ASTM D2718-00(2011)e1
(Test Method)Standard Test Methods for Structural Panels in Planar Shear (Rolling Shear)
Standard Test Methods for Structural Panels in Planar Shear (Rolling Shear)
SIGNIFICANCE AND USE
3.1 Planar shear (rolling shear) characteristics of structural panels determined by these test methods are essential for the rigorous design of various glued wood-panel structural components, such as box beams, folded plate roofs, and stressed skin panels. Planar shear also may govern the design at low span-depth ratios encountered in floors subjected to high concentrated loads, concrete forms at high pouring pressures, and bulk storage structures.
3.2 The modulus of rigidity determined from Test Method A is a composite of the entire specimen acting as a unit. For plywood panels for which the ratio between the shear moduli of the plies with grain oriented parallel and perpendicular to the shear forces is known, the rolling shear modulus of the perpendicular plies can be calculated.
3.3 Veneer produced by slicing or rotary peeling may contain fine checks or separations parallel to the grain on the knife side of the veneer that are produced as the knife is forced through the wood. These checks are termed “knife checks” to distinguish them from occasional checks that may be formed on the opposite side of the veneer by forces at the compression bar, and from checks caused by drying. Knife checks can have a significant effect on rolling shear properties in plywood panels and may be of significance in other veneer containing panels. Test Method A requires (when applicable) the testing of matching specimens having knife checks oriented both open and closed wherever possible (see Fig. 1).
(a) Knife Checks Open
(b) Knife Checks Closed
3.4 To control or define other variables influencing rolling shear, these test methods require determination of moisture content, specific gravity, and elapsed time-to-failure. Conditioning of test material in controlled atmospheres, determination of depth of knife checks (when applicable), and determination of percent of wood and plywood glueline failure (when applicable) are recommended.
SCOPE
1.1 These test methods determine the shear properties of structural panels associated with shear distortion of the planes parallel to the edge planes of the panels. Both shear strength and modulus of rigidity may be determined. Primarily, the tests measure the planar shear (rolling shear) strength developed in the plane of the panel.
1.2 Structural panels in use include plywood, waferboard, oriented strand board, and composites of veneer and of wood-based layers.
1.3 Two test methods are included:
1.3.1 Test Method A—Planar shear loaded by plates.
1.3.2 Test Method B—Planar shear induced by five-point bending.
1.3.3 The choice of method will be dictated by the purpose of the test and equipment available.
1.3.4 Test Method A, Planar Shear Loaded by Plates—This test method uses a rectangular panel section adhered between steel plates with protruding knife edges to create load at the panel faces. This test method has been used to develop shear properties of plywood and oriented strand board for the purpose of confirming design values. This test method does not produce pure shear, but the specimen length is prescribed so that the secondary stresses have a minimum effect. The method determines shear strength and modulus of rigidity.
1.3.5 Test Method B, Planar Shear Induced by Five-Point Bending—Planar shear stress is induced on the panel while loaded in bending using two continuous spans. This test method determines planar shear strength consistent with panel applications under transverse loading. This test method is able to determine shear strength at any moisture condition.
1.4 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.
1.5 This international standard was developed in accordance with interna...
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´1
Designation: D2718 − 00 (Reapproved 2011)
Standard Test Methods for
Structural Panels in Planar Shear (Rolling Shear)
This standard is issued under the fixed designation D2718; 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.
ε NOTE—Eq 2 and Eq 4 were corrected editorially in April 2017.
1. Scope 1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 These test methods determine the shear properties of
ization established in the Decision on Principles for the
structural panels associated with shear distortion of the planes
Development of International Standards, Guides and Recom-
parallel to the edge planes of the panels. Both shear strength
mendations issued by the World Trade Organization Technical
and modulus of rigidity may be determined. Primarily, the tests
Barriers to Trade (TBT) Committee.
measure the planar shear (rolling shear) strength developed in
the plane of the panel.
2. Referenced Documents
1.2 Structural panels in use include plywood, waferboard, 2
2.1 ASTM Standards:
oriented strand board, and composites of veneer and of
D2395 Test Methods for Density and Specific Gravity (Rela-
wood-based layers.
tive Density) of Wood and Wood-Based Materials
1.3 Two test methods are included: D4442 Test Methods for Direct Moisture Content Measure-
1.3.1 Test Method A—Planar shear loaded by plates. ment of Wood and Wood-Based Materials
1.3.2 Test Method B—Planar shear induced by five-point
3. Significance and Use
bending.
1.3.3 The choice of method will be dictated by the purpose
3.1 Planar shear (rolling shear) characteristics of structural
of the test and equipment available.
panels determined by these test methods are essential for the
1.3.4 Test Method A, Planar Shear Loaded by Plates—This rigorous design of various glued wood-panel structural
test method uses a rectangular panel section adhered between
components, such as box beams, folded plate roofs, and
steel plates with protruding knife edges to create load at the stressed skin panels. Planar shear also may govern the design
panel faces. This test method has been used to develop shear
atlowspan-depthratiosencounteredinfloorssubjectedtohigh
properties of plywood and oriented strand board for the
concentrated loads, concrete forms at high pouring pressures,
purpose of confirming design values.This test method does not
and bulk storage structures.
produce pure shear, but the specimen length is prescribed so
3.2 The modulus of rigidity determined fromTest MethodA
that the secondary stresses have a minimum effect.The method
is a composite of the entire specimen acting as a unit. For
determines shear strength and modulus of rigidity.
plywood panels for which the ratio between the shear moduli
1.3.5 Test Method B, Planar Shear Induced by Five-Point
oftheplieswithgrainorientedparallelandperpendiculartothe
Bending—Planar shear stress is induced on the panel while
shear forces is known, the rolling shear modulus of the
loaded in bending using two continuous spans. This test
perpendicular plies can be calculated.
method determines planar shear strength consistent with panel
3.3 Veneer produced by slicing or rotary peeling may
applications under transverse loading. This test method is able
contain fine checks or separations parallel to the grain on the
to determine shear strength at any moisture condition.
knife side of the veneer that are produced as the knife is forced
1.4 This standard does not purport to address all of the
through the wood. These checks are termed “knife checks” to
safety concerns, if any, associated with its use. It is the
distinguish them from occasional checks that may be formed
responsibility of the user of this standard to establish appro-
on the opposite side of the veneer by forces at the compression
priate safety and health practices and determine the applica-
bar, and from checks caused by drying. Knife checks can have
bility of regulatory limitations prior to use.
a significant effect on rolling shear properties in plywood
This test method is under the jurisdiction of ASTM Committee D07 on Wood
and is the direct responsibility of Subcommittee D07.03 on Panel Products. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2011. Published November 2011. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1969. Last previous edition approved in 2000 as D2718 – 00 (2006). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D2718-00R11E01. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D2718 − 00 (2011)
panels and may be of significance in other veneer containing 5.2 This international standard was developed in accor-
panels.Test MethodArequires (when applicable) the testing of dance with internationally recognized principles on standard-
matching specimens having knife checks oriented both open ization established in the Decision on Principles for the
and closed wherever possible (see Fig. 1). Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
3.4 To control or define other variables influencing rolling
Barriers to Trade (TBT) Committee.
shear, these test methods require determination of moisture
content, specific gravity, and elapsed time-to-failure. Condi-
6. Test Specimen
tioning of test material in controlled atmospheres, determina-
6.1 Specimen thickness shall be that of the material. Speci-
tion of depth of knife checks (when applicable), and determi-
mensfrommaterialthatisexpectedtovarysignificantlywithin
nation of percent of wood and plywood glueline failure (when
the specimen due to growth or manufacturing features or from
applicable) are recommended.
other causes shall be 6 in. (15 cm) wide by 18 in. (45 cm) long
4. Control of Moisture Content or larger as shown in Fig. 2. This size is recommended for
uniform material as well. However, smaller specimens of
4.1 The structural panel samples to be tested at specific
uniform material may be used if these are not less than four
moisture contents or equilibrium relative humidities shall be
times the thickness in width nor twelve times the thickness in
conditioned to approximately constant weight in controlled
length.
atmospheric conditions before gluing to plates. For approxi-
mating moisture conditions of structural panel used under dry 6.2 From each sample of panels containing veneer, two
conditions a relative humidity of 65 6 2 % at a temperature of matching specimens shall be cut. Knife edges of loading plates
68 6 6°F (20 6 3°C) is recommended. Specimens shall be for one specimen of each matching pair shall be oriented
tested without undue delay after the adhesive is cured. Testing perpendicular to one of the primary panel directions or for
in similarly controlled atmospheres is recommended wherever plywood to cause opening of knife checks during test as shown
possible. in Fig. 1(a). Knife edges of plates loading the other specimen
shall be positioned perpendicular to one of the primary panel
Test Method A—Planar Shear Loaded by Plates
directions or for plywood to cause knife checks to close during
test as shown in Fig. 1(b). Proper plywood orientation may be
5. Scope
determined from check depth specimens described in 16.3.It
5.1 The specimen having the form of a rectangular flat plate
may not be possible to test samples having two or more plies
is bonded between steel plates beveled at opposite ends of the
stressed in rolling shear in both “open” and “closed” orienta-
specimen to provide knife edges for loading the plate at the
tions if these plies are oriented in opposite directions causing a
face bonded to the specimen. The knife edges project beyond
“checks open” failure regardless of direction of loading.
the ends of the specimen. This test method is conducted by
6.3 Specimen length and width shall be measured to the
loading the knife edges in compression at a uniform rate while
nearest 0.01 in. (0.25 mm) and thickness to the nearest 0.001
a suitable gage measures slip between the plates due to
specimen deformation. Shear strength is computed from maxi-
mum load, and effective shear modulus for the specimen is
determined from a plot of load versus slip.
NOTE 1—The “V” block is supported on a seat that provides rotation
about the axis perpendicular to the knife edge only.
Metric Equivalents
in. 6 18
mm 15 45
(a) Knife Checks Open
(b) Knife Checks Closed
FIG. 2 Planar (Rolling) Shear Test Using a Dial Gage for Measur-
FIG. 1 Orientation of Knife Checks in Plywood ing Plate Slip
´1
D2718 − 00 (2011)
in. (0.025 mm). When applicable, the direction of knife checks 7.2.1 Elapsed time from beginning of load application to
in plies having grain perpendicular to its length shall be failure of each specimen shall be measured and recorded to the
determined and the specimens marked for position of knife
nearest half minute. Machine speeds calculated by the above
edges. At the time specimens are cut matching samples for
formula will normally produce failure in the range of 3 to 12
determination of moisture content and specific gravity in
min elapsed time from the beginning of loading. Should
accordance with 16.1 and 16.2 shall be obtained. When
elapsed time to failure fall greatly outside this range, machine
measurement of knife checks is included as discussed in 16.3,
speed should be modified to obtain times within this range.
a sample for this measurement also may be cut at this time.
7.3 Both epoxy and polyvinyl adhesives have been found
satisfactory for bonding steel plates to specimens. Minimum
7. Loading
required surface preparation of steel plates consists of removal
7.1 Figs.1and2illustratethespecimenandsuitableloading
of residual adhesive. This can be accomplished most easily by
plates and blocks for loading the knife edges of the plates. The
mild heating of the plate and any portion of the specimen
specimen shall be loaded by steel plates bonded to both faces
remaining from the previous test in an oven which weakens the
of the specimen with an adhesive sufficiently rigid to preclude
bond to the steel sufficiently to permit peeling the remaining
contributionofadhesivecreeptomeasureddeformation.Width
wood and adhesive from the plate. The residual adhesive may
of plates shall be that of the specimen. One end of each plate
be scraped off with a sharp-edged tool. Further degreasing and
shall be provided with a knife edge projecting ⁄4 in. (6 mm)
cleaning has frequently been found necessary in addition to the
beyond the end of the specimen at one end and flush with the
above to ensure adequate bond strength. Curing the adhesive at
surface glued to the specimen. The other end of the plate shall
a slightly elevated temperature has also been helpful.
be square and flush with the end of the specimen. Knife edges
of the two plates shall be at opposite ends of the specimen and
8. Measurement of Deformation
shall be oriented to load the specimen in the desired direction
in relation to the knife checks. Planar shear properties of 8.1 Slip between the steel plates during load application
structural panels should be determined in both directions. shall be measured to at least the nearest 0.0001 in. (0.002 mm)
Plates for specimens 18 in. (45 cm) long shall be 1 in. (2.5 cm)
at no less than twelve and preferably more equally spaced
thick. The thickness of plates for shorter specimens may be increments of load to proportional limit from which a load-
reduced proportionately. Loading of at least one V-block shall deformation curve shall be plotted. Slip can be measured with
provide for uniform load distribution along the knife edge by
a dial gage as illustrated in Figs. 2 and 3 or with appropriate
loading through a pivot having its axis perpendicular to the
automatic measuring and recording equipment. Gage geometry
knife edge and centered along it. Pivots permitting rotation
and position on the specimen shall be such as to minimize any
about an axis parallel to the knife edge or spherical seats free
effects of unsymmetrical loading or deformation.
to pivot in this manner shall not be used as they create unstable
loadingwhichmaycauseviolentejectionofthespecimenfrom
9. Calculation
the machine and hazard to operating personnel. The V-blocks
9.1 Shear stress shall be calculated as follows:
shall be vertically positioned in the machine, one above the
other, causing the forces applied to the specimen to act parallel f 5 P⁄ L · W (2)
~ !
v
to the axis of the machine. The specimen itself will be slightly
where:
inclined when placed in the machine. A means of holding the
f = shear stress, psi (N/mm),
v
plates in an upright position after the specimen has sheared
P = maximum or proportional limit load (force), lbf (N),
apart is desirable as a complete separation of the specimen
W = specimen width, in. (mm), and
permits the plates to be thrown out of the machine with
L = specimen length, in. (mm).
attendant hazard to the operator.
Maximum shear stress obtained from specimens having final
7.2 Loadshallbeappliedcontinuouslythroughoutthetestat
failure of the bond between the plate and the specimen shall be
constant rate of cross-head motion to normally produce failure
regarded as defective and shall be clearly indicated in the
in the range of 3 to 12 min elapsed time from beginning of
report of results.
loading. For plywood, the approximate speed may be deter-
mined as follows:
9.2 Effective modulus of rigidity for the specimen acting as
a unit shall be calculated as follows:
N 5 0.0075 T 1R T (1)
~ !
( ( '
?
G 5 P/∆ t/ L·W (3)
~ !@ ~ !#
where:
where:
N = crosshead speed, in./min (cm/min),
∑T = total thickness of plies having grain parallel to G = apparent modulus of rigidity for the entire specimen,
|
direction of shear force, in. (cm), psi (N/mm),
R = 8 (assumed ratio of shear modulus of parallel plies to t = specimen thickness, in. (mm),
P/∆ = slope of the force-deformation curve below propor-
shear modulus of perpendicular plies), and
∑T = total thickness of plies having grain perpendicular to tional limit load, lbf/in. (N/mm), and other notation is
'
the direction of shear force, in. (cm). as indicated in 9.1.
´1
D2718 − 00 (2011)
FIG. 3 Planar (Rolling) Shear Specimen Re
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: D2718 − 00 (Reapproved 2011) D2718 − 00 (Reapproved 2011)
Standard Test Methods for
Structural Panels in Planar Shear (Rolling Shear)
This standard is issued under the fixed designation D2718; 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.
ε NOTE—Eq 2 and Eq 4 were corrected editorially in April 2017.
1. Scope
1.1 These test methods determine the shear properties of structural panels associated with shear distortion of the planes parallel
to the edge planes of the panels. Both shear strength and modulus of rigidity may be determined. Primarily, the tests measure the
planar shear (rolling shear) strength developed in the plane of the panel.
1.2 Structural panels in use include plywood, waferboard, oriented strand board, and composites of veneer and of wood-based
layers.
1.3 Two test methods are included:
1.3.1 Test Method A—Planar shear loaded by plates.
1.3.2 Test Method B—Planar shear induced by five-point bending.
1.3.3 The choice of method will be dictated by the purpose of the test and equipment available.
1.3.4 Test Method A, Planar Shear Loaded by Plates—This test method uses a rectangular panel section adhered between steel
plates with protruding knife edges to create load at the panel faces. This test method has been used to develop shear properties
of plywood and oriented strand board for the purpose of confirming design values. This test method does not produce pure shear,
but the specimen length is prescribed so that the secondary stresses have a minimum effect. The method determines shear strength
and modulus of rigidity.
1.3.5 Test Method B, Planar Shear Induced by Five-Point Bending—Planar shear stress is induced on the panel while loaded
in bending using two continuous spans. This test method determines planar shear strength consistent with panel applications under
transverse loading. This test method is able to determine shear strength at any moisture condition.
1.4 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.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D2395 Test Methods for Density and Specific Gravity (Relative Density) of Wood and Wood-Based Materials
D4442 Test Methods for Direct Moisture Content Measurement of Wood and Wood-Based Materials
3. Significance and Use
3.1 Planar shear (rolling shear) characteristics of structural panels determined by these test methods are essential for the rigorous
design of various glued wood-panel structural components, such as box beams, folded plate roofs, and stressed skin panels. Planar
shear also may govern the design at low span-depth ratios encountered in floors subjected to high concentrated loads, concrete
forms at high pouring pressures, and bulk storage structures.
This test method is under the jurisdiction of ASTM Committee D07 on Wood and is the direct responsibility of Subcommittee D07.03 on Panel Products.
Current edition approved Nov. 1, 2011. Published November 2011. Originally approved in 1969. Last previous edition approved in 2000 as D2718 – 00 (2006). DOI:
10.1520/D2718-00R11.10.1520/D2718-00R11E01.
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 the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D2718 − 00 (2011)
3.2 The modulus of rigidity determined from Test Method A is a composite of the entire specimen acting as a unit. For plywood
panels for which the ratio between the shear moduli of the plies with grain oriented parallel and perpendicular to the shear forces
is known, the rolling shear modulus of the perpendicular plies can be calculated.
3.3 Veneer produced by slicing or rotary peeling may contain fine checks or separations parallel to the grain on the knife side
of the veneer that are produced as the knife is forced through the wood. These checks are termed “knife checks” to distinguish
them from occasional checks that may be formed on the opposite side of the veneer by forces at the compression bar, and from
checks caused by drying. Knife checks can have a significant effect on rolling shear properties in plywood panels and may be of
significance in other veneer containing panels. Test Method A requires (when applicable) the testing of matching specimens having
knife checks oriented both open and closed wherever possible (see Fig. 1).
3.4 To control or define other variables influencing rolling shear, these test methods require determination of moisture content,
specific gravity, and elapsed time-to-failure. Conditioning of test material in controlled atmospheres, determination of depth of
knife checks (when applicable), and determination of percent of wood and plywood glueline failure (when applicable) are
recommended.
4. Control of Moisture Content
4.1 The structural panel samples to be tested at specific moisture contents or equilibrium relative humidities shall be conditioned
to approximately constant weight in controlled atmospheric conditions before gluing to plates. For approximating moisture
conditions of structural panel used under dry conditions a relative humidity of 65 6 2 % at a temperature of 68 6 6°F (20 6 3°C)
is recommended. Specimens shall be tested without undue delay after the adhesive is cured. Testing in similarly controlled
atmospheres is recommended wherever possible.
Test Method A—Planar Shear Loaded by Plates
5. Scope
5.1 The specimen having the form of a rectangular flat plate is bonded between steel plates beveled at opposite ends of the
specimen to provide knife edges for loading the plate at the face bonded to the specimen. The knife edges project beyond the ends
of the specimen. This test method is conducted by loading the knife edges in compression at a uniform rate while a suitable gage
measures slip between the plates due to specimen deformation. Shear strength is computed from maximum load, and effective
shear modulus for the specimen is determined from a plot of load versus slip.
5.2 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
6. Test Specimen
6.1 Specimen thickness shall be that of the material. Specimens from material that is expected to vary significantly within the
specimen due to growth or manufacturing features or from other causes shall be 6 in. (15 cm) wide by 18 in. (45 cm) long or larger
(a) Knife Checks Open
(b) Knife Checks Closed
FIG. 1 Orientation of Knife Checks in Plywood
´1
D2718 − 00 (2011)
as shown in Fig. 2. This size is recommended for uniform material as well. However, smaller specimens of uniform material may
be used if these are not less than four times the thickness in width nor twelve times the thickness in length.
6.2 From each sample of panels containing veneer, two matching specimens shall be cut. Knife edges of loading plates for one
specimen of each matching pair shall be oriented perpendicular to one of the primary panel directions or for plywood to cause
opening of knife checks during test as shown in Fig. 1(a). Knife edges of plates loading the other specimen shall be positioned
perpendicular to one of the primary panel directions or for plywood to cause knife checks to close during test as shown in Fig.
1(b). Proper plywood orientation may be determined from check depth specimens described in 16.3. It may not be possible to test
samples having two or more plies stressed in rolling shear in both “open” and “closed” orientations if these plies are oriented in
opposite directions causing a “checks open” failure regardless of direction of loading.
6.3 Specimen length and width shall be measured to the nearest 0.01 in. (0.25 mm) and thickness to the nearest 0.001 in. (0.025
mm). When applicable, the direction of knife checks in plies having grain perpendicular to its length shall be determined and the
specimens marked for position of knife edges. At the time specimens are cut matching samples for determination of moisture
content and specific gravity in accordance with 16.1 and 16.2 shall be obtained. When measurement of knife checks is included
as discussed in 16.3, a sample for this measurement also may be cut at this time.
7. Loading
7.1 Figs. 1 and 2 illustrate the specimen and suitable loading plates and blocks for loading the knife edges of the plates. The
specimen shall be loaded by steel plates bonded to both faces of the specimen with an adhesive sufficiently rigid to preclude
contribution of adhesive creep to measured deformation. Width of plates shall be that of the specimen. One end of each plate shall
be provided with a knife edge projecting ⁄4 in. (6 mm) beyond the end of the specimen at one end and flush with the surface glued
to the specimen. The other end of the plate shall be square and flush with the end of the specimen. Knife edges of the two plates
shall be at opposite ends of the specimen and shall be oriented to load the specimen in the desired direction in relation to the knife
checks. Planar shear properties of structural panels should be determined in both directions. Plates for specimens 18 in. (45 cm)
long shall be 1 in. (2.5 cm) thick. The thickness of plates for shorter specimens may be reduced proportionately. Loading of at least
one V-block shall provide for uniform load distribution along the knife edge by loading through a pivot having its axis
perpendicular to the knife edge and centered along it. Pivots permitting rotation about an axis parallel to the knife edge or spherical
seats free to pivot in this manner shall not be used as they create unstable loading which may cause violent ejection of the specimen
from the machine and hazard to operating personnel. The V-blocks shall be vertically positioned in the machine, one above the
other, causing the forces applied to the specimen to act parallel to the axis of the machine. The specimen itself will be slightly
inclined when placed in the machine. A means of holding the plates in an upright position after the specimen has sheared apart
is desirable as a complete separation of the specimen permits the plates to be thrown out of the machine with attendant hazard to
the operator.
7.2 Load shall be applied continuously throughout the test at constant rate of cross-head motion to normally produce failure in
the range of 3 to 12 min elapsed time from beginning of loading. For plywood, the approximate speed may be determined as
follows:
NOTE 1—The “V” block is supported on a seat that provides rotation about the axis perpendicular to the knife edge only.
Metric Equivalents
in. 6 18
mm 15 45
FIG. 2 Planar (Rolling) Shear Test Using a Dial Gage for Measuring Plate Slip
´1
D2718 − 00 (2011)
N 5 0.0075 T 1R T (1)
~ !
( ( '
?
where:
N = crosshead speed, in./min (cm/min),
∑T = total thickness of plies having grain parallel to direction of shear force, in. (cm),
|
R = 8 (assumed ratio of shear modulus of parallel plies to shear modulus of perpendicular plies), and
∑T = total thickness of plies having grain perpendicular to the direction of shear force, in. (cm).
'
7.2.1 Elapsed time from beginning of load application to failure of each specimen shall be measured and recorded to the nearest
half minute. Machine speeds calculated by the above formula will normally produce failure in the range of 3 to 12 min elapsed
time from the beginning of loading. Should elapsed time to failure fall greatly outside this range, machine speed should be modified
to obtain times within this range.
7.3 Both epoxy and polyvinyl adhesives have been found satisfactory for bonding steel plates to specimens. Minimum required
surface preparation of steel plates consists of removal of residual adhesive. This can be accomplished most easily by mild heating
of the plate and any portion of the specimen remaining from the previous test in an oven which weakens the bond to the steel
sufficiently to permit peeling the remaining wood and adhesive from the plate. The residual adhesive may be scraped off with a
sharp-edged tool. Further degreasing and cleaning has frequently been found necessary in addition to the above to ensure adequate
bond strength. Curing the adhesive at a slightly elevated temperature has also been helpful.
8. Measurement of Deformation
8.1 Slip between the steel plates during load application shall be measured to at least the nearest 0.0001 in. (0.002 mm) at no
less than twelve and preferably more equally spaced increments of load to proportional limit from which a load-deformation curve
shall be plotted. Slip can be measured with a dial gage as illustrated in Figs. 2 and 3 or with appropriate automatic measuring and
recording equipment. Gage geometry and position on the specimen shall be such as to minimize any effects of unsymmetrical
loading or deformation.
FIG. 3 Planar (Rolling) Shear Specimen Ready for Testing
´1
D2718 − 00 (2011)
9. Calculation
9.1 Shear stress shall be calculated as follows:
(2)
f 5 P⁄ L · W (2)
~ !
v
where:
f = shear stress, psi (N/mm),
v
P = maximum or proportional limit load (force), lbf (N),
W = specimen width, in. (mm), and
L = specimen length, in. (mm).
Maximum shear stress obtained from specimens having final failure of the bond between the plate and the specimen shal
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Questions, Comments and Discussion
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