1、Designation: D7337/D7337M 07 D7337/D7337M 12Standard Test Method forTensile Creep Rupture of Fiber Reinforced Polymer MatrixComposite Bars1This standard is issued under the fixed designation D7337/D7337M; the number immediately following the designation indicates theyear of original adoption or, in
2、the case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method outlines requirements for tensile creep rupture testing of fiber re
3、inforced polymer matrix (FRP) compositebars commonly used as tensile elements in reinforced, prestressed, or post-tensioned concrete.1.2 Data obtained from this test method are used in design of FRP reinforcements under sustained loading. The procedure forcalculating the one-million hour creep-ruptu
4、re capacity is provided in Annex A1.1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, theinch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system mustbe used indep
5、endently of the other. Combining values from the two systems may result in nonconformance with the standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety
6、and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning
7、 of Polymer Matrix CompositeMaterialsD7205/D7205M Test Method for Tensile Properties of Fiber Reinforced Polymer Matrix Composite BarsE4 Practices for Force Verification of Testing MachinesE456 Terminology Relating to Quality and StatisticsE1012 Practice for Verification of Testing Frame and Specime
8、n Alignment Under Tensile and Compressive Axial ForceApplication3. Terminology3.1 Terminology in D3878 defines terms relating to high-modulus fibers and their composites. Terminology in D883 definesterms relating to plastics. Terminology in E6 defines terms relating to mechanical testing. Terminolog
9、y in E456 defines termsrelating to statistics and the selection of sample sizes. In the event of a conflict between terms, Terminology in D3878 shall haveprecedence over the other terminology standards.3.2 Definitions of Terms Specific to This Standard:3.2.1 anchor, na protective device placed on ea
10、ch end of a bar, between the bar and the grips of the tensile testing apparatus,to prevent grip-induced damage. Usually used on bars with irregular surfaces, as opposed to flat strips where bonded tabs are moretypical.3.2.2 anchoring section, nthe end parts of the specimen where an anchor is fitted
11、to transmit the forces from the testingapparatus to the test section.1 This test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.10 on Compositesfor Civil Structures.Current edition approved Aug. 1, 2007Sept. 1, 2012.
12、 Published September 2007December 2012. Originally approved in 2007. Last previous edition approved in 2007 asD7337/D7337M 07. DOI: 10.1520/D7337_D7337M-07.10.1520/D7337_D7337M-12.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.o
13、rg. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This 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
14、 may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions 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 H
15、arbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.3 bar, na linear element, often with surface undulations or a coating of particles that promote mechanical interlock withconcrete.3.2.4 creep, ntime-dependent deformation (or strain) under sustained force (or stress).3.2.5
16、 creep rupture, nmaterial failure caused by sustained force (or stress) over time.3.2.6 creep rupture capacity, nthe force at which failure occurs after a specified period of time from initiation of a sustainedforce. The predicted force causing failure at 1 million hours is referred to as the millio
17、n-hour creep rupture capacity. This capacityis determined by the method described in the Annex.3.2.7 creep rupture strength, nthe stress causing failure after a specified period of time from initiation of a sustained force.3.2.8 creep rupture time, nthe lapsed time between the start of a sustained f
18、orce and failure of the test specimen.3.2.9 failure, nrupture of the bar under test into two separate pieces.3.2.10 force ratio, nthe ratio of a constant sustained force applied to a specimen to its tensile capacity as determined accordingto Test Method D7205/D7205M.3.2.11 grid, na two-dimensional (
19、planar) or three-dimensional (spatial) rigid array of interconnected FRP bars that form acontiguous lattice that can be used to reinforce concrete. The lattice can be manufactured with integrally connected bars orconstructed of mechanically connected individual bars. The grid bar elements have trans
20、verse dimensions typically greater than3 mm 0.12 in.3.2.12 nominal cross-sectional area, na measure of cross-sectional area of a bar, determined over at least one representativelength, used to calculate stress.3.2.13 representative length, nthe minimum length of a bar that contains a repeating geome
21、tric pattern that, placed end-to-end,reproduces the geometric pattern of a continuous bar (usually used in reference to bars having surface undulations for enhancinginterlock with concrete).3.2.14 surface undulation, nvariation in the area, orientation, or shape of cross-section of a bar along its l
22、ength, intended toenhance mechanical interlock between a bar and concrete, made by any of a number of processes such as, for example, indentation,addition of extra materials, and twisting.3.2.15 test section, nthe portion of a specimen between the anchoring sections of the test specimen.3.3 Symbols:
23、a1, b1 = empirical constantsA = nominal or standard cross-sectional area of a bar, see Test Method D7205/D7205MFr = stress carried by specimen at rupturePr = force carried by specimen at rupturet = time, hoursYc = creep rupture trend line4. Summary of Test Method4.1 This test method consists of meas
24、uring the time to rupture of a bar subjected to a constant tensile force. Multiple force levelsare specified by the method so that a relationship between force and time-to-failure can be derived.5. Significance and Use5.1 This method for investigating creep rupture of FRP bars is intended for use in
25、 laboratory tests in which the principal variableis the size or type of FRP bars, magnitude of applied force, and duration of force application. Unlike steel reinforcing bars orprestressing tendons subjected to significant sustained stress, creep rupture of FRP bars may take place below the static t
26、ensilestrength. Therefore, the creep rupture strength is an important factor when determining acceptable stress levels in FRP bars usedas reinforcement or tendons in concrete members designed to resist sustained loads. Creep rupture strength varies according to thetype of FRP bars used.5.2 This test
27、 method measures the creep rupture time of FRP bars under a given set of controlled environmental conditions andforce ratios.5.3 This test method is intended to determine the creep rupture data for material specifications, research and development,quality assurance, and structural design and analysi
28、s. The primary test result is the million-hour creep rupture capacity of thespecimen.5.4 Creep properties of reinforced, post-tensioned, or prestressed concrete structures are important to be considered in design.For FRP bars used as reinforcing bars or tendons, the creep rupture shall be measured a
29、ccording to the method given herein.D7337/D7337M 1226. Interferences6.1 GrippingThe method of gripping has been known to cause premature creep rupture in bars. Anchors, if used, shall bedesigned in such a way that the creep rupture capacity can be achieved without excessive slip throughout the lengt
30、h of the anchorduring the test.6.2 System AlignmentExcessive bending may cause premature failure. Every effort shall be made to eliminate bending fromthe test system. Bending may occur due to misalignment of the bar within anchors or grips or associated fixturing, or from thespecimen itself if impro
31、perly installed in the grips or if it is out-of-tolerance due to poor specimen preparation. See Practice E1012for verification of specimen alignment under tensile loading.6.3 Measurement of Cross-Sectional AreaThe nominal cross-sectional area of the bar is measured by immersing a prescribedlength of
32、 the specimen in water to determine its buoyant weight. Bar configurations that trap air during immersion (aside fromminor porosity) cannot be assessed using this method. This method may not be appropriate for bars that have large variations incross-sectional area along the length of the bar.6.4 Tes
33、t ConditionsCreep rupture is highly dependent upon environmental conditions such as, for example, temperature,humidity, and chemical agents. Every effort shall be made to test FRP bars for creep rupture under tightly controlled and monitoredconditions (see Sections 7, 10 and 11 for requirements).7.
34、Apparatus7.1 The testing apparatus shall be capable of applying and maintaining a force on the specimen within 61 % of the desiredsustained force.7.2 Test ApparatusUse a testing apparatus with a force capacity in excess of the tensile capacity of the specimen and calibratedaccording to Practices E4.
35、7.3 AnchorsAnchors, if used, shall be in accordance with Test Method D7205/D7205M.7.4 Temperature ControlThe temperature of the test environment shall be maintained at the specified temperature 62C64F during the test period. If no temperature is specified, maintain the temperature at 23C 73F.7.5 Env
36、ironmental Test ChamberAn environmental test chamber may be required for test environments other than ambienttesting laboratory conditions. For environments where temperature is specified, the chamber shall be capable of maintaining therequired temperature to within 62C 64F. In addition, the chamber
37、 may have to be capable of maintaining environmentalconditions such as fluid exposure or relative humidity during the test. For environments where relative humidity is specified, thechamber shall be capable of maintaining the required humidity to within 610 %RH.8. Sampling and Test Specimens8.1 Spec
38、imens shall be representative of the lot or batch being tested. For grid-type FRP specimens, linear test specimens maybe prepared by cutting away extraneous material in such a way as not to affect the performance of the part to be used. Leavinga minimum 2 mm 0.08 in. projection of the cross bars is
39、recommended. In the test section of the specimen, no postproductionmachining, abrading, or other such processing is permitted. Such processing may be used in the anchoring sections to promotebond of the rod to the anchoring device.8.2 During the sampling and preparation of test specimens, all deform
40、ation, heating, outdoor exposure to ultraviolet light, andother conditions possibly causing changes to the material properties of the specimen shall be avoided, unless these conditions arespecified as part of the test procedure.8.3 The length of the specimen shall be in accordance with Test Method D
41、7205/D7205M.8.4 The cross-sectional area of the specimen shall be determined in accordance with either of the two methods described in TestMethod D7205/D7205M: nominal area or standard area.8.5 If a specimen fails at or slips out of an anchoring section, an additional test shall be performed on a se
42、parate specimen takenfrom the same lot as the failed specimen.8.6 A100 mm 4 in. long specimen of the bar shall be used to determine the average moisture content of the as-received oras-conditioned bar before the start of creep rupture testing. The average moisture content shall be determined accordi
43、ng toProcedure D, section 3.2.2, of Test Method D5229/D5229M.8.7 A100 mm 4 in. long traveler specimen of the same cross-section geometry and appropriate size (but without anchors) shallbe used to determine the average moisture content of each bar after creep rupture testing. The ends of creep ruptur
44、e specimens andtraveler specimens shall be sealed with a water resistant sealant such as a high grade, room-temperature curing epoxy to avoid endeffects. The average moisture content shall be determined according to Procedure D, section 3.2.2, of Test MethodD5229/D5229M.D7337/D7337M 1239. Test Matri
45、x9.1 The quasi-static tensile strength of the bars as determined by Test Method D7205/D7205M is used as a basis for selectingthe applied tensile forces for creep rupture tests. At each given force ratiofor example, 80 %, 70 %, 60 % of the tensilestrengththe applied force must be maintained constant
46、until failure occurs while the time elapsed to rupture of each test specimenis recorded.NOTE 1The selection of force ratios is dependent on the fiber architecture and fiber volume fraction for the bar. Material systems with a highresistance to creep rupture (for example, carbon FRP composite) will n
47、ecessitate the selection of closely-spaced force ratios at stress levels approaching100 % of the quasi-static tensile strength. Material systems with less resistance to creep rupture (for example, glass FRP composite) will necessitate theselection of widely-spaced force ratios.9.2 A minimum of four
48、force ratios are required (see Fig. A1.1 for example). A minimum of 5 valid test results are requiredfor each force ratio. For the entire group of tests reported, the range between the longest and shortest recorded rupture times shallbe at least three decades. Data from specimens that break before t
49、he applied tensile force is fully applied to the specimen shall bedisregarded.NOTE 2It is suggested that additional specimens be tested at each force ratio, especially for those force ratios that require long times to rupture.9.2.1 The highest force ratio shall be selected such that at least four specimens in this group ruptures at a time of greater than1 h.NOTE 3The highest force is specified with the aim of minimizing the effects of the initial loading ramp on the creep rupture time.9.2.2 The lowest force ratio shall be selected
