1、Designation:D7248/D7248M08 Designation: D7248/D7248M 12Standard 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 indica
2、tes theyear 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 bea
3、ring/bypass interaction response of multi-directional polymer matrix compositelaminates reinforced by high-modulus fibers by either double-shear tensile loading (Procedures A and C) or single-shear tensileor compressive loading (Procedure B) of a two-fastener specimen. The scope of this test method
4、is limited to net section (bypass)failure modes. Standard specimen configurations using fixed values of test parameters are described for each procedure. A numberof test parameters may be varied within the scope of the standard, provided that the parameters are fully documented in the testreport. Th
5、e composite material forms are limited to continuous-fiber or discontinuous-fiber (tape or fabric, or both) reinforcedcomposites for which the laminate is balanced and symmetric with respect to the test direction. The range of acceptable testlaminates and thicknesses are described in 8.2.1.1.2 This
6、test method is consistent with the recommendations of MIL-HDBK-17, which describes the desirable attributes of abearing/bypass interaction response test method.1.3 The two-fastener test configurations described in this test method are similar to those in Test Method D5961/D5961M aswell as those used
7、 by industry to investigate the bearing portion of the bearing/bypass interaction response for bolted joints, wherethe specimen may produce either a bearing failure mode or a bypass failure mode. Should the test specimen fail in a bearing failuremode rather than the desired bypass mode, then the tes
8、t should be considered to be a bearing dominated bearing/bypass test, andthe data reduction and reporting procedures of Test Method D5961/D5961M should be used instead of those given in this standard.1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standa
9、rd. Within the text theinch-pound units are shown in brackets. The values stated in each system aremay not be exact equivalents; therefore, each systemmustshall be used independently of the other. Combining values from the two systems may result in non-conformance with thestandard.1.4.1 Within the t
10、ext the inch-pound units are shown in brackets.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regul
11、atorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D792 Test Methods for Density and Specific Gravity (Relative Density) of Plastics by DisplacementD883 Terminology Relating to PlasticsD2584 Test Method for Ignition Loss of Cured Reinforced ResinsD2734 Test Methods for Void Con
12、tent of Reinforced PlasticsD3171 Test Methods for Constituent Content of Composite MaterialsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix CompositeMaterialsD5687/D5687M Guide for Preparation of Flat
13、 Composite Panels with Processing Guidelines for Specimen PreparationD5766/D5766M Test Method for Open-Hole Tensile Strength of Polymer Matrix Composite LaminatesD5961/D5961M Test Method for Bearing Response of Polymer Matrix Composite Laminates1This test method is under the jurisdiction of ASTM Com
14、mittee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.05 on Structural TestMethods.Current edition approved Sept.April 1, 2008.2012. Published October 2008.May 2012. Originally approved in 2007. Last previous edition approved in 20072008 asD7248/D7248M-078. DOI: 10.1
15、520/D7248_D7248M-0812.2For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.1This document is not an ASTM standar
16、d and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases o
17、nly the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.D6484/D6484M Test Method for Open-Hole Compressive Strength of Polymer Matrix Compos
18、ite LaminatesD6742/D6742M Practice for Filled-Hole Tension and Compression Testing of Polymer Matrix Composite LaminatesE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE83 Practice for Verification and Classification of Extensometer Syst
19、emsE122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot orProcessE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE251 Test Methods for Performance Characteristics of Metallic Bonded Resistance Strain Gaug
20、esE456 Terminology Relating to Quality and StatisticsE1237 Guide for Installing Bonded Resistance Strain GagesE1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in DatabasesE1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Da
21、tabases2.2 Other Document:MIL-HDBK-17 Polymer Matrix Composites, Vol 1, Section 733. Terminology3.1 DefinitionsTerminology D3878 defines terms relating to high-modulus fibers and their composites. Terminology D883defines terms relating to plastics. Terminology E6 defines terms relating to mechanical
22、 testing. Terminology E456 and PracticeE177 define terms relating to statistics. In the event of a conflict between terms, Terminology D3878 shall have precedence overthe other documents.NOTE 1If the term represents a physical quantity, its analytical dimensions are stated immediately following the
23、term (or letter symbol) infundamental dimension form, using the following ASTM standard symbology for fundamental dimensions, shown within square brackets: M for mass,L for length, T for time, u for thermodynamic temperature, and nd for non-dimensional quantities. Use of these symbols is restricted
24、to analyticaldimensions when used with square brackets, as the symbols may have other definitions when used without the brackets.3.2 Definitions of Terms Specific to This Standard3.2.1 gross bypass stress, fgr_bypML-1T-2, nthe gross bypass stress for tensile loadings is calculated from the total for
25、cebypassing the fastener hole.3.2.2 net bypass stress, fnet_bypML-1T-2, nthe net bypass stress for tensile loading is calculated from the force bypassingthe fastener hole minus the force reacted in bearing at the fastener.NOTE 2For compressive loadings the gross and net bypass stresses are equal and
26、 are calculated using the force that bypasses the fastener hole (sincefor the compressive loading case the bearing stress reaction is on the same side of the fastener as the applied force, the force reacted in bearing does notbypass the fastener hole).NOTE 3Several alternate definitions for gross an
27、d net bypass stress have been used historically in the aerospace industry. Comparison of data fromtests conforming to this standard with historical data may need to account for differences in the bypass definitions.3.2.3 bearing area, L2, nthe area of that portion of a specimen used to normalize app
28、lied loading into an effective bearingstress; equal to the diameter of the fastener multiplied by the thickness of the specimen.3.2.4 bearing chord stiffness, EbrML-1T-2, nthe chord stiffness between two specific bearing stress or bearing strain pointsin the linear portion of the bearing stress/bear
29、ing strain curve.3.2.5 bearing force, P MLT2, nthe in-plane force transmitted by a fastener to a specimen at the fastener hole.3.2.6 bearing strain, ,brnd, nthe normalized hole deformation in a specimen, equal to the deformation of the bearing holein the direction of the bearing force, divided by th
30、e diameter of the hole.3.2.7 bearing strength, Fxbr_bypML-1T-2, nthe value of bearing stress occurring at the point of bypass (net section) failure.3.2.8 bearing stress, sbrML-1T-2, nthe bearing force divided by the bearing area.3.2.9 diameter to thickness ratio, D/h nd, n in a bearing specimen, the
31、 ratio of the hole diameter to the specimen thickness.3.2.9.1 DiscussionThe diameter to thickness ratio may be either a nominal value determined from nominal dimensions or anactual value determined from measured dimensions.3.2.10 edge distance ratio, e/D nd, n in a bearing specimen, the ratio of the
32、 distance between the center of the hole andthe specimen end to the hole diameter.3.2.10.1 DiscussionThe edge distance ratio may be either a nominal value determined from nominal dimensions or an actualvalue determined from measured dimensions.3.2.11 nominal value, na value, existing in name only, a
33、ssigned to a measurable quantity for the purpose of convenientdesignation. Tolerances may be applied to a nominal value to define an acceptable range for the quantity.3.2.12 offset bearing strength, FxbroML-1T-2, nthe value of bearing stress, in the direction specified by the subscript, at thepoint
34、where a bearing chord stiffness line, offset along the bearing strain axis by a specified bearing strain value, intersects thebearing stress/bearing strain curve.3Available from Standardization Documents Order Desk, DODSSP, Bldg. 4, Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, Attn: NPO
35、DS.http:/dodssp.daps.dla.mil.D7248/D7248M 1223.2.12.1 DiscussionUnless otherwise specified, an offset 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 bearing specimen, the ratio of specimen width to hole diameter.3.2.13.1 DiscussionThe width to
36、diameter ratio may be either a nominal value determined from nominal dimensions or anactual value, determined as the ratio of the actual specimen width to the actual hole diameter.3.2.14 ultimate bearing strength, FxbruML-1T-2, nthe value of bearing stress, in the direction specified by the subscrip
37、t, atthe maximum force capability of a bearing specimen.3.2.15 ultimate gross bypass strength, Fxgr_bypML-1T-2, nthe value of gross bypass stress, in the direction specified by thesubscript, at the maximum force capability of the specimen.3.2.16 ultimate net bypass strength, Fxnet_bypML-1T-2, nthe v
38、alue of net bypass stress, in the direction specified by thesubscript, at the maximum force capability of the specimen.3.3 Symbols:A = cross-sectional area of a specimenCV = coefficient of variation statistic of a sample population for a given property (in percent)d = fastener or pin diameterD = spe
39、cimen hole diametere = distance, parallel to applied force, from hole center to end of specimen; the edge distanceExbr= bearing chord stiffness in the test direction specified by the subscriptf = distance, parallel to applied force, from hole edge to end of specimenFxbr_byp= bearing stress at the ul
40、timate bypass strength in the test direction specified by the subscriptFxgr_byp_c= ultimate compressive gross bypass strength in the test direction specified by the subscriptFxgr_byp_t= ultimate tensile gross bypass strength in the test direction specified by the subscriptFxnet_byp_c= ultimate compr
41、essive net bypass strength in the test direction specified by the subscriptFxnet_byp_t= ultimate tensile net bypass strength in the test direction specified by the subscriptg = distance, perpendicular to applied force, from hole edge to shortest edge of specimenh = specimen thicknessk = calculation
42、factor used in bearing equations to distinguish single-fastener tests from double-fastener testsLg= extensometer gage lengthn = number of specimens per sample populationFIG. 1 Illustration of FHT, FHC, Bearing and Bearing/Bypass Bolted Joints Data and Bearing/Bypass Interaction Diagram (Refs 1-3)D72
43、48/D7248M 123P = force carried by test specimenPf= force carried by test specimen at failurePmax= maximum force carried by test specimen prior to failuresn-1= standard deviation statistic of a sample population for a given propertyw = specimen widthxi= test result for an individual specimen from the
44、 sample population for a given propertyx 5 = mean or average (estimate of mean) of a sample population for a given propertyd = extensional displacement = general symbol for strain, whether normal strain or shear strainbr= bearing strainsbr= bearing stressw = specimen widthdcsk= countersink depthdfl=
45、 countersink flushness (depth or protrusion of the fastener in a countersunk hole)4. Summary of Test Method4.1 Bearing/Bypass ProceduresDefinition of the uniaxial bearing/bypass interaction response requires data for varyingamounts of bearing and bypass forces at a fastener hole. Fig. 1 shows a typi
46、cal composite laminate bearing/bypass interactiondiagram (Refs 1-3),4along with illustrative data from various test types. Data from Practice D6742/D6742M and Test MethodD5961/D5961M define the 100 % bypass and bearing ends of the interaction diagram. Rationale for the baseline bearing/bypassspecime
47、n geometry and fastener torques are given in 6.7 and 6.8. Procedures A and B of this test method provide data in thebypass/high bearing region, while Procedure C provides data in the bypass/low bearing region. More complicated test setups havebeen used to develop data across the full range of bearin
48、g/bypass interaction. This test method is limited to cases where the bearingand bypass loads are aligned in the same direction. It is also limited to uniaxial tensile or compressive bypass loads. Test proceduresfor cases where the bearing and bypass loads act at different directions, or cases with b
49、iaxial or shear bypass loads are outside thescope of this standard.4.1.1 Ultimate strength for all procedures is calculated based on the specimen gross cross-sectional area, disregarding thepresence of the hole. While the hole causes a stress concentration and reduced net section, it is common industry practice todevelop notched design allowable strengths based on gross section stress to account for various stress concentrations (fastenerholes, free edges, flaws, damage, and so forth) not explicitly modeled in th
