1、Designation: D 3762 03Standard Test Method forAdhesive-Bonded Surface Durability of Aluminum (WedgeTest)1This standard is issued under the fixed designation D 3762; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last r
2、evision. 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 method2,3simulates in a qualitative manner theforces and effects on an adhesive bond joint at metal-adhesive/prim
3、er interface. It has proven to be highly reliable in deter-mining and predicting the environmental durability of adher-end surface preparations. The method has proven to becorrelatable with service performance in a manner that is muchmore reliable than conventional lap shear or peel tests (Note 2).N
4、OTE 1While this test method is intended for use in aluminum-to-aluminum applications it may be used for determining surface durabilityof other metals and plastics provided consideration is given to thicknessand rigidity of the adherends.NOTE 2This test method is not a quantitative fracture strength
5、testmethod. To measure fracture strength see Test Method D 3433.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is
6、 theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 907 Terminology of Adhesives4D 3433 Test Method for Fracture Strength in Cleavage
7、ofAdhesives in Bonded Metal Joints43. Terminology3.1 DefinitionsMany of the terms used in this test methodare defined in Terminology D 907.4. Summary of Test Method4.1 A wedge is forced into the bondline of a flat-bondedaluminum specimen, thereby creating a tensile stress in theregion of the resulti
8、ng crack tip. The stressed specimen isexposed to an aqueous environment, usually at an elevatedtemperature, or to an appropriate environment relative to theuse of the bonded structure. The resulting crack growth withtime and failure modes are then evaluated. Variations inadherend surface quality are
9、 easily observable when thespecimens are forcibly, if necessary, opened at the test conclu-sion.5. Significance and Use5.1 The test is primarily qualitative, but is very discriminat-ing in determining variations in adherend surface preparationparameters and adhesive environmental durability. The tes
10、t hasfound application in controlling surface preparation operationsand in screening surface preparations, primer and adhesivesystems for durability. In addition to determining crack growthrate and assigning a value to it, the adhesivejoint failure isevaluated and reported. For example, adhesion fai
11、lure; cohe-sion failure; or adherend failure are noted after opening up thespecimen at the conclusion of the test period.6. Apparatus6.1 Magnifier (preferably stereo binocular), 5 to 30-power.6.2 Marking Stylus, sharp-pointed, or triangular file.6.3 Wedges, aluminum or stainless steel.NOTE 3Wedges a
12、re preferably of the same composition as theadherends of the specimen being tested to reduce the possibility ofelectrolytic corrosion. Stainless steel wedges have been found to workwell with many adherends and are very durable and reuseable.6.4 Scale, small, graduated in millimetres or hundredths of
13、an inch.1This test method is under the jurisdiction of ASTM Committee D14 onAdhesives and is the direct responsibility of Subcommittee D14.80 on MetalBonding Adhesives.Current edition approved August 10, 2003. Published September 2003. Origi-nally approved in 1979. Last previous edition approved in
14、1998 as D 3762 98.2Marceau, J. A., Moji, Y., and McMillan, J. C., “A Wedge Test for EvaluatingAdhesive Bonded Surface Durability,” 21st SAMPE Symposium, Vol 21, April 68,1976.3Scardino, W. M., Marceau J. A., “Comparative Stressed Durability of AdhesiveBonded Aluminum Alloy Joints” Symposium on Durab
15、ility of Adhesive BondedStructures, U. S. Army Armament Research and Development Command, Dover, N.J. Oct, 2729, 1976.4Annual Book of ASTM Standards, Vol 15.06.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Test Specimen7.1 Use a
16、 minimum of five 25.4 by 203-mm (1 by 8-in.)specimens from a single assembly for each test (Fig. 1).7.2 It is desirable to prevent plastic deformation (yielding)of the test specimen adherends when inserting the wedge intothe bondline. However, some plastic deformation is permis-sible providing it is
17、 not excessive. (Fig. 2 illustrates data inwhich some plastic deformation of high-strength aluminumalloys occurred when the wedges was forced into the bond-line.)7.3 The adherend yield point and the toughness of theadhesive are the two most important factors in determining asatisfactory adherend thi
18、ckness. The configuration of Fig. 1 hasbeen satisfactory for high-strength aluminum alloys, for ex-ample, 2024T-3 and 7075-T6, when used with most tough,high-strength aerospace adhesives.7.4 A satisfactory adherend thickness for a specificadhesive-adherend system can be determined by trial and error
19、methods and can also be approximated.NOTE 4The minimum permissible thickness in a uniform symmetri-cal adherend may be computed from the following relationship:h 56TaBFty(1)where:h = thickness of metal normal to plane of bonding, mm (or in.),Fty= tensile yield point of metal (or the stress at propor
20、tional limit)MPa (or psi),T = 150 % of the maximum load to start the crack in the adhesivebond, N (or lbf),a = crack length at maximum load, mm (or in.), andB = bond width, mm (or in.).8. Conditioning8.1 Expose the specimens to any environment appropriateto the bonded structure being represented, fo
21、r example: humid-ity, heat, thermal shock, salt spray, etc. However, for mostapplications water is the most deleterious environment to thepolymer-adherend interface. A typical accelerated aging envi-ronment commonly used is 50C (122F) and condensinghumidity. This and other standard test environments
22、 are listedin Table 1 (Note 5). The time of exposure may be varied. If thejoint is affected by the chosen environment, significant crackgrowth normally occurs.NOTE 5For maximum acceleration of aging effect, the aerospaceindustry typically uses environment 8 for adhesive systems that cure at121C (250
23、F) with performance to about 80C (178F) and environment9 for adhesive systems that cure at 177C (350F) with performance toabout 150C (302F).9. Procedure9.1 Prepare the surfaces of a piece of 152 by 203 by 3.2-mm(6 by 8 by 0.125-in.) aluminum using a surface treatmentprocess appropriate for the test
24、requirements.9.2 Prime the faying surface of each panel, apply theadhesive, assemble the panels, and cure the adhesive asrequired by the appropriate specification. Insert a 50.8 by 152by 0.10 mm (2 by 6 by 0.004-mm.) separation film along oneof the 152-mm wide edges of the assembly as shown in Fig.
25、1to omit the adhesive from between the separation film and thealuminum surface.9.3 Cut the test assembly into five 1-in. wide test specimensas shown in Fig. 1. The surface finish of both cut edges is 3.175m (125 in.) or finer. No burrs or smearing of adherendmaterial onto the bondline is allowed. Do
26、 not overheat ordamage the bond when cutting or finishing.9.4 Mark all test specimens to identify them appropriatelywith respect to their processing in a manner such that testing ina high-humidity environment does not destroy the identifica-tion markings. Appropriately positioned identification mark
27、-ings can be made on the 152 by 152-mm (6 by 6-in.) panelsprior to surface preparation processing.9.5 Open the end of the test specimen that contains theseparation film, and insert the wedge. Position the wedge so theend and sides are approximately flush with the sides of thespecimen. (In any use of
28、 an auxiliary tool to open thespecimen, remove the separation film or insert the wedge, donot bend the specimen.)9.6 Using 5 to 30-power magnification and adequate illu-mination, locate the tip of the crack, ao, on the 3.175-m(125- in.) finish edge of each specimen. This is the point, ao,farthest fr
29、om the wedge where the specimen (the adhesive,primer, or adherends, on both) has separated. Mark the locationon both sides of the adherend edge, using a fine stylus or scribe.If the specimen is to be used in salt spray or other environmentexpected to be corrosive and likely to obliterate the mark, t
30、hendeepen the scribe mark with a triangular file.9.7 For additional accuracy, take and average readings onboth sides of the specimen. Expose the wedged specimens tothe environment as required by the appropriate specification,the environments suggested in 8.1, or the environment dictatedby actual exp
31、ected service conditions.9.8 Remove the specimens from the environment and within15 min mark the location of the tip of the crack, Da, in the samemanner as in 9.6.9.9 Measure the initial crack length aoand the crackextension, Da, of each specimen to the nearest 0.254 mm (0.01in.).9.10 At the conclus
32、ion of the test, forcibly open the speci-men and note the failure mode of the test section.10. Interpretation of Results10.1 Report the crack extension, Da, and the adhesivejointfailure.10.2 The initial crack length, ao, the crack extension, Da,and the adhesivejoint failure are all functions of the
33、adherend,surface treatment, and the adhesive/primer systems beingconsidered. Because of these variables, the acceptance criteriafor a bonded system of interest has to be established. Below isan example of an acceptance criterion for sodium dichromate-sulfuric acid-etched, aluminum adherends bonded w
34、ith 121C(250F) curing high-peel modified epoxy structural adhesives:Ten specimens, representing two individual bonded testassemblies, are tested. Typically good durability surface prepa-ration is evidenced by no individual specimen having a crackextension, Da, exceeding 19 mm (0.75 in.) with the ave
35、rage ofD3762032FIG. 1 Crack Extension Specimen ConfigurationD3762033all specimens not over 6.3 mm (0.25 in.), when placed in 50C(122F) condensing humidity for 1 h.11. Report11.1 Report the following:11.1.1 Complete identification of the adhesive and specimentested, including types, source, manufactu
36、rers code numbers,form, etc.11.1.2 Method of preparing test specimens, including mix-ing and dispensing of adhesive.11.1.3 Conditioning procedure.11.1.4 Testing conditions.11.1.5 Number of specimens tested.11.1.6 Report the original crack length, ao, and the crackextension, Da, at the end of various
37、 time intervals such as 1, 4,8, 24 h; 7, 30 days.11.1.7 Also report the adhesivejoint failure such as 100 %cohesive, 100 % primer to adherend, or 50 % adhesive toprimer, etc.12. Precision and Bias12.1 Precision and bias must be established for each systemsince initial crack length, ao, the crack ext
38、ension,D a, and theadhesivejoint failure are all functions of the adherends,surface treatment, the adhesive/primer, and the environmentused.12.2 Fig. 2 is a plot of data on one such system (see 10.2) atfive separate locations over a period of 1 year.13. Keywords13.1 adhesive; crack extension; durabi
39、lity; surface prepara-tion; wedgeNOTE 1Distribution of crack extension Da at five locations for one adherend, surface preparation, adhesive, primer system. (Adhesive is a 121C(250F) curing high-peel modified expoxy structural adhesive).FIG. 2 Distribution of Crack ExtensionTABLE 1 Standard Test Envi
40、ronmentsTestEnvironmentNumberTemperature,C (F)AMoisture Conditions % RelativeHumidityB1 23 (73.4) immersed in distilled or deionized water2 23 (73.4) 503 23 (73.4) 154 35 (95) 905 35 (95) 1006 50 (122) 907 50 (122) 1008 60 (140) 1009 71 (160) 10010 35 (95) 5 % salt fog11 ambient (outdoors) ambient (
41、outdoors)12 other (specify) other, including aqueous solutions ornonaqueous liquids (specify)AThe tolerance for test temperature shall be 6 1C or 1.8F for environments 1to 10.BThe moisture condition may be provided by controlling the relative humidity ofa box, room, or other chamber by any convenien
42、t means.D3762034ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of
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