1、Designation: D5656 10Standard Test Method forThick-Adherend Metal Lap-Shear Joints for Determination ofthe Stress-Strain Behavior of Adhesives in Shear byTension Loading1This standard is issued under the fixed designation D5656; the number immediately following the designation indicates the year ofo
2、riginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the preparation and testing ofthick-
3、adherend lap-shear samples for the determination of thestress-strain behavior of adhesives.1.2 This test method covers data reduction and analysis ofstress-strain curves obtained using thick-adherend lap-shearsamples.1.3 The values stated in SI units are to be regarded as thestandard. The inch-pound
4、 units in parentheses are for informa-tion only.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 determine the applica-bility of reg
5、ulatory limitations prior to use. Specific precau-tionary statements are given in 7.3.2. Referenced Documents2.1 ASTM Standards:2D907 Terminology of AdhesivesD2651 Guide for Preparation of Metal Surfaces for Adhe-sive BondingD4896 Guide for Use ofAdhesive-Bonded Single Lap-JointSpecimen Test Results
6、E4 Practices for Force Verification of Testing Machines3. Terminology3.1 Definitions:3.1.1 Many terms in this test method are defined in Termi-nology D907.3.2 Definitions of Terms Specific to This Standard:3.2.1 knee, ninflection point on a load-deflection curve;the point at which plastic yielding o
7、f the adhesive begins todominate the deformation response of the load-deflectioncurve.3.2.2 panel, ntwo plates of a rigid material having thesame dimensions that are adhesively bonded together on oneface such that the thickness of the panel is approximately twicethe thickness of each individual plat
8、e.4. Summary of Test Method4.1 This test method consists of testing thick-adherendlap-shear samples whereby a tensile load is applied to thesample but the adhesive is placed in shear. Unlike GuideD4896, the adherends used in this standard test method arethick and rigid, peel forces are minimized and
9、 the shearstress-strain properties of the adhesive are obtained. Refer-enced data presents a finite element analysis of the thick-adherent metal lap shear specimen and calculates the effect ofvarying the adherent and adhesive stiffness.3User of thisstandard is cautioned that since the stress is not
10、totally uniformacross the over-lap of the specimen, factors such as adhesivestiffness, adherent stiffness and location of shear strain mea-surement along the length of the bond can affect the experi-mentally obtained load-displacement curve.3,4NOTE 1The peel forces generated during testing are a fun
11、ction of thebending deformation in the adherends. Greater adherend stiffness resultsin less bending and smaller peel forces.5. Significance and Use5.1 This test method can be used to determine the stress-strain properties of an adhesive in shear and to establish theproportional-limit of the stress-s
12、tain relationship. This datamay be useful for the design and analysis of adhesively bondedjoints.1This test method is under the jurisdiction of ASTM Committee D14 onAdhesives and is the direct responsibility of Subcommittee D14.80 on MetalBonding AdhesivesCurrent edition approved Oct. 1, 2010. Publi
13、shed October 2010. Originallyapproved in 1995. Last previous edition approved in 2004 as D5656 - 041. DOI:10.1520/D5656-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, re
14、fer to the standards Document Summary page onthe ASTM website.3Kassapoglou, C. and Adelmann, John C., “KGR-1 Thick Adherend SpecimenEvaluation for the Determination of Adhesive Mechanical Properties,” 23rdInter-national SAMPE Conference, Oct. 2124, 1991.4Krieger, R. B., Jr., “Stiffness Characteristi
15、cs of Structural Adhesives for StressAnalysis in Hostile Environment,” American Cyanamid Co., Havre de Grace, MD,1975.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 This test method is not intended to determine adhesioncharacter
16、istics of an adhesive to a particular substrate; ratherthis test method is intended to characterize the adhesive shearstress-strain properties that may be relevant for design consid-erations.5.3 This test method has been developed and applied usingbonded aluminum adherends. At this time no assumptio
17、nsregarding the validity of this test method with non-aluminumadherends can be made.6. Apparatus6.1 Testing machine conforming to the requirements ofPractices E4. Select the testing machine so that the breakingload of the specimens falls between 15 and 85 % of thefull-scale capacity. Ensure that the
18、 machine is capable ofmaintaining a rate of loading of 2455 N (550 lbf)/min, or, if therate is dependent on cross-head motion, set the machine toapproach this rate of loading. Use a suitable pair of self-aligning grips to hold the specimen. Ensure that the grips andattachments are so constructed tha
19、t they will move intoalignment with the test specimen as soon as the load is applied,so that the long axis of the test specimen will coincide with thedirection of the applied pull through the center line of the gripassembly.NOTE 2The cross-head speed setting required to approach the speci-fied loadi
20、ng rate is dependent on the modulus of the adherends and theadhesive being evaluated.6.2 Use two three-point displacement sensors, linear vari-able differential transformers (extensometers), with the capa-bility of measuring displacements in the adhesive bond overlaparea and a sensitivity sufficient
21、 to measure displacements withan accuracy of 1 part/1000.7. Sample Preparation7.1 Suitably prepare the bonding surfaces of two 229 by229-mm (9 by 9-in.) by 9.5 6 0.05-mm (0.375 6 0.002-in.)rigid adherends, such as 2024-T3 aluminum, for the adhesivebeing used. For aluminum, solvent degreasing and aci
22、d etch-ing, such as Method G of Guide D2651, are recommended forremoving the oxide coating from the aluminum surfaces to bebonded.7.2 Apply the adhesive in a uniform layer to one face of oneof the adherend plates. In the case of paste adhesives andunsupported film adhesives, metal wires or shims may
23、 be usedto control the bondline thickness. In this case, take care toensure that the shims are outside of the lap area or are locatedin the trim region around the panel perimeter so that they donot affect the test results. Place the other adherend plate on topof the adhesive-coated plate in accordan
24、ce with Fig. 1.Toachieve the desired adhesive thickness, apply sufficient pres-sure to cause the adhesive to flow between the plates such thatthe plates are in contact with the shims if they are being used.Cure the adhesive in accordance with the manufacturersrecommended practices for the adhesive b
25、eing tested.NOTE 3The use of glass beads in the adhesive to control the bondlinethickness is not recommended, since their use will have an effect on thecalculated values of modulus, strain, and strength.7.3 After cure, saw-cut 25.4-mm (1.0-in.) wide test samplesfrom the bonded panel, or if machined
26、edges are preferredsaw-cut the samples to 27.5-mm widths and machine the sawcut edges to a sample width of 25.4 mm (1.0 in.). Use an endmill to machine notches through the glue line in accordancewith Fig. 2. Drill holes for inserting support pins and steelbushings for testing in accordance with Fig.
27、 2.(WarningExercise caution during machining of the notches to minimizethe buildup of stresses and thermal degradation of the adhesivein this region.) End milling or saw cutting has been found tocarry metal from the metal plates and decrease the adhesivebondline thickness in a narrow region along th
28、e cut edge. Handsanding using progressively finer grit sandpaper on a flatsanding block has been found to eliminate this edge effect. Theuse of 240, 320, 400 followed by 600 grit sandpaper to sand thecut edges, which determine the specimen width, has beeneffective in removing the metal spread into t
29、he adhesivebondline edge.7.4 Using a vernier caliper or other suitable measuringdevice, measure the width of the overlap area to the nearest0.03 mm (0.001 in.) for each test sample.7.5 Using an optical comparator or other suitable measuringdevice, measure the overlap length to the nearest 0.03 mm(0.
30、001 in.) for each test sample.7.6 Using an optical comparator or other suitable measuringdevice, measure the adhesive thickness in the overlap region tothe nearest 0.003 mm (0.0001 in.) for each test sample. Due tometal surface roughness start and end the measurement of bondthickness at the average
31、of metal peak to valley distance.8. Calibration of Extensometers8.1 Connect the extensometers to an amplifier with twosignal inputs and one signal output, which is the average of thetwo input signals. Connect the amplifier output to a strip-chartrecorder that will be used during testing. Allow suffi
32、cient timefor the amplifier to warm up to minimize signal drift.FIG. 1 Bonded Adherend PlatesD5656 1028.2 Using a micrometer gage or similar device, adjust theamplifier gain such that 0.0254 mm (0.001 in.) of extensometerdisplacement is equal to 50.8 mm (2.0 in.) of chart travel.8.3 Repeat the proce
33、dure for the remaining extensometer.9. Conditioning9.1 The accuracy of the results of strength tests of adhesivebonds depends on the conditions under which the bondingprocess is carried out. Unless otherwise agreed upon betweenthe manufacturer and the purchaser, use the bonding conditionsprescribed
34、by the manufacturer of the adhesive. In order toensure that complete information is available to the individualconducting the tests, obtain numerical values and other specificinformation from the manufacturer of the adhesive for each ofthe following variables:9.2 Procedure for preparation of surface
35、s prior to applica-tion of the adhesive, the cleaning and drying of adherendsurfaces, and special surface treatments, such as sanding, thatare not specifically limited by the pertinent test method,9.2.1 Complete mixing directions for the adhesive,9.2.2 Conditions for application of the adhesive, inc
36、ludingthe rate of spread or thickness of film, number of coats to beapplied, whether to be applied to one or both surfaces, and theconditions of drying where more than one coat is required,9.2.3 Assembly conditions before application of pressure,including the room temperature, relative humidity, and
37、 lengthof time,9.2.4 Curing conditions, including the amount of pressure tobe applied, the length of time under pressure, method ofapplying pressure (pressure bag, press platens, etc.), heat-uprate, and the temperature of the assembly when under pressure.Ensure that it is stated whether this tempera
38、ture is that of thebondline or of the atmosphere at which the assembly is to bemaintained,NOTE 1Asymmetry obviates “left-right” covention. Ship terms retain identity of test site when specimen is rotated or inverted.FIG. 2 Thick Adherend Lap Shear Test SpecimenD5656 1039.2.5 Conditioning procedure b
39、efore testing, unless a stan-dard procedure is specified, including the length of time,temperature, and relative humidity.9.3 A range may be prescribed for any variable by themanufacturer of the adhesive if it can be assumed by the testoperator that any arbitrarily chosen value within such a rangeor
40、 any combination of such values for several variables will beacceptable to both the manufacturer and the purchaser of theadhesive.10. Procedure10.1 Connect two extensometers to the signal amplifier andthe averaged signal output from the amplifier to the strip-chartrecorder. Allow sufficient time for
41、 the amplifier to warm up tominimize signal drift.10.2 Set the chart range such that the expected outputsignals during testing from the extensometer is between 15 and85 % of full scale.10.3 Using a solid bar of adherend material machined to thesame overall dimensions and geometry as the test sample,
42、attach one of the extensometers to each edge of the bar, inaccordance with Fig. 3.10.4 Mount the bar in the test machine by placing a steelbushing though each of the drilled holes of the solid bar andinserting steel pins through the bushings and clevises attachedto the test machine. Adjust the cross
43、-head position of the testmachine to zero, the initial load on the specimen. Load the barto 4017 N (900 lbf) at a rate of 2455 N/min (550 lbf/min).Repeat the loading six times and record the load versusdisplacement for each loading.10.5 For each of the six loadings extrapolate the load-displacement
44、curve to 4464 N (1000 lbf) and record thedisplacement at this load. Average the results of the six tests toobtain the metal load-displacement values. For 2024-T3 alu-minum, 0.00057 mm/1000 N (0.00010 in./1000 lbf) has beenfound to be a reasonable value for metal deformation at 22C(72F).10.6 Using an
45、 adhesively bonded test sample, mount theextensometers on each edge of the sample such that theadhesive bondline is centered between the contact points ofeach extensometer and each extensometer is centered betweenthe machined notches in the test specimen, in accordance withFig. 4. Ensure that the si
46、ngle point on the extensometer is onthe leg of the coupon that will be raised during testing.10.7 Mount the test specimen in the test machine by placinga steel bushing through each of the drilled holes of the testsample and inserting steel pins through each bushing and clevisattached to the test mac
47、hine. Adjust the cross-head position ofthe test machine to zero, the initial load on the specimen. Loadthe test sample to failure at a rate of 2455 N/min (550 lbf/min).10.8 Test a minimum of three replicate samples.11. Calculation (See Fig. 5)11.1 Draw a tangent line to the initial, linearly rising
48、portionof the load-displacement curve and label the line as “A.” Labelthe point at which the load-displacement curve diverges fromthe tangent as “LL” (linear limit). The calculated stress andstrain at LL are dLLand gLL, respectively (refer to 11.8 and11.9).11.2 Draw a tangent line to the horizontal
49、or yielded portionof the load-displacement curve and label the line as “B.”11.3 Draw a line through the load-displacement curve,which bisects the angle between the two tangents and label thisline “C.” Label the point on load displacement curve as “KN”FIG. 3 Extensometer Positioning for Metal Deformation DeterminationD5656 104(knee). If digital data is utilized (see Fig. 6) do not use thecalculated slope of the two tangent lines “A” and “B” todetermine the bisector of line “D,” instead use an equal chartdistance from the intersection point “e” to define points “f” and“g
