ASTM D7291 D7291M-2015 red 8507 Standard Test Method for Through-Thickness &x201c Flatwise&x201d Tensile Strength and Elastic Modulus of a Fiber-Reinforced Polymer Matrix Composite.pdf

1、Designation: D7291/D7291M 07D7291/D7291M 15Standard Test Method forThrough-Thickness “Flatwise” Tensile Strength and ElasticModulus of a Fiber-Reinforced Polymer Matrix CompositeMaterial1This standard is issued under the fixed designation D7291/D7291M; the number immediately following the designatio

2、n indicates theyear of original adoption or, in 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 determines the thro

3、ugh-thickness “flatwise” tension strength and elastic modulus of fiber reinforcedpolymer matrix composite materials. A tensile force is applied normal to the plane of the composite laminate using adhesivelybonded thick metal end-tabs. The composite material forms are limited to continuous-fiber or d

4、iscontinuous fiber (tape or2-dimensional fabric, or both) reinforced composites.1.2 The through-thickness strength results using this test method will in general not be comparable to Test Method D6415 sincethis method subjects a relatively large volume of material to an almost uniform stress field w

5、hile Test Method D6415 subjects asmall volume of material to a non-uniform stress field.1.3 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices

6、 and determine the applicability of regulatorylimitations prior to use.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; there

7、fore, each system mustbe used independently 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 problems, if any, associated with its use. It is the responsibilityof the user of this standa

8、rd to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D792 Test Methods for Density and Specific Gravity (Relative Density) of Plastics by DisplacementD883 Terminology Relating to Plast

9、icsD3171 Test Methods for Constituent Content of Composite MaterialsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix CompositeMaterialsD5687/D5687M Guide for Preparation of Flat Composite Panels with P

10、rocessing Guidelines for Specimen PreparationD6415 Test Method for Measuring the Curved Beam Strength of a Fiber-Reinforced Polymer-Matrix CompositeE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE122 Practice for Calculating Sample Size

11、 to Estimate, With Specified Precision, the Average for a Characteristic of a Lot orProcessE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE251 Test Methods for Performance Characteristics of Metallic Bonded Resistance Strain GagesE456 Terminology Relating to Quality and St

12、atistics1 This test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.06 on InterlaminarProperties.Current edition approved April 1, 2007Oct. 1, 2015. Published May 2007November 2015. Originally approved in 2007. Last p

13、revious edition approved in 2007 asD7291/D7291M-07. DOI: 10.1520/D7291_D7291M-07.10.1520/D7291_D7291M-15.2 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 standard

14、s 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 may not be technically possible to adequately depict all changes accurately,

15、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 Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E691

16、 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodE1012 Practice for Verification of Testing Frame and Specimen Alignment Under Tensile and Compressive Axial ForceApplicationE1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materia

17、ls in Databases (Withdrawn 2015)3E1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases (Withdrawn 2015)3E1471 Guide for Identification of Fibers, Fillers, and Core Materials in Computerized Material Property Databases (Withdrawn2015)33. Terminology3.1 De

18、finitionsTerminology D3878 defines terms relating to high-modulus fibers and their composites. Terminology D883defines terms relating to plastics. Terminology E6 defines terms relating to mechanical testing. Terminology E456 and PracticeE177 define terms relating to statistics. In the event of a con

19、flict between terms, Terminology D3878 shall have precedence overthe other terminologies.NOTE 1If the term represents a physical quantity, its analytical dimensions are stated immediately following the term (or letter symbol) infundamental dimension form, using the following ASTM standard symbology

20、for fundamental dimensions, shown within square brackets: M for mass,L for length, T for time, for thermodynamic temperature, and nd for non-dimensional quantities. Use of these symbols is restricted to analyticaldimensions when used with square brackets, as the symbols may have other definitions wh

21、en used without the brackets.3.2 Definitions of Terms Specific to This Standard:3.2.1 flatwise tensile ultimate strength, F tu M L1 T2 , nthe ultimate strength of the composite material in the out-of-plane(through-thickness) direction.3.2.2 through-thickness tensile modulus, E chord M L1 T2 , nthe c

22、hord modulus of elasticity of the composite material inthe out-of-plane (through-thickness) direction.3.3 Symbols:3.3.1 Across-sectional area of specimen in the through-thickness direction,3.3.2 CVcoefficient of variation statistic of a sample population for a given property (in percent),3.3.3 Echor

23、d through-thickness tensile modulus.3.3.4 Ftu flatwise tensile ultimate strength.3.3.5 nnumber of specimens.3.3.6 Pmax maximum force carried by test specimen before failure.3.3.7 sn1sample standard deviation.3.3.8 xi measured or derived property for an individual specimen from the sample population.

24、3.3.9 xsample mean (average).3.3.10 indicated through-thickness tensile strain from strain transducer.3.3.11 through-thickness tensile stress.4. Summary of Test Method4.1 A composite specimen in the shape of either a straight-sided cylindrical disk or a reduced gage section cylindrical “spool”is adh

25、esively bonded to cylindrical metal end tabs. The bonded assembly is loaded under “flatwise” tension loading by a forceapplied normal to the plane of the composite laminate until failure of the laminate occurs (Fig. 1). The test is considered valid onlywhen failure occurs entirely within the composi

26、te laminate. The test is considered invalid if failure of the bond-line or partialfailure of the bond-line and the surface layer of the composite occurs. The failure mode of this test is not controlled; therefore,the actual failure may be intralaminar or interlaminar in nature.4.2 If force-strain da

27、ta are required, the specimen may be instrumented with strain gages provided certain specimen thicknessrequirements are satisfied (see 8.2).5. Significance and Use5.1 This test method is designed to produce through-thickness failure data for structural design and analysis, quality assurance,and rese

28、arch and development. Factors that influence the through-thickness tensile strength, and should therefore be reported,include the following: material and fabric reinforcement, methods of material and fabric preparation, methods of processing andspecimen fabrication, specimen stacking sequence, speci

29、men conditioning, environment of testing, specimen alignment, speed oftesting, time at temperature, void content, and volume reinforcement content.3 The last approved version of this historical standard is referenced on www.astm.org.D7291/D7291M 1526. Interferences6.1 Material and Specimen Preparati

30、onPoor material fabrication practices, lack of control of fiber alignment, voids, anddamage induced by improper specimen machining are known causes of high material data scatter in composites in general. Inaddition, surface finish of the cylindrical machined surface and lack of control of parallelis

31、m of laminate surfaces can lead toerroneous through-thickness strength results. Laminate stacking sequences that are not balanced and symmetric could lead toadhesive bondline failures.6.2 Material with Coarse StructureThis test method assumes that the material is relatively homogeneous with respect

32、to thesize of the test section. Certain fabric and braided composites with large repeating unit cell sizes (12 mm 0.5 in.) should notbe tested with this specimen size. It may be possible to scale-up the specimen size and fixtures to accommodate such materials,but this is beyond the scope of this tes

33、t method.6.3 Load EccentricityBending of the specimen during loading can occur, affecting strength results. Bending may occur dueto poor specimen preparation, non-parallel laminate surfaces, improper bonding of the specimen to the end tabs, or machine/loadtrain misalignment.6.4 Void contentThe throu

34、gh-thickness tension strength measured using this method is extremely sensitive to reinforcementvolume and void content. Consequently, the test results may reflect manufacturing quality as much as material properties.7. Apparatus7.1 MicrometersThe micrometer(s) shall use a 4 to 6 mm 0.16 to 0.25 in.

35、 diameter ball-interface on irregular surfaces suchas the bag-side of a laminate, and a flat anvil interface on machined or very-smooth tooled surfaces. The accuracy of theinstrument(s) shall be suitable for reading to within 1 % of the sample diameter and thickness. For typical specimen geometriesa

36、n instrument with an accuracy of 625 m 60.001 in. is desirable for both diameter and thickness measurements.7.2 FixturesThe apparatus consists of three different fixtures.7.2.1 The loading fixtures are used to load the specimen and end tab assembly. They can be either self-aligning or fixed gripand

37、shall not apply eccentric loads.7.2.2 The end tabs are bonded to the specimen (Figs. 2 and 3). The end tabs are attached to the loading fixture during the test.The threads on the end tabs provide a means to attach the specimen and end tab assembly to the loading fixture. They also providea means to

38、attach constant diameter bushings for the purpose of aligning the specimen and end tab assembly in the bonding fixture.The end tab thickness shall be a minimum of 12.7 mm 0.5 in. Section 8.3 provides further requirements for the end tabs.7.2.3 The end tab bonding fixture (Figs. 4-6) is used to provi

39、de support and alignment to the specimen and end tab assemblyduring the entire bonding process. The threads on the end tabs are used to attach bushings to them during the bonding process.These bushings provide a fixed diameter reference surface for aligning the specimen and end tab assembly during b

40、onding, thusallowing the resuse and re-machining of the end tabs.7.3 Testing MachineThe testing machine shall conform with Practice E4, and shall satisfy these requirements:7.3.1 Testing Machine HeadsThe testing machine shall have two crossheads, with either a stationary head and a movable heador tw

41、o movable heads.FIG. 1 Flatwise Tension Specimen and End Tab AssemblyD7291/D7291M 1537.3.2 Platens/AdapterOne of the testing machine heads shall be capable of being attached to the lower half of the specimenend tab by an adapter or platen interface as required. The other head shall be capable of bei

42、ng attached to the upper half of thespecimen end tab.7.3.3 Drive MechanismThe testing machine drive mechanism shall be capable of imparting to the movable head a controlledvelocity with respect to the stationary head. The velocity of the movable head shall be capable of regulation as specified in 11

43、.3.7.3.4 Force IndicatorThe testing machine force-sensing device shall be capable of indicating the total force applied to the testspecimen. This device shall be essentially free from response lag at the specified testing rate and shall indicate the force with anaccuracy over the load range(s) of in

44、terest of within 61 % of the indicated value, as specified by Practice E4. The load range(s)of interest may be fairly low for modulus evaluation, much higher for strength evaluation, or both, as required.7.4 Force versus Displacement RecordAn X-Y plotter, or similar device, shall be used to make a p

45、ermanent record of theforce versus displacement during the test. Alternatively, the data may be stored digitally and post-processed.FIG. 2 Drawing of End Tabs and Cylindrical Specimen Assembly (SI units)FIG. 3 Drawing of End Tabs and Cylindrical Specimen Assembly (inch-pound units)D7291/D7291M 1547.

46、5 Strain-Indicating DeviceFor the measurement of through-thickness modulus, bonded resistance strain gages shall be usedto measure strain. Either two strain gages at locations that are 180 degrees apart or three strain gages at 120 degrees apart arerequired around the cylindrical surface of the spec

47、imen at the center of the gage section.7.5.1 Bonded Resistance Strain GagesStrain gage selection is a compromise based on the type of material. An active gagelength of 1.5 mm 0.062 in. is recommended for most materials although larger gages may be more suitable for some wovenfabrics (with consolidat

48、ed tow thicknesses larger than 1.5 mm 0.062 in.), provided the specimen gage length can accommodatesuch gages (as specified in 8.2). Gage calibration certification shall comply with Test Method E251. For laminated composites, thestrain gage should cover a minimum of three laminate plies.7.6 System A

49、lignmentPoor system alignment can be a major contributor to premature failure, to elastic property data scatter,or both. Practice E1012 describes bending evaluation guidelines and describes potential sources of misalignment during tensiletesting. Alignment should be checked using a cylindrical metal specimen with a minimum of three strain gages equally spacedaround the circumference per Practice E1012. While the maximum advisable amount of system misalignment is material andlocation dependent, good testing pra