1、Designation: D4688/D4688M 14Standard Test Method forEvaluating Structural Adhesives for Finger Jointing Lumber1This standard is issued under the fixed designation D4688/D4688M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the ye
2、ar 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 is designed to evaluate adhesives forfinger jointing lumber used in the manufacture of a variet
3、y ofbonded structural wood products such as structural gluedlaminated timber. It tests the tensile strength of joints under thefollowing treatments: dry with no treatment, wet after onevacuum-pressure soak treatment, and wet after cyclic boil-drytreatment.1.2 This test method is intended neither for
4、 quality controlas the test assemblies are selected for the absence of defectsusually found in run-of-the-mill finger joints nor as a substitutefor in-plant qualification of end joints, including full-scale jointtests.NOTE 1This test method is specifically designed to evaluate adhesivesfor use in fi
5、nger jointing lumber using small scale test specimens cut fromcarefully selected finger joint assemblies. In contrast, plant qualificationand quality control require tests of full scale end joints selected randomlyfrom production, designed to evaluate parameters beyond adhesiveperformance which affe
6、ct the performance of the end use product.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two
7、systems may result in non-conformancewith the 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 determine the applica-bility
8、 of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D907 Terminology of AdhesivesD2559 Specification for Adhesives for Bonded StructuralWood Products for Use Under Exterior Exposure Condi-tionsD5266 Practice for Estimating the Percentage of WoodFailure in Adhesive Bond
9、ed JointsE4 Practices for Force Verification of Testing Machines3. Terminology3.1 DefinitionsMany terms in this test method are definedin Terminology D907.3.2 Definitions of Terms Specific to This Standard:3.2.1 billet, na piece cut from a vertical finger jointassembly as an intermediate step in mak
10、ing specimens.3.2.2 horizontal finger joint, na joint formed by bondingtwo precut members shaped like fingers where the profile isvisible on the edge of the lumber (see Fig. 1a).3.2.3 vertical finger joint, na joint formed by bonding twoprecut members shaped like fingers where the profile is on thew
11、ide face of the lumber (see Fig. 1b).3.2.4 finger joint assembly, na short portion of two boardsjoined at their ends by an adhesively bonded finger joint tocreate a longer piece, frequently referred to as an assembly.3.2.5 sample, na group of finger joint assemblies obtainedfrom a finger joint produ
12、ction line or laboratory prepared fingerjoints selected for statistical purposes.3.2.6 specimen, nan individual test piece prepared tospecific dimensions for the purpose of determining the adhe-sive performance in accordance with the tension tests describedin this test method.4. Significance and Use
13、4.1 This test method is specifically designed to measure theperformance of adhesives in finger joints manufactured underproduction line conditions.4.1.1 The test method can be adapted to evaluate theadhesive performance of laboratory produced finger jointsusing commercial finger joint cutting heads
14、with finger jointsproduced following the adhesive manufacturers recommenda-tions. The conditions under which the finger joints wereproduced, including any limitations, are to be reported in9.1.2.2 (see Note 2).1This test method is under the jurisdiction of ASTM Committee D14 onAdhesives and is the d
15、irect responsibility of Subcommittee D14.30 on WoodAdhesives.Current edition approved Nov. 1, 2014. Published January 2015. Originallyapproved in 1987. Last previous edition approved in 2013 as D4688 99 (2013).DOI: 10.1520/D4688_D4688M-14.2For referenced ASTM standards, visit the ASTM website, www.a
16、stm.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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1NOTE 2If
17、 laboratory prepared finger joints are to be produced, recorddetails related to adhesive used, its preparation, application to the cutfinger joint, appropriate bonding parameters and limitations in theproduction of the finger joint assemblies.4.2 The results of the test method may be used to certify
18、 anadhesive as suitable for finger jointing lumber under produc-tion line conditions where the intended end use of the fingerjointed lumber may be in a variety of bonded structural woodproducts.4.2.1 When the test results are to be used for certification ofan adhesive a standard wood species shall b
19、e used.4.2.1.1 Standard species may be found in Table 1 ofSpecification D2559.5. Apparatus5.1 Test Machine, capable of applying a tensile force, up to23 kN (5000 lbf), having an accuracy of 61 % when calibratedin accordance with Practice E4, and equipped with Templin(wedge-action) grips with grip ar
20、ea of 38 by 75 mm 112 by 3in.5.2 Vacuum Pressure Vessel, capable of drawing and hold-ing a vacuum of at least 635 mm 25 in. of mercury (sea level)for 30 min, holding a pressure of 620 6 35 kPa (75 6 2 psi)for 30 min, and capacity to ensure that all of the specimens areat least 50 mm 2 in. below the
21、water level during thecomplete vacuum-pressure cycle.5.3 Tank for Boiling, capacity such that all specimens are atleast 51 mm 2 in. below the water level for the duration of theboil cycles.5.4 Oven, capable of operating continuously for 20 h at 636 2C 145 6 5F with sufficient air circulation to lowe
22、r themoisture content of the group of specimens from saturation tono more than 8 % within 20 h.5.4.1 Timer, to shut the oven off automatically is desirable.6. Specimen Preparation6.1 Obtain a sample consisting of either 20 horizontal orvertical finger joint assemblies from a finger joint productionl
23、ine or, when evaluating laboratory prepared finger joints, froma population of laboratory prepared finger joints. The boardsmust be nominal 2 by 4-in. or 2 by 6-in.6.1.1 Identify and record the wood species, jointconfiguration, average specific gravity and moisture content.6.2 Horizontal Joint (Fig.
24、 1(a):6.2.1 Joint one face of each assembly until the finger on thesurface is feathered as shown in Fig. 1(c).NOTE 3In the context of this test method, feathering is described as aprocess where the surface containing the respective vertical or horizontaljoint is planed to approximately center of the
25、 visible edge of the joint (seeFig. 1(c).6.2.2 Joint one edge of the assembly for end cutting andripping at a later stage.6.2.3 Plane the second face of the assembly until the fingeron the surface is feathered while maintaining an assemblythickness of about 35-mm 138-in.NOTE 4It is more important to
26、 feather the finger than to maintain the35-mm 138-in. thickness.6.2.4 Cut the assembly to a 305-mm 12-in. length with thefinger joint at the center.6.2.5 Rip individual specimens 6.4-mm 14-in. thick fromthe assembly starting with the jointed edge of the assembly (see6.2.2) against the saw guide. A t
27、hin hollow-ground rip sawblade is preferred but the important criterion is the straightnessof the cut.6.2.5.1 Check cut specimens for uniform thickness through-out. Thickness shall not vary by more than 0.5 mm 0.02 in.6.2.5.2 Number the specimens in order from one side of theassembly to the other.6.
28、3 Vertical Joint (Fig. 1(b):6.3.1 Joint one edge of the finger joint assembly.6.3.2 Joint one face of the finger joint assembly.6.3.3 With the jointed edge against the saw guide, rip billets40 mm 1916 in. wide from the assembly.NOTE 5The 40-mm 1916-in. dimension is not critical but thisdimension mus
29、t be enough to allow feathering the fingers in subsequentsteps.6.3.4 Joint and plane the sides of each billet so the exposedsides of the fingers are feathered as described in 6.2.1 and6.2.3.6.3.5 Rip four individual specimens of 6.4-mm 14-in.thickness from each billet of the assembly as in 6.2.5.6.3
30、.5.1 Number the specimens in order from one side of theassembly to the other. Use the same order for each assembly.6.4 Inspect specimens for defects. Assemblies yieldingspecimens that have obvious strength-reducing characteristicssuch as: low visual density, knots, steep slope of grain,compression w
31、ood, compression failures, decay, pitch pockets,or stress risers due to errors in specimen preparation shall berejected.FIG. 1 Finger Joint Assembly and Specimen DescriptionsD4688/D4688M 1426.5 Condition all specimens to equilibrium moisture content(EMC) at 2 6 2C 68 6 3F and 65 6 5 % relative humid
32、ity.Monitor the weight of randomly selected specimens periodi-cally to determine when equilibrium is reached.6.6 Weigh all specimens to the nearest 0.01 g and record theweight. Measure the width and thickness of the specimens tothe nearest 0.25 mm 0.010 in. and record the measurements.6.7 Randomly a
33、ssign two specimens from each of the 20finger joint assemblies in the sample to each test (that is, dry,soak, and boil). (Note this requires only six specimens fromeach assembly, the other specimens are extra.) Fig. 2 shows thesource and distribution of the specimens.NOTE 6Thus: 20 assemblies 2 spec
34、imens/assembly = 40 specimens/test.7. Procedure7.1 Dry Test (No Treatment):7.1.1 As described in 6.7, assign 40 specimens to this test.Test each specimen in tension to failure by loading at a rate of5 mm/min (0.20 in./min. Maintain a space of 155 6 6mm66 0.25 in. between the ends of the jaws of the
35、grips. Recordthe load at failure.NOTE 7Be very careful to align the specimen with the principal axisof the test grip. Failure to do this will increase the variability of the results.Markings, spacers on the grips, or some other device is recommended toensure proper front-to-rear alignment, and a plu
36、mb bob or other device isrecommended to ensure the vertical alignment.7.1.2 Determine and record the percentage of wood failureand the failure mode using the criteria given in Annex A1independent of any knowledge of the strength test result.7.2 Cold Water Vacuum-Pressure Soak Test:7.2.1 As described
37、 in 6.7, assign 40 specimens to this test.Place specimens in a vacuum-pressure vessel with spacersbetween them so that water has free access to all surfaces. Fillthe vessel with tap water at 18.5 to 27.5C 65 to 80F so thatall specimens are at least 51 mm 2 in. below the surface of thewater. After fi
38、lling, seal the vessel and draw a vacuum of atleast 635 mm 25 in. of mercury (sea level). Hold the vacuumfor 30 min, then release the vacuum and apply pressure of 6206 35 kPa (75 6 2 psi). Hold this pressure for 2 h, then release.Remove the specimens from the pressure vessel and place themsubmerged
39、in water at room temperature. Remove the speci-mens individually from the water, and test while wet within1h.FIG. 2 Flowchart of the Source and Allocation of Individual Test SpecimensD4688/D4688M 1437.2.2 Test wet in tension as described in 7.1.1. Record theload at failure.7.2.3 Dry tested specimens
40、 to less than 8 % moisturecontent, then determine and record the percentage of woodfailure and the failure mode as described in 7.1.2.7.3 Cyclic Boil Test:7.3.1 As described in 6.7, assign 40 specimens to this test.Place specimens in the boil tank with spacers so that water hasfree access to all sur
41、faces. Fill with water such that thespecimens are at least 51 mm 2 in. below the water level. Boilspecimens for 4 h, then dry them in an oven at 63 6 2C 1456 5F with sufficient air circulation to lower the moisturecontent to 63 % of their conditioned weight recorded in 6.6 inno more than 20 h.NOTE 8
42、The rate of air circulation, the size of the load of specimensin the oven, and the spacing of the specimens greatly affect drying timeand the steepness of the moisture gradient in the specimen. Variation ofthese factors strongly affects the repeatability of the test method. In orderto obtain accepta
43、ble repeatability (within-laboratory variability) andreproducibility (between laboratories), the drying should be conducted sothat the specimens reach 63 % of their original weight within the samedrying period in every test. One way to do this is to monitor the weight ofthe specimens and adjust the
44、oven vents so the specimens reach the targetweight in 15 to 20 h. As an aid, the drying time and airflow required canbe established with the extra specimens cut from the 20 assemblies.7.3.2 Repeat the boil-dry cycle five more times; exceptduring the final cycle do not dry the specimens. Remove thesp
45、ecimens from the boiling vessel and cool in running water at18 to 27C 65 to 80F for 1 h. Remove the specimensindividually from the water, and test while wet within 1 h.7.3.3 Test wet in tension as described in 7.1.1. Record theload at failure.7.3.4 Dry tested specimens to less than 8 % moistureconte
46、nt, then determine and record the percentage of woodfailure and the failure mode as described in 7.1.2.NOTE 9Nonmandatory guidelines for joint performance follow:Mode 1 An unacceptable failure.Modes 2 and 3 Unconditionally acceptable failure.Modes 4, 5, and 6 Conditionally acceptable failure if stre
47、ngth isacceptable.8. Calculation of Results8.1 Calculate the tensile stress at failure in megapascals(pounds-force per square inch) as the load at failure in newtons(pounds-force) divided by the cross-sectional area of thespecimen provided by the measurements of 6.6.8.2 Estimate the 25th, 50th, and
48、75th percentiles for thegroup of specimens in the following manner:8.2.1 Arrange the specimens in order of increasing strength.8.2.2 Estimate the 25th percentile as the average of the 10thand 11th lowest strength values.8.2.3 Estimate the 50th percentile as the average of the 20thand 21st values.8.2
49、.4 Estimate the 75th percentile as the average of the 30thand 31st strength values.8.3 Determine the upper and lower adjacent values (seedefinition below) for the group of specimens. Determine theoutliers (test values outside the range expressed by the upperand lower adjacent values).25th percentile = Q1 = the value below which 25 % of the observationsfall.50th percentile = Q2 = the value below which 50 % of the observationsfall.75th percentile = Q3 = the value below which 75 % of the observatio
