1、Designation: D 4896 01 (Reapproved 2008)e1Standard Guide forUse of Adhesive-Bonded Single Lap-Joint Specimen TestResults1This standard is issued under the fixed designation D 4896; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e 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.e1NOTEThe units statement in subsection 1.2 was corrected editorially in April 2008.INTRODUCTIONThe true strength of an
3、 adhesive is a material property independent of the joint geometry, adherendproperties, and load, and is a good starting point for determining an allowable design stress.Allowablestresses in shear and tension are needed to design safe, efficient, adhesively bonded joints andstructures. The true shea
4、r strength, however, cannot be easily determined using single-lap specimens.Many factors affect the apparent shear strength of an adhesive when measured with a smalllaboratory specimen, and in particular, with a single-lap specimen. For example, the failure of a typicalsingle-lap specimen, is usuall
5、y controlled by the tensile stress in the adhesive, and not by the shearstress. The factors that control the tensile stress in lap-joint specimen, and thus, the apparent shearstrength are the size and shape of the specimen, the properties of the adherends, the presence ofinternal stresses or flaws,
6、and the changes that take place in the specimen due to adhesive cure and theenvironment. Similarly these factors affect the apparent tensile strength of an adhesive in butt-joint testspecimens.Due to the effects of these factors, the apparent shear strength obtained through measurements onsmall labo
7、ratory specimens may vary widely from the true shear- or tensile-strength values needed todetermine allowable shear and tension design stresses.The objectives of this guide are: to develop an appreciation of the factors that influence strength andother stress measurements that are made with small la
8、boratory test specimens; to foster the acceptableuses of the widely used thin-adherend single-lap-joint test; and, specifically, to prevent misuse of thetest results.1. Scope1.1 This guide is directed toward the safe and appropriateuse of strength values obtained from test methods usingsingle-lap ad
9、hesive joint specimens.1.2 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 The discussion focuses on shear strength as measuredwith s
10、mall thin-adherend, single-lap specimens. Many factors,however, apply to shear modulus, tensile strength, and tensilemodulus measured by small laboratory specimens in general.This discussion is limited to single-lap specimens and shearstrength only for simplification.2. Referenced Documents2.1 ASTM
11、Standards:2D 896 Practice for Resistance ofAdhesive Bonds to Chemi-cal ReagentsD 906 Test Method for Strength Properties of Adhesives inPlywood Type Construction in Shear by Tension LoadingD 907 Terminology of AdhesivesD 1002 Test Method for Apparent Shear Strength of Single-Lap-Joint Adhesively Bon
12、ded Metal Specimens by Ten-sion Loading (Metal-to-Metal)D 1144 Practice for Determining Strength Development ofAdhesive BondsD 1151 Practice for Effect of Moisture and Temperature onAdhesive Bonds1This guide is under the jurisdiction ofASTM Committee D14 onAdhesives andis the direct responsibility o
13、f Subcommittee D14.80 on Metal Bonding Adhesives.Current edition approved April 1, 2008. Published April 2008. Originallyapproved in 1989. Last previous edition approved in 2001 as D 4896 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serv
14、iceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.D 1183 Practices for Resistance of Adhesives to CyclicL
15、aboratory Aging ConditionsD 1780 Practice for Conducting Creep Tests of Metal-to-Metal AdhesivesD 2294 Test Method for Creep Properties of Adhesives inShear by Tension Loading (Metal-to-Metal)D 2295 Test Method for Strength Properties ofAdhesives inShear by Tension Loading at Elevated Temperatures(M
16、etal-to-Metal)D 2339 Test Method for Strength Properties ofAdhesives inTwo-Ply Wood Construction in Shear by Tension LoadingD 2919 Test Method for Determining Durability of Adhe-sive Joints Stressed in Shear by Tension LoadingD 3163 Test Method for Determining Strength of Adhe-sively Bonded Rigid Pl
17、astic Lap-Shear Joints in Shear byTension LoadingD 3164 Test Method for Strength Properties of AdhesivelyBonded Plastic Lap-Shear Sandwich Joints in Shear byTension LoadingD 3165 Test Method for Strength Properties ofAdhesives inShear by Tension Loading of Single-Lap-Joint LaminatedAssembliesD 3166
18、Test Method for Fatigue Properties of Adhesives inShear by Tension Loading (Metal/Metal)D 3434 Test Method for Multiple-Cycle Accelerated AgingTest (Automatic Boil Test) for Exterior Wet Use WoodAdhesivesD 3528 Test Method for Strength Properties of Double LapShear Adhesive Joints by Tension Loading
19、D 3632 Test Method for Accelerated Aging of AdhesiveJoints by the Oxygen-Pressure MethodD 3983 Test Method for Measuring Strength and ShearModulus of Nonrigid Adhesives by the Thick-AdherendTensile-Lap SpecimenD 4027 Test Method for Measuring Shear Properties ofStructural Adhesives by the Modified-R
20、ail TestD 4562 Test Method for Shear Strength of Adhesives UsingPin-and-Collar SpecimenD 5868 Test Method for Lap Shear Adhesion for FiberReinforced Plastic (FRP) BondingE6 Terminology Relating to Methods of Mechanical Test-ingE 229 Test Method for Shear Strength and Shear Modulusof Structural Adhes
21、ives33. Terminology3.1 Definitions:3.1.1 The following terms are defined in accordance withTerminologies D 907 and E6.3.2 creepthe time-dependent increase in strain in a solidresulting from force.3.3 shear strengththe maximum shear stress which amaterial is capable of sustaining. Shear strength is c
22、alculatedfrom the maximum load during a shear or torsion test and isbased on the original dimensions of the cross section of thespecimen. (See apparent and true shear strength).3.4 strainthe unit change due to force, in the size or shapeof a body referred to its original size or shape. Strain is ano
23、ndimensional quantity, but is frequently expressed in inchesper inch, centimeters per centimeter, etc. (Refer to Terminol-ogy E6for specific notes.)3.4.1 linear (tensile or compressive) strainthe change perunit length due to force in an original linear dimension.3.4.2 shear strainthe tangent of the
24、angular change, dueto force, between two lines originally perpendicular to eachother through a point in a body.3.5 stressthe intensity at a point in a body of the internalforces or components of force that act on a given plane throughthe point. Stress is expressed as force per unit of area(pounds-fo
25、rce per square inch, newtons per square millimetre,etc.).NOTE 1As used in tension, compression, or shear tests prescribed inproduct specifications, stress is calculated on the basis of the originaldimensions of the cross section of the specimen.3.5.1 normal stressthe stress component perpendicular t
26、othe plane on which the forces act. Normal stress may be either:3.5.1.1 compressive stressnormal stress due to forcesdirected toward the plane on which they act, or3.5.1.2 tensile stressnormal stress due to forces directedaway from the plane on which they act.3.5.2 DiscussionIn single-lap specimen t
27、esting, the planeon which the forces act is the bondline. Tensile stress issometimes used interchangeably, although incorrectly, withpeel or cleavage stress. Peel and cleavage involve complextensile, compressive, and shear stress distributions, not justtensile stress.3.5.3 shear stressthe stress com
28、ponent tangential to theplane on which the forces act.3.6 Definitions of Terms Specific to This Standard:3.6.1 allowable design stressa stress to which a materialcan be subjected under service conditions with low probabilityof mechanical failure within the design lifetime.3.6.1.1 DiscussionAllowable
29、 design stress is obtainedusually by multiplying the true shear strength of the material(or close approximation thereof) by various adjustment factorsfor manufacturing quality control, load and environmentaleffects, and safety.3.6.2 apparent shear strength(in testing a single-lapspecimen) the nomina
30、l shear stress at failure without regard forthe effects of geometric and material effects on the nominalshear stress. Often called the lap-shear or tensile-shearstrength.3.6.3 average stress(in adhesive testing) the stress calcu-lated by simple elastic theory as the load applied to the jointdivided
31、by the bond area without taking into account the effectson the stress produced by geometric discontinuities such asholes, fillets, grooves, inclusions, etc.3.6.3.1 DiscussionThe average shear and tensile stressesare denoted by tavgand savgrespectively. (See 5.3.1.) (Averagestress is the same as the
32、preferred but less common term,nominal stress, as defined in Terminology E6.)3.6.4 cleavage stress(in adhesive testing) a term used todescribe the complex distribution of normal and shear stresses3Withdrawn.D 4896 01 (2008)e12present in an adhesive when a prying force is applied at oneend of a joint
33、 between two rigid adherends.3.6.5 peel stress(in adhesive testing) a term used todescribe the complex distribution of normal and shear stressespresent in an adhesive when a flexible adherend is strippedfrom a rigid adherend or another flexible adherend.3.6.6 single-lap specimen(in adhesive testing)
34、 a specimenmade by bonding the overlapped edges of two sheets or stripsof material, or by grooving a laminated assembly, as shown inTest Methods D 2339 and D 3165. In testing, a single-lapspecimen is usually loaded in tension at the ends.NOTE 2In the past this specimen has been referred to commonly
35、asthe tensile-shear- or the lap-shear-specimen. These names imply that thisis a shear dominated joint, and that the measured strength is the shearstrength of the adhesive. This is not true for most uses of such specimens.(An exception would be where the adhesive being evaluated is so low instrength
36、as not to induce any bending in the adherends.) It is recom-mended that, henceforth, this specimen be referred to as a single-lapspecimen.3.6.7 stress concentrationa localized area of higher thanaverage stress near a geometric discontinuity in a joint ormember (such as a notch, hole, void, or crack)
37、; or near amaterial discontinuity (such as a bonded joint or weld) whenthe joint or member is under load.3.6.7.1 DiscussionIn adhesive testing, the most commonand important discontinuities are the ends of the bondedadherends and the interfaces between the adhesive and adher-ends.3.6.8 stress concent
38、ration factorthe ratio of the stress at apoint in a stress concentration to the average stress.3.6.9 thick adherend(in adhesive testing) an adherendused in a single-lap specimen that does not bend significantlywhen a load is applied, resulting in relatively lower tension/normal stress at the ends of
39、 the overlap; and, more uniformnormal and shear stress distributions in the adhesive comparedto a joint made with thin adherends and placed under the sameload.3.6.9.1 DiscussionA thick adherend for a typical epoxyadhesive and steel joint is at least 0.25 in. (6.36 mm) thickwhen the overlap is 0.50 i
40、n. (12.7 mm), based on finite elementanalysis and mechanical tests (1 and 2).4Objective criteria fordetermining whether or not an adherend is thick are given inTest Method D 3983.3.6.10 thin adherend(in adhesive testing) an adherendused in a single-lap specimen that bends significantly, causingsigni
41、ficant tension/normal stresses in the adhesive at the endsof the overlap and nonuniform shear and normal stress distri-butions in the adhesive when a load is applied.3.6.10.1 DiscussionThe bending of the adherends, thetension-normal stresses, and the nonuniform stress distribu-tions are continuous f
42、unctions of the adhesive modulus andthickness, the adherend modulus, and the joint overlap lengthas described more fully in Test Method D 3983. An adherendthickness to overlap length ratio of less than 1:5 is a reasonableapproximation of a thin adherend for epoxy-steel joints (1 and2).3.6.11 true sh
43、ear strengththe maximum uniform shearstress which a material is capable of sustaining in the absenceof all normal stresses.4. Significance and Use4.1 Single-lap specimens are economical, practical, andeasy to make. They are the most widely used specimens fordevelopment, evaluation, and comparative s
44、tudies involvingadhesives and bonded products, including manufacturing qual-ity control.4.2 Special specimens and test methods have been devel-oped that yield accurate estimates of the true shear strength ofadhesives. These methods eliminate or minimize many of thedeficiencies of the thin-adherend s
45、ingle-lap specimens, but aremore difficult to make and test. (See Test Methods D 3983,D 4027, D 4562, and E 229.)4.3 The misuse of strength values obtained from such TestMethods or Practices as D 906, D 1002, D 1144, D 1151,D 1183, D 1780, D 2294, D 2295, D 2339, D 3163, D 3164,D 3165, D 3434, D 352
46、8, D 3632, and D 5868, as allowabledesign-stress values for structural joints could lead to productfailure, property damage, and human injury.5. Considerations for the Analysis of Small Single-LapSpecimen Test Results5.1 The true shear strength of an adhesive can be deter-mined only if normal stress
47、es are entirely absent. Theseconditions can be approached under special conditions, but notin single-lap specimens made with the thin adherends normallyused in manufacturing and in most standard test specimens. Inmost cases the tensile stress in the adhesive controls jointfailure. As a consequence t
48、he single-lap specimen strength isunrelated to, and an unreliable measure of, the true shearstrength of an adhesive (1 and 2).5.2 Changes in adhesive volume during cure, the size of thejoint, the modulus of the adherends, and temperature ormoisture shifts after cure, all affect the magnitude of thes
49、tresses imposed on an adhesive in service. The thermalconductivity and permeability of the adherends affect theextent of thermal or moisture softening and the rate of chemicaldegradation of the adhesive in service. Therefore, in addition tothe problems stated in 5.1, the average stress at failure of smallsingle-lap specimens after a given exposure is an unreliablemeasure of an adhesives environmental resistance in any otherjoint, especially a much larger structural joint.5.3 Factors Affecting Apparent Shear Strength:5.3.1 Specimen geometry, material pro
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