1、Designation: C 1674 08Standard Test Method forFlexural Strength of Advanced Ceramics with EngineeredPorosity (Honeycomb Cellular Channels) at AmbientTemperatures1This standard is issued under the fixed designation C 1674; the number immediately following the designation indicates the year oforiginal
2、 adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the flexuralstrength (
3、modulus of rupture in bending) at ambient conditionsof advanced ceramic structures with 2-dimensional honeycombchannel architectures.1.2 The test method is focused on engineered ceramiccomponents with longitudinal hollow channels, commonlycalled “honeycomb” channels. (See Fig. 1.) The componentsgene
4、rally have 30 % or more porosity and the cross-sectionaldimensions of the honeycomb channels are on the order of 1millimeter or greater. Ceramics with these honeycomb struc-tures are used in a wide range of applications (catalyticconversion supports (1),2high temperature filters (2, 3),combustion bu
5、rner plates (4), energy absorption and damping(5), etc.). The honeycomb ceramics can be made in a range ofceramic compositionsalumina, cordierite, zirconia, spinel,mullite, silicon carbide, silicon nitride, graphite, and carbon.The components are produced in a variety of geometries(blocks, plates, c
6、ylinders, rods, rings).1.3 The test method describes two test specimen geometriesfor determining the flexural strength (modulus of rupture) for aporous honeycomb ceramic test specimen (see Fig. 2):1.3.1 Test Method AA4-point or 3-point bending test withuser-defined specimen geometries, and1.3.2 Test
7、 Method BA 4-point-14 point bending test witha defined rectangular specimen geometry (13 mm 3 25 mm 3 116 mm) and a 90 mm outer support span geometry suitablefor cordierite and silicon carbide honeycombs with small cellsizes.1.4 The test specimens are stressed to failure and thebreaking force value,
8、 specimen and cell dimensions, andloading geometry data are used to calculate a nominal beamstrength, a wall fracture strength, and a honeycomb structurestrength.1.5 Test results are used for material and structural devel-opment, product characterization, design data, quality control,and engineering
9、/production specifications.1.6 The test method is meant for ceramic materials that arelinear-elastic to failure in tension. The test method is notapplicable to polymer or metallic porous structures that fail inan elastomeric or an elastic-ductile manner.1.7 The test method is defined for ambient tes
10、ting tempera-tures. No directions are provided for testing at elevated orcryogenic temperatures.1.8 The values stated in SI units are to be regarded asstandard (IEEE/ASTM SI 10). English units are sparsely usedin this standard for product definitions and tool descriptions,per the cited references an
11、d common practice in the USautomotive industry.1.9 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regu
12、latory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3C 373 Test Method for Water Absorption, Bulk Density,Apparent Porosity, and Apparent Specific Gravity of FiredWhiteware ProductsC 1145 Terminology of Advanced CeramicsC 1161 Test Method for Flexural Strength of AdvancedCerami
13、cs at Ambient TemperatureC 1198 Test Method for Dynamic Youngs Modulus, ShearModulus, and Poissons Ratio for Advanced Ceramics bySonic ResonanceC 1239 Practice for Reporting Uniaxial Strength Data andEstimating Weibull Distribution Parameters for AdvancedCeramicsC 1259 Test Method for Dynamic Youngs
14、 Modulus, Shear1This test method is under the jurisdiction of ASTM Committee C28 onAdvanced Ceramics and is the direct responsibility of Subcommittee C28.04 onApplications.Current edition approved June 1, 2008. Published July 2008.2The boldface numbers in parentheses refer to the list of references
15、at the end ofthis standard.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100
16、 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Modulus, and Poissons Ratio for Advanced Ceramics byImpulse Excitation of VibrationC 1292 Test Method for Shear Strength of ContinuousFiber-Reinforced Advanced Ceramics at Ambient Tem-peraturesC 1341 Test Method for Fle
17、xural Properties of ContinuousFiber-Reinforced Advanced Ceramic CompositesC 1368 Test Method for Determination of Slow CrackGrowth Parameters of Advanced Ceramics by ConstantStress-Rate Flexural Testing at Ambient TemperatureC 1525 Test Method for Determination of Thermal ShockResistance for Advance
18、d Ceramics by Water QuenchingC 1576 Test Method for Determination of Slow CrackGrowth Parameters of Advanced Ceramics by ConstantStress Flexural Testing (Stress Rupture) at Ambient Tem-peratureD 2344/D 2344M Test Method for Short-Beam Strength ofPolymer Matrix Composite Materials and Their Laminates
19、E4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical Test-ingE 337 Test Method for Measuring Humidity with a Psy-chrometer (the Measurement of Wet- and Dry-Bulb Tem-peratures)IEEE/ASTM SI 10 Standard for Use of the InternationalSystem of Units (SI)
20、(The Modern Metric System)3. Terminology3.1 The definitions of terms relating to flexure testingappearing in Terminology E6apply to the terms used in thistest method. The definitions of terms relating to advancedceramics appearing in Terminology C 1145 apply to the termsused in this test method. Per
21、tinent definitions, as listed inTerminology C 1145, Test Method C 1161, and TerminologyE6are shown in the following section with the appropriatesource given in brackets. Additional terms used in conjunctionwith this test method are also defined.3.1.1 advanced ceramic, na highly engineered, high-perf
22、ormance, predominately nonmetallic, inorganic, ceramicmaterial having specific functional attributes. C 11453.1.2 breaking force, F, nthe force at which fractureoccurs in a test specimen. E63.1.2.1 DiscussionIn this test method, fracture consists ofbreakage of the test bar into two or more pieces or
23、 a loss of atleast 50 % of the maximum force carrying capacity.3.1.3 cell pitch, (p), L, nthe unit dimension/s for thecross-section of a cell in the honeycomb component. The cellpitch p is calculated by measuring the specimen dimension ofinterest, the cell count in that dimension, and a cell wallthi
24、ckness, where p =(dt)/n. (See Fig. 3.)3.1.3.1 DiscussionThe cell pitch can be measured forboth the height and width of the cell; those two measurementswill be equal for a square cell geometry and uniform cell wallthickness and will be unequal for a rectangular cell geometry.3.1.4 cell wall thickness
25、, (t), L, nthe nominal thicknessof the walls that form the cell channels of the honeycombstructure. (See Fig. 3.)3.1.5 channel porosity, nporosity in the porous ceramiccomponent that is defined by the large, open longitudinalhoneycomb channels. Channel porosity generally has cross-sectional dimensio
26、ns on the order of 1 millimeter or greater.FIG. 1 General Schematics of Typical Honeycomb Ceramic StructuresL = Outer Span Length (for Test Method A, L = User defined; for Test Method B, L =90mm)NOTE 14-Point-14 Loading for Test Methods A1 and B.NOTE 23-Point Loading for Test Method A2.FIG. 2 Flexur
27、e Loading ConfigurationsC16740823.1.6 complete gage section, nthe portion of the specimenbetween the two outer bearings in four-point flexure andthree-point flexure fixtures.3.1.6.1 DiscussionIn this standard, the complete 4-pointflexure gage section is twice the size of the inner gage section.Weibu
28、ll statistical analysis only includes portions of thespecimen volume or surface which experience tensile stresses.3.1.7 engineered porosity, nporosity in a component thatis deliberately produced and controlled for a specific functionand engineered performance. The porosity can be microporous(micron
29、and submicron pores in the body of the ceramic) ormacroporous (millimeter and larger) cells and channels in theceramic. The porosity commonly has physical properties (vol-ume fraction, size, shape, structure, architecture, dimensions,etc.) that are produced by a controlled manufacturing process.The
30、porosity in the component has a direct effect on theengineering properties and performance and often has to bemeasured for quality control and performance verification.3.1.8 four-point-14 point flexure, na configuration of flex-ural strength testing where a specimen is symmetrically loadedat two inn
31、er span locations that are situated one quarter of theoverall span inside the span of the outer two support bearings.(See Fig. 2.) C 11613.1.9 fractional open frontal area, (OFA), ND, na frac-tional ratio of the open frontal area of the honeycomb archi-tecture, calculated by dividing the total front
32、al area of the openchannels by the full frontal area of the full size specimen, as awhole.3.1.9.1 DiscussionThe fractional open frontal area of thefull size specimen can be calculated from the shape anddimensions of the cells and the wall thickness between cells.(See section 11.4 on Calculations.)3.
33、1.10 fully-articulating fixture, na flexure fixture de-signed to be used both with flat and parallel specimens andwith uneven or nonparallel specimens. The fixture allows fullindependent articulation, or pivoting, of all load and supportrollers about the specimen long axis to match the specimensurfa
34、ce. In addition, the upper or lower roller pairs are free topivot to distribute force evenly to the bearing cylinders oneither side. (See Annex A1 for schematics and discussion.)C 11613.1.11 honeycomb cell density, na characterization of thehoneycomb cell structure that lists the number of cells per
35、 unitarea and the nominal cell wall thickness. It is common practicein the automotive catalyst industry to use English units for thisterm, for example:100/17 density = 100 cells/in.2with a cell wall thickness of 0.017 in.200/12 density = 200 cells/in.2with a cell wall thickness of 0.012 in.3.1.12 ho
36、neycomb cellular architecture, nan engineeredcomponent architecture in which long cylindrical cells ofdefined geometric cross-section form a porous structure withopen channels in one dimension and a nominal closed-cellarchitecture in the remaining two dimensions. The crosssectional geometry of the h
37、oneycomb cells can have a varietyof shapessquare, hexagonal, triangular, circular, etc. (SeeFig. 1.)3.1.12.1 DiscussionThe cell walls in a honeycomb struc-ture may have controlled wall porosity levels, engineered forfiltering, separation effects, and mechanical strength.3.1.13 honeycomb structure st
38、rength, SHS, FL-2, nameasure of the maximum strength in bending of a specifiedhoneycomb test specimen, calculated by considering the com-plex moment of inertia of the test specimen with its channelpore structure and adjusting for the open frontal area of thecellular specimen. (See Section 11 and App
39、endix X1.)3.1.13.1 DiscussionThe honeycomb structure strengthgives a continuum strength that is more representative of thetrue continuum strength as compared to the nominal beamstrength SNB, particularly for specimens where the linear cellcount in the smallest cross sectional dimension is less than
40、15.b = specimen widthd = specimen thicknesst = cell wall thicknessp = cell pitchn = linear cell count (height)m = linear cell count (width)FIG. 3 Schematic of Honeycomb Structure with Square Cells Showing Geometric TermsC16740833.1.13.2 DiscussionThe honeycomb structure strengthmay be used to compar
41、e tests for specimens of different cellarchitectures and sizes and specimen dimensions. However, thecalculated honeycomb structure strength is not representativeof the failure stress in the outer fiber surface (the wall fracturestrength) of the test specimen.3.1.14 linear cell count, ND, nthe intege
42、r number ofcells along a given cross-sectional dimension of a test speci-men. For the specimen width, the linear cell count is defined asm. For the specimen thickness dimension, the linear cell countis defined as n. (See Fig. 3.)3.1.15 modulus of elasticity, FL-2, nthe ratio of stress tocorrespondin
43、g strain below the proportional limit. E63.1.16 nominal beam strength, SNB, FL-2, nIn honey-comb test specimens, a measure of the maximum strength inbending, calculated with the simple elastic beam equationsusing the overall specimen dimensions, disregarding thecellular/channel architecture, and mak
44、ing the simplifying as-sumption of a solid continuum in the bar. The nominal beamstrength is not necessarily representative of the true failurestress in the outer fiber face, because it does not take the effectof channel porosity on the moment of inertia into account. (SeeSection 11 and Appendix X1.
45、)3.1.16.1 DiscussionThe nominal beam strength is calcu-lated without consideration of the dimensions, geometry/shape,cell wall thickness, or linear cell count of the cellular channelarchitecture in the test specimen. The nominal beam strengthcan be used for material comparison and quality control fo
46、rflexure test specimens of equal size, comparable cell geometry,and equivalent loading configuration.3.1.16.2 DiscussionFor specimens where the minimumlinear cell count is less than 15, the nominal beam strengthshould not be used for design purposes or material propertycharacterization, because it i
47、s not necessarily an accurateapproximation of the true failure stress (material strength) inthe outer fiber face of the specimen.3.1.17 relative density (percent), na relative measurementof the density of a porous material, defined as the ratio(expressed as a percent) of the bulk density of the spec
48、imen tothe true/theoretical density of the material composition. Therelative density of the specimen is equal to 1 minus thefractional porosity, expressed as a percent. The relative densityaccounts for both channel porosity and wall porosity.3.1.18 semi-articulating fixture, na flexure fixture de-si
49、gned to be used with flat and parallel specimens. The fixtureallows some articulation, or pivoting, to ensure the top pair (orbottom pair) of bearing cylinders pivot together about an axisparallel to the specimen long axis, in order to match thespecimen surfaces. In addition, the upper or lower pairs are freeto pivot to distribute force evenly to the bearing cylinders oneither side. (See Annex A1 for schematics.) C 11613.1.19 three-point flexure, nconfiguration of flexuralstrength testing where a specimen is loaded at a locatio
