ASTM D3983-98(2004)
(Test Method)Standard Test Method for Measuring Strength and Shear Modulus of Nonrigid Adhesives by the Thick-Adherend Tensile-Lap Specimen
Standard Test Method for Measuring Strength and Shear Modulus of Nonrigid Adhesives by the Thick-Adherend Tensile-Lap Specimen
SIGNIFICANCE AND USE
This test method is capable of providing shear modulus and shear strength values for adhesives with accuracy suitable for use by design engineers in predicting the characteristics of building assemblies bonded with nonrigid adhesives. Adhesive formulators will also find the method useful during the development of new adhesive systems. In general, the thick adherend lap-shear test is a useful tool in research during studies of both short- and long-term load-deformation properties of adhesives. This thick adherend lap-shear test yields a uniformity of stress distribution approaching that obtained in thin tubular butt joints subjected to torsion, which is considered to be a condition of pure shear.
The user is cautioned that pure shear strength cannot be obtained by this test method, because some tensile and compression stresses and stress concentrations are present in the joint. The estimate of shear strength by this test method will be conservative. If pure shear strength is demanded, then Test Method E 229 should be used.
SCOPE
1.1 This test method describes a method of measuring the shear modulus and rupture stress in shear of adhesives in bonded joints. The method employs lap-shear specimens with wood, metal, or composite adherends, with adhesives having shear moduli ranging up to 700 MPa (100 000 psi). This test method is suitable generally for joints in which the ratio of adherend tensile modulus to adhesive shear modulus is greater than 300 to 1. It is not suitable for adhesives that have a high shear modulus in the cured state and that also require elimination of volatile constituents during cure.
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation:D3983–98(Reapproved2004)
Standard Test Method for
Measuring Strength and Shear Modulus of Nonrigid
Adhesives by the Thick-Adherend Tensile-Lap Specimen
This standard is issued under the fixed designation D3983; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E104 Practice for Maintaining Constant Relative Humidity
by Means of Aqueous Solutions
1.1 This test method describes a method of measuring the
E229 Test Method for Shear Strength and Shear Modulus of
shear modulus and rupture stress in shear of adhesives in
Structural Adhesives
bonded joints. The method employs lap-shear specimens with
wood, metal, or composite adherends, with adhesives having
3. Terminology
shear moduli ranging up to 700 MPa (100 000 psi). This test
3.1 Definitions—For definitions of terms used in this test
method is suitable generally for joints in which the ratio of
method, refer to Terminologies E6 and D907.
adherend tensile modulus to adhesive shear modulus is greater
3.1.1 initial tangent modulus, n—the slope of the stress-
than 300 to 1. It is not suitable for adhesives that have a high
strain curve at the origin.
shear modulus in the cured state and that also require elimina-
3.1.2 nominal stress, n—the stress at a point calculated on
tion of volatile constituents during cure.
the net cross section by simple elastic theory without taking
1.2 The values stated in SI units are to be regarded as
into account the effect on the stress produced by discontinuities
standard. The values given in parentheses are for information
such as holes, grooves, fillets, etc.
only.
3.1.3 normal stress, n—the stress component perpendicular
1.3 This standard does not purport to address all of the
to a plane on which the forces act, that is, the plane of the
safety concerns, if any, associated with its use. It is the
bondline.
responsibility of the user of this standard to establish appro-
3.1.4 proportional limit, n—the maximum stress that a
priate safety and health practices and determine the applica-
material is capable of sustaining without significant deviation
bility of regulatory limitations prior to use.
from proportionality of stress to strain.
2. Referenced Documents 3.1.5 secant modulus, n—the slope of the secant drawn
2 from the origin to any specified point on the stress-strain curve.
2.1 ASTM Standards:
3.1.5.1 Discussion—Modulus is expressed in force per unit
D143 Test Methods for Small Clear Specimens of Timber
area (MPa, lb/in. , etc.).
D905 Test Method for Strength Properties of Adhesive
3.1.6 shear modulus, n—the ratio of shear stress to corre-
Bonds in Shear by Compression Loading
sponding shear strain below the proportional limit. (Compare
D907 Terminology of Adhesives
secant modulus.)
D1151 Practice for Effect of Moisture and Temperature on
3.1.6.1 Discussion—The term shear modulus is generally
Adhesive Bonds
reserved for materials that exhibit linear elastic behavior over
D2651 Guide for Preparation of Metal Surfaces for Adhe-
most of their stress-strain diagram. Many adhesives exhibit
sive Bonding
curvilinear or nonelastic behavior, or both, in which case some
E6 TerminologyRelatingtoMethodsofMechanicalTesting
other term, such as secant modulus, may be substituted.
E83 Practice for Verification and Classification of Exten-
3.1.7 shear strain, n—the tangent of the angular change,
someter Systems
due to force, between two lines originally perpendicular to
each other through a point in the body.
This test method is under the jurisdiction of ASTM Committee D14 on
3.1.7.1 Discussion—Shear strain equals adherend slip/
Adhesives and is the direct responsibility of Subcommittee D14.70 on Construction
adhesive layer thickness.
Adhesives.
Current edition approved April 1, 2004. Published April 2004. Originally
3.1.8 shear strength, n—in an adhesive joint, the maximum
approved in 1981. Last previous edition approved in 1998 as D3983 – 98. DOI:
average stress when a force is applied parallel to the joint.
10.1520/D3983-98R04.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Withdrawn. The last approved version of this historical standard is referenced
the ASTM website. on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D3983–98 (2004)
3.1.8.1 Discussion—In most adhesive test methods, the
shear strength is actually the maximum average stress at failure
of the specimen, not necessarily the true maximum stress in the
material.
3.1.9 shear stress, n—the stress component tangential to the
plane of which the forces act, that is, the plane of the bondline.
3.1.9.1 Discussion—Nominal shear stress equals load/bond
area.
3.1.10 strain, n—the unit change due to force, in the size or
shape of a body referred to its original size or shape.
3.1.11 stress, n—the intensity at a point in a body of the
internal forces or components of force that act on a given plane
through the point.
3.1.12 stress-strain diagram, n—a diagram in which corre-
sponding values of stress and strain are plotted against each
other. Values of stress are usually plotted as ordinates (verti-
cally) and values of strain as abscissas (horizontally).
3.2 Definitions of Terms Specific to This Standard:
3.2.1 load, n—the force applied to the specimen at any
given time.
3.2.2 load-slip diagram, n—adiagraminwhichcorrespond-
NOTE 1—The modulus is represented by the secant modulus line at
ing values of load and slip are plotted against each other.
some load P less than the load to cause failure.
Values of load are usually plotted as ordinates (vertically) and
FIG. 2 Load-Slip Diagram of Nonlinear Adhesive Under Cyclic
Low-Level Loading Showing Both Elastic and Viscoelastic
values of slip as abscissas (horizontally).
Recovering Diagrams
3.2.2.1 Discussion—Stress-strain behavior is commonly re-
corded in the form of a load-slip diagram. The difference
between the two is simply one of scale. Load is divided by
bond area to obtain stress and slip is divided by adhesive layer
thickness to obtain strain. Examples of various types of
load-slip diagrams and modulus are shown in Figs. 1-3.
3.2.3 rate of strain, n—rate of slip per unit adhesive
thickness.
NOTE 1—The modulus may be represented by the initial tangent, the
secant drawn to the ultimate load, or the secant drawn to some interme-
diate load.
FIG. 3 Load-Slip Diagram of Adhesive Loaded to Failure
3.2.4 slip, n—the relative collinear displacement of the
adherends on either side of the adhesive layer in the direction
of the applied load.
3.3 Symbols:Symbols:
3.3.1 c = half the overlap length = L/2, mm or in.
NOTE 1—Case load and unload diagrams and modulus line are congru-
ˆ
3.3.2 G = estimate of shear modulus of adhesive, MPa or
ent.
psi.
FIG. 1 Load-Slip Diagram of Linear Elastic Adhesive Under Cyclic
Low-Level Loading 3.3.3 G = shear modulus of adhesive, MPa or psi.
D3983–98 (2004)
FIG. 4 Incline Tension Grips with Specimen Bolted in Place Ready for Testing
3.3.4 E = tensile modulus of adherend, MPa or psi. uniformity of stress distribution approaching that obtained in
3.3.5 t = thickness of adherend, mm or in. thintubularbuttjointssubjectedtotorsion,whichisconsidered
3.3.6 h = thickness of adhesive, mm or in. to be a condition of pure shear.
3.3.7 P = failure load for the bond, N or lbf. 5.2 The user is cautioned that pure shear strength cannot be
max
3.3.8 L = overlap length, mm or in. obtained by this test method, because some tensile and com-
2 2
3.3.9 A = bond area, mm or in. pression stresses and stress concentrations are present in the
3.3.10 d = adherend slip at load equivalent to 0.1 P , joint. The estimate of shear strength by this test method will be
max
mm or in. conservative. If pure shear strength is demanded, then Test
3.3.11 t¯ = maximum nominal shear stress sustained by Method E229 should be used.
max
the bond, MPa or psi.
6. Equipment
4. Summary of Test Method
6.1 Test Machine— A tension test machine with electronic
load cell capacities of 0 to 100 and 0 to 1000 kg (0 to 200 and
4.1 Lap-shear specimens are prepared with the adhesive in
0 to 2000 lb) is satisfactory for this test method. The machine
question using selected adherends.The load-deformation prop-
should have a loading rate capability of 0 to 200 kg/min (0 to
erties of the specimens are measured under specific recom-
400 lb/min) or a crosshead movement rate of 0 to 1 mm/min (0
mended conditions to yield a “first estimate” of adhesive shear
to0.040in./min).Closed-loopcontrolofloadlevelandloading
modulus.Thisestimateisusedtodeterminetheoptimizedjoint
rate, or crosshead position and movement rate, is desirable to
geometry for best attainable uniformity of stress distribution in
facilitate testing under controlled cyclic loading conditions. A
the joint. A second set of specimens is prepared having the
working space approximately 450 by 450 mm (18 by 18 in.) is
optimized joint geometry. The final values for load-
desirable to accommodate the specimen grips and the installa-
deformation properties are then measured under a variety of
tion of a chamber for environmental control. In-line tension
controlled environmental and experimental conditions.
grips, shown in Fig. 4, are used for transmitting the load to the
4.2 The test method is based upon the theoretical analysis
specimen.
by Goland and Reissner relating stress concentrations (that is,
6.2 Slip Gage and Signal Conditioner:
nonuniformity) in single-lap joints to the geometry of the joint
6.2.1 The shear strain in adhesive layers is usually small.
and the mechanical properties of the materials involved. The
Thin layers of relatively rigid adhesives (greater than 50 MPa
controlling factor in the Goland and Reissner equations is a
(7000 psi)) require anASTM ClassAextensometer. Class B-1
composite of essentially three ratios which can be manipulated
or B-2 extensometers suffice for thicker layers and more
to improve the stress uniformity in the joint, and thereby
flexible adhesives. Extensometer classes are described in
control the accuracy of measurement. Stress uniformity is
Practice E83.
improved by (1) increasing the adherend tensile modulus in
6.2.2 A mechanical-electrical transducer, the linear variable
relation to the shear modulus of the adhesive, and by (2)
differential transformer (LVDT), is well suited for these tests.
increasing adherend and adhesive thickness while minimizing
The LVDT with suitable signal conditioning will satisfy the
overlap length. Because of these relationships, the practice was
requirements of Class B andAextensometers. They are rugged
developed to use high-modulus adherends in thick cross
enough to remain fastened to the specimen through failure if
sections.
the gage is properly designed.
6.2.2.1 The LVDT should have a linear output over a
5. Significance and Use
displacement range of 62.5 mm (60.10 in.) to accommodate
5.1 This test method is capable of providing shear modulus
adhesive layers varying in shear modulus and thickness.
and shear strength values for adhesives with accuracy suitable
6.2.2.2 The LVDT transducers with signal conditioner
for use by design engineers in predicting the characteristics of
should provide several ranges of displacement resolution—
building assemblies bonded with nonrigid adhesives.Adhesive
between 0.0005 and 0.5 mm/cm (5 3 10 and 0.05 in./m) of
formulators will also find the method useful during the
chart paper.
development of new adhesive systems. In general, the thick
6.2.3 The slip gage shall employ two LVDTs as described in
adherend lap-shear test is a useful tool in research during
6.2.2, positioned in such a manner as to measure and compen-
studies of both short- and long-term load-deformation proper-
sate for rotation of the adherends as well as slip.
ties of adhesives. This thick adherend lap-shear test yields a
6.2.4 A gage design that has been found to compensate
satisfactorily for adherend rotation is shown in Fig. 5, Fig.
A1.1, and Fig. A1.2. The gage consists of three components:
Goland, M., and Reissner, E., “The Stresses in Cemented Joints,” Journal of
Applied Mechanics , November 1944, pp. A17–A27. the gage itself on which two LVDTs are mounted, the follower,
D3983–98 (2004)
FIG. 5 Dual Transducer Slip Gage Mounted on a Thick Adherend Lap Specimen
and a gage block. The gage and follower attach to opposing 6.4.2 The combined test chamber and conditioning unit
adherends by clamping knife edges. One knife edge on each shouldbecapableofmaintainingaconstanttemperaturewithin
component may be advanced or retracted by a captive screw. the limits from 23 to 71 6 1°C (80 to 160 6 2°F), and constant
The gage block is placed between the gage and follower to relative humidity within the limits of 44 to 98 6 2 % at a given
align the knife edges. The gage is clamped to the stationary or temperature.
downward moving adherend and the follower to the upward
6.4.3 A suitable test chamber is described in Annex A2.
moving adherend, so the LVDT core moves out of the LVDT
during loading. This prevents damage to the LVDT upon
7. Materials
failure of the specimen. The follower is equipped with a
7.1 Adherend:
knurled adjustment screw for each LVDT. These screws are
7.1.1 Wood—Hard maple (Acer saccharum or Acer nigrum)
used to null mechanically and electrically each LVDT prior to
with a minimum specific gravity of 0.60 is the standard wood
testing.
adherend for this test method. Other dense species with
6.2.5 The slip gage shall be equipped with a switching and
comparable modulus of elasticity such as yellow birch, Dou-
signal-conditioning device to permit recording the signal from
glas fir, western hemlock, or southern pine may be used. The
each LVDT individually or the sum of the signals.
lumber shall be of straight grain and free of defects, including
6.2.6 The LVDTs and slip gage components should be
knots, birdseye, short grain, decay, and any unusual discolora-
fabricated of corrosion-resistant materials.
tions within the shearing area. Criteria for lumber selection
6.3 X-Y Recorder— A general-purpose X-Y recorder with
shall be those described in Test Method D905.
inputs compatible with the outputs of the load cell and slip
7.2 Metal—Use cold-rolled steel or aluminum-alloy bar
gage is requir
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