1、Designation: D8067/D8067M 17Standard Test Method forIn-Plane Shear Properties of Sandwich Panels Using aPicture Frame Fixture1This standard is issued under the fixed designation D8067/D8067M; the number immediately following the designation indicates theyear of original adoption or, in the case of r
2、evision, 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 covers determination of apparentin-plane shear strength and stiffness properties
3、 of flat sandwichconstructions with composite face sheets. Permissible corematerial forms include those with continuous bonding surfaces(such as balsa wood and foams) as well as those withdiscontinuous bonding surfaces (such as honeycomb).1.2 The square test specimen with corner notches is me-chanic
4、ally fastened to a pinned metal frame along each edge.The frame is loaded in uni-axial tension which produces tensileforces in the frame elements at a 45 angle to the appliedtension. These tensile forces act along the edges of thespecimen to cause a state of predominately shear stress totransfer the
5、 applied force through the specimen. Procedure Auses a specimen without edge doublers; Procedure B uses aspecimen with four discrete edge doublers; Procedure C uses aspecimen with a continuous edge doubler.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as s
6、tandard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.3.1 Within the text the inch-pound units are shown inbrackets.1.4 This standard
7、 does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. .2. Referenced Documents2.1 AST
8、M Standards:2D883 Terminology Relating to PlasticsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for MoistureAbsorption Prop-erties and Equilibrium Conditioning of Polymer MatrixComposite MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Me
9、thods of Mechanical TestingE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE251 Test Methods for Performance Characteristics of Me-tallic Bonded Resistance Strain GagesE456 Terminology Relating to Quality and Statistics3. Terminology3.1 DefinitionsTerminology D3878 defines t
10、erms relatingto high-modulus fibers and their composites, as well as termsrelating to sandwich constructions. Terminology D883 definesterms relating to plastics. Terminology E6 defines termsrelating to mechanical testing. Terminology E456 and PracticeE177 define terms relating to statistics. In the
11、event of aconflict between terms, Terminology D3878 shall have prece-dence over the other terminologies.3.2 Acronyms:3.2.1 CVcoefficient of variation statistic of a samplepopulation for a given property (in percent)3.2.2 Fsuface sheet ultimate shear stress3.2.3 Gfeffective face sheet chord shear mod
12、ulus3.2.4 measured engineering shear strain in face sheet3.2.5 Llength of specimen between doubler edges3.2.6 nnumber of specimens3.2.7 Papplied force3.2.8 Pmaxmaximum force carried by test specimen beforefailure1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials
13、and is the direct responsibility of Subcommittee D30.09 onSandwich Construction.Current edition approved Jan. 1, 2017. Published January 2017. DOI: 10.1520/D806717.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Boo
14、k of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recogni
15、zed principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.2.9 qrunning shear force per unit width along specimenedge3.2.10
16、 Sn-1standard deviation statistic of a sample popu-lation for a given property3.2.11 face sheet shear stress3.2.12 tface sheet thickness3.2.13 x1test result for an individual specimen from thesample population for a given property3.2.14 xmean or average (estimate of mean) of a samplepopulation for a
17、 given property4. Summary of Test Method4.1 This test method consists of subjecting a square panel ofsandwich construction to a set of forces along the panel edgessuch that the applied force is transferred through the panel viaa state of predominately shear stresses. The tensile forces areapplied us
18、ing a picture-frame loading fixture. By placing twostrain gage rosettes in the center of the specimen, the apparentshear stress-strain response of the panel can be measured.Out-of-plane panel deflection can be measured to assist indetecting panel buckling. It is noted that engineering shearstrain, a
19、s opposed to tensorial shear strain, is used throughoutthis standard.NOTE 1Tensorial shear strain may be used in analysis and reporting ofresults from tests using this standard, but requires the appropriateinclusion of the factor of 2, and clear documentation shall be made in thetest report.4.2 Proc
20、edure A uses a specimen without edge doublers.Procedure B uses a specimen with four discrete edge doublers;the data analysis for this procedure assumes that the doublersdo not carry significant shear force. Procedure C uses aspecimen with a continuous edge doubler; the data analysis forthis procedur
21、e assumes that the doublers carry some shearforce, and a correction is made to the applied force beforecalculating the shear stress in the panel.4.3 The acceptable failure modes are face sheet fracture,face sheet dimpling, face sheet wrinkling or core shear insta-bility. Failure of the sandwich core
22、-to-face sheet bond preced-ing one of the previous listed modes is not an acceptable failuremode. Failure originating at the panel corner notches is not anacceptable failure mode. Buckling of the panel prior to facesheet or core failure is not an acceptable failure mode, unlessotherwise specified as
23、 an acceptable response by the testrequestor. The test specimen face sheet thicknesses, corethickness, core material and adhesive material must be selectedto avoid the unacceptable failure modes.5. Significance and Use5.1 In-plane shear loading tests on flat sandwich construc-tions may be conducted
24、to determine the sandwich panelin-plane shear stiffness, the face sheets in-plane strength, thecore shear instability strength, or panel buckling response.5.2 This test method can be used to produce face sheetstrength data for structural design allowables, materialspecifications, and research and de
25、velopment applications; itmay also be used as a quality control test for bonded sandwichpanels.5.3 Factors that influence the panel strength and shalltherefore be reported include the following: face sheetmaterial, core material, adhesive material, methods of materialfabrication, face sheet stacking
26、 sequence and overall thickness,core geometry (cell size), core shear and compressive strength,core shear and compressive stiffness, adhesive thickness,specimen geometry, specimen preparation, specimenconditioning, environment of testing, specimen alignment,loading procedure, speed of testing, face
27、sheet void content,adhesive void content, and face sheet volume percent rein-forcement. Further, face sheet strength may be different be-tween precured/bonded and co-cured face sheets of the samematerial.6. Interferences6.1 Fixture GeometryThe basic configuration withthrough-pins and corner notches
28、may exhibit large deviationsfrom uniform stress. For example, in a configuration relativeclose in geometry to Method C, the shear stress at the centerwas predicted by finite element analysis (FEA) to be more than25 % lower than the value obtained from Eq 2, while the shearstress increases near the e
29、dges and corners so that localbuckling or material failure is likely to originate at theperiphery of the gage area. Farley and Baker reported on thestrong influence of the location of the pivot pins on the stressdistribution.3Moving the pivots to the corners of the gage area,while requiring a signif
30、icantly more complicated test fixture,provides a greatly improved stress distribution. Furthermore itwas reported that stiff edge doublers (e.g. steel rather thancomposite) increased the uniformity of the stresses.6.2 Material and Specimen PreparationPoor material fab-rication practices and damage i
31、nduced by improper specimenmachining are known causes of high data scatter in compositesand sandwich structures in general. A specific material factorthat affects sandwich cores is variability in core density.Important aspects of sandwich core specimen preparation thatcontribute to data scatter incl
32、ude the existence of joints, voidsor other core discontinuities, out-of-plane curvature, and sur-face roughness.6.3 GeometrySpecific geometric factors that affect sand-wich face sheet strength include face sheet thickness, core cellgeometry, and face sheet surface flatness. This test has beenmainly
33、used on panels with relatively thin face sheets (0.5 mm0.020 in.). The reliability of testing panels with thicker facesheets is unknown.6.4 EnvironmentResults are affected by the environmentalconditions under which specimens are conditioned, as well asthe conditions under which the tests are conduct
34、ed. Specimenstested in various environments can exhibit significant differ-ences in both strength behavior and failure mode. Criticalenvironments must be assessed independently for each specific31. G.L. Farley and D.J. Baker, “In-Plane Shear Test of Thin Panels,”Experimental Mechanics, Vol. 23, No.
35、1, 1983, pp. 8187.D8067/D8067M 172combination of core material, face sheet material, and core-to-face sheet interfacial adhesive (if used) that is tested.6.5 Elastic Modulus MeasurementShear modulus calcula-tions in this test method assume a uniform distribution of shearstress and engineering shear
36、strain in the center region of thespecimen. The actual uniformity is dependent on the materialorthotropy, the panel geometry, and doubler material andthickness.6.6 PottingEdge potting of open cell cores (filling the corecells with resin type material) may be used in the areas underthe loading bars.
37、The use of potting may be necessary to avoidcrushing the panel when the edge fasteners are installed.6.7 Edge DoublersThese are used to increase the thick-ness of the face sheets to avoid bearing failures in the facesheets at the edge fastener holes.6.8 Edge Doubler AdhesiveA suitable adhesive shall
38、 beselected for the test environment. The cure temperature of theadhesive should not exceed the face sheet material dry glasstransition temperature, Tg, to avoid changes to the face sheetmaterial. The limitation on cure temperature should alsoconsider any exothermic temperature increases in the adhe
39、siveduring cure (exothermic reactions are not unusual for adhesivesused in secondary bonding).7. Apparatus7.1 Micrometers and CalipersA micrometer witha4to7 mm 0.16 to 0.28 in. nominal diameter ball-interface or a flatanvil interface shall be used to measure the specimen thick-ness. A ball interface
40、 is recommended for thickness measure-ments when face sheets are bonded to the core and at least onesurface is irregular (e.g. the bag-side of a thin face sheetlaminate that is neither smooth nor flat). A micrometer orcaliper with a flat anvil interface is recommended for thicknessmeasurements when
41、face sheets are bonded to the core andboth surfaces are smooth (e.g. tooled surfaces). A micrometeror caliper with a flat anvil interface shall be used for measuringlength and width. The use of alternative measurement devicesis permitted if specified (or agreed to) by the test requestor andreported
42、by the testing laboratory. The accuracy of the instru-ments shall be suitable for reading to within1%ofthesampledimensions. For typical specimen geometries, an instrumentwith an accuracy of 60.025 mm 60.001 in. is adequate forthe length, width, and thickness measurements.NOTE 2The accuracies given a
43、bove are based on achieving measure-ments that are within 1% of the sample length, width, and thickness.7.2 Loading FixtureThe loading fixture shall be self-aligning and shall not apply eccentric forces. A satisfactorytype of apparatus for testing relatively thin face sheet panels isshown in Fig. 1.
44、 It consists of a steel frame with four cornerpins and 40 panel mounting fastener holes, see Fig. 2. Beforeusing the test fixture, a stress analysis of the entire fixtureshould be performed, using a conservative estimated failureload for the panel to be tested.7.3 Testing MachineThe testing machine
45、shall be in ac-cordance with Practices E4 and shall satisfy the followingrequirements:7.3.1 Testing Machine ConfigurationThe testing machineshall have both an essentially stationary head and a movablehead.7.3.2 Drive MechanismThe testing machine drive mecha-nism shall be capable of imparting to the
46、movable head acontrolled velocity with respect to the stationary head. Thevelocity of the movable head shall be capable of beingregulated in accordance with 11.4.7.3.3 Force IndicatorThe testing machine force-sensingdevice shall be capable of indicating the total force beingcarried by the test speci
47、men. This device shall be essentiallyfree from inertia lag at the specified rate of testing and shallindicate the force with an accuracy over the force range(s) ofinterest of within 61 % of the indicated value.7.4 DeflectometerWhen required by the test requestor, theout-of-plane deflection shall be
48、measured in the center of thespecimen by a properly calibrated device having an accuracy of61 % or better of the indicted value.7.5 Strain-Indicating DeviceWhen required by the testrequestor, strain data shall be determined by the specifiedmeans. When using bonded resistance strain gages, one tri-ax
49、ial gage rosette shall be located on each face at the center ofthe specimen. Full field digital image correlation or laser strainmeasurement methods may be used.FIG. 1 Panel In-Plane Shear Test Specimen and Test Fixture -Procedure C shown(Procedure A is the same except without the doublers ProcedureB is the same except with discrete doublers on each edge)D8067/D8067M 1737.6 Out-of-Plane DisplacementWhen required by the testrequestor, for cases where panel buckling response is to bemeasured, moire fringe methods or Digital Image Correla
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