1、Designation: D7966/D7966M 14Standard Test Method forResistance to Creep of Adhesives in Static Shear byCompression Loading (Wood-to-Wood)1This standard is issued under the fixed designation D7966/D7966M; the number immediately following the designation indicates theyear of original adoption or, in t
2、he 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 method covers the determination of creepproperties of structural adhesives
3、in wood-to-wood bondswhen a standardized specimen is subjected to shearing stressesat various levels of static load, constant temperature, andrelative humidity. Apparatus and procedures are provided forshear deformation (creep) of adhesive bonds under static load.This test method is used under the i
4、ndicated conditions toevaluate resistance to creep properties of a structural woodadhesive.1.2 The test method is used to evaluate creep performanceof adhesives suitable for the bonding of wood, includingtreated wood, into structural wood products for generalconstruction, marine use, or for other us
5、es where a high-strength general construction, creep-resistant, durable adhesivebond is required. Individual block shear specimens are pre-pared from adhesively bonded laminations, subjected to aconstant load under various combinations of temperature andrelative humidity, and the amount of creep mea
6、sured.1.3 Creep of structural wood adhesives as measured by thistest method may not be comparative to other ASTM methodsand is limited to the conditions of the test and procedurescontained herein.1.4 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. T
7、he 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.1.5 This standard does not purport to address all of thesafety concerns, if any, associated
8、 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 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D905 Test Method for Strength Properties of AdhesiveBonds in Sh
9、ear by Compression LoadingD907 Terminology of AdhesivesD1101 Test Methods for Integrity of Adhesive Joints inStructural Laminated Wood Products for Exterior UseD2395 Test Methods for Density and Specific Gravity (Rela-tive Density) of Wood and Wood-Based MaterialsD2559 Specification for Adhesives fo
10、r Bonded StructuralWood Products for Use Under Exterior Exposure Condi-tionsD4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Base MaterialsE4 Practices for Force Verification of Testing Machines2.2 Other Document:3CSA O112.9 Evaluation of Adhesives for Structural WoodProd
11、ucts (Exterior Exposure)2.3 ASTM Adjuncts:Compression-Shear Creep Test Apparatus43. Terminology3.1 Definitions: Many terms in this test method are definedin Terminology D907.3.1.1 laminated wood, nthe fabricated product resultingfrom the bonding of two or more laminations, with eachlamination made f
12、rom one or more pieces bonded eitherlengthwise, edgewise, or both, and all with the direction of thegrain essentially parallel, to form a larger piece such as astructural member.3.1.1.1 DiscussionLaminated wood as defined in D1101.3.1.2 stress, nthe force exerted per unit area at a pointwithin a pla
13、ne.3.2 Definitions of Terms Specific to This Standard:1This test method is under the jurisdiction of ASTM Committee D14 onAdhesives and is the direct responsibility of Subcommittee D14.30 on WoodAdhesives.Current edition approved Nov. 1, 2014. Published March 2015. DOI: 10.1520/D7966_D7966-14.2For r
14、eferenced 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 Document Summary page onthe ASTM website.3Available from APA The Engineered Wood Association, 7011 S.19th St
15、.,Tacoma, WA 98466-5333, www.apawood.org.4Available from ASTM International Headquarters. Order Adjunct No. ADJ-ADJD4680. Original adjunct produced in 1987.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.1 average creep of specime
16、n, ncalculated creep dis-placement in the bondline of a specimen as shown in Fig. 1(D1+D2)/2.3.2.2 maximum average creep, nthe largest average creepobserved with any one test specimen from a test assembly.3.2.3 overall average creep, nthe average creep observedin the test assembly based on the avera
17、ge creep of the testedspecimens.3.2.4 laminated test assembly, nan assembly formed bybonding layers of lumber with an adhesive so that the grain ofall laminations is essentially parallel.4. Summary of Test Method4.1 An adhesive to be evaluated for suitability in structuralwood products in terms of r
18、esistance to creep is used to prepareblock shear test specimens which will then be loaded to aprescribed level of stress.4.2 Following the adhesive manufacturers recommenda-tions two 2ply test assemblies of a designated species arelaminated following specific recommendations of wood selec-tion and p
19、reparation.4.3 After a designated curing period, eight 25 mm 1.0 in.by 25 mm 1.0 in. block shear specimens are prepared fromeach assembly and preconditioned.4.4 Both sides of the geometric center of each specimen aremarked with a scribe.4.5 The block shear specimens from each assembly areloaded to t
20、he required stress in a prescribed compression-shearcreep test jig and then subjected to a designated test environ-ment in terms of temperature, moisture level and time.4.6 At the completion of the designated exposure time, theamount of creep for each specimen is measured and reportedalong with the
21、average creep for the group of specimens.5. Significance and Use5.1 This test method evaluates the performance of theadhesive in laminated wood as measured by resistance to creepunder static load.5.2 Test results from the evaluation of adhesive creepresistance, under designated environmental conditi
22、ons of thetest, provide a measure of the adhesives ability to withstandconstant loading over a relatively long period of time.5.3 Creep measured with this test method is normally usedin conjunction with specifications such as, but not limited toSpecification D2559 and CSA O112.9 to confirm suitabili
23、ty ofan adhesive to resist creep under designed loads when sub-jected to specific levels of stress, load duration and environ-mental conditions.6. Apparatus6.1 Testing MachineA testing machine, or other suitableloading machine, capable of applying compression loads from0 to 22 kN (5000 lbf) having a
24、n accuracy of 61 % whencalibrated in accordance with Practice E4, and cross-headspeeds from 0.3 to 10 mm/min 0.01 to 0.40 in./min issufficient for this test method.Aminimum vertical space of 510mm 20 in. is required to compress the loading spring in thecreep-test apparatus.6.2 Creep-Test ApparatusSt
25、atic loads shall be applied andmaintained on block-shear specimens by means of thecompression-loaded creep-test cylinder shown in Fig. 2. Thespecific spring used in the apparatus shown in Fig. 2 has adesign load of 2300 lbf (10 kN) and is made of corrosion-resistant components so that is can be used
26、 in high-temperatureand humid environments for prolonged periods without con-cern for damaging the apparatus or interfering with theeffectiveness. The apparatus is spring-loaded and shall containa mechanism to provide a self aligning surface to account forspecimens where the two bearing surfaces are
27、 not perfectlyparallel.NOTE 1Although this particular spring has a design load of 10 kN(2300 lbf) others of greater or less capacity may be substituted. Varyingspring capacities with outside diameters no greater than the cylinder insidediameter are available. Additional details, including options fo
28、r providingself aligning surface can be found in ADJD4680.6.2.1 For creep testing up to 50C 122F, it is notnecessary to adjust the spring or load to compensate for theeffects of changing temperature. It is only necessary that theFIG. 1 Creep Measurement of Test SpecimenD7966/D7966M 142FIG.2CreepTest
29、ApparatusD7966/D7966M 143apparatus, with included specimen, be preconditioned to thetest temperature before the test load is applied to the spring.The preheated apparatus must be wrapped with a piece offlexible thermal insulation material while the test load isapplied to the specimen. After loading
30、and measurements,return the loaded apparatus to the test environment.NOTE 2Since there are no significant changes in temperature before orafter loading, no adjustments are needed in the spring.6.2.1.1 When conducting creep testing a temperatures of50C 122F or higher the applied stress level shall be
31、increased to compensate for the decrease in the spring constant.This can be determined by comparing the spring constant forthe spring at room temperature to that when the spring is heatedto the specified temperature. Laboratories shall establish thatthe spring constant, when repeatedly heated to the
32、 specifiedtemperature, is consistent between each use. Compensation forspring stiffness at temperature shall be determined by thetesting laboratory.6.3 MicroscopeA microscope with an objective lens of atleast 7 magnification or a magnifying glass, such as a 10loupe is required to measure displacemen
33、t of scribe marksacross the two adherends of a specimen to measure and recordany creep that has occurred. A linear traveling binocularmicroscope is ideally suited to creep measurements; however,a microscope fitted with an appropriately graduated scale issatisfactory.6.4 Environmental ChambersAn envi
34、ronmental chamberis required to precondition test specimens to their intended testenvironment and subject the conditioned specimens, afterloading to a specified shear stress, to the required conditions oftemperature and relative humidity. In the absence of specificrequired test conditions of tempera
35、ture, relative humidity,applied shear stress and time under test, Table 1 providesexamples of standard conditions that are considered appropri-ate.6.4.1 Conditioning equipment, such as but not limited toovens and humidity cabinets, should be capable of maintaininga constant temperature within 62.0C
36、63.6F of the set-point and constant relative humidity within 65 % of theset-point at a given temperature for each of the test conditionsselected for evaluation.NOTE 3The standard conditions listed in Table 1 are consideredappropriate to evaluate the suitability of a structural wood adhesive forcreep
37、 resistance when exposed to a variety of environmental exposureconditions up to and including continuous exposure to the weather. Otherconditions of temperature, humidity, load duration and stress level may beused or specified provided that the conditions and their precision has beendetermined and r
38、eported. Specific and appropriate product standards,qualified evaluation and code approval agencies, or combinations thereof,may specify the targeted stress level for a particular species or speciesgroup, including exposure duration, when adopting this test method.NOTE 4Section 8.6 provides requirem
39、ents for preconditioning speci-mens prior to testing.7. Materials7.1 Wood Selection, Preparation and ConditioningUseany softwood or hardwood single species planned for bondingand intended for use and considered suitable for bondedstructural wood products. The selected species shall be com-patible wi
40、th the test structural wood adhesive and determinedsuitable to evaluate resistance to creep using this test method asrequired, specified or desired. Bond only to vertical grain woodsurfaces (Note 6).NOTE 5This test only measures resistance to creep; for characterizingadditional adhesive properties r
41、elated to the selected species, such asbondability, an alternative test method or specification, including but notlimited to Specification D2559 should be considered.NOTE 6The bond face is considered vertical grain when the growthrings make an angle of between 45 and 90 to the face.7.1.1 For the spe
42、cies under evaluation, each piece of woodselected for use in resistance to creep testing and in accordancewith this test method shall have a minimum specific gravity asindicated in Table 1, Required Shear Strength for StructuralLaminated Wood Products, in Specification D2559. For speciesnot included
43、 in Table 1 of Specification D2559 consult theUSDA Wood Handbook5for the reported specific gravity at12 % moisture content (Note 7).NOTE 7For the species selected for evaluation, the wood qualityselected is such that it is able to sustain the applied stress under theselected environmental conditions
44、. For species not found in Table 1 ofSpecification D2559, trial tests should be conducted to confirm the woodhas adequate strength for the specific test. Wood with higher specificgravity and slower growth rate (relatively large number of growth ringsper inch) have been found to be effective metrics
45、for selecting suitablewood substrate for resistance to creep testing.7.1.2 The wood shall have a slope of grain not steeper than1 in 15 on any face or any edge. The wood shall contain noknots larger than 3 mm 18 in. in diameter and shall be free ofdecay, machining defects (such as chipped grain, dub
46、bed ends,feed roll polish, coarse knife marks, and feed rollcompression), and any drying defects such as case hardening,collapse, splits, or checks.7.1.3 Condition the wood at 23 6 2C 73 6 3.6F and arelative humidity of 50 to 70 % (preferably 65 %) until amoisture content of 8 to 14 % has been obtai
47、ned.7.1.3.1 Conditioning for wood used for sample preparationby hot press adhesives that require a moisture content less than8 %, should be in accordance with the adhesive manufacturersrecommendations.5Available from USDA, Forest Products Laboratory, One Gifford Pinchot Drive,Madison, WI 53726, http
48、:/www.fpl.fs.fed.us.TABLE 1 Standard Environmental ConditionsTest Condition TemperatureRelative Humidity(%)Time (days) Stress LevelAA20 2.0C 68 3.6F 95 7 2.5 MPa (360 psi)BA70 2.0C 158 3.6F ambient humidity 7 2.5 MPa (360 psi)CA50 2.0C 122 3.6F 100 28 2.1 MPa (300 psi)AConditions for A, B, and C are
49、 the same as those found in CSA O112.910.D7966/D7966M 1448. Test Specimens8.1 The standard specimen shall be the block-shear speci-men illustrated in Fig. 3.8.2 The test adhesive is used to bond the selected woodspecies together following procedures found in 8.4. The sheararea of the standard specimen shall be 25 by 25 mm 1.0 by 1.0in. equaling 625 mm21.0 in2.8.3 Preparation of Test Assemblies:8.3.1 Prepare two laminated test assemblies, each providingeight test specimens.8.3.2 Billets 16 mm 0.
