1、Designation: D 6790 02 (Reapproved 2007)Standard Test Method forDetermining Poissons Ratio of Honeycomb Cores1This standard is issued under the fixed designation D 6790; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the hon-eycomb Poissons ratio from the anticlastic curvature radii, seeFi
3、g. 1.1.2 The values stated in SI units are to be regarded as thestandard. The inch-pound units given may be approximate.1.3 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-pr
4、iate safety and health practices and determine the applica-bility 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 Constructions3. Terminology3.1 DefinitionsTermino
5、logy C 274 defines terms relatingto sandwich constructions.3.2 Symbols:c = chord measurementd = depth measurementRa= anticlastic curvature radiusRc= cylinder radius = Poissons ratio4. Summary of Test Method4.1 The Poissons ratio of honeycomb core is determined bybending the core around a cylinder an
6、d taking measurements ofthe anticlastic curvature that occurs.5. Significance and Use5.1 Certain sandwich panel finite element programs requirethe Poissons ratio of the honeycomb core. It is not possible tomeasure the honeycombs Poissons ratio by standard methods.6. Interference6.1 The test method s
7、hown here is one means of obtainingthe Poissons ratio of honeycomb. However, this test methodhas not been widely used, and it is in its conceptual stage.7. Apparatus7.1 Cylinders, of various diameters. A 610 mm (24 in.)diameter cylinder is recommended.7.2 Scale, capable of measuring accurately to 0.
8、25 mm(0.01 in.).8. Sampling and Test Specimens8.1 Test at least five specimens per test condition unlessvalid results can be gained through the use of fewer specimens,such as in the case of a designed experiment.8.2 The test specimen shall be square. The length and widthshould be great enough to obt
9、ain an anticlastic curvature when1This 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 May 1, 2007. Published June 2007. Originallyapproved in 2002. Last previou
10、s edition approved in 2002 as D 6790 - 02.2For 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.FIG. 1 Anticlastic
11、Curvature1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.the specimen is bent over the cylinder. A specimen size of 300by 300 mm (12 by 12 in.) is recommended.8.3 Various core thicknesses should be tested. A corethickness of 12.7 mm
12、(0.50 in.) is recommended as a startingthickness.9. Calibration9.1 The accuracy of all measuring equipment shall havecertified calibrations that are current at the time of use of theequipment.10. Conditioning10.1 When the physical properties of the core material areaffected by moisture, bring the te
13、st specimens to constantweight (61 %) before testing, preferably in a conditioningroom with temperature and humidity control and make thetests, preferably, in a room under the same condition. Atemperature of 23 6 3C (73 6 5F) and a relative humidity of50 6 5 % are recommended.11. Procedure11.1 Deter
14、mine the plan dimensions of the specimens in mm(in.) to a precision of 60.5 %.11.2 Measure the thickness of the specimens in mm (in.) tothe nearest 0.025 mm (0.001 in.).11.3 Bend the honeycomb core specimen around the cylin-der of known diameter, making sure all the specimen surfacealong its centerl
15、ine is in contact with the cylinder.11.4 Place a straightedge across the specimen and measurethe distance as shown in Fig. 2 while the specimen is bentaround the cylinder.12. Calculations12.1 Calculate the densities of the specimens using TestMethod C 271.12.2 Calculate the anticlastic curvature rad
16、ius and Poissonsratio of the specimens as follows:Ra54 d21 c28 d 5RcRawhere: (see Fig. 2) = Poissons ratio,Ra= anticlastic curvature radius,Rc= cylinder radius,c = chord measurement, andd = depth measurement.13. Report13.1 The report shall include the following:13.1.1 Description of the test specime
17、ns; core material, cellsize, and density,13.1.2 Dimensions of the test specimens and which coredirection was bent over the cylinder, L or W,13.1.3 Specimens conditioning, if any, and13.1.4 The Poissons ratios; individual values, average, andstandard deviation.14. Precision and Bias14.1 PrecisionThe
18、data required for the development of aprecision statement are not available for this test method.14.2 BiasBias cannot be determined for this test methodas no acceptable reference material exists.15. Keywords15.1 core; honeycomb; Poissons ratioFIG. 2 MeasurementsD 6790 02 (2007)2ASTM International ta
19、kes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own r
20、esponsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addre
21、ssed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at t
22、he address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 6790 02 (2007)3
