1、Designation: D7247 16Standard Test Method forEvaluating the Shear Strength of Adhesive Bonds inLaminated Wood Products at Elevated Temperatures1This standard is issued under the fixed designation D7247; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e 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 standard describes a test method for evaluating thecomparative shear strength of
3、a planar adhesive bond at bothambient and elevated temperatures relative to the performanceof solid wood under the same conditions. The test method isbased on the breaking load after the specimen is exposed toeither ambient or a constant elevated temperature for a speci-fied duration as described in
4、 Section 7. This standard does notpreclude the development and implementation of other meth-ods that provide equivalent performance meeting the intent ofthis method.1.2 This test method is intended for the evaluation ofadhesives that can be used to assemble test specimens inaccordance with Test Meth
5、od D905. The evaluation of othertypes of adhesives, such as the binder systems used forstrand-based products, is beyond the scope of this test method.1.3 This test method is intended for the evaluation ofadhesives as a component of laminated wood products atelevated temperatures. The evaluation of f
6、ire performance onfire-rated laminated wood products or assemblies is beyond thescope of this test method.1.4 This test method may be used for the evaluation of heatdurability for binder adhesives used in strand-based structuralwood composites, such as oriented strand lumber (OSL) andlaminated stran
7、d lumber (LSL), by substituting strand-basedcomposite specimens for the bonded specimens.1.5 The exact formulation of adhesive supplied to themanufacturer of laminated wood products shall be evaluated.Modifications to the adhesive formulation require a separateevaluation unless approved by the manuf
8、acturer of the lami-nated wood product, qualified agency, and code evaluationagency.1.6 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.7 This standard does not purport to address all of thesafety concerns, such as the fire h
9、azard, associated with its use.It is the responsibility of the user of this standard to establishappropriate safety and health practices and determine theapplicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D905 Test Method for Strength Properties of Adhesi
10、veBonds in Shear by Compression LoadingD907 Terminology of AdhesivesD2395 Test Methods for Density and Specific Gravity (Rela-tive Density) of Wood and Wood-Based MaterialsD2915 Practice for Sampling and Data-Analysis for Struc-tural Wood and Wood-Based ProductsD4933 Guide for Moisture Conditioning
11、of Wood andWood-Based MaterialsD5266 Practice for Estimating the Percentage of WoodFailure in Adhesive Bonded JointsD5456 Specification for Evaluation of Structural CompositeLumber Products2.2 Other Documents:ANSI A190.1 American National Standard for Wood Prod-ucts Structural Glued Laminated Timber
12、3ANSI/AWC NDS-2015 National Design Specification forWood Construction (NDS)3Wood Handbook Wood as an Engineering Material43. Terminology3.1 Definitions:1This test method is under the jurisdiction of ASTM Committee D14 onAdhesives and is the direct responsibility of Subcommittee D14.30 on WoodAdhesiv
13、es.Current edition approved April 1, 2016. Published April 2016. Originallyapproved in 2006. Last previous edition approved in 2007 as D7247 07a1whichwas withdrawn January 2016 and reinstated in April 2016 as D7247 16. DOI:10.1520/D7247-16.2For referenced ASTM standards, visit the ASTM website, www.
14、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.3APA The Engineered Wood Association, 7011 S. 19th St., Tacoma, WA98466, www.apaword.org.4Available from U.S. Department
15、ofAgriculture, Forest Service, Forest ProductsLaboratory, One Gifford Pinchot Drive Madison, WI 53726, www.fpl.fs.fed.us.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.1 Many terms in this test method are defined in Termi-nology
16、D907.4. Significance and Use4.1 A discussion of the issues and limitations associatedwith the measurement of strength properties of adhesive bondsin shear by compression loading is found in Test Method D905.4.2 While various combinations of test temperature and heatexposure duration can be used, the
17、 provisions specified in 7.2.4shall be based on the understanding that the objective of thistest method is to evaluate adhesive bond performance justbefore wood begins to burn and the elevated temperature isselected to be slightly below the unpiloted ignition temperaturefor wood when taken into acco
18、unt the specific product and itsend-use applications.4.3 When using this test method, consideration shall begiven to the unique production conditions, such as woodmoisture content, applied spread rate, press pressure, andcuring temperature of the adhesive.5. Apparatus5.1 The testing machine and shea
19、ring tool described in TestMethod D905 have been found to be satisfactory for the testmethod described herein.5.2 An oven capable of maintaining the targeted test tem-perature to within 61 % and with sufficient air circulation toprovide constant temperature conditions within the oven inte-rior is re
20、quired for heating the specimens.5.3 Thermometers/thermocouples capable of measuring thetemperature of the test specimen and air are required.NOTE 1Type “K” 24 gauge thermocouples are recommended.5.4 Dessicator, capable of maintaining the dry condition ofthe dried specimen sets until exposure and te
21、sting.NOTE 2Fresh or freshly regenerated desiccant is recommended foreach test.6. Test Specimen6.1 The wood species used for the tests shall be the woodspecies used in commercial production. Wood species withsimilar bonding characteristics in accordance with ANSIA190.1 shall be permitted to be group
22、ed for the purpose of thistest method. Nominal 2-in. thick lumber shall be used tomanufacture the test specimens. The lumber shall have theannual growth rings oriented 45 to 90, as measured from thewide face (vertical grain), and be free of defects and at theequilibrium moisture content recommended
23、by the manufac-turer of the adhesive. If no such recommendation exists, themoisture content shall be between 10 and 12 % prior tobonding following the moisture conditioning procedures de-scribed in Guide D4933. Each piece of lumber used as part ofthis test method shall have a specific gravity equal
24、to orexceeding the value specified in the National Design Specifi-cation for Wood Construction (NDS) for the wood species, asdetermined in accordance with Test Methods D2395 based onoven-dry weight and volume. The specific gravity determina-tion for each piece of lumber shall be permitted to becondu
25、cted on the ends trimmed from the lumber during thepreparation of the bonded and solid wood test specimens. Theside-matched components from which the bonded and solidwood control specimens are prepared shall have a specificgravity within 0.02 of each other (for example, if the solidwood control spec
26、imens have a specific gravity of 0.50, thebonded specimens shall have a specific gravity between 0.48and 0.52).6.2 Specimens shall be prepared in accordance with thegeneral principle of Test Method D905. To ensure that pieceswith a mean specific gravity are bonded together, a single pieceof the nomi
27、nal 2 in. thick lumber shall provide, at a minimum,the two pieces (lumber) necessary for each bonded specimenand a side-matched solid wood (control) specimen. An ex-ample of the shear specimen-cutting pattern is shown in Fig. 1.Care shall be exercised to ensure the same annual ringorientation when b
28、onding the lumber together into a bondedassembly.6.3 The mating surfaces of the lumber used to prepare thebonded specimens shall be surfaced no more than 24 h prior tobonding. The adhesive preparation, spread rate, clampingNoteSee Fig. 2 for specimen dimension.FIG. 1 Example of Side-Matched Specimen
29、 Fabrication (Using Nominal 2 by 6 in. Lumber with Bonded Specimens and Side-MatchedSolid Wood Control Specimens)D7247 162pressure and clamping time shall follow the adhesive manu-facturers recommendations. The production conditions for theend-use products shall also be considered (see 4.3).6.4 A mi
30、nimum of 20 bonded specimens shall be preparedin accordance with Fig. 2. The bonded specimens will have athickness less than the specified 38 mm (1.5 in.) as describedin Test Method D905 due to surfacing from nominal 2-inlumber. In addition, a minimum of 20 solid wood (without thebondline) control s
31、pecimens side-matched with the bondedspecimens shall be prepared as shown in Fig. 1. The side-matched solid wood specimens shall be surfaced to the samethickness as the bonded specimens. The bonded and matchedsolid wood control specimens shall be prepared as 20 pairs.6.5 A total of 10 pairs of bonde
32、d and matched solid woodcontrol specimens shall be tested at ambient temperature andthe remaining 10 pairs of bonded and matched solid woodcontrol specimens shall be tested at the targeted elevatedtemperature.6.6 For specimens tested at the elevated temperature, a holeshall be drilled through one la
33、mination at a 90 angle to thebondline and extending 0.6 mm (132 in.) past the bondline. Thedrilled hole shall allow the thermocouple wire casing to fitsnugly inside the hole (see Fig. 3), with the exposed portion ofthe thermocouple wire touching the bondline of the bondedspecimen or the geometric ce
34、nter (shear plane) of the matchedsolid wood control specimen. The tip of the thermocouple wireshall have a maximum of 1 mm (0.040 in.) of insulationremoved.NOTE 3Experience has shown that stripping the wire insulationapproximately 12.7 mm (0.5 in.), twisting the wires together, and cuttingthe expose
35、d wire back to 1 mm (0.040 in.) gives consistent results.Damage-to or improper-removal-of thermocouple wire insulation in-creases the possibility of inaccurate temperature readings in the oven.Prior to re-using thermocouple wire, it is to be re-tested to ensure thataccurate temperature readings are
36、being provided.6.7 All specimens shall be oven dried for 48 h at 60 6 2C(140 6 4F) and placed in an atmosphere, such as a desiccator,to allow for cooling in dry conditions.NOTE 4The intent of the oven drying is to remove the moisture fromthe wood adherend so that the specimen weight reduction during
37、 testing inaccordance with Section 7 is primarily due to thermal degradation.6.8 After cooling, the specimen weight shall be determined.The width and length of the test specimen shall be measuredand recorded, at the bondline, to the nearest 0.25 mm (0.010in.) to determine the shear area. Test specim
38、ens are to be keptin the desiccator until just prior to testing in accordance withSection 7.7. Test Procedures7.1 Specimens at Ambient Temperature Condition:7.1.1 A sample set consisting of 10 solid wood controlspecimens and 10 bonded specimens shall be tested at ambientlaboratory conditions in acco
39、rdance with the procedures out-lined in Test Method D905. Loads shall be applied with acontinuous motion of the movable head at a rate of 5 mm (0.20in.)/min until failure. The ultimate load shall be recorded alongwith an estimation of wood failure (to the nearest 5 %) inaccordance with Practice D526
40、6.7.2 Specimens at Elevated Temperature Condition:7.2.1 The oven shall be preheated to the targeted tempera-ture using a thermocouple to monitor the interior oven tem-perature (see Note 5 for additional information). The oven airtemperature shall be held at the desired level for a sufficientamount o
41、f time to heat all of the components of the oven to thetargeted temperature.7.2.2 Only one specimen, either one solid wood controlspecimen or one side-matched bonded specimen, shall beplaced in the oven at a time. A thermocouple wire shall beplaced into the specimen as described in 6.6 and shown in
42、Fig.3. The drilled hole shall be backfilled, if necessary, with glassinsulation, high temperature silicon, or a similar protectivebarrier. The backfill materials shall be allowed to cure accord-ing to the manufacturers recommendations prior to testing.The starting time and specimen oven-dry weight,
43、after thebackfill materials are cured, as applicable, shall be recorded.7.2.3 The bondline temperature of the bonded specimen orthe temperature at the shear plane of the matched solid woodcontrol specimen shall be monitored. Because of the insulatingnature of wood, the bondline temperature may be di
44、fferentfrom the oven air temperature and thus the targeted tempera-ture. Therefore, as the specimen approaches the targetedtemperature, the rate of heating shall be slowed to a rate thatFIG. 2 Form and Dimensions of a Bonded SpecimenFIG. 3 Top View (Left) and Side View (Right) of Drilled Hole forThe
45、rmocouple PlacementD7247 163can be easily controlled either manually or by using a propor-tional temperature controller with an integral and derivative(PID) control algorithm. The amount of time for the specimento reach the targeted temperature shall not be less than 30 min.nor more than 90 min.NOTE
46、 5When a manually controlled oven is used, previous studieshave shown that for a targeted temperature of 232C (450F), the heatshould be turned down when the interior temperatures of the specimensreach approximately 210C (410F). The bondline temperature willcontinue to rise, but the rate of increase
47、will decrease. As the rate oftemperature rise decreases, heat can be re-introduced, if necessary, toattain the targeted bondline temperature. Practice runs with “dummy”specimens are recommended before the collection of actual data. The useof a PID device may help the temperature control.7.2.4 The ti
48、me when the bondline temperature of thebonded specimen or the temperature at the shear plane of thematched solid wood control specimen reaches the targetedtemperature shall be recorded. The bondline temperature of thebonded specimen or the shear plane of the solid wood controlspecimen shall be maint
49、ained at the targeted temperature,within the tolerance stated in 5.2, for at least 10 min. Theexposure duration shall be pre-selected based on the specificproduct, its end-use applications and shall be consistently usedfor both solid wood control and bonded specimens. A range ofshear strength retentions for solid wood control specimensshall be permitted to be specified in lieu of an exposureduration.NOTE 6The product standard, manufacturer of the laminated woodproduct, qualified agency, or code evaluation agency, or combinationsthereof, may specify the t
