1、Designation: C297/C297M 04 (Reapproved 2010)Standard Test Method forFlatwise Tensile Strength of Sandwich Constructions1This standard is issued under the fixed designation C297/C297M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision,
2、 the year 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 Department of Defense.1. Scope1.1 This test method determi
3、nes the flatwise tensile strengthof the core, the core-to-facing bond, or the facing of anassembled sandwich panel. Permissible core material formsinclude those with continuous bonding surfaces (such as balsawood and foams) as well as those with discontinuous bondingsurfaces (such as honeycomb).1.2
4、The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. Within the text theinch-pound units are shown in brackets. The values stated ineach system are not exact equivalents; therefore, each systemmust be used independently of the other. Combining valuesfrom
5、 the two systems may result in nonconformance with thestandard.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 determine the applic
6、a-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C274 Terminology of Structural Sandwich ConstructionsD792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics by DisplacementD883 Terminology Relating to PlasticsD2584 Test Method for
7、 Ignition Loss of Cured ReinforcedResinsD2734 Test Methods for Void Content of Reinforced Plas-ticsD3039/D3039M Test Method for Tensile Properties ofPolymer Matrix Composite MaterialsD3171 Test Methods for Constituent Content of CompositeMaterialsD3878 Terminology for Composite MaterialsD5229/D5229M
8、 Test Method for Moisture AbsorptionProperties and Equilibrium Conditioning of Polymer Ma-trix Composite MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE122 Practice for Calculating Sample Size to Estimate,With Specified Precis
9、ion, the Average for a Characteristicof a Lot or ProcessE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in DatabasesE1434 Guide for Recordi
10、ng Mechanical Test Data of Fiber-Reinforced Composite Materials in DatabasesE1471 Guide for Identification of Fibers, Fillers, and CoreMaterials in Computerized Material Property Databases3. Terminology3.1 DefinitionsTerminology D3878 defines terms relatingto high-modulus fibers and their composites
11、. TerminologyC274 defines terms relating to structural sandwich construc-tions. Terminology D883 defines terms relating to plastics.Terminology E6 defines terms relating to mechanical testing.Terminology E456 and Practice E177 define terms relating tostatistics. In the event of a conflict between te
12、rms, TerminologyD3878 shall have precedence over the other terminologies.3.2 Symbols:A = cross-sectional area of a test specimenCV = coefficient of variation statistic of a sample populationfor a given property (in percent)1This test method is under the jurisdiction of ASTM Committee D30 onComposite
13、 Materials and is the direct responsibility of Subcommittee D30.09 onSandwich Construction.Current edition approved Oct. 1, 2010. Published December 2010. Originallyapproved in 1952. Last previous edition approved in 2004 as C297/C297M 04.DOI: 10.1520/C0297_C0297M-04R10.2For referenced ASTM standard
14、s, 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 1
15、9428-2959, United States.Fzftu= ultimate flatwise tensile strengthPmax= maximum force carried by test specimen beforefailureSn-1= standard deviation statistic of a sample population fora given propertyx1= test result for an individual specimen from the samplepopulation for a given propertyx = mean o
16、r average (estimate of mean) of a sample popu-lation for a given property4. Summary of Test Method4.1 This test method consists of subjecting a sandwichconstruction to a uniaxial tensile force normal to the plane ofthe sandwich. The force is transmitted to the sandwich throughthick loading blocks, w
17、hich are bonded to the sandwich facingsor directly to the core.4.2 The only acceptable failure modes for flatwise tensilestrength are those which are internal to the sandwich construc-tion. Failure of the loading block-to-sandwich bond is not anacceptable failure mode.5. Significance and Use5.1 In a
18、 sandwich panel, core-to-facing bond integrity isnecessary to maintain facing stability and permit load transferbetween the facings and core. This test method can be used toprovide information on the strength and quality of core-to-facing bonds. It can also be used to produce flatwise tensilestrengt
19、h data for the core material. While it is primarily used asa quality control test for bonded sandwich panels, it can also beused to produce flatwise tensile strength data for structuraldesign properties, material specifications, and research anddevelopment applications.5.2 Factors that influence the
20、 flatwise tensile strength andshall therefore be reported include the following: facingmaterial, core material, adhesive material, methods of materialfabrication, facing stacking sequence and overall thickness,core geometry (cell size), core density, adhesive thickness,specimen geometry, specimen pr
21、eparation, specimen condi-tioning, environment of testing, specimen alignment, loadingprocedure, speed of testing, facing void content, adhesive voidcontent, and facing volume percent reinforcement. Propertiesthat may be derived from this test method include flatwisetensile strength.6. Interferences
22、6.1 Material and Specimen PreparationPoor materialfabrication practices, lack of control of fiber alignment, anddamage induced by improper specimen machining are knowncauses of high data scatter in composites in general. Specificmaterial factors that affect sandwich composites include vari-ability i
23、n core density and degree of cure of resin in both facingmatrix material and core bonding adhesive. Important aspectsof sandwich panel specimen preparation that contribute to datascatter are incomplete or nonuniform core bonding to facings,misalignment of core and facing elements, the existence ofjo
24、ints, voids or other core and facing discontinuities, out-of-plane curvature, facing thickness variation, and surface rough-ness.6.2 System AlignmentExcessive bending will cause pre-mature failure. Every effort should be made to eliminate excessbending from the test system. Bending may occur as a re
25、sult ofmisaligned grips, poor specimen preparation, or poor align-ment of the bonding blocks and loading fixture. If there is anydoubt as to the alignment inherent in a given test machine, thenthe alignment should be checked as discussed in Test MethodD3039/D3039M.6.3 GeometrySpecific geometric fact
26、ors that affect sand-wich flatwise tensile strength include core cell geometry, corethickness, specimen shape (square or circular), adhesive thick-ness, facing thickness, and facing per-ply thickness.6.4 EnvironmentResults are affected by the environmen-tal conditions under which the tests are condu
27、cted. Specimenstested in various environments can exhibit significant differ-ences in both strength behavior and failure mode. Criticalenvironments must be assessed independently for each facing,adhesive and core material tested.6.5 ConditioningAs it is inappropriate to bond amoisture-conditioned sp
28、ecimen to the bonding blocks, it isnecessary to perform the bonding operation prior to suchconditioning. The presence of the bonding blocks will affectthe degree of moisture intake into the specimen, in comparisonto a non-bonded sample.7. Apparatus7.1 MicrometersThe micrometer(s) shall use a 4- to 5
29、-mm0.16- to 0.20-in. nominal diameter ball-interface on irregularsurfaces such as the bag-side of a facing laminate, and a flatanvil interface on machined edges or very smooth-tooledsurfaces. The accuracy of the instrument(s) shall be suitable forreading to within 1 % of the sample length, width and
30、thickness. For typical specimen geometries, an instrument withan accuracy of 625 mm 60.001 in. is desirable for thickness,length and width measurement.7.2 Loading FixturesThe loading fixtures shall be self-aligning and shall not apply eccentric loads.Asatisfactory typeof apparatus is shown in Fig. 1
31、. The loading blocks shall besufficiently stiff to keep the bonded core or facings essentiallyflat under load. Loading blocks 40 to 50 mm 1.5 to 2.0 in.thick have been found to perform satisfactorily. Permissibletolerances for the loading blocks (along with alignment re-quirements) are provided in F
32、ig. 2.7.3 Testing MachineThe testing machine shall be inaccordance with Practices E4 and shall satisfy the followingrequirements:7.3.1 Testing Machine ConfigurationThe testing machineshall have both an essentially stationary head and a movablehead.7.3.2 Drive MechanismThe testing machine drive mecha
33、-nism shall be capable of imparting to the movable head acontrolled velocity with respect to the stationary head. Thevelocity of the movable head shall be capable of beingregulated in accordance with 11.6.7.3.3 Load IndicatorThe testing machine load-sensingdevice shall be capable of indicating the t
34、otal force beingcarried by the test specimen. This device shall be essentiallyfree from inertia lag at the specified rate of testing and shallC297/C297M 04 (2010)2indicate the force with an accuracy over the force range(s) ofinterest of within 61 % of the indicated value.7.4 Conditioning ChamberWhen
35、 conditioning materialsat non-laboratory environments, a temperature/vapor-levelcontrolled environmental conditioning chamber is required thatshall be capable of maintaining the required temperature towithin 63C 65F and the required relative humidity levelto within 63 %. Chamber conditions shall be
36、monitored eitheron an automated continuous basis or on a manual basis atregular intervals.7.5 Environmental Test ChamberAn environmental testchamber is required for test environments other than ambienttesting laboratory conditions. This chamber shall be capable ofmaintaining the gage section of the
37、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 unless valid results can be gained through the use of fewerspecimens, as in the case of a designed experiment. Forstatistically signific
38、ant data, consult the procedures outlined inPractice E122. Report the method of sampling.8.2 GeometryTest specimens shall have a square or cir-cular cross-section, and shall be equal in thickness to thesandwich panel thickness. Minimum specimen facing areas forvarious types of core materials are as
39、follows:8.2.1 Continuous Bonding Surfaces (for example, balsawood, foams)The minimum facing area of the specimenshall be 625 mm21.0 in.2.8.2.2 Discontinuous Cellular Bonding Surfaces (for ex-ample, honeycomb)The required facing area of the specimenis dependent upon the cell size, to ensure a minimum
40、 numberof cells are tested. Minimum facing areas are recommended inTable 1 for the more common cell sizes. These are intended toprovide approximately 60 cells minimum in the test specimen.The largest facing area listed in the table (5625 mm29.0 in.2)is a practical maximum for this test method. Cores
41、 with cellsizes larger than 9 mm 0.375 in. may require a smallernumber of cells to be tested in the specimen.8.3 Specimen Preparation and MachiningSpecimenpreparation is extremely important for this test method. Takeprecautions when cutting specimens from large panels to avoidnotches, undercuts, rou
42、gh or uneven surfaces, or delaminationsdue to inappropriate machining methods. Obtain final dimen-sions by water-lubricated precision sawing, milling, or grind-ing. The use of diamond tooling has been found to beextremely effective for many material systems. Edges shouldbe flat and parallel within t
43、he specified tolerances. Record andreport the specimen cutting preparation method.8.4 LabelingLabel the 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.8.5 Loading Fixture BondingThe loadi
44、ng blocks shall bebonded to the core or facings of the test specimen using asuitable adhesive. To minimize thermal exposure effects uponthe existing core-to-facing bonds, it is recommended that theassembly bonding temperature be at room temperature, or atleast 28C 50F lower than that at which the sa
45、ndwich wasoriginally bonded. Similarly, the assembly bonding pressureshall not be greater than the original facing-to-core bondingpressure. Permissible tolerances for the bonded assembly(along with alignment requirements) are provided in Fig. 2.9. Calibration9.1 The accuracy of all measuring equipme
46、nt shall havecertified calibrations that are current at the time of use of theequipment.10. Conditioning10.1 Standard Conditioning ProcedureUnless a differentenvironment is specified as part of the experiment, conditionthe test specimens in accordance with Procedure C of TestMethod D5229/D5229M, and
47、 store and test at standard labo-ratory atmosphere (23 6 3C 73 6 5F and 50 6 5 % relativehumidity).11. Procedure11.1 Parameters to Be Specified Before Test:11.1.1 The specimen sampling method, specimen geometry,and conditioning travelers (if required).11.1.2 The properties and data reporting format
48、desired.NOTE 1Determine specific material property, accuracy, and datareporting requirements prior to test for proper selection of instrumentationand data recording equipment. Estimate the specimen strength to aid intransducer selection, calibration of equipment, and determination ofequipment settin
49、gs.11.1.3 The environmental conditioning test parameters.FIG. 1 Flatwise Tension Test SetupC297/C297M 04 (2010)311.1.4 If performed, sampling method, specimen geometry,and test parameters used to determine facing density andreinforcement volume.11.2 General Instructions:11.2.1 Report any deviations from this test method, whetherintentional or inadvertent.11.2.2 If specific gravity, density, facing reinforcement vol-ume, or facing void volume are to be reported, then obtainthese samples from the same panels being tested. Specificgravi
