ASTM D4680-98(2023)

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

• Status: Published
• Publication Date: 30-Apr-2023
• ICS: 83.180 - Adhesives
• Technical Committee: D14 - Adhesives
• Drafting Committee: D14.30 - Wood Adhesives

Relations

• Refers: ASTM D143-23 - Standard Test Methods for Small Clear Specimens of Timber
• Effective Date: 15-Nov-2023
• Refers: ASTM D2016-74(1983) - Methods of Test for Moisture Content of Wood (Withdrawn 1987)
• Effective Date: 29-Sep-2023
• Refers: ASTM D907-12a - Standard Terminology of Adhesives
• Effective Date: 01-Jul-2012
• Refers: ASTM D907-12 - Standard Terminology of Adhesives
• Effective Date: 01-May-2012
• Refers: ASTM D907-11a - Standard Terminology of Adhesives
• Effective Date: 01-Dec-2011
• Refers: ASTM D907-11 - Standard Terminology of Adhesives
• Effective Date: 01-Jan-2011
• Refers: ASTM D143-09 - Standard Test Methods for Small Clear Specimens of Timber
• Effective Date: 01-Sep-2009
• Refers: ASTM D905-08 - Standard Test Method for Strength Properties of Adhesive Bonds in Shear by Compression Loading
• Effective Date: 01-Oct-2008
• Refers: ASTM D907-08b - Standard Terminology of Adhesives
• Effective Date: 01-Oct-2008
• Refers: ASTM D905-08e1 - Standard Test Method for Strength Properties of Adhesive Bonds in Shear by Compression Loading
• Effective Date: 01-Oct-2008
• Refers: ASTM D907-08a - Standard Terminology of Adhesives
• Effective Date: 15-Aug-2008
• Refers: ASTM D907-08 - Standard Terminology of Adhesives
• Effective Date: 01-Mar-2008
• Refers: ASTM D143-94(2000)e1 - Standard Test Methods for Small Clear Specimens of Timber
• Effective Date: 10-Apr-2007
• Refers: ASTM D143-94(2007) - Standard Test Methods for Small Clear Specimens of Timber
• Effective Date: 01-Apr-2007
• Refers: ASTM D907-06 - Standard Terminology of Adhesives
• Effective Date: 01-Dec-2006

Overview

ASTM D4680-98(2023) is a widely recognized international standard published by ASTM International under the jurisdiction of ASTM Committee D14 on Adhesives. This standard outlines a test method for determining the creep and time to failure of adhesives in static shear by compression loading (wood-to-wood joints). It provides essential procedures and guidelines for evaluating how structural adhesives perform under sustained static loads, focusing on wood-to-wood bonded assemblies subjected to varying service conditions, such as stress levels, temperature, and relative humidity.

The standard is instrumental for predicting long-term adhesive performance, characterizing new or existing adhesives, comparing them against specifications, and informing the design of structural members utilizing adhesives.

Key Topics

• Creep Testing of Adhesives: Provides methodologies for measuring time-dependent shear deformation-creep-of adhesives under static loads. Creep rate, strain, and modulus are calculated at specified conditions.
• Time to Failure Analysis: Offers procedures for testing the ultimate load-bearing capacity of an adhesive joint over time at different stress, temperature, and humidity levels.
• Specimen Preparation and Conditioning: Covers the preparation of wood adherends, adhesive application, and conditioning requirements to ensure standardized baseline conditions.
• Test Apparatus and Procedure: Specifies the tools, loading machines, environmental chambers, and measurement techniques (including the use of scribe marks and microscopes) needed for accurate, reliable data.
• Data Reporting: Recommends comprehensive documentation of materials used, test conditions, procedures, and results to ensure reproducibility and traceability.

Applications

ASTM D4680-98(2023) is highly valuable for several industry sectors and research domains:

• Adhesive Research & Development: Supports material scientists and manufacturers in developing and evaluating new adhesive formulations and product designs by providing meaningful long-term performance data.
• Quality Control and Specification Compliance: Enables laboratories and manufacturing facilities to compare adhesives to industry or project specifications, ensuring reliability in end-use applications.
• Structural Design: Assists engineers and designers in selecting appropriate adhesives and safety factors for bonded wood components in buildings, furniture, or engineered wood products by predicting service life under static loads.
• Comparative Evaluation: Facilitates the benchmarking of multiple adhesives under identical conditions to establish relative performance.
• Extrapolation for Service Life Prediction: With appropriate caution, short-term test results can be extrapolated to estimate the long-term durability of wood-to-wood adhesive bonds.
• Environmental Testing: Provides guidance on assessing adhesive performance under varying environmental conditions, including high humidity and elevated temperatures, reflecting real-world service environments.

Although the apparatus and procedures may be adaptable for substrates like metal, plastic, or glass, this standard specifically addresses wood-to-wood bonds.

Related Standards

• ASTM D143: Test Methods for Small Clear Specimens of Timber-used for determining reference shear strengths of wood specimens.
• ASTM D905: Test Method for Strength Properties of Adhesive Bonds in Shear by Compression Loading-complements D4680 for evaluating ultimate adhesive joint strengths.
• ASTM D907: Terminology of Adhesives-provides definitions for terms and concepts used in adhesive testing.
• ASTM D2016: Methods of Test for Moisture Content of Wood-relevant for specimen conditioning procedures.

These related standards support a comprehensive framework for the testing and evaluation of wood adhesives under both short-term and extended service conditions.

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Keywords: ASTM D4680, adhesive creep, wood-to-wood adhesive, static shear testing, time-to-failure, adhesive bond testing, structural adhesives, adhesive durability, compression loading, environmental testing, long-term adhesive performance.

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 [e-mail]. 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 illustrated in
of a measured property. Creep tests generally are expensive
and time-consuming, and a specimen count of ten represents a
Wood Handbook: Wood As An Engineering Material, USDA Agriculture
practical compromise.
Handbook 72, rev., U.S. Forest Products Lab., 1974, Table 4-2 and p. 4-32 and 4-33.
7.4.4 If it is determined from experimental evidence that a
Available from U.S. Government Printing Office Superintendent of Documents, 732
N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401. reasonable degree of confidence can be given to a mean by
D4680 − 98 (2023)
using a lesser number of specimens, then it is permissible to the finished block-shear specimens to the standard atmosphere
use the lesser number. given in 8.1. Condition them there for 7 days to ensure that the
moisture content has stabilized before creep tests begin. If
8. Conditioning of Materials and Specimens
creep tests are to be conducted at equilibrium moisture
conditions other than those in 8.1, then subsequent condition-
8.1 Condition hard maple boards at 73 °F 6 3 °F (23 °C 6
ing will be required as described in 10.1.2.
1.7 °C) and 65 % 6 2 % relative humidity until they reach
moisture equilibrium (approximately 12 % moisture content), 9.4 Cut scribe marks along the two sides of each specimen
as indicated by no further significant changes in weight. Use
intended for creep tests. A sharp, single-edged razor blade
Test Methods D2016 for guidance to determine when equilib- makes well-defined marks. The marks extend in a straight line
rium has been reached. Other relative humidities may be
across, and perpendicular to the bondline and adherends.
substituted as long as (1) the wood reaches equilibrium Inspect the cuts with any microscope fitted with an objective
between 10 % and 12 % moisture content, (2) the alternative
lens of 7× magnification. If at least one edge of the cut is not
conditions are substituted consistently throughout the test clearly defined, then make another cut next to the first. Be sure
method, and (3) the substituted standard conditions are re-
to use the same cut edge every time measurements are made.
ported. If the facilities are not available for conditioning wood
to the 10 % to 12 % moisture content range, then lower relative
10. Procedure
humidities may be substituted to lower the equilibrium mois-
10.1 Creep Tests:
ture content of the wood to the 7 % to 9 % range. Conditions
10.1.1 Randomly select and assign at least ten specimens to
(2) and (3) above must apply to this substitution.
each set of test conditions from the total number of specimens
8.2 It is important that wood moisture content after precon-
that are to be used for the creep tests. Select an additional set
ditioning and during creep tests remain essentially the same.
of specimens to replace defective or mis-tested specimens.
Otherwise adherends will undergo dimensional changes with
10.1.2 Since creep specimens of wood undergo dimensional
moisture during static loading with the inevitable result that
changes with changes in environment, it is essential that
creep properties will be affected. The exposure environment for
specimens be preconditioned to, and in equilibrium with, those
creep tests shall be the same as indicated in 8.1, unless
test conditions at the time creep tests begin. If creep is to be
otherwise prescribed.
measured at conditions other than standard conditions in 8.1,
then condition specimens at those test conditions until speci-
NOTE 1—Guidelines for selecting test conditions are given in Annex
mens reach equilibrium moisture content (indicated by no
A1.
change in weight) and temperature.
9. Specimen Preparation 10.1.3 After specimens have been preconditioned, measure
the shear area of each creep specimen to the nearest 0.01 in.
9.1 Plane hard maple boards of specified specific gravity on
(0.25 mm) using a dial-indicating calipered micrometer. Cal-
both sides to a thickness of 0.63 in. (16 mm). If a planer is not
2 2
culate the shear area to the nearest 0.01 in. (0.06 cm ).
available, use a hand-fed jointer. Planing should be carried out
10.1.4 Measure bondline thickness at the four corners of the
no longer than 24 h before bonding. Cut the boards into blocks
shear area on each specimen to the nearest 0.0004 in.
12 in. long by 3 in. wide (30.5 cm by 7.6 cm). The grain
(0.001 mm) with a linear traveling microscope, or with a
direction shall be parallel to the long dimensions of the block.
microscope having a graduated scale. The bondline thickness
Keep the planed surfaces free of dust and dirt until they can be
for each specimen shall be the average of the four measure-
bonded.
ments.
9.2 Prepare the test adhesive and apply it to adherends in
10.1.5 If creep is to be determined for elevated
accordance with procedures recommended by the manufacturer
temperatures, but specimens have to be removed from test
of the adhesive. Since adhesives of different types may be
conditions for periodic measurements of creep, the creep test
tested by this method, no given set of spread rates, assembly
apparatus along with a properly seated specimen must be
times, clamp pressures, pressure times, and curing times, can
conditioned to equilibrium temperature before removal from
be specified to cover all adhesives. Normally, the adhesive
test conditions. Every effort should be made to maintain test
manufacturer describes procedures for making sound bonds
temperature when apparatus and specimen are removed for
and these should be carefully followed.
measurements. This can be accomplished by wrapping the
9.3 After proper curing, cut each test joint assembly into apparatus in a flexible thermal insulation material such as
twelve specimen blanks. The method of cutting specimens polyurethane f
...