1、Designation: D7966/D7966M 14D7966/D7966M 16Standard 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 ad
2、option 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 method covers the determination of creep properties of struc
3、tural adhesives in wood-to-wood bonds when astandardized specimen is subjected to shearing stresses at various levels of static load, constant temperature, and relative humidity.Apparatus and procedures are provided for shear deformation (creep) of adhesive bonds under static load. This test method
4、is usedunder the indicated conditions to evaluate resistance to creep properties of a structural wood adhesive.1.2 The test method is used to evaluate creep performance of adhesives suitable for the bonding of wood, including treatedwood, into structural wood products for general construction, marin
5、e use, or for other uses where a high-strength generalconstruction, creep-resistant, durable adhesive bond is required. Individual block shear specimens are prepared from adhesivelybonded laminations, subjected to a constant load under various combinations of temperature and relative humidity, and t
6、he amountof creep measured.1.3 Creep of structural wood adhesives as measured by this test method may not be comparative to other ASTM methods andis limited to the conditions of the test and procedures contained herein.1.4 The values stated in either SI units or inch-pound units are to be regarded s
7、eparately as standard. The values stated in eachsystem may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from thetwo systems may result in non-conformance with the standard.1.5 This standard does not purport to address all of the safety c
8、oncerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D905 Test Method for Strength Propertie
9、s of Adhesive Bonds in Shear by Compression LoadingD907 Terminology of AdhesivesD1101 Test Methods for Integrity of Adhesive Joints in Structural Laminated Wood Products for Exterior UseD2395 Test Methods for Density and Specific Gravity (Relative Density) of Wood and Wood-Based MaterialsD2559 Speci
10、fication for Adhesives for Bonded Structural Wood Products for Use Under Exterior Exposure ConditionsD4442 Test Methods for Direct Moisture Content Measurement of Wood and Wood-Based MaterialsE4 Practices for Force Verification of Testing Machines2.2 Other Document:3CSA O112.9 Evaluation of Adhesive
11、s for Structural Wood Products (Exterior Exposure)2.3 ASTM Adjuncts:Compression-Shear Creep Test Apparatus43. Terminology3.1 Definitions: Many terms in this test method are defined in Terminology D907.1 This test method is under the jurisdiction of ASTM Committee D14 on Adhesives and is the direct r
12、esponsibility of Subcommittee D14.30 on Wood Adhesives.Current edition approved Nov. 1, 2014May 1, 2016. Published March 2015June 2016. Originally approved in 2014. Last previous edition approved in 2014 asD7966/D7966M 14. DOI: 10.1520/D7966_D7966-14.10.1520/D7966_D7966-16.2 For referencedASTM stand
13、ards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from APA The Engineered Wood Association, 7011 S.19th St., Tacoma, WA 98466
14、-5333, www.apawood.org.4 Available from ASTM International Headquarters. Order Adjunct No. ADJADJD4680. Original adjunct produced in 1987.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous ve
15、rsion. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM Internati
16、onal, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.1 laminated wood, nthe fabricated product resulting from the bonding of two or more laminations, with each laminationmade from one or more pieces bonded either lengthwise, edgewise, or both, and all with th
17、e direction of the grain essentiallyparallel, to form a larger piece such as a structural member.3.1.1.1 DiscussionLaminated wood as defined in D1101.3.1.2 stress, nthe force exerted per unit area at a point within a plane.3.2 Definitions of Terms Specific to This Standard:3.2.1 average creep of spe
18、cimen, ncalculated creep displacement in the bondline of a specimen as shown in Fig. 1(D1+D2)/2.3.2.2 maximum average creep, nthe largest average creep observed with any one test specimen from a test assembly.3.2.3 overall average creep, nthe average creep observed in the test assembly based on the
19、average creep of the testedspecimens.3.2.4 laminated test assembly, nan assembly formed by bonding layers of lumber with an adhesive so that the grain of alllaminations is essentially parallel.4. Summary of Test Method4.1 An adhesive to be evaluated for suitability in structural wood products in ter
20、ms of resistance to creep is used to prepare blockshear test specimens which will then be loaded to a prescribed level of stress.4.2 Following the adhesive manufacturers recommendations two 2ply test assemblies of a designated species are laminatedfollowing specific recommendations of wood selection
21、 and preparation.4.3 After a designated curing period, eight 25 mm 1.0 in. by 25 mm 1.0 in. block shear specimens are prepared from eachassembly and preconditioned.4.4 Both sides of the geometric center of each specimen are marked with a scribe.4.5 The block shear specimens from each assembly are lo
22、aded to the required stress in a prescribed compression-shear creeptest jig and then subjected to a designated test environment in terms of temperature, moisture level and time.4.6 At the completion of the designated exposure time, the amount of creep for each specimen is measured and reported along
23、with the average creep for the group of specimens.5. Significance and Use5.1 This test method evaluates the performance of the adhesive in laminated wood as measured by resistance to creep understatic load.5.2 Test results from the evaluation of adhesive creep resistance, under designated environmen
24、tal conditions of the test, providea measure of the adhesives ability to withstand constant loading over a relatively long period of time.FIG. 1 Creep Measurement of Test SpecimenD7966/D7966M 1625.3 Creep measured with this test method is normally used in conjunction with specifications such as, but
25、 not limited toSpecification D2559 and CSA O112.9 to confirm suitability of an adhesive to resist creep under designed loads when subjectedto specific levels of stress, load duration and environmental conditions.6. Apparatus6.1 Testing MachineA testing machine, or other suitable loading machine, cap
26、able of applying compression loads from 0 to22 kN (5000 lbf) having an accuracy of 61 % when calibrated in accordance with Practice E4, and cross-head speeds from 0.3to 10 mm/min 0.01 to 0.40 in./min is sufficient for this test method. A minimum vertical space of 510 mm 20 in. is requiredto compress
27、 the loading spring in the creep-test apparatus.6.2 Creep-Test ApparatusStatic loads shall be applied and maintained on block-shear specimens by means of thecompression-loaded creep-test cylinder shown in Fig. 2. The specific spring used in the apparatus shown in Fig. 2 has a designload of 2300 lbf
28、(10 kN) and is made of corrosion-resistant components so that is can be used in high-temperature and humidenvironments for prolonged periods without concern for damaging the apparatus or interfering with the effectiveness. Theapparatus is spring-loaded and shall contain a mechanism to provide a self
29、 aligning surface to account for specimens where thetwo bearing surfaces are not perfectly parallel.NOTE 1Although this particular spring has a design load of 10 kN (2300 lbf) others of greater or less capacity may be substituted. Varying springcapacities with outside diameters no greater than the c
30、ylinder inside diameter are available. Additional details, including options for providing selfaligning surface can be found in Adjunct ADJD4680.6.2.1 For creep testing up to 50C 122F, it is not necessary to adjust the spring or load to compensate for the effects ofchanging temperature. It is only n
31、ecessary that the apparatus, with included specimen, be preconditioned to the test temperaturebefore the test load is applied to the spring. The preheated apparatus must be wrapped with a piece of flexible thermal insulationmaterial while the test load is applied to the specimen. After loading and m
32、easurements, return the loaded apparatus to the testenvironment.NOTE 2Since there are no significant changes in temperature before or after loading, no adjustments are needed in the spring.6.2.1.1 When conducting creep testing a temperatures of 50C 122F or higher the applied stress level shall be in
33、creased tocompensate for the decrease in the spring constant. This can be determined by comparing the spring constant for the spring at roomtemperature to that when the spring is heated to the specified temperature. Laboratories shall establish that the spring constant,when repeatedly heated to the
34、specified temperature, is consistent between each use. Compensation for spring stiffness attemperature shall be determined by the testing laboratory.6.3 MicroscopeA microscope with an objective lens of at least 7 magnification or a magnifying glass, such as a 10 loupeis required to measure displacem
35、ent of scribe marks across the two adherends of a specimen to measure and record any creep thathas occurred. A linear traveling binocular microscope is ideally suited to creep measurements; however, a microscope fitted withan appropriately graduated scale is satisfactory.6.4 Environmental ChambersAn
36、 environmental chamber is required to precondition test specimens to their intended testenvironment and subject the conditioned specimens, after loading to a specified shear stress, to the required conditions oftemperature and relative humidity. In the absence of specific required test conditions of
37、 temperature, relative humidity, appliedshear stress and time under test, Table 1 provides examples of standard conditions that are considered appropriate.6.4.1 Conditioning equipment, such as but not limited to ovens and humidity cabinets, should be capable of maintaining aconstant temperature with
38、in 62.0C 63.6F of the set-point and constant relative humidity within 65 % of the set-point at agiven temperature for each of the test conditions selected for evaluation.NOTE 3The standard conditions listed in Table 1 are considered appropriate to evaluate the suitability of a structural wood adhesi
39、ve for creepresistance when exposed to a variety of environmental exposure conditions up to and including continuous exposure to the weather. Other conditions oftemperature, humidity, load duration and stress level may be used or specified provided that the conditions and their precision has been de
40、termined andreported. Specific and appropriate product standards, qualified evaluation and code approval agencies, or combinations thereof, may specify the targetedstress level for a particular species or species group, including exposure duration, when adopting this test method.NOTE 4Section 8.6 pr
41、ovides requirements for preconditioning specimens prior to testing.7. Materials7.1 Wood Selection, Preparation and ConditioningUse any softwood or hardwood single species planned for bonding andintended for use and considered suitable for bonded structural wood products. The selected species shall b
42、e compatible with thetest structural wood adhesive and determined suitable to evaluate resistance to creep using this test method as required, specifiedor desired. Bond only to vertical grain wood surfaces (Note 6).NOTE 5This test only measures resistance to creep; for characterizing additional adhe
43、sive properties related to the selected species, such asbondability, an alternative test method or specification, including but not limited to Specification D2559 should be considered.NOTE 6The bond face is considered vertical grain when the growth rings make an angle of between 45 and 90 to the fac
44、e.7.1.1 For the species under evaluation, each piece of wood selected for use in resistance to creep testing and in accordance withthis test method shall have a minimum specific gravity as indicated in Table 1, Required Shear Strength for Structural LaminatedD7966/D7966M 163FIG. 2 Creep Test Apparat
45、usD7966/D7966M164Wood Products, in Specification D2559. For species not included in Table 1 of Specification D2559 consult the USDA WoodHandbook5 for the reported specific gravity at 12 % moisture content (Note 7).NOTE 7For the species selected for evaluation, the wood quality selected is such that
46、it is able to sustain the applied stress under the selectedenvironmental conditions. For species not found in Table 1 of Specification D2559, trial tests should be conducted to confirm the wood has adequatestrength for the specific test. Wood with higher specific gravity and slower growth rate (rela
47、tively large number of growth rings per inch) have been foundto be effective metrics for selecting suitable wood substrate for resistance to creep testing.7.1.2 The wood shall have a slope of grain not steeper than 1 in 15 on any face or any edge. The wood shall contain no knotslarger than 3 mm 18 i
48、n. in diameter and shall be free of decay, machining defects (such as chipped grain, dubbed ends, feed rollpolish, coarse knife marks, and feed roll compression), 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 a relative h
49、umidity of 50 to 70 % (preferably 65 %) until a moisturecontent of 8 to 14 % has been obtained.7.1.3.1 Conditioning for wood used for sample preparation by hot press adhesives that require a moisture content less than 8 %,should be in accordance with the adhesive manufacturers recommendations.8. Test Specimens8.1 The standard specimen shall be the block-shear specimen illustrated in Fig. 3.8.2 The test adhesive is used to bond the selected wood species together following procedures found in 8.4. The shear area ofthe stand
