1、Designation: D7766_D7766M 11Standard Practice forDamage Resistance Testing of Sandwich Constructions1This standard is issued under the fixed designation D7766_D7766M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the year of last
2、 revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice provides instructions for modifying lami-nate quasi-static indentation and drop-weight impact test meth-ods
3、to determine damage resistance properties of sandwichconstructions. Permissible core material forms include thosewith continuous bonding surfaces (such as balsa wood andfoams) as well as those with discontinuous bonding surfaces(such as honeycomb, truss cores and fiber-reinforced cores).1.2 This pra
4、ctice supplements Test Methods D6264/D6264M (for quasi-static indentation testing) and D7136/D7136M (for drop-weight impact testing) with provisions fortesting sandwich specimens. Several important test specimenparameters (for example, facing thickness, core thickness andcore density) are not mandat
5、ed by this practice; however,repeatable results require that these parameters be specified andreported.1.3 Three test procedures are provided. Procedures A and Bcorrespond to D6264/D6264M test procedures for rigidly-backed and edge-supported test conditions, respectively. Pro-cedure C corresponds to
6、 D7136/D7136M test procedures. Allthree procedures are suitable for imparting damage to asandwich specimen in preparation for subsequent damagetolerance testing.1.4 In general, Procedure A is considered to be the mostsuitable procedure for comparative damage resistance assess-ments, due to reduced i
7、nfluence of flexural stiffness andsupport fixture characteristics upon damage formation. How-ever, the selection of a test procedure and associated supportconditions should be done in consideration of the intendedstructural application, and as such Procedures B and C may bemore appropriate for compa
8、rative purposes for some applica-tions.1.5 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system are not exact equivalents; therefore, each systemmust be used independently of the other. Combining valuesfrom the two systems
9、 may result in non-conformance with thestandard.1.5.1 Within the text the inch-pound units are shown inbrackets.1.6 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 saf
10、ety and health practices and determine the applica-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 Term
11、inology Relating to PlasticsD3171 Test Methods for Constituent Content of CompositeMaterialsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for Moisture AbsorptionProperties and Equilibrium Conditioning of Polymer Ma-trix Composite MaterialsD6264/D6264M Test Method for Measuring th
12、e DamageResistance of a Fiber-Reinforced Polymer-Matrix Com-posite to a Concentrated Quasi-Static Indentation ForceD7136/D7136M Test Method for Measuring the DamageResistance of a Fiber-Reinforced Polymer Matrix Com-posite to a Drop-Weight Impact EventE6 Terminology Relating to Methods of Mechanical
13、 TestingE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE2533 Guide for Nondestructive Testing of Polymer MatrixComposites Used in Aerospace Applications2.2 Military Standards:MIL-HDBK-17-3F Composite Materials Handbook, Vol
14、-ume 3Polymer Matrix Composites Materials Usage,Design and Analysis3MIL-HDBK-728/1 Nondestructive Testing4MIL-HDBK-731A Nondestructive Testing Methods of1This practice is under the jurisdiction of ASTM Committee D30 on CompositeMaterials and is the direct responsibility of Subcommittee D30.09 on San
15、dwichConstruction.Current edition approved Nov. 15, 2011. Published December 2011.2For 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 pag
16、e onthe ASTM website.3Available from U.S. Army Research Laboratory, Materials Directorate, Ab-erdeen Proving Ground, MD 21001.4Available from U.S. Army Materials Technology Laboratory, Watertown, MA02471.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2
17、959, United States.Composite MaterialsThermography4MIL-HDBK-732A Nondestructive Testing Methods ofComposite MaterialsAcoustic Emission4MIL-HDBK-733A Nondestructive Testing Methods ofComposite MaterialsRadiography4MIL-HDBK-787A Nondestructive Testing Methods ofComposite MaterialsUltrasonics43. Termin
18、ology3.1 DefinitionsTerminology D3878 defines terms relatingto high-modulus fibers and their composites. TerminologyC274 defines terms relating to sandwich constructions. Termi-nology D883 defines terms relating to plastics. Terminology E6defines terms relating to mechanical testing. Terminology E45
19、6and Practice E177 define terms relating to statistics. In theevent of a conflict between terms, Terminology D3878 shallhave precedence over the other terminologies.3.2 Definitions of Terms Specific to This Standard:3.2.1 If the term represents a physical quantity, its analyticaldimensions are state
20、d immediately following the term (or lettersymbol) in fundamental dimension form, using the followingASTM standard symbology for fundamental dimensions,shown within square brackets: M for mass, L for length, Tfor time, u for thermodynamic temperature, and nd fornon-dimensional quantities. Use of the
21、se symbols is restrictedto analytical dimensions when used with square brackets, asthe symbols may have other definitions when used without thebrackets.3.2.2 dent depth, d L, nresidual depth of the depressionformed by an indenter after removal of applied force during aquasi-static indentation test,
22、or by an impactor after the impactevent during a drop-weight impact test. The dent depth shall bedefined as the maximum distance in a direction normal to theface of the specimen from the lowest point in the dent to theplane of the indented or impacted surface that is undisturbed bythe dent.3.2.3 nom
23、inal value, na value, existing in name only,assigned to a measurable property for the purpose of conve-nient designation. Tolerances may be applied to a nominalvalue to define an acceptable range for the property.3.2.4 recorded contact force, F MLT2, nthe forceexerted by the indenter on the specimen
24、 during a quasi-staticindentation test, or by the impactor on the specimen during adrop-weight impact test, as recorded by a force indicator.3.2.5 tip, nthe portion or component of the indenter orimpactor which comes into contact with the test specimen firstduring a quasi-static indentation or drop-
25、weight impact test.3.3 Symbols:3.3.1 E potential energy of impactor prior to drop3.3.2 t thickness of impacted sandwich facing4. Summary of Practices4.1 Procedure AIn accordance with Test Method D6264/D6264M, but with a sandwich specimen, perform a quasi-staticindentation test of a rigidly-backed sp
26、ecimen. Damage isimparted through an out-of-plane, concentrated force appliedby slowly pressing a displacement-controlled hemisphericalindenter into the face of the specimen. The damage resistanceis quantified in terms of the resulting size, location and type ofdamage in the specimen.4.2 Procedure B
27、In accordance with Test Method D6264/D6264M, but with a sandwich specimen, perform a quasi-staticindentation test of an edge-supported specimen. Damage isimparted through an out-of-plane, concentrated force appliedby slowly pressing a displacement-controlled hemisphericalindenter into the face of th
28、e specimen. The damage resistanceis quantified in terms of the resulting size, location and type ofdamage in the specimen.4.3 Procedure CIn accordance with Test Method D7136/D7136M, but with a sandwich specimen, perform a drop-weight impact test of an edge-supported specimen. Damage isimparted throu
29、gh an out-of-plane, concentrated impact using adrop weight with a hemispherical striker tip. The damageresistance is quantified in terms of the resulting size, locationand type of damage in the specimen.5. Significance and Use5.1 This practice provides supplemental instructions thatallow Test Method
30、s D6264/D6264M (for quasi-static indenta-tion testing) and D7136/D7136M (for drop-weight impacttesting) to determine damage resistance properties of sandwichconstructions. Susceptibility to damage from concentratedout-of-plane forces is one of the major design concerns ofmany structures made using s
31、andwich constructions. Knowl-edge of the damage resistance properties of a sandwich panelis useful for product development and material selection.5.2 Sandwich damage resistance testing can serve the fol-lowing purposes:5.2.1 To establish quantitatively the effects of facing geom-etry, facing stackin
32、g sequence, facing-to-core interface, coregeometry (cell size, cell wall thickness, core thickness, etc.),core density, core strength, processing and environmentalvariables on the damage resistance of a particular sandwichpanel to a concentrated quasi-static indentation force, drop-weight impact for
33、ce, or impact energy.5.2.2 To compare quantitatively the relative values of thedamage resistance parameters for sandwich constructions withdifferent facing, core or adhesive materials. The damageresponse parameters can include dent depth, damage dimen-sions and location(s), indentation or impact for
34、ce magnitudes,impact energy magnitudes, as well as the force versus timecurve.5.2.3 To impart damage in a specimen for subsequentdamage tolerance tests.5.2.4 Quasi-static indentation tests can also be used toidentify a specific sequence of damage events (only the finaldamage state is identifiable af
35、ter a drop-weight impact test).5.3 The properties obtained using these practices can pro-vide guidance in regard to the anticipated damage resistancecapability of sandwich structures with similar materials, geom-etry, stacking sequence, and so forth. However, it must beunderstood that the damage res
36、istance of a sandwich structureis highly dependent upon several factors including geometry,thickness, stiffness, mass, support conditions, and so forth.5.3.1 Significant differences in the relationships betweenforce/energy and the resultant damage state can result due toD7766_D7766M 112differences i
37、n these parameters. For example, properties ob-tained using edge-supported specimens would more likelyreflect the damage resistance characteristics of a sandwichpanel away from substructure attachments, whereas rigidly-backed specimens would more likely reflect the behavior of apanel local to substr
38、ucture which resists out-of-plane deforma-tion. Similarly, edge-supported impact test specimen propertieswould be expected to be similar to those of a sandwich panelwith equivalent length and width dimensions, in comparison tothose of a panel significantly larger than the test specimen,which tends t
39、o divert a greater proportion of the impact energyinto elastic deformation.5.3.2 Procedure A (quasi-static indentation using a rigidly-backed specimen) is considered to be the most suitableprocedure for comparison of the damage resistance character-istics of sandwich panels of varying material, geom
40、etry,stacking sequence and so forth. This is because the rigidbacking plate resists out-of-plane deformation of the specimen,such that the sandwich flexural stiffness and support geometryhave less influence on damage initiation and growth behaviorthan in edge-supported tests. However, it should be n
41、oted thatdamage resistance behavior observed using rigidly-backedspecimens may not strictly translate to edge-supported appli-cations. For example, sandwich constructions using cores withhigh compression stiffness or strength, or both (e.g., balsawood) may exhibit superior performance in rigidly-bac
42、kedtests, but that performance may not strictly translate to edge-supported tests in which the core shear stiffness, core shearstrength and sandwich panel flexural stiffness have greaterinfluence upon the test results. Consequently, it is imperative toconsider the intended assessment and structural
43、applicationwhen selecting a test procedure for comparative purposes, andas such the use of Procedures B and C may be more appropriatefor some applications.5.3.3 For some structural applications, the use of a rigidly-backed specimen in drop-weight impact testing may be appro-priate. Specific procedur
44、es for such testing are not included inthis practice, but the general approach detailed for Procedure Cmay be useful as guidance material when conducting suchassessments. Such tests should be performed in considerationof the implications of using rigidly-backed support conditions,such as their effec
45、t upon contact forces and sandwich defor-mation under impact, as well as the potential for damage to thetest apparatus.5.4 The standard indenter and impactor geometries haveblunt, hemispherical tips. Historically, these tip geometrieshave generated a larger amount of internal damage for a givenamoun
46、t of external damage, when compared with that observedfor similar indentations or impacts using sharp tips.Alternativeindenter and impactor geometries may be appropriate depend-ing upon the damage resistance characteristics being examined.For example, the use of sharp tip geometries may be appropri-
47、ate for certain facing penetration resistance assessments.5.5 Some testing organizations may desire to use thesepractices in conjunction with a subsequent damage tolerancetest method to assess the residual strength of specimenscontaining a specific damage state, such as a defined dentdepth, damage g
48、eometry, damage location, and so forth. In thiscase, the testing organization should subject several specimens,or a large panel, to multiple indentations or impacts, or both, atvarious energy levels using these practices. A relationshipbetween force or energy and the desired damage parameter canthen
49、 be developed. Subsequent residual strength tests can thenbe performed using specimens damaged using an interpolatedenergy or force level that is expected to produce the desireddamage state.6. Interferences6.1 The response of a sandwich specimen to an out-of-planeforce or impact is dependent upon many factors, such as facingmaterial, facing thickness, facing ply thickness, facing stackingsequence, facing surface flatness, facing-to-core adhesive ma-terial, adhesive thickness, core material, core geometry (cellsize, cell wall thickness, core thickness, etc
