ASTM D4027-98

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Designation: D 4027 – 98
Standard Test Method for
Measuring Shear Properties of Structural Adhesives by the
Modified-Rail Test
This standard is issued under the fixed designation D 4027; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 905 Test Method for Strength Properties of Adhesive
Bonds in Shear by Compression Loading
1.1 This test method describes equipment and procedures to
D 907 Terminology of Adhesives
measure the shear modulus and shear strength of adhesive
D 4442 Test Methods for Direct Moisture Content Measure-
layers between rigid adherends. The equipment may also be
ment of Wood and Wood-Base Materials
used for determining the adhesive’s shear creep compliance,
E 83 Practice for Verification and Classification of Exten-
the effects of strain history such as cyclic loading upon shear
someters
properties, and a failure criteria for biaxial stress conditions
2 E 229 Test Method for Shear Strength and Shear Modulus
such as shear plus tension and shear plus compression.
of Structural Adhesives
1.2 High-density wood shall be the preferred substrate. The
practical upper limit on the shear modulus that can be
3. Terminology
measured is determined by the shear modulus of the adherends
3.1 Definitions—Many terms in this test method are defined
and by the strain measuring device. Thus, the practical limit of
in Terminology D 907.
adhesive shear modulus that can be measured using high-
3.1.1 shear modulus, n—the ratio of shear stress to corre-
density wood adherends is about 690 MPa (1 3 10 psi).
sponding shear strain below the proportional limit. (Compare
NOTE 1—Wood-base composites, metal, plastic, reinforced plastics,
secant modulus.)
and other common construction materials may also be used for adherends.
3.1.1.1 Discussion—The term shear modulus is generally
1.3 The range of specimen dimensions that can be tested
reserved for materials that exhibit linear elastic behavior over
are: width 1.59 to 12.70 mm (0.0625 to 0.500 in.), length 102
most of their stress-strain diagram. Many adhesives exhibit
to 203 mm (4 to 8 in.), and adherend thickness 13 to 25 mm
curvilinear or nonelastic behavior, or both, in which case some
(0.50 to 1.00 in.). The standard specimen dimensions shall be:
other term, such as secant modulus, may be substituted.
width 3.18 mm (0.125 in.), length 203 mm (8 in.), and
3.1.2 shear strain, n—the tangent of the angular change,
adherend thickness 19 mm (0.75 in.). Bondline thicknesses
due to force between two lines originally perpendicular to each
from 0.15 to 3.18 mm (0.006 to 0.125 in.) may be tested.
other through a point in the body.
1.4 The values stated in SI units are to be regarded as the
3.1.2.1 Discussion—Shear strain equals adherend slip/
standard. The values given in parentheses are for information
adhesive layer thickness.
only.
3.1.3 shear strength, n—in an adhesive joint, the maximum
1.5 This standard does not purport to address all of the
average stress when a force is applied parallel to the joint.
safety concerns, if any, associated with its use. It is the
3.1.3.1 Discussion—In most adhesive test methods, the
responsibility of the user of this standard to establish appro-
shear strength is actually the maximum average stress at failure
priate safety and health practices and determine the applica-
of the specimen, not necessarily the true maximum stress in the
bility of regulatory limitations prior to use.
material.
3.2 Definitions of Terms Specific to This Standard:
2. Referenced Documents
3.2.1 load—the force applied to the specimen at any given
2.1 ASTM Standards:
time.
3.2.2 load-slip diagram—a diagram in which corresponding
values of load and slip are plotted against each other. Values of
load are usually plotted as ordinates and values of slip as
This test method is under the jurisdiction of ASTM Committee D-14 on
Adhesives and is the direct responsibility of Subcommittee D14.70 on Construction
abscissas.
Adhesives.
Current edition approved May 10, 1998. Published March 1999. Originally
published as D 4027 – 81. Last previous edition D 4027 – 93.
2 3
Kreuger, G. P., “Tests for the Shear Properties of Adhesives in Adherend- Annual Book of ASTM Standards, Vol 15.06.
Adhesive Assemblies,” Unpublished report. Michigan Technological Institute, Annual Book of ASTM Standards, Vol 04.10.
Houghton, MI. Annual Book of ASTM Standards, Vol 03.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 4027 – 98
FIG. 1 Top, Side, and End Views of the Modified-Rail Shear Apparatus
3.2.3 normal stress—the stress component perpendicular to other. Values of stress are usually plotted as ordinates (verti-
a plane on which the forces act, that is, perpendicular to the cally) and values of strain as abscissas (horizontally).
plane of the bondline.
3.2.4 proportional limit, n—the maximum stress that a 4. Summary of Test Method
material is capable of sustaining without significant deviation
4.1 Shear force is applied to the adhesive through the
from proportionality of stress to strain.
adherends by a modified-rail shear tool such as shown in Fig.
3.2.5 secant modulus—the slope of the secant drawn from
1. The adherends are firmly clamped between two pairs of rigid
the origin to any specified point on the stress-strain curve.
rails as shown in Fig. 2. One pair is fixed and the other is
3.2.5.1 Discussion—Modulus is expressed in force per unit
movable. The rigid rails limit undesired adherend deformation
area (megapascals, pounds-force per square inch, etc.).
during testing. The pair of movable rails is fixed to two
3.2.6 shear stress—the stress component tangential to the
counter-moment pivot arms. These arms restrict the attached
plane on which the forces act, that is, in the plane of the
rails (and clamped adherend) to collinear motion with respect
bondline.
to the fixed rails (and clamped adherend). The results of using
3.2.7 slip—the relative collinear displacement of the adher-
this shear tool are nearly uniform stress and strain distributions
ends on either side of the adhesive layer in the direction of the
and the reduction of normal stress in the adhesive layer under
applied load.
load. Such conditions are necessary for accurate measurement
3.2.7.1 Discussion—This term differs from that of the
of the adhesive shear properties.
stress-strain diagram in that load and slip are not divided by 4.2 A known amount of uniform tensile or compression
bond area and bond thickness (the constants that convert load
force can be applied to the adhesive layer by the shear tool in
to stress and slip to strain). In actual practice, stress-strain order to develop a fracture criteria for the adhesive under
information is generally collected in the form of a load-slip
combined states of stress, such as shear plus tension, or shear
diagram for ease in plotting. plus compression, which commonly occur in bonded struc-
3.2.8 stress–strain diagram—a diagram in which corre- tures. Fig. 3 shows combined shear and tensile forces on the
sponding values of stress and strain are plotted against each clamped specimen.
D 4027 – 98
FIG. 2 Top View of the Rail Clamps Showing How the Specimen Is Gripped for Testing
4.3 The basic output of the test method is the bond shear adherends in the torsion test. The modified-rail test does not
strength determined as the shear stress at failure, and the have this disadvantage.
stress-strain diagram determined from the plot of load on the 5.2 Two undesirable conditions occur in the modified-rail
shear tool versus the shear displacement of the bond line. test specimens that do not occur in butt-joined cylinders;
4.4 Bond strength and the stress-strain diagram may be nonuniform shear-stress distribution along the joint, and the
obtained for a variety of environmental and loading conditions. addition of some undefined combination of tension and com-
Specific recommendations are made for a minimum test pression stresses to the shear stress at a given location in the
program. joint. The modified-rail shear tool minimizes but does not
eliminate these undesirable effects.
5. Significance and Use
5.3 Shear modulus, strength, and other properties are mea-
5.1 Structural design based on strength of materials prin-
sured by the modified-rail method.
ciples or the theory of elasticity requires knowledge of the
6. Apparatus
mechanical properties of the structural components, including
adhesives. By the nature of their use, the most important 6.1 Universal Testing Machine:
adhesive properties are shear modulus and shear strength. A 6.1.1 The universal testing machine shall have a minimum
torsion test, such as described in Test Method E 229, is load capacity of 8900 N (2000 lbf), and a range of crosshead
theoretically the most accurate method for measuring adhesive speed from 0.317 to 10.16 mm/min (0.0125 to 0.40 in./min). A
shear properties. It is, however, impractical in many situations. minimum vertical space of 508 mm (20 in.) and horizontal
For example, certain materials of construction are not readily space of 305 mm (12 in.) is required to install the shear tool in
adaptable to fabricating the thin-walled cylinders used as the testing machine.
D 4027 – 98
NOTE 1—During a shear only test the horizontal arrows (tension forces) would be absent.
FIG. 3 Side View of the Rail Clamps Showing the Forces On the Clamps (Specimen) During Combined Shear and Tension Loading
6.1.2 The testing machine shall have a device capable of test. The bolt has a strain gage bonded to it that, with a suitable
reading the load to the nearest 4.5 6 0.9 N (1.0 6 0.2 lbf). This readout device and calibration, can be used to set the desired
readout device should preferably be an electronic load cell to normal force.
facilitate simultaneous recording of load with the adhesive 6.3 Slip or Strain Gage—Since the shear strain of adhesive
deformation. layers will normally be very small, an ASTM Class A or Class
6.2 Modified-Rail Shear Tool: B-1 extensometer as described in Practice E 83 shall be used.
6.2.1 A shear tool suitable for this test method is illustrated A mechanical-electrical transducer such as the linear variable
in Fig. 1, Fig. 2, Fig. 4, Fig. 5, and Fig. 6. differential transducer (LVDT) can be used to measure the
6.2.2 The shear tool is fitted with a threaded bolt (Adjuster, shear slip indirectly by attachment of the LVDT to the
Fig. 1 ) to apply normal force for combined stress studies. The specimen clamps. Or miniature electrical resistance strain
magnitude of the normal force is constant from the outset of the gages can be used to measure the shear strain by direct
attachment to the adhesive joint.
7. Materials
Complete detail drawings of the modified-rail shear apparatus are available
7.1 The adhesives used shall be selected by the adhesive
from the Forest Products Laboratory, Forest Service, U.S. Department of Agricul-
ture, Madison, WI 53705. manufacturer or by the party requesting these tests.
D 4027 – 98
FIG. 4 Detail Drawings of Modified-Rail Shear Apparatus
FIG. 5 Schematic Diagram Showing Use of the Modified-Rail Shear Apparatus With a Universal Test Machine to Apply Load
7.2 Hard maple shall be the standard material for specimen 7.2.1 Generally a high-density wood such as hard maple,
adherends. Other species may be selected at the option of the yellow birch, Douglas-fir, or southern pine are desirable to
adhesive manufacturer or by the party requesting these tests. minimize wood deformation effects on the measured adhesive
D 4027 – 98
FIG. 6 Schematic Diagram Showing Use of the Modified-Rail Shear Apparatus With an Integral Hydraulic Cylinder to Apply Load
deformation. The specific gravity of the lumber selected shall 9.1.2.2 Bondline thickness shall never be greater than the
equal or exceed average specific gravity for the species as
adhesive manufacturer’s stated maximum thickness.
given in Table 4-2 of the Wood Handbook. For hard maple,
9.1.3 The maximum range of bondline thickness that is
the average is 0.63. A method of selecting maple lumber of
acceptable for use in this test method is 0.15 to 3.18 mm (0.006
satisfactory specific gravity is described in the appendix to Test
to 0.125 in.).
Method D 905.
9.2 Specimen Preparation:
7.2.2 A uniform textured wood such as maple or birch is
9.2.1 Cut the lumber into pieces measuring nominal 25 by
desirable to minimize wood density variation effects on the
64 by 305 mm (1 by 2.5 by 12 in.) with the grain in the long
adhesive layer. Coarse-textured woods such as Douglas-fir,
direction. Lightly surface both faces of each piece. Condition
hemlock, or southern pine are acceptable however.
these pieces to an equilibrium moisture content between 7 and
7.2.3 The wood shall be nominal 25.4 mm (1-in.) flat-sawn
10 % (ovendry basis) or to the moisture content specified by
lumber presenting a flat grain (tangential surface) for bonding.
the adhesive manufacturer. Determine moisture content at
7.2.4 The lumber shall be straight-grained and free of
equilibrium from extra pieces of lumber in accordance with
defects including knots, cracks, abrupt grain deviations, decay,
Procedure A of Test Methods D 4442.
and any unusual discolorations within the bond area.
9.2.2 Prepare one 64 by 305-mm (2.5 by 12-in.) surface of
8. Sampling
each board for bonding not longer than 2 days prior to bonding
by lightly surfacing it with a hand-fed jointer. If a jig is used
8.1 When testing adhesives that form highly variable bond-
during gluing to control the bondline thickness, the pieces
lines such as the solvent dispersed construction adhesives,
should be thickness planed on the opposite face to achieve the
prepare at least three billets for each test condition. Individual
proper thickness for the jig and to ensure that the faces are
specimens cut from the billets shall be drawn at random for
parallel.
assignment to a given test condition.
8.2 Eight specimens shall be tested at every set of condi- 9.2.3 Follow the adhesive manufacturer’s instructions when
tions. applying the adhesive and controlling the assembly time.
Ensure that enough adhesive is applied, especially to thick
9. Test Specimen
joints to eliminate voids from this source.
9.1 Specimen Dimensions:
9.2.4 To minimize variability along the specimen, contr
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