ASTM_D_7998_-_19.pdf

Designation:D799819Standard Test Method forMeasuring the Effect of Temperature on the CohesiveStrength Development of Adhesives using Lap Shear Bondsunder Tensile Loading1This standard is issued under the fixed designation D7998;the number immediately following the designation indicates the year oforiginal adoption or,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 test method concerns bonding and testing of woodadhesives and related adhesives using small scale tensilelap-shear samples in a manner that emphasizes transientcohesive strength as a function of bonding time and tempera-ture.1.2 Use of thin adherends enables bondlines to be rapidlyheated to elevated temperatures and maintained at thosetemperatures for a range of times at a controlled pressurebefore testing.1.3 Optional rapid forced air cooling of bonds after pressingand immediately before testing enables the effect of testingtemperature on transient strength to be evaluated.1.4 Bond overlap distance is specified to ensure that failureoccurs in the bondline rather than in unbonded portions ofadherend strips,and also to minimize the effect of shear stressnon-uniformity along the overlap during tensile testing.1.5 Standard wood or alternative non-standard materialsmust be of specified high quality and uniformity of structureand dimension to minimize variability of bonding and maxi-mize stress transfer into the bonds during testing.1.6 The effect of wood variability and type,or of theproperties of alternative non-wood materials,on bond strengthdevelopment may be explored using the method.1.7 Optional hermetic sealing of bond overlaps during theirheated pressing enables the effect of moisture on bonding to beevaluated.1.8 Thermal damage,either of pre-formed bonds or byprolonging bond forming times,may be evaluated as a functionof time and elevated temperature using this test method.1.9 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.10 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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.Some specific hazards statements are given in Section 10 onHazards.1.11 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D907 Terminology of AdhesivesE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 See Terminology D907 for other terms related to adhe-sives.3.2 Definitions of Terms Specific to This Standard:3.2.1 adherend strip,none of two adherend pieces thatconstitute a test specimen.3.3 adhesive spread rate,nthe mass of adhesive appliedper unit surface area of the overlap region of the adherend.3.4 contact heating,nthe transfer of heat energy to the testspecimen by the application of precisely temperature-controlled heads pressing on the test specimens surfaces withcontrolled force.3.5 forced air cooling,nthe rapid cooling of the overlapregion of a test specimen after bonding at elevated temperature1This test method is under the jurisdiction of ASTM Committee D14 onAdhesives and is the direct responsibility of Subcommittee D14.30 on WoodAdhesives.Current edition approved June 1,2019.Published July 2019.Originally approvedin 2015.Last previous edition approved in 2015 as D7998 15.DOI:10.1520/D7998-19.2For referenced ASTM standards,visit the ASTM website,www.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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 by the controlled application of air jets onto both external facesof the overlap portion of the specimen.3.6 test specimen,nthe lap shear sample made up of anadhesive between two pieces of adherend.3.7 thermal damage,nthe decrease in measured bondstrength due to exposure to a specified elevated temperature fora specified time.3.8 transient bond strength,nthe strength of a partiallyforme