1、Designation: D 7247 07aStandard Test Method forEvaluating the Shear Strength of Adhesive Bonds inLaminated Wood Products at Elevated Temperatures1This standard is issued under the fixed designation D 7247; the number immediately following the designation indicates the year oforiginal adoption or, in
2、 the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This standard describes a test method for evaluating thecomparative shear strength
3、 of 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 describe
4、d in 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
5、Method D 905. 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
6、 of fire performance onfire-rated laminated wood products or assemblies is beyond thescope of this test method.1.4 While it is preferable to use solid wood specimens asdescribed in Section 6 as the control, structural compositelumber products as defined in Specification D 5456 shall bepermitted for
7、use provided they are matched with the bondedspecimens in accordance with Section 6 and the ignitiontemperature is not significantly lower than solid wood of thesame species.1.5 The exact formulation of adhesive supplied to themanufacturer of laminated wood products shall be evaluated.Modifications
8、to the adhesive formulation require a separateevaluation unless approved by the manufacturer 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 Th
9、is standard does not purport to address all of thesafety concerns, such as the fire hazard, 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. Refer
10、enced Documents2.1 ASTM Standards:2D 905 Test Method for Strength Properties of AdhesiveBonds in Shear by Compression LoadingD 907 Terminology of AdhesivesD 2395 Test Methods for Specific Gravity of Wood andWood-Based MaterialsD 2915 Practice for Evaluating Allowable Properties forGrades of Structur
11、al LumberD 4933 Guide for Moisture Conditioning of Wood andWood-Based MaterialsD 5266 Practice for Estimating the Percentage of WoodFailure in Adhesive Bonded JointsD 5456 Specification for Evaluation of Structural Compos-ite Lumber Products2.2 Other Documents:ANSI/AITC A190.1 American National Stan
12、dard for WoodProducts Structural Glued Laminated Timber3ANSI/AF V # 0.3 (when V is greaterthan 0.3, use 0.3 in the calculation), andN = sample size for the solid wood control specimens atthe elevated temperature.NOTE 6The acceptance criteria for adhesive performance at elevatedtemperatures is to be
13、established by the manufacturer of the laminatedwood product, qualified agency, and code evaluation agency. The meanresidual shear strength ratio for the bonded specimens is recommended tobe equal to or higher than the lower 95 % confidence interval on the meanresidual shear strength ratio for the s
14、olid wood control specimens, RLC,ascalculated in accordance with Eq 3.9. Report9.1 The report shall include the following:9.1.1 Identification of the adhesive tested.9.1.2 Identification of the wood species used.9.1.3 Application and bonding conditions used in fabricat-ing the specimens.9.1.4 Condit
15、ioning procedure used for the specimens.9.1.5 Temperature and relative humidity in the test room.9.1.6 Time elapsed before the elevated temperature speci-men reached the targeted temperature after being placed in theoven.9.1.7 One plot of specimen temperature versus time in oven,at a minimum of 5 in
16、tervals.9.1.8 One plot of oven temperature versus time, at aminimum of 5 intervals.9.1.9 Amount of time the elevated temperature specimenwas held at the targeted temperature.9.1.10 Specimen weight and specific gravity prior to andafter Section 7 test procedures. Average weight loss ratio foreach tes
17、t condition.D 7247 07a49.1.11 Shear strength and percentages of wood failure foreach specimen. Note the presence and extent of charring ofadhesive or wood, or both.9.1.12 The average shear strength, average percent woodfailure, and mean residual strength (if applicable) for each testcondition.9.1.13
18、 The calculated residual shear strength ratios (R) forthe bonded and solid wood control specimens, and the calcu-lated lower 95 % confidence interval on the mean residualshear strength ratio (RLC) for the solid wood control speci-mens.10. Precision and Bias10.1 The precision and bias of the procedur
19、e in this testmethod for measuring the shear strength of adhesives atelevated temperature is being determined and it is expected thatresults will be available by January 2008.11. Keywords11.1 bonded; bondline; laminated; residual shear strengthratioAPPENDIX(Nonmandatory Information)X1. COMMENTARYX1.
20、1 The objective of any structural adhesive is to transferloads between substrates when exposed to specific serviceenvironments and to provide an adhesive bond equal to orstronger than the cohesive strength of the substrates bondedtogether. Many different factors influence the determination ofthe she
21、ar strength of an adhesive bond, especially at elevatedtemperatures. For example, the strength of the wood, the sheartool design, the rate of loading, and the rate of temperature gainof an individual specimen may all bias the results to a certainextent. Therefore, it cannot be assumed that this test
22、 methodmeasures the true shear strength of the adhesive. Instead, thesmall-scale shear test method is used as a relative measure ofadhesive bond strength relative to the longitudinal shearstrength of solid wood. Solid wood has code-recognized fireperformance and is commonly used as a benchmark by fi
23、refighters.X1.2 The shear strength of structural wood members isaffected by the temperature of the wood in service. Shearstrength is increased as the temperature cools below the normaltemperature range found in most buildings. Conversely, theshear strength decreases as temperature increases. For ex-
24、ample, the NDS calls for a 30 % reduction in the tabulatedshear strength when the temperature of a structural member issustained at 65C (150F). Based on the Wood Handbook, thethermal degradation of wood occurs in three phases; (a)dehydration or loss of water vapor (up to 150C or 302F), (b)noncombust
25、ible degradation where gaseous vapors are slowlygiven off and char begins to form (100 to 250C or 212 to482F), and (c) combustible degradation where volatile organiccompounds are emitted, which may or may not flame, depend-ing on oven conditions (270 to 470C or 518 to 878F). Thistest method can be u
26、sed to evaluate the condition at the upperend of the second phase of wood degradation, above the hotpress temperatures typically used in production of woodcomposites (149 to 204C or 300 to 400F), yet below theunpiloted ignition temperature of the wood adherend (270 to470C or 518 to 878F). Wood ignit
27、ion is the decomposition(pyrolysis) of material into volatiles and a char residue. Afterpyrolysis, the char may disintegrate by glowing or smoldering;the volatiles mix with oxygen in the air and may undergoflaming combustion. The temperature at which the woodignites is a function of the wood moistur
28、e content and species,the temperature and heat flow within the oven, and the time ofexposure at an elevated temperature. This test method does notevaluate a number of factors pertaining to a flashover fire on afull-scale assembly, such as size and shape of the floor joist,joist depth and spacing, pi
29、loted versus unpiloted ignitiontemperature, and assembly protection, etc.X1.3 It is the prerogative of the product standard, manu-facturer of the laminated wood product, qualified agency,and/or code evaluation agency, when adopting this test method,to select a combination of test temperature and exp
30、osureduration (or a range of shear strength reductions) for a specificproduct and its end-use applications. The minimum exposureof 10 min. is specified to ensure the temperature uniformity atthe bondline of the bonded specimen. Limited test data used forthe development of this standard is documented
31、.55Yeh, B. and Brooks, R. “Evaluation of Adhesive Performance at ElevatedTemperatures for Engineered Wood Products,” Proceedings: World Conference onTimber Engineering, August 610, 2006. Portland, OR.D 7247 07a5ASTM International takes no position respecting the validity of any patent rights asserte
32、d in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by th
33、e responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive
34、careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM Internat
35、ional, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 7247 07a6
