1、Designation: D4896 01 (Reapproved 2016)Standard Guide forUse of Adhesive-Bonded Single Lap-Joint Specimen TestResults1This standard is issued under the fixed designation D4896; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar 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.INTRODUCTIONThe true strength of an adhesive is a material property independent of the joint geometry, adherendproperties, a
3、nd 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 shear strength, however, cannot be easily determined using single-lap specimens.Many factors
4、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 usually controlled by the tensile stress in the adhesive, and not by the shearstress. The facto
5、rs 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, and the changes that take place in the specimen due to adhesive cure and theenvironment.
6、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 laboratory specimens may vary widely from the true shear- or tensile-strength values needed t
7、odetermine 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 laboratory test specimens; to foster the acceptableuses of the widely used thin-adherend si
8、ngle-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 adhesive joint specimens.1.2 The values stated in inch-pound units are to be regardedas sta
9、ndard. 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 small thin-adherend, single-lap specimens. Many factors,however, apply to shear modulus, t
10、ensile 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:2D896 Practice for Resistance of Adhesive Bonds to Chemi-cal ReagentsD906 Test
11、Method for Strength Properties of Adhesives inPlywood Type Construction in Shear by Tension LoadingD907 Terminology of AdhesivesD1002 Test Method for Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded Metal Specimens by Ten-sion Loading (Metal-to-Metal)D1144 Practice for Determining Stren
12、gth Development ofAdhesive BondsD1151 Practice for Effect of Moisture and Temperature onAdhesive BondsD1183 Practices for Resistance of Adhesives to Cyclic1This guide is under the jurisdiction ofASTM Committee D14 on Adhesives andis the direct responsibility of Subcommittee D14.80 on Metal Bonding A
13、dhesives.Current edition approved May 1, 2016. Published May 2016. Originallyapproved in 1989. Last previous edition approved in 2008 as D4896 01 (2008)1.DOI: 10.1520/D4896-01R16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org.
14、 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 States1Laboratory Aging ConditionsD1780 Practice for Conducting Creep Tests
15、 of Metal-to-Metal AdhesivesD2294 Test Method for Creep Properties of Adhesives inShear by Tension Loading (Metal-to-Metal)D2295 Test Method for Strength Properties of Adhesives inShear by Tension Loading at Elevated Temperatures(Metal-to-Metal)D2339 Test Method for Strength Properties of Adhesives
16、inTwo-Ply Wood Construction in Shear by Tension LoadingD2919 Test Method for Determining Durability of AdhesiveJoints Stressed in Shear by Tension LoadingD3163 Test Method for Determining Strength of AdhesivelyBonded Rigid Plastic Lap-Shear Joints in Shear by Ten-sion LoadingD3164 Test Method for St
17、rength Properties of AdhesivelyBonded Plastic Lap-Shear Sandwich Joints in Shear byTension LoadingD3165 Test Method for Strength Properties of Adhesives inShear by Tension Loading of Single-Lap-Joint LaminatedAssembliesD3166 Test Method for Fatigue Properties of Adhesives inShear by Tension Loading
18、(Metal/Metal)D3434 Test Method for Multiple-Cycle Accelerated AgingTest (Automatic Boil Test) for Exterior Wet Use WoodAdhesivesD3528 Test Method for Strength Properties of Double LapShear Adhesive Joints by Tension LoadingD3632 Test Method for Accelerated Aging of AdhesiveJoints by the Oxygen-Press
19、ure MethodD3983 Test Method for Measuring Strength and ShearModulus of Nonrigid Adhesives by the Thick-AdherendTensile-Lap SpecimenD4027 Test Method for Measuring Shear Properties ofStructural Adhesives by the Modified-Rail TestD4562 Test Method for Shear Strength of Adhesives UsingPin-and-Collar Sp
20、ecimenD5868 Test Method for Lap Shear Adhesion for FiberReinforced Plastic (FRP) BondingE6 Terminology Relating to Methods of Mechanical TestingE229 Test Method for Shear Strength and Shear Modulus ofStructural Adhesives (Withdrawn 2003)33. Terminology3.1 Definitions:3.1.1 The following terms are de
21、fined in accordance withTerminologies D907 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 calculatedfrom the maximum load during a shear or torsion test and is
22、based 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 anondimensional quantity, but is frequently expressed in inchesper inch
23、, centimeters per centimeter, etc. (Refer to Terminol-ogy E6 for 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 angular change, due toforce, between two lines originally perpendic
24、ular to each otherthrough 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-force per square inch, newtons per square millimetre,etc.).NOTE 1As u
25、sed 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 tothe plane on which the forces act. Normal stress may be either:3.5
26、.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.3.5.1.2.1 DiscussionIn single-lap specimen testing, theplane on which the forces act is the bondline. Tensi
27、le stress issometimes used interchangeably, although incorrectly, withpeel or cleavage stress. Peel and cleavage involve complextensile, compressive, and shear stress distributions, not justtensile stress.3.5.2 shear stressthe stress component tangential to theplane on which the forces act.3.6 Defin
28、itions 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 design stress is obtainedusually by multiplying the true shear
29、 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 nominal shear stress at failure without regard forthe effects of geom
30、etric 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 by the bond area without taking into account the effectson the
31、stress produced by geometric discontinuities such asholes, fillets, grooves, inclusions, etc.3.6.3.1 DiscussionThe average shear and tensile stressesare denoted by avgand avgrespectively. (See 5.3.1.) (Averagestress is the same as the preferred but less common term,nominal stress, as defined in Term
32、inology E6.)3.6.4 cleavage stress(in adhesive testing) a term used todescribe the complex distribution of normal and shear stresses3The last approved version of this historical standard is referenced onwww.astm.org.D4896 01 (2016)2present in an adhesive when a prying force is applied at oneend of a
33、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 flexible adherend.3.6.6 single-lap specimen(in adhesive tes
34、ting) a specimenmade by bonding the overlapped edges of two sheets or stripsof material, or by grooving a laminated assembly, as shown inTest Methods D2339 and D3165. In testing, a single-lapspecimen is usually loaded in tension at the ends.NOTE 2In the past this specimen has been referred to common
35、ly 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 instreng
36、th 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 cra
37、ck); 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 conc
38、entration 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
39、 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 adherend for a typical epoxyadhesive and steel joint is at least 0.25 in. (6.36 mm) thickwhen the overlap is 0.5
40、0 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 D3983.3.6.10 thin adherend(in adhesive testing) an adherendused in a single-lap specimen that bends significantly, causingsig
41、nificant 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
42、 functions of the adhesive modulus andthickness, the adherend modulus, and the joint overlap lengthas described more fully in Test Method D3983. 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 s
43、hear 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
44、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 true shear strength ofadhesives. These methods eliminate or minimize many of thedeficiencies of the thin-adherend
45、single-lap specimens, but aremore difficult to make and test. (See Test Methods D3983,D4027, D4562, and E229.)4.3 The misuse of strength values obtained from such TestMethods or Practices as D906, D1002, D1144, D1151, D1183,D1780, D2294, D2295, D2339, D3163, D3164, D3165,D3434, D3528, D3632, and D58
46、68, as allowable design-stressvalues for structural joints could lead to product failure,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 stresses are entirely abs
47、ent. 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 the single-lap speci
48、men 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 thestresses imposed on
49、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 properties, and loa
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