1、Designation: D 7291/D 7291M 07Standard Test Method forThrough-Thickness “Flatwise” Tensile Strength and ElasticModulus of a Fiber-Reinforced Polymer Matrix CompositeMaterial1This standard is issued under the fixed designation D 7291/D 7291M; the number immediately following the designation indicates
2、 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method determines the through-thickn
3、ess “flat-wise” tension strength and elastic modulus of fiber reinforcedpolymer matrix composite materials. A tensile force is appliednormal to the plane of the composite laminate using adhesivelybonded thick metal end-tabs. The composite material forms arelimited to continuous-fiber or discontinuou
4、s fiber (tape or2-dimensional fabric, or both) reinforced composites.1.2 The through-thickness strength results using this testmethod will in general not be comparable to Test MethodD 6415 since this method subjects a relatively large volume ofmaterial to an almost uniform stress field while Test Me
5、thodD 6415 subjects a small volume of material to a non-uniformstress field.1.3 This standard does not purport to address all of thesafety problems, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determi
6、ne the applica-bility of regulatory limitations prior to use.1.4 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. Within the text, theinch-pound units are shown in brackets. The values stated ineach system are not exact equivalents; therefore, each s
7、ystemmust be used independently of the other. Combining valuesfrom the two systems may result in nonconformance with thestandard.2. Referenced Documents2.1 ASTM Standards:2D 792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics by DisplacementD 883 Terminology Relating to
8、 PlasticsD 3171 Test Methods for Constituent Content of CompositeMaterialsD 3878 Terminology for Composite MaterialsD 5229/D 5229M Test Method for Moisture AbsorptionProperties and Equilibrium Conditioning of Polymer Ma-trix Composite MaterialsD 5687/D 5687M Guide for Preparation of Flat CompositePa
9、nels with Processing Guidelines for Specimen Prepara-tionD 6415 Test Method for Measuring the Curved BeamStrength of a Fiber-Reinforced Polymer-Matrix CompositeE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical Test-ingE 122 Practice for Calculati
10、ng Sample Size to Estimate,With a Specified Tolerable Error, the Average for aCharacteristic of a Lot or ProcessE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 251 Test Methods for Performance Characteristics ofMetallic Bonded Resistance Strain GagesE 456 Terminology Rela
11、ting to Quality and StatisticsE 1012 Practice for Verification of Test Frame and Speci-men Alignment Under Tensile and Compressive AxialForce ApplicationE 1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in DatabasesE 1434 Guide for Recording Mechanical Test Data o
12、f Fiber-Reinforced Composite Materials in DatabasesE 1471 Guide for Identification of Fibers, Fillers, and CoreMaterials in Computerized Material Property Databases3. Terminology3.1 DefinitionsTerminology D 3878 defines terms relatingto high-modulus fibers and their composites. TerminologyD 883 defi
13、nes terms relating to plastics. Terminology E6defines terms relating to mechanical testing. TerminologyE 456 and Practice E 177 define terms relating to statistics. Inthe event of a conflict between terms, Terminology D 3878shall have precedence over the other terminologies.NOTE 1If the term represe
14、nts a physical quantity, its analyticaldimensions are stated immediately following the term (or letter symbol) infundamental dimension form, using the following ASTM standard sym-bology for fundamental dimensions, shown within square brackets: M1This test method is under the jurisdiction of ASTM Com
15、mittee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.06 onInterlaminar Properties.Current edition approved April 1, 2007. Published May 2007.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For
16、Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.for mass, L for length, T for time, Q for thermodynamic temperature,and
17、nd for non-dimensional quantities. Use of these symbols is restrictedto analytical dimensions when used with square brackets, as the symbolsmay have other definitions when used without the brackets.3.2 Definitions of Terms Specific to This Standard:3.2.1 flatwise tensile ultimate strength, FtuML1T2,
18、nthe ultimate strength of the composite material in theout-of-plane (through-thickness) direction.3.2.2 through-thickness tensile modulus, EchordML1T2,nthe chord modulus of elasticity of the composite material inthe out-of-plane (through-thickness) direction.3.3 Symbols:3.3.1 Across-sectional area o
19、f specimen in the through-thickness direction,3.3.2 CVcoefficient of variation statistic of a samplepopulation for a given property (in percent),3.3.3 Echordthrough-thickness tensile modulus.3.3.4 Ftuflatwise tensile ultimate strength.3.3.5 nnumber of specimens.3.3.6 Pmaxmaximum force carried by tes
20、t specimen be-fore failure.3.3.7 sn1sample standard deviation.3.3.8 ximeasured or derived property for an individualspecimen from the sample population.3.3.9 xsample mean (average).3.3.10 eindicated through-thickness tensile strain fromstrain transducer.3.3.11 sthrough-thickness tensile stress.4. Su
21、mmary 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 adhesively bonded to cylindrical metal end tabs. Thebonded assembly is loaded under “flatwise” tension loading bya force applied normal to the plane o
22、f the composite laminateuntil failure of the laminate occurs (Fig. 1). The test isconsidered valid only when failure occurs entirely within thecomposite laminate. The test is considered invalid if failure ofthe bond-line or partial failure of the bond-line and the surfacelayer of the composite occur
23、s. The failure mode of this test isnot controlled; therefore, the actual failure may be intralaminaror interlaminar in nature.4.2 If force-strain data are required, the specimen may beinstrumented with strain gages provided certain specimenthickness requirements are satisfied (see 8.2).5. Significan
24、ce and Use5.1 This test method is designed to produce through-thickness failure data for structural design and analysis, qualityassurance, and research and development. Factors that influ-ence the through-thickness tensile strength, and should there-fore be reported, include the following: material
25、and fabricreinforcement, methods of material and fabric preparation,methods of processing and specimen fabrication, specimenstacking sequence, specimen conditioning, environment oftesting, specimen alignment, speed of testing, time at tempera-ture, void content, and volume reinforcement content.6. I
26、nterferences6.1 Material and Specimen PreparationPoor materialfabrication practices, lack of control of fiber alignment, voids,and damage induced by improper specimen machining areknown causes of high material data scatter in composites ingeneral. In addition, surface finish of the cylindrical machi
27、nedsurface and lack of control of parallelism of laminate surfacescan lead to erroneous through-thickness strength results. Lami-nate stacking sequences that are not balanced and symmetriccould lead to adhesive bondline failures.6.2 Material with Coarse StructureThis test method as-sumes that the ma
28、terial is relatively homogeneous with respectto the size of the test section. Certain fabric and braidedcomposites with large repeating unit cell sizes (12 mm 0.5in.) should not be tested with this specimen size. It may bepossible to scale-up the specimen size and fixtures to accom-modate such mater
29、ials, but this is beyond the scope of this testmethod.6.3 Load EccentricityBending of the specimen duringloading can occur, affecting strength results. Bending mayFIG. 1 Flatwise Tension Specimen and End Tab AssemblyD 7291/D 7291M 072occur due to poor specimen preparation, non-parallel laminatesurfa
30、ces, improper bonding of the specimen to the end tabs, ormachine/load train misalignment.6.4 Void contentThe through-thickness tension strengthmeasured using this method is extremely sensitive to reinforce-ment volume and void content. Consequently, the test resultsmay reflect manufacturing quality
31、as much as material prop-erties.7. Apparatus7.1 MicrometersThe micrometer(s) shall usea4to6mm0.16 to 0.25 in. diameter ball-interface on irregular surfacessuch as the bag-side of a laminate, and a flat anvil interface onmachined or very-smooth tooled surfaces. The accuracy of theinstrument(s) shall
32、be suitable for reading to within 1 % of thesample diameter and thickness. For typical specimen geom-etries an 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 fix-tures.7.2.1 The loading fi
33、xtures are used to load the specimen andend tab assembly. They can be either self-aligning or fixed gripand shall not apply eccentric loads.7.2.2 The end tabs are bonded to the specimen (Figs. 2 and3). The end tabs are attached to the loading fixture during thetest. The threads on the end tabs provi
34、de a means to attach thespecimen and end tab assembly to the loading fixture. Theyalso provide a means to attach constant diameter bushings forthe purpose of aligning the specimen and end tab assembly inthe bonding fixture. The end tab thickness shall be a minimumof 12.7 mm 0.5 in. Section 8.3 provi
35、des further requirementsfor the end tabs.7.2.3 The end tab bonding fixture (Figs. 4-6) is used toprovide support and alignment to the specimen and end tabassembly during the entire bonding process. The threads on theend tabs are used to attach bushings to them during the bondingprocess. These bushin
36、gs provide a fixed diameter referencesurface for aligning the specimen and end tab assembly duringbonding, thus allowing the resuse and re-machining of the endtabs.7.3 Testing MachineThe testing machine shall conformwith Practice E4, and shall satisfy these requirements:7.3.1 Testing Machine HeadsTh
37、e testing machine shallhave two crossheads, with either a stationary head and amovable head or two movable heads.7.3.2 Platens/AdapterOne of the testing machine headsshall be capable of being attached to the lower half of thespecimen end tab by an adapter or platen interface as required.The other he
38、ad shall be capable of being attached to the upperhalf of the specimen end tab.7.3.3 Drive MechanismThe testing machine drive mecha-nism shall be capable of imparting to the movable head acontrolled velocity with respect to the stationary head. Thevelocity of the movable head shall be capable of reg
39、ulation asspecified in 11.3.7.3.4 Force IndicatorThe testing machine force-sensingdevice shall be capable of indicating the total force applied tothe test specimen. This device shall be essentially free fromresponse lag at the specified testing rate and shall indicate theforce with an accuracy over
40、the load range(s) of interest ofwithin 61 % of the indicated value, as specified by PracticeE4. The load range(s) of interest may be fairly low formodulus evaluation, much higher for strength evaluation, orboth, as required.7.4 Force versus Displacement RecordAn X-Y plotter, orsimilar device, shall
41、be used to make a permanent record of theforce versus displacement during the test. Alternatively, thedata may be stored digitally and post-processed.FIG. 2 Drawing of End Tabs and Cylindrical Specimen Assembly (SI units)D 7291/D 7291M 0737.5 Strain-Indicating DeviceFor the measurement ofthrough-thi
42、ckness modulus, bonded resistance strain gagesshall be used to measure strain. Either two strain gages atlocations that are 180 degrees apart or three strain gages at 120degrees apart are required around the cylindrical surface of thespecimen at the center of the gage section.7.5.1 Bonded Resistance
43、 Strain GagesStrain gage selec-tion is a compromise based on the type of material. An activegage length of 1.5 mm 0.062 in. is recommended for mostmaterials although larger gages may be more suitable for somewoven fabrics (with consolidated tow thicknesses larger than1.5 mm 0.062 in.), provided the
44、specimen gage length canaccommodate such gages (as specified in 8.2). Gage calibrationcertification shall comply with Test Method E 251. For lami-nated composites, the strain gage should cover a minimum ofthree laminate plies.7.6 System AlignmentPoor system alignment can be amajor contributor to pre
45、mature failure, to elastic property datascatter, or both. Practice E 1012 describes bending evaluationguidelines and describes potential sources of misalignmentFIG. 3 Drawing of End Tabs and Cylindrical Specimen Assembly (inch-pound units)FIG. 4 Drawing of Alignment and Bonding Fixture (showing 12 s
46、pecimens)D 7291/D 7291M 074during tensile testing. Alignment should be checked using acylindrical metal specimen with a minimum of three straingages equally spaced around the circumference per PracticeE 1012. While the maximum advisable amount of systemmisalignment is material and location dependent
47、, good testingpractice is generally able to limit percent bending to within 5 %at moderate strain levels (1000 e). A system showingexcessive bending for the given application should be re-adjusted or modified.7.7 Conditioning ChamberWhen conditioning materialsin other than ambient laboratory environ
48、ments, a temperature/vapor-level controlled environmental conditioning chamber isrequired, that shall be capable of maintaining the requiredrelative temperature to within 63C 65F and the requiredrelative vapor level to within 63 %. Chamber conditions shallbe monitored either on an automated continuo
49、us basis or on amanual basis at regular intervals.7.8 Environmental Test ChamberAn environmental testchamber is required for test environments other than ambienttesting laboratory conditions. This chamber shall be capable ofmaintaining the gage section of the test specimen within 63C65F of the required test temperature during the mechanicaltest. In addition, the chamber may have to be capable ofmaintaining environmental conditions such as fluid exposure orrelative humidity during the test (see 11.4).8. Sampl
