ASTM C1557-2003e1 Standard Test Method for Tensile Strength and Youngs Modulus of Fibers《纤维的抗拉强度及杨氏模量的标准试验方法》.pdf

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1、Designation: C 1557 03e1Standard Test Method forTensile Strength and Youngs Modulus of Fibers1This standard is issued under the fixed designation C 1557; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A

2、number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEFig. 3 was editorially corrected in June 2004.1. Scope1.1 This test method covers the preparation, mounting, andtesting of single fibers (ob

3、tained either from a fiber bundle ora spool) 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 This standard may involve hazardous materials, opera-tions, and equipment. This stand

4、ard 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 applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM

5、 Standards:2C 1239 Practice for Reporting Uniaxial Strength Data andEstimating Weibull Distribution Parameters for AdvancedCeramicsD 3878 Terminology of High-Modulus Reinforcing Fibersand their CompositesE 4 Practices for Load Verification of Testing MachinesE 6 Terminology Relating to Methods of Me

6、chanical Test-ingE 1382 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, compliantmetal, or plastic strip with a center hol

7、e 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 specimen-gripping system to the indicated cross

8、-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 D 3878 and E 6.4. Summary of Test Method4.1 A fiber is extracted randomly from a bundle or from aspool.4.2 The fiber is mounted in the testing machine, an

9、d 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-sectional area of a plane perpendicular toth

10、e 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 method are useful inthe evaluation of new fibers

11、 at the research and developmentlevels. Fibers with diameters up to 250 3 10-6m are coveredby this test method. Very short fibers (including whiskers) callfor specialized test techniques (1)3and are not covered by thistest method. This test method may also be useful in the initialscreening of candid

12、ate 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 fibers is controlled by one populationof flaws,

13、 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 of determining the parameters of thedistribu

14、tion of fiber strengths it is recommended to follow thistest method in conjunction with Practice C 1239.1This 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

15、April 10, 2003. Published August 2003.2For 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 website.3The boldface numbers i

16、n parentheses refer to the list of references at the end ofthis standard.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6. Interferences6.1 The test environment may have an influence on themeasured tensile strength of fibers. In par

17、ticular, the behaviorof fibers susceptible to slow crack growth fracture will bestrongly influenced by test environment and testing rate (4).Testing to evaluate the maximum strength potential of a fibershould be conducted in inert environments or at sufficientlyrapid testing rates, or both, so as to

18、 minimize slow crackgrowth effects. Conversely, testing can be conducted in envi-ronments and testing modes and rates representative of serviceconditions 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

19、 as stress concentrations, extraneousstresses introduced by gripping, or strength-limiting features inthe microstructure of the specimen. Such non-gage sectionfractures constitute invalid tests. When using active grippingsystems, insufficient pressure can lead to slippage, while toomuch pressure can

20、 cause local fracture in the gripping area.6.3 Torsional strains may reduce the magnitude of thetensile strength (5). Caution must be exercised when 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

21、length shouldbe avoided (4,6).7. Apparatus7.1 The apparatus described herein consists of a tensiletesting machine with one actuator (cross-head) that 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 Mach

22、ineThe testing machine shall be inconformance with Practice E 4. The failure forces shall beaccurate within 61 % at any force within the selected forcerange of the testing machine as defined in Practice E 4. Todetermine the appropriate capacity of the load cell, the follow-ing table lists the range

23、of strength and diameter values ofrepresentative glass, graphite, organic and ceramic fibers.7.1.2 GripsThe gripping system shall be of such designthat axial alignment of the fiber along the line of action of themachine shall be easily accomplished without damaging thetest specimen. Although studies

24、 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 action ofthe testing machine within d, to prevent spurious bendingstrains and/or stress concentrations:d #lo50(1)where:d = the tolerance, m, andlo= t

25、he 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 used, or none at all (that is, the fiber may bedirectly mounted into the grips). A simple but effectiveapproach for making mounting tabs with repeata

26、ble dimen-sions consists in printing the mounting tab pattern ontocardboard file folders using a laser printer.As illustrated in Fig.3, holes can be obtained using a three-hole punch. Fig. 3 showsa typical specimen mounting method. The mounting tabs aregripped or connected to the load train (for exa

27、mple, 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 using an activeset of grips without tabs, the grip facing material in contactwith the test specimen must be of appropriate compliance toallow for

28、 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 would lead to inaccurateresults. Large diameter fibers (diameter 50 3 10-6m) canalso be mounted inside hypodermic needles filled with anadhesive

29、(7). This is a good alternative to avoid crushing thefiber if pneumatic/hydraulic/mechanical grips were to be used.The adhesive must be sufficiently strong to withstand thegripping process, and prevent fiber “pull-out” during testing.FIG. 1 Typical Fiber TesterC155703e127.3 Data AcquisitionAt a mini

30、mum, autographic recordsof applied force and cross-head displacement versus time shallbe obtained. Either analog chart recorders or digital dataacquisition systems may be used for this purpose although adigital record is recommended for ease of later data analysis.Ideally, an analog chart recorder o

31、r plotter shall be used inconjunction with the digital data acquisition system to providean immediate record of the test as a supplement to the digitalrecord. 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 deem

32、ed more than sufficient.8. Precautionary Statement8.1 During the conduct of this test method, the possibility offlying fragments of broken fibers may be high. Means forcontaining these fragments for later fractographic reconstruc-tion and analysis is highly recommended. For example,vacuum grease has

33、 been used successfully to dampen the fiberduring failure and capture the fragments. In this case, vacuumgrease is applied in the gage section of the fiber so that theformer does not bear any force. An appropriate solvent can beused afterwards to remove the vacuum grease.9. Procedure9.1 Test Specime

34、n Mounting:9.1.1 Randomly choose, and carefully separate, a suitablesingle-fiber specimen from the bundle or fiber spool. The totallength of the specimen should be sufficiently long (at least 1.5times longer than the gage length) to allow for convenienthandling and gripping. Handle the test specimen

35、 at its ends andavoid touching it in the test gage length.NOTE 1Because the strength of fibers is statistical in nature, themagnitude of the strength will depend on the dimensions of the fiber beingFIG. 2TABLE 1 Room Temperature Tensile Strength of Fibers (25 310-3m Gage Length)Fiber Diameter, m Str

36、ength, PaCVD-SiC 50-150 3 10-62-3.5 3 109polymer-derived SiC 10-18 3 10-62-3.5 3 109sol-gel derived oxide 1-20 3 10-61-3 3 109single-crystal oxide 70-250 3 10-61.5-3.5 3 109graphite 1-15 3 10-61-6 3 109glass 1-250 x3 10-61-4 3 109aramid 12-20 3 10-62-4 3 109C155703e13evaluated. In composite material

37、 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 3 10-3m. However, other gagelengths can be used as long as they are practical, and in either case, thevalue of the gage length must be rep

38、orted.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 the tab.9.1.2.2 Tape the opposite end of the test specimen to the tabexercising care to prevent fiber twisting. It has be

39、en 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, epoxy, red sealing wax) at the marks on themounting tab that define the gage length, and bond the fiber tothe mounting tab.

40、9.1.2.4 Determine the gage length to the nearest 6 5 3 10-4mor61 % of the gage length, whichever is smaller.9.2 Optical Strain FlagsIf optical flags are to be used forstrain measurement, they may be attached directly to the fibersat this time, using a suitable adhesive or other attachmentmethod. Not

41、e that this may not be possible with small-diameterfibers (d 53 10-6m).9.3 Test Modes and RatesThe test shall be conductedunder a constant cross-head displacement rate. Rates of testingmust be sufficiently rapid to obtain the maximum possiblestrength at fracture within 30 s. The user may try as an i

42、nitialvalue a test rate of 8 3 10-6m/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 that the machine is calibrated and in equilibrium(no drift).9.5 Set the cross-head and data recorder speeds to

43、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 Position the cross-head so that the other tab grip areamay be grasped as in 9.6. Check the axial specimen alignmentus

44、ing 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. 4.Alternatively, the sides of the tab can be burned using asoldering iron, for example. If the fiber is damaged,

45、 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 applicable.9.10 Recover the fracture surfaces and measure the cross-sectional area of a plane normal to the axis

46、 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 diameter or better, usinglaser diffraction techniques (8-11), or an image analysis systemin combination with a reflec

47、ted light microscope or a scanningelectron microscope (12) (see Test Methods E 1382). Note thatin practice, a reflected white light microscope can provide amaximum resolution of 0.5 3 10-6m and therefore its use maybe impractical when measuring the cross-sectional area ofsmall diameter fibers. Becau

48、se 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 the fiber upon fracture. Theuser of this standard should be aware that the need to recoverthe fracture surfac

49、es 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 length of each fiber (13-16). It has been customary toFIG. 3 Mounting TabC155703e14determine individual fiber strength values using the average cross-sectional area of a group of fibers. Ho