1、Designation:D7336/D7336M07 Designation: D7336/D7336M 12Standard 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 adop
2、tion or, in the case of revision, 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 absorption properties (com
3、pressive crush stress and crush stroke) ofhoneycomb sandwich core materials. These properties are usually determined for design purposes in a direction normal to the planeof facings as the honeycomb core material would be placed in a structural sandwich construction.1.2 Permissible core materials ar
4、e limited to those in honeycomb form.1.3 This test method is not intended for use in crush testing of stabilized honeycomb core materials (for which the edges facingplane surfaces of the honeycomb core material are dipped in resin to resist local crushing) or sandwich specimens (for whichfacings are
5、 bonded to the honeycomb core material).1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text theinch-pound units are shown in brackets. The values stated in each system aremay not be exact equivalents; therefore, each systemmustshall
6、 be used independently of the other. Combining values from the two systems may result in non-conformance with thestandard.1.4.1 Within the text the inch-pound units are shown in brackets.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is
7、the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C271/C271M Test Method for Density of Sandwich Core MaterialsC274 Terminology of Struct
8、ural Sandwich ConstructionsD883 Terminology Relating to PlasticsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix CompositeMaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology
9、Relating to Methods of Mechanical TestingE18 Test Methods for Rockwell Hardness of Metallic MaterialsE122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot orProcessE177 Practice for Use of the Terms Precision and Bias in ASTM Test
10、MethodsE456 Terminology Relating to Quality and StatisticsE1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in DatabasesE1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in DatabasesE1471 Guide for Identification of Fibers, Fil
11、lers, and Core Materials in Computerized Material Property Databases3. Terminology3.1 DefinitionsTerminology D3878 defines terms relating to high-modulus fibers and their composites. Terminology C2741This test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and is the d
12、irect responsibility of Subcommittee D30.09 on SandwichConstruction.Current edition approved May 1, 2007. Published May 2007. DOI: 10.1520/D7336_D7336M-07.Current edition approved April 1, 2012. Published May 2012. Originally approved in 2007. Last previous edition approved in 2007 as D7336/D7336M 0
13、7. DOI:10.1520/D7336_D7336M-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.1This document is not an AST
14、M standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In al
15、l cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.defines terms relating to structural sandwich constructions. Terminology D8
16、83 defines terms relating to plastics. Terminology E6defines terms relating to mechanical testing. Terminology E456 and Practice E177 define terms relating to statistics. In the eventof a conflict between terms, Terminology D3878 shall have precedence over the other terminologies.NOTE 1If the term r
17、epresents a physical quantity, its analytical dimensions are stated immediately following the term (or letter symbol) infundamental dimension form, using the following ASTM standard symbology for fundamental dimensions, shown within square brackets: M for mass,L for length, T for time, u for thermod
18、ynamic temperature, and nd for non-dimensional quantities. Use of these symbols is restricted to analyticaldimensions when used with square brackets, as the symbols may 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 h
19、oneycomb core, the distance between two parallel and opposite cell walls at node bond areas,measured transverse to the ribbon direction.3.2.2 node bond area, nin a honeycomb core, the area between two cells at which the component walls of the cells are bondedor attached.3.3 Symbols:A = cross-section
20、al area of a test specimen prior to compressive crush testingCV = coefficient of variation statistic of a sample population for a given property (in percent)KA= initial chord slope of the force versus displacement/deformation curveKB= post-crush slope of the force versus displacement/deformation cur
21、vePcr= average force carried by test specimen during compressive crushingscr= crush stroke in percentSn-1= standard deviation statistic of a sample population for a given propertyti= thickness of a test specimen prior to compressive crush testingx1= test result for an individual specimen from the sa
22、mple population for a given propertyx = mean or average (estimate of mean) of a sample population for a given propertyd = recorded displacement/deflectiondA= displacement/deflection at which the initial chord slope intersects the displacement/deformation axisdB= displacement/deflection at which the
23、post-crushing slope equals the initial chord slopedcr= crush strokeD = normalized displacement/deflectionscr= average compressive crush stress4. Summary of Test Method4.1 This test method consists of subjecting a sandwich honeycomb core material to a uniaxial compressive force normal to theplane of
24、the facings as the honeycomb core material would be placed in a structural sandwich construction. The force is transmittedto the sandwich honeycomb core material using loading platens attached to the testing machine. Compressive force is applied pastthe initial failure force, such that the honeycomb
25、 core material is crushed under continuous displacement of the loading platens.Force versus loading platen displacement data are recorded and used to determine the crush stress and crush stroke.5. Significance and Use5.1 Sandwich honeycomb core materials are used extensively in energy absorption app
26、lications, due to their ability to sustaincompressive loading while being crushed. Proper design of energy absorption devices utilizing sandwich honeycomb corematerials requires knowledge of the compressive crush stress and crush stroke properties of the honeycomb core material.5.2 The procedures co
27、ntained within this standard are intended to assess the crush stress and crush stroke properties of thesandwich honeycomb core material under static compressive loading. The dynamic crush stress of the honeycomb core materialmay vary from that measured under static loading, depending upon factors su
28、ch as honeycomb core material thickness, corematerial density, impact velocity, etc.5.3 This test method provides a standard method of obtaining the compressive crush stress and crush stroke for sandwichhoneycomb core material structural design properties, material specifications, research and devel
29、opment applications, and qualityassurance.5.4 This test method is not intended for use in crush testing of stabilized honeycomb core materials (for which the edgesfacingplane surfaces of the honeycomb core material are dipped in resin to resist local crushing) or sandwich specimens (for whichfacings
30、 are bonded to the honeycomb core material).5.5 Factors that influence the compressive crush stress and crush stroke and shall therefore be reported include the following:honeycomb core material, methods of material fabrication, core material geometry (nominal cell size), core material density,speci
31、men geometry, specimen preparation, specimen conditioning, environment of testing, specimen alignment, pre-crushprocedure, pre-crush depth, loading procedure, and speed of testing.6. Interferences6.1 Material and Specimen PreparationPoor material fabrication practices and damage induced by improper
32、specimenD7336/D7336M 122machining are known causes of high data scatter in composites and sandwich structures in general. Important aspects of sandwichcore material specimen preparation that contribute to data scatter include the existence of joints, voids or other core materialdiscontinuities, out-
33、of-plane curvature/warpage, and surface roughness.6.2 System AlignmentNon-uniform loading over the surface of the test specimen may cause premature or uneven crushing.This may occur as a result from non-uniform thickness, failing to locate the specimen concentrically in the fixture, or system orfixt
34、ure misalignment.6.3 GeometrySpecific geometric factors that affect compressive crush stress and crush stroke include honeycomb corematerial cell geometry, core material thickness, and specimen shape (square or circular). Thicker specimens are generally desirable,as the crush stroke is greater for t
35、hick specimens compared to thin specimens.6.4 Pre-CrushingIt is recommended to pre-crush honeycomb core material specimens prior to test, as historical crush forceversus displacement data for pre-crushed specimens have displayed greater uniformity (consistency of the crush force level forvarying cru
36、sh stroke) than have similar data for non pre-crushed specimens. If tests are performed using analog equipment torecord force versus displacement data, pre-crushing may be necessary to ensure the crush force is recorded on a high sensitivityforce scale (if not pre-crushed, the peak force to initiall
37、y fail the specimen may be substantially higher than the crush force).Pre-crushing also aids interpretation of force versus displacement data and calculation of crush stroke values. Results are affectedby the pre-crush depth and uniformity of pre-crushing.6.5 EnvironmentResults are affected by the e
38、nvironmental conditions under which specimens are conditioned, as well as theconditions under which the tests are conducted. Specimens tested in various environments can exhibit significant differences inboth crush stress and crush stroke. Critical environments must be assessed independently for eac
39、h honeycomb core material tested.7. Apparatus7.1 Micrometers and CalipersA micrometer having a flat anvil interface, or a caliper of suitable size, shall be used. Theaccuracy of the instrument(s) shall be suitable for reading to within 1 % of the sample length and width (or diameter) and thickness.F
40、or typical specimen geometries, an instrument with an accuracy of 6250 m 60.010 in. is desirable for thickness, length andwidth (or diameter) measurement.7.2 Loading PlatensForce shall be introduced into the specimen using fixed flat platens (58 HRC minimum as specified inTest Methods E18). One plat
41、en may be of the spherical seat (self-aligning) type, if it is capable of being locked in a fixed positiononce the platen has contacted and aligned with the specimen. The platens shall be well-aligned (centered with respect to the drivemechanism loading train) and shall not apply eccentric forces.As
42、atisfactory type of apparatus is shown in Figs. 1 and 2. The platensurfaces shall extend beyond the test specimen periphery. If the platens are not sufficiently hardened, or simply to protect the platensurfaces, a hardened plate (with parallel surfaces) can be inserted between each end of the specim
43、en and the corresponding platen.7.3 Testing MachineThe testing machine shall be in accordance with Practices E4 and shall satisfy the followingrequirements:7.3.1 Testing Machine ConfigurationThe testing machine shall have both an essentially stationary head and a movable head.7.3.2 Drive MechanismTh
44、e testing machine drive mechanism shall be capable of imparting to the movable head a controlledvelocity with respect to the stationary head. The velocity of the movable head shall be capable of being regulated in accordancewith 11.6.7.3.3 Load IndicatorThe testing machine load-sensing device shall
45、be capable of indicating the total force being carried bythe test specimen. This device shall be essentially free from inertia lag at the specified rate of testing and shall indicate the forcewith an accuracy over the force range(s) of interest of within 61 % of the indicated value.7.3.4 Crosshead D
46、isplacement IndicatorThe testing machine shall be capable of monitoring and recording the crossheaddisplacement (stroke) with a precision of at least 61 %. If machine compliance is significant, it is acceptable to measure thedisplacement of the movable head using a LVDT, compressometer or similar de
47、vice with 61 % precision on displacement. Atransducer and rod setup, shown in Figs. 1 and 2, has been found to work satisfactorily. In the example shown, a small hole isdrilled in the center of the bottom loading platen, and a transducer rod is inserted through the hole and the honeycomb core testsp
48、ecimen, such that it contacts the upper loading platen. If such an apparatus is used, the transducer rod diameter shall be no greaterthan the cell size, so that the transducer rod can be inserted through the test specimen without distorting the core cell geometry.7.4 Conditioning ChamberWhen conditi
49、oning materials at non-laboratory environments, a temperature/vapor-level con-trolled environmental conditioning chamber is required that shall be capable of maintaining the required temperature to within63C 65F and the required relative humidity level to within 63 %. Chamber conditions shall be monitored either on anautomated continuous basis or on a manual basis at regular intervals.7.5 Environmental Test ChamberAn environmental test chamber is required for test environments other than ambient testinglaboratory conditions. This chamber shall b
