1、Designation: D 4896 01Standard 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, the year of last revis
2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONThe true strength of an adhesive is a material property independent of the joint geometry, adherendproperties, and load, and is
3、 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 shear strength, however, cannot be easily determined using single-lap specimens.Many factors affect the app
4、arent 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 usually controlled by the tensile stress in the adhesive, and not by the shearstress. The factors that contro
5、l 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, and the changes that take place in the specimen due to adhesive cure and theenvironment. Similarly thes
6、e 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 laboratory specimens may vary widely from the true shear- or tensile-strength values needed todetermine all
7、owable 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 laboratory test specimens; to foster the acceptableuses of the widely used thin-adherend single-lap-joint
8、 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 adhesive joint specimens.1.2 The discussion focuses on shear strength as measuredwith small thin-adherend
9、, 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 Standards:D 896 Te
10、st Method for Resistance of Adhesive Bonds toChemical Reagents2D 906 Test Method for Strength Properties of Adhesives inPlywood Type Construction in Shear by Tension Loading2D 907 Terminology of Adhesives2D 1002 Test Method for Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded Metal Spec
11、imens by Ten-sion Loading (Metal-to-Metal)2D 1144 Practice for Determining Strength Development ofAdhesive Bonds2D 1151 Test Method for Effect of Moisture and Temperatureon Adhesive Bonds2D 1183 Test Methods for Resistance of Adhesives to CyclicLaboratory Aging Conditions2D 1780 Practice for Conduct
12、ing Creep Tests of Metal-to-Metal Adhesives2D 2294 Test Method for Creep Properties of Adhesives inShear by Tension Loading (Metal-to-Metal)2D 2295 Test Method for Strength Properties of Adhesives inShear by Tension Loading at Elevated Temperatures(Metal-to-Metal)2D 2339 Test Method for Strength Pro
13、perties of Adhesives inTwo-Ply Wood Construction in Shear by Tension Loading2D 2919 Test Method for Determining Durability of Adhe-sive Joints Stressed in Shear by Tension Loading21This guide is under the jurisdiction of ASTM Committee D14 on Adhesives andis the direct responsibility of Subcommittee
14、 D14.80 on Metal Bonding Adhesives.Current edition approved March 10, 2001. Published May 2001. Originallypublished as D 4896 89. Last previous edition D 4896 95.2Annual Book of ASTM Standards, Vol 15.06.1Copyright ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.D 3163 T
15、est Method for Determining Strength of Adhe-sively Bonded Rigid Plastic Lap-Shear Joints in Shear byTension Loading2D 3164 Test Method for Determining the Strength of Ad-hesively Bonded Plastic Lap-Shear Sandwich Joints inShear by Tension Loading2D 3165 Test Method for Strength Properties of Adhesiv
16、es inShear by Tension Loading of Single-Lap-Joint LaminatedAssemblies2D 3166 Test Method for Fatigue Properties of Adhesives inShear by Tension Loading (Metal/Metal)2D 3434 Practice for Multiple-Cycle Accelerated Aging Test(Automatic Boil Test) for Exterior Wet Use Wood Adhe-sives2D 3528 Test Method
17、 for Strength Properties of Double LapShear Adhesive Joints by Tension Loading2D 3632 Practice for Accelerated Aging of Adhesive Jointsby the Oxygen-Pressure Method2D 3983 Test Method for Measuring Strength and ShearModulus of Nonrigid Adhesives by the Thick AdherendTensile Lap Specimen2D 4027 Test
18、Method for Measuring Shear Properties ofStructural Adhesives by the Modified-Rail Test2D 4562 Test Method for Shear Strength of Adhesives UsingPin-and-Collar Specimen2D 5868 Test Method for Lap Shear Adhesion for FiberReinforced Plastic (FRP) Bonding2E 6 Terminology Relating to Methods of Mechanical
19、 Test-ing3E 229 Test Method for Shear Strength and Shear Modulusof Structural Adhesives23. Terminology3.1 Definitions:3.1.1 The following terms are defined in accordance withTerminologies D 907 and E 6.3.2 creepthe time-dependent increase in strain in a solidresulting from force.3.3 shear strength t
20、he maximum shear stress which amaterial is capable of sustaining. Shear strength is calculatedfrom 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
21、, in the size or shapeof a body referred to its original size or shape. Strain is anondimensional quantity, but is frequently expressed in inchesper inch, centimeters per centimeter, etc. (Refer to Terminol-ogy E 6 for specific notes.)3.4.1 linear (tensile or compressive) strainthe change perunit le
22、ngth due to force in an original linear dimension.3.4.2 shear strain the tangent of the 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
23、 a given plane throughthe point. Stress is expressed as force per unit of area(pounds-force 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 t
24、he cross section of the specimen.3.5.1 normal stress the stress component perpendicular tothe 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 stress normal stress due to for
25、ces directedaway from the plane on which they act.3.5.2 DiscussionIn single-lap specimen testing, 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, compressiv
26、e, and shear stress distributions, not justtensile stress.3.5.3 shear stress The stress component 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
27、low probabilityof mechanical failure within the design lifetime.3.6.1.1 DiscussionAllowable 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 environmentalef
28、fects, and safety.3.6.2 apparent shear strength(in testing a single-lapspecimen) the nominal 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 testin
29、g) the stress calcu-lated by simple elastic theory as the load applied to the jointdivided 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 stres
30、sesare denoted by tavgand savgrespectively. (See 5.3.1.1.) (Average stress is the same as the preferred but less commonterm, nominal stress, as defined in Terminology E 6.)3.6.4 cleavage stress(in adhesive testing) a term used todescribe the complex distribution of normal and shear stressespresent i
31、n an adhesive when a prying force is applied at oneend of a joint 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
32、 flexible adherend.3.6.6 single-lap specimen(in adhesive testing) 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 en
33、ds.NOTE 2In the past this specimen has been referred to commonly asthe tensile-shear- or the lap-shear-specimen. These names imply that thisis a shear dominated joint, and that the measured strength is the shear3Annual Book of ASTM Standards, Vol 03.01.D 48962strength of the adhesive. This is not tr
34、ue for most uses of such specimens.(An exception would be where the adhesive being evaluated is so low instrength 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 hi
35、gher thanaverage stress near a geometric discontinuity in a joint ormember (such as a notch, hole, void, or crack); 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 discontinuiti
36、es are the ends of the bondedadherends and the interfaces between the adhesive and adher-ends.3.6.8 stress concentration 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 doe
37、s not bend significantlywhen a load is applied, resulting in relatively lower tension/normal stress at the ends of 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 a
38、dherend for a typical epoxyadhesive and steel joint is at least 0.25 in. (6.36 mm) thickwhen the overlap is 0.50 in. (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
39、thin adherend(in adhesive testing) an adherendused in a single-lap specimen that bends significantly, causingsignificant 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 DiscussionT
40、he bending of the adherends, thetension-normal stresses, and the nonuniform stress distribu-tions are continuous functions 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 rat
41、io of less than 1:5 is a reasonableapproximation of a thin adherend for epoxy-steel joints (1 and2).3.6.11 true shear 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,
42、 practical, andeasy to make. They are the most widely used specimens fordevelopment, evaluation, and comparative studies 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 t
43、rue shear strength ofadhesives. These methods eliminate or minimize many of thedeficiencies of the thin-adherend single-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 Pract
44、ices 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 3528, 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
45、Single-LapSpecimen Test Results5.1 The true shear strength of an adhesive can be deter-mined only if normal stresses 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
46、standard test specimens. Inmost cases the tensile stress in the adhesive controls jointfailure. As a consequence the 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 thej
47、oint, the modulus of the adherends, and temperature ormoisture shifts after cure, all affect the magnitude of thestresses 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
48、 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 Factor
49、s Affecting Apparent Shear Strength:5.3.1 Specimen geometry, material properties, and load arefactors affecting apparent shear strength. The shear and normalstresses at any point in a single-lap specimen are describedmathematically in the classic linear-elastic analysis of Golandand Reissner (3). Modern finite element analysis has proventhe Goland and Reissner analysis to be accurate except at thevery ends of the overlap (1). Both the Goland and Reissner andfinite element analyses show that both the normal and shearstress concentration factors increase tow
