1、Designation: D7248/D7248M 12 (Reapproved 2017)Standard Test Method forBearing/Bypass Interaction Response of Polymer MatrixComposite Laminates Using 2-Fastener Specimens1This standard is issued under the fixed designation D7248/D7248M; the number immediately following the designation indicates theye
2、ar of original adoption or, in the case 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 test method determines the uniaxial bearing/bypa
3、ssinteraction response of multi-directional polymer matrix com-posite laminates reinforced by high-modulus fibers by eitherdouble-shear tensile loading (Procedures A and C) or single-shear tensile or compressive loading (Procedure B) of atwo-fastener specimen. The scope of this test method is limite
4、dto net section (bypass) failure modes. Standard specimenconfigurations using fixed values of test parameters are de-scribed for each procedure. A number of test parameters maybe varied within the scope of the standard, provided that theparameters are fully documented in the test report. Thecomposit
5、e material forms are limited to continuous-fiber ordiscontinuous-fiber (tape or fabric, or both) reinforced com-posites for which the laminate is balanced and symmetric withrespect to the test direction. The range of acceptable testlaminates and thicknesses are described in 8.2.1.1.2 This test metho
6、d is consistent with the recommendationsof MIL-HDBK-17, which describes the desirable attributes ofa bearing/bypass interaction response test method.1.3 The two-fastener test configurations described in thistest method are similar to those in Test Method D5961/D5961M as well as those used by industr
7、y to investigate thebearing portion of the bearing/bypass interaction response forbolted joints, where the specimen may produce either a bearingfailure mode or a bypass failure mode. Should the testspecimen fail in a bearing failure mode rather than the desiredbypass mode, then the test should be co
8、nsidered to be a bearingdominated bearing/bypass test, and the data reduction andreporting procedures of Test Method D5961/D5961M shouldbe used instead of those given in this standard.1.4 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values st
9、ated 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 text the inch-pound units are shown inbrackets.1.5 This standard does not purport to a
10、ddress all of thesafety concerns, if any, associated with its use. It is 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.1.6 This international standard was developed in accor
11、-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 the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM
12、 Standards:2D792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics by DisplacementD883 Terminology Relating to PlasticsD2584 Test Method for Ignition Loss of Cured ReinforcedResinsD2734 Test Methods for Void Content of Reinforced PlasticsD3171 Test Methods for Constituent
13、 Content of CompositeMaterialsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for MoistureAbsorption Prop-erties and Equilibrium Conditioning of Polymer MatrixComposite MaterialsD5687/D5687M Guide for Preparation of Flat CompositePanels with Processing Guidelines for Specimen Prepa
14、ra-tionD5766/D5766M Test Method for Open-Hole TensileStrength of Polymer Matrix Composite LaminatesD5961/D5961M Test Method for Bearing Response of Poly-mer Matrix Composite Laminates1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibil
15、ity of Subcommittee D30.05 onStructural Test Methods.Current edition approved Aug. 1, 2017. Published May 2017. Originallyapproved in 2007. Last previous edition approved in 2012 as D7248/D7248M-12.DOI: 10.1520/D7248_D7248M-12R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org,
16、orcontact ASTM Customer Service at serviceastm.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
17、 standard was developed in accordance with 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.1
18、D6484/D6484M Test Method for Open-Hole CompressiveStrength of Polymer Matrix Composite LaminatesD6742/D6742M Practice for Filled-Hole Tension and Com-pression Testing of Polymer Matrix Composite LaminatesE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mec
19、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 MethodsE251 Tes
20、t Methods for Performance Characteristics of Me-tallic Bonded Resistance Strain GagesE456 Terminology Relating to Quality and StatisticsE1237 Guide for Installing Bonded Resistance Strain GagesE1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in Databases (With-dra
21、wn 2015)3E1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases (Withdrawn2015)32.2 Other Document:MIL-HDBK-17 Polymer Matrix Composites, Vol 1, Sec-tion 743. Terminology3.1 DefinitionsTerminology D3878 defines terms relatingto high-modulus fibers and the
22、ir 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 conflict between terms, Terminology D3878 shall haveprecedence over the other document
23、s.NOTE 1If the term represents a physical quantity, its analyticaldimensions are stated 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 fo
24、r time, for thermodynamic temperature,and nd for non-dimensional quantities. Use of these 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 gro
25、ss bypass stress, fgr_bypML-1T-2,nthe grossbypass stress for tensile loadings is calculated from the totalforce bypassing the fastener hole.3.2.2 net bypass stress, fnet_bypML-1T-2,nthe net bypassstress for tensile loading is calculated from the force bypassingthe fastener hole minus the force react
26、ed in bearing at thefastener.NOTE 2For compressive loadings the gross and net bypass stresses areequal and are calculated using the force that bypasses the fastener hole(since for the compressive loading case the bearing stress reaction is onthe same side of the fastener as the applied force, the fo
27、rce reacted inbearing does not bypass the fastener hole).NOTE 3Several alternate definitions for gross and net bypass stresshave been used historically in the aerospace industry. Comparison of datafrom tests conforming to this standard with historical data may need toaccount for differences in the b
28、ypass definitions.3.2.3 bearing area, L2,nthe area of that portion of aspecimen used to normalize applied loading into an effectivebearing stress; equal to the diameter of the fastener multipliedby the thickness of the specimen.3.2.4 bearing chord stiffness, EbrML-1T-2,nthe chordstiffness between tw
29、o specific bearing stress or bearing strainpoints in the linear portion of the bearing stress/bearing straincurve.3.2.5 bearing force, P MLT2,nthe in-plane force trans-mitted by a fastener to a specimen at the fastener hole.3.2.6 bearing strain, ,brnd,nthe normalized hole de-formation in a specimen,
30、 equal to the deformation of thebearing hole in the direction of the bearing force, divided bythe diameter of the hole.3.2.7 bearing strength, Fxbr_bypML-1T-2,nthe value ofbearing stress occurring at the point of bypass (net section)failure.3.2.8 bearing stress, brML-1T-2,nthe bearing forcedivided b
31、y the bearing area.3.2.9 diameter to thickness ratio, D/h nd, n in a bearingspecimen, the ratio of the hole diameter to the specimenthickness.3.2.9.1 DiscussionThe diameter to thickness ratio may beeither a nominal value determined from nominal dimensions oran actual value determined from measured d
32、imensions.3.2.10 edge distance ratio, e/D nd, n in a bearingspecimen, the ratio of the distance between the center of thehole and the specimen end to the hole diameter.3.2.10.1 DiscussionThe edge distance ratio may be eithera nominal value determined from nominal dimensions or anactual value determi
33、ned from measured dimensions.3.2.11 nominal value, na value, existing in name only,assigned to a measurable quantity for the purpose of conve-nient designation. Tolerances may be applied to a nominalvalue to define an acceptable range for the quantity.3.2.12 offset bearing strength, FxbroML-1T-2,nth
34、evalue of bearing stress, in the direction specified by thesubscript, at the point where a bearing chord stiffness line,offset along the bearing strain axis by a specified bearing strainvalue, intersects the bearing stress/bearing strain curve.3.2.12.1 DiscussionUnless otherwise specified, an offset
35、bearing strain of 2 % is to be used in this test method.3.2.13 width to diameter ratio, w/D nd, n in a bearingspecimen, the ratio of specimen width to hole diameter.3.2.13.1 DiscussionThe width to diameter ratio may beeither a nominal value determined from nominal dimensions oran actual value, deter
36、mined as the ratio of the actual specimenwidth to the actual hole diameter.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http:/dodssp.
37、daps.dla.mil.D7248/D7248M 12 (2017)23.2.14 ultimate bearing strength, FxbruML-1T-2,nthevalue of bearing stress, in the direction specified by thesubscript, at the maximum force capability of a bearingspecimen.3.2.15 ultimate gross bypass strength, Fxgr_bypML-1T-2,nthe value of gross bypass stress, i
38、n the direction specifiedby the subscript, at the maximum force capability of thespecimen.3.2.16 ultimate net bypass strength, Fxnet_bypML-1T-2,nthe value of net bypass stress, in the direction specified bythe subscript, at the maximum force capability of the specimen.3.3 Symbols:A = cross-sectional
39、 area of a specimenCV = coefficient of variation statistic of a sample populationfor a given property (in percent)d = fastener or pin diameterD = specimen hole diametere = distance, parallel to applied force, from hole center toend of specimen; the edge distanceExbr= bearing chord stiffness in the t
40、est direction specifiedby the subscriptf = distance, parallel to applied force, from hole edge to endof specimenFxbr_byp= bearing stress at the ultimate bypass strength inthe test direction specified by the subscriptFxgr_byp_c= ultimate compressive gross bypass strength inthe test direction specifie
41、d by the subscriptFxgr_byp_t= ultimate tensile gross bypass strength in the testdirection specified by the subscriptFxnet_byp_c= ultimate compressive net bypass strength in thetest direction specified by the subscriptFxnet_byp_t= ultimate tensile net bypass strength in the testdirection specified by
42、 the subscriptg = distance, perpendicular to applied force, from hole edgeto shortest edge of specimenh = specimen thicknessk = calculation factor used in bearing equations to distin-guish single-fastener tests from double-fastener testsLg= extensometer gage lengthn = number of specimens per sample
43、populationP = force carried by test specimenPf= force carried by test specimen at failurePmax= maximum force carried by test specimen prior tofailuresn-1= standard deviation statistic of a sample population fora given propertyw = specimen widthxi= test result for an individual specimen from the samp
44、lepopulation for a given propertyx = mean or average (estimate of mean) of a samplepopulation for a given property = extensional displacement = general symbol for strain, whether normal strain or shearstrainFIG. 1 Illustration of FHT, FHC, Bearing and Bearing/Bypass Bolted Joints Data and Bearing/By
45、pass Interaction Diagram (Refs 1-3)D7248/D7248M 12 (2017)3br= bearing strainbr= bearing stressw = specimen widthdcsk= countersink depthdfl= countersink flushness (depth or protrusion of the fas-tener in a countersunk hole)4. Summary of Test Method4.1 Bearing/Bypass ProceduresDefinition of the uniaxi
46、albearing/bypass interaction response requires data for varyingamounts of bearing and bypass forces at a fastener hole. Fig. 1shows a typical composite laminate bearing/bypass interactiondiagram (Refs 1-3),5along with illustrative data from varioustest types. Data from Practice D6742/D6742M and Test
47、Method D5961/D5961M define the 100 % bypass and bearingends of the interaction diagram. Rationale for the baselinebearing/bypass specimen geometry and fastener torques aregiven in 6.7 and 6.8. Procedures A and B of this test methodprovide data in the bypass/high bearing region, while Proce-dure C pr
48、ovides data in the bypass/low bearing region. Morecomplicated test setups have been used to develop data acrossthe full range of bearing/bypass interaction. This test method islimited to cases where the bearing and bypass loads are alignedin the same direction. It is also limited to uniaxial tensile
49、 orcompressive bypass loads. Test procedures for cases where thebearing and bypass loads act at different directions, or caseswith biaxial or shear bypass loads are outside the scope of thisstandard.4.1.1 Ultimate strength for all procedures is calculatedbased on the specimen gross cross-sectional area, disregardingthe presence of the hole. While the hole causes a stressconcentration and reduced net section, it is common industrypractice to develop notched design allowable strengths basedon gross section stre
