1、Designation: D 7336/D 7336M 07Standard Test Method forStatic Energy Absorption Properties of HoneycombSandwich Core Materials1This standard is issued under the fixed designation D 7336/D 7336M; the number immediately following the designation indicates theyear of original adoption or, in the case of
2、 revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method determines the static energy absorptionproperties (compressive crush stress a
3、nd crush stroke) ofhoneycomb sandwich core materials. These properties areusually determined for design purposes in a direction normal tothe plane of facings as the honeycomb core material would beplaced in a structural sandwich construction.1.2 Permissible core materials are limited to those in hon
4、-eycomb form.1.3 This test method is not intended for use in crush testingof stabilized honeycomb core materials (for which the edges ofthe honeycomb core material are dipped in resin to resist localcrushing) or sandwich specimens (for which facings arebonded to the honeycomb core material).1.4 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.1.5 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 Sandwich CoreMaterialsC 274 Terminology of Structural Sandwich ConstructionsD 883 Terminology Relating to PlasticsD 3878 Terminology for Composite MaterialsD 5229/D 5229M Te
8、st Method for Moisture AbsorptionProperties and Equilibrium Conditioning of Polymer Ma-trix Composite MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical Test-ingE18 Test Methods for Rockwell Hardness of MetallicMaterialsE 122 Practice for
9、 Calculating Sample Size to Estimate,With a Specified Tolerable Error, the Average for aCharacteristic of a Lot 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-ReinforcedP
10、olymer-Matrix Composite Materials in DatabasesE 1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in DatabasesE 1471 Guide for Identification of Fibers, Fillers, and CoreMaterials in Computerized Material Property Databases3. Terminology3.1 DefinitionsTerminology
11、D 3878 defines terms relatingto high-modulus fibers and their composites. TerminologyC 274 defines terms relating 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 17
12、7 define terms relating tostatistics. In the event of a conflict between terms, TerminologyD 3878 shall have precedence over the other terminologies.NOTE 1If the term represents a physical quantity, its analyticaldimensions are stated immediately following the term (or letter symbol) in1This test me
13、thod is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.09 onSandwich Construction.Current edition approved May 1, 2007. Published May 2007.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cus
14、tomer Service at serviceastm.org. For Annual Book 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.fundamental dimension form, using
15、the following ASTM standard sym-bology for fundamental dimensions, shown within square brackets: Mfor mass, L for length, T for time, u for thermodynamic temperature,and nd for non-dimensional quantities. Use of these symbols is restrictedto analytical dimensions when used with square brackets, as t
16、he symbolsmay have other definitions when used without the brackets.3.2 Definitions of Terms Specific to This Standard:3.2.1 cell size L, nin a honeycomb core, the distancebetween two parallel and opposite cell walls at node bondareas, measured transverse to the ribbon direction.3.2.2 node bond area
17、, nin a honeycomb core, the areabetween two cells at which the component walls of the cells arebonded or attached.3.3 Symbols:A = cross-sectional area of a test specimen prior tocompressive crush testingCV = coefficient of variation statistic of a sample popula-tion for a given property (in percent)
18、KA= initial chord slope of the force versus displacement/deformation curveKB= post-crush slope of the force versus displacement/deformation curvePcr= average force carried by test specimen during com-pressive crushingscr= crush stroke in percentSn-1= standard deviation statistic of a sample populati
19、onfor a given propertyti= thickness of a test specimen prior to compressivecrush testingx1= test result for an individual specimen from thesample population for a given propertyx = mean or average (estimate of mean) of a samplepopulation for a given propertyd = recorded displacement/deflectiondA= di
20、splacement/deflection at which the initial chordslope intersects the displacement/deformation axisdB= displacement/deflection at which the post-crushingslope equals the initial chord slopedcr= crush strokeD = normalized displacement/deflectionscr= average compressive crush stress4. Summary of Test M
21、ethod4.1 This test method consists of subjecting a sandwichhoneycomb core material to a uniaxial compressive forcenormal to the plane of the facings as the honeycomb corematerial would be placed in a structural sandwich construction.The force is transmitted to the sandwich honeycomb corematerial usi
22、ng loading platens attached to the testing machine.Compressive force is applied past the initial failure force, suchthat the honeycomb core material is crushed under continuousdisplacement of the loading platens. Force versus loadingplaten displacement data are recorded and used to determinethe crus
23、h stress and crush stroke.5. Significance and Use5.1 Sandwich honeycomb core materials are used exten-sively in energy absorption applications, due to their ability tosustain compressive loading while being crushed. Properdesign of energy absorption devices utilizing sandwich honey-comb core materia
24、ls requires knowledge of the compressivecrush stress and crush stroke properties of the honeycomb corematerial.5.2 The procedures contained within this standard are in-tended to assess the crush stress and crush stroke properties ofthe sandwich honeycomb core material under static compres-sive loadi
25、ng. The dynamic crush stress of the honeycomb corematerial may vary from that measured under static loading,depending upon factors such as honeycomb core materialthickness, core material density, impact velocity, etc.5.3 This test method provides a standard method of obtain-ing the compressive crush
26、 stress and crush stroke for sandwichhoneycomb core material structural design properties, materialspecifications, research and development applications, andquality assurance.5.4 This test method is not intended for use in crush testingof stabilized honeycomb core materials (for which the edges ofth
27、e honeycomb core material are dipped in resin to resist localcrushing) or sandwich specimens (for which facings arebonded to the honeycomb core material).5.5 Factors that influence the compressive crush stress andcrush stroke and shall therefore be reported include thefollowing: honeycomb core mater
28、ial, methods of materialfabrication, core material geometry (nominal cell size), corematerial density, specimen geometry, specimen preparation,specimen conditioning, environment of testing, specimenalignment, pre-crush procedure, pre-crush depth, loading pro-cedure, and speed of testing.6. Interfere
29、nces6.1 Material and Specimen PreparationPoor materialfabrication practices and damage induced by improper speci-men machining are known causes of high data scatter incomposites and sandwich structures in general. Importantaspects of sandwich core material specimen preparation thatcontribute to data
30、 scatter include the existence of joints, voidsor other core material discontinuities, out-of-plane curvature/warpage, and surface roughness.6.2 System AlignmentNon-uniform loading over the sur-face of the test specimen may cause premature or unevencrushing. This may occur as a result from non-unifo
31、rmthickness, failing to locate the specimen concentrically in thefixture, or system or fixture misalignment.6.3 GeometrySpecific geometric factors that affect com-pressive crush stress and crush stroke include honeycomb corematerial cell geometry, core material thickness, and specimenshape (square o
32、r circular). Thicker specimens are generallydesirable, as the crush stroke is greater for thick specimenscompared to thin specimens.6.4 Pre-CrushingIt is recommended to pre-crush honey-comb core material specimens prior to test, as historical crushforce versus displacement data for pre-crushed speci
33、mens havedisplayed greater uniformity (consistency of the crush forcelevel for varying crush stroke) than have similar data for nonpre-crushed specimens. If tests are performed using analogequipment to record force versus displacement data, pre-crushing may be necessary to ensure the crush force is
34、recordedD 7336/D 7336M 072on a high sensitivity force scale (if not pre-crushed, the peakforce to initially fail the specimen may be substantially higherthan the crush force). Pre-crushing also aids interpretation offorce versus displacement data and calculation of crush strokevalues. Results are af
35、fected by the pre-crush depth and unifor-mity of pre-crushing.6.5 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 significantdif
36、ferences in both crush stress and crush stroke. Criticalenvironments must be assessed independently for each honey-comb core material 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(
37、s) shall be suitable for reading towithin 1 % of the sample length and width (or diameter) andthickness. For typical specimen geometries, an instrument withan accuracy of 6250 m 60.010 in. is desirable for thick-ness, length and width (or diameter) measurement.7.2 Loading PlatensForce shall be intro
38、duced into thespecimen using fixed flat platens (58 HRC minimum asspecified in Test Methods E18). One platen may be of thespherical seat (self-aligning) type, if it is capable of beinglocked in a fixed position once the platen has contacted andaligned with the specimen. The platens shall be well-ali
39、gned(centered with respect to the drive mechanism loading train)and shall not apply eccentric forces. A satisfactory type ofapparatus is shown in Figs. 1 and 2. The platen surfaces shallextend beyond the test specimen periphery. If the platens arenot sufficiently hardened, or simply to protect the p
40、latensurfaces, a hardened plate (with parallel surfaces) can beinserted between each end of the specimen and the correspond-ing platen.7.3 Testing MachineThe testing machine shall be inaccordance with Practices E4and shall satisfy the followingrequirements:7.3.1 Testing Machine ConfigurationThe test
41、ing 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. Thevelocity of the movable head shall be capable of beingr
42、egulated in accordance with 11.6.7.3.3 Load IndicatorThe 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 acc
43、uracy over the force range(s) ofinterest of within 61 % of the indicated value.7.3.4 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 acc
44、eptable tomeasure the displacement of the movable head using a LVDT,compressometer or similar device with 61 % precision ondisplacement.Atransducer 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 bottom lo
45、adingplaten, and a transducer rod is inserted through the hole and thehoneycomb core test specimen, such that it contacts the upperloading platen. If such an apparatus is used, the transducer roddiameter shall be no greater than the cell size, so that thetransducer rod can be inserted through the te
46、st specimenwithout distorting the core cell geometry.FIG. 1 Platen with Transducer and Rod SetupFIG. 2 Close-up of Specimen Between Loading PlatensBeing CrushedD 7336/D 7336M 0737.4 Conditioning ChamberWhen conditioning materialsat non-laboratory environments, a temperature/vapor-levelcontrolled env
47、ironmental 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 intervals.7.5
48、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.7.6 Pre-Crushing Devi
49、ceCrush strength and stroke datafor pre-crushed honeycomb core materials typically displaygreater uniformity than have similar data for non pre-crushedspecimens. Serrated plates have been used successfully aspre-crushing devices for honeycomb core materials; acceptablereference serrated plate configurations are shown in Figs. 3 and4. The pre-crushing device must be capable of providing arelatively uniform pre-crush depth of 1.0 6 0.5 mm0.03 6 0.02 in.8. Sampling and Test Specimens8.1 SamplingTest at least five specimens per test condi-tion un
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