1、Designation: D7247 16D7247 17Standard 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 o
2、r, in the 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 the comparative shear str
3、ength of a planar adhesive bond at bothambient and elevated temperatures relative to the performance of solid wood under the same conditions. The test method is basedon the breaking load after the specimen is exposed to either ambient or a constant elevated temperature for a specified durationas des
4、cribed in Section 7. This standard does not preclude the development and implementation of other methods that provideequivalent performance meeting the intent of this method.1.2 This test method is intended for the evaluation of adhesives that can be used to assemble test specimens in accordance wit
5、hTest Method D905. The evaluation of other types of adhesives, such as the binder systems used for strand-based products, isbeyond the scope of this test method.method, except as noted in 1.4.1.3 This test method is intended for the evaluation of adhesives as a component of laminated wood products a
6、t elevatedtemperatures. The evaluation of fire performance on fire-rated laminated wood products or assemblies is beyond the scope of thistest method.1.4 This test method may be used for the evaluation of heat durability for binder adhesives used in strand-based structural woodcomposites, such as or
7、iented strand lumber (OSL) and laminated strand lumber (LSL), by substituting strand-based compositespecimens for the bonded specimens.1.5 The exact formulation of adhesive supplied to the manufacturer of laminated wood products shall be evaluated.Modifications to the adhesive formulation require a
8、separate evaluation unless approved by the manufacturer of the laminatedwood product, qualified agency, and code evaluation agency.1.6 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.1.7 This standard does not purport to addr
9、ess all of the safety concerns, such as the fire hazard, if any, associated with its use.It is the responsibility of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practicesand determine the applicability of regulatory limitations prior to use.1.8 T
10、his international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (
11、TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D905 Test Method for Strength Properties of Adhesive Bonds in Shear by Compression LoadingD907 Terminology of AdhesivesD2395 Test Methods for Density and Specific Gravity (Relative Density) of Wood and Wood-Based MaterialsD2915 Practice for S
12、ampling and Data-Analysis for Structural Wood and Wood-Based ProductsD4933 Guide for Moisture Conditioning of Wood and Wood-Based MaterialsD5266 Practice for Estimating the Percentage of Wood Failure in Adhesive Bonded JointsD5456 Specification for Evaluation of Structural Composite Lumber Products1
13、 This test method is under the jurisdiction of ASTM Committee D14 on Adhesives and is the direct responsibility of Subcommittee D14.30 on Wood Adhesives.Current edition approved April 1, 2016Oct. 15, 2017. Published April 2016November 2017. Originally approved in 2006. Last previous edition approved
14、 in 20072016as D7247 07a1 which was withdrawn January 2016 and reinstated in April 2016 as D7247 16. DOI: 10.1520/D7247-16.10.1520/D7247-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume
15、 information, refer to the standards Document Summary page on the ASTM website.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 version. Becauseit may not be technically possible to adequat
16、ely 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 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken
17、, PA 19428-2959. United States12.2 Other Documents:ANSI A190.1 American National Standard for Wood Products Structural Glued Laminated Timber 3ANSI/AWC NDS-2015 National Design Specification for Wood Construction (NDS) 3Wood Handbook Wood as an Engineering Material 43. Terminology3.1 Definitions:3.1
18、.1 Many terms in this test method are defined in Terminology D907.4. Significance and Use4.1 Adiscussion of the issues and limitations associated with the measurement of strength properties of adhesive bonds in shearby compression loading is found in Test Method D905.4.2 While various combinations o
19、f test temperature and heat exposure duration can be used, the provisions specified in 7.2.4shall be based on the understanding that the objective of this test method is to evaluate adhesive bond performance just beforewood begins to burn and the elevated temperature is selected to be slightly below
20、 the unpiloted ignition temperature for wood whentaken into account the specific product and its end-use applications.4.3 When using this test method, consideration shall be given to the unique production conditions, such as wood moisturecontent, applied spread rate, press pressure, and curing tempe
21、rature of the adhesive.5. Apparatus5.1 The testing machine and shearing tool described in Test Method D905 have been found to be satisfactory for the test methoddescribed herein.5.2 An oven capable of maintaining the targeted test temperature to within 61 % and with sufficient air circulation to pro
22、videconstant temperature conditions within the oven interior is required for heating the specimens.5.3 Thermometers/thermocouples capable of measuring the temperature of the test specimen and air are required.NOTE 1Type “K” 24 gauge thermocouples are recommended.5.4 Dessicator, capable of maintainin
23、g the dry condition of the dried specimen sets until exposure and testing.NOTE 2Fresh or freshly regenerated desiccant is recommended for each test.6. Test Specimen6.1 The wood species used for the tests shall be the wood species used in commercial production. Wood species with similarbonding charac
24、teristics in accordance with ANSI A190.1 shall be permitted to be grouped for the purpose of this test method.Nominal 2-in. thick lumber shall be used to manufacture the test specimens.The lumber shall have the annual growth rings oriented45 to 90, as measured from the wide face (vertical grain), an
25、d be free of defects and at the equilibrium moisture contentrecommended by the manufacturer of the adhesive. If no such recommendation exists, the moisture content shall be between 10and 12 % prior to bonding following the moisture conditioning procedures described in Guide D4933. Each piece of lumb
26、er used3 APA The Engineered Wood Association, 7011 S. 19th St., Tacoma, WA 98466, www.apaword.org.4 Available from U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, One Gifford Pinchot Drive Madison, WI 53726, www.fpl.fs.fed.us.NoteSee Fig. 2 for specimen dimension.FIG. 1 E
27、xample of Side-Matched Specimen Fabrication (Using Nominal 2 by 6 in. Lumber with Bonded Specimens and Side-MatchedSolid Wood Control Specimens)D7247 172as part of this test method shall have a specific gravity equal to or exceeding the value specified in the National DesignSpecification for Wood Co
28、nstruction (NDS) for the wood species, as determined in accordance with Test Methods D2395 basedon oven-dry weight and volume. The specific gravity determination for each piece of lumber shall be permitted to be conductedon the ends trimmed from the lumber during the preparation of the bonded and so
29、lid wood test specimens. The side-matchedcomponentsstock from which the bonded and solid wood control specimens are prepared shall have a specific gravity within 0.02of each other (for example, if the solid wood control specimens have a specific gravity of 0.50, the bonded specimens shall havea spec
30、ific gravity between 0.48 and 0.52).60.02 of each other.6.2 Specimens shall be prepared in accordance with the general principle of Test Method D905. To ensure that pieces with amean specific gravity are bonded together, a single piece of the nominal 2 in. thick lumber shall provide, at a minimum, t
31、he twopieces (lumber) necessary for each bonded specimen and a side-matched solid wood (control) specimen. An example of the shearspecimen-cutting pattern is shown in Fig. 1. Care shall be exercised to ensure the same annual ring orientation when bonding thelumber together into a bonded assembly.6.3
32、 The mating surfaces of the lumber used to prepare the bonded specimens shall be surfaced no more than 24 h prior tobonding. The adhesive preparation, spread rate, clamping pressure and clamping time shall follow the adhesive manufacturersrecommendations. The production conditions for the end-use pr
33、oducts shall also be considered (see 4.3).6.4 A minimum of 20 bonded specimens shall be prepared in accordance with Fig. 2. The bonded specimens will have athickness less than the specified 38 mm (1.5 in.) as described in Test Method D905 due to surfacing from nominal 2-in lumber.In addition, a mini
34、mum of 20 solid wood (without the bondline) control specimens side-matched with the bonded specimens shallbe prepared as shown in Fig. 1. The side-matched solid wood specimens shall be surfaced to the same thickness as the bondedspecimens. The bonded and matched solid wood control specimens shall be
35、 prepared as 20 pairs.6.5 A total of 10 pairs of bonded and matched solid wood control specimens shall be tested at ambient temperature and theremaining 10 pairs of bonded and matched solid wood control specimens shall be tested at the targeted elevated temperature.6.6 For specimens tested at the el
36、evated temperature, a hole shall be drilled through one lamination at a 90 angle to the bondlineand extending 0.6 mm (132 in.) past the bondline. The drilled hole shall allow the thermocouple wire casing to fit snugly insidethe hole (see Fig. 3), with the exposed portion of the thermocouple wire tou
37、ching the bondline of the bonded specimen or thegeometric center (shear plane) of the matched solid wood control specimen. The tip of the thermocouple wire shall have amaximum of 1 mm (0.040 in.) of insulation removed.NOTE 3Experience has shown that stripping the wire insulation approximately 12.7 m
38、m (0.5 in.), twisting the wires together, and cutting the exposedwire back to 1 mm (0.040 in.) gives consistent results. Damage-to or improper-removal-of thermocouple wire insulation increases the possibility ofinaccurate temperature readings in the oven. Prior to re-using thermocouple wire, it is t
39、o be re-tested to ensure that accurate temperature readings are beingprovided.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 fr
40、om the wood adherend so that the specimen weight reduction during 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 measured andrecorded, at the bondline, to the n
41、earest 0.25 mm (0.010 in.) to determine the shear area. Test specimens are to be kept in thedesiccator until just prior to testing in accordance with Section 7.7. Test Procedures7.1 Specimens at Ambient Temperature Condition:FIG. 2 Form and Dimensions of a Bonded SpecimenD7247 1737.1.1 Asample set c
42、onsisting of 10 solid wood control specimens and 10 bonded specimens shall be tested at ambient laboratoryconditions in accordance with the procedures outlined in Test Method D905. Loads shall be applied with a continuous motion ofthe movable head at a rate of 5 mm (0.20 in.)/min until failure. The
43、ultimate load shall be recorded along with an estimation ofwood failure (to the nearest 5 %) in accordance with Practice D5266.7.2 Specimens at Elevated Temperature Condition:7.2.1 The oven shall be preheated to the targeted temperature using a thermocouple to monitor the interior oven temperature(s
44、ee Note 5 for additional information). The oven air temperature shall be held at the desired level for a sufficient amount of timeto heat all of the components of the oven to the targeted temperature.7.2.2 Only one specimen, either one solid wood control specimen or one side-matched bonded specimen,
45、 shall be placed in theoven at a time. A thermocouple wire shall be placed into the specimen as described in 6.6 and shown in Fig. 3. The drilled holeshall be backfilled, if necessary, with glass insulation, high temperature silicon, or a similar protective barrier. The backfillmaterials shall be al
46、lowed to cure according to the manufacturers recommendations prior to testing. The starting time andspecimen oven-dry weight, after the backfill materials are cured, as applicable, shall be recorded.7.2.3 The bondline temperature of the bonded specimen or the temperature at the shear plane of the ma
47、tched solid wood controlspecimen shall be monitored. Because of the insulating nature of wood, the bondline temperature may be different from the ovenair temperature and thus the targeted temperature. Therefore, as the specimen approaches the targeted temperature, the rate ofheating shall be slowed
48、to a rate that can be easily controlled either manually or by using a proportional temperature controllerwith an integral and derivative (PID) control algorithm. The amount of time for the specimen to reach the targeted temperatureshall not be less than 30 min. nor more than 90 min.NOTE 5When a manu
49、ally controlled oven is used, previous studies have shown that for a targeted temperature of 232C (450F), the heat should beturned down when the interior temperatures of the specimens reach approximately 210C (410F). The bondline temperature will continue to rise, butthe rate of increase will decrease. As the rate of temperature rise decreases, heat can be re-introduced, if necessary, to attain the targeted bondlinetemperature. Practice runs with “dummy” specimens are recommended before the collection of actual data. The use of a PID device may help the
