1、Designation: C273/C273M 16Standard Test Method forShear Properties of Sandwich Core Materials1This standard is issued under the fixed designation C273/C273M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of last revision
2、. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test method covers the determination of
3、shearproperties of sandwich construction core materials associatedwith shear distortion of planes parallel to the facings. It coversthe determination of shear strength parallel to the plane of thesandwich, and the shear modulus associated with strains in aplane normal to the facings. The test may be
4、 conducted on corematerials bonded directly to the loading plates or the sandwichfacings bonded to the plates. Permissible core material formsinclude those with continuous bonding surfaces (such as balsawood and foams) as well as those with discontinuous bondingsurfaces (such as honeycomb).1.2 The v
5、alues stated in either SI units or inch-pound unitsare to be regarded separately as standard. 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 stand
6、ard.1.2.1 Within the text the inch-pound units are shown inbrackets.1.3 This standard 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 a
7、pplica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C271/C271M Test Method for Density of Sandwich CoreMaterialsC393 Test Method for Flexural Properties of SandwichConstructionsD792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plast
8、ics by DisplacementD883 Terminology Relating to PlasticsD2584 Test Method for Ignition Loss of Cured ReinforcedResinsD2734 Test Methods for Void Content of Reinforced PlasticsD3171 Test Methods for Constituent Content of CompositeMaterialsD3878 Terminology for Composite MaterialsD5229/D5229M Test Me
9、thod for MoistureAbsorption Prop-erties and Equilibrium Conditioning of Polymer MatrixComposite MaterialsD5687/D5687M Guide for Preparation of Flat CompositePanels with Processing Guidelines for Specimen Prepara-tionD5961/D5961M Test Method for Bearing Response of Poly-mer Matrix Composite Laminates
10、E4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE122 Practice for Calculating Sample Size to Estimate, WithSpecified Precision, the Average for a Characteristic of aLot or ProcessE177 Practice for Use of the Terms Precision and Bias inAS
11、TM Test MethodsE456 Terminology Relating to Quality and Statistics3. Terminology3.1 DefinitionsTerminology D3878 defines terms relatingto high-modulus fibers and their composites, as well as termsrelating to sandwich constructions. Terminology D883 definesterms relating to plastics. Terminology E6 d
12、efines termsrelating to mechanical testing. Terminology E456 and PracticeE177 define terms relating to statistics. In the event of aconflict between terms, Terminology D3878 shall have prece-dence over the other terminologies.3.2 Symbols: b = width of specimenCV = coefficient of variation statistic
13、of a sample populationfor a given property (in percent)G = core shear modulusL = length of specimenP = force on specimenS = P/u, slope of initial portion of force-deflection curve1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibility
14、of Subcommittee D30.09 onSandwich Construction.Current edition approved April 1, 2016. Published April 2016. Originallyapproved in 1951. Last previous edition approved in 2011 as C273 11. DOI:10.1520/C0273_C0273M-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM
15、 Customer Service at serviceastm.org. For Annual Book 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 States1Sn-1= standard deviation statis
16、tic of a sample population fora given propertyt = thickness of coreu = displacement of loading platesx1= test result for an individual specimen from the samplepopulation for a given propertyx5 mean or average (estimate of mean) of a samplepopulation for a given property = core engineering shear stra
17、in = core shear stress4. Summary of Test Method4.1 This test method consists of subjecting a sandwich coreor sandwich panel to monotonically increasing shear forceparallel to the plane of its faces. The force is transmitted to thespecimen through bonded loading plates that are subjected toopposing t
18、ensile or compressive displacements that result in ashear force on the sandwich core. Core shear modulus, stress,and strength are reported in terms of the nominal shear area ofthe core.4.2 The only acceptable failure mode is shear failure of thecore material. Adhesive or cohesive failures, or both,
19、at thecore-to-facesheet, facesheet-to-load-plate, or (if no facesheetsare used) core-to-load-plate interface are not acceptable failuremodes.5. Significance and Use5.1 The core shear properties are fundamental propertiesthat are used in the design of sandwich panels. This test methodprovides informa
20、tion on the force-deflection behavior of sand-wich constructions or cores when loaded in shear parallel to theplane of the facings. From a complete force-deflection curve, itis possible to compute core shear stress at any force (such asthe shear stress at proportional limit, at yield, or at maximumf
21、orce) and to compute an effective core shear modulus.5.2 The test does not produce pure shear, but the specimenlength is prescribed so that secondary stresses have a minimumeffect. Approximate shear properties can also be obtained froma sandwich flexure test (see Test Method C393).5.3 This test meth
22、od provides a standard method of obtain-ing sandwich core shear data for material specifications,sandwich panel design, research and development applications,and quality assurance.5.4 Factors that influence core shear strength and shalltherefore be reported include the following: facing material,cor
23、e material, adhesive material, methods of materialfabrication, core geometry (density, cell size, orientation, etc.),adhesive thickness, specimen geometry and associated mea-surement accuracy, specimen preparation, specimenconditioning, environment of testing, specimen alignment,loading procedure, s
24、peed of testing, and adhesive void content.Further, core-to-facing strength may be different betweenprecured/bonded and co-cured facings in sandwich panels withthe same core and facing material.6. Interferences6.1 Material and Specimen PreparationPoor material fab-rication practices, lack of control
25、 of fiber alignment, anddamage induced by improper specimen machining are knowncauses of high data scatter in composites in general. Specificmaterial factors that affect sandwich composites include vari-ability in core density and degree of cure of resin in both facingmatrix material and core bondin
26、g adhesive. Important aspectsof sandwich panel specimen preparation that contribute to datascatter are incomplete or nonuniform core bonding to facings,misalignment of core and facing elements, the existence ofjoints, voids or other core and facing discontinuities, out-of-plane curvature, facing thi
27、ckness variation, and surface rough-ness. For this particular core shear test, thickness of theadhesive bond to honeycomb core (adhesive-filled depth intothe honeycomb core cells) may affect the core shear strengthand modulus values depending on the core thickness.6.2 System AlignmentUnintended load
28、ing eccentricitieswill cause premature failure. Every effort should be made toeliminate undesirable eccentricities from the test system. Sucheccentricities may occur as a result of misaligned grips, poorspecimen preparation, or poor alignment of the bonded loadingplates.6.3 GeometrySpecific geometri
29、c factors that affect coreshear behavior of sandwich panels includes core cell geometry(shape, density, orientation), core thickness, and adhesivethickness.6.4 EnvironmentResults are affected by the environmentalconditions under which the tests are conducted. Specimenstested in various environments
30、can exhibit significant differ-ences in both static strength and failure mode. Critical envi-ronments must be assessed independently for each sandwichconstruction tested.7. Apparatus7.1 Micrometers and CalipersA micrometer with a 4 to 7mm 0.16 to 0.28 in. nominal diameter ball-interface or a flatanv
31、il interface shall be used to measure the specimen thick-ness. A ball interface is recommended for thickness measure-ments when facings are bonded to the core and at least onesurface is irregular (e.g., the bag-side of a thin facing laminatethat is neither smooth nor flat). A micrometer or caliper w
32、ith aflat anvil interface is recommended for thickness measure-ments when facings are bonded to the core and both surfacesare smooth (e.g., tooled surfaces).Amicrometer or caliper witha flat anvil interface shall be used for measuring length andwidth, as well as the specimen thickness when no facing
33、s arepresent. The use of alternative measurement devices is permit-ted if specified (or agreed to) by the test requestor and reportedby the testing laboratory. The accuracy of the instruments shallbe suitable for reading to within 1 % of the sample dimensions.For typical specimen geometries, an inst
34、rument with an accu-racy of 6 0.025 mm 6 0.001 in. is adequate for the length,width, and thickness measurements.7.2 Test FixturesEither a tensile or compressive loadingmode may be used. In either case, the test specimen shall berigidly supported by means of steel plates bonded to the facings(see Not
35、e 1) as shown in Fig. 1. The thickness of the plates maybe varied in accordance with the strength of the sandwich (seeNote 2), but the plate length shall be such that the line of actionC273/C273M 162of the direct tensile or compressive force shall pass through thediagonally opposite corners of the s
36、andwich as shown in Fig. 1.A correct line of load action may also be obtained bymodifying the core length to thickness ratio provided thespecimen dimensional requirements noted in 8.2 are fulfilled.NOTE 1To ensure a core shear failure on some honeycomb cores, twoplies of adhesive must be used to bon
37、d the honeycomb to the steel plates.This provides deeper adhesive fillets on the honeycomb cell walls.NOTE 2It has been found that loading plates having a bendingstiffness per unit width, D = EI / b, not less than 2.67 MN - mm2/mm widthper millimeter of core thickness (600 000 lb-in.2/in. per inch o
38、f corethickness) have performed satisfactorily.7.2.1 Tension LoadingEither pinned or bolted load plate-to-universal-joint test fixtures, as shown in Fig. 2, may be used.The overall load-train shall be of the suspended, self-aligningtype.7.2.2 Compression LoadingLoad plates shall taper to aknife-edge
39、 and fit into V-notch loading blocks, as shown in Fig.3. V-notch loading blocks shall be rigidly attached to the testmachine and aligned flat and parallel to within 60.02 mm60.001 in.7.3 Testing MachineThe testing machine shall be in ac-cordance with Practices E4 and shall satisfy the followingrequi
40、rements: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 movable head acontrolled velocity with respect to the stationary head. Thevelo
41、city of the movable head shall be capable of beingregulated in accordance with 11.6.7.3.3 Force IndicatorThe testing machine force-sensingdevice shall be capable of indicating the total force beingcarried by the test specimen. This device shall be essentiallyfree from inertia lag at the specified ra
42、te of testing and shallindicate the force with an accuracy over the force range(s) ofinterest of within 61 % of the indicated value.7.3.4 Deflectometer, Compressometer, or ExtensometerThe deflection measurement device shall be capable of mea-suring the displacement with a precision of at least 61%.7
43、.4 Conditioning ChamberWhen conditioning materialsat non-laboratory environments, a temperature/vapor-levelcontrolled environmental conditioning chamber is required thatshall be capable of maintaining the required temperature towithin 63C 65F and the required relative humidity levelto within 63 %. C
44、hamber conditions shall be monitored eitheron an automated continuous basis or on a manual basis atregular intervals.7.5 Environmental Test ChamberAn environmental testchamber is required for test environments other than ambienttesting laboratory conditions. This chamber shall be capable ofmaintaini
45、ng the entire test specimen at the required testenvironment during the mechanical test.8. Sampling and Test Specimens8.1 SamplingTest at least five specimens per test condi-tion unless valid results can be gained through the use of fewerspecimens, as in the case of a designed experiment. Forstatisti
46、cally significant data, consult the procedures outlined inPractice E122. Report the method of sampling.8.2 GeometryThe test specimens shall have a thicknessequal to the thickness of the sandwich, a width not less than 50mm 2.0 in., and a length not less than twelve times thethickness.8.3 Specimen Pr
47、eparation and MachiningGuide D5687/D5687M provides recommended specimen preparation prac-tices and should be followed where practical.8.4 LabelingLabel the test specimens so that they will bedistinct from each other and traceable back to the panel oforigin, and will neither influence the test nor be
48、 affected by it.9. Calibration9.1 The accuracy of all measuring equipment shall havecertified calibrations that are current at the time of use of theequipment.10. Conditioning10.1 The recommended pre-test specimen condition is ef-fective moisture equilibrium at a specific relative humidity asestabli
49、shed by Test Method D5229/D5229M; however, if thetest requester does not explicitly specify a pre-test conditioningenvironment, conditioning is not required and the test speci-mens may be tested as prepared.FIG. 1 Plate Shear Specimens, Force Line of ActionC273/C273M 163NOTE 3The term moisture, as used in Test Method D5229/D5229M,includes not only the vapor of a liquid and its condensate, but the liquiditself in large quantities, as for immersion.10.2 The pre-test specimen conditioning process, to includespecified environmental exposure lev
