1、Designation: D7616/D7616M 11Standard Test Method forDetermining Apparent Overlap Splice Shear StrengthProperties of Wet Lay-Up Fiber-Reinforced Polymer MatrixComposites Used for Strengthening Civil Structures1This standard is issued under the fixed designation D7616/D7616M; the number immediately fo
2、llowing the designation indicates 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 meth
3、od describes the requirements for samplepreparation and tensile testing of single-lap shear splicesformed with fiber-reinforced polymer (FRP) composite mate-rials commonly used for strengthening of structures made ofmaterials such as metals, timber, masonry, and reinforcedconcrete. The objective of
4、this method is to determine theapparent shear strength of an overlap splice joint through theapplication of a far-field tensile force. The method applies towet lay-up FRP material systems fabricated on site or in alaboratory setting. The FRP composite may be of eitherunidirectional (0) or cross-ply
5、(0/90 type) reinforcement. Forcross-ply laminates, the construction may be achieved usingmultiple-layers of unidirectional fibers at either 0 or 90, or oneor more layers of stitched or woven 0/90 fabrics. The compos-ite material forms are limited to continuous fiber or discon-tinuous fiber-reinforce
6、d composites in which the laminate isbalanced and symmetric with respect to the test direction. Themethod is often used to determine the length of the overlapsplice needed to ensure that a tension failure occurs in thematerial away from the splice rather than the splice connectionitself.1.2 The valu
7、es 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 may result in non-conformancewith the standard
8、.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 safety and health practices and determine the app
9、lica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD3039/D3039M Test Method for Tensile Properties ofPolymer Matrix Composite MaterialsD3878 Terminology for Composite MaterialsD4896 Guide for Use ofAdhesive-Bonded Single
10、 Lap-JointSpecimen Test ResultsD5229/D5229M Test Method for Moisture AbsorptionProperties and Equilibrium Conditioning of Polymer Ma-trix Composite MaterialsD5687/D5687M Guide for Preparation of Flat CompositePanels with Processing Guidelines for Specimen Prepara-tionD7565/D7565M Test Method for Det
11、ermining TensileProperties of Fiber Reinforced Polymer Matrix Compos-ites Used for Strengthening of Civil StructuresE6 Terminology Relating to Methods of Mechanical TestingE122 Practice for Calculating Sample Size to Estimate,With Specified Precision, the Average for a Characteristicof a Lot or Proc
12、essE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and Statistics2.2 Other Standards:3DOT/FAA/AR-01/33 Investigation of Thick Bondline Ad-hesive Joints, June 2001DOT/FAA/AR-02/97 Shear Stress-Strain Data for Struc-tural Adhesives, Novembe
13、r 20023. Terminology3.1 DefinitionsTerminology D3878 defines terms relatingto high-modulus fibers and their composites. TerminologyD883 defines terms relating to plastics. Terminology E6 defines1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct
14、responsibility of Subcommittee D30.05 onStructural Test Methods.Current edition approved March 1, 2011. Published May 2011. DOI: 10.1520/D7616_D7616M-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMSt
15、andards volume information, refer to the standards Document Summary page onthe ASTM website.3Available at the Federal Aviation Administration William J. Hughes TechnicalCenter Full-Text Technical Reports page: http:/207.67.203.68/F10011.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C7
16、00, West Conshohocken, PA 19428-2959, United States.terms 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 standards.3.2 Definitions of Terms Specific
17、to This Standard:3.2.1 nominal value, na value, existing in name only,assigned 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.3.2.2 screed, vto move a flat rule along the top of asaturate
18、d laminate to level the top of the laminate andsimultaneously remove excess resin.3.2.3 wet lay-up FRP composite, nan FRP compositematerial fabricated by manually impregnating dry fibers with amatrix of polymeric resin. Semi-automated processes such asmachine-aided wetting of fabrics before placemen
19、t or vacuumaided impregnation of laminates after placement are consideredpart of wet lay-up FRP. For civil infrastructure strengtheningapplications, the degree of control over the volume fractions offibers, matrix, and voids as well as the overall cross-sectionalgeometry in wet lay-up FRP composites
20、 may be less than thatfor shop manufactured FRP composites on account of themanual process. For strengthening applications, wet lay-upFRP composites are typically applied to the substrate at thesame time the dry fiber is impregnated. The impregnating resinmay act as the saturant for the FRP composit
21、e as well as thebonding agent between the composite reinforcement and thesubstrate. Wet lay-up specimens may be fabricated in either afield or a laboratory setting.3.3 Symbols:3.3.1 F*strength of FRP laminate per unit width.3.3.2 h1laminate thickness measured outside of the over-lap splice on the bo
22、ttom (flat) laminate.3.3.3 h2laminate thickness measured outside of the over-lap splice on the top (kinked) laminate.3.3.4 h3laminate thickness measured within the overlapsplice region.3.3.5 hthe reference thickness of a fiber, fabric or pre-form layer without resin, measured outside of the overlaps
23、plice.3.3.6 Lentire length of the overlap splice specimen in-cluding the portion dedicated to gripping.3.3.7 Llength of the overlap splice region3.3.8 nnumber of specimens.3.3.9 Pforce carried by test specimen.3.3.10 Pmaxmaximum tensile force.3.3.11 wcoupon width.3.3.12 V*apparent shear strength of
24、the overlap splice perunit width for the L under consideration.4. Summary of Test Method4.1 Overlap splice specimens are prepared using a wetlay-up procedure. Wet lay-up material may be prepared in alaboratory or field setting, as the testing objectives dictate. Fortesting in single shear, two thin,
25、 flat strips of material having anominally constant cross section are joined together with aspecified overlap and allowed to cure. The cured specimen ismounted in the grips of a mechanical testing machine andmonotonically loaded in tension while force is recorded. Thefollowing items are reported for
26、 each specimen: ultimate forceat failure, failure mode, and the apparent shear strength per unitwidth at failure.5. Significance and Use5.1 Overlap splices are used in field applications of FRPcomposites when site conditions prohibit continuous access toa structural element or when the specified len
27、gth of the FRPcomposite is such that saturation and placement of the entirelength would be cumbersome. This method can be used as aquality control mechanism for ensuring that overlap splicesconstructed under field conditions meet or exceed the require-ments established by the design engineer or FRP
28、systemmanufacturer. Both the saturant mixing and fiber saturationmethod can be verified for wet-layup FRP systems.5.2 Caution is recommended when interpreting apparentshear strength results obtained from this method. Single shearlap splices develop non-uniform shear stress distributionswithin the ov
29、erlap splice region during testing. Additionalguidance on the interpretation and use of results obtained fromlap shear testing is found in D4896.5.3 This test method focuses on the FRP material itself,irrespective of gripping method. Therefore, strengths resultingfrom failure or pullout at either gr
30、ip are disregarded. Thestrength measurements are based solely on test specimens thatfail in the gage section (away from the grips) or at the splice.6. Interferences6.1 A summary of the interferences, specifically materialand specimen preparation, gripping, system alignment, andedge effects in cross-
31、ply laminates, are presented in D3039/D3039M.6.2 Additional interferences may arise from lack of controlin wet lay-up specimen preparation procedures outlined in8.3.1. Specimen variations in resin content, ply thickness, voidcontent and degree of cure may contribute to variability in testresults.6.3
32、 Construction of single lap-splice samples using wet-layFRP will result in kinked fibers for the top laminate (see Fig.1). The effects of this kink on lap shear results will beFIG. 1 Interference in Wet-Lay FRP Sample due to Kink in Top LaminateD7616/D7616M 112magnified as the thickness, h1and h2, o
33、f the FRP increases.This kink may also result in laminate failure outside the regionof the bondline and the severity of the kink can impart momentloading to the bonded joint.6.4 Overlap splice length, L, is identified in D4896, section5.3.2 as a geometric parameter which affects apparent shearstreng
34、th properties obtained from overlap splice tests. Theresults obtained using this test method are valid exclusively forthe overlap splice length under consideration.6.5 If a supplementary adhesive material (e.g., thickenedepoxy tack coat) is used to promote bond between compositelayers within the ove
35、rlap splice region, it should be noted thatvariations in the bond-line thickness may result in differentapparent shear strength values or different failure modes. Thetypically observed trend is that increasing bondline thicknessresults in decreased apparent shear strength (DOT/FAA/AR-01/33 and DOT/F
36、AA/AR-02/97).6.6 The fiber/ply orientation within the overlap splice regionhas also been shown to influence the apparent shear strength orfailure mode, or both, in lap shear specimens (DOT/FAA/AR-02/97).6.7 The temperature and moisture conditions experiencedby a specimen during curing and load testi
37、ng can affect theapparent shear strength of an overlap splice joint. Additionalguidance is provided in D3039/D3039M, section 11.4.7. Apparatus7.1 Requirements for testing machines and instrumentationare the same as those given in D3039/D3039M, Section 7.8. Sampling and Test Specimens8.1 SamplingTest
38、 at least five specimens per test condi-tion unless valid results can be gained through the use of fewerspecimens, such as in the case of a designed experiment. Forstatistically significant data, the procedures outlined in PracticeE122 shall be consulted. Report the method of sampling.NOTE 1If speci
39、mens are to undergo environmental conditioning toequilibrium, and are of such type or geometry that the weight change ofthe material cannot be properly measured by weighing the specimen itself(such as a tabbed mechanical coupon), then use another traveler coupon ofthe same nominal thickness and appr
40、opriate size (but without tabs) todetermine when equilibrium has been reached for the specimens beingconditioned.8.2 GeometryRecommended geometries for single shearspecimens are provided in Fig. 2.8.2.1 Splice LengthThe desired overlap splice length shallbe specified. A designed experiment may invol
41、ve the testing ofgroups of specimens with varying overlap splice lengths. SeeTable 1 for recommended overall specimen lengths for varyingoverlap splice lengths. Variation in the overlap splice length asmeasured along both edges of the specimen shall be no greaterthan 6 5%.8.2.2 Specimen WidthMinimum
42、 specimen width for uni-directional wet lay-up FRP specimens shall be 25 mm 1.0 in.Minimum width for cross-ply specimens shall be 38 mm 1.5in. for wet lay-up composites. Variation in specimen widthshall be no greater than 6 1%.8.3 Specimen Preparation:8.3.1 Wet Lay-up FRPMake field-prepared specimen
43、s in amanner similar to the actual field installation of the material. Apolymer release film, typically 600 3 600 mm 24 3 24 in. isplaced on a smooth, flat horizontal surface. The release filmshall be at least 0.076 mm 0.003 in. thick and made of apolymer that will not adhere to the resin used to im
44、pregnate thefibers. Usually, acetate and nylon are acceptable. Resin is firstapplied to the release film. The dimensions of each ply shouldbe no less than 150 3 300 mm 6 3 12 in. (or longer asrequired by the specimen size, see Fig. 2). In order to facilitatethe construction of the overlap splice joi
45、nt and to ensure thedesired overlap splice length, L8, is obtained, the width of thebottom laminate may be slightly larger (5 10 mm) than thewidth of the top laminate. Any excess material present in thebottom laminate shall be removed and discarded during thespecimen machining process described in 8
46、.3.4. The dry fibersare saturated or coated with the specified amount of resin andplaced on the release film. This can be done using a properlycalibrated saturator machine or using a manufacturer-specifiedfiber to resin weight ratio. The specified number of plies at thespecified angles (0 or 90) for
47、 the bottom laminate of the singlelap splice are sequentially impregnated with resin and stackedonto the release film using the specified amount of resin per plyper unit area as in the actual installation. Using the flat edge ofa small hand tool or a grooved roller, air bubbles are workedout of the
48、material. The bubbles shall be worked out in thedirection of the primary fibers to ensure that no damage iscaused to the fibers. At this point the specified number of pliesfor the top laminate of the lap splice are sequentially impreg-nated with resin and stacked onto a second piece of releasefilm.
49、If a supplementary adhesive material is specified, it shallbe applied uniformly to both saturated laminates in the regionFIG. 2 Dimensions for Single-Shear Wet Lay-Up FRP SpecimensD7616/D7616M 113of the overlap splice as in the actual installation. One of thesaturated laminates is then placed on top of the other overlap-ping the bottom portion by the specified overlap splice dis-tance, L8. If the release film on the top laminate does not extendpast the entire length of the bottom laminate, the release filmon the top laminate shall be remove
