ASTM D6484 D6484M-2004e1 809 Standard Test Method for Open-Hole Compressive Strength of Polymer Matrix Composite Laminates.pdf

1、Designation: D 6484/D 6484M 041Standard Test Method forOpen-Hole Compressive Strength of Polymer MatrixComposite Laminates1This standard is issued under the fixed designation D 6484/D 6484M; the number immediately following the designation indicates theyear of original adoption or, in the case of re

2、vision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEAdded research report footnote to Section 15 editorially in May 2009.1. Scope1.1 This test method determi

3、nes the open-hole compressivestrength of multidirectional polymer matrix composite lami-nates reinforced by high-modulus fibers. The composite mate-rial forms are limited to continuous-fiber or discontinuous-fiber(tape or fabric, or both) reinforced composites in which thelaminate is balanced and sy

4、mmetric with respect to the testdirection. The range of acceptable test laminates and thick-nesses are described in 8.2.1.1.2 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 state

5、d ineach system are not exact equivalents; therefore, each systemmust be used independently of the other. Combining valuesfrom 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

6、 theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics

7、 by DisplacementD 883 Terminology Relating to PlasticsD 2584 Test Method for Ignition Loss of Cured ReinforcedResinsD 2734 Test Method for Void Content of Reinforced Plas-ticsD 3039/D 3039M Test Method for Tensile Properties ofPolymer Matrix Composite MaterialsD 3171 Test Method for Constituent Cont

8、ent of CompositeMaterialsD 3878 Terminology for Composite MaterialsD 5229/D 5229M Test Method for Moisture AbsorptionProperties and Equilibrium Conditioning of Polymer Ma-trix Composite MaterialsD 5687/D 5687M Guide for Preparation of Flat CompositePanels with Processing Guidelines for Specimen Prep

9、ara-tionE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical Test-ingE83 Practice for Verification and Classification of Exten-sometersE 122 Practice for Calculating Sample Size to Estimate,With a Specified Tolerable Error, the Average for aCharacte

10、ristic of a Lot or ProcessE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 456 Terminology Relating to Quality and StatisticsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE 1309 Guide for Identification of Fiber-Reinforced

11、Polymer-Matrix Composite Materials in DatabasesE 1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in DatabasesE 1471 Guide for Identification of Fibers, Fillers, and CoreMaterials in Computerized Material Property Databases3. Terminology3.1 DefinitionsTerminology

12、 D 3878 defines terms relatingto high-modulus fibers and their composites. TerminologyD 883 defines terms relating to plastics. Terminology E6defines terms relating to mechanical testing. TerminologyE 456 and Practice E 177 define terms relating to statistics. In1This test method is under the jurisd

13、iction of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.05 onStructural Test Methods.Current edition approved March 1, 2004. Published April 2004. Originallyapproved in 1999. Last previous edition approved in 1999 as D 6484/D 6484M 991 .2For referenced

14、 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 page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Cons

15、hohocken, PA 19428-2959, United States.the event of a conflict between terms, Terminology D 3878shall have precedence over the other terminologies.3.2 Definitions of Terms Specific to This Standard:NOTE 1If the term represents a physical quantity, its analyticaldimensions are stated immediately foll

16、owing the term (or letter symbol) infundamental dimension form, using the following ASTM standard sym-bology for fundamental dimensions, shown within square brackets: Mfor mass, L for length, T for time, u for thermodynamic temperature,and nd for nondimensional quantities. Use of these symbols is re

17、strictedto analytical dimensions when used with square brackets, as the symbolsmay have other definitions when used without the brackets.3.2.1 nominal 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 n

18、ominalvalue to define an acceptable range for the property.3.2.2 principal material coordinate system, na coordinatesystem with axes that are normal to the planes of symmetryinherent to a material.3.2.3 DiscussionCommon usage, at least for Cartesianaxes (123, xyz, and so forth), generally assigns th

19、e coordinatesystem axes to the normal directions of planes of symmetry inorder that the highest property value in a normal direction (forelastic properties, the axis of greatest stiffness) would be 1 orx, and the lowest (if applicable) would be 3 or z. Anisotropicmaterials do not have a principal ma

20、terial coordinate systemdue to the total lack of symmetry, while, for isotropic materials,any coordinate system is a principal material coordinatesystem. In laminated composites, the principal material coor-dinate system has meaning only with respect to an individualorthotropic lamina. The related t

21、erm for laminated compositesis “reference coordinate system.”3.2.4 reference coordinate system, na coordinate systemfor laminated composites used to define ply orientations. Oneof the reference coordinate system axes (normally the Carte-sian x-axis) is designated the reference axis, assigned apositi

22、on, and the ply principal axis of each ply in the laminateis referenced relative to the reference axis to define the plyorientation for that ply.3.2.5 specially orthotropic, adja description of an ortho-tropic material as viewed in its principal material coordinatesystem. In laminated composites, a

23、specially orthotropic lami-nate is a balanced and symmetric laminate of the 0i/90jnsfamily as viewed from the reference coordinate system, suchthat the membrane-bending coupling terms of the laminateconstitutive relation are zero.3.3 Symbols:Across-sectional area of a couponCVcoefficient of variatio

24、n statistic of a sample populationfor a given property (in percent)Bzedgewise percent bendingDhole diameterhcoupon thicknessnnumber of coupons per sample populationNnumber of plies in laminate under testFxohcuultimate open hole (notched) compressive strengthin the test directionPmaxmaximum force car

25、ried by test coupon before failurer95 % repeatability confidence limit, equal to 2.8 timesthe repeatability standard deviationR95 % reproducibility confidence limit, equal to 2.8 timesthe reproducibility standard deviationSn1standard deviation statistic of a sample population fora given propertySrre

26、peatability (within laboratory precision) standard de-viation, calculated in accordance with Practice E 691SRreproducibility (between laboratory precision) standarddeviation, calculated in accordance with Practice E 691wcoupon widthx1test result for an individual coupon from the samplepopulation for

27、 a given propertyxmean or average (estimate of mean) of a sample popu-lation for a given propertysnormal stress4. Summary of Test Method4.1 A uniaxial compression test of a balanced, symmetriclaminate is performed with a centrally located hole. Edge-mounted extensometer displacement transducers are

28、optional.Ultimate strength is calculated based on the gross cross-sectional area, disregarding the presence of the hole. While thehole causes a stress concentration and reduced net section, it iscommon aerospace practice to develop notched design allow-able strengths based on gross section stress to

29、 account forvarious stress concentrations (fastener holes, free edges, flaws,damage, and so forth) not explicitly modeled in the stressanalysis.4.2 The test specimen is face-supported in a multi-piecebolted support fixture. Two acceptable test procedures areprovided. In Procedure A, the specimen/fix

30、ture assembly isclamped in hydraulic wedge grips. The force is transmitted byshear into the support fixture and then is transmitted by shearinto the test specimen. In Procedure B, the specimen/fixtureassembly is placed between flat platens, such that the specimenand fixture are end-loaded. The porti

31、on of the force initiallytransferred into the support fixture is transmitted by shear intothe test specimen.4.3 The only acceptable failure mode for ultimate open-holecompressive strength is one which passes through the hole inthe test specimen.5. Significance and Use5.1 This test method is designed

32、 to produce notched com-pressive strength data for structural design allowables, materialspecifications, research and development, and quality assur-ance. Factors that influence the notched compressive strengthand shall therefore be reported include the following: material,methods of material fabric

33、ation, accuracy of lay-up, laminatestacking sequence and overall thickness, specimen geometry,specimen preparation (especially of the hole), specimen con-ditioning, environment of testing, specimen alignment andgripping, loading procedure, speed of testing, void content, andvolume percent reinforcem

34、ent. Properties that may be derivedfrom this test method include open-hole (notched) compressivestrength (OHC).6. Interferences6.1 Hole PreparationBecause of the dominating presenceof the notch, and the lack of need to measure the materialD 6484/D 6484M 0412response, results from this test method ar

35、e relatively insensitiveto parameters that would be of concern in an unnotchedcompressive property test. However, since the notch dominatesthe strength, consistent preparation of the hole, without damageto the laminate, is important to meaningful results. Damagecaused by hole preparation will affect

36、 strength results. Sometypes of damage, such as longitudinal splitting and delamina-tion, can blunt the stress concentration caused by the hole,increasing the force-carrying capacity of the coupon and thecalculated strength.6.2 GeometryResults are affected by the ratio of specimenwidth to hole diame

37、ter; this ratio should be maintained at 6,unless the experiment is investigating the influence of thisratio. Results may also be affected by the ratio of hole diameterto thickness; the preferred ratio is the range from 1.5 to 3.0unless the experiment is investigating the influence of thisratio. Resu

38、lts may also be affected by the ratio of ungrippedspecimen length to specimen width; this ratio should bemaintained at 2.7, unless the experiment is investigating theinfluence of this ratio.6.3 Support FixtureResults are affected by the amount oflateral pressure applied to the test specimen by the s

39、upportfixture. Sources of variation in this lateral pressure includefixture bolt torque, hydraulic gripping pressure, and fixtureshimming choices, and should be controlled and reported asrequired in the Procedure and Report sections. The supportfixture can inhibit the growth of delamination damage b

40、yinhibiting out-of-plane deformation beyond the cutout, and byrelieving force from the specimen via friction effects. This mayresult in non-conservative data.6.4 Material OrthotropyThe degree of laminate orthot-ropy strongly affects the failure mode and measured OHCstrength. Valid OHC strength resul

41、ts should only be reportedwhen appropriate failure modes are observed, in accordancewith 11.9.6.5 Thickness ScalingThick composite structures do notnecessarily fail at the same strengths as thin structures with thesame laminate orientation (that is, strength does not alwaysscale linearly with thickn

42、ess). Thus, data gathered using thistest method may not translate directly into equivalent thick-structure properties.6.6 Type of LoadingDifferences in force versus crossheaddisplacement and force versus extensometer strain responsemay be observed when comparing hydraulic grip-loaded speci-mens with

43、 end-loaded specimens. Hydraulic grip-loaded datatypically exhibit linear behavior at the onset of loading.At highforce levels, some nonlinear behavior may be observed due togrip slippage. End-loaded data typically display some initialnonlinear behavior at low force levels, due to seating of thespec

44、imen/fixture assembly underneath the load platens, butthen exhibit linear behavior to failure.7. Apparatus7.1 MicrometersThe micrometer(s) shall use a 4- to 5-mm0.16- to 0.20-in. nominal diameter ball-interface on irregularsurfaces such as the bag-side of a laminate, and a flat anvilinterface on mac

45、hined edges or very smooth-tooled surfaces.The accuracy of the instrument(s) shall be suitable for readingto within 1 % of the sample width and thickness. For typicalspecimen geometries, an instrument with an accuracy of 625m 60.001 in. is desirable for thickness measurement, whilean instrument with

46、 an accuracy of 676 m 60.003 in. isdesirable for width measurement. Additionally, a micrometeror gage capable of determining the hole diameter to 625 m60.001 in. is required.7.2 Support FixtureThe fixture is a face-supported com-pressive test fixture as shown in Fig. 1. The fixture consists oftwo sh

47、ort-grip/long-grip assemblies, two support plates, andstainless steel shims as required to maintain a nominally zero(0.00- to 0.12-mm 0.000- to 0.005-in. tolerance) gap betweensupport plates and long grips. If this gap does not meet theminimum requirement, shim the contact area between thesupport pl

48、ate and the short grip with stainless steel shim stock.If the gap is too large, shim between the support plate and thelong grip, holding the shim stock on the support plate withtape. Fig. 2 shows shim requirements. The fixture should bechecked for conformity to engineering drawings. Each short-grip/

49、long-grip assembly is line-drilled as shown in Figs. 3 and4 and must be used as a matched set. The threading of thesupport plate is optional. Standard test specimens are 36 by 300mm 1.5 by 12 in. In Procedure A, the fixture is hydraulicallygripped on each end and the compressive force is transmittedby means of friction through the fixture and into the testspecimen. In Procedure B, the fixture is placed between flatplatens and loaded in compression at each end; force intro-duced into the fixture is transmitted by mea