1、Designation: D 6484/D 6484M 04Standard 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 rev
2、ision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method determines the open-hole compressivestrength of multidirectional polymer matrix c
3、omposite 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 symmetric with respect to the testdirection. The range of acceptable test la
4、minates 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 stated ineach system are not exact equivalents; therefore, each systemmust be u
5、sed 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 theresponsibility of the user of this standard to establish appro-priate
6、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 by DisplacementD 883 Terminology Relating to PlasticsD 2584 Test Method f
7、or 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 Content of CompositeMaterialsD 3878 Terminology for Composite MaterialsD 5229/
8、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 Prepara-tionE4 Practices for Force Verification of Testing MachinesE6 Terminol
9、ogy 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 aCharacteristic of a Lot or ProcessE 177 Practice for Use of the Terms Precision an
10、d 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-ReinforcedPolymer-Matrix Composite Materials in DatabasesE 1434 Guide for Recording
11、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 D 3878 defines terms relatingto high-modulus fibers and their composites.
12、 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 jurisdiction of ASTM Committee D30 onComposite Materials and is the direct respo
13、nsibility 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 99e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cust
14、omer 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 19428-2959, United States.the event of a conflict between ter
15、ms, 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 following the term (or letter symbol) infundamental dimension form, using the
16、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 restrictedto analytical dimensions when used with square brackets, as the sy
17、mbolsmay 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 nominalvalue to define an acceptable range for the property.3.2.2 principal
18、 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 the coordinatesystem axes to the normal directions of planes of symmetry ino
19、rder 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 material coordinate systemdue to the total lack of symmetry, while, for isot
20、ropic 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 term for laminated compositesis “reference coordinate system.”3.2.4 referen
21、ce 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 aposition, and the ply principal axis of each ply in the laminateis referenced re
22、lative 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 specially orthotropic lami-nate is a balanced and symmetric laminate of th
23、e 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 variation statistic of a sample populationfor a given property (in percent)Bzedgew
24、ise percent bendingDhole diameterhcoupon thicknessnnumber of coupons per sample populationNnumber of plies in laminate under testFxohcuultimate open hole (notched) compressive strengthin the test directionPmaxmaximum force carried by test coupon before failurer95 % repeatability confidence limit, eq
25、ual 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 propertySrrepeatability (within laboratory precision) standard de-viation, calculated
26、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 a given propertyxmean or average (estimate of mean) of a sample popu-lati
27、on 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 optional.Ultimate strength is calculated based on the gross cross-sectiona
28、l 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 account forvarious stress concentrations (fastener holes, free edges, fla
29、ws,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/fixture assembly isclamped in hydraulic wedge grips. The force is transmitted
30、 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 portion of the force initiallytransferred into the support fixture is transmitt
31、ed 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 to produce notched com-pressive strength data for structural design allow
32、ables, 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 fabrication, accuracy of lay-up, laminatestacking sequence and overall thickness
33、, 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 reinforcement. Properties that may be derivedfrom this test method include open-hole
34、 (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 042response, results from this test method are relatively insensitiveto parameters that would be of concern in an unnotc
35、hedcompressive 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 strength results. Sometypes of damage, such as longitudinal splitting and
36、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 diameter; this ratio should be maintained at 6,unless the experiment is investig
37、ating 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. Results may also be affected by the ratio of ungrippedspecimen length to specim
38、en 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 supportfixture. Sources of variation in this lateral pressure includefixture
39、 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 byinhibiting out-of-plane deformation beyond the cutout, and byrelieving for
40、ce 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 results should only be reportedwhen appropriate failure modes are observed, in a
41、ccordancewith 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 thickness). Thus, data gathered using thistest method may not translate directly
42、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 end-loaded specimens. Hydraulic grip-loaded datatypically exhibit linear b
43、ehavior 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 thespecimen/fixture assembly underneath the load platens, butthen exhibit linear b
44、ehavior 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 machined edges or very smooth-tooled surfaces.The accuracy of the instrument(s
45、) 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 an accuracy of 676 m 60.003 in. isdesirable for width measurement. Additio
46、nally, 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 short-grip/long-grip assemblies, two support plates, andstainless steel shims
47、 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 plate and the short grip with stainless steel shim stock.If the gap is too la
48、rge, 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/long-grip assembly is line-drilled as shown in Figs. 3 and4 and must be use
49、d 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 means of friction intothe test specimen. A cutout exists on both faces of the fixtur
