ASTM D5045-14(2022)
(Test Method)Standard Test Methods for Plane-Strain Fracture Toughness and Strain Energy Release Rate of Plastic Materials
Standard Test Methods for Plane-Strain Fracture Toughness and Strain Energy Release Rate of Plastic Materials
SIGNIFICANCE AND USE
5.1 The property KIc (GIc) determined by these test methods characterizes the resistance of a material to fracture in a neutral environment in the presence of a sharp crack under severe tensile constraint, such that the state of stress near the crack front approaches plane strain, and the crack-tip plastic (or non-linear viscoelastic) region is small compared with the crack size and specimen dimensions in the constraint direction. A KIc value is believed to represent a lower limiting value of fracture toughness. This value has been used to estimate the relation between failure stress and defect size for a material in service wherein the conditions of high constraint described above would be expected. Background information concerning the basis for development of these test methods in terms of linear elastic fracture mechanics can be found in Refs (1-5).3
5.1.1 The KIc (GIc) value of a given material is a function of testing speed and temperature. Furthermore, cyclic loads have been found to cause crack extension at K values less than KIc (GIc). Crack extension under cyclic or sustained load will be increased by the presence of an aggressive environment. Therefore, application of KIc (GIc) in the design of service components should be made considering differences that may exist between laboratory tests and field conditions.
5.1.2 Plane-strain fracture toughness testing is unusual in that sometimes there is no advance assurance that a valid KIc (GIc) will be determined in a particular test. Therefore it is essential that all of the criteria concerning validity of results be carefully considered as described herein.
5.1.3 Clearly, it will not be possible to determine KIc (GIc) if any dimension of the available stock of a material is insufficient to provide a specimen of the required size.
5.2 Inasmuch as the fracture toughness of plastics is often dependent on specimen process history, that is, injection molded, extruded, compression molded, etc., the spe...
SCOPE
1.1 These test methods are designed to characterize the toughness of plastics in terms of the critical-stress-intensity factor, KIc, and the energy per unit area of crack surface or critical strain energy release rate, GIc, at fracture initiation.
1.2 Two testing geometries are covered by these test methods, single-edge-notch bending (SENB) and compact tension (CT).
1.3 The scheme used assumes linear elastic behavior of the cracked specimen, so certain restrictions on linearity of the load-displacement diagram are imposed.
1.4 A state-of-plane strain at the crack tip is required. Specimen thickness must be sufficient to ensure this stress state.
1.5 The crack must be sufficiently sharp to ensure that a minimum value of toughness is obtained.
1.6 The significance of these test methods and many conditions of testing are identical to those of Test Method E399, and, therefore, in most cases, appear here with many similarities to the metals standard. However, certain conditions and specifications not covered in Test Method E399, but important for plastics, are included.
1.7 This protocol covers the determination of GIc as well, which is of particular importance for plastics.
1.8 These test methods give general information concerning the requirements for KIc and GIc testing. As with Test Method E399, two annexes are provided which give the specific requirements for testing of the SENB and CT geometries.
1.9 Test data obtained by these test methods are relevant and appropriate for use in engineering design.
1.10 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.
Note 1: This standard and ISO 13586 address the same subject matter, but differ in technical con...
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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: D5045 − 14 (Reapproved 2022)
Standard Test Methods for
Plane-Strain Fracture Toughness and Strain Energy Release
Rate of Plastic Materials
This standard is issued under the fixed designation D5045; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.1 These test methods are designed to characterize the
toughness of plastics in terms of the critical-stress-intensity
NOTE1—ThisstandardandISO13586addressthesamesubjectmatter,
but differ in technical content.
factor, K , and the energy per unit area of crack surface or
Ic
critical strain energy release rate, G , at fracture initiation.
1.11 This international standard was developed in accor-
Ic
dance with internationally recognized principles on standard-
1.2 Two testing geometries are covered by these test
ization established in the Decision on Principles for the
methods, single-edge-notch bending (SENB) and compact
Development of International Standards, Guides and Recom-
tension (CT).
mendations issued by the World Trade Organization Technical
1.3 The scheme used assumes linear elastic behavior of the
Barriers to Trade (TBT) Committee.
cracked specimen, so certain restrictions on linearity of the
load-displacement diagram are imposed. 2. Referenced Documents
1.4 A state-of-plane strain at the crack tip is required. 2.1 ASTM Standards:
Specimen thickness must be sufficient to ensure this stress D638Test Method for Tensile Properties of Plastics
state. D4000Classification System for Specifying Plastic Materi-
als
1.5 The crack must be sufficiently sharp to ensure that a
E399Test Method for Linear-Elastic Plane-Strain Fracture
minimum value of toughness is obtained.
Toughness of Metallic Materials
1.6 The significance of these test methods and many con-
E691Practice for Conducting an Interlaboratory Study to
ditions of testing are identical to those of Test Method E399,
Determine the Precision of a Test Method
and, therefore, in most cases, appear here with many similari-
3. Terminology
ties to the metals standard. However, certain conditions and
specifications not covered in Test Method E399, but important
3.1 Definitions:
for plastics, are included.
3.1.1 compact tension, n—specimen geometry consisting of
single-edge notched plate loaded in tension. See 3.1.5 for
1.7 This protocol covers the determination of G as well,
Ic
reference to additional definition.
which is of particular importance for plastics.
3.1.2 critical strain energy release rate, G ,n—toughness
1.8 Thesetestmethodsgivegeneralinformationconcerning Ic
parameter based on energy required to fracture. See 3.1.5 for
the requirements for K and G testing. As with Test Method
Ic Ic
reference to additional definition.
E399, two annexes are provided which give the specific
requirements for testing of the SENB and CT geometries. 3.1.3 plane-strain fracture toughness, K ,n—toughness
Ic
parameter indicative of the resistance of a material to fracture.
1.9 Testdataobtainedbythesetestmethodsarerelevantand
See 3.1.5 for reference to additional definition.
appropriate for use in engineering design.
3.1.4 single-edge notched bend, n—specimen geometry
1.10 This standard does not purport to address all of the
consisting of center-notched beam loaded in three-point bend-
safety concerns, if any, associated with its use. It is the
ing. See 3.1.5 for reference to additional definition.
responsibility of the user of this standard to establish appro-
3.1.5 Reference is made toTest Method E399 for additional
explanation of definitions.
These test methods are under the jurisdiction of ASTM Committee D20 on
Plastics and is the direct responsibility of Subcommittee D20.10 on Mechanical
Properties. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2022. Published November 2022. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1990. Last previous edition approved in 2014 as D5045-14. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D5045-14R22. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5045 − 14 (2022)
3.2 Definitions of Terms Specific to This Standard: 5.2 Inasmuch as the fracture toughness of plastics is often
3.2.1 yield stress, n—stress at fracture is used. The slope of dependent on specimen process history, that is, injection
the stress-strain curve is not required to be zero. See 7.2 for molded, extruded, compression molded, etc., the specimen
reference to additional definition. crack orientation (parallel or perpendicular) relative to any
processing direction shall be noted on the report form dis-
4. Summary of Test Methods
cussed in 10.1.
4.1 These test methods involve loading a notched specimen
5.3 Before proceeding with this test method, reference
that has been pre-cracked, in either tension or three-point
shouldbemadetothespecificationofthematerialbeingtested.
bending. The load corresponding to a 2.5% apparent incre-
Any test specimen preparation, conditioning, dimensions, or
ment of crack extension is established by a specified deviation
testing parameters, or combination thereof, covered in the
from the linear portion of the record. The K value is
Ic
relevant ASTM materials specification shall take precedence
calculated from this load by equations that have been estab-
over those mentioned in this test method. If there are no
lishedonthebasisofelasticstressanalysisonspecimensofthe
relevantASTM material specifications, then the default condi-
type described in the test methods. The validity of the
tions apply.
determination of the K value by these test methods depends
Ic
6. Apparatus
upon the establishment of a sharp-crack condition at the tip of
the crack, in a specimen of adequate size to give linear elastic
6.1 Testing Machine—A constant displacement-rate device
behavior.
shall be used such as an electromechanical, screw-driven
4.2 Amethod for the determination of G is provided. The machine, or a closed loop, feedback-controlled servohydraulic
Ic
method requires determination of the energy derived from load frame. For SENB, a rig with either stationary or moving
integrationoftheloadversusload-pointdisplacementdiagram, rollers of sufficiently large diameter to avoid excessive plastic
while making a correction for indentation at the loading points indentation is required.Asuitable arrangement for loading the
as well as specimen compression and system compliance. SENB specimen is shown in Fig. 1. A loading clevis suitable
for loading compact tension specimens is shown in Fig. 2.
5. Significance and Use
Loading is by means of pins in the specimen holes (Fig. 3(b)).
5.1 ThepropertyK (G )determinedbythesetestmethods
Ic Ic 6.2 Displacement Measurement—An accurate displacement
characterizestheresistanceofamaterialtofractureinaneutral
measurement must be obtained to assure accuracy of the G
Ic
environment in the presence of a sharp crack under severe
value.
tensile constraint, such that the state of stress near the crack
6.2.1 Internal Displacement Transducer—For either SENB
front approaches plane strain, and the crack-tip plastic (or
orCTspecimenconfigurations,thedisplacementmeasurement
non-linear viscoelastic) region is small compared with the
shall be performed using the machine’s stroke (position)
cracksizeandspecimendimensionsintheconstraintdirection.
transducer. The fracture-test-displacement data must be cor-
A K value is believed to represent a lower limiting value of
Ic rected for system compliance, loading-pin penetration (brinel-
fracture toughness. This value has been used to estimate the
ling)andspecimencompressionbyperformingacalibrationof
relation between failure stress and defect size for a material in
the testing system as described in 9.2.
service wherein the conditions of high constraint described
6.2.2 ExternalDisplacementTransducer—Ifaninternaldis-
abovewouldbeexpected.Backgroundinformationconcerning
placement transducer is not available, or has insufficient
the basis for development of these test methods in terms of
precision, then an externally applied displacement-measuring
linear elastic fracture mechanics can be found in Refs (1-5).
device shall be used as illustrated in Fig. 1 for the SENB
5.1.1 TheK (G )valueofagivenmaterialisafunctionof
Ic Ic
configuration. For CT specimens, a clip gauge shall be
testing speed and temperature. Furthermore, cyclic loads have
been found to cause crack extension at K values less than K
Ic
(G ). Crack extension under cyclic or sustained load will be
Ic
increased by the presence of an aggressive environment.
Therefore, application of K (G ) in the design of service
Ic Ic
components should be made considering differences that may
exist between laboratory tests and field conditions.
5.1.2 Plane-strain fracture toughness testing is unusual in
that sometimes there is no advance assurance that a validK
Ic
(G ) will be determined in a particular test. Therefore it is
Ic
essentialthatallofthecriteriaconcerningvalidityofresultsbe
carefully considered as described herein.
5.1.3 Clearly,itwillnotbepossibletodetermineK (G )if
Ic Ic
any dimension of the available stock of a material is insuffi-
cient to provide a specimen of the required size.
The boldface numbers in parentheses refer to the list of references at the end of
these test methods. FIG. 1 Bending Rig with Transducer for SENB
D5045 − 14 (2022)
maximize this dimension. The specimen width, W,is W=2B.
In both geometries the crack length, a, shall be selected such
that 0.45 < a/W< 0.55.
7.1.2 In order for a result to be considered valid according
to these test methods, the following size criteria must be
satisfied:
B, a, ~W 2 a!.2.5 K /σ (1)
~ !
Q y
where:
K = the conditional or trial K value (see Section 9), and
Q Ic
σ = the yield stress of the material for the temperature and
y
loading rate of the test.
The criteria require that B must be sufficient to ensure plane
strain and that (W−a) be sufficient to avoid excessive plas-
ticity in the ligament. If (W−a) is too small and non-linearity
in loading occurs, then increasing the W/Bratio to a maximum
of 4 is permitted for SENB specimens.
7.2 Yield Stress:
7.2.1 The yield stress, σ , is to be taken from the maximum
y
FIG. 2 Tension Testing Clevis Design for CT
load in a uniaxial tensile test. The yield-stress test can be
performed in a constant stroke-rate uniaxial tensile test where
the loading time to yield is within 620% of the actual loading
time observed in the fracture test.The definition of yield stress
is not identical to that found in Test Method D638 which
requires a zero slope to the stress-strain curve. If it is
established that 2.5 (K /σ ) is substantially less than
Q y
the specimen thickness employed, then a correspondingly
smaller specimen can be used.
7.2.2 Yielding in tensile tests in most polymers can be
achieved by carefully polishing the specimen sides. If yielding
does not occur and brittle fracture is observed, the stress at
fracture shall be used in the criteria to give a conservative size
value.
7.2.3 If a tensile test cannot be performed, then an alterna-
tive method is to use 0.7 times the compressive yield stress.
7.2.4 If the form of the available material is such that it is
not possible to obtain a specimen with both crack length and
thickness greater than 2.5 (K /σ ) , it is not possible to make a
Ic y
valid K (G ) measurement according to these test methods.
Ic Ic
7.2.5 The test method employed for determining yield
stress, as mentioned in 7.2.1 – 7.2.4, must be reported.
7.3 Specimen Configurations:
7.3.1 Standard Specimens—The configurations of the two
FIG. 3 Specimen Configuration as in Test Method E399
geometries are shown in Fig. 3(a) (SENB) and Fig. 3(b) (CT),
whicharetakenfromAnnexesA3andA4,respectively,ofTest
Method E399. The crack length, a(crack pre-notch plus razor
mounted across the loading pins. For both the SENB and CT
notch), is nominally equal to the thickness, B, and is between
specimens measure the displacement at the load point.
0.45 and 0.55 times the width, W. The ratio W/Bis nominally
7. Specimen Size, Configurations, and Preparation equal to two.
7.3.2 Alternative Specimens—In certain cases it may be
7.1 Specimen Size:
desirable to use specimens having W/Bratios other than two.
7.1.1 SENB and CT geometries are recommended over
Alternative proportions for bend specimens are 2 < W/B<4.
other configurations because these have predominantly bend-
This alternative shall have the same a/Wand S/Wratios as the
ing stress states which allow smaller specimen sizes to achieve
standard specimens (S=support span).
plane strain. Specimen dimensions are shown in Fig. 3 (a, b).
If the material is supplied in the form of a sheet, the specimen 7.3.3 Displacement Correction Specimens—Separately pre-
thickness, B, is identical with the sheet thickness, in order to paredunnotchedspecimenconfigurationsforthedetermination
D5045 − 14 (2022)
of the displacement correction mentioned in 9.2 are shown in 7.4.1.4 Thedepthoftherazornotchgeneratedbyslidingthe
Fig. 4(a) for SENB and in Fig. 4(b) for CT configurations, razor blade must be two times longer than the width of the
respectively. sawed-in slot or of the pre-notch tip radius (the notch diagram
in Fig. 3 is not to scale).
7.4 Specimen Preparation:
7.4.1 Initially, prepare a sharp notch by machining.
NOTE 2—Pressing the blade into the notch is not recommended for
moreductileresinsbecauseitmayinduceresidualstressesatthecracktip
Subsequently, initiate a natural crack by inserting a fresh razor
which may result in an artificially high value of K .
Ic
blade and tapping. If a natural crack cannot be successfully
initiated by tapping, a sufficiently sharp crack shall alterna- 7.4.1.5 The total depth of the notch obtained by machining
tively be generated by sliding or sawing a new razor blade and generation of the natural crack is the crack length, a.
across the notch root. The procedure is given in 7.4.1.1 –
8. General Procedure
7.4.1
...
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