1、Designation: C365/C365M 16Standard Test Method forFlatwise Compressive Properties of Sandwich Cores1This standard is issued under the fixed designation C365/C365M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of last re
2、vision. 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 determinati
3、on of compres-sive strength and modulus of sandwich cores. These propertiesare usually determined for design purposes in a directionnormal to the plane of facings as the core would be placed ina structural sandwich construction. The test procedures pertainto compression in this direction in particul
4、ar, but also can beapplied with possible minor variations to determining compres-sive properties in other directions. Permissible core materialforms include those with continuous bonding surfaces (such asbalsa wood and foams) as well as those with discontinuousbonding surfaces (such as honeycomb).1.
5、2 This test method does not cover the determination ofcompressive core crush properties. Reference Test MethodD7336/D7336M for determination of static energy absorptionproperties of honeycomb sandwich core materials.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separ
6、ately 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 standard.1.3.1 Within the text the inch-pound units are shown inbrackets.1.4 Thi
7、s 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-bility of regulatory limitations prior to use.2. Referenced Document
8、s2.1 ASTM Standards:2C271/C271M Test Method for Density of Sandwich CoreMaterialsD883 Terminology Relating to PlasticsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for MoistureAbsorption Prop-erties and Equilibrium Conditioning of Polymer MatrixComposite MaterialsD7336/D7336M Tes
9、t Method for Static Energy AbsorptionProperties of Honeycomb Sandwich Core MaterialsE4 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 Charact
10、eristic of aLot or ProcessE177 Practice for Use of the Terms Precision and Bias inASTM 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
11、 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 event of aconflict between terms, Terminology D3878 shall have prece-dence over the other term
12、inologies.3.2 Symbols:3.2.1 Across-sectional area of a test specimen3.2.2 CVcoefficient of variation statistic of a samplepopulation for a given property (in percent)3.2.3 Ezfcflatwise compressive modulus3.2.4 Fzfcuultimate flatwise compressive strength3.2.5 Fzfc 0.02flatwise compressive strength at
13、 2 % LVDT/compressometer deflection3.2.6 Pmaxmaximum force carried by test specimen beforefailure3.2.7 P0.02force carried by test specimen at 2 % LVDT/compressometer deflection3.2.8 Sn1standard deviation statistic of a sample popula-tion for a given property1This test method is under the jurisdictio
14、n of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.09 onSandwich Construction.Current edition approved May 15, 2016. Published June 2016. Originallyapproved in 1955. Last previous edition approved in 2011 as C365/C365M 11A.DOI: 10.1520/C0365_C0365M-16.
15、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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C
16、700, West Conshohocken, PA 19428-2959. United States13.2.9 tthickness of a test specimen3.2.10 x1test result for an individual specimen from thesample population for a given property3.2.11 xmean or average (estimate of mean) of a samplepopulation for a given property3.2.12 LVDT or compressometer def
17、lection3.2.13 zfc0.02flatwise compressive stress at 2 % LVDT/compressometer deflection4. Summary of Test Method4.1 This test method consists of subjecting a sandwich coreto a uniaxial compressive force normal to the plane of thefacings as the core would be placed in a structural sandwichconstruction
18、. The force is transmitted to the sandwich coreusing loading platens attached to the testing machine.5. Significance and Use5.1 Flatwise compressive strength and modulus are funda-mental mechanical properties of sandwich cores that are usedin designing sandwich panels. Deformation data can beobtaine
19、d, and from a complete force versus deformation curve,it is possible to compute the compressive stress at any appliedforce (such as compressive stress at proportional limit force orcompressive strength at the maximum force) and to computethe effective modulus of the core.5.2 This test method provide
20、s a standard method of obtain-ing the flatwise compressive strength and modulus for sand-wich core structural design properties, material specifications,research and development applications, and quality assurance.5.3 In order to prevent local crushing of some honeycombcores, it is often desirable t
21、o stabilize the facing plane surfaceswith a suitable material, such as a thin layer of resin or thinfacings. Flatwise compressive strength data may be generatedusing either stabilized specimens (reported as stabilized com-pression strength) or non-stabilized specimens (reported asbare compression st
22、rength). It is customary aerospace industrypractice to determine compression modulus only when usingstabilized specimens.5.4 Factors that influence the flatwise compressive strengthand shall therefore be reported include the following: corematerial, methods of material fabrication, core geometry (ce
23、llsize), core density, specimen geometry, specimen preparation,specimen conditioning, environment of testing, specimenalignment, loading procedure, and speed of testing.6. Interferences6.1 Material and Specimen PreparationPoor material fab-rication practices and damage induced by improper specimenma
24、chining 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 include the existence of joints,
25、voidsor other core discontinuities, out-of-plane curvature, and sur-face roughness.6.2 System AlignmentNon-uniform loading over the sur-face of the test specimen may cause premature failure. Non-uniform loading may result from non-uniform specimenthickness, failure to locate the specimen concentrica
26、lly in thefixture, or system or fixture misalignment.6.3 GeometrySpecific geometric factors that affect sand-wich flatwise compressive strength include core cell geometry,core thickness, and specimen shape (square or circular).Flatwise compressive strength and modulus measurements areparticularly se
27、nsitive to thickness variations over the cross-sectional area of the specimen, which can cause local loadingeccentricities, as well as toe regions in the force versusdisplacement curves due to specimen seating.6.4 EnvironmentResults are affected by the environmentalconditions under which specimens a
28、re conditioned, as well asthe conditions under which the tests are conducted. Specimenstested in various environments can exhibit significant differ-ences in both strength behavior and failure mode. Criticalenvironments must be assessed independently for each corematerial tested.7. Apparatus7.1 Micr
29、ometers 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 is recommended for thickness measure-ments of stabilized specimens (in accordance with 8.3) when atleast one faci
30、ng plane surface is irregular (e.g. the bag-side ofa thin facing laminate that is neither smooth nor flat). Amicrometer or caliper with a flat anvil interface is recom-mended for thickness measurements of stabilized specimenswhen both facing plane surfaces are smooth (e.g. tooledsurfaces). A microme
31、ter or caliper with a flat anvil interfaceshall be used for measuring length and width (or diameter), aswell as the specimen thickness when the facing plane surfacesare not stabilized (e.g. bare). The use of alternative measure-ment devices is permitted if specified (or agreed to) by the testrequest
32、or and reported by the testing laboratory. The accuracyof the instrument(s) shall be suitable for reading to within 1 %of the sample length and width (or diameter) and thickness. Fortypical specimen geometries, an instrument with an accuracyof 60.012 mm 60.0005 in. is adequate for thicknessmeasureme
33、nt, whereas an instrument with an accuracy of60.25 mm 60.010 in. is adequate for length and width (ordiameter) measurement.7.2 Loading PlatensForce shall be introduced into thespecimen using one fixed flat platen and one spherical seat(self-aligning) platen. The platens shall be well-aligned andshal
34、l not apply eccentric forces. A satisfactory type of appara-tus is shown in Figs. 1 and 2. The platen surfaces shall extendbeyond the test specimen periphery. If the platens are notsufficiently hardened, or simply to protect the platen surfaces,a hardened plate (with parallel surfaces) can be insert
35、edbetween each end of the fixture and the corresponding platen.7.3 Testing MachineThe testing machine shall be in ac-cordance with Practices E4 and shall satisfy the followingrequirements:C365/C365M 1627.3.1 Testing Machine ConfigurationThe testing machineshall have both an essentially stationary he
36、ad 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. Thevelocity of the movable head shall be capable of beingregulated in accordance with 11.5.7.3.3 Force IndicatorT
37、he testing machine load-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 rate of testing and shallindicate the force with an accuracy over the force range(s) ofinterest of within 61
38、% of the indicated value.7.4 Crosshead Displacement IndicatorThe testing ma-chine shall be capable of monitoring and recording the cross-head displacement (stroke) with a precision of at least 61%.If machine compliance is significant, it is acceptable tomeasure the displacement of the movable head u
39、sing an LVDT,compressometer, or similar device with 61 % precision ondisplacement. A transducer and rod setup, shown in Figs. 1 and2, has been found to work satisfactorily. In the example shown,a small hole is drilled in the center of the core specimen and inthe bottom loading platen, and a transduc
40、er rod is insertedthrough the hole, such that it contacts the upper loading platen.NOTE 1Bonded resistance strain gages are not usually consideredsatisfactory for measuring strain in this application because of theirstiffness. The reinforcing effect of bonding gages to some cores can leadto large er
41、rors in measurement of strain.7.5 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
42、humidity levelto within 63 %. Chamber conditions shall be monitored eitheron an automated continuous basis or on a manual basis atregular intervals.7.6 Environmental Test ChamberAn environmental testchamber is required for test environments other than ambienttesting laboratory conditions. This chamb
43、er shall be capable ofmaintaining the gage section of the test specimen at therequired test environment 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 th
44、e case of a designed experiment. Forstatistically significant data, consult the procedures outlined inPractice E122. Report the method of sampling.8.2 GeometryTest specimens shall have a square or cir-cular cross-section not exceeding 10 000 mm216.0 in.2, andshall be equal in thickness to the sandwi
45、ch core thickness.Minimum specimen cross-sectional areas for various types ofcore materials are as follows:NOTE 2The specimens cross-sectional area is defined in the facingFIG. 1 Platen, Transducer, and Rod Setup FIG. 2 Close-up of Specimen Between Loading PlatensC365/C365M 163plane, in regard to th
46、e orientation that the core would be placed in astructural sandwich construction. For example, for a honeycomb core thecross-sectional area is defined in the plane of the cells, which isperpendicular to the orientation of the cell walls.8.2.1 Continuous Bonding Surfaces (for example, BalsaWood, Foam
47、s)The minimum facing area of the specimenshall be 625 mm21.0 in.2.8.2.2 Discontinuous Cellular Bonding Surfaces (forexample, Honeycomb)The required facing area of the speci-men is dependent upon the cell size, to ensure a minimumnumber of cells are tested. Minimum facing areas are recom-mended in Ta
48、ble 1 for the more common cell sizes. These areintended to provide approximately 60 cells minimum in the testspecimen. The largest facing area listed in the table (5625mm29.0 in.2) is a practical maximum for this test method.Cores with cell sizes larger than 9 mm 0.375 in. may requirea smaller numbe
49、r of cells to be tested in the specimen.8.3 Specimen Preparation and MachiningPrepare the testspecimens so that the loaded surfaces will be parallel to eachother and perpendicular to the sides of the specimen. Takeprecautions when cutting specimens from large sheets of coreto avoid notches, undercuts, and rough or uneven surfaces dueto inappropriate machining methods. Obtain final dimensionsby water-lubricated precision sawing, milling, or grinding. Theuse of diamond tooling has been found to be extremelyeffective for many m
