1、Designation: C1425 11Standard Test Method forInterlaminar Shear Strength of 1D and 2D ContinuousFiber-Reinforced Advanced Ceramics at ElevatedTemperatures1This standard is issued under the fixed designation C1425; the number immediately following the designation indicates the year oforiginal adoptio
2、n 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 addresses the compression of a double-notched test specime
3、n to determine interlaminar shear strengthof continuous fiber-reinforced ceramic composites (CFCCs) atelevated temperatures. Failure of the test specimen occurs byinterlaminar shear between two centrally located notchesmachined halfway through the thickness of the test specimenand spaced a fixed dis
4、tance apart on opposing faces (see Fig.1). Test specimen preparation methods and requirements,testing modes (force or displacement control), testing rates(force rate or displacement rate), data collection, and reportingprocedures are addressed.1.2 This test method is used for testing advanced cerami
5、c orglass matrix composites with continuous fiber reinforcementhaving a laminated structure such as in unidirectional (1-D) orbidirectional (2-D) fiber architecture (lay-ups of unidirectionalplies or stacked fabric). This test method does not addresscomposites with nonlaminated structures, such as (
6、3-D) fiberarchitecture or discontinuous fiber-reinforced, whisker-reinforced, or particulate-reinforced ceramics.1.3 Values expressed in this test method are in accordancewith the International System of Units (SI) and IEEE/ASTMSI 10.1.4 This standard does not purport to address all of thesafety con
7、cerns, 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 regulatory limitations prior to use. Specific precau-tionary statements are noted in 8.1 and 8.2.2. Referenced Docume
8、nts2.1 ASTM Standards:2C1145 Terminology of Advanced CeramicsC1292 Test Method for Shear Strength of Continuous Fiber-Reinforced Advanced Ceramics at Ambient TemperaturesD695 Test Method for Compressive Properties of RigidPlasticsD3846 Test Method for In-Plane Shear Strength of Rein-forced PlasticsD
9、3878 Terminology for Composite MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE122 Practice for Calculating Sample Size to Estimate,With Specified Precision, the Average for a Characteristicof a Lot or ProcessE220 Test Method f
10、or Calibration of Thermocouples ByComparison TechniquesE230 Specification and Temperature-Electromotive Force(EMF) Tables for Standardized ThermocouplesE337 Test Method for Measuring Humidity with a Psy-chrometer (the Measurement of Wet- and Dry-Bulb Tem-peratures)IEEE/ASTM SI 10 American National S
11、tandard for Use ofthe International System of Units (SI): The Modern MetricSystem3. Terminology3.1 DefinitionsThe definitions of terms relating to shearstrength testing appearing in Terminology E6 apply to theterms used in this test method. The definitions of terms relatingto advanced ceramics appea
12、ring in Terminology C1145 apply1This test method is under the jurisdiction of ASTM Committee C28 onAdvanced Ceramics and is the direct responsibility of Subcommittee C28.07 onCeramic Matrix Composites.Current edition approved July 15, 2011. Published August 2011. Originallyapproved in 1999. Last pre
13、vious edition approved in 2005 as C1425 05. DOI:10.1520/C1425-11.2For 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 webs
14、ite.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.to the terms used in this test method. The definitions of termsrelating to fiber-reinforced composites appearing in Terminol-ogy D3878 apply to the terms used in this test method.3.
15、2 Definitions of Terms Specific to This Standard:3.2.1 shear failure force (F), nmaximum force required tofracture a shear-loaded test specimen. (C1292)3.2.2 shear strength (FL-2), nmaximum shear stress that amaterial is capable of sustaining. Shear strength is calculatedfrom the failure force in sh
16、ear and the shear area. (C1292)4. Summary of Test Method4.1 This test method addresses the determination of theinterlaminar shear strength of CFCCs at elevated temperatures.The interlaminar shear strength of CFCCs, as determined bythis test method, is measured by loading in compression adouble-notch
17、ed test specimen of uniform width. Failure of thetest specimen occurs by interlaminar shear between twocentrally located notches machined halfway through the thick-ness of the test specimen and spaced a fixed distance apart onopposing faces. Schematics of the loading mode and the testspecimen are sh
18、own in Fig. 1. The procedures in this testmethod are similar to those in Test Method C1292 for thedetermination of the interlaminar shear strength of CFCCs atambient temperature, except that the considerations for con-ducting the test at elevated temperatures are addressed in thistest method.5. Sign
19、ificance and Use5.1 Continuous fiber-reinforced ceramic composites arecandidate materials for structural applications requiring highdegrees of wear and corrosion resistance, and damage toler-ance at high temperatures.5.2 The 1-D and 2-D CFCCs are highly anisotropic andtheir transthickness tensile an
20、d interlaminar shear strength arelower than their in-plane tensile and in-plane shear strength,respectively.5.3 Shear tests provide information on the strength anddeformation of materials under shear stresses.5.4 This test method may be used for material development,material comparison, quality assu
21、rance, characterization, anddesign data generation.5.5 For quality control purposes, results derived from stan-dardized shear test specimens may be considered indicative ofthe response of the material from which they were taken forgiven primary processing conditions and post-processing heattreatment
22、s.6. Interferences6.1 Test environment (vacuum, inert gas, ambient air, and soforth) including moisture content (for example, relative humid-ity) may have an influence on the measured interlaminar shearstrength. In particular, the behavior of materials susceptible toslow crack growth will be strongl
23、y influenced by test environ-ment and testing rate. Testing to evaluate the maximumstrength potential of a material shall be conducted in inertenvironments or at sufficiently rapid testing rates, or both, so asto minimize slow crack growth effects. Conversely, testing canbe conducted in environments
24、 and testing modes and ratesrepresentative of service conditions to evaluate material per-formance under those conditions. When testing is conducted inuncontrolled ambient air with the objective of evaluatingmaximum strength potential, relative humidity and temperaturemust be monitored and reported.
25、 Testing at humidity levels65 % RH is not recommended and any deviations from thisrecommendation must be reported.6.2 Preparation of test specimens, although normally notconsidered a major concern with CFCCs, can introduce fabri-cation flaws which may have pronounced effects on themechanical propert
26、ies and behavior (for example, shape andlevel of the resulting force-displacement curve and shearstrength). Machining damage introduced during test specimenpreparation can be either a random interfering factor in thedetermination of shear strength of pristine material, or aninherent part of the stre
27、ngth characteristics to be measured.Universal or standardized test methods of surface preparationdo not exist. Final machining steps may, or may not, negateFIG. 1 Schematic of Compression of Double-Notched TestSpecimen for the Determination of Interlaminar Shear Strength ofCFCCsC1425 112machining da
28、mage introduced during the initial machining.Thus, test specimen fabrication history may play an importantrole in the measured strength distributions and shall bereported.6.3 Bending in uniaxially loaded shear tests can cause orpromote non-uniform stress distributions that may alter thedesired state
29、 of stress during the test. For example, non-uniform loading will occur if the loading surfaces of the testspecimen are not flat and parallel.6.4 Fractures that initiate outside the gage section of a testspecimen may be due to factors such as localized stressconcentrations, extraneous stresses intro
30、duced by improperloading configurations, or strength-limiting features in themicrostructure of the test specimen. Such non-gage sectionfractures will normally constitute invalid tests.6.5 For the evaluation of the interlaminar shear strength bythe compression of a double-notched test specimen, the d
31、is-tance between the notches has an effect on the maximum forceand therefore on the interlaminar shear strength.3,4,5It has beenfound that the stress distribution in the gage section of the testspecimen is independent of the distance between the notcheswhen the notches are far apart. However, when t
32、he distancebetween the notches is such that the stress fields around thenotches interact, the measured interlaminar shear strengthincreases. Because of the complexity of the stress field aroundeach notch and its dependence on the properties and homoge-neity of the material, conduct a series of tests
33、 on test specimenswith different spacing between the notches to determine theeffect of notch separation on the measured interlaminar shearstrength.6.6 For the evaluation of the interlaminar shear strength bythe compression of a double-notched test specimen, excessiveclamping forces will reduce the s
34、tress concentration around thenotches and, therefore, artificially increase the measured inter-laminar shear strength. Excessive clamping might occur ifinterference between the test fixure and the test specimenresults from mismatch in their thermal expansion. Section 7.6provides guidance to prevent
35、this problem.6.7 The interlaminar shear strength of 1-D and 2-D CFCCsis controlled either by the matrix-rich interlaminar regions orby the weakest of the fiber-matrix interfaces. Whetherinterlaminar-shear failure initiates at the matrix-rich interlami-nar region or at the weakest of the fiber/matrix
36、 interfacesdepends on the location of the root of the notch, where theinterlaminar shear stress is largest, with respect to the inter-laminar microstructural features.7. Apparatus7.1 Testing MachinesThe testing machine shall be inconformance with Practices E4. The forces used in determiningshear str
37、ength shall be accurate within 61 % at any forcewithin the selected force range of the testing machine asdefined in Practices E4.7.2 Heating ApparatusThe apparatus for, and method of,heating the test specimens shall provide the temperaturecontrol necessary to satisfy the requirement of 10.2.7.2.1 He
38、ating can be by indirect electrical resistance (heat-ing elements), indirect induction through a susceptor, or radiantlamp with the test specimen in ambient air at atmosphericpressure unless other environments are specifically applied andreported. Note that direct resistance heating is not recom-men
39、ded for heating CFCCs due to possible differences of theelectrical resistance of the constituent materials which mayproduce nonuniform heating of the test specimen.7.3 Temperature-Measuring ApparatusThe method oftemperature measurement shall be sufficiently sensitive andreliable to ensure that the t
40、emperature of the test specimen iswithin the limits specified in 10.2.7.3.1 Primary temperature measurement shall be made withthermocouples in conjunction with potentiometers, millivolt-meters, or electronic temperature controllers or readout units,or combination thereof. Such measurements are subje
41、ct to twotypes of error. Thermocouple calibration and instrument mea-suring errors initially produce uncertainty as to the exacttemperature. Secondly, both thermocouples and measuringinstruments may be subject to variations over time. Commonerrors encountered in the use of thermocouples to measurete
42、mperatures include: calibration error, drift in calibration dueto contamination or deterioration with use, lead-wire error,error arising from method of attachment to the test specimen,direct radiation of heat to the bead, heat conduction alongthermocouple wires, and so forth.7.3.2 Temperature measur
43、ements shall be made with ther-mocouples of known calibration. Representative thermo-couples shall be calibrated from each lot of wires used formaking noble-metal (for example, platinum or rhodium) ther-mocouples. Except for relatively low temperatures of exposure,noble-metal thermocouples are event
44、ually subject to error uponreuse. Oxidized noble-metal thermocouples shall not be reusedwithout clipping back to remove wire exposed to the hot zone,re-welding, and annealing. Any reuse of noble-metal thermo-couples after relatively low-temperature use without this pre-caution shall be accompanied b
45、y re-calibration data demon-strating that calibration was not unduly affected by theconditions of exposure.7.3.3 Measurement of the drift in calibration of thermo-couples during use is difficult. When drift is a problem duringtests, a method shall be devised to check the readings of thethermocouples
46、 monitoring the test specimen temperature dur-ing the test. For reliable calibration of thermocouples after use,the temperature gradient of the test furnace must be reproducedduring the re-calibration.3Whitney, J. M., “Stress Analysis of the Double Notch Shear Specimen,”Proceedings of the American S
47、ociety for Composites, 4th Technical Conference,Blacksburg, VA, Technomic Publishing Co., Oct. 3-5, 1989, pp. 325.4Fang, N. J. J., and Chou, T. W., “Characterization of Interlaminar ShearStrength of Ceramic Matrix Composites,” Journal Am. Ceram. Soc., 76, 10 1993,pp. 2539-48.5Lara-Curzio, E., and Fe
48、rber, M. K., “Shear Strength of Continuous FiberReinforced Ceramic Composites,” in Thermal and Mechanical Test Methods andBehavior of Continuous Fiber Ceramic Composites, ASTM STP 1309M, G. Jenkins,S. T. Gonczy, E. Lara-Curzio, N. E. Ashgaugh, and L. P. Zawada, eds., AmericanSociety for Testing and
49、Materials, Philadelphia, PA, 1996.C1425 1137.3.4 Temperature-measuring, controlling, and recording in-struments shall be calibrated against a secondary standard,such as precision potentiometer, optical pyrometer, or black-body thyristor. Lead-wire error shall be checked with the leadwires in place as they normally are used. For thermocouplecalibration procedures refer to Test Method E220 and Specifi-cation E230.7.4 Data AcquisitionAt a minimum, autographic recordsof applied force and cross-head displacement versus time shallbe obtained. Either analog chart recorders or
