1、Designation: C272/C272M 18Standard Test Method forWater Absorption of Core Materials for SandwichConstructions1This standard is issued under the fixed designation C272/C272M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year
2、 of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test method covers the
3、determination of the relativeamount of water absorption by various types of sandwichconstruction core materials when immersed in water, or whensubjected to a high relative humidity environment. Permissiblecore material forms include those with continuous bondingsurfaces (such as balsa wood and foams
4、) as well as those withdiscontinuous bonding surfaces (such as honeycomb).1.2 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 othe
5、r. Combiningvalues from the two systems may result in non-conformancewith the standard.1.2.1 Within the text the inch-pound units are shown inbrackets.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
6、 standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decis
7、ion on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD1193 Specification for Reagent WaterD3878 Te
8、rminology for Composite MaterialsE122 Practice for Calculating Sample Size to Estimate, WithSpecified 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. Terminolo
9、gy3.1 DefinitionsTerminology D3878 defines terms relatingto high-modulus fibers and their composites, as well as termsrelating to sandwich constructions. Terminology D883 definesterms relating to plastics. Terminology E456 and Practice E177define terms relating to statistics. In the event of a confl
10、ictbetween terms, Terminology D3878 shall have precedenceover the other terminologies.3.2 Symbols:3.2.1 CVcoefficient of variation statistic of a samplepopulation for a given property (in percent).3.2.2 Dpre-immersion mass of a test specimen.3.2.3 hheight of a test specimen.3.2.4 llength of a test s
11、pecimen.3.2.5 Sn1standard deviation statistic of a sample popula-tion for a given property.3.2.6 x1test result for an individual specimen from thesample population for a given property.3.2.7 xmean or average (estimate of mean) of a samplepopulation for a given property.3.2.8 Vvolume of a test specim
12、en.3.2.9 wwidth of a test specimen.3.2.10 Wmass of a test specimen.4. Summary of Test Method4.1 This test method consists of exposing sandwich corespecimen to a defined moisture condition, and determining theamount of water absorbed by measuring the mass increase inthe specimen.1This test method is
13、under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.09 onSandwich Construction.Current edition approved Aug. 1, 2018. Published August 2018. Originallyapproved in 1951. Last previous edition approved in 2016 as C272 16. DOI:10.1520/
14、C0272_C0272M-18.2For 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.Copyright ASTM International, 100 Barr Harbor
15、 Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendation
16、s issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.15. Significance and Use5.1 Absorbed water affects the characteristic properties ofsandwich core materials, such as electrical properties (forexample, dielectric constant, loss tangent, and electrical resis-tance) a
17、nd mechanical properties (for example, strength andmodulus). The mass of absorbed water may also affect thebehavior of sandwich structures. It should be noted that in asandwich panel the presence of facings bonded on two sides ofthe core may affect the amount of water absorbed by the core.5.2 This t
18、est method provides a standard method of obtain-ing sandwich core moisture absorption data for designproperties, material specifications, research and developmentapplications, and quality assurance.5.3 Factors that influence the water absorption and shalltherefore be reported include the following:
19、core material,methods of material fabrication, core geometry (honeycombcell size, honeycomb cell wall thickness, foam pore size, etc.),specimen geometry, specimen preparation, methods of massand dimensional measurement, specimen conditioning, andmoisture content during mass and dimensional measureme
20、nts.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 specimen preparation that contribute
21、 to datascatter include the existence of joints, voids or other corediscontinuities, out-of-plane curvature, and surface roughness.Cracks in the specimen and rough surfaces can increase theapparent water absorption.6.2 Surface WaterSome core materials tend to collectwater on the surfaces or trap wat
22、er in corners, and, if notremoved will give incorrect results.6.3 EnvironmentResults are affected by the environmentalconditions under which specimens are conditioned.7. Apparatus7.1 Analytical Balance or Weighing ScaleAn analyticalbalance or weighing scale is required that is capable ofmeasuring th
23、e sample weight accurately to 0.01 %.7.2 Oven:7.2.1 Circulating Air OvenFor ProcedureAand C tests, anair-circulating oven is required that shall be capable of main-taining the required uniform temperatures to within 63C65F.7.2.2 Circulating Air Vacuum OvenFor Procedure B tests,an air-circulating ove
24、n is required that shall be capable ofmaintaining the required uniform temperatures to within 63C65F, shall be capable of achieving full vacuum, and shallhave a drying device on the air inlet line.7.3 DesiccatorA clean, dry desiccator is required; speci-mens being oven-dried shall be brought to labo
25、ratory tempera-ture following removal from the oven.7.4 Humidity ChamberA humidity chamber is requiredthat shall be capable of maintaining uniform relative humiditywith an accuracy of 65 % and a uniform temperature with anaccuracy of 63C 65F.7.5 The water used in this test method shall be distilledw
26、ater (Specification D1193, Type IV reagent water) or deion-ized water.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. For statisticallysignificant data
27、, consult the procedures outlined in PracticeE122. Report the method of sampling.8.2 GeometryTest specimens shall have a square or rect-angular cross-section. The recommended specimen size is75 mm 3.0 in. in length by 75 mm 3.0 in. in width by13 mm 0.5 in. in thickness.NOTE 1The specimens cross-sect
28、ional area (length times width) isdefined in the facing plane, in regard to the orientation that the core wouldbe placed in a structural sandwich construction. For example, for ahoneycomb core the cross-sectional area is defined in the plane of thecells, which is perpendicular to the orientation of
29、the cell walls.8.3 Specimen Preparation and MachiningMachine, saw,or shear the test specimens from the core sample so as to havesmooth surfaces that are free from cracks and facing planesurfaces that are parallel to each other and perpendicular to thesides of the specimen. Record and report the spec
30、imen cuttingpreparation method.8.4 LabelingLabel the test specimens so that they will bedistinct from each other and traceable back to the sheet oforigin, and will neither influence the test nor be affected by it.9. Calibration9.1 The accuracy of all measuring equipment shall havecertified calibrati
31、ons that are current at the time of use of theequipment.10. Pre-Test Conditioning10.1 Oven dry the specimens as follows:10.1.1 For materials whose water absorption value would beaffected by temperatures up to approximately 110C 230F,dry the specimens in an oven for 24 h at 50 6 3C 120 6 5F,cool in a
32、 desiccator to room temperature, remove, and imme-diately weigh and record the mass. After weighing, immedi-ately place the specimens in the water or humidity chamber.10.1.2 For materials whose water absorption value has beenshown not to be affected by temperatures up to 110C 230F,dry the specimens
33、in an oven for2hat1056 3C 225 6 5F,cool in a desiccator to room temperature, remove, and imme-diately weigh and record the mass. After weighing, immedi-ately place the specimens in the water or humidity chamber.10.1.3 For specimens to be conditioned using Procedure Bbelow, dry the specimens per 10.1
34、.1 or 10.1.2 in a vacuumdrying oven without application of vacuum. After the timeperiods specified above, apply full vacuum for 30 min toremove remaining traces of moisture. When reducing thevacuum level, ambient venting air should be passed through acalcium sulfate desiccant or suitable alternate i
35、n-line trap.C272/C272M 18210.2 In the case of a new material of which the waterabsorption properties are not known, conditioning separatespecimens in accordance with 10.1.1 and 10.1.2, followed bythe specified procedure below is recommended until sufficientexperience on the effect of temperature is
36、achieved to indicatethe selection of the most satisfactory method.11. Procedure11.1 Parameters to Be Specified Before Test:11.1.1 The specimen sampling method and specimen geom-etry.11.1.2 The properties and data reporting format desired.NOTE 2Determine specific material property, accuracy, and data
37、reporting requirements prior to test for proper selection of apparatus.11.1.3 The pre-test conditioning method and parameters.11.1.4 The balance or weighing scale measurement accu-racy.11.1.5 The conditioning procedure (A, B or C) to be used.11.2 General Instructions:11.2.1 Report any deviations fro
38、m this test method, whetherintentional or inadvertent.11.2.2 Following final specimen machining, but beforeconditioning and testing, measure the specimen length, widthand thickness. The accuracy of these measurements shall bewithin 0.5 % of the dimension. Measure the specimen length,width and thickn
39、ess with an accuracy of 60.025 mm60.001 in. Record the dimensions to three significant figuresin units of millimetres inches.11.3 Condition the specimens using one of the followingconditioning environments, as specified by the test requestor:11.3.1 Procedure A Twenty-Four-Hour ImmersionImmerse the s
40、pecimens in a container horizontally under 25mm 1.0 in. minimum head of water for 24 + 1,0h,maintained at a temperature of 23 6 3C 73 6 5F. Corematerials that float should be held under water by a loose netor other means which will not greatly affect the exposedsurface area of the specimen.11.3.1.1
41、Remove the specimens from conditioning, shakevigorously and wipe off all surface water with a dry cloth untilno visible water is present. For materials that tend to collectwater on the surfaces or trap water in corners, dip the specimenin isopropyl alcohol, shake vigorously, allow the alcohol toevap
42、orate, and immediately weigh and record the mass.11.3.1.2 Re-measure the specimen length, width and thick-ness as in 11.2.2.11.3.1.3 Weigh and record the mass of each specimen ingrams to a precision of 60.01 %.11.3.2 Procedure B Elevated Temperature HumidityThestandard conditioning environment shall
43、 be 70 6 3C 160 65F and 85 6 5 % relative humidity for 30 days. Othertemperatures, relative humidities, and lengths of time can beused if specified by the test requestor but must be reported. Thespecimens shall be placed in the conditioning chamber with the75 by 75 mm 3.0 by 3.0 in. planes in the ve
44、rtical position andthe ends sitting on an open base (such as a screen or perforatedmaterial). After conditioning, allow the specimens to cool toroom temperature.11.3.2.1 Remove the specimens from conditioning, shakevigorously and wipe off all surface water with a dry cloth untilno visible water is p
45、resent. For materials that tend to collectwater on the surfaces or trap water in corners, dip the specimenin isopropyl alcohol, shake vigorously, allow the alcohol toevaporate, and immediately weigh and record the mass.11.3.2.2 Re-measure the specimen length, width and thick-ness as in 11.2.2.11.3.2
46、.3 Weigh and record the mass of each specimen ingrams to a precision of 60.01 %.11.3.3 Procedure C Maximum Percent Mass GainImmerse the specimens in a container as in Procedure A for 48+1,0h.11.3.3.1 Remove the specimens from conditioning, shakevigorously and wipe off all surface water with a dry cl
47、oth untilno visible water is present. For materials that tend to collectwater on the surfaces or trap water in corners, dip the specimenin isopropyl alcohol, shake vigorously, allow the alcohol toevaporate, and immediately weigh and record the mass.11.3.3.2 Re-measure the specimen length, width and
48、thick-ness as in 11.2.2.11.3.3.3 Weigh and record the mass of each specimen ingrams to a precision of 60.01 %.11.3.3.4 Place the specimens back into the water and repeatthis process until the mass gain after the last 48-h interval isless than 2 % of the entire mass gain of all the previousintervals.
49、11.4 Surface Water CorrectionA typical indication thatsurface water is present on the specimen is a significantly orrandomly, or both, varying moisture content versus time. Whensurface water on the specimens presents such problems,determine the amount of surface water left on the specimensusing the following procedure:11.4.1 Prepare five control samples identical to the testspecimens.11.4.2 Perform the same pre-test conditioning per 10.1 asused for the test specimens.11.4.3 Weigh and record the mass o
