1、Designation: D7766/D7766M 16Standard 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 resistanceassessments, due to reduced inf
7、luence of flexural stiffness andsupport fixture characteristics upon damage formation.However, the selection of a test procedure and associatedsupport conditions should be done in consideration of theintended structural application, and as such Procedures B andC may be more appropriate for comparati
8、ve purposes for someapplications.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 may r
9、esult 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 safety an
10、d health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics by DisplacementD883 Terminology Relating to PlasticsD3171 Test Methods for Constitu
11、ent Content of CompositeMaterialsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for MoistureAbsorption Prop-erties and Equilibrium Conditioning of Polymer MatrixComposite MaterialsD6264/D6264M Test Method for Measuring the DamageResistance of a Fiber-Reinforced Polymer-Matrix Com-
12、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 TestingE177 Practice for Use of the Terms Precision and Bia
13、s inASTM Test MethodsE456 Terminology Relating to Quality and Statistics1This practice is under the jurisdiction of ASTM Committee D30 on CompositeMaterials and is the direct responsibility of Subcommittee D30.09 on SandwichConstruction.Current edition approved May 15, 2016. Published June 2016. Ori
14、ginallyapproved in 2011. Last previous edition approved in 2011 as D7766/D7766M11.DOI: 10.1520/D7766_D7766M-16.2For 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 s
15、tandards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E2533 Guide for Nondestructive Testing of Polymer MatrixComposites Used in Aerospace Applications2.2 Other Documents:CMH-17-3G Composite
16、 Materials Handbook, Volume3Polymer Matrix Composites: Materials Usage, Designand Analysis3CMH-17-6 Composite Materials Handbook, Volume6Structural Sandwich Composites3MIL-HDBK-728/1 Nondestructive Testing4MIL-HDBK-731A Nondestructive Testing Methods ofComposite MaterialsThermography4MIL-HDBK-732A N
17、ondestructive Testing Methods ofComposite MaterialsAcoustic Emission4MIL-HDBK-733A Nondestructive Testing Methods ofComposite MaterialsRadiography4MIL-HDBK-787A Nondestructive Testing Methods ofComposite MaterialsUltrasonics43. Terminology3.1 DefinitionsTerminology D3878 defines terms relatingto hig
18、h-modulus fibers and their composites, as 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
19、between terms, Terminology D3878 shall have prece-dence 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 stated immediately following the term (or lettersymbol) in fundamental dimension form
20、, using the followingASTM standard symbology for fundamental dimensions,shown within square brackets: M for mass, L for length, Tfor time, for thermodynamic temperature, and nd fornon-dimensional quantities. Use of these symbols is restrictedto analytical dimensions when used with square brackets, a
21、sthe 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, or by an impactor after the impactevent during a drop-weight impact test. The dent
22、 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 nominal value, na value, existing in name only,assigned to a measurable property for
23、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 force ex-erted by the indenter on the specimen during a quasi-staticindentation test, or by the impactor on the specimen durin
24、g 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-weight impact test.3.3 Symbols:3.3.1 Epotential energy of impactor prior to drop
25、3.3.2 tthickness 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 specimen. Damage isimparted through an out-of-plane, concentrated force appliedby sl
26、owly 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 BIn accordance with Test Method D6264/D6264M, but with a sandwich specimen, perform
27、 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 the specimen. The damage resistanceis quantified in terms of the resulting size, loc
28、ation 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 through an out-of-plane, concentrated impact using adrop weight with a hemispherical st
29、riker 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 Methods D6264/D6264M (for quasi-static indenta-tion testing) and D7136/D7136M (for drop-
30、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 sandwich constructions. Knowl-edge of the damage resistance properties of a sandwic
31、h 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 facinggeometry, facing stacking sequence, facing-to-core interface,core geometry (cell size, cell wall thickness,
32、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 force, or impact energy.5.2.2 To compare quantitatively the relative values of thedamag
33、e resistance parameters for sandwich constructions withdifferent facing, core or adhesive materials. The damage3Available from SAE International (SAE), 400 Commonwealth Dr., Warrendale,PA 15096, http:/www.sae.org.4Available from U.S. Army Materials Technology Laboratory, Watertown, MA02471.D7766/D77
34、66M 162response parameters can include dent depth, damage dimen-sions and location(s), indentation or impact force 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
35、 can also be used toidentify a specific sequence of damage events (only the finaldamage state is identifiable after 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
36、similar materials,geometry, stacking sequence, and so forth. However, it must beunderstood that the damage resistance 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 r
37、elationships betweenforce/energy and the resultant damage state can result due todifferences in 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, whe
38、reas rigidly-backed specimens would more likely reflect the behavior of apanel local to substructure 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 dimensio
39、ns, in comparison tothose of a panel significantly larger than the test specimen,which tends to 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 com
40、parison of the damage resistance character-istics of sandwich panels of varying material, geometry,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
41、 on damage initiation and growth behaviorthan in edge-supported tests. However, it should be noted thatdamage resistance behavior observed using rigidly-backedspecimens may not strictly translate to edge-supported appli-cations. For example, sandwich constructions using cores withhigh compression st
42、iffness or strength, or both (e.g., balsawood) may exhibit superior performance in rigidly-backedtests, 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 t
43、est results. Consequently, it is imperative toconsider the intended assessment and structural 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
44、a rigidly-backed specimen in drop-weight impact testing may be appro-priate. Specific procedures 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 c
45、onsiderationof the implications of using rigidly-backed support conditions,such as their effect 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. Histor
46、ically, these tip geometrieshave generated a larger amount of internal damage for a givenamount 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 resistanc
47、e characteristics being examined.For example, the use of sharp tip geometries may be appropri-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
48、strength of specimenscontaining a specific damage state, such as a defined dentdepth, damage geometry, 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 t
49、hese practices. A relationshipbetween force or energy and the desired damage parameter canthen 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 adhesivematerial, ad
