1、Designation: C 1337 96 (Reapproved 2005)Standard Test Method forCreep and Creep Rupture of Continuous Fiber-ReinforcedCeramic Composites under Tensile Loading at ElevatedTemperatures1This standard is issued under the fixed designation C 1337; the number immediately following the designation indicate
2、s the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of
3、the time-dependent deformation and time-to-rupture of continuousfiber-reinforced ceramic composites under constant tensileloading at elevated temperatures. This test method addresses,but is not restricted to, various suggested test specimengeometries. In addition, specimen fabrication methods, allow
4、-able bending, temperature measurements, temperature control,data collection, and reporting procedures are addressed.1.2 This test method is intended primarily for use with alladvanced ceramic matrix composites with continuous fiberreinforcement: unidirectional (1-D), bidirectional (2-D), andtridire
5、ctional (3-D). In addition, this test method may also beused with glass matrix composites with 1-D, 2-D, and 3-Dcontinuous fiber reinforcement. This test method does notaddress directly discontinuous fiber-reinforced, whisker-reinforced, or particulate-reinforced ceramics, although the testmethods d
6、etailed here may be equally applicable to thesecomposites.1.3 Values expressed in this test method are in accordancewith the International System of Units (SI) and IEEE/ASTM SI10.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is therespon
7、sibility 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. Hazard statementsare noted in 7.1 and 7.2.2. Referenced Documents2.1 ASTM Standards:2C 1145 Terminology on Advanced CeramicsC 1275 Test
8、 Method for Monotonic Tensile Behavior ofContinuous Fiber-Reinforced Advanced Ceramics withSolid Rectangular Cross-Section Test Specimens at Ambi-ent TemperatureD 3878 Terminology for Composite MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mech
9、anical Test-ingE83 Practice for Verification and Classification of Exten-someter SystemE 139 Practice for Conducting Creep, Creep Rupture, andStress Rupture Tests of Metallic MaterialsE 220 Test Method for Calibration of Thermocouples ByComparison TechniquesE 230 Specification for Temperature-Electr
10、omotive Force(EMF) Tables for Standardized ThermocouplesE 337 Test Method for Measuring Humidity with a Psy-chrometer (The Measurement of Wet- and Dry-Bulb Tem-peratures)E 1012 Practice for Verification of Specimen Alignmentunder Tensile LoadingIEEE/ASTM SI 10 American National Standard for Use ofth
11、e International System of Units (SI): The Modern MetricSystem3. Terminology3.1 DefinitionsThe definitions of terms relating to tensiletesting appearing in Terminology E6apply to the terms used inthis test method. The definitions relating to advanced ceramicsappearing in Terminology C 1145 apply to t
12、he terms used inthis test method. The definitions of terms relating to fiberreinforced composites appearing in Terminology D 3878 applyto the terms used in this test method. Additional terms used inconjunction with this test method are defined in the following:3.1.1 continuous fiber-reinforced ceram
13、ic matrix composite(CFCC)ceramic matrix composite in which the reinforcingphase consists of a continuous fiber, continuous yarn, or awoven fabric.1This test method is under the jurisdiction of ASTM Committee C28 onAdvanced Ceramics and is the direct responsibility of Subcommittee C28.07 onCeramic Ma
14、trix Composites.Current edition approved June 1, 2005. Published June 2005. Originallyapproved in 1996. Last previous edition approved in 2000 as C 1337 96 (2000).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book
15、 of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.2 fracture strengthtensile stress which the materialsustains at the instant of
16、fracture. Fracture strength is calcu-lated from the load at fracture during a tension test carried torupture and the original cross-sectional area of the specimen.3.1.2.1 DiscussionIn some cases, the fracture strengthmay be identical to the tensile strength if the load at fracture isthe maximum for
17、the test. Factors such as load train compli-ance and fiber pull-out behavior may influence the fracturestrength.3.1.3 proportional limit stressgreatest stress which a ma-terial is capable of sustaining without any deviation fromproportionality of stress to strain (Hookes law).3.1.3.1 DiscussionMany
18、experiments have shown thatvalues observed for the proportional limit vary greatly with thesensitivity and accuracy of the testing equipment, eccentricityof loading, the scale to which the stress-strain diagram isplotted, and other factors. When determination of proportionallimit is required, the pr
19、ocedure and sensitivity of the testequipment shall be specified.3.1.4 slow crack growthsubcritical crack growth (exten-sion) which may result from, but is not restricted to, suchmechanisms as environmentally assisted stress corrosion ordiffusive crack growth.4. Significance and Use4.1 This test meth
20、od may be used for material development,material comparison, quality assurance, characterization, anddesign data generation.4.2 Continuous fiber-reinforced ceramic matrix compositesare candidate materials for structural applications requiringhigh degrees of wear and corrosion resistance and toughnes
21、s athigh temperatures.4.3 Creep tests measure the time-dependent deformation ofa material under constant load at a given temperature. Creeprupture tests provide a measure of the life of the material whensubjected to constant mechanical loading at elevated tempera-tures. In selecting materials and de
22、signing parts for service atelevated temperatures, the type of test data used will depend onthe criteria for load carrying capability which best defines theservice usefulness of the material.4.4 Creep and creep rupture tests provide information on thetime-dependent deformation and on the time-of-fai
23、lure ofmaterials subjected to uniaxial tensile stresses at elevatedtemperatures. Uniform stress states are required to effectivelyevaluate any nonlinear stress-strain behavior which may de-velop as the result of cumulative damage processes (forexample, matrix cracking, matrix/fiber debonding, fiber
24、frac-ture, delamination, etc.) which may be influenced by testingmode, testing rate, processing or alloying effects, environmen-tal influences, or elevated temperatures. Some of these effectsmay be consequences of stress corrosion or subcritical (slow)crack growth. It is noted that ceramic materials
25、 typically creepmore rapidly in tension than in compression. Therefore, creepdata for design and life prediction should be obtained in bothtension and compression.4.5 The results of tensile creep and tensile creep rupturetests of specimens fabricated to standardized dimensions froma particular mater
26、ial or selected portions of a part, or both, maynot totally represent the creep deformation and creep ruptureproperties of the entire, full-size end product or its in-servicebehavior in different environments or at various elevatedtemperatures.4.6 For quality control purposes, results derived from s
27、tan-dardized tensile test specimens may be considered indicative ofthe response of the material from which they were taken forgiven primary processing conditions and post-processing heattreatments.5. Interferences5.1 Test environment (vacuum, inert gas, ambient air, etc.)including moisture content (
28、for example, relative humidity)may have an influence on the creep and creep rupture behaviorof CFCCs. In particular, the behavior of materials susceptibleto slow crack growth fracture and oxidation will be stronglyinfluenced by test environment and test temperature. Testingcan be conducted in enviro
29、nments representative of serviceconditions to evaluate material performance under these con-ditions.5.2 Surface preparation of test specimens, although nor-mally not considered a major concern with CFCCs, canintroduce fabrication flaws which may have pronounced effectson the mechanical properties an
30、d behavior (for example, shapeand level of the resulting stress-strain-time curve, etc.). Ma-chining damage introduced during specimen preparation can beeither a random interfering factor in the ultimate strength ofpristine material (that is, increased frequency of surface-initiated fractures compar
31、ed to volumeinitiated fractures) or aninherent part of the strength characteristics to be measured.Surface preparation can also lead to the introduction of residualstresses. Universal or standardized test methods of surfacepreparation do not exist. It should be understood that finalmachining steps m
32、ay or may not negate machining damageintroduced during the initial machining. Thus, specimen fabri-cation history may play an important role in the measuredtime-to-failure or deformation, and shall be reported. In addi-tion, the nature of fabrication used for certain composites (forexample, chemical
33、 vapor infiltration or hot pressing) mayrequire the testing of specimens in the as-processed condition(that is, it may not be possible to machine the specimen faceswithout compromising the in-plane fiber architecture).5.3 Bending in uniaxial tests does induce nonuniform stressdistributions. Bending
34、may be introduced from several sourcesincluding misaligned load trains, eccentric or misshaped speci-mens, and nonuniformly heated specimens or grips. In addi-tion, if deformations or strains are measured at surfaces wheremaximum or minimum stresses occur, bending may introduceover or under measurem
35、ent of strains depending on thelocation of the strain measuring device on the specimen.Similarly, fracture from surface flaws may be accentuated orsuppressed by the presence of the nonuniform stresses causedby bending.5.4 Fractures that initiate outside the uniformly stressedgage section of a specim
36、en may be due to factors such as stressconcentrations or geometrical transitions, extraneous stressesintroduced by gripping or thermal gradients, or strength limit-ing features in the microstructure of the specimen. Suchnon-gage section fractures will normally constitute invalidtests. In addition, f
37、or face-loaded geometries, gripping pressureC 1337 96 (2005)2is a key variable in the initiation of fracture. Insufficientpressure can shear the outer plies in laminated CFCCs, whiletoo much pressure can cause local crushing of the CFCC andlead to fracture in the vicinity of the grips.5.5 The time-d
38、ependent stress redistribution that occurs atelevated temperatures among the CFCC constituents makes itnecessary that the precise loading history of a creep specimenbe specified. This is of particular importance since the rate atwhich a creep load is initially applied can influence thesubsequent cre
39、ep behavior and damage modes. For example,whether matrix cracking would occur at the end of loading willdepend on the magnitude of the loading rate, the test stress, thetest temperature and the relative creep resistance of the matrixwith respect to that of the fibers.3,45.6 When CFCCs are mechanical
40、ly unloaded either partiallyor totally after a creep test during which the specimenaccumulated time-dependent deformation, the specimen mayexhibit creep recovery as manifested by a time-dependentreduction of strain. The rate of creep recovery is usually slowerthan the rate of creep deformation, and
41、both creep and creeprecovery are in most cases thermally activated processes,making them quite sensitive to temperature. Often it is desiredto determine the retained strength of a CFCC after beingsubjected to creep for a prescribed period of time. Therefore, itis customary to unload the specimen fro
42、m the creep stress andthen reload it monotonically until failure. Under these circum-stances, the time elapsed between the end of the creep test andthe conduction of the monotonic fast fracture test to determinethe retained strength as well as the loading and unloading rateswill influence the rate o
43、f internal stress redistribution amongthe phases and hence the CFCC strength.6. Apparatus6.1 Testing MachinesMachines used for tensile testingshall conform to the requirements of Practices E4. The loadsused shall be accurate within 61 % at any load within theselected load range of the testing machin
44、e as defined inPractices E4.6.2 Gripping Devices:6.2.1 GeneralVarious types of gripping devices may beused to transmit the measured load applied by the testingmachine to the test specimens. The brittle nature of thematrices of CFCCs requires that a uniform interface existsbetween the grip components
45、 and the gripped section of thespecimen. Line or point contacts and nonuniform pressure canproduce Hertzian-type stresses leading to crack initiation andfracture of the specimen in the gripped section. Grippingdevices can be classified generally as those employing activeand those employing passive g
46、rip interfaces as discussed in thefollowing sections. Grips located outside the heated zonesurrounding the specimen may or may not employ cooling.Uncooled grips located outside the heated zone are termedwarm grips and generally reduce the thermal gradient in thespecimen but at the expense of using h
47、igh-temperature alloygrips and increased degradation of the grips due to exposure tothe elevated-temperature environment. Cooled grips locatedoutside the heated zone are termed cold grips and generallyinduce a steep thermal gradient along the length of thespecimen.NOTE 1The expense of the cooling sy
48、stem for cold grips is balancedagainst maintaining alignment that remains consistent from test to test(stable grip temperature) and decreased degradation of the grips due toexposure to the elevated-temperature environment. When grip cooling isemployed, provisions shall be provided to control the coo
49、ling medium tomaximum fluctuations of 5 K (less than 1 K preferred) about a setpointtemperature over the course of the test to minimize thermally inducedstrain changes in the specimen. In addition, opposing grip temperaturesshould be maintained at uniform and consistent temperatures not to exceeda difference 65 K (less than 61 K preferred) so as to avoid inducingunequal thermal gradients and subsequent nonuniaxial stresses in thespecimen. Generally, the need for control of grip temperature fluctuationsor differences may be indicated if specimen gage section temperaturescan
