1、Designation: C297/C297M 04 (Reapproved 2010)C297/C297M 15Standard 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
2、 of revision, 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 U.S. Department of Defense.1. Scope1.1 This t
3、est method determines the flatwise tensile strength of the core, the core-to-facing bond, or the facing of an assembledsandwich panel. Permissible core material forms include those with continuous bonding surfaces (such as balsa wood and foams)as well as those with discontinuous bonding surfaces (su
4、ch as honeycomb).1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text theinch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system mustbe used independently of the othe
5、r. Combining values from the two systems may result in nonconformance 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 t
6、his 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 ConstructionsD792 Te
7、st Methods for Density and Specific Gravity (Relative Density) of Plastics by DisplacementD883 Terminology Relating to PlasticsD2584 Test Method for Ignition Loss of Cured Reinforced ResinsD2734 Test Methods for Void Content of Reinforced PlasticsD3039/D3039M Test Method for Tensile Properties of Po
8、lymer Matrix Composite MaterialsD3171 Test Methods for Constituent Content of Composite MaterialsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix CompositeMaterialsE4 Practices for Force Verification o
9、f Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot orProcessE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE456 Terminology Rel
10、ating to Quality and StatisticsE1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in DatabasesE1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in DatabasesE1471 Guide for Identification of Fibers, Fillers, and Core Materials in
11、 Computerized Material Property 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. Terminology E6
12、1 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 Oct. 1, 2010April 1, 2015. Published December 2010April 2015. Originally approved in 1952. Last previous
13、edition approved in 20042010 asC297/C297M 04.C297/C297M 04(2010). DOI: 10.1520/C0297_C0297M-04R10.10.1520/C0297_C0297M-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refe
14、r 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 previous version. Becauseit may not be technically possible to adequately depict all cha
15、nges 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 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. U
16、nited States1defines terms relating to mechanical testing. Terminology E456 and Practice E177 define terms relating to statistics. In the eventof a conflict between terms, Terminology D3878 shall have precedence over the other terminologies.3.2 Symbols:A = cross-sectional area of a test specimenCV =
17、 coefficient of variation statistic of a sample population for a given property (in percent)Fzftu = ultimate flatwise tensile strengthPmax = maximum force carried by test specimen before failureSn-1 = standard deviation statistic of a sample population for a given propertyx1 = test result for an ind
18、ividual specimen from the sample population for a given propertyx = mean or average (estimate of mean) of a sample population for a given property3.2 Symbols:3.2.1 Across-sectional area of a test specimen3.2.2 CVcoefficient of variation statistic of a sample population for a given property (in perce
19、nt)3.2.3 eedge tolerance between specimen and loading blocks3.2.4 Fzftuultimate flatwise tensile strength3.2.5 Pmaxmaximum force carried by test specimen before failure3.2.6 Sn-1 standard deviation statistic of a sample population for a given property3.2.7 xitest result for an individual specimen fr
20、om the sample population for a given property3.2.8 xmean or average (estimate of mean) of a sample population for a given property4. Summary of Test Method4.1 This test method consists of subjecting a sandwich construction to a uniaxial tensile force normal to the plane of thesandwich. The force is
21、transmitted to the sandwich through thick loading blocks, which are bonded to the sandwich facings ordirectly to the core.4.2 The only acceptable failure modes for flatwise tensile strength are those which are internal to the sandwich construction.Failure of the loading block-to-sandwich bond is not
22、 an acceptable failure mode.5. Significance and Use5.1 In a sandwich panel, core-to-facing bond integrity is necessary to maintain facing stability and permit load transfer betweenthe facings and core. This test method can be used to provide information on the strength and quality of core-to-facing
23、bonds. Itcan also be used to produce flatwise tensile strength data for the core material. While it is primarily used as a quality control testfor bonded sandwich panels, it can also be used to produce flatwise tensile strength data for structural design properties, materialspecifications, and resea
24、rch and development applications.5.2 Factors that influence the flatwise tensile strength and shall therefore be reported include the following: facing material, corematerial, adhesive material, methods of material fabrication, facing stacking sequence and overall thickness, core geometry (cellsize)
25、, size, cell wall thickness), core density, adhesive thickness, specimen geometry, specimen preparation, specimen conditioning,environment of testing, specimen alignment, loading procedure, speed of testing, facing void content, adhesive void content, andfacing volume percent reinforcement. Properti
26、es that may be derived from this test method include flatwise tensile strength.6. Interferences6.1 Material and Specimen PreparationPoor material fabrication practices, lack of control of fiber alignment, and damageinduced by improper specimen machining are known causes of high data scatter in compo
27、sites in general. Specific material factorsthat affect sandwich composites include variability in core density and degree of cure of resin in both facing matrix material andcore bonding adhesive. Important aspects of sandwich panel specimen preparation that contribute to data scatter are incompleteo
28、r nonuniform core bonding to facings, misalignment of core and facing elements, the existence of joints, voids or other core andfacing discontinuities, out-of-plane curvature, facing thickness variation, and surface roughness.6.2 System AlignmentExcessive bending will cause premature failure. Every
29、effort should be made to eliminate excessbending from the test system. Bending may occur as a result of misaligned grips, poor specimen preparation, or poor alignmentof the bondingloading blocks and loading fixture. If there is any doubt as to the alignment inherent in a given test machine, thenthe
30、alignment should be checked as discussed in Test Method D3039/D3039M.6.3 GeometrySpecific geometric factors that affect sandwich flatwise tensile strength include core cell geometry, corethickness, specimen shape (square or circular), adhesive thickness, facing thickness, and facing per-ply thicknes
31、s.C297/C297M 1526.4 EnvironmentResults are affected by the environmental conditions under which the tests are conducted. Specimens testedin various environments can exhibit significant differences in both strength behavior and failure mode. Critical environments mustbe assessed independently for eac
32、h facing, adhesive and core material tested.6.5 ConditioningAs it is inappropriate to bond a moisture-conditioned specimen to the bondingloading blocks, it is necessaryto perform the bonding operation prior to such conditioning. The presence of the bondingloading blocks will affect the degree ofmois
33、ture intake into the specimen, in comparison to a non-bonded sample.7. Apparatus7.1 MicrometersMicrometers and CalipersThe micrometer(s) shall use a 4- to 5-mm 0.16- to 0.20-in. A micrometer witha 4 to 7 mm 0.16 to 0.28 in. nominal diameter ball-interface on irregular surfaces such as or a flat anvi
34、l interface shall be usedto measure the specimen thickness. A ball interface is recommended for thickness measurements when facings are bonded to thecore and at least one surface is irregular (e.g. the bag-side of a facing laminate, and thin facing laminate that is neither smooth norflat). A microme
35、ter or caliper with a flat anvil interface is recommended for thickness measurements when facings are bonded tothe core and both surfaces are smooth (e.g. tooled surfaces). A micrometer or caliper with a flat anvil interface on machined edgesor very smooth-tooled surfaces. The shall be used for meas
36、uring length and width, as well as the specimen thickness when nofacings are present. The use of alternative measurement devices is permitted if specified (or agreed to) by the test requestor andreported by the testing laboratory. The accuracy of the instrument(s)instruments shall be suitable for re
37、ading to within 1 % 1 %of the sample length, width and thickness. dimensions. For typical specimen geometries, an instrument with an accuracy of62560.025 mm 60.001 in. is desirable for thickness, length and width measurement.adequate for the length, width, andthickness measurements.7.2 Loading Fixtu
38、resThe loading fixtures shall be self-aligning and shall not apply eccentric loads. A satisfactory type ofapparatus is shown in Fig. 1. A dual-pin connection or universal joint shall be attached to each loading block to minimize anymoments imparted to the test specimen. The loading blocks shall be s
39、ufficiently stiff to keep the bonded core or facings essentiallyFIG. 1 Flatwise Tension Test SetupC297/C297M 153flat under load. Loading blocks 40 to 50 mm 50 mm 1.5 to 2.0 in. thick have been found to perform satisfactorily. PermissibleRecommended dimensions and tolerances for the loading blocks (a
40、long with alignment requirements) are provided in Fig. 2.7.3 Testing MachineThe testing machine shall be in accordance with Practices E4 and shall satisfy the followingrequirements:7.3.1 Testing Machine ConfigurationThe testing machine shall have both an essentially stationary head and a movable hea
41、d.7.3.2 Drive MechanismThe testing machine drive mechanism shall be capable of imparting to the movable head a controlledvelocity with respect to the stationary head. The velocity of the movable head shall be capable of being regulated in accordancewith 11.6.7.3.3 LoadForce IndicatorThe testing mach
42、ine load-sensingforce-sensing device shall be capable of indicating the total forcebeing carried by the test specimen. This device shall be essentially free from inertia lag at the specified rate of testing and shallindicate the force with an accuracy over the force range(s) of interest of within 61
43、 % of the indicated value.7.4 Conditioning ChamberWhen conditioning materials at non-laboratory environments, a temperature/vapor-level controlledenvironmental conditioning chamber is required that shall be capable of maintaining the required temperature to within 63C65F63 C 65 F and the required re
44、lative humidity level to within 63 %. Chamber conditions shall be monitored either onan automated continuous basis or on a manual basis at regular intervals.7.5 Environmental Test ChamberAn environmental test chamber is required for test environments other than ambient testinglaboratory conditions.
45、This chamber shall be capable of maintaining the gage section of the test specimen at the required testenvironment during the mechanical test.8. Sampling and Test Specimens8.1 SamplingTest at least five specimens per test condition unless valid results can be gained through the use of fewerspecimens
46、, as in the case of a designed experiment. For statistically significant data, consult the procedures outlined in PracticeE122. Report the method of sampling.8.2 GeometryTest specimens shall have a square or circular cross-section, cross section, and shall be equal in thickness to thesandwich panel
47、thickness. Recommended dimensions and tolerances for the core specimens are provided in Fig. 3. Minimumspecimen facing areas for various types of core materials are as follows:8.2.1 Continuous Bonding Surfaces (for example, balsa wood, foams)The minimum facing area of the specimen shall be 625mm2 1.
48、0 in.2., and the minimum width or diameter of the loading blocks shall be 25 mm 1.0 in. Recommended tolerances forthe core specimens are provided in Fig. 3.8.2.2 Discontinuous Cellular Bonding Surfaces (for example, honeycomb)The required facing area of the specimen isdependent upon the cell size, t
49、o ensure a minimum number of cells are tested. Minimum facing areas and specimen dimensionsare recommended in Table 1 for the more common cell sizes. These are intended to provide approximately 60 cells minimum inFIG. 2 Loading Block Dimensions and TolerancesC297/C297M 154the test specimen. The largest facing area listed in the table (5625 mm2 9.0 in.2) is a practical maximum for this test method.Cores with cell sizes larger than 9 mm 0.375 in. may require a smaller number of cells to be tested in the specimen.8.3 Specim
