1、Designation: C1557 03 (Reapproved 2013)Standard Test Method forTensile Strength and Youngs Modulus of Fibers1This standard is issued under the fixed designation C1557; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of las
2、t 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 preparation, mounting, andtesting of single fibers (obtained either from a fiber bundle ora s
3、pool) for the determination of tensile strength and Youngsmodulus at ambient temperature. Advanced ceramic, glass,carbon and other fibers are covered by this test standard.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3
4、This standard may involve hazardous materials,operations, and equipment. This standard does not purport toaddress all of the safety concerns, if any, associated with itsuse. It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-mine the a
5、pplicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C1239 Practice for Reporting Uniaxial Strength Data andEstimating Weibull Distribution Parameters for AdvancedCeramicsD3878 Terminology for Composite MaterialsE4 Practices for Force Verification of Testing
6、 MachinesE6 Terminology Relating to Methods of Mechanical TestingE1382 Test Methods for Determining Average Grain SizeUsing Semiautomatic and Automatic Image Analysis3. Terminology3.1 Definitions:3.1.1 bundlea collection of parallel fibers. Synonym, tow.3.1.2 mounting taba thin paper, cardboard, com
7、pliantmetal, or plastic strip with a center hole or longitudinal slot offixed gage length. The mounting tab should be appropriatelydesigned to be self-aligning if possible, and as thin as practi-cable to minimize fiber misalignment.3.1.3 system compliancethe contribution by the load trainsystem and
8、specimen-gripping system to the indicated cross-head displacement, by unit of force exerted in the load train.3.2 For definitions of other terms used in this test method,refer to Terminologies D3878 and E6.4. Summary of Test Method4.1 A fiber is extracted randomly from a bundle or from aspool.4.2 Th
9、e fiber is mounted in the testing machine, and thenstressed to failure at a constant cross-head displacement rate.4.3 A valid test result is considered to be one in which fiberfailure doesnt occur in the gripping region.4.4 Tensile strength is calculated from the ratio of the peakforce and the cross
10、-sectional area of a plane perpendicular tothe fiber axis, at the fracture location or in the vicinity of thefracture location, while Youngs modulus is determined fromthe linear region of the tensile stress versus tensile strain curve.5. Significance and Use5.1 Properties determined by this test met
11、hod are useful inthe evaluation of new fibers at the research and developmentlevels. Fibers with diameters up to 250 10-6m are covered bythis test method. Very short fibers (including whiskers) call forspecialized test techniques (1)3and are not covered by this testmethod. This test method may also
12、be useful in the initialscreening of candidate fibers for applications in polymer, metalor ceramic matrix composites, and quality control purposes.Because of their nature, ceramic fibers do not have a uniquestrength, but rather, a distribution of strengths. In most caseswhen the strength of the fibe
13、rs is controlled by one populationof flaws, the distribution of fiber strengths can be describedusing a two-parameter Weibull distribution, although otherdistributions have also been suggested (2,3). This test methodconstitutes a methodology to obtain the strength of a singlefiber. For the purpose o
14、f determining the parameters of the1This 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 Aug. 1, 2013. Published September 2013. Originallyapproved in 2003. La
15、st previous edition approved in 2008 as C1557 03 (2008).DOI: 10.1520/C1557-03R13.2For 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
16、 onthe ASTM website.3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1distribution of fiber strengths it is recommended to follow thistest m
17、ethod in conjunction with Practice C1239.6. Interferences6.1 The test environment may have an influence on themeasured tensile strength of fibers. In particular, the behaviorof fibers susceptible to slow crack growth fracture will bestrongly influenced by test environment and testing rate (4).Testin
18、g to evaluate the maximum strength potential of a fibershould be conducted in inert environments or at sufficientlyrapid testing rates, or both, so as to minimize slow crackgrowth effects. Conversely, testing can be conducted in envi-ronments and testing modes and rates representative of servicecond
19、itions to evaluate the strength of fibers under thoseconditions.6.2 Fractures that initiate outside the gage section of a fibermay be due to factors such as stress concentrations, extraneousstresses introduced by gripping, or strength-limiting features inthe microstructure of the specimen. Such non-
20、gage sectionfractures constitute invalid tests. When using active grippingsystems, insufficient pressure can lead to slippage, while toomuch pressure can cause local fracture in the gripping area.6.3 Torsional strains may reduce the magnitude of thetensile strength (5). Caution must be exercised whe
21、n mountingthe fibers to avoid twisting the fibers.6.4 Many fibers are very sensitive to surface damage.Therefore, any contact with the fiber in the gage length shouldbe avoided (4,6).7. Apparatus7.1 The apparatus described herein consists of a tensiletesting machine with one actuator (cross-head) th
22、at operates ina controllable manner, a gripping system and a load cell. Fig.1 and Fig. 2 show a picture and schematic of such a system.7.1.1 Testing MachineThe testing machine shall be inconformance with Practice E4. The failure forces shall beaccurate within 61 % at any force within the selected fo
23、rcerange of the testing machine as defined in Practice E4.Todetermine the appropriate capacity of the load cell, the follow-ing table lists the range of strength and diameter values ofrepresentative glass, graphite, organic and ceramic fibers.7.1.2 GripsThe gripping system shall be of such designtha
24、t axial alignment of the fiber along the line of action of themachine shall be easily accomplished without damaging thetest specimen. Although studies of the effect of fiber misalign-ment on the tensile strength of fibers have not been reported,the axis of the fiber shall be coaxial with the line of
25、 action ofthe testing machine within , to prevent spurious bendingstrains and/or stress concentrations:#lo50(1)where: = the tolerance, m, andlo= the fiber gage length, m.7.2 Mounting TabsTypical mounting tabs for test speci-mens are shown in Fig. 3. Alternative methods of specimenmounting may be use
26、d, or none at all (that is, the fiber may bedirectly mounted into the grips). A simple but effectiveapproach for making mounting tabs with repeatable dimen-sions consists in printing the mounting tab pattern ontocardboard file folders using a laser printer.As illustrated in Fig.3, holes can be obtai
27、ned using a three-hole punch. Fig. 3 showsa typical specimen mounting method. The mounting tabs aregripped or connected to the load train (for example, by pin andclevis) so that the test specimen is aligned axially along the lineof action of the test machine.7.2.1 When gripping large diameter fibers
28、 using an activeset of grips without tabs, the grip facing material in contactwith the test specimen must be of appropriate compliance toallow for a firm, non-slipping grip on the fiber. At the sametime, the grip facing material must prevent crushing, scoring orother damage to the test specimen that
29、 would lead to inaccurateresults. Large diameter fibers (diameter 50 10-6m) can alsobe mounted inside hypodermic needles filled with an adhesiveFIG. 1 Typical Fiber TesterC1557 03 (2013)2(7). This is a good alternative to avoid crushing the fiber ifpneumatic/hydraulic/mechanical grips were to be use
30、d. Theadhesive must be sufficiently strong to withstand the grippingprocess, and prevent fiber “pull-out” during testing.7.3 Data AcquisitionAt a minimum, autographic recordsof applied force and cross-head displacement versus time shallbe obtained. Either analog chart recorders or digital dataacquis
31、ition systems may be used for this purpose although adigital record is recommended for ease of later data analysis.Ideally, an analog chart recorder or plotter shall be used inconjunction with the digital data acquisition system to providean immediate record of the test as a supplement to the digita
32、lrecord. Recording devices must be accurate to 6 1 % of fullscale and shall have a minimum data acquisition rate of 10 Hzwith a response of 50 Hz deemed more than sufficient.8. Precautionary Statement8.1 During the conduct of this test method, the possibility offlying fragments of broken fibers may
33、be high. Means forcontaining these fragments for later fractographic reconstruc-tion and analysis is highly recommended. For example,vacuum grease has been used successfully to dampen the fiberduring failure and capture the fragments. In this case, vacuumgrease is applied in the gage section of the
34、fiber so that theformer does not bear any force. An appropriate solvent can beused afterwards to remove the vacuum grease.9. Procedure9.1 Test Specimen Mounting:9.1.1 Randomly choose, and carefully separate, a suitablesingle-fiber specimen from the bundle or fiber spool. The totallength of the speci
35、men should be sufficiently long (at least 1.5FIG. 2TABLE 1 Room Temperature Tensile Strength of Fibers (25 10-3m Gage Length)Fiber Diameter, m Strength, PaCVD-SiC 50-150 10-62-3.5 109polymer-derived SiC 10-18 10-62-3.5 109sol-gel derived oxide 1-20 10-61-3109single-crystal oxide 70-250 10-61.5-3.5 1
36、09graphite 1-15 10-61-6109glass 1-250 x 10-61-4109aramid 12-20 10-62-4109C1557 03 (2013)3times longer than the gage length) to allow for convenienthandling and gripping. Handle the test specimen at its ends andavoid touching it in the test gage length.NOTE 1Because the strength of fibers is statisti
37、cal in nature, themagnitude of the strength will depend on the dimensions of the fiber beingevaluated. In composite material applications, the gage length of the fiberis usually of the order of several fiber diameters, but it has been customaryto test fibers with a gage length of 25.4 10-3m. However
38、, other gagelengths can be used as long as they are practical, and in either case, thevalue of the gage length must be reported.9.1.2 When Using Tabs:9.1.2.1 A mounting tab (Fig. 3) may be used for specimenmounting. Center the test specimen over the tab using theprinted pattern with one end taped to
39、 the tab.9.1.2.2 Tape the opposite end of the test specimen to the tabexercising care to prevent fiber twisting. It has been found thatthe tensile strength of fibers decreases significantly withincreasing torsional strain (5).9.1.2.3 Carefully place a small amount of suitable adhesive(for example, e
40、poxy, red sealing wax) at the marks on themounting tab that define the gage length, and bond the fiber tothe mounting tab.9.1.2.4 Determine the gage length to the nearest 6 510-4mor61 % of the gage length, whichever is smaller.9.2 Optical Strain FlagsIf optical flags are to be used forstrain measure
41、ment, they may be attached directly to the fibersat this time, using a suitable adhesive or other attachmentmethod. Note that this may not be possible with small-diameterfibers ( 510-6m).9.3 Test Modes and RatesThe test shall be conductedunder a constant cross-head displacement rate. Rates of testin
42、gmust be sufficiently rapid to obtain the maximum possiblestrength at fracture within 30 s. The user may try as an initialvalue a test rate of810-6m/s. However, rates other thanthose recommended here may be used to evaluate rate effects.In all cases the test mode and rate must be reported.9.4 Ensure
43、 that the machine is calibrated and in equilibrium(no drift).9.5 Set the cross-head and data recorder speeds to provide atest time to specimen fracture within 30 s.9.6 Grasp a mounted test specimen in one of the two tabgrip areas (or pin load one end of the mounting tab). Zero theload cell.9.7 Posit
44、ion the cross-head so that the other tab grip areamay be grasped as in 9.6. Check the axial specimen alignmentusing whatever methods have been established, as described in7.1.2.9.8 If using tabs, with the mounting tab un-strained, cut bothsides of the tab very carefully at mid-gage as shown in Fig.
45、4.Alternatively, the sides of the tab can be burned using asoldering iron, for example. If the fiber is damaged, then itmust be discarded.9.9 Initiate the data recording followed by the operation ofthe test machine until fiber failure. Record both the cross-headdisplacement and force, and strain if
46、applicable.9.10 Recover the fracture surfaces and measure the cross-sectional area of a plane normal to the axis of the fiber at thefracture location or in the vicinity of the fracture location.Determine the fiber cross-sectional area using with a linearspatial resolution of 1.0 % of the fiber diame
47、ter or better, usinglaser diffraction techniques (8-11), or an image analysis systemin combination with a reflected light microscope or a scanningelectron microscope (12) (see Test Methods E1382). Note thatin practice, a reflected white light microscope can provide amaximum resolution of 0.5 10-6m a
48、nd therefore its use maybe impractical when measuring the cross-sectional area ofsmall diameter fibers. Because stiff fibers tend to shatter uponfailure, it is recommended to capture the fiber fragments usingvacuum grease, because vacuum grease is an effective mediumto dampen the energy released by
49、the fiber upon fracture. TheFIG. 3 Mounting TabC1557 03 (2013)4user of this standard should be aware that the need to recoverthe fracture surfaces of the fiber to determine the fibercross-sectional area is consistent with the need to do fractog-raphy to identify the strength-limiting flaws for the properestimation of the parameters of the distribution of fiberstrengths.NOTE 2The user of this standard test method must be aware that thediameter of many ceramic fibers varies not only among fibers in a bundle,but also along the
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