1、Designation: D7336/D7336M 16Standard Test Method forStatic Energy Absorption Properties of HoneycombSandwich Core Materials1This standard is issued under the fixed designation D7336/D7336M; the number immediately following the designation indicates theyear of original adoption or, in the case of rev
2、ision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method determines the static energy absorptionproperties (compressive crush stress and cr
3、ush 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-eyco
4、mb form.1.3 This test method is not intended for use in crush testingof stabilized honeycomb core materials (for which the facingplane surfaces of the honeycomb core material are dipped inresin to resist local crushing) or sandwich specimens (forwhich facings are bonded to the honeycomb core materia
5、l).1.4 The values 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-conformancewi
6、th the standard.1.4.1 Within the text the inch-pound units are shown inbrackets.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 det
7、ermine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 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-e
8、rties and Equilibrium Conditioning of Polymer MatrixComposite MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE18 Test Methods for Rockwell Hardness of Metallic Ma-terialsE122 Practice for Calculating Sample Size to Estimate, Wi
9、thSpecified Precision, the Average for a Characteristic 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
10、composites, as well as termsrelating to sandwich 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
11、D3878 shall have prece-dence over the other terminologies.NOTE 1If the term represents a physical quantity, its analyticaldimensions are stated immediately following the term (or letter symbol) infundamental dimension form, using the following ASTM standard sym-bology for fundamental dimensions, sho
12、wn within square brackets: Mfor mass, L for length, T for time, for thermodynamic temperature,and nd for non-dimensional quantities. Use of these symbols is restrictedto analytical dimensions when used with square brackets, as the symbolsmay have other definitions when used without the brackets.3.2
13、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, nin a honeycomb core, the areabetween two cells at which the component
14、 walls of the cells arebonded or attached.3.3 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 April 1, 2016. Published April 2016. Originallyapprov
15、ed in 2007. Last previous edition approved in 2012 as D7336/D7336M 12.DOI: 10.1520/D7336_D7336M-16.2For 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 Doc
16、ument Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1A = cross-sectional area of a test specimen prior to com-pressive crush testingCV = coefficient of variation statistic of a sample populationfor a g
17、iven property (in percent)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 stat
18、istic of a sample population fora given propertyti= thickness of a test specimen prior to compressivecrush testingx1= test result for an individual specimen from the samplepopulation for a given propertyx = mean or average (estimate of mean) of a samplepopulation for a given property = recorded disp
19、lacement/deflectionA= displacement/deflection at which the initial chordslope intersects the displacement/deformation axisB= displacement/deflection at which the post-crushingslope equals the initial chord slopecr= crush stroke = normalized displacement/deflectioncr= average compressive crush stress
20、4. Summary of Test Method4.1 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 honeyc
21、omb corematerial using 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
22、to determinethe crush 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 hon
23、ey-comb core materials 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 stati
24、c compres-sive loading. 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 t
25、he compressive crush 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
26、which the facingplane surfaces of the honeycomb core material are dipped inresin to resist local crushing) or sandwich specimens (forwhich facings are bonded to the honeycomb core material).5.5 Factors that influence the compressive crush stress andcrush stroke and shall therefore be reported includ
27、e thefollowing: honeycomb core material, 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, loadingprocedure,
28、 and speed of testing.6. Interferences6.1 Material and Specimen PreparationPoor material fab-rication practices and damage induced by improper specimenmachining are known causes of high data scatter in compositesand sandwich structures in general. Important aspects ofsandwich core material specimen
29、preparation that contribute todata scatter include the existence of joints, voids or other corematerial discontinuities, out-of-plane curvature/warpage, andsurface roughness.6.2 System AlignmentNon-uniform loading over the sur-face of the test specimen may cause premature or unevencrushing. This may
30、 occur as a result from non-uniformthickness, 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 thick
31、ness, and specimenshape (square or 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 displa
32、cement data for pre-crushed specimens 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 necess
33、ary to ensure the crush force is recordedon 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.
34、 Results are affected by the pre-crush depth and unifor-mity of pre-crushing.6.5 EnvironmentResults are affected by the environmentalconditions under which specimens are conditioned, as well asthe conditions under which the tests are conducted. SpecimensD7336/D7336M 162tested in various environments
35、 can exhibit significant differ-ences in both crush stress and crush stroke. Critical environ-ments must be assessed independently for each honeycombcore material tested.7. Apparatus7.1 Micrometers and CalipersA micrometer having a flatanvil interface, or a caliper of suitable size, shall be used. T
36、heaccuracy of the instrument(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 forthickness, length and width (or diameter) measurement.7.2 Loading
37、PlatensForce shall be introduced 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. Th
38、e platens shall be well-aligned(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,
39、 or simply to protect the platensurfaces, 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 in ac-cordance with Practices E4 and shall satisfy the followingrequirements:7.3.1 Testing
40、 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. Thevelocity of the movable h
41、ead shall be capable of beingregulated 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 shall
42、indicate the force with an accuracy 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 compli
43、ance is significant, it is acceptable tomeasure the displacement of the movable head using a 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 drille
44、d in the center of the bottom loadingplaten, 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 ro
45、d can be inserted through the test specimenwithout distorting the core cell geometry.7.4 Conditioning ChamberWhen conditioning materialsat non-laboratory environments, a temperature/vapor-levelcontrolled environmental conditioning chamber is required thatshall be capable of maintaining the required
46、temperature towithin 63C 65F and the required relative humidity levelFIG. 1 Platen with Transducer and Rod SetupFIG. 2 Close-up of Specimen Between Loading PlatensBeing CrushedD7336/D7336M 163to within 63 %. Chamber conditions shall be monitored eitheron an automated continuous basis or on a manual
47、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 ofmaintaining the gage section of the test specimen at therequired test environment during the mechani
48、cal test.7.6 Pre-Crushing DeviceCrush 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; acceptabler
49、eference 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 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 sampling.8.2 GeometryTest specimens shall h
