1、Designation: D 3931 08Standard Test Method forDetermining Strength of Gap-Filling Adhesive Bonds inShear by Compression Loading1This standard is issued under the fixed designation D 3931; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of compara-tive shear properties of gap-filling adhesives
3、in wood-to-woodjoints at specified thicknesses of bondline in the dry condition,when tested on standard specimens under specified conditionsof preparation, conditioning, and loading in compression. Thistest method is intended as an evaluation of gap-filling adhe-sives such as those used to bond plyw
4、ood to lumber, lumber tolumber, and other similar materials in building constructions.1.2 This test method also may be used to determine shearproperties of gap-filling adhesives in species of wood and inthicknesses of bondline other than those specified for thecomparative tests of shear properties w
5、ithin this test method.All procedures specified herein are applicable, excepting re-quirements for wood species and specific gravity, and thick-nesses of bondlines.1.3 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to
6、SI units that are provided for information onlyand are not considered standard.1.4 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 dete
7、rmine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 143 Test Methods for Small Clear Specimens of TimberD 905 Test Method for Strength Properties of AdhesiveBonds in Shear by Compression LoadingD 1151 Practice for Effect of Moisture and Temper
8、ature onAdhesive BondsE 171 Specification for Atmospheres for Conditioning andTesting Flexible Barrier Materials3. Terminology3.1 Definitions:3.1.1 gap-filling adhesive, nan adhesive capable of form-ing and maintaining a bond between surfaces that are notclose-fitting.3.1.1.1 DiscussionClose-fitting
9、 is relative to a given ma-terial and industry; for example, standards in constructiondiffer from standards in electronics. Some adhesives will bondby bridging without completely filling the gap; others by fillingthe gap completely.4. Significance and Use4.1 Structural design based on strength-of-ma
10、terials prin-ciples requires knowledge of the mechanical properties of thestructural components, including adhesives. By nature of theiruse, the most important property of adhesive is shear strength.4.2 Shear strength measured by this test method is suitablefor use in adhesive development, manufactu
11、ring quality con-trol, and in materials performance specifications, as well asstructural design.5. Apparatus5.1 Testing Machine, having a capacity of about 15 000 lb(6818 kg) in compression or of sufficient capacity to test theadhesive in use. The machine shall be fitted with a shearingtool containi
12、ng a self-aligning seat to ensure uniform lateraldistribution of the load. The machine shall be capable ofmaintaining a uniform rate of loading such that the load may beapplied with a continuous motion of the movable head tomaximum load at a rate of 9.20 in. (5.0 mm)/min with apermissible variation
13、of 625 %. The shearing tool shown inFig. 1 of Test Method D 905 has been found satisfactory.1This test method is under the jurisdiction of ASTM Committee D14 onAdhesives and is the direct responsibility of Subcommittee D14.70 on ConstructionAdhesives.Current edition approved April 1, 2008. Published
14、 May 2008. Originallyapproved in 1980. Last previous edition approved in 2005 as D 3931 - 93a (2005).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards D
15、ocument Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Locate the testing machine in an atmosphere such that themoisture content of the specimens, developed under the con-ditions prescribed in 7.3, is
16、 not noticeably altered duringtesting.6. Test Specimen and Sample6.1 Test specimens for adhesive bonds shall conform to theform and dimensions shown in Fig. 1. Prepare bonded assem-blies as described in 7.1. Prepare test specimens for testing asdescribed in 7.2.6.2 Determine mean shear strengths of
17、bonds at bondlinethicknesses of 0.006 and 0.060 in. (0.15 and 1.52 mm). Testsfor strengths of bonds at other thicknesses, in addition to thosespecified, shall be optional upon agreement between themanufacturer and the user.6.3 Test a minimum of 28 specimens, representing sevendifferent bonded assemb
18、lies, to determine mean shear strengthsof bonds at each bondline thickness.7. Procedure7.1 Preparation of Bonded Assemblies:7.1.1 Prepare bonded assemblies with hard maple blocks(Acer saccharum or Acer nigrum) conditioned as described in7.3. The blocks shall have a minimum specific gravity of 0.65,b
19、ased on ovendry weight and ovendry volume (Note 1).NOTE 1A method for selecting maple blocks of satisfactory specificgravity is described in the Appendix of Test Method D 905. For referencetests, the specific gravity of blocks may be determined in accordance withthe Weight and Moisture Content Secti
20、on under Nail Withdrawal of TestMethods D 143.7.1.1.1 These blocks shall be straight-grained and free ofdefects, including knots, splits, birdseye, short grain, decay,and any unusual discoloration within the shearing area. Theblocks shall be of suitable size so that four test specimens canbe cut fro
21、m one test joint, as shown in Fig. 2. Blocksapproximately34 by 212 by 14 in. (19 by 63 by 356 mm) havebeen found to be satisfactory for this purpose. The moisturecontent shall be from 8 to 10 % (conditions prescribed in 7.3.1)based on ovendry weight as determined on representativesamples in accordan
22、ce with the final measurement sectionunder radial and tangential shrinkage and the weighing sectionunder moisture determination in Test Methods D 143. Surfacethe blocks just prior to gluing, preferably with a hand-feedjointer. Make sure the surfaces remain unsanded and free fromdirt.7.1.2 Use spacer
23、 strips to control bondlines to specifiedthicknesses between blocks. Spacers shall be wood veneer orplastic, and measure approximately12 by 312 in. (13 by 89mm) long. Place spacers crosswise at the ends and center of thelower test joint block. Apply adhesive in sufficient quantity toensure squeezeou
24、t at the ends of the joint when blocks areunder pressure (Note 2).NOTE 2If the adhesive is to be applied as an extruded bead, the beadshould be38 to12 in. (10 to 13 mm) in diameter to ensure squeezeout inbondline thicknesses near 0.060 in. (1.5 mm). Use a smaller diameter beadof adhesive for thinner
25、 bondlines.7.1.2.1 Take care to avoid air entrapment in the bondline.Do not spread the adhesive closer than12 in. (13 mm) to anyspacer because adhesive may be entrapped between block andspacer, thereby increasing bondline thickness. Assemble theblocks immediately, unless specified otherwise by agree
26、mentbetween the manufacturer and user of the adhesive. Apply a15-lb (7.0-kg) load uniformly over the entire bond area toensure firm contact between spacers and blocks of the assem-bly. Maintain the pressure on test joints at the conditionsprescribed in 7.1.7.1.3 Curing time for bonded assemblies sha
27、ll be as speci-fied by the manufacturer of the adhesive, or else 30 days in thestandard atmosphere (7.3.1).7.2 Preparation of Test Specimens:TABLE 1Metric Equivalentsin.mm0.0641.63146.353419.0513444.45250.80FIG. 1 Form and Dimensions of Test SpecimenD39310827.2.1 Joint one edge of each bonded assemb
28、ly to use as areference surface in further cutting. Rip-saw the other edge toreduce the width of the assembly to 2 in. (51 mm). Cut 2-in.long specimen blanks with the reference surface of the bondedassembly against the crosscut guide of the saw (Cut A, Fig. 2).Then using a stop clamped to the crossc
29、ut guide, notch eachend of the specimen blank to achieve the 134-in. (44.5-mm)bond length (Cuts B1 and B2, Fig. 2). Always make the cutwith the reference surface against the crosscut guide. Make CutB1 extend through the laminate to the glueline. Make Cut B2extend through the laminate and through the
30、 glueline. Thepurpose of the latter procedure is to ensure that the adhesive-adhered bond under test is aligned with the shear plane. Makethe final cuts (Cut C, Fig. 2) with the block vertical in order toremove waste and complete the steps on either end of thespecimen. Keep the reference surface aga
31、inst the crosscutguide. Take special care in making all of the above cuts toensure that the loading surfaces are smooth, parallel to eachother, and perpendicular to the edges and the bondline.7.2.2 Measure and record the bond width and length to thenearest 0.010 in. (0.25 mm).7.3 Conditioning:7.3.1
32、Use the standard atmosphere for adhesives for condi-tioning wood blocks prior to bonding, curing of test joints, andstoring of test joints and specimens prior to testing, unlessotherwise specified. The standard atmosphere (SpecificationE 171) is a relative humidity of 50 6 5 % and a temperature of73
33、.4 6 3.6F (23 6 2C). Store wood blocks, test joints, andspecimens at these conditions for a period of 7 days, or untilthey reach equilibrium moisture content as indicated by noprogressive changes in weight.7.3.2 Other conditions such as described in Practice D 1151in materials performance specificat
34、ions, or by mutual agree-ment between the parties of the test, may be used in addition tothe standard atmosphere.7.4 TestingPlace the test specimen in the shearing tool sothat the load may be applied as described in 5.1. The positionof the specimen with respect to the loading ledge and self-adjustin
35、g bearing is shown in Fig. 3. Take special care toensure that the maple block rests on the lower ledge bearingand abuts the gap-filling bondline. The upper self-adjustingbearing should rest on the opposite maple block and gap-fillingbondline. Apply the loading with a continuous motion of themovable
36、crosshead at a rate of 0.20 in./min (5.0 mm/min) tofailure as described in 5.1.8. Calculation8.1 Calculate the nominal shear stress at failure in pounds-force per square inch (or pascals), and estimate the percentageof wood failure based on the measured bondline area betweenthe two laminations. Reco
37、rd for each specimen.TABLE 2Metric Equivalentsin.mm11238.1250.821263.514356.0FIG. 2 Bonded Assembly Showing Method of Cutting Four Test Specimen BlanksFIG. 3 Side View of Test Specimen Showing Method of NotchingSpecimen to Ensure Proper Alignment of Shearing Tool andPlane of ShearD39310838.2 Calcula
38、te the mean of the specimens of each grouptested as:xi5 (xi/n (1)where:xi= mean shear strength,xi= individual shear strengths of specimens in a group, andn = number of specimens in the group.8.3 Calculate the standard deviation of the group as:s 5 =( xi22 ( xi!2/n/n 2 1! (2)8.4 Calculate the standar
39、d error of the mean as:sx5 =s2/n (3)8.5 Calculate the mean percentage of wood failure, asshown in 8.2.9. Report9.1 Report the following information:9.1.1 Complete identification of the adhesive tested, includ-ing type, source, manufacturers code numbers, form, etc.9.1.2 Type of adherends in test spe
40、cimens; that is, species,specific gravity, and grain orientation (that is, edge or flatgrain).9.1.3 Bondline thicknesses tested, as determined from thick-nesses of spacers used rather than measured thickness of curedbondline.9.1.4 Moisture content of wood at time of bonding, methodof adhesive applic
41、ation, and time of cure.9.1.5 Temperature and relative humidity used for precondi-tioning wood blocks, curing of adhesive, and testing ofspecimens.9.1.6 Number of specimens tested at each bondline thick-ness.9.1.7 Number of test joints represented at each bondlinethickness.9.1.8 The mean, maximum, a
42、nd minimum shear stresses atfailure, and mean percentage of wood failure for each bondlinethickness. Also report the standard deviation of test values forshear stress at failure. Individual test values may be included inthe report at the option of either manufacturer or user.10. Precision and Bias31
43、0.1 Precision:10.1.1 The precision of this test method is based on aninterlaboratory study of Test Method D 3931 - 93a (2005),using a 0.006-in. gap, conducted in 2006. Each of sevenlaboratories tested five replicates of specimens prepared usingthree different adhesives, recording shear strength (lbf
44、).Table 1 summarizes the precision statistics for the statisticalanalysis on the data collected.10.1.2 The precision statement was determined throughstatistical examination of results from seven laboratories, onthree materials. These three adhesives were the following:(1) one-component polyurethane(
45、2) latex based low-VOC(3) poly-vinyl acetate10.1.3 The shear strength precision statistics are expressedin terms of within a laboratory (repeatability) and between-laboratories (reproducibility). Standard deviation (sr and SR)and 95 % repeatability and reproducibility limits (r and R)were selected a
46、s the precision statistics. See Table 1. Corre-sponding wood failure mean and standard deviation values aredisplayed. See Table 2.10.1.4 Qualification testing for Test Method D 3931 com-pliance specifies testing a sample set of 28 replicates. The shearstrength variability of a sample group larger th
47、an 5 replicateswould represent the adhesive performance estimate with ahigher degree of probability.10.1.4.1 Committee D14 will plan for a future interlabora-tory study of Test Method D 3931 with the standards recom-mended test set of 28 replicates.10.1.4.2 All of the test specimens were assembled a
48、ndprecut to shear blocks by an accredited laboratory professionaltechnician. The adhesives samples used for test specimenpreparation adhesive were from the same batch. The shearblocks were prepared on the same day with the same equip-ment. Variability contributors such as substrate moisture con-tent
49、, adhesive application rate, assembly time, press pressure,and curing conditions met the standards tolerance.3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D14-1013.TABLE 1 Summary of Shear Strength (lbf)Material, AdhesiveAverage D( x )RepeatabilityStandardDeviation(Sr)ReproducibilityStandardDeviation(SR)RepeatabilityLimit(r)ReproducibilityLimit(R)Maple to Maple,Adhesive D1122 103 132 288 368Maple to Maple,Adhesive E2850 380 496 1065 1390Maple to Maple,Adhesive F11010 1102 1312 3086
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