ASTM C1557-2014 Standard Test Method for Tensile Strength and Young&rsquo s Modulus of Fibers《纤维抗拉强度和扬氏模量的标准试验方法》.pdf

1、Designation: C1557 03 (Reapproved 2013)C1557 14Standard 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 yea

2、r 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 covers the preparation, mounting, and testing of single fibers (obtained either from a fiber bun

3、dle or aspool) for the determination of tensile strength andYoungs modulus at ambient temperature.Advanced ceramic, glass, carbon andother fibers are covered by this test standard.1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this sta

4、ndard.1.3 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address allof the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriatesafety and health practices and dete

5、rmine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C1239 Practice for Reporting Uniaxial Strength Data and Estimating Weibull Distribution Parameters for Advanced CeramicsD3878 Terminology for Composite MaterialsE4 Practices for Force Verificati

6、on of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE1382 Test Methods for Determining Average Grain Size Using 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,

7、cardboard, compliant metal, or plastic strip with a center hole or longitudinal slot of fixed gagelength. The mounting tab should be appropriately designed to be self-aligning if possible, and as thin as practicable to minimizefiber misalignment.3.1.3 system compliancethe contribution by the load tr

8、ain system and specimen-gripping system to the indicated cross-headdisplacement, 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 fro

9、m a spool.4.2 The fiber is mounted in the testing machine, and then stressed to failure at a constant cross-head displacement rate.4.3 A valid test result is considered to be one in which fiber failure doesnt occur in the gripping region.4.4 Tensile strength is calculated from the ratio of the peak

10、force and the cross-sectional area of a plane perpendicular to thefiber axis, at the fracture location or in the vicinity of the fracture location, while Youngs modulus is determined from the linearregion of the tensile stress versus tensile strain curve.1 This test method is under the jurisdiction

11、of ASTM Committee C28 on Advanced Ceramics and is the direct responsibility of Subcommittee C28.07 on Ceramic MatrixComposites.Current edition approved Aug. 1, 2013Aug. 15, 2014. Published September 2013October 2014. Originally approved in 2003. Last previous edition approved in 20082013as C1557 03

12、(2008).(2013). DOI: 10.1520/C1557-03R13.10.1520/C1557-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This

13、 document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior edition

14、s as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Significance and Use5.1 Properties determined by

15、this test method are useful in the evaluation of new fibers at the research and development levels.Fibers with diameters up to 250 10-6 m are covered by this test method. Very short fibers (including whiskers) call for specializedtest techniques (1)3 and are not covered by this test method.This test

16、 method may also be useful in the initial screening of candidatefibers for applications in polymer, metal or ceramic matrix composites, and quality control purposes. Because of their nature,ceramic fibers do not have a unique strength, but rather, a distribution of strengths. In most cases when the

17、strength of the fibersis controlled by one population of flaws, the distribution of fiber strengths can be described using a two-parameter Weibulldistribution, although other distributions have also been suggested (2,3). This test method constitutes a methodology to obtain thestrength of a single fi

18、ber. For the purpose of determining the parameters of the distribution of fiber strengths it is recommendedto follow this test method in conjunction with Practice C1239.6. Interferences6.1 The test environment may have an influence on the measured tensile strength of fibers. In particular, the behav

19、ior of fiberssusceptible to slow crack growth fracture will be strongly influenced by test environment and testing rate (4). Testing to evaluatethe maximum strength potential of a fiber should be conducted in inert environments or at sufficiently rapid testing rates, or both,so as to minimize slow c

20、rack growth effects. Conversely, testing can be conducted in environments and testing modes and ratesrepresentative of service conditions to evaluate the strength of fibers under those conditions.6.2 Fractures that initiate outside the gage section of a fiber may be due to factors such as stress con

21、centrations, extraneousstresses introduced by gripping, or strength-limiting features in the microstructure of the specimen. Such non-gage section fracturesconstitute invalid tests. When using active gripping systems, insufficient pressure can lead to slippage, while too much pressurecan cause local

22、 fracture in the gripping area.6.3 Torsional strains may reduce the magnitude of the tensile strength (5). Caution must be exercised when mounting the fibersto avoid twisting the fibers.6.4 Many fibers are very sensitive to surface damage. Therefore, any contact with the fiber in the gage length sho

23、uld be avoided(4,6).7. Apparatus7.1 The apparatus described herein consists of a tensile testing machine with one actuator (cross-head) that operates in acontrollable 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 t

24、esting machine shall be in conformance with Practice E4. The failure forces shall be accuratewithin 61 % at any force within the selected force range of the testing machine as defined in Practice E4. To determine theappropriate capacity of the load cell, the following table lists the range of streng

25、th and diameter values of representative glass,graphite, organic and ceramic fibers.3 The boldface numbers in parentheses refer to the list of references at the end of this standard.FIG. 1 Typical Fiber TesterC1557 1427.1.2 GripsThe gripping system shall be of such design that axial alignment of the

26、 fiber along the line of action of the machineshall be easily accomplished without damaging the test specimen.Although studies of the effect of fiber misalignment on the tensilestrength of fibers have not been reported, the axis of the fiber shall be coaxial with the line of action of the testing ma

27、chine within, to prevent spurious bending strains and/or stress concentrations:# lo50where: = the tolerance, m, andlo = the fiber gage length, m.FIG. 2 Schematic of Fiber Tensile Testing MachineTABLE 1 Room Temperature Tensile Strength of Fibers (25 10-3m Gage Length)Fiber Diameter, m Strength, PaCV

28、D-SiC 50-150 10-6 2-3.5 109polymer-derived SiC 10-18 10-6 2-3.5 109sol-gel derived oxide 1-20 10-6 1-3 109single-crystal oxide 70-250 10-6 1.5-3.5 109graphite 1-15 10-6 1-6 109glass 1-250 x 10-6 1-4 109aramid 12-20 10-6 2-4 109C1557 1437.2 Mounting TabsTypical mounting tabs for test specimens are sh

29、own in Fig. 3. Alternative methods of specimen mountingmay be used, or none at all (that is, the fiber may be directly mounted into the grips). A simple but effective approach for makingmounting tabs with repeatable dimensions consists in printing the mounting tab pattern onto cardboard file folders

30、 using using, forexample, a laser printer. As illustrated in Fig. 3, holes can be obtained using a three-hole punch. Fig. 3 shows a typical specimenmounting method. The mounting tabs are gripped or connected to the load train (for example, by pin and clevis) so that the testspecimen is aligned axial

31、ly along the line of action of the test machine.7.2.1 When gripping large diameter fibers using an active set of grips without tabs, the grip facing material in contact with thetest specimen must be of appropriate compliance to allow for a firm, non-slipping grip on the fiber.At the same time, the g

32、rip facingmaterial must prevent crushing, scoring or other damage to the test specimen that would lead to inaccurate results. Large diameterfibers (diameter 50 10-6 m) can also be mounted inside hypodermic needles filled with an adhesive (7). This is a goodalternative to avoid crushing the fiber if

33、pneumatic/hydraulic/mechanical grips were to be used. The adhesive must be sufficientlystrong to withstand the gripping process, and prevent fiber “pull-out” during testing.7.3 Data AcquisitionAt a minimum, autographic records of applied force and cross-head displacement versus time shall beobtained

34、. Either analog chart recorders or digital data acquisition systems may be used for this purpose although a digital recordis recommended for ease of later data analysis. Ideally, an analog chart recorder or plotter shall be used in conjunction with thedigital data acquisition system to provide an im

35、mediate record of the test as a supplement to the digital record. Recording devicesmust be accurate to 6 1 % of full scale and shall have a minimum data acquisition rate of 10 Hz with a response of 50 Hz deemedmore than sufficient.8. Precautionary Statement8.1 During the conduct of this test method,

36、 the possibility of flying fragments of broken fibers may be high. Means forcontaining these fragments for later fractographic reconstruction and analysis is highly recommended. For example, vacuum greasehas been used successfully to dampen the fiber during failure and capture the fragments. In this

37、 case, vacuum grease is appliedin the gage section of the fiber so that the former does not bear any force.An appropriate solvent can be used afterwards to removethe vacuum grease.9. Procedure9.1 Test Specimen Mounting:9.1.1 Randomly choose, and carefully separate, a suitable single-fiber specimen f

38、rom the bundle or fiber spool. The total lengthof the specimen should be sufficiently long (at least 1.5 times longer than the gage length) to allow for convenient handling andgripping. Handle the test specimen at its ends and avoid touching it in the test gage length.NOTE 1Because the strength of f

39、ibers is statistical in nature, the magnitude of the strength will depend on the dimensions of the fiber being evaluated.In composite material applications, the gage length of the fiber is usually of the order of several fiber diameters, but it has been customary to test fiberswith a gage length of

40、25.4 10-3 m. However, other gage lengths can be used as long as they are practical, and in either case, the value of the gage lengthmust be reported.9.1.2 When Using Tabs:9.1.2.1 A mounting tab (Fig. 3) may be used for specimen mounting. Center the test specimen over the tab using the printedpattern

41、 with one end taped to the tab.FIG. 3 Mounting TabC1557 1449.1.2.2 Tape the opposite end of the test specimen to the tab exercising care to prevent fiber twisting. It has been found that thetensile strength of fibers decreases significantly with increasing torsional strain (5).9.1.2.3 Carefully plac

42、e a small amount of suitable adhesive (for example, epoxy, red sealing wax) at the marks on the mountingtab that define the gage length, and bond the fiber to the mounting tab.9.1.2.4 Determine the gage length to the nearest 6 5 10-4 m or 61 % of the gage length, whichever is smaller.9.2 Optical Str

43、ain FlagsIf optical flags are to be used for strain measurement, they may be attached directly to the fibers atthis time, using a suitable adhesive or other attachment method. Note that this may not be possible with small-diameter fibers (d 5 10-6 m).9.3 Test Modes and RatesThe test shall be conduct

44、ed under a constant cross-head displacement rate. Rates of testing must besufficiently rapid to obtain the maximum possible strength at fracture within 30 s. The user may try as an initial value a test rateof 8 10-6 m/s. However, rates other than those recommended here may be used to evaluate rate e

45、ffects. In all cases the test modeand 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 provide a test time to specimen fracture within 30 s.9.6 Grasp a mounted test specimen in one of the two tab grip are

46、as (or pin load one end of the mounting tab). Zero the loadcell.9.7 Position the cross-head so that the other tab grip area may be grasped as in 9.6. Check the axial specimen alignment usingwhatever methods have been established, as described in 7.1.2.9.8 If using tabs, with the mounting tab un-stra

47、ined, cut both sides of the tab very carefully at mid-gage as shown in Fig. 4.Alternatively, the sides of the tab can be burned using a soldering iron, for example. If the fiber is damaged, then it must bediscarded.9.9 Initiate the data recording followed by the operation of the test machine until f

48、iber 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 of the fiber at the fracturelocation or in the vicinity of the fracture location. Determine the fiber cross-s

49、ectional area using with a linear spatial resolutionof 1.0 % of the fiber diameter or better, using laser diffraction techniques (8-11), or an image analysis system in combination witha reflected light microscope or a scanning electron microscope (12) (see Test Methods E1382). Note that in practice, a reflectedwhite light microscope can provide a maximum resolution of 0.5 10-6 m and therefore its use may be impractical when measuringthe cross-sectional area of small diameter fibers. Because stiff fibers tend to shat