1、Designation: C272/C272M 16Standard 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 and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD1193 Specification for Reagent WaterD3878 Terminology for Composite MaterialsE122 P
7、ractice 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. Terminology3.1 DefinitionsTerminology D3878 defi
8、nes 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 conflictbetween terms, Terminology D3878 sha
9、ll 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 specimen.3.2.5 Sn1standard deviation sta
10、tistic 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 specimen.3.2.9 wwidth of a test specimen.3.2.
11、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.5. Significance and Use5.1 Absorbed water affects the charac
12、teristic properties ofsandwich core materials, such as electrical properties (forexample, dielectric constant, loss tangent, and electrical resis-tance) and mechanical properties (for example, strength and1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is
13、the direct responsibility of Subcommittee D30.09 onSandwich Construction.Current edition approved April 1, 2016. Published April 2016. Originallyapproved in 1951. Last previous edition approved in 2012 as C272 12. DOI:10.1520/C0272_C0272M-16.2For referenced ASTM standards, visit the ASTM website, ww
14、w.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 Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1modul
15、us). 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 test method provides a standard method of obtain-ing sand
16、wich 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: core material,methods of material fabrication, core geom
17、etry (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 measurements.6. Interferences6.1 Material and Specimen Preparatio
18、nPoor 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 to datascatter include the existence of joints, voids o
19、r 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 water in corners, and, if notremoved will give incorrect re
20、sults.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 accurately to 0.001 g.7.2 Oven:7.2.1 Circulating Air OvenF
21、or 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 oven is required that shall be capable ofmaintaining the required uniform te
22、mperatures 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 laboratory tempera-ture following removal from the oven.7.4 Humidity ChamberA
23、 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 distilledwater (Specification D1193, Type IV reagent water) or deion-ized water.8.
24、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, consult the procedures outlined in PracticeE122. Report the method of s
25、ampling.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-sectional area (length times width) isdefined in the facing plane, in regard
26、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 the cell walls.8.3 Specimen Preparation and MachiningMachine, saw,or shea
27、r 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 specimen cuttingpreparation method.8.4 LabelingLabel the test specimens so th
28、at 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 calibrations that are current at the time of use of theequipment.10. Pre-Test Cond
29、itioning10.1 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 desiccator to room temperature, remove, and imme-diately weigh and recor
30、d 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 in an oven for2hat1056 3C 225 6 5F,cool in a desiccator to room temperatu
31、re, 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 10.1.1 or 10.1.2 in a vacuumdrying oven without application of vacuum. After
32、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 in-line trap.10.2 In the case of a new material of which the waterabsorpti
33、on 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 achieved to indicatethe selection of the most satisfactory method.C272/C272M 16211. Pro
34、cedure11.1 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 datareporting requirements prior to test for proper selection of apparatus.11
35、.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 from this test method, whetherintentional or inadvertent.11.2.2 Following fi
36、nal 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 thickness with an accuracy of 60.025 mm60.001 in. Record the dimensions to thre
37、e 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 specimens in a container horizontally under 25mm 1.0 in. minimum head of w
38、ater 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 Remove the specimens from conditioning, shakevigorously and wipe off all
39、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 toevaporate, and immediately weigh and record the mass.11.3.1.2 Re-measure the
40、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 60.001 g.11.3.2 Procedure B Elevated Temperature HumidityThestandard conditioning environment shall be 70 6 3C 160 65F and 85 6 5 % relative humidity for 30 days. Othertem
41、peratures, 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 vertical position andthe ends sitting on an open base (such as a screen or
42、 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 present. For materials that tend to collectwater on the surfaces or trap
43、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 11.2.2.11.3.2.3 Weigh and record the mass of each specimen ingrams to a precision of
44、60.001 g.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 cloth untilno visible water is present. For materials that tend to collec
45、twater 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 thick-ness as in 11.2.2.11.3.3.3 Weigh and record the mass of each spec
46、imen ingrams to a precision of 60.001 g.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.11.4 Surface Water CorrectionA typical indication thatsurface water is
47、 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 t
48、he 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 of each of the controlsamples in grams to a precision of 60.001 g.11.4.4 Dip each control sample quickly in water, shakevigorously and wipe off all surface water wit
49、h 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 toevaporate, and immediately weigh and record the mass.11.4.5 Subtract the post-dip mass from the initial mass toobtain the surface water mass gain for each specimen.11.4.6 Repeat steps 11.4.2 11.4.5 two more times for eachof the five control samples.11.4.7 Calculate the average surface water mass g
