes of this standard, the term monolithic includes particle, platelet and whisker reinforced advanced technical ceramics which can be regarded as macroscopically homogeneous. It does not include long-fibre reinforced ceramics.
1.2   Reference is made in this part of prCEN/TS 14425 to specific test methods described in other parts of this Technical Specification.

This part of EN 821 describes a method for the determination of thermal diffusivity of advanced monolithic technical ceramics, to an accuracy of approximately +/- 5%. It is suitable for the measurement of thermal diffusivity values in the range 0.1 mm2/s to 1000 mm2/s at temperatures greater than -180°C.

This European Standard provides a test method for fracture toughness determination based on the chevron-notch method. For the purposes of this European Standard, the term monolithic includes particle and whisker reinforced advanced technical ceramics which can be regarded as macroscopically homogeneous. It does not include long-fibre reinforced ceramics.

This part of EN 12923 specifies guidelines to be employed when undertaking corrosion tests on advanced technical ceramics. The mechanisms of chemical attack on advanced ceramics are widely varied and depend on the chemical and phase composition and the phase morphology of the material, as well as the corrosive conditions imposed. For any particular engineering application it is usually necessary to model expected conditions of use in order to obtain quantitative data on the ability to withstand the proposed end-use conditions.
This European Standard is not restricted to specific material types, nor does it prescribe particular test conditions or a test duration. The actual testing requirements might be very specific, for example, in order to investigate the suitability of a range of materials for a given application in which certain specified conditions occur. This European Standard provides recommended methods for undertaking the assessment of the effect of corrosion and provides guidance on practical issues related to undertaking the tests.

This part of EN 843 specifies a method for statistical analysis of ceramic strength data in terms of a two-parameter Weibull distribution using a maximum likelihood estimation technique. It assumes that the data set has been obtained from a series of tests under nominally identical conditions.
NOTE 1   In principle, Weibull analysis is considered to be strictly valid for the case of linear elastic fracture behaviour to the point of failure, i.e. for a perfectly brittle material, and under conditions in which strength limiting flaws do not interact and in which there is only a single strength-limiting flaw population.
If subcritical crack growth or creep deformation preceding fracture occurs, Weibull analysis can still be applied if the results fit a Weibull distribution, but numerical parameters may change depending on the magnitude of these effects. Since it is impossible to be certain of the degree to which subcritical crack growth or creep deformation has occurred, this European Standard permits the analysis of the general situation where crack growth or creep may have occurred, provided that it is recognized that the parameters derived from the analysis may not be the same as those derived from data with no subcritical crack growth or creep.
NOTE 2   This European Standard employs the same calculation procedures as method A of ISO 20501:2003, but does not provide a method for dealing with censored data (method B of ISO 20501).

This part of EN 623 describes methods for determination of the bulk desnsity, apparent porosity of advanced technical ceramics.
Two methods are described and are designated as Methods 1 and 2, as follows :
Method 1: Determination of bulk density, apparent solid density and apparent porosity by the evacuation method.
Method 2: Determination of bulk density only, by measurement of dimensions and mass.

This part of EN 821 desribes the method for the determination of the linear thermal expansion characteristics of advanced monolithic technical ceramics up to a maximum temperature of 1500°C and to a specified level of accuracy A or B as defined in table 1. The method describes general principles of construction, calibration and operation of suitable apparatus. Specific details, including test piece dimensions, depend on the design of the apparatus. Methods of calibration are given in annexes A and B. Thermal expansion reference data are given in annex C.

This Part of ENV 12923 describes a simple oxidation test for advanced technical ceramics. The test is designed to give an assessment of the mass and dimensional changes of test pieces following oxidation at high temperature in an oxidizing atmosphere, and to assess whether oxidation has a significant effect on the subsequent strength, either at room temperature or at elevated temperatures.
NOTE 1 This test method does not allow definition of other mechanical performance changes resulting from high-temperature exposure, such as changes in susceptibility to subcritical crack growth, creep behaviour, migration of secondary constituents, etc.
NOTE 2 This test method does not cover the additional effects of other corrodents in the ambient atmosphere, such as salt vapours, reducing or corrosive gases, and other contaminants. This method also does not cover tests at pressures other than ambient atmospheric pressure.
NOTE 3 An interlaboratory evaluation of the procedure given in this standard is summarised in annex A.

This part of EN 623 specifies a manual method of making measurements for the determination of volume fraction of
major phases in advanced technical ceramics using micrographs of polished and etched sections, overlaying a square
grid of lines, and counting the number of intersections lying over each phase.
NOTE 1 This method assumes that the true phase volume fractions are equivalent to area fractions on a randomly cut crosssection
according to stereological principles.
NOTE 2 Guidelines for polishing and etching of advanced technical ceramics can be found in Annexes A and B.
The method applies to ceramics with one or more distinct secondary phases, such as found in Al2O3/ZrO2, Si/SiC,or
Al2O3/SiCw.
If the test material contains discrete pores, these can be treated as a secondary phase for the purpose of this method
provided that there is no evidence of grain pluck-out during polishing being confused with genuine pores.
NOTE 3 If the material contains more than about 20 % porosity there is a strong risk that the microstructure will be damaged
during the polishing process, and measurement of volume fraction of pores may become misleading.
Secondary phase volume fractions or porosity present at levels of less than 0,05 are subject to considerable error and
potential scatter in results. A larger number of micrographs than the minimum of three is normally needed to improve
the consistency and accuracy of the results.
NOTE 4 Many ceramics contain small amounts of secondary glassy phases. In order to make a reasonable estimate of
glassy phase content, the glass material between crystalline grains should be readily observable, and thus should be at least
0,5 μm in width. The method in this European Standard is not considered appropriate for narrow glassy films around grains.
This method assumes that the selected regions of a prepared cross-section are statistically representative of the whole
sampled section.

This part of CEN/TS 14425 describes a method for the determination of the fracture toughness of advanced technical ceramics. The procedure makes use of V-notched bars, which are loaded in 4-point bending until failure. It is applicable to ceramics with a grain size or major microstructural feature size larger than about 1 µm.

This Part of EN 623 describes manual methods of making measurements for the determination of mean linear intercept grain size of advanced technical ceramics using photomicrographs of polished and etched test pieces. This is not the true mean grain diameter, but a somewhat smaller parameter representing the average path length of a line drawn across a two-dimensional section. The relationship to true grain dimensions depends on grain shape and degree of microstructural anisotropy. This standard contains two methods, A and B.
Method A applies to single-phase ceramics, and to ceramics with a principal crystalline phase and a glassy grain-boundary phase of less than about 5% by volume for which intercept counting suffices. Method B applies to ceramics with more than about 5% by volume of pores or secondary phases, or ceramics with more than one major crystalline phase where individual intercept lengths are measured, which can optionally be used to create a size distribution. This latter method allows the pores or phases to be distinguished and the mean linear intercept size for each to be calculated separately.
NOTE A method of determining volume fraction(s) of secondary phase(s) is under development as ENV 623-5; this will provide a means of determining whether Method A or Method B should be applied in borderline cases.
Some users of this standard may wish to apply automatic or semiautomatic image analysis to micrographs or directly captured microstructural images This is permitted by this standard provided that the technique employed simulates the manual method (see clause 4 and 8.4).

This part of CEN/TS 14425 provides a test method for fracture toughness determination based on the chevron-notch method. For the purposes of this standard, the term monolithic includes particle and whisker reinforced advanced technical ceramics which can be regarded as macroscopically homogeneous. It does not included long-fibre reinforced ceramics.

This European Prestandard specifies a manual method of making measurements for the determination of volume fraction of major phases in advanced technical ceramics using micrographs of polished and etched sections, overlaying a square grid of lines, and counting the number of intersections lying over each phase.
NOTE 1   This method assumes that the true phase volume fractions are equivalent to area fractions on a randomly cut cross-section according to stereological principles.
NOTE 2   Guidelines for polishing and etching of advanced technical ceramics can be found in annexes A and B.
The method applies to ceramics with one or more distinct secondary phases, such as found in Al2O3/ZrO2, Si/SiC, or Al2O3/SiCw.
If the test material contains discrete pores, these can be treated as a secondary phase for the purpose of this method provided that there is no evidence of grain pluck-out during polishing being confused with genuine pores.
NOTE 3   If the material contains more than about 20% porosity there is a strong risk that the microstructure will be damaged during the polishing process, and measurement of volume fraction of pores may become misleading.
Secondary phase volume fractions or porosity present at levels of less than 0,05 are subject to considerable error and potential scatter in results. A larger number of micrographs than the minimum of three is normally needed to improve the consistency and accuracy of the results.
NOTE 4   Many ceramics contain small amounts of secondary glassy phases. In order to make a reasonable estimate of glassy phase content, the glass material between crystalline grains should be readily observable, and thus should be at least 0,5 µm in width. The method in this Prestandard is not considered appropriate for narrow glassy films around grains.

This Part of ENV 820 describes a procedure for undertaking flexural creep tests at elevated temperatures on advanced technical ceramics, mainly for the purposes of comparison of deformation behaviour of materials under stressed conditions and under any appropriate atmospheric condition.
NOTE This prestandard does not provide a method of acquiring engineering performance data since the stress distribution under flexural loading is indeterminate.

This part of ENV 12923 describes general procedures to be employed when undertaking corrosion tests on advanced technical ceramics. The mechanisms of chemical attack on advanced ceramics are widely varied, and depend on the chemical and phase composition and the phase morphology of the material, as well as the corrosive conditions imposed. For any particular engineering application it is usually necessary to model expected conditions of use in order to obtain quantitative data on ability to withstand the proposed end-use conditions.

This pre-standard describes a method for statistical analysis of ceramic strength data in terms of a two-parameter Weibull distribution using a maximum likelihood estimation technique. It assumes that the data set has been obtained from a series of tests under nominally identical conditions.

Migrated from Progress Sheet (TC Comment) (2000-07-10): Stage 41/51=ENV ++ Waiting for D version.

This part of EN 843 describes methods for determining the nominal flexural strength of advanced monolithic technical ceramic materials at ambient temperature. The available loading geometries are three- and four-point flexure,using rectangular section test-pieces of two prescribed geometries: 20 mm support span (A) and 40 mm support span (B). The test prescribes four categoriesof surface finish applied to the test-pieces.

This part of EN 623 describes qualitative methods for determination of the presence of defects in advanced monolithic technical ceramics by dye penetration tests. The results are reported as visual observations of dye penetration.

Migrated from Progress Sheet (TC Comment) (2000-07-10): Stage 41/51=ENV ++ Waiting for D version.

Migrated from Progress Sheet (TC Comment) (2000-07-10): Stage 41/51=ENV ++ Information on ENV: ++ REAL41=199212, REAL53=199212.

Migrated from Progress Sheet (TC Comment) (2000-07-10): 2-Year Enquiry ++ Realized dates for the ENV: REAL41 = 1992-09; REAL53 = 1992-09 (CC/970919)

This Technical Specification contains guidelines to be adopted when evaluating the appearance of the
fracture surface of an advanced technical ceramic. The purpose in undertaking this procedure can be
various, for example, for material development or quality assessment, to identify normal or abnormal
causes of failure, or as a design aid.
NOTE Not all advanced technical ceramics are amenable to fractography. In particular, coarse-grained ceramics
can show such rough surfaces that identifying the fracture origin may be impossible. Similarly, porous materials,
especially those of a granular nature, tend not to fracture in a continuous manner, making analysis difficult.

This part of ENV 820 describes methods for determining the elastic moduli, specifically Young's modulus, shear modulus and Poisson's ratio, of advanced monolithic technical ceramics at temperatures above room temperature. The Technical Specification prescribes three alternative methods for determining some or all of these three parameters:
A   The determination of Young's modulus by static flexure of a thin beam in three- or four-point bending.
B   The determination of Young's modulus by forced longitudinal resonance, or Young's modulus, shear modulus and Poisson's ratio by forced flexural and torsional resonance, of a thin beam.
C   The determination of Young's modulus from the fundamental natural frequency of a struck bar (impulse excitation method).
This Technical Specification extends the above-defined room-temperature methods described in ENV 843-2 to elevated temperatures. All the test methods assume the use of homogeneous test pieces of linear elastic materials. The test assumes that the test piece has isotropic elastic properties. At high porosity levels all of the methods can become inappropriate. The maximum grain size (see EN 623-3), excluding deliberately added whiskers, should be less than 10% of the minimum dimension of the test piece.

Migrated from Progress Sheet (TC Comment) (2000-07-10): Information on ENV: ++ REAL41=199203, REAL53=199203.