1、Designation: D6772 02 (Reapproved 2007)D6772/D6772M 15Standard Test Method forDimensional Stability of Sandwich Core Materials1This standard is issued under the fixed designation D6772;D6772/D6772M; the number immediately following the designation indicatesthe year of original adoption or, in the ca
2、se 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 covers the determination of the sandwich core dimensional stability in th
3、e two plan dimensions.1.2 The values stated in either SI units or inch-pound units are to be regarded separately as the standard. The inch-pound unitsgiven may be approximate.values stated in each system may not be exact equivalents; therefore, each system shall be usedindependently of the other. Co
4、mbining values from the two systems may result in non-conformance with the standard.1.2.1 Within the text, the inch-pound units are shown in brackets.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this
5、 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 Structural Sandwich ConstructionsD883 Termi
6、nology Relating to PlasticsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix CompositeMaterialsE122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characte
7、ristic of a Lot orProcessE177 Practice for Use of the Terms Precision and Bias in ASTM Test 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 Fi
8、ber-Reinforced Composite Materials in Databases3. Terminology3.1 DefinitionsTerminology D3878 defines terms relating to high-modulus fibers and their composites. Terminology C274defines terms relating to structural sandwich constructions. Terminology D883 defines terms relating to plastics. Terminol
9、ogy E456and Practice E177 define terms relating to statistics. In the event of a conflict between terms, Terminology D3878 shall haveprecedence over the other terminologies.3.2 Symbols:Li = initial measured dimensionLf = final measured dimension3.2 Symbols:3.2.1 CVcoefficient of variation statistic
10、of a sample population for a given property (in percent)3.2.2 Li initial (pre-test) measured dimension1 This test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.09 on SandwichConstruction.Current edition approved May
11、 1, 2007April 1, 2015. Published June 2007April 2014. Originally approved in 2002. Last previous edition approved in 20022007 asD6772 - 02.D6772 - 02(2007). DOI: 10.1520/D6772-02R07.10.1520/D6772_D6772M-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer S
12、ervice at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the prev
13、ious version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM In
14、ternational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.3 Lfpost-heating measured dimension3.2.4 Sn-1standard deviation statistic of a sample population for a given property3.2.5 xItest result for an individual specimen from the sample population for a gi
15、ven property3.2.6 xmean or average (estimate of mean) of a sample population for a given property4. Summary of Test Method4.1 A This test method consists of placing a small piece of honeycomb is placedsandwich core material in an elevatedtemperature environment and after for a specified period of ti
16、me. After cooling, the dimensional changes in the planplanardimensions are measured and compared to the initial measurements. measurements taken prior to thermal exposure, bothimmediately after heating and after re-conditioning. A typical honeycomb core specimen is shown in Fig. 1.5. Significance an
17、d Use5.1 Sandwich panel cores may change planplanar dimensions when heated. This phenomenon can be associated with the effectsof heating upon the core material itself, as well as changes in core moisture content resulting from the heating cycle. It is prudentto know if this may be a problem with the
18、 problematic with regard to the intended final part dimensions.5.2 This test method provides a standard method of characterizing the dimensional stability of sandwich core materials fordesign properties, material specifications, research and development applications, and quality assurance.5.3 Factor
19、s that influence dimensional stability of sandwich core materials and shall therefore be reported include the following:core material, methods of material fabrication, core geometry, core thickness, core thickness uniformity, cell wall thickness,specimen geometry, specimen preparation, heating and c
20、ooling environments (including temperatures and humidity levels), andspecimen conditioning (both prior to and after heating).6. Interferences6.1 Material and Specimen PreparationIf oven size is limited, smaller specimens may be used.Poor material fabricationpractices and damage induced by improper s
21、pecimen machining are known causes of high data scatter for sandwich cores.Important aspects of sandwich core specimen preparation that contribute to data scatter include the existence of joints, voids orother core discontinuities, out-of-plane curvature, and surface roughness.6.2 Core GeometryCore-
22、specific geometric factors that affect dimensional stability include core cell size, uniformity of corecell geometry, core cell wall thickness, core cell wall thickness uniformity, core thickness, and core thickness uniformity.6.3 EnvironmentIf the specimen warps, flatten it out while making the mea
23、surements.Results are affected by theenvironmental conditions (including both temperatures and humidity levels) under which specimens are pre-conditioned, theelevated temperature exposure environment, the re-conditioning environment after heating, as well as the conditions under whichthe planar dime
24、nsional measurements are taken. Specimens tested in various environments can exhibit differences in dimensionalstability.7. Apparatus7.1 Oven, Micrometers and Caliperscapable of maintaining a controlled temperature 63C (65F). A micrometer having aflat anvil interface, or a caliper of suitable size,
25、shall be used. The accuracy of the instrument(s) shall be suitable for reading towithin 0.5 % of the sample length, width and thickness. For typical specimen geometries, an instrument with an accuracy of60.025 mm 60.001 in. is desirable for thickness measurement, whereas an instrument with an accura
26、cy of 60.25 mm 60.01in. is desirable for length and width measurement.FIG. 1 Dimensional Stability SpecimenD6772/D6772M 1527.2 Scale, Balance or Weighing ScaleAn analytical balance or weighing scale is required that is capable of measuringaccurately to 0.25 mm (0.01 in.).the mass of the core materia
27、l accurately to 60.5 %.7.3 Micrometer, Ovencapable of measuring accurately to 0.025 mm (0.001 in.).An air-circulating oven is required that shallbe capable of maintaining the required temperature to within 63 C 65 F.8. Sampling and Test Specimens8.1 SamplingTest at least five specimens per test cond
28、ition unless valid results can be gained through the use of fewerspecimens, such as in the case of a designed experiment. For statistically significant data, consult the procedures outlined inPractice E122. Report the method of sampling.8.2 The test specimens, if possible, should be approximately 46
29、0 by 915 mm (18 by 36 in.) in plan dimension, and the thicknessshall be approximately 12.7 mm (0.50 in.). For honeycomb cores, the 460-mm (18-in.) dimension is the cores ribbon or Ldirection. Other dimensions can be used, but must be reported.Test Specimens:8.2.1 Core ThicknessStandard test specimen
30、s shall utilize 13 mm 0.50 in. thick core. When assessing dimensional stabilitycharacteristics of core used in specific sandwich constructions, it is recommended to test the actual core thickness used in the endapplication. Tests conducted using non-standard core thicknesses must be designated as su
31、ch, with the core thickness reported withany test results.8.2.2 Core Planar GeometryCore test specimens shall be approximately 450 mm 18 in. by 900 mm 36 in. in the planardimensions. For honeycomb cores, the planar dimension cross section is defined to be in the facing plane (in regard to theorienta
32、tion that the core would be placed in a structural sandwich construction) and is perpendicular to the orientation of the cellwalls. For honeycomb cores the 450-mm 18-in. dimension is the cores ribbon or L direction. Other dimensions can be used, butmust be reported. Smaller specimens may be used if
33、oven size is limited.8.2.3 Core Preparation and MachiningPrepare the core material samples so that the facing plane surfaces are parallel to eachother and perpendicular to the sides of the core. Take precautions when cutting specimens from large sheets of core material toavoid notches, undercuts, ro
34、ugh or uneven surfaces due to inappropriate machining methods. Record and report the core materialspecimen cutting preparation method.8.3 LabelingLabel the test specimens so that they will be distinct from each other and traceable back to the sheet of origin,and will neither influence the test nor b
35、e affected by it.9. Calibration9.1 The accuracy of all measuring equipment shall have certified calibrations that are current at the time of use of the equipment.10. Conditioning10.1 Pre-test environmental conditioning requirements shall be specified by the test requestor. The recommended pre-testco
36、ndition is effective moisture equilibrium at a specific relative humidity as established by Test Method D5229/D5229M; however,if the test requestor does not explicitly specify a pre-test conditioning environment, no conditioning is required and the testspecimens may be tested as prepared.10.2 The pr
37、e-test specimen conditioning process, to include specified environmental exposure levels and resulting moisturecontent, shall be reported with the test data.NOTE 1The term “moisture,” as used in Test Method D5229/D5229M includes not only the vapor of a liquid and its condensate, but the liquid itsel
38、fin large quantities, as for immersion.10.3 If no explicit pre-test conditioning process is performed, the pre-test specimen conditioning process shall be reported as“unconditioned” and the moisture content as “unknown.”10.4 When the physical properties of the material are affected by moisture, brin
39、g the test specimens to constant weight (61 %)before testing. A temperature of 23 6 3C (73 6 5F) and a relative humidity of 50 6 5 % are recommended.Post-heatingenvironmental conditioning requirements shall be specified by the test requestor. The recommended post-heating condition ismoisture content
40、 equivalency to that after pre-test conditioning, which is obtained by re-conditioning the specimen in the sameconditioning environment used for pre-conditioning for an equivalent duration. If the test requestor does not explicitly specify are-conditioning environment, no re-conditioning is required
41、.10.5 The specimen re-conditioning process, to include specified environmental exposure levels, shall be reported with the testdata.10.6 If no explicit re-conditioning process is performed, the specimen re-conditioning process shall be reported as“unconditioned” and the moisture content as “unknown.
42、”11. Procedure11.1 Weigh the specimens in grams (pounds) to a precision of 60.5 %.Parameters to be Specified Before Test:11.1.1 The specimen sampling method, specimen geometry, and conditioning travelers (if required).D6772/D6772M 15311.1.2 The properties and data reporting format desired.NOTE 2Dete
43、rmine specific material property, accuracy, and data reporting requirements prior to test for proper selection of apparatus.11.1.3 The environmental pre-conditioning and re-conditioning parameters.11.2 Determine the plan dimensions of the specimens in millimetres (inches) to a precision of 60.5 %.Ge
44、neral Instructions:11.2.1 Report any deviations from this test method, whether intentional or inadvertent.11.2.2 If core material density is to be reported, then obtain these samples from the same sheet of core material being tested.Density may be evaluated in accordance with Test Method C271/C271M.
45、11.2.3 Following final core material specimen machining, but before conditioning and testing, measure the specimen length andwidth in the planar dimensions at three places. The thickness of the specimen shall be measured at four locations and recorded asthe average of the four measurements. The accu
46、racy of these measurements shall be within 0.5 % of the dimension. Measure thespecimen length and width with an accuracy of 60.25 mm 60.010 in. Measure the specimen thickness with an accuracy of60.025 mm 60.001 in. Record the dimensions to three significant figures in units of millimeters inches. If
47、 the specimen warps,it may be flattened while making the measurements.11.2.4 Determine the mass of the specimen with an accuracy of 60.5 %.11.3 Measure the thickness of Condition the specimens as required. Store the specimens in millimetres (inches) to the nearest0.025 mm (0.001 in.).the conditioned
48、 environment until test time, if the test environment is different than the conditioningenvironment. Record the total time that the specimens are exposed to the conditioning environment.11.4 Following final specimen conditioning, but before testing, re-measure the specimen length, width, and thickne
49、ss as in11.2.3, and re-measure the specimen mass as in 11.2.4.11.5 Mark the specimen in eight locations as shown in Fig. 1. For honeycomb core, it is recommended that the cells be pottedwith a resin at the eight locations and then marked (see Fig. 2). Recommended dimensional locations for the eight markings areshown in Fig. 3.11.6 Measure the dimensions between the marked locations with an accuracy of 60.25 mm 60.010 in. Make threemeasurements in one direction and three measurements in the other direction, as shown in Fig. 3.11
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