1、Designation: C 273/C 273M 07aStandard Test Method forShear Properties of Sandwich Core Materials1This standard is issued under the fixed designation C 273/C 273M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of last rev
2、ision. A number in parentheses indicates the year of last reapproval.A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the 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 b
4、e 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
5、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 systemmust be used independently of the other. Combining valuesfrom the
6、 two systems may result in nonconformance with thestandard.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 applica-bi
7、lity of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 271/C 271M Test Method for Density of Core SandwichMaterialsC 274 Terminology of Structural Sandwich ConstructionsC 393 Test Method for Flexural Properties of SandwichConstructionsD 792 Test Methods for Density
8、and Specific Gravity (Rela-tive Density) of Plastics by DisplacementD 883 Terminology Relating to PlasticsD 2584 Test Method for Ignition Loss of Cured ReinforcedResinsD 2734 Test Methods for Void Content of Reinforced Plas-ticsD 3171 Test Methods for Constituent Content of CompositeMaterialsD 3878
9、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 CompositePanels with Processing Guidelines for Specimen Prepara-tionD 5961/D 5961M Test Meth
10、od for Bearing Response ofPolymer Matrix Composite LaminatesE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical Test-ingE 122 Practice for Calculating Sample Size to Estimate,With a Specified Tolerable Error, the Average for aCharacteristic of a Lo
11、t or ProcessE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 456 Terminology Relating to Quality and StatisticsE 1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in DatabasesE 1434 Guide for Recording Mechanical Test Data of Fiber-Reinfor
12、ced 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. TerminologyC 274 defines terms relat
13、ing to structural sandwich construc-tions. Terminology D 883 defines terms relating to plastics.Terminology E6defines terms relating to mechanical testing.Terminology E 456 and Practice E 177 define terms relating tostatistics. In the event of a conflict between terms, TerminologyD 3878 shall have p
14、recedence over the other terminologies.3.2 Symbols:1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.09 onSandwich Construction.Current edition approved Oct. 1, 2007. Published October 2007. Originallyapproved
15、 in 1951. Last previous edition approved in 2007 as C 273 07.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.
16、1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.b = width of specimenCV = coefficient of variation statistic of a sample populationfor a given property (in percent)G = core shear modulusL = length of specimenP = force on specimenS =
17、DP/Du, slope of initial portion of force-deflection curveSn-1= standard deviation statistic 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 propertyx = mean or average (e
18、stimate of mean) of a samplepopulation for a given propertyg = core engineering shear straint = 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
19、is transmitted to thespecimen through bonded loading plates that are subjected toopposing tensile 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
20、failure mode is shear failure of thecore material. Adhesive or cohesive failures, or both, 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
21、 propertiesthat are used in the design of sandwich panels. This test methodprovides information 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 s
22、tress at any force (such asthe shear stress at proportional limit, at yield, or at maximumforce) 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
23、 can also be obtained froma sandwich flexure test (see Test Method C 393).5.3 This test method 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 c
24、ore shear strength and shalltherefore be reported include the following: facing material,core material, adhesive material, methods of material fabrica-tion, core geometry (density, cell size, orientation, etc.),adhesive thickness, specimen geometry and associated mea-surement accuracy, specimen prep
25、aration, specimen condition-ing, environment of testing, specimen alignment, loadingprocedure, speed of testing, and adhesive void content. Further,core-to-facing strength may be different between precured/bonded and co-cured facings in sandwich panels with the samecore and facing material.6. Interf
26、erences6.1 Material and Specimen PreparationPoor materialfabrication practices, lack of control 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-ab
27、ility in core density and degree of cure of resin in both facingmatrix material and core bonding 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 existen
28、ce ofjoints, voids or other core and facing discontinuities, out-of-plane curvature, facing thickness 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
29、 strengthand modulus values depending on the core thickness.6.2 System AlignmentUnintended loading 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, poorsp
30、ecimen preparation, or poor alignment of the bonded loadingplates.6.3 GeometrySpecific geometric 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 enviro
31、nmen-tal conditions under which the tests are conducted. Specimenstested in various environments 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 MicrometersThe mi
32、crometer(s) shall use a 4 to 6-mm0.16 to 0.25-in. nominal diameter ball-interface on irregularsurfaces such as the bag-side of a facing laminate, and a flatanvil interface on core material alone, machined edges, or verysmooth-tooled surfaces. The accuracy of the instrument(s)shall be suitable for re
33、ading to within 1 % of the sample length,width and thickness. For typical specimen geometries, aninstrument with an accuracy of 625 m 60.001 in. isdesirable for thickness, length and width measurement.7.2 Test FixturesEither a tensile or compressive loadingmode may be used. In either case, the test
34、specimen shall berigidly supported by means of steel plates bonded to the facings(see Note 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 actionof the direct tensile or c
35、ompressive force shall pass through thediagonally opposite corners of the sandwich 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.C 273/C 273M 07a2NOTE 1To e
36、nsure a core shear failure on some honeycomb cores, twoplies of adhesive must be used to bond 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
37、 than 2.67 MN - mm2/mm widthper millimeter of core thickness (600 000 lb-in.2/in. per inch of 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
38、suspended, self-aligningtype.7.2.2 Compression LoadingLoad plates shall taper to aknife-edge 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 te
39、sting machine shall be inaccordance with Practices E4and 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 impart
40、ing to the movable head acontrolled velocity with respect to the stationary head. Thevelocity 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
41、 test specimen. 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.7.3.4 Deflectometer, Compressometer, or ExtensometerThe deflection measurement
42、device shall be capable of mea-suring the displacement with a precision of at least 61%.7.4 Conditioning ChamberWhen conditioning materialsat non-laboratory environments, a temperature/vapor-levelcontrolled environmental conditioning chamber is required thatshall be capable of maintaining the requir
43、ed temperature towithin 63C 65F and the required relative humidity levelto within 63 %. Chamber 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 o
44、ther than ambienttesting laboratory conditions. This chamber shall be capable ofmaintaining 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 gaine
45、d through the use of fewerspecimens, as in the case of a designed experiment. Forstatistically significant data, consult the procedures outlined inPractice E 122. Report the method of sampling.8.2 GeometryThe test specimens shall have a thicknessequal to the thickness of the sandwich, a width not le
46、ss than 50mm 2.0 in., and a length not less than twelve times thethickness.8.3 Specimen Preparation and MachiningGuide D 5687/D 5687M provides recommended specimen preparation prac-tices and should be followed where practical.8.4 LabelingLabel the test specimens so that they will bedistinct from eac
47、h other and traceable back to the panel oforigin, and will neither influence the test nor be 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 spe
48、cimen condition is ef-fective moisture equilibrium at a specific relative humidity asestablished by Test Method D 5529/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.
49、NOTE 3The term moisture, as used in Test Method D 5229/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 levels and resulting moisturecontent, shall be reported with the data.10.3 If there is no explicit conditioning process, the condi-tioning process shall be reported as “unconditioned” and themoisture content as “unknown.”FIG. 1 Plate Shear Specimens, Force Line of ActionC 273/C 2
