1、Designation: C 1468 06Standard Test Method forTransthickness Tensile Strength of Continuous Fiber-Reinforced Advanced Ceramics at Ambient Temperature1This standard is issued under the fixed designation C 1468; the number immediately following the designation indicates the year oforiginal adoption or
2、, 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 transthick-ness tensile strength
3、SUT! under monotonic uniaxial forcing ofcontinuous fiber-reinforced ceramics (CFCC) at ambient tem-perature. This test method addresses, but is not restricted to,various suggested test specimen geometries, test fixtures, datacollection and reporting procedure. In general, round or squaretest specime
4、ns are tensile tested in the direction normal to thethickness by bonding appropriate hardware to the samples andperforming the test. For a Cartesian coordinate system, thex-axis and the y-axis are in the plane of the test specimen. Thetransthickness direction is normal to the plane and is labeledthe
5、 z-axis for this test method. For CFCCs, the plane of the testspecimen normally contains the larger of the three dimensionsand is parallel to the fiber layers for uni-directional, bi-directional, and woven composites. Note that transthicknesstensile strength as used in this test method refers to the
6、 tensilestrength obtained under monotonic uniaxial forcing wheremonotonic refers to a continuous nonstop test rate with noreversals from test initiation to final fracture.1.2 This test method is intended primarily for use with alladvanced ceramic matrix composites with continuous fiberreinforcement:
7、 unidirectional (1-D), bidirectional (2-D), wo-ven, and tridirectional (3-D). In addition, this test method alsomay be used with glass (amorphous) matrix composites with1-D, 2-D, and 3-D continuous fiber reinforcement. This testmethod does not address directly discontinuous fiber-reinforced, whisker
8、-reinforced or particulate-reinforced ceram-ics, although the test methods detailed here may be equallyapplicable to these composites. It should be noted that 3-Darchitectures with a high volume fraction of fibers in the “z”direction may be difficult to test successfully.1.3 Values are in accordance
9、 with the International Systemof Units (SI) and IEEE/ASTM SI 10.1.4 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 appli
10、ca-bility of regulatory limitations prior to use. Additional recom-mendations are provided in 6.7 and Section 7.2. Referenced Documents2.1 ASTM Standards:2C 1145 Terminology of Advanced CeramicsC 1239 Practice for Reporting Uniaxial Strength Data andEstimating Weibull Distribution Parameters for Adv
11、ancedCeramicsC 1275 Test 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 Rel
12、ating 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 American National Standard for Use ofthe International System of Units (SI): The Modern MetricSystem.E 1012 Practice for Verificati
13、on of Test Frame and Speci-men Alignment Under Tensile and Compressive AxialForce Application3. Terminology3.1 DefinitionsThe definitions of terms relating to tensiletesting appearing in Terminology E6apply to the terms used inthis test method. The definitions of terms relating to advancedceramics a
14、ppearing in Terminology C 1145 apply to the termsused in this test method. The definitions of terms relating tofiber-reinforced composites appearing in Terminology D 3878apply to the terms used in this test method. Pertinent definitionsas listed in Practice E 1012, Terminology C 1145, TerminologyD 3
15、878, and Terminology E6are shown in the following with1This 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 Jan. 1, 2006. Published January 2006. Originallyapp
16、roved in 2000. Last previous edition approved in 2000 as C1468 00.2For 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 web
17、site.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.the appropriate source given in brackets. Terms used inconjunction with this test method are defined as follows:3.1.1 advanced ceramic, na highly-engineered, high-performance predo
18、minately nonmetallic, inorganic, ceramicmaterial having specific functional attributes. C 11453.1.2 bending strain, nthe difference between the strain atthe surface and the axial strain. E 10123.1.3 breaking force, nthe force at which fracture occurs,Pmax, is the breaking force in units of N. E63.1.
19、4 ceramic matrix composite (CMC), na material con-sisting of two or more materials (insoluble in one another), inwhich the major, continuous component (matrix component) isa ceramic, while the secondary component(s) (reinforcingcomponent) may be ceramic, glass-ceramic, glass, metal ororganic in natu
20、re. These components are combined on amacroscale to form a useful engineering material possessingcertain properties or behavior not possessed by the individualconstituents. C 11453.1.5 continuous fiber-reinforced ceramic matrix composite(CFCC), na ceramic matrix composite in which the reinforc-ing p
21、hases consists of continuous filaments, fibers, yarn, orknitted or woven fabrics. C 11453.1.6 gage length, nthe original length LGL of thatportion of the test specimen over which strain or change oflength is determined. E63.1.7 modulus of elasticity, nthe ratio of stress to corre-sponding strain bel
22、ow the proportional limit. E63.1.8 percent bending, nthe bending strain times 100divided by the axial strain. E 10123.1.9 tensile strength, nthe maximum tensile stress, whicha material is capable of sustaining. Tensile strength is calcu-lated from the maximum force during a tension test carried toru
23、pture and the original cross-sectional area of the test speci-men. E63.2 Definitions of Terms Specific to This Standard:3.2.1 transthickness, nthe direction parallel to the thick-ness, that is, out-of-plane dimension, as identified in 1.1, andalso typically normal to the plies for 1-D, 2-D laminate,
24、 andwoven cloth. For 3-D laminates this direction is typically takento be normal to the thickness and associated with the “z”direction.3.2.2 fixturing, nfixturing is referred to as the device(s)bonded to the test specimen. It is this device(s) that is actuallygripped or pinned to the force train. Th
25、e fixturing transmits theapplied force to the test specimen.4. Significance and Use4.1 This test method may be used for material development,material comparison, quality assurance, characterization, anddesign data generation.4.2 Continuous fiber-reinforced ceramic matrix compositesgenerally are char
26、acterized by fine grain sized (65 % RH is not recom-mended and any deviations from this recommendation must bereported.5.2 Surface and edge preparation of test specimens, al-though normally not considered a major concern in CFCCs,can introduce fabrication flaws which may have pronouncedeffects on th
27、e measured transthickness strength (1).3Machiningdamage introduced during test specimen preparation can beeither a random interfering factor in the determination ofstrength of pristine material, that is, increased frequency ofsurface-initiated fractures compared to volume-initiated frac-tures, or an
28、 inherent part of the strength characteristics.Universal or standardized test methods of surface and edgepreparation do not exist. It should be understood that finalmachining steps may, or may not, negate machining damageintroduced during the initial machining; thus, test specimenfabrication history
29、 may play an important role in the measuredstrength distributions and should be reported. In addition, thenature of fabrication used for certain composites, for example,chemical vapor infiltration or hot pressing, may require thetesting of test specimens in the as-processed condition.5.3 Bending in
30、uniaxial transthickness tensile tests cancause or promote nonuniform stress distributions with maxi-mum stresses occurring at the test specimen edge leading tononrepresentative fractures. Similarly, fracture from edge flawsmay be accentuated or suppressed by the presence of thenonuniform stresses ca
31、used by bending.NOTE 1Finite element calculations were performed for the squarecross section test specimen for the forcing conditions and test specimenthickness investigated in reference (1). Stress levels along the four corneredges were found to be lower than the interior, except for the corners at
32、 thebond lines where the stress was slightly higher than the interior. Stresslevels along the sides and interior of the test specimen were found to beuniform.6. Apparatus6.1 Testing MachinesMachines used for transthicknesstensile testing shall conform to the requirements of PracticeE4. The forces us
33、ed in determining tensile strength shall beaccurate within 61 % at any force within the selected forcerange of the testing machine as defined in Practice E4.Aschematic showing pertinent features of the transthicknesstensile testing apparatus for two possible forcing configurationsis shown in Figs. 1
34、 and 2.6.1.1 Values for transthickness tensile strength can range agreat deal for different types of CFCC. Therefore, it is helpfulto know an expected strength value in order to properly selecta force range. Approximate transthickness tensile strengthvalues (1) for several CFCCs are as follows: poro
35、us oxide/oxide composites range from 210 MPa, hot pressed fullydense SiC/MAS-5 glass-ceramic composites range from 1427MPa, Polymer Infiltrated and Pyrolyzed (PIP) SiC/SiNC rangefrom 1532 MPa, and hot pressed SCS-6/Si3N4range from3043 MPa.6.1.2 For any testing apparatus, the force train will need to
36、be aligned for angularity and concentricity. Alignment of thetesting system will need to be measured and is detailed in A1.1of Test Method C 1275.6.2 Gripping Devices:6.2.1 GeneralVarious types of gripping devices may beused to transmit the force applied by the testing machine to thetest fixtures an
37、d into the test specimens. The brittle nature ofthe matrices of CFCCs requires accurate alignment. Bendingmoments can produce stresses leading to premature crack3The boldface numbers in parentheses refers to the list of references at the endof this standard.FIG. 1 Schematic Diagram of One Possible A
38、pparatus forConducting a Uniaxially-Forced Transthickness Tensile TestFIG. 2 Schematic Diagram of a Second Possible Apparatus forConducting a Uniaxially-Forced Transthickness Tensile TestC1468063initiation and fracture of the test specimen. Gripping devicescan be classified generally as those employ
39、ing active and thoseemploying passive grip interfaces as discussed in the followingsections. Several additional gripping techniques are discussedin Test Method C 1275.6.2.1.1 Active Grip InterfacesActive grip interfaces re-quire a continuous application of a mechanical, hydraulic, orpneumatic force
40、to transmit the force applied by the testmachine to the test fixtures. Generally, these types of gripinterfaces cause a force to be applied normal to the surface ofthe gripped section of the test fixturing. Transmission of theuniaxial force applied by the test machine then is accomplishedby friction
41、 between the test fixturing and the grip faces; thus,important aspects of active grip interfaces are uniform contactbetween the gripped section of the test fixturing and the gripfaces and constant coefficient of friction over the grip/fixtureinterface. In addition, for active grips, uniform applicat
42、ion ofgripping force and motion of the grips upon actuation areimportant factors to consider in assuring proper gripping.(1) Face-forceed grips, either by direct lateral pressure gripfaces (2) or by indirect wedge-type grip faces, act as the gripinterface (3). Generally, close tolerances are require
43、d for theflatness and parallelism as well as for the wedge angle of thewedge grip faces. In addition, the thickness, flatness, andparallelism of the gripped section of the fixturing shall bewithin similarly close tolerances to promote uniform contact atthe fixture/grip interface. Tolerances will var
44、y depending onthe exact configuration.(2) Sufficient lateral pressure should be applied to preventslippage between the grip face and the fixturing. Grip surfacesthat are scored or serrated with a pattern similar to that of asingle-cut file have been found satisfactory. A fine serrationappears to be
45、the most satisfactory. The serrations should bekept clean and well defined but not overly sharp. The length Land width W of the grip faces should be equal to or greaterthan the respective length and width of the fixturing to begripped.(3) Grip inserts, called wedges, can be machined to acceptflat or
46、 round fixturing. This allows for a wide range of fixturingto be utilized.6.2.1.2 Passive Grip InterfacesPassive grip interfacestransmit the force applied by the test machine through a directmechanical link (4). Generally, these mechanical links transmitthe test forces to the test specimen via geome
47、trical features ofthe test fixturing. Passive grips may act through pin forcing viapins at holes in the fixturing. Generally, close tolerances oflinear dimensions are required to promote uniform contact aswell as to provide for noneccentric forcing. In addition,moderately close tolerances are requir
48、ed for center-line coin-cidence and diameter D of the pins and holes.6.3 force Train Couplers:6.3.1 GeneralVarious types of devices (force train cou-plers) may be used to attach the active or passive grip interfaceassemblies to the testing machine (1,5,6,7). The force traincouplers in conjunction wi
49、th the type of gripping device playmajor roles in the alignment of the force train, and thus,subsequent bending imposed in the test specimen. force traincouplers can be classified generally as fixed and non-fixed asdiscussed in the following sections. Note that use of well-aligned fixed or self-aligning non-fixed couplers does notautomatically guarantee low ending in the test specimen. Thetype and operation of grip interfaces, as well as the as-fabricated dimensions of the test specimen can add signifi-cantly to the final bending impose
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