1、Designation: D8131/D8131M 171Standard Practice forTensile Properties of Tapered and Stepped Joints ofPolymer Matrix Composite Laminates1This standard is issued under the fixed designation D8131/D8131M; the number immediately following the designation indicates theyear of original adoption or, in the
2、 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.1NOTEEditorial changes made in September 2017.1. Scope1.1 This test practice defines the procedure
3、for determina-tion of the tensile strength of a tapered or stepped joint ofpolymer matrix composite materials. It is applicable to second-ary bonded or co-bonded laminates with either unidirectionalplies or woven fabric reinforcements. The materials to bebonded may be different material systems. In
4、the bondline, aseparate adhesive material may or may not be used (example:adhesives may be used with a prepreg system or may not beused with a wet lay-up repair system). The range of acceptabletest laminates and thicknesses is described in 8.2.1.1.2 This practice supplements Test Method D3039/D3039M
5、for tensile loading. Several important test specimen parameters(for example, joint length, ply overlaps, step depth, and taperratio) are not mandated by this practice, however, theseparameters are required to be specified and reported to supportrepeatable results.1.3 Unidirectional (0 ply orientatio
6、n) tape composites,textile composites, as well as multidirectional compositelaminates, can be tested.1.4 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.1.4.1 Within the text the inch-pound units are shown inbrackets. The values stated in each system
7、 are not exactequivalents; therefore, each system must be used indepen-dently of the other. Combining values from the two systemsmay result in nonconformance with the standard1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibi
8、lity of the user of this standard to establish appro-priate safety, health and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization e
9、stablished 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 Standards:2D792 Test Methods for Density and Specific Gravity (Rela-ti
10、ve Density) of Plastics by DisplacementD883 Terminology Relating to PlasticsD3039/D3039M Test Method for Tensile Properties of Poly-mer Matrix Composite MaterialsD3171 Test Methods for Constituent Content of CompositeMaterialsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for Mois
11、tureAbsorption Prop-erties and Equilibrium Conditioning of Polymer MatrixComposite MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE122 Practice for Calculating Sample Size to Estimate, WithSpecified Precision, the Average for a
12、 Characteristic of aLot or ProcessE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE2533 Guide for Nondestructive Testing of Polymer MatrixComposites Used in Aerospace Applications2.2 Other Documents:3CMH-17 Composite Materia
13、ls Handbook-17 Volume I3. Terminology3.1 Terminology D3878 defines terms relating to high-modulus fibers and their composites. Terminology D883 de-fines terms relating to plastics. Terminology E6 defines terms1This practice is under the jurisdiction of ASTM Committee D30 on CompositeMaterials and is
14、 the direct responsibility of Subcommittee D30.05 on Structural TestMethods.Current edition approved Aug. 1, 2017. Published August 2017. Originallyapproved in 2017. DOI: 10.1520/D8131_D8131M-17E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service
15、at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available for purchase in print and e-book format from SAE International,http:/books.sae.org/r-422/.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C7
16、00, West Conshohocken, PA 19428-2959. United StatesThis international 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 W
17、orld Trade Organization Technical Barriers to Trade (TBT) Committee.1relating to mechanical testing. Terminology E456 and PracticeE177 define terms relating to statistics. In the event of aconflict between terms, Terminology D3878 shall have prece-dence over the other terminology standards.NOTE 1If
18、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 for time, for
19、 thermodynamic temperature,and nd for nondimensional 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 co-bonded (repa
20、ir) laminatethe co-bonded laminateis the laminate that is bonded to the parent pre-cured laminateand cured in a second cure cycle.3.2.2 joint tensile strengthultimate tensile force experi-enced by the test specimen divided by the initial width of thejoint area and the nominal thickness of the parent
21、 laminate.3.2.3 nominal valuea value, existing in name only, as-signed to a measureable property for the purpose of convenientdesignation. Tolerances may be applied to a nominal value todefine and acceptable range for the property.3.2.4 parent laminatethe parent laminate is the laminatethat is cured
22、 during the first cure cycle.3.2.5 secondary bonded (repair) laminatethe secondarybonded laminate is a pre-cured laminate that is bonded to theparent pre-cured laminate using a separate adhesive material(sometimes referred to as a pre-cured patch repair).3.3 Symbols:3.3.1 CVsample coefficient of var
23、iation, in percent3.3.2 Fptuultimate tensile strength, based on parent lami-nate thickness3.3.3 Frtuultimate tensile strength, based on repair lami-nate thickness3.3.4 hpspecimen nominal parent laminate thickness asspecified by the test requestor (nominal ply thickness may beavailable from the relev
24、ant material specification)3.3.5 hrspecimen nominal repair laminate thickness asspecified by the test requestor (nominal ply thickness may beavailable from the relevant material specification)3.3.6 Njultimate joint running force per ply3.3.7 nnumber of specimens3.3.8 npnumber of parent laminate plie
25、s3.3.9 Pfmaximum force carried by test specimen at failure3.3.10 Sn1standard deviation statistic of a sample popu-lation for a given property3.3.11 wspecimen width3.3.12 xitest result for an individual coupon from thesample population for a given property3.3.13 xmean or average (estimate of mean) of
26、 a samplepopulation for a given property4. Summary of Practice4.1 Tapered or Stepped Joint Tensile StrengthIn accor-dance with Test Method D3039/D3039M, but using a taperedor stepped joint configured specimen (Fig. 1 or Fig. 2), performa uniaxial tension test of the composite laminate joint speci-me
27、n.5. Significance and Use5.1 This test practice is designed to produce tensile propertydata for material specifications, research and development,quality assurance, and structural design and analysis. Factorsthat influence the tensile response and should therefore bereported include the following: m
28、aterials (laminates andadhesive), methods of material preparation including surfacepreparation prior to bonding, lay-ups, specimen stackingsequence, joint taper ratio or step length, ply overlap length,material relative thicknesses and stiffness of the parent andrepair laminates, adhesive bond stiff
29、ness, specimenpreparation, specimen conditioning, environment of testing,specimen alignment and gripping, speed of testing, time attemperature, void content, and volume percent reinforcement.Properties in the test direction, which may be obtained fromthis test practice, include the following:5.1.1 U
30、ltimate tensile strength (based on the nominal parentmaterial thickness), (Fptu).5.1.2 Ultimate tensile strength (based on the nominal repairmaterial thickness), (Frtu).5.1.3 Ultimate running force per repair ply, (Nj).6. Interferences6.1 Material and Specimen PreparationPoor material fab-rication p
31、ractices, lack of control of fiber alignment, anddamage induced by improper coupon machining are knowncauses of high material data scatter in composites. For thebonded joint specimens, the quality of the co-cured laminate(ply positioning, lengths, impregnation for wet lay-up materialsystems), lack o
32、f orientation control of the parent laminate orpre-cured patch, and quality of the bond between the parentand pre-cured or co-cured bonded laminates will have signifi-cant effects on the test results.6.2 GrippingA high percentage of grip-induced failures,especially when combined with high material d
33、ata scatter, is anindicator of specimen gripping problems. Specimen grippingmethods are discussed further in Test Method D3039/D3039M.Specimen shall not be gripped within 25 mm 1.0 in. of thebondline (joint) area.6.3 System AlignmentExcessive bending will cause pre-mature failure, as well as highly
34、inappropriate load-versus-deflection response. Every effort should be made to eliminateexcess bending from the test system. Bending may occur as aresult of misaligned grips or from specimens themselves ifimproperly installed in the grips or out-of-tolerance caused bypoor specimen preparation. If the
35、re are differences in materialthickness and stiffness of the parent versus repair laminates, itmay be necessary to intentionally induce distortion and mis-alignment upon gripping or to employ the use of a shim(s) onthe thinner part of the specimen and accept the inducedmoment. If there is any doubt
36、as to the alignment inherent in aD8131/D8131M 1712given test machine, then the alignment should be checked asdiscussed in Test Method D3039/D3039M.6.4 Specimen DesignThe bonded joint test specimen in-volves a parent and a repair laminate. These two laminatestypically do not use the same material sys
37、tem. There are anumber of variables and factors which influence the selectionof the repair laminate lay-up relative to the parent laminate.Generally the repair lay-up is designed to match or slightlyexceed the stiffness of the parent laminate, and ideally therepair material type (fabric or tape) and
38、 the ply thicknesses arethe same as for the parent material. When they are different,repair design compromises are necessary to obtain sufficientrepair stiffness and strength while not making the repair thickerthan the parent laminate. Details of repair design are beyondthe scope of this test practi
39、ce. When filler plies or extra repairplies are used, or when the repair material thicknesses do notmatch the parent material thicknesses, a difference in joint testspecimen thickness on the two ends will occur, leading to someinduced bending, even if shims are applied. Also, any unbal-ance or asymme
40、try in the repair lay-up from filler plies, therepair laminate, or from extra repair plies may also lead tosome induced bending. The results from this test practice areNotes:1) Interpret drawing in accordance with ANSI Y14.5M-1982, subject to the following:2) All dimensions in millimeters with decim
41、al tolerances as follows:No Decimal .X .XX3 1 .33) All angles have a tolerance of 65.4) Ply orientation direction tolerance relative to -A- within 6.5.5) Finish on machine edges not to exceed 1.6= (symbology in accordance with ASA B46.1, with roughness height in micrometers).6) Values to be provided
42、 for the following, subject to any ranges shown in the field of drawing: material, lay-up, ply orientation reference relative to -A-, overall length,gage length, coupon thickness, tab material, tab thickness, tab length, tab bevel angle, tab adhesive.7) Repair specimen length design should not excee
43、d scarf joint length by more than 20 %.FIG. 1 Tensile Tapered and Stepped Joint Specimen Geometry (SI)D8131/D8131M 1713reported as simple stress and force-per-width values; the jointspecimen design will influence the validity of these reportedresults for use with bonded repair analysis methods.6.4.1
44、 Step Joint Filler PliesThe stepped joint specimenshould have a filler ply to avoid waviness in the repair plies.The filler ply should ideally be the same thickness as thebottom ply in the parent laminate. The standard test specimenconfiguration in this practice for unidirectional tape materialsuses
45、 a +45 ply as the filler ply; this may induce some bendingor twisting in the specimen under load. If an equivalentthickness fabric repair material is available, that could be usedfor the filler ply to provide a balanced lay-up.6.5 Edge Effects in Angle Ply LaminatesPremature failurecan occur as a re
46、sult of edge softening in laminates containingoff-axis plies. Because of this, the strength for angle plylaminates can be lower than expected. For multidirectionallaminates containing significant axial fibers, the effect is not assignificant.Notes:1) Interpret drawing in accordance with ANSI Y14.5M-
47、1982, subject to the following:2) All dimensions in inches with decimal tolerances as follows:No Decimal .X .XX.1 .03 .013) All angles have a tolerance of 65.4) Ply orientation direction tolerance relative to -A- within 6.5.5) Finish on machine edges not to exceed 64= (symbology in accordance with A
48、SA B46.1, with roughness height in microinches).6) Values to be provided for the following, subject to any ranges shown in the field of drawing: material, lay-up, ply orientation reference relative to -A-, overall length,gage length, coupon thickness, tab material, tab thickness, tab length, tab bev
49、el angle, tab adhesive.7) Repair specimen length design should not exceed scarf joint length by more than 20 %.FIG. 2 Tensile Tapered and Stepped Joint Specimen Geometry (Inch-Pound)D8131/D8131M 17146.6 EnvironmentResults are affected by the environmentalconditions under which the tests are conducted. Laminatestested in various environments can exhibit significant differ-ences in both failure force and failure mode. Experience hasdemonstrated that cold-temperature environments can be criti-cal f
