1、Designation: D5766/D5766M 11Standard Test Method forOpen-Hole Tensile Strength of Polymer Matrix CompositeLaminates1This standard is issued under the fixed designation D5766/D5766M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, t
2、he 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.1. Scope1.1 This test method determines the open-hole tensilestrength of multidirectional polymer matrix composite lami
3、-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 laminates and t
4、hick-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. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems
5、 may result in non-conformancewith the standard.1.2.1 Within the text the inch-pound units are shown inbrackets.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 saf
6、ety and 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 PlasticsD2584 Test Method for Ign
7、ition Loss of Cured ReinforcedResinsD2734 Test Methods for Void Content of Reinforced Plas-ticsD3039/D3039M Test Method for Tensile Properties ofPolymer Matrix Composite MaterialsD3171 Test Methods for Constituent Content of CompositeMaterialsD3878 Terminology for Composite MaterialsD5229/D5229M Tes
8、t Method for Moisture AbsorptionProperties and Equilibrium Conditioning of Polymer Ma-trix Composite MaterialsE6 Terminology Relating to Methods of Mechanical TestingE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE691 Pract
9、ice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in DatabasesE1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases3. Terminology3.1
10、DefinitionsTerminology D3878 defines terms relatingto high-modulus fibers and their composites. TerminologyD883 defines terms relating to plastics.Terminology E6 definesterms relating to mechanical testing. Terminology E456 andPractice E177 define terms relating to statistics. In the event ofa confl
11、ict between terms, Terminology D3878 shall haveprecedence over the other standards.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,
12、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 non-dimensional quantities. Use of these symbols is restrictedto analytical dimensions when used with square brackets
13、, as the symbolsmay have other definitions when used without the brackets.3.2.1 diameter-to-thickness ratio, D/h nd, nin an open-hole specimen, the ratio of the hole diameter to the specimenthickness.3.2.1.1 DiscussionThe diameter-to-thickness ratio may beeither a nominal value determined from nomin
14、al dimensions oran actual value determined from measured dimensions.1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.05 onStructural Test Methods.Current edition approved Jan. 1, 2011. Published February 2011
15、. Originallyapproved in 1995. Last previous edition approved in 2007 as D5766/D5766M 07.DOI: 10.1520/D5766_D5766M-11.2For 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
16、 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.3.2.2 nominal value, na value, existing in name only,assigned to a measurable property for the purpose of conve-nient designation
17、. Tolerances may be applied to a nominalvalue to define an acceptable range for the property.3.2.3 principal material coordinate system, na coordinatesystem with axes that are normal to the planes of symmetryinherent to a material.3.2.3.1 DiscussionCommon usage, at least for Cartesianaxes (123, xyz,
18、 and so forth), generally assigns the 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. Anisotropic
19、materials do not have a principal material 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 individ
20、ualorthotropic lamina. The related term 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
21、the reference axis, assigned aposition, 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 coordinat
22、esystem. In laminated composites, a 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.3.2.6 width-to-diameter ratio, w/D
23、 nd, nin an open-holespecimen, the ratio of the specimen width to the hole diameter.3.2.6.1 DiscussionThe width-to-diameter ratio may beeither a nominal value determined from nominal dimensions oran actual value determined from measured dimensions.3.3 Symbols:A = cross-sectional area of a specimenCV
24、 = coefficient of variation statistic of a sample populationfor a given property (in percent)D = hole diameterh = specimen thicknessn = number of specimens per sample populationN = number of plies in laminate under testFxOHTu= ultimate open-hole (notched) tensile strength in thetest directionPmax= m
25、aximum force carried by test specimen prior tofailuresn-1= standard deviation statistic of a sample population fora given propertySr= repeatability (within laboratory precision) standard de-viation, calculated in accordance with Practice E691SR= reproducibility (between laboratory precision) standar
26、ddeviation, calculated in accordance with Practice E691w = specimen widthxi= test result for an individual specimen from the samplepopulation for a given propertyx = mean or average (estimate of mean) of a samplepopulation for a given propertys = normal stress4. Summary of Test Method4.1 A uniaxial
27、tension test of a balanced, symmetric lami-nate is performed in accordance with Test Method D3039/D3039M, although with a centrally located hole. Edge-mounted extensometer displacement transducers are optional.Ultimate strength is calculated based on the gross cross-sectional area, disregarding the
28、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, flaws,damage, and so forth)
29、not explicitly modeled in the stressanalysis.4.2 The only acceptable failure mode for ultimate open-holetensile strength is one which passes through the hole in the testspecimen.5. Significance and Use5.1 This test method is designed to produce notched tensilestrength data for structural design allo
30、wables, material speci-fications, research and development, and quality assurance.Factors that influence the notched tensile strength and shouldtherefore be reported include the following: material, methodsof material fabrication, accuracy of lay-up, laminate stackingsequence and overall thickness,
31、specimen geometry (includinghole diameter, diameter-to-thickness ratio, and width-to-diameter ratio), specimen preparation (especially of the hole),specimen conditioning, environment of testing, specimenalignment and gripping, speed of testing, time at temperature,void content, and volume percent re
32、inforcement. Propertiesthat may be derived from this test method include the follow-ing:5.1.1 Open-hole (notched) tensile strength (OHT).6. Interferences6.1 Hole PreparationDue to the dominating presence ofthe notch, and the lack of need to measure the materialresponse, results from this test method
33、 are relatively insensitiveto parameters that would be of concern in an unnotched tensileproperty test. However, since the notch dominates the strength,consistent preparation of the hole, without damage to thelaminate, is important to meaningful results. Damage due tohole preparation will affect str
34、ength results. Some types ofdamage, such as delaminations, can blunt the stress concentra-tion due to the hole, increasing the force-carrying capacity ofthe specimen and the calculated strength. Other types ofdamage can reduce the calculated strength.6.2 Specimen GeometryResults are affected by the
35、ratioof specimen width to hole diameter (w/D); this ratio should bemaintained at 6, unless the experiment is investigating theinfluence of this ratio. Results may also be affected by the ratioof hole diameter to thickness (D/h); the preferred ratio is theD5766/D5766M 112range from 1.5 to 3.0 unless
36、the experiment is investigating theinfluence of this ratio. Results may also be affected byspecimen length3; the preferred specimen length is in the rangefrom 200 to 300 mm 8.0 to 12.0 in. Shorter specimens (150to 200 mm 6.0 to 8.0 in) may be utilized in accordance withthe limitations defined in 8.2
37、.2. The equivalence of test resultsfrom Configurations A and B is contingent upon severalfactors, including fiber strain-to-failure, resin strength andfracture toughness. Laminates with a propensity to developsub-critical resin splits and cracks could potentially be affectedby a change in specimen l
38、ength due to closer grip proximity tothe hole (and any longitudinal cracks that may develop).6.3 Material OrthotropyThe degree of laminate orthot-ropy strongly affects the failure mode and measured OHTstrength. Valid OHT strength results should only be reportedwhen appropriate failure modes are obse
39、rved, in accordancewith 11.5.6.4 Thickness ScalingThick composite structures do notnecessarily fail at the same strengths as thin structures with thesame laminate orientation (that is, strength does not alwaysremain constant independent of specimen thickness). Thus,data gathered using this test meth
40、od may not translate directlyinto equivalent thick-structure properties.6.5 OtherAdditional sources of potential data scatter intesting of composite materials are described in Test MethodD3039/D3039M.7. Apparatus7.1 Apparatus shall be in accordance with Test MethodD3039/D3039M. Additionally, a micro
41、meter or gage capableof determining the hole diameter to 60.025 mm 60.001 in.is required.8. Sampling and Test Specimens8.1 SamplingSampling shall be in accordance with TestMethod D3039/D3039M.8.2 GeometryThe specimen geometry shall be in accor-dance with Test Method D3039/D3039M, as modified by thef
42、ollowing, and illustrated by the schematic of Fig. 1. Anyvariation of the stacking sequence, specimen width or length,or hole diameter from that specified shall be clearly noted inthe report.8.2.1 Stacking SequenceThe standard laminate shall havemultidirectional fiber orientations (fibers shall be o
43、riented in aminimum of two directions), and balanced and symmetricstacking sequences. Nominal thickness shall be 2.5 mm 0.10in., with a permissible range of 2 to 4 mm 0.080 to 0.160 in.,inclusive. Fabric laminates containing satin-type weaves shallhave symmetric warp surfaces, unless otherwise noted
44、 in thereport.NOTE 2Typically a 45i/-45i/0j/90kmstape or 45i/0jmsfabric lami-nate should be selected such that a minimum of 5 % of the fibers lay ineach of the four principal orientations. This laminate design has beenfound to yield the highest likelihood of acceptable failure modes.8.2.2 Configurat
45、ion:8.2.2.1 Configuration AThe width of the specimen is 366 1 mm 1.50 6 0.05 in. and the length range is 200 to 300mm 8.0 to 12.0 in. The notch consists of a centrally locatedhole, 6 6 0.06 mm 0.250 6 0.003 in. in diameter, centered bylength to within 0.12 mm 0.005 in. and by width to within0.05 mm
46、0.002 in. While tabs may be used, they are notrequired and generally not needed, since the open hole acts assufficient stress riser to force failure in the notched region.Configuration A is preferred for the general laminate stackingsequences defined in 8.2.1 because it is long enough to ensurea uni
47、form strain field is achieved in the specimen outside of theinfluence of the hole.8.2.2.2 Configuration BThe width of the specimen is 366 1 mm 1.50 6 0.05 in. and the length range is 150 to 200mm 6.0 to 8.0 in. The notch consists of a centrally locatedhole, 6 6 0.06 mm 0.250 6 0.003 in. in diameter,
48、 centered bylength to within 0.12 mm 0.005 in. and by width to within0.05 mm 0.002 in. While tabs may be used, they are notrequired and generally not needed, since the open hole acts assufficient stress riser to force failure in the notched region.Configuration B is limited to quasi-isotropic lamina
49、te stackingsequences, typically a 45m/45m/0m/90mnstape or 45m/0mnsfabric laminate, with a specimen grip length of 35 to 55 mm1.4 to 2.0 in.NOTE 3The ungripped specimen length for Configuration B shall notbe less than 75 mm 3.0 in. as shorter ungripped lengths may result in an3Chris, R. M., “Comparison of Quasi-Isotropic Laminate Open-Hole TensionStrength vs. Specimen Length by Experimental Evaluation,” Bell HelicopterTextron Report BL2010-240, July 2010.FIG. 1 Schematic of Open-Hole Tension Test S
