ASTM D3433-99

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Designation: D 3433 – 99
Standard Test Method for
Fracture Strength in Cleavage of Adhesives in Bonded Metal
Joints
This standard is issued under the fixed designation D3433; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope B265 Specification for Titanium and TitaniumAlloy Strip,
2 Sheet, and Plate
1.1 Thistestmethod (1, 2, 5, 6, 9) coversthedetermination
D907 Terminology of Adhesives
of fracture strength in cleavage of adhesives when tested on
E4 Practices for Force Verification of Testing Machines
standard specimens and under specified conditions of prepara-
E399 Test Method for Plane-Strain Fracture Toughness of
tion and testing (Note 1).
Metallic Materials
1.2 This test method is useful in that it can be used to
develop design parameters for bonded assemblies.
3. Terminology
NOTE 1—While this test method is intended for use in metal-to-metal
3.1 Definitions: Many of the terms used in this test method
applications it may be used for measuring fracture properties of adhesives
are defined in Terminology D907.
using plastic adherends, provided consideration is given to the thickness
3.2 Definitions of Terms Specific to This Standard:
and rigidity of the plastic adherends.
3.2.1 crack-extension force, G,—the system isolated (fixed
1.3 The values stated in SI units are considered to be the
load-displacement) loss of stress field energy for an infinitesi-
standard. Values in parentheses are for information purposes.
mal increase, d A, of separational area. In equation form,
1.4 This standard does not purport to address all of the
GdA52dU (1)
T
safety concerns, if any, associated with its use. It is the
where U 5totalelasticenergyinthesystem(componentor
responsibility of the user of this standard to establish appro-
T
test specimen). In the test specimens of this method, the crack
priate safety and health practices and determine the applica-
front is nearly straight through the specimen thickness, B, so
bility of regulatory limitations prior to use.
thatdA 5 Bda,wheredaisaninfinitesimalforwardmotionof
2. Referenced Documents
the leading edge of the crack. Completely linear-elastic behav-
ior is assumed in the calculations (SeeAnnexA1) of G used in
2.1 ASTM Standards:
A 167 Specification for Stainless and Heat-Resisting this method, an allowable assumption when the zone of
nonlinear deformation in the adhesive is small relative to
Chromium-Nickel Steel Plate, Sheet, and Strip
A366/A366M SpecificationforSteel,Sheet,Carbon,Cold- specimen dimensions and crack size.
3.2.1.1 When the shear stress on the plane of crack and
Rolled, Commercial Quality
B36 Specification for Brass Plate, Sheet, Strip, and Rolled forward to its leading edge is zero, the stress state is termed
“opening mode.” The symbol for an opening mode G is G for
Bar
I
B152 Specification for Copper Sheet, Strip, Plate, and plane-strain and G when the connotation of plane-strain is not
wanted.
Rolled Bar
B209 Specification for Aluminum and Aluminum-Alloy 3.2.2 opening mode fracture toughness, G —thevalueof G
1c
justpriortoonsetofrapidfracturingwhen Gisincreasingwith
Sheet and Plate
time.
3.2.3 opening mode crack arrest toughness, G —thevalue
1a
This test method is under the jurisdiction of ASTM Committee D-14 on
of Gjustafterarrestofarun-arrestsegmentofcrackextension.
Adhesives and is the direct responsibility of Subcommittee D14.80 on Metal
3.2.3.1 It is assumed that the dimensions of the part con-
Bonding Adhesives.
taining the crack are large compared to the run-arrest segment
Current edition approved May 10, 1999. Published August 1999. Originally
published as D3433–75. Last previous edition D3433–93.
The boldface numbers in parentheses refer to the references at the end of this
test method.
3 6
Annual Book of ASTM Standards, Vol 01.03. Annual Book of ASTM Standards, Vol 02.04.
4 7
Annual Book of ASTM Standards, Vol 02.01. Annual Book of ASTM Standards, Vol 15.06.
5 8
Annual Book of ASTM Standards, Vol 02.02. Annual Book of ASTM Standards, Vol 03.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 3433
whichprecedescrackarrestandthatthequasi-staticstressfield would be expected. Background information concerning the
enclosingthecracktipjustaftercrackarrestcanbeassumedin basis for development of this test method in terms of linear
calculating G . elastic fracture mechanics may be found in Refs (6) and (7).
1a
5.1.1 Cyclic loads can cause crack extension at G values
4. Summary of Test Method less than G value. Furthermore, progressive stable crack
1c
extension under cyclic or sustained load may be promoted by
4.1 This test method involves cleavage testing bonded
the presence of certain environments.Therefore, application of
specimenssuchthatacrackismadetoextendbyatensileforce
G in the design of service components should be made with
1c
acting in a direction normal to the crack surface.
awareness of the G increase for a prior crack which may occur
4.2 Load versus load-displacement across the bondline is
in service due to slow-stable crack-extension.
recorded autographically. The G and G values are calcu-
1c 1a
5.2 This test method can serve the following purposes:
lated from this load by equations that have been established on
5.2.1 In research and development to establish, in quantita-
the basis of elastic stress analysis of specimens of the type
tive terms, significant to service performance, the effects of
described below. The validity of the determination of G and
1c
adhesive composition, primers, adherend surface treatments,
G values by this test method depends upon the establishment
1a
supporting adhesive carriers (scrim), processing variables, and
of a sharp-crack condition in the bondline in a specimen of
environmental effects.
adequate size. This test method will measure the fracture
5.2.2 In service evaluation to establish the suitability of an
strength of a bonded joint which is influenced by adherend
adhesive system for a specific application for which the stress
surface condition, adhesive, adhesive-adherend interactions,
conditions are prescribed and for which maximum flaw sizes
primers, adhesive-supporting scrims, etc., and in which of the
can be established with confidence.
above possible areas the crack grows.
5.2.3 For specifications of acceptance and manufacturing
quality control, but only when there is a sound basis for
5. Significance and Use
specification of minimum G values. The specification of G
1c 1c
NOTE 2—Crackgrowthinadhesivebondspecimenscanproceedintwo
values in relation to a particular application should signify that
ways: (1) by a slow-stable extension where the crack velocity is dictated
a fracture control study has been conducted on the component
by the crosshead rate or (2) by a run-arrest extension where the stationary
in relation to the expected history of loading and environment,
crack abruptly jumps ahead outrunning the crosshead-predicted rate. The
and in relation to the sensitivity and reliability of the crack
first type of crack extension is denoted flat; the second type peaked
because of the appearance of the autographic record. The flat behavior is
detection procedures that are to be applied prior to service and
characteristic of adhesives or test temperatures, or both, for these
subsequently during the anticipated life.
adhesives where there is no difference between initiation, G , and arrest,
1c
G . For example, the rubber modified film adhesives tested
1a
6. Apparatus
above−17.8°C (0°F) all exhibit flat autographic records. Peaked curves
are exhibited for all modified materials tested below−73°C (−100°F) and 6.1 Testing Machine, conforming to the requirements of
in general for unmodified epoxies.
PracticesE4.Selectthetestingmachinesuchthatthecracking
It should be noted that both peaked and flat behaviors are determined
load of the specimens falls between 15 and 85% of the
from a crack-length-independent specimen. For other specimens or
full-scale capacity and that is provided with a suitable pair of
structures where G increases with a at constant load the onset of crack
self-aligning pinned fixtures to hold the specimen.
growth would result in rapid complete fracturing whatever the adhesive
6.2 Ensure that the pinned fixtures and attachments are
characteristics.
constructed such that they will move into alignment with the
5.1 The property G (and G if relevant) determined by
1c 1a
test specimen as soon as the load is applied.
this test method characterizes the resistance of a material to
6.3 For a discussion of the calculation of separation rates
slow-stable or run-arrest fracturing in a neutral environment in
see Annex A1.
the presence of a sharp crack under severe tensile constraint,
such that the state of stress near the crack front approaches
7. Test Specimens
tritensile plane strain, and the crack-tip plastic region is small
compared with the crack size and specimen dimensions in the 7.1 Flat Adherend, conforming to the form and dimensions
constraint direction. It has not been proven that tough adhesive shown in Fig. 1, cut from test joints as in Fig. 2, prepared as
systems fully meet this criteria. Therefore, data developed prescribed in Section 8.
using equations based on this assumption may not represent 7.2 Contoured Double-Cantilever Beam (CDCB), conform-
plane-strain fracture values. Comparison of fracture toughness ing to the form and dimensions shown in Fig. 3.
between adhesive systems widely different in brittleness or 7.3 Thefollowinggradesofmetalsaresuggestedforthetest
toughness should take this into consideration. In general,
specimens (Note 3):
systems of similar type toughness (3, 4, 7, 8, 10) can be
Metal ASTM Designation
Brass B 36, Alloy 260 (6), quarter hard temper
compared as can the effect of environment on toughness of a
Copper B 152, cold rolled, Type 110, hard temper
single system. A G value is believed to represent a lower
1c
Aluminum B 209, Alclad 2024, T3 temper, mill finish
limiting value of fracture toughness for a given temperature,
Steel A 366, regular matte finish
Corrosion-resisting steel A 167, Type 304, No. 2B finish
strainrate,andadhesiveconditionasdefinedbymanufacturing
Titanium B 265, Grade 3
variables. This value may be used to estimate the relation
between failure stress and defect size for a material in service 7.4 Test at least twelve specimens, representing at least four
wherein the conditions of high constraint described above different joints.
D 3433
FIG. 1 Flat Adherend Specimen
FIG. 2 Test Joint
NOTE 3—Since it is unacceptable to exceed the yield point of the metal
procedure prescribed by the manufacturer of the adhesive.
in flexure during test, the permissible thickness of the specimen will vary
Prepare and apply the adhesive in accordance with the recom-
with type of metal, and the general level of strength of the adhesive being
mendations of the manufacturer of the adhesive. Apply the
investigated. The minimum permissible thickness in a uniform symmetri-
adhesivetothefayingsurfaceofoneorbothmetalsheets.Then
cal adherend may be computed from the following relationship:
assemble the sheets, faying surface to faying surface in pairs,
6 Ta
and allow the adhesive to cure under conditions prescribed by
h 5 (2)
Œ
BF
ty
the manufacturer of the adhesive.
8.2 Itisrecommendedthateach“flatadherend”testjointbe
where:
madewithsufficientareatoprovideatleastfivetestspecimens.
h 5 thickness of metal normal to plane of bonding, mm (or in.),
F 5 tensile yield point of metal (or the stress at proportional limit)
ty
MPa (or psi),
9. Preparation of Test Specimens
T 5 150% of the maximum load to start the crack in the adhesive
9.1 For flat adherend test specimens, trim joint area in
bond, N (or lbf),
accordance with Fig. 2. Then cut test specimens, as shown in
a 5 crack length at maximum load, mm (or in.), and
B 5 bond width, mm (or in.).
Fig. 1, from the joints, Fig. 2 (Note 4). Then cut holes for load
pins as shown in Fig. 1.
8. Preparation of Test Joints
9.2 Contoured double-cantilever specimens are ready for
8.1 Cut sheets of the metals or contoured adherends pre- test as bonded.
scribedin7.1-7.3andtorecommendedsize(Figs.2and3).All
NOTE 4—Do not use lubricants or oils during the cutting process. For
edges of the metal panels and specimens must be flat, free of
aluminum it is suggested that the specimens be rough cut 3.2 mm ( ⁄8 in.)
burrs, and smooth (4.1-µm (160-µin.) maximum) before the
over-size using a four-pitch band saw traveling at approximately 4.2 m/s
panelsaresurface-treatedandbonded.Clean,treat,anddrythe
(800 ft/min) followed by finish dimensioning to a 1-in. wide 3.2-µm
sheetsorcontouredadherendscarefully,inaccordancewiththe (125-µin.) surface using a five-blade 15-deg carbide fly cutter at 1115 rpm
D 3433
FIG. 3 Contoured Double-Cantilever Beam Specimen
and 0.015 to 0.035-m/s (3 to 7-in./min) feed rate.
motion is represented on the abscissa (_) for each 100 mm (4
in.)ofordinatemotion(P).Forload-timerecordsachart speed
10. Procedure
rate should be used such that the slope of the load versus time
10.1 Test specimens, prepared as prescribed in Section 8, in
record is similar to that specified for load versus load-
an atmosphere maintained at 50 6 4% relative humidity and
displacement (for example, 5 mm/min (0.2 in./mm)).
23 6 1°C (73.4 6 1.8°F). Tests at other than ambient
10.4 Apply load to specimen until Point A is reached. (See
temperature may be run if desired. It is suggested that
Point A, Fig. 4 for flat adherend and Fig. 5, Point A for
specimens be conditioned for a minimum of 10 min and a
contoured double-cantilever specimen.) Point A is the load at
maximum of 30 min at the temperature of test to assure
which the crack begins to grow rapidly. Then stop loading and
equilibrium. The manufacturer of the adhesive may, however,
follow crack growth curve on the chart. When the load has
prescribe a definite period of conditioning under specific
leveled off at an approximate constant value (the crack has
conditions before testing.
stopped growing), determine and record the following values:
10.2 Determine the following test specimen dimensions.
10.4.1 Load to start crack, L (max), N (or lbf),
10.2.1 Distance from center of 6.4-mm (0.25-in.) inside-
10.4.2 Load when crack stops, L (min), N (or lbf), and
diameter pin holes to close end of specimen.
10.4.3 Distance from loading end of specimen to the sta-
10.2.2 Width of test specimen
...