1、Designation: C480/C480M 16Standard Test Method forFlexure Creep of Sandwich Constructions1This standard is issued under the fixed designation C480/C480M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of last revision. A
2、number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the creepcharacteristics and creep rate of flat sandwich constructionsloaded in flexure, a
3、t any desired temperature. Permissible corematerial forms include those with continuous bonding surfaces(such as balsa wood and foams) 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
4、standard. Within the text theinch-pound units are shown in brackets. The values stated ineither SI units or inch-pound units are to be regarded separatelyas standard. The values stated in each system may not be exactequivalents; therefore, each system shall be used independentlyof the other. Combini
5、ng values from the two systems mayresult in non-conformance with the standard.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-priate safety and health practices and deter
6、mine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C393/C393M Test Method for Core Shear Properties ofSandwich Constructions by Beam FlexureD883 Terminology Relating to PlasticsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method fo
7、r MoistureAbsorption Prop-erties and Equilibrium Conditioning of Polymer MatrixComposite MaterialsD7249/D7249M Test Method for Facing Properties of Sand-wich Constructions by Long Beam FlexureE6 Terminology Relating to Methods of Mechanical TestingE122 Practice for Calculating Sample Size to Estimat
8、e, 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 defines terms relatingto high-modulus fibers and t
9、heir composites, a well as termsrelating to sandwich constructions. Terminology D883 definesterms relating to plastics. Terminology E6 defines termsrelating to mechanical testing. Terminology E456 and PracticeE177 define terms relating to statistics. In the event of aconflict between terms, Terminol
10、ogy D3878 shall have prece-dence over the other terminology documents.3.2 Symbols:3.2.1 Adistance between pivot point and point of appliedforce on the specimen3.2.2 bspecimen width3.2.3 Bdistance from pivot point to center of gravity of theloading arm3.2.4 ccore thickness3.2.5 CRIcreep rate at time,
11、 ii3.2.6 dsandwich total thickness3.2.7 dinitial static deflection under the same load and atthe same temperature3.2.8 Dtotal deflection at time, t3.2.9 Ffapplied facing stress3.2.10 Fsapplied core shear stress3.2.11 Mdistance between point and weight point3.2.12 nnumber of specimens3.2.13 pmass of
12、loading plate and rod3.2.14 Papplied force3.2.15 Slength of support span3.2.16 wmass of lever arm3.2.17 Wmass of weight (including tray mass)1This specification is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.09 onSandwich Co
13、nstruction.Current edition approved April 1, 2016. Published April 2016. Originallyapproved in 1961. Last previous edition approved in 2015 as C480/C480M 08(2015). DOI: 10.1520/C0480_C0480M-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at se
14、rviceastm.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 States14. Summary of Test Method4.1 This test method consists
15、 of subjecting a beam ofsandwich construction to a sustained force normal to the planeof the sandwich, using either a 3-point or a 4-point loadingfixture. Deflection versus time measurements are recorded.4.2 For long beam specimens conforming to Test MethodD7249/D7249M, the only acceptable failure m
16、odes for sand-wich facesheet strength are those which are internal to one ofthe facesheets. Failure of the sandwich core or the core-to-facesheet bond preceding failure of one of the facesheets is notan acceptable failure mode for this specimen configuration.4.3 For short-beam specimens conforming t
17、o Test MethodC393/C393M, the only acceptable failure modes are core shearor core-to-facing bond. Failure of the sandwich facing preced-ing failure of the core or core-to-facing bond is not anacceptable failure mode for this specimen configuration.4.4 Careful post-test inspection of the specimen is r
18、equiredas facing failure occurring in proximity to the loading pointscan be caused by local through-thickness compression or shearfailure of the core that precedes failure of the facing.5. Significance and Use5.1 The determination of the creep rate provides informa-tion on the behavior of sandwich c
19、onstructions under constantapplied force. Creep is defined as deflection under constantforce over a period of time beyond the initial deformation as aresult of the application of the force. Deflection data obtainedfrom this test method can be plotted against time, and a creeprate determined. By usin
20、g standard specimen constructions andconstant loading, the test method may also be used to evaluatecreep behavior of sandwich panel core-to-facing adhesives.5.2 This test method provides a standard method of obtain-ing flexure creep of sandwich constructions for quality control,acceptance specificat
21、ion testing, and research and develop-ment.5.3 Factors that influence the sandwich construction creepresponse and shall therefore be reported include the following:facing material, core material, adhesive material, methods ofmaterial fabrication, facing stacking sequence and overallthickness, core g
22、eometry (cell size), core density, corethickness, adhesive thickness, specimen geometry, specimenpreparation, specimen conditioning, environment of testing,specimen alignment, loading procedure, speed of testing,facing void content, adhesive void content, and facing volumepercent reinforcement. Furt
23、her, facing and core-to-facingstrength and creep response may be different betweenprecured/bonded and co-cured facesheets of the same material.6. Interferences6.1 The interferences listed in Test Methods C393/C393Mand D7249/D7249M are also applicable to this test method.7. Apparatus7.1 Micrometers a
24、nd CalipersA micrometer having a flatanvil interface, or a caliper of suitable size, shall be used. Theinstruments(s) shall have an accuracy of 625 m 60.001 in.for thickness measurement, and an accuracy of 6250 m60.010 in. for length and width measurements.NOTE 1The accuracies given above are based
25、on achieving measure-ments that are within1%ofthesample length, width and thickness.7.2 Loading FixturesThe fixture for loading the specimenshall be a 3-point loading configuration that conforms to eitherTest Method D7249/D7249M (for a long beam test) or to TestMethod C393/C393M (for a short beam te
26、st) except that aconstant force shall be applied by means of weights and a leversystem. Fig. 1 shows a lever and weight-loading apparatus thathas been found satisfactory.7.3 Deflectometer (LVDT)The deflection of the specimenshall be measured in the center of the support span by aproperly calibrated
27、device having an accuracy of 60.025 mm60.001 in. or better.7.4 Conditioning ChamberWhen conditioning materialsat non-laboratory environments, a temperature/vapor-levelcontrolled environmental conditioning chamber is required thatshall be capable of maintaining the required temperature towithin 63C 6
28、5F and the required relative humidity levelto within 63 %. Chamber conditions shall be monitored eitheron an automated continuous basis or on a manual basis atregular intervals (a minimum of once daily checks are recom-mended).7.5 Environmental Test ChamberAn environmental testchamber is required fo
29、r test environments other than ambienttesting laboratory conditions. This chamber shall be capable ofmaintaining the gage section of the test specimen at therequired test environment during the mechanical test.8. Sampling and Test Specimens8.1 SamplingTest at least five specimens per test condi-tion
30、 unless valid results can be gained through the use of fewerspecimens, as in the case of a designed experiment. Forstatistically significant data, consult the procedures outlined inPractice E122. Report the method of sampling.8.2 Geometry, Facing, Core:8.2.1 Core or Core-to-Facing Failure Mode Desir
31、edThetest specimen configuration shall be a sandwich construction ofa size and proportions conforming to the flexure test specimendescribed in Test Method C393/C393M. The standard speci-men configuration should be used whenever the specimendesign equations in Section 8.2.3 of C393/C393M indicate tha
32、tFIG. 1 Creep Test Apparatus and Loading SystemC480/C480M 162a core of core-to-facing bond failure mode is expected. In caseswhere the standard C393/C393M specimen configuration willnot produce a desired failure, a non-standard specimen shall bedesigned to produce a core or bond failure mode.8.2.2 F
33、acesheet Failure Mode DesiredThe test specimenconfiguration shall be a sandwich construction of a size andproportions conforming to the flexure test specimen describedin Test Method D7249/D7249M. A non-standard 3-point load-ing specimen configuration shall be designed per Section 8.2.3of D7249/D7249
34、M to achieve a facing failure mode. Thestandard 4-point loading D7249/D7249M specimen configura-tion may be used if a suitable creep loading apparatus is used.8.3 Compression Side FacingUnless otherwise specifiedby the test requestor, the bag-side facing of a co-curedcomposite sandwich panel shall b
35、e placed as the upper,compression-loaded facing during test, as facing compressionstrength is more sensitive to imperfections typical of bag-sidesurfaces (for example, intra-cell dimpling) than is facingtension strength. Creep response is expected to follow the sametrends as static strength.8.4 Spec
36、imen Preparation and MachiningSpecimenpreparation is extremely important for this test method. Takeprecautions when cutting specimens from large panels to avoidnotches, undercuts, rough or uneven surfaces, or delaminationsdue to inappropriate machining methods. Obtain final dimen-sions by water-lubr
37、icated precision sawing, milling, or grind-ing. The use of diamond coated machining tools has beenfound to be extremely effective for many material systems.Edges should be flat and parallel within the specified toler-ances. Record and report the specimen cutting preparationmethod.8.5 LabelingLabel t
38、he test specimens so that they will bedistinct from each other and traceable back to the panel 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 theequi
39、pment10. Conditioning10.1 The recommended pre-test specimen condition is ef-fective moisture equilibrium at a specific relative humidity perD5229/D5229M; however, if the test requestor does notexplicitly specify a pre-test conditioning environment, condi-tioning is not required and the test specimen
40、s may be tested asprepared.10.2 The pre-test specimen conditioning process, to includespecified environmental exposure levels and resulting moisturecontent, shall be reported with the test data.NOTE 2The term moisture, as used in Test Method D5229/D5229M,includes not only the vapor of a liquid and i
41、ts condensate, but the liquiditself in large quantities, as for immersion.10.3 If no explicit conditioning process is performed, thespecimen conditioning process shall be reported as “uncondi-tioned” and the moisture content as “unknown”.11. Procedure11.1 Parameters to Be Specified Before Test:11.1.
42、1 The specimen sampling method, specimen geometry,and conditioning travelers (if required).11.1.2 The loading fixture support span (and loading span ifa 4-point loading configuration is used).11.1.3 The force, P, to be applied to the specimen and themaximum time for the test.11.1.4 The properties an
43、d data reporting format desired.11.1.5 The environmental conditioning test parameters.11.1.6 The nominal thicknesses of the facing materials.NOTE 3Determine specific material property, accuracy, and datareporting requirements prior to test for proper selection of instrumentationand data recording eq
44、uipment. Estimate the maximum specimen deflec-tion to aid in transducer selection, calibration of equipment, and determi-nation of equipment settings.11.2 General Instructions:11.2.1 Report any deviations from this test method, whetherintentional or inadvertent.11.2.2 Condition the specimens as requ
45、ired. Store the speci-mens in the conditioned environment until test time, if the testenvironment is different than the conditioning environment.11.2.3 Before testing, measure and record the specimenlength, width and thickness at three places in the test section.Measure the specimen length and width
46、 with an accuracy of6250 m 60.010 in. Measure the specimen thickness withan accuracy of 625 m 60.001 in. Record the dimensions tothree significant figures in units of millimeters inches.11.3 Measure and record the length of the support andloading spans.11.4 The weight required to apply the specified
47、 force to thespecimen by the 3-point loading lever system shown in Fig. 1may be calculated as follows:W 5P 2 p! A 2 wBM(1)where:W = mass of weight (including tray mass), N lb,P = force applied to specimen, N lb,p = mass of loading plate and rod, N lb,w = mass of lever arm, N lb,A = distance between
48、pivot point and point of applied forceon the specimen, mm in.B = distance from pivot point to center of gravity of theloading arm, mm in., andM = distance between pivot point and weight point, mm,11.5 Test EnvironmentIf possible, test the specimen underthe same fluid exposure level used for conditio
49、ning. However,cases such as elevated temperature testing of a moist specimenplace unrealistic requirements on the capabilities of commontesting machine environmental chambers. In such cases, themechanical test environment may need to be modified, forexample, by testing at elevated temperature with no fluidexposure control, but with a specified limit on time to failurefrom withdrawal from the conditioning chamber. Record anymodifications to the test environment.C480/C480M 16311.6 Specimen Insertion and AlignmentP
