1、Designation: C365/C365M 11aStandard 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 r
2、evision. 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 Department of Defense.1. Scope1.1 This test method covers the determination o
3、f 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 particular,
4、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).1.2 Th
5、is 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 separatel
6、y 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 This st
7、andard 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
8、 ASTM Standards:2C271/C271M Test Method for Density of Sandwich CoreMaterialsC274 Terminology of Structural Sandwich ConstructionsD883 Terminology Relating to PlasticsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for Moisture AbsorptionProperties and Equilibrium Conditioning of P
9、olymer Ma-trix Composite MaterialsD7336/D7336M Test 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,W
10、ith Specified Precision, the Average for a Characteristicof a Lot or ProcessE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in DatabasesE14
11、34 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in DatabasesE1471 Guide for Identification of Fibers, Fillers, and CoreMaterials in Computerized Material Property Databases3. Terminology3.1 DefinitionsTerminology D3878 defines terms relatingto high-modulus fibers
12、and their composites. TerminologyC274 defines terms relating to structural sandwich construc-tions. Terminology D883 defines terms relating to plastics.Terminology E6 defines terms relating to mechanical testing.Terminology E456 and Practice E177 define terms relating tostatistics. In the event of a
13、 conflict between terms, TerminologyD3878 shall have precedence over the other terminologies.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 Fzfcuul
14、timate flatwise compressive strength3.2.5 Fzfc0.02flatwise compressive strength at 2 % LVDT/compressometer deflection1This 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
15、 approved Nov. 1, 2011. Published December 2011. Originallyapproved in 1955. Last previous edition approved in 2011 as C365/C365M 11.DOI: 10.1520/C0365_C0365M-11A.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book
16、 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.3.2.6 Pmaxmaximum force carried by test specimen be-fore failure3.2.7 P0.02force ca
17、rried by test specimen at 2 % LVDT/compressometer deflection3.2.8 Sn1standard deviation statistic of a sample popula-tion for a given property3.2.9 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 (esti
18、mate of mean) of a samplepopulation for a given property3.2.12 dLVDT or compressometer deflection3.2.13 szfc0.02flatwise 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
19、to the plane of thefacings as the core would be placed in a structural sandwichconstruction. 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
20、of sandwich cores that are usedin designing sandwich panels. Deformation data can be ob-tained, and from a complete force versus deformation curve, itis possible to compute the compressive stress at any appliedforce (such as compressive stress at proportional limit force orcompressive strength at th
21、e maximum force) and to computethe effective modulus of the core.5.2 This test method provides 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 ass
22、urance.5.3 In order to prevent local crushing of some honeycombcores, it is often desirable to 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
23、stabilized com-pression strength) or non-stabilized specimens (reported asbare compression strength). 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 rep
24、orted include the following: corematerial, methods of material fabrication, core geometry (cellsize), core density, specimen geometry, specimen preparation,specimen conditioning, environment of testing, specimenalignment, loading procedure, and speed of testing.6. Interferences6.1 Material and Speci
25、men PreparationPoor materialfabrication practices and damage induced by improper speci-men machining are known causes of high data scatter incomposites and sandwich structures in general. A specificmaterial factor that affects sandwich cores is variability in coredensity. Important aspects of sandwi
26、ch core specimen prepa-ration that contribute to data scatter include the existence ofjoints, voids or other core discontinuities, out-of-plane curva-ture, and surface roughness.6.2 System AlignmentNon-uniform loading over the sur-face of the test specimen may cause premature failure. Non-uniform lo
27、ading may result from non-uniform specimen thick-ness, failure to locate the specimen concentrically 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 sha
28、pe (square or circular).Flatwise compressive strength and modulus measurements areparticularly sensitive 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 s
29、eating.6.4 EnvironmentResults are affected by the environmen-tal conditions under which specimens are conditioned, as wellas the conditions under which the tests are conducted. Speci-mens tested in various environments can exhibit significantdifferences in both strength behavior and failure mode. Cr
30、iticalenvironments must be assessed independently for each corematerial tested.7. Apparatus7.1 Micrometers and CalipersA micrometer having a flatanvil interface, or a caliper of suitable size, shall be used. Theaccuracy of the instrument(s) shall be suitable for reading towithin 1 % of the sample le
31、ngth and width (or diameter) andthickness. For typical specimen geometries, an instrument withan accuracy of 612 m 60.0005 in. is desirable for thicknessmeasurement, whereas an instrument with an accuracy of6250 m 60.010 in. is acceptable for length and width (ordiameter) measurement.7.2 Loading Pla
32、tensForce shall be introduced into thespecimen using one fixed flat platen and one spherical seat(self-aligning) platen. The platens shall be well-aligned andshall not apply eccentric forces. A satisfactory type of appara-tus is shown in Figs. 1 and 2. The platen surfaces shall extendbeyond the test
33、 specimen periphery. If the platens are notsufficiently hardened, or simply to protect the platen surfaces,a hardened plate (with parallel surfaces) can be insertedbetween each end of the fixture and the corresponding platen.7.3 Testing MachineThe testing machine shall be inaccordance with Practices
34、 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 movable head acontrolled velocity with
35、 respect to the stationary head. Thevelocity of the movable head shall be capable of beingregulated in accordance with 11.5.7.3.3 Force IndicatorThe testing machine load-sensingdevice shall be capable of indicating the total force beingcarried by the test specimen. This device shall be essentiallyfr
36、ee from inertia lag at the specified rate of testing and shallC365/C365M 11a2indicate the force with an accuracy over the force range(s) ofinterest of within 61 % of the indicated value.7.4 Crosshead Displacement IndicatorThe testing ma-chine shall be capable of monitoring and recording the cross-he
37、ad displacement (stroke) with a precision of at least 61%.If machine compliance is significant, it is acceptable tomeasure the displacement of the movable head using an LVDT,compressometer, or similar device with 61 % precision ondisplacement. A transducer and rod setup, shown in Figs. 1 and2, has b
38、een 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 transducer rod is insertedthrough the hole, such that it contacts the upper loading platen.NOTE 1Bonded resistance strain gages are not usually con
39、sideredsatisfactory for measuring strain in this application because of theirstiffness. The reinforcing effect of bonding gages to some cores can leadto large errors in measurement of strain.7.5 Conditioning ChamberWhen conditioning materialsat non-laboratory environments, a temperature/vapor-levelc
40、ontrolled environmental conditioning chamber is required thatshall be capable of maintaining the required 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 i
41、ntervals.7.6 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 at therequired test environment during the mechanical test.8. Sampl
42、ing 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. Forstatistically significant data, consult the procedures outlined inPractice E122. Report the method of s
43、ampling.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 sandwich core thickness.Minimum specimen cross-sectional areas for various types ofcore materials are as follows:NOTE 2The specimens cross-sectio
44、nal area is defined in the facingplane, in regard to the 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 Co
45、ntinuous Bonding Surfaces (for example, BalsaWood, Foams)The minimum facing area of the specimenshall be 625 mm21.0 in.2.8.2.2 Discontinuous Cellular Bonding Surfaces (for ex-ample, Honeycomb)The required facing area of the speci-men is dependent upon the cell size, to ensure a minimumnumber of cell
46、s are tested. Minimum facing areas are recom-mended in Table 1 for the more common cell sizes. These areintended to provide approximately 60 cells minimum in the testFIG. 1 Platen, Transducer, and Rod Setup FIG. 2 Close-up of Specimen Between Loading PlatensC365/C365M 11a3specimen. The largest facin
47、g 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 number of cells to be tested in the specimen.8.3 Specimen Preparation and MachiningPrepare the testspecimens so that the loaded surfaces will
48、 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, mill
49、ing, or grinding. Theuse of diamond tooling has been found to be extremelyeffective for many material systems. Record and report thespecimen cutting preparation method.NOTE 3In order to prevent local crushing of some honeycomb cores,it is often desirable to reinforce the facing plane surfaces with a suitablematerial. In such instances, the facing plane surfaces may be dipped in athin layer of resin, or thin facings may be bonded to the facing planesurfaces of the core. When either of these stabilization techniques is used,the
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