1、Designation: D7615/D7615M 11 (Reapproved 2018)Standard Practice forOpen-Hole Fatigue Response of Polymer Matrix CompositeLaminates1This standard is issued under the fixed designation D7615/D7615M; the number immediately following the designation indicates theyear of original adoption or, in the case
2、 of revision, 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.1. Scope1.1 This practice provides instructions for modifying staticopen-hole tensile and compressive st
3、rength test methods todetermine the fatigue behavior of composite materials sub-jected to cyclic tensile or compressive forces, or both. Thecomposite material forms are limited to continuous-fiber rein-forced polymer matrix composites in which the laminate isboth symmetric and balanced with respect
4、to the test direction.The range of acceptable test laminates and thicknesses aredescribed in 8.2.1.2 This practice supplements Test Methods D5766/D5766M and D6484/D6484M with provisions for testingspecimens under cyclic loading. Several important test speci-men parameters (for example, fatigue force
5、(stress) ratio) arenot mandated by this practice; however, repeatable resultsrequire that these parameters be specified and reported.1.3 This practice is limited to test specimens subjected toconstant amplitude uniaxial loading, where the machine iscontrolled so that the test specimen is subjected t
6、o repetitiveconstant amplitude force (stress) cycles. Either engineeringstress or applied force may be used as a constant amplitudefatigue variable. The repetitive loadings may be tensile,compressive, or reversed, depending upon the test specimenand procedure utilized.1.4 The values stated in either
7、 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 may result in non-conformancewith the standard.1.4.1 Within the t
8、ext the inch-pound units are shown inbrackets.1.5 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, health, and environmental practices and deter-mine the applic
9、ability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by th
10、e World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for MoistureAbsorption Prop-erties and Equilibrium Conditioning of Polymer MatrixCom
11、posite MaterialsD5766/D5766M Test Method for Open-Hole TensileStrength of Polymer Matrix Composite LaminatesD6484/D6484M Test Method for Open-Hole CompressiveStrength of Polymer Matrix Composite LaminatesE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mec
12、hanical TestingE83 Practice for Verification and Classification of Exten-someter SystemsE122 Practice for Calculating Sample Size to Estimate, WithSpecified Precision, the Average for a Characteristic of aLot or ProcessE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Ter
13、minology Relating to Quality and StatisticsE467 Practice for Verification of Constant Amplitude Dy-namic Forces in an Axial Fatigue Testing System1This practice is under the jurisdiction of ASTM Committee D30 on CompositeMaterials and is the direct responsibility of Subcommittee D30.05 on Structural
14、 TestMethods.Current edition approved April 1, 2018. Published May 2018. Originallyapproved in 2011. Last previous edition approved in 2011 as D7615/D7615M11.DOI: 10.1520/D7615_D7615M-11R18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at servi
15、ceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance wi
16、th internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1E739 Practice for StatisticalAnalysis of
17、 Linear or LinearizedStress-Life (S-N) and Strain-Life (-N) Fatigue DataE1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in Databases (With-drawn 2015)3E1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases (Withdrawn20
18、15)3E1823 Terminology Relating to Fatigue and Fracture Testing3. Terminology3.1 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 E
19、1823defines terms relating to fatigue. Terminology E456 andPractice E177 define terms relating to statistics. In the event ofa conflict between terms, Terminology D3878 shall haveprecedence over the other standards.NOTE 1If the term represents a physical quantity, its analyticaldimensions are stated
20、 immediately following 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, for thermodynamic temperature,and nd for non-dimensional quantities. Use of the
21、se symbols is restrictedto analytical dimensions when used with square brackets, as the symbolsmay have other definitions when used without the brackets.3.2 Definitions of Terms Specific to This Standard:3.2.1 constant amplitude loading, nin fatigue, a loading inwhich all of the peak values of force
22、 (stress) are equal and allof the valley values of force (stress) are equal.3.2.2 fatigue loading transition, nin the beginning offatigue loading, the number of cycles before the force (stress)reaches the desired peak and valley values.3.2.3 force, P MLT2, nthe total force carried by a testspecimen.
23、3.2.4 force (stress) ratio, R nd, nin fatigue loading, theratio of the minimum applied force (stress) to the maximumapplied force (stress).3.2.5 frequency, f T1, nin fatigue loading, the number offorce (stress) cycles completed in 1 s (Hz).3.2.6 nominal value, na value, existing in name only,assigne
24、d 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.3.2.7 peak, nin fatigue loading, the occurrence where thefirst derivative of the force (stress) versus time changes frompositive to negati
25、ve sign; the point of maximum force (stress)in constant amplitude loading.3.2.8 residual strength, ML-1T-2, nthe value of force(stress) required to cause failure of a specimen under quasi-static loading conditions after the specimen is subjected tofatigue loading.3.2.9 run-out, nin fatigue, an upper
26、 limit on the number offorce cycles to be applied.3.2.10 spectrum loading, nin fatigue, a loading in whichthe peak values of force (stress) are not equal or the valleyvalues of force (stress) are not equal (also known as variableamplitude loading or irregular loading).3.2.11 valley, nin fatigue load
27、ing, the occurrence wherethe first derivative of the force (stress) versus time changesfrom negative to positive sign; the point of minimum force(stress) in constant amplitude loading.3.2.12 wave form, nthe shape of the peak-to-peak varia-tion of the force (stress) as a function of time.3.3 Symbols:
28、A = Cross-sectional area of a specimenK = specimen chord stiffness, P/Ki= specimen chord stiffness prior to fatigue cyclesKN= specimen chord stiffness after N fatigue cyclesD = specimen hole diameterh = specimen thicknessN = number of constant amplitude cyclesN= change in chord stiffness after N fat
29、igue cyclesP = force carried by specimenPmaxq= peak force under quasi-static loading for measure-ment of stiffnessPminq= valley force under quasi-static loading for measure-ment of stiffnessw = specimen width = crosshead or extensometer translationalt= alternating open hole stress during fatigue loa
30、dingohm= maximum cyclic open hole stress magnitude, givenby the greater of the absolute values of maxand minmax= value of stress corresponding to the peak value offorce (stress) under constant amplitude loadingmaxq= value of stress corresponding to the peak value offorce (stress) under quasi-static
31、loading for measure-ment of stiffness, given by the greater of theabsolute values of maxand 0.5 minmean= mean normal stress during fatigue loadingmin= value of stress corresponding to the valley value offorce (stress) under constant amplitude loadingminq= value of stress corresponding to the valley
32、value offorce (stress) under quasi-static loading for measure-ment of stiffness, given by the greater of theabsolute values of minand 0.5 max4. Summary of Practice4.1 In accordance with Test Methods D5766/D5766M orD6484/D6484M, but under constant amplitude fatigue loading,perform a uniaxial test of
33、an open-hole specimen. Cycle thespecimen between minimum and maximum axial forces(stresses) at a specified frequency. At selected cyclic intervals,determine the specimen stiffness from a force versus deforma-tion curve obtained by quasi-statically loading the specimenthrough one tension, compression
34、 or tension-compressioncycle as applicable. Determine the number of force cycles atwhich failure occurs (or at which a predetermined change inspecimen stiffness is observed), for a specimen subjected to aspecific force (stress) ratio and stress magnitude.3The last approved version of this historical
35、 standard is referenced onwww.astm.org.D7615/D7615M 11 (2018)25. Significance and Use5.1 This practice provides supplemental instructions forusing Test Methods D5766/D5766M or D6484/D6484M toobtain open-hole fatigue data for material specifications, re-search and development, material design allowab
36、les, andquality assurance. The primary property that results is thefatigue life of the test specimen under a specific loading andenvironmental condition. Replicate tests may be used to obtaina distribution of fatigue life for specific material types, lami-nate stacking sequences, environments, and l
37、oading conditions.Guidance in statistical analysis of fatigue data, such as deter-mination of linearized stress life (S-N) curves, can be found inPractice E739.5.2 This practice can be utilized in the study of fatiguedamage in a polymer matrix composite open-hole specimensuch as the occurrence of mi
38、croscopic cracks, fiber fractures, ordelaminations. The change in strength associated with fatiguedamage may be determined by discontinuing cyclic loading toobtain the static strength using Test Methods D5766/D5766Mor D6484/D6484M.NOTE 2This practice may be used as a guide to conduct variableamplitu
39、de loading. This information can be useful in the understanding offatigue behavior of composite structures under spectrum loadingconditions, but is not covered in this standard.5.3 Factors that influence open-hole fatigue response andshall therefore be reported include the following: material,method
40、s of material fabrication, accuracy of lay-up, laminatestacking sequence and overall thickness, specimen geometry,specimen preparation (especially of the hole), specimenconditioning, environment of testing, type of support fixture,specimen alignment and gripping, test frequency, force (stress)ratio,
41、 normal stress magnitude, void content, and volumepercent reinforcement. Properties that result include the fol-lowing:5.3.1 Specimen stiffness versus fatigue life curves for se-lected normal stress values.5.3.2 Normal stress versus specimen stiffness curves atselected cyclic intervals.5.3.3 Normal
42、stress versus fatigue life curves for selectedstress ratio values.6. Interferences6.1 Force (Stress) RatioResults are affected by the force(stress) ratio under which the tests are conducted. Experiencehas demonstrated that reversed (tension-compression) forceratios are critical for fatigue-induced d
43、amage in open holespecimens, with fully reversed tension-compression (R = 1)being the most critical force ratio (1)4.6.2 Loading FrequencyResults are affected by the loadingfrequency at which the test is conducted. High cyclic rates mayinduce heating within the specimen that may cause variationsin s
44、pecimen temperature and properties of the composite asdiscussed in 11.3.2. The temperature of the specimen should bemonitored, and the frequency should be kept low enough toavoid significant temperature variations, unless that is a factorto be studied during the test. For example, loading frequencie
45、sup to 5Hz have been used successfully. Varying the cyclicfrequency during the test is generally not recommended, as theresponse may be sensitive to the frequency utilized and theresultant thermal history.6.3 EnvironmentResults are affected by the environmentalconditions under which the tests are co
46、nducted. Laminatestested in various environments can exhibit significant differ-ences in both strength and failure mode. Experience hasdemonstrated that elevated temperature, humid environmentsare generally critical for open hole fatigue-induced damage (1).However, critical environments must be asse
47、ssed indepen-dently for each material system, stacking sequence and loadingcondition tested.6.4 Method of Stiffness MeasurementResults are affectedby the method used to monitor specimen stiffness. Force versusdeformation data provide an indication of specimen stiffnesschange due to damage formation.
48、 However, the accuracy ofsuch measurements is affected by factors such as strainindicator accuracy, signal noise, gage length and extensometerslippage, extensometer placement/location, grip slippage, andload frame stiffness (for crosshead deflection data), and soforth.6.5 Hole PreparationResults are
49、 affected by the holepreparation procedures.6.6 OtherAdditional sources of potential data scatter aredocumented in Test Methods D5766/D5766M and D6484/D6484M.7. Apparatus7.1 General ApparatusGeneral apparatus shall be in ac-cordance with Test Method D5766/D5766M Configuration Afor tension-tension fatigue loading, and in accordance withTestMethod D6484/D6484M Procedure A for tension-compressionand compression-compression fatigue loading. The micrometeror gage used shall be capable of determining the hole diameterto 6 0.02
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