ASTM D4680-98(2023)
(Test Method)Standard Test Method for Creep and Time to Failure of Adhesives in Static Shear by Compression Loading (Wood-to-Wood)
Standard Test Method for Creep and Time to Failure of Adhesives in Static Shear by Compression Loading (Wood-to-Wood)
SIGNIFICANCE AND USE
4.1 Creep data that are obtained over a relatively short period of time in this test method can provide a measure of an adhesive bond's ability to withstand static loading in shear over a relatively long period of time. Creep measurements are made over a range of expected service conditions, including level of stress, temperature, relative humidity, and duration of load. Creep rate, creep strain, and creep modulus are calculated at the various service conditions.
4.2 Creep data can be used to (1) predict performance of an adhesive under long-term loading, (2) characterize an adhesive, (3) compare adhesives with each other and against specifications, and (4) design structural members fabricated with an adhesive.
4.3 Time-to-failure data provide a measure of the ultimate load-carrying ability of an adhesive bond as a function of time at various levels of stress, temperature, and relative humidity.
4.4 With proper caution, time-to-failure data derived from relatively short loading periods can be extrapolated to estimate the useful service life of an adhesive at working levels of static stress. This property may also be used with creep data to accomplish purposes listed in 4.2.
4.5 This test method is a research tool intended for development or evaluation of new adhesives and new product designs. The researcher may select from suggested tests those that are appropriate. However, creep and time-to-failure tests are nonroutine and can be time-consuming and expensive, so tests must be selected with care.
4.6 The apparatus and procedures may be suitable for measuring creep properties of adhesives on substrates other than wood, such as metal, plastic, and glass, but such considerations are not within the scope of this test method.
SCOPE
1.1 This test method covers the determination of time-dependent properties of structural adhesives in wood-to-wood bonds when specimens are subjected to shearing stresses at various levels of static load, constant temperature, and relative humidity. Apparatus and procedures are provided for direct measurement of time-dependent shear deformation (creep) and time to failure of adhesive bonds under static load. Guidelines for selecting test conditions, methods for calculating creep rate, creep strain, creep modulus, and extrapolation of time to failure, are given along with methods of presenting these data.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 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.
General Information
Relations
Standards Content (Sample)
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.
Designation: D4680 − 98 (Reapproved 2023)
Standard Test Method for
Creep and Time to Failure of Adhesives in Static Shear by
Compression Loading (Wood-to-Wood)
This standard is issued under the fixed designation D4680; 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 D907 Terminology of Adhesives
D2016 Methods of Test for Moisture Content of Wood
1.1 This test method covers the determination of time-
(Withdrawn 1987)
dependent properties of structural adhesives in wood-to-wood
2.2 ASTM Adjuncts:
bonds when specimens are subjected to shearing stresses at
Compression-Shear Creep Test Apparatus
various levels of static load, constant temperature, and relative
humidity. Apparatus and procedures are provided for direct
3. Terminology
measurement of time-dependent shear deformation (creep) and
3.1 Definitions:
time to failure of adhesive bonds under static load. Guidelines
3.1.1 Many terms in these test methods are defined in
for selecting test conditions, methods for calculating creep rate,
Terminology D907.
creep strain, creep modulus, and extrapolation of time to
3.1.2 creep, n—the dimensional change with time of a
failure, are given along with methods of presenting these data.
material under load, following the initial instantaneous elastic
1.2 The values stated in inch-pound units are to be regarded
or rapid deformation. Creep at room temperature is sometimes
as standard. The values given in parentheses are mathematical
called cold flow.
conversions to SI units that are provided for information only
3.1.3 creep modulus, n—the ratio of initial applied stress to
and are not considered standard.
creep strain.
1.3 This standard does not purport to address all of the
3.1.4 creep strain, n—the total strain, at any given time,
safety concerns, if any, associated with its use. It is the
produced by the applied stress during a creep test.
responsibility of the user of this standard to establish appro-
3.1.4.1 Discussion—In this test method, creep strain is
priate safety, health, and environmental practices and deter-
calculated by dividing displacement at any given time by the
mine the applicability of regulatory limitations prior to use.
estimated apparent thickness of the adhesive bondline.
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard-
3.1.5 rate of creep, n—the slope of the creep-time curve at
ization established in the Decision on Principles for the
a given time.
Development of International Standards, Guides and Recom-
3.1.6 shear stress, n—the stress component tangential to the
mendations issued by the World Trade Organization Technical
plane on which the forces act, that is, in the plane of the bond
Barriers to Trade (TBT) Committee.
line.
3.1.7 strain, n—the unit change, due to stress, in the size or
2. Referenced Documents
shape of a body referred to its original size or shape.
2.1 ASTM Standards:
3.1.8 stress, n—the force exerted per unit area at a point
D143 Test Methods for Small Clear Specimens of Timber
within the plane.
D905 Test Method for Strength Properties of Adhesive
Bonds in Shear by Compression Loading
4. Significance and Use
4.1 Creep data that are obtained over a relatively short
This test method is under the jurisdiction of ASTM Committee D14 on
period of time in this test method can provide a measure of an
Adhesives and is the direct responsibility of Subcommittee D14.30 on Wood
adhesive bond’s ability to withstand static loading in shear over
Adhesives.
a relatively long period of time. Creep measurements are made
Current edition approved May 1, 2023. Published May 2023. Originally
approved in 1987. Last previous edition approved in 2017 as D4680 – 98 (2017).
DOI: 10.1520/D4680-98R23.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or The last approved version of this historical standard is referenced on
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM www.astm.org.
Standards volume information, refer to the standard’s Document Summary page on Available from ASTM International Headquarters. Order Adjunct No.
the ASTM website. ADJD4680. Original adjunct produced in 1987.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4680 − 98 (2023)
over a range of expected service conditions, including level of apparatus, with included specimen, be preconditioned to the
stress, temperature, relative humidity, and duration of load. test temperature before the test load is applied to the spring.
Creep rate, creep strain, and creep modulus are calculated at The preheated apparatus must be wrapped with a piece of
the various service conditions. flexible thermal insulation material while the test load is
applied to the specimen. After loading and measurements,
4.2 Creep data can be used to (1) predict performance of an
return the loaded apparatus to the test environment. Since there
adhesive under long-term loading, (2) characterize an adhesive,
are no significant changes in temperature before or after
(3) compare adhesives with each other and against
loading, no adjustments are needed in the spring.
specifications, and (4) design structural members fabricated
5.3.2 The creep-test apparatus is made of corrosion-resistant
with an adhesive.
components so that it can be used in high-temperature and
4.3 Time-to-failure data provide a measure of the ultimate
humid environments for prolonged periods without concern for
load-carrying ability of an adhesive bond as a function of time
damaging the apparatus or interfering with the effectiveness of
at various levels of stress, temperature, and relative humidity.
the test.
4.4 With proper caution, time-to-failure data derived from
5.3.3 The creep-test apparatus has been compactly designed
relatively short loading periods can be extrapolated to estimate
with its load-applying mechanism built-in. Thus, several of the
the useful service life of an adhesive at working levels of static
units may be stacked on racks in a small environmental
stress. This property may also be used with creep data to
chamber such as an oven, incubator, or humidity cabinet. The
accomplish purposes listed in 4.2.
apparatus may be transferred from one exposure chamber to
another, or may be removed from an exposure chamber for
4.5 This test method is a research tool intended for devel-
measurements without disturbing the specimen under static
opment or evaluation of new adhesives and new product
load.
designs. The researcher may select from suggested tests those
5.3.4 The creep-test apparatus shown in Fig. 1 has a
that are appropriate. However, creep and time-to-failure tests
microswitch mounted at its base which is activated when the
are nonroutine and can be time-consuming and expensive, so
creep specimen fails. A small pin is located in the lower
tests must be selected with care.
specimen seat which is driven against the microswitch when
4.6 The apparatus and procedures may be suitable for
the failed specimen strikes it. The microswitch must be
measuring creep properties of adhesives on substrates other
connected to an automatic timer-recorder.
than wood, such as metal, plastic, and glass, but such consid-
5.4 Automatic Timer-Recorder—If creep or time-to-failure
erations are not within the scope of this test method.
measurements are to be made, an automatic and multi-channel
5. Apparatus
timer-recorder is connected to the microswitch on each creep-
test apparatus. The timer-recorder is capable of automatically
5.1 Testing Machine—A testing machine, or other suitable
scanning the several connected circuits at selected intervals of
loading machine, capable of applying compression loads from
time. When the creep specimen fails and activates the
0 lbf to 5000 lbf (22 kN) and cross-head speeds from 0.01 in-
microswitch, the timer-recorder automatically records the time
. ⁄min to 0.40 in./min (0.3 mm ⁄min to 10.2 mm/min) is suffi-
at which the circuit is broken.
cient for this test method. A minimum vertical space of 20 in.
(508 mm) is required to compress the loading spring in the
5.5 Microscope—A microscope is required to measure dis-
creep-test apparatus.
placement of scribe marks across the two adherends of a
specimen as creep occurs. Accurate measurements are also
5.2 Compression Shearing Tool—The testing machine is
required for bondline thicknesses. Make measurements to the
equipped with a shearing tool capable of applying a uniformly
nearest 0.001 mm (0.0004 in.). A linear traveling binocular
distributed compression load to the loading ledges of the
microscope is ideally suited to creep measurements; however,
block-shear specimen. A shearing tool equipped with a self-
a microscope fitted with an appropriately graduated scale is
aligning seat in the shearing blade ensures uniform loading.
satisfactory. An objective lens of at least 7× magnification is
5.3 Creep-Test Apparatus—Static loads shall be applied and
required.
maintained on block-shear specimens by means of the
5,4
5.6 Environmental Chambers—Control of temperature and
compression-loaded creep-test cylinder shown in Fig. 1. The
relative humidity is required in creep tests of adhesive bonds
apparatus is spring-loaded and can sustain any load up to the
on wood substrates. Temperature has a profound effect on
design capacity of the spring. This particular spring has a
creep properties of adhesives. Humidity also affects creep of
design load of 2300 lbf (10 kN); however, others of greater or
certain adhesives, but it can also affect dimensional change in
less capacity may be substituted. Varying spring capacities
wood adherends. Conditioning equipment should be capable of
with outside diameters no greater than the cylinder inside
maintaining a constant temperature within 63.0 °F (61.7 °C)
diameter are available.
of the set-point and constant relative humidity within 65 % of
5.3.1 For creep tests above room temperature, it is not
the set-point at a given temperature.
necessary to adjust the spring or load to compensate for the
effects of changing temperature. It is only necessary that the
6. Materials
6.1 Adherends—Select sugar maple (Acer saccharum) as the
This creep-test apparatus may be purchased from Hull Machine Shop, P.O. 373,
Hull, GA 30646, or other suitable suppliers. standard adherend material with the grain of the wood straight
D4680 − 98 (2023)
FIG. 1 Creep Test Apparatus
and parallel to the direction of shear and free of all defects such 6.1.2 Any other species of wood may be used as adherend
as knots, splits, and discolorations. Sugar maple is a uniformly material, particularly in those cases where it is necessary to
textured and high-density wood preferred in creep tests be- know the creep behavior of an adhesive in contact with a
cause it is less likely to deform near the bondline or fail in the specific wood species. However, it should be recognized that
wood before the test is completed. woods that are less uniform in texture and lower in density than
6.1.1 Sugar maple adherend material has a minimum spe- sugar maple, are more likely to deform and fail prematurely.
cific gravity of 0.65 (based on oven-dry weight and volume). A 6.1.3 When conducting creep and time-to-failure tests, it is
method for selecting maple blocks at this specific gravity, important not to overload the adherend and cause deformation
including appropriate adjustments in specific gravity for vari- at the bondline or failure in the wood before the test is
ous moisture contents, is described in the Appendix of Test completed. As a guide to selecting maximum levels of stress, it
Method D905. If more complete procedures are required for is recommended that the load not exceed the average shear
refereed tests, specific gravity may be determined in accor- strength parallel-to-grain for the species of wood when ad-
dance with Section 116 of Test Methods D143. justed for any change in moisture content from 12 %. Average
D4680 − 98 (2023)
FIG. 2 Block-Shear Specimen for Creep and Time To Failure Tests
shear strengths at 12 % moisture content for sugar maple and Fig. 2. Use the test adhesive to bond the two hard maple
other species of wood are presented in Table 4-2 of the Wood adherends together. The shear area is 1.00 in. by 1.00 in.
6 2 2
Handbook. For moisture contents other than 12 %, it will be (2.54 cm by 2.54 cm), equalling 1.00 in. (6.45 cm ).
necessary to adjust shear strengths by the formula described in
7.2 The finished specimen for creep tests has well-defined
pp. 4-32 and 4-33 of the Wood Handbook.
scribe marks on each side of the specimen for measuring
6.1.4 Should premature failures occur in the wood after
displacement of the two adherends as creep takes place.
mean strength values have been adjusted for moisture content,
7.3 Scribe marks are not necessary for specimens intended
then the 5 % exclusion limit may be used to select the
maximum level of stress for a particular species of wood. The for the time-to-failure tests.
maximum level of stress S is determined by the follow-
max0.05
7.4 Number of Specimens:
ing equation:
7.4.1 Test at least ten specimens at each set of test
S 5 S 2 1.645~0.14S ! (1)
max0.05 m m conditions, that is, each combination of stress level,
temperature, and relative humidity, for either creep test or
where S is the mean shear strength parallel-to-grain as
m
time-to-failure test. It is suggested that at least one test joint
presented in Table 4-2 of the Wood Handbook.
assembly (contains twelve specimens) be prepared for each
6.2 Adhesives—Creep properties of any adhesive can be
combination of test conditions.
measured on any species of wood as long as the level of shear
7.4.2 Randomly assign the ten specimens for each set of test
stress does not exceed the shear strength of the wood in the
conditions to that set from the entire lot of specimens prepared
specimen.
for testing of a given adhesive.
7.4.3 For many adhesives, measured creep properties will
7. Test Specimens
be highly variable, and ten specimens may not be a large
7.1 The standard specimen for both creep and time-to-
enough sample to give a high degree of confidence to the mean
failure tests shall be the block-shear specimen illus
...
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