ASTM D7247-06
(Test Method)Standard Test Method for Evaluating the Shear Strength of Adhesive Bonds in Laminated Wood Products at Elevated Temperatures
Standard Test Method for Evaluating the Shear Strength of Adhesive Bonds in Laminated Wood Products at Elevated Temperatures
SCOPE
1.1 This standard describes a test method for evaluating the comparative shear strength of a planar adhesive bond at both ambient and elevated temperatures relative to the performance of solid wood under the same conditions. The test method is based on the breaking load after the specimen is exposed to either ambient or a constant elevated temperature for a specified duration as described in Section . This standard does not preclude the development and implementation of other methods that provide equivalent performance meeting the intent of this method.
1.2 This test method is intended for the evaluation of adhesives that can be used to assemble test specimens in accordance with Test Method D 905. The evaluation of other types of adhesives, such as the binder systems used for strand-based products, is beyond the scope of this test method.
1.3 This test method is intended for the evaluation of adhesives as a component of laminated wood products at elevated temperatures. The evaluation of fire performance on fire-rated laminated wood products or assemblies is beyond the scope of this test method.
1.4 While it is preferable to use solid wood specimens as described in Section as the control, structural composite lumber products as defined in Specification D 5456 shall be permitted for use provided they are matched with the bonded specimens in accordance with Section and the ignition temperature is not significantly lower than solid wood of the same species.
1.5 The exact formulation of adhesive supplied to the manufacturer of laminated wood products shall be evaluated. Modifications to the adhesive formulation require a separate evaluation unless approved by the manufacturer of the laminated wood product, qualified agency, and code evaluation agency.
1.6 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
This standard does not purport to address all of the safety concerns, such as the fire hazard, 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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D7247–06
Standard Test Method for
Evaluating the Shear Strength of Adhesive Bonds in
Laminated Wood Products at Elevated Temperatures
This standard is issued under the fixed designation D 7247; 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 1.7 This standard does not purport to address all of the
safety concerns, such as the fire hazard, associated with its use.
1.1 This standard describes a test method for evaluating the
It is the responsibility of the user of this standard to establish
comparative shear strength of a planar adhesive bond at both
appropriate safety and health practices and determine the
ambient and elevated temperatures relative to the performance
applicability of regulatory limitations prior to use.
of solid wood under the same conditions. The test method is
based on the breaking load after the specimen is exposed to
2. Referenced Documents
either ambient or a constant elevated temperature for a speci-
2.1 ASTM Standards:
fied duration as described in Section 7. This standard does not
D 905 Test Method for Strength Properties of Adhesive
preclude the development and implementation of other meth-
Bonds in Shear by Compression Loading
ods that provide equivalent performance meeting the intent of
D 907 Terminology of Adhesives
this method.
D 2395 Test Methods for Specific Gravity of Wood and
1.2 This test method is intended for the evaluation of
Wood-Based Materials
adhesives that can be used to assemble test specimens in
D 2915 Practice for Evaluating Allowable Properties for
accordance with Test Method D 905. The evaluation of other
Grades of Structural Lumber
types of adhesives, such as the binder systems used for
D 4933 Guide for Moisture Conditioning of Wood and
strand-based products, is beyond the scope of this test method.
Wood-Based Materials
1.3 This test method is intended for the evaluation of
D 5266 Practice for Estimating the Percentage of Wood
adhesives as a component of laminated wood products at
Failure in Adhesive Bonded Joints
elevated temperatures. The evaluation of fire performance on
D 5456 Specification for Evaluation of Structural Compos-
fire-rated laminated wood products or assemblies is beyond the
ite Lumber Products
scope of this test method.
2.2 Other Documents:
1.4 While it is preferable to use solid wood specimens as
ANSI/AITCA190.1 American National Standard for Wood
described in Section 6 as the control, structural composite
Products — Structural Glued Laminated Timber
lumber products as defined in Specification D 5456 shall be
ANSI/AF&PANDS-2005 National Design — Specification
permitted for use provided they are matched with the bonded
for Wood Construction (NDS)
specimens in accordance with Section 6 and the ignition
Wood Handbook Wood as an Engineering Material
temperature is not significantly lower than solid wood of the
same species.
3. Terminology
1.5 The exact formulation of adhesive supplied to the
3.1 Definitions:
manufacturer of laminated wood products shall be evaluated.
3.1.1 Many terms in this test method are defined in Termi-
Modifications to the adhesive formulation require a separate
nology D 907.
evaluation unless approved by the manufacturer of the lami-
nated wood product, qualified agency, and code evaluation
agency.
1.6 The values stated in SI units are to be regarded as the
standard. The values given in parentheses are for information
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
only.
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.
1 3
This test method is under the jurisdiction of ASTM Committee D14 on Available from American Institute of Timber Construction (AITC), 7012 S.
Adhesives and is the direct responsibility of Subcommittee D14.30 on Wood Revere Parkway, Suite 140, Centennial, CO 80112.
Adhesives. AvailablefromU.S.DepartmentofAgriculture,ForestService,ForestProducts
Current edition approved June 15, 2006. Published July 2006. Laboratory, One Gifford Pinchot Drive Madison, Wisconsin 53726.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7247–06
4. Significance and Use A190.1 shall be permitted to be grouped for the purpose of this
test method. Nominal 2-in. thick lumber shall be used to
4.1 A discussion of the issues associated with the measure-
manufacture the test specimens. The lumber shall have the
ment of strength properties of adhesive bonds in shear by
annual growth rings oriented 45 to 90°, as measured from the
compression loading is found in Test Method D 905.
wide face (vertical grain), and be free of defects and at the
4.2 Whilevariouscombinationsoftesttemperatureandheat
equilibrium moisture content recommended by the manufac-
exposuredurationcanbeused,theprovisionsspecifiedin7.2.4
shall be based on the understanding that the objective of this turer of the adhesive. If no such recommendation exists, the
test method is to evaluate adhesive bond performance just moisture content shall be between 10 and 12 % prior to
before wood begins to burn and the elevated temperature is
bonding following the moisture conditioning procedures de-
selected to be slightly below the unpiloted ignition temperature
scribed in Guide D 4933. Each piece of lumber used as part of
for wood when taken into account the specific product and its
this test method shall have a specific gravity equal to or
end-use applications.
exceeding the value specified in the National Design Specifi-
4.3 When using this test method, consideration shall be
cation for Wood Construction (NDS) for the wood species, as
given to the unique production conditions, such as wood
determined in accordance with Test Methods D 2395 based on
moisture content, applied spread rate, press pressure, and
oven-dry weight and volume. The specific gravity determina-
curing temperature of the adhesive.
tion for each piece of lumber shall be permitted to be
conducted on the ends trimmed from the lumber during the
5. Apparatus
preparation of the bonded and solid wood test specimens.
5.1 The testing machine and shearing tool described in Test
6.2 Specimens shall be prepared in accordance with the
Method D 905 have been found to be satisfactory for the test
general principle of Test Method D 905. To ensure that pieces
method described herein.
with similar specific gravity are bonded together, a single piece
5.2 An oven capable of maintaining 232 6 3°C (450 6
of the nominal 2 in. thick lumber shall provide, at a minimum,
5.4°F) with sufficient air circulation to maintain constant
the two pieces (lumber) necessary for each bonded specimen
temperature conditions within the oven interior is required for
and a side-matched solid wood (control) specimen. An ex-
heating the specimens.
ample of the shear specimen-cutting pattern is shown in Fig. 1.
5.3 Thermometers/thermocouples capable of measuring the
Care shall be exercised to ensure the same annual ring
temperature of the test specimen and air are required.
orientation when bonding the lumber together into a bonded
NOTE 1—Type “K” 24 gauge thermocouples are recommended.
assembly. The side-matched pairs of bonded and solid wood
6. Test Specimen control specimens shall have similar specific gravity.
6.3 The mating surfaces of the lumber used to prepare the
6.1 The wood species used for the tests shall be the wood
species used in commercial production. Wood species with bonded specimens shall be surfaced, no more than 24 h, prior
similar bonding characteristics in accordance withANSI/AITC to bonding. The adhesive preparation, spread rate, clamping
FIG. 1 Example of Side-Matched Specimen Fabrication (Using Nominal 2 by 6 in. Lumber with Bonded Specimens and Side-Matched
Solid Wood Control Specimens)
D7247–06
pressure, and clamping time shall follow the adhesive manu-
facturer’s recommendations. The production conditions for the
end-use products shall also be considered (see 4.3).
6.4 A minimum of 20 bonded specimens shall be prepared
in accordance with Fig. 2. The bonded specimens will have a
thickness less than the specified 38 mm (1.5 in.) as described
in Test Method D 905 due to surfacing from nominal 2-in
lumber. In addition, a minimum of 20 solid wood (without the
bondline) control specimens side-matched with the bonded
specimens shall be prepared, as shown in Fig. 1. The side-
matched solid wood specimens shall be surfaced to the same
thickness as the bonded specimens. The bonded and matched
solid wood control specimens shall be prepared as 20 pairs.
6.5 A total of 10 pairs of bonded and matched solid wood
FIG. 3 Top View (Left) and Side View (Right) of Drilled Hole for
control specimens shall be tested at ambient temperature and
Thermocouple Placement
the remaining 10 pairs of bonded and matched solid wood
control specimens shall be tested at the targeted elevated
thewoodadherendsothatthespecimenweightreductionduringtestingin
temperature.
accordance with Section 7 is primarily due to thermal degradation.
6.6 For specimens tested at the elevated temperature, a hole
6.9 After cooling, the specimen weight shall be determined.
shall be drilled through one lamination at a 90° angle to the
The width and length of the test specimen shall be measured
bondline and reaching to within 1.6 mm ( ⁄16 in.) of the
and recorded, at the bondline, to the nearest 0.25 mm (0.010
bondline. The drilled hole shall allow the thermocouple wire
in.) to determine the shear area. Test specimens are to be kept
casing to fit snugly inside the hole (see Fig. 3), with the
in the desiccator until just prior to testing in accordance with
exposed portion of the thermocouple wire touching the bond-
Section 7.
line of the bonded specimen or the geometric center (shear
plane) of the matched solid wood control specimen. The tip of
7. Test Procedures
the thermocouple wire shall have a maximum of 1 mm (0.040
7.1 Specimens Tested at Ambient Condition:
in.) of insulation removed.
7.1.1 A sample set consisting of 10 solid wood control
NOTE 2—Experience has shown that stripping the wire insulation
specimens and 10 bonded specimens shall be tested at standard
approximately 12.7 mm (0.5 in.), twisting the wires together, and cutting
laboratory conditions in accordance with the procedures out-
the exposed wire back to 1 mm (0.040 in.) gives consistent results.
lined in Test Method D 905. Loads shall be applied with a
Damage-to or improper-removal-of thermocouple wire insulation in-
continuous motion of the movable head at a rate of 5 mm (0.20
creases the possibility of inaccurate temperature readings in the oven.
Prior to re-using thermocouple wire, it is to be re-tested to ensure that in.)/min until failure.The ultimate load shall be recorded along
accurate temperature readings are being provided.
with an estimation of wood failure (to the nearest 5 %) in
accordance with Practice D 5266.
6.7 Thewidthandlengthofthespecimenshallbemeasured,
7.2 Specimens Tested at Elevated Temperature:
at the bondline, to the nearest 0.25 mm (0.010 in.) to determine
7.2.1 The oven shall be preheated to the targeted tempera-
the shear area, prior to subjecting the specimen to the targeted
ture using a thermocouple to monitor the interior oven tem-
temperature.
perature. The oven air temperature shall be held at the desired
6.8 All specimens shall be oven dried for 24 h at 103 6 6°C
level for a sufficient amount of time to heat all of the
(217 6 11°F) and placed in an atmosphere, such as a
components of the oven to the targeted temperature.
desiccator, to allow for cooling in dry conditions.
7.2.2 Only one specimen, either one solid wood control
NOTE 3—The intent of the oven drying is to remove the moisture from
specimen or one side-matched bonded specimen, shall be
placed in the oven at a time. A thermocouple wire shall be
placed into the specimen, as described in 6.6 and shown in Fig.
3. The drilled hole shall be backfilled, if necessary, with glass
insulation, high temperature silicon, or a similar protective
barrier. The backfill materials shall be allowed to cure accord-
ing to the manufacturer’s recommendations prior to testing.
The starting time and specimen oven-dry weight, after the
backfill materials are cured, as applicable, shall be recorded.
7.2.3 The bondline temperature of the bonded specimen or
the temperature at the shear plane of the matched solid wood
control specimen shall be monitored. Because of the insulating
nature of wood, the bondline temperature may be different
from the oven air temperature and thus the targeted tempera-
ture. Therefore, as the specimen approaches the targeted
FIG. 2 Form and Dimensions of a Bonded Specimen temperature, the rate of heating shall be slowed to a rate that
D7247–06
f 5 P/A (1)
can be easily controlled either manually or by using a propor-
v
tional temperature controller with an integral and derivative
(PID) control algorithm. The amount of time for the specimen
to reach the targeted temperature shall not be less than 30 min. where,
f = shear strength, MPa (or psi),
nor more than 90 min.
v
P = load at failure, N (or lbf), and
2 2
NOTE 4—When a manually controlled oven is used, previous studies
A = shear area of the specimen, mm (or in. ).
have shown that for a targeted temperature of 232°C (450°F), the heat
8.2 The shear strength of each specimen shall be reported.
should be turned down when the interior temperatures of the specimens
8.3 The specimen weight loss ratio, which is the specimen
reach approximately 210°C (410°F). The bondline temperature will
weight after testing divided by the specimen oven-dry weight
continue to rise, but the rate of increase will decrease. As the rate of
prior to Section 7 test procedures, shall be calculated and
temperature rise decreases, heat can be re-introduced, if necessary, to
attain the targeted bondline temperature. Practice runs with “dummy” reported.
specimens are recommended before the collection of actual data. The use
8.4 The residual shear strength ratio for the bonded and
of a PID device may help the temperature control.
solid wood control specimens shall be calculated separately in
accordance with Eq 2.
7.2.4 The time when the bondline temperature of the
bonded specimen or the temperature at the shear plane of the f
v,e
R 5 (2)
f
matched solid wood control specimen reaches the targeted
v,a
temperatur
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.