ASTM D6112-97
(Test Method)Standard Test Methods for Compressive and Flexural Creep and Creep-Rupture of Plastic Lumber and Shapes
Standard Test Methods for Compressive and Flexural Creep and Creep-Rupture of Plastic Lumber and Shapes
SCOPE
1.1 These test methods cover the determination of the creep and creep-rupture properties of plastic lumber and shapes, when loaded in compression or flexure under specified environmental conditions. test specimens in the "as-manufactured" form are employed. As such, these are test methods for evaluating the properties of plastic lumber or shapes as a product and not material property test methods.
1.2 Plastic lumber and plastic shapes are currently made predominantly with recycled plastics. However, this test method would also be applicable to similar manufactured plastic products made from virgin resins where the product is non-homogenous in the cross-section.
1.3 The values stated in SI units are to be regarded as the standard.
1.4 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 and health practices and determine the applicability of regulatory limitations prior to use.
Note 1- There is no similar or equivalent ISO standard.
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Designation: D 6112 – 97
Standard Test Methods for
Compressive and Flexural Creep and Creep-Rupture of
Plastic Lumber and Shapes
This standard is issued under the fixed designation D 6112; 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 E 4 Practices for Load Verification of Testing Machines
1.1 These test methods cover the determination of the creep
3. Terminology
and creep-rupture properties of plastic lumber and shapes,
3.1 Definitions:
when loaded in compression or flexure under specified envi-
3.1.1 compression—in a compressive creep test, the de-
ronmentalconditions.Testspecimensinthe“as-manufactured”
crease in length produced in the gage length or the total length
form are employed. As such, these are test methods for
of a test specimen.
evaluating the properties of plastic lumber or shapes as a
3.1.2 creep modulus—the ratio of initial applied stress to
product and not material property test methods.
creep strain.
1.2 Plastic lumber and plastic shapes are currently made
3.1.3 creep strain—the total strain, at any given time,
predominantly with recycled plastics. However, this test
produced by the applied stress during a creep test.
method would also be applicable to similar manufactured
3.1.3.1 Discussion—The term creep, as used in this test
plastic products made from virgin resins where the product is
method,reflectscurrentplasticsengineeringusage.Inscientific
non-homogenous in the cross-section.
practice, creep is often defined to be the nonelastic portion of
1.3 Thevaluesstatedininch–poundunitsaretoberegarded
strain. However, this definition is not applicable to existing
as the standard. The values given in parentheses are for
engineering formulas. Plastics have a wide spectrum of retar-
information only.
dation times, and elastic portions of strain cannot be separated
1.4 This standard does not purport to address all of the
in practice from nonelastic. Therefore, wherever “strain” is
safety concerns, if any, associated with its use. It is the
mentioned in these test methods, it refers to the sum of elastic
responsibility of the user of this standard to establish appro-
strain plus the additional strain with time.
priate safety and health practices and determine the applica-
3.1.4 deflection—in a flexural creep test, the change in
bility of regulatory limitations prior to use.
mid-span position of a test specimen.
NOTE 1—There is no similar or equivalent ISO standard.
3.1.5 deformation—a change in shape, size or position of a
test specimen as a result of compression, deflection, or exten-
2. Referenced Documents
sion:
2.1 ASTM Standards:
3.1.6 plasticlumber,n—amanufacturedproductcomposed
D 543 Test Method for Resistance of Plastics to Chemical
ofmorethan50weightpercentresin,andinwhichtheproduct
Reagents
generally is rectangular in cross-section and typically supplied
D 883 Terminology Relating to Plastics
in board and dimensional lumber sizes, may be filled or
D 2990 Standard Test Methods for Tensile, Compressive,
unfilled, and may be composed of single or multiple resin
and Flexural Creep and Creep Rupture of Plastics
blends.
D 4000 Classification System for Specifying Plastics
3.1.7 plastic shape, n— a manufactured product composed
D5033 GuidefortheDevelopmentofStandardsRelatingto
ofmorethan50weightpercentresin,andinwhichtheproduct
the Proper Use of Recycled Plastics
generally is not rectangular in cross-section, may be filled or
D 5947 Test Methods for Physical Dimensions of Solid
unfilled, and may be composed of single or multiple resin
Plastics Specimens
blends.
3.1.8 resin, n—a solid or pseudo-solid organic material
oftenofhighmolecularweight,thatexhibitsatendencytoflow
These test methods are under the jurisdiction of ASTM Committee D-20 on
when subjected to stress, usually has a softening or melting
Plasticsand are the direct responsibility of Subcommittee D20.20 on Plastic
range, and usually fractures conchoidally. (See Terminology
Products (Section D20.20.01).
D883.)
Current edition approved July 10, 1997. Published February 1998.
Annual Book of ASTM Standards, Vol 08.01.
Annual Book of ASTM Standards, Vol 08.02.
4 5
Annual Book of ASTM Standards, Vol 08.03. 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.
D6112–97
3.1.8.1 Discussion—In a broad sense, the term is used to 6.1.2.2 Deformation measuring devices shall be calibrated
designate any polymer that is a basic material for plastics. againstaprecisionmicrometerscreworothersuitablestandard
3.1.9 stress—for compressive creep, the ratio of the applied under conditions are nearly identical as possible with those
load to the initial cross-sectional area. For flexural creep, encountered in the test. Caution is necessary when using
maximum fiber stress is calculated according to Eq 1. deformation measuring devices whose calibration is subject to
3.1.10 Additional definition of terms applying to this test drifting with time and is dependent on temperature and
method appear in Terminology D883 and Guide D5033. humidity.
6.1.2.3 Deformation measuring devices shall be firmly at-
4. Summary of Test Method
tached to or seated on the specimen so that no slippage occurs.
4.1 These test methods consist of measuring the deflection
Electrical resistance gages are suitable only if the material
or compression as a function of time and time-to-rupture, or tested will permit perfect adhesion to the specimen and if they
failure of a specimen subject to constant flexural or compres-
are consistent with 6.2.1
sive load under specified environmental conditions. 6.1.3 Time Measurement— The accuracy of the time mea-
4.2 Thefour-pointloadingaoutlinedinthistestingstandard
suringdeviceshallbe 61%ofthetime-to-ruptureorfailureor
shall be used for the flexural creep tests.
the elapsed time of each creep measurement, or both.
4.3 Compressive loading as outlined in this testing standard 6.1.4 Temperature Control and Measurement:
shall be used for the compressive creep tests.
6.1.4.1 Thetemperatureofthetestspace,especiallycloseto
4.4 These test methods represent modifications of the com- the gage length of the specimen, shall be maintained within
pressive and flexural creep and creep rupture test methods
62°C by a suitable automatic device and shall be stated in
specified in Test Methods D2990. reporting the results.
NOTE 2—The thermal contraction and expansion associated with small
5. Significance and Use
temperature changes during the test may produce changes in the apparent
5.1 Datafromcreepandcreep-rupturetestsarenecessaryto
creep rate, especially near transition temperatures.
predict the creep modulus and strength of materials under
6.1.4.2 Care must be taken to ensure accurate temperature
long-term loads and to predict dimensional changes that may
measurementsoverthegagelengthofthespecimenthroughout
occur as a result of such loads.
the test. The temperature measuring devices shall be checked
5.2 Datafromthesetestmethodscanbeusedtocharacterize
regularly against temperature standards and shall indicate the
plastic lumber: for comparison purposes, for the design of
temperature of the specimen gage area.
fabricated parts, to determine long-term performance under
6.1.4.3 Temperature measurements shall be made at fre-
constant load, and under certain conditions, for specification
quent intervals, or continuously recorded to ensure an accurate
purposes.
determination of the average test temperature and compliance
5.3 For many products, there may be a specification that
with 6.1.5.
requires the use of this test method, but with some procedural
6.1.5 Environmental Control and Measurements:
modifications that take precedence when adhering to the
6.1.5.1 Whenthetestenvironmentisair,therelativehumid-
specification. Therefore, it is advisable to refer to that product
ity shall be controlled to 50 6 5% during the test unless
specification before using this test method. Table 1 in Classi-
otherwise specified, or unless the creep behavior of the
fication D4000 lists the ASTM materials standards that cur-
material under testing has been shown to be unaffected by
rently exist.
humidity. The controlling and measuring instruments shall be
stable for long time intervals and accurate to within 61%.
6. Apparatus
(The control of relative humidity is known to be difficult at
6.1 General:
temperatures much outside the range from 50 to 104°F (10 to
6.1.1 Loading System:
40°C).)
6.1.1.1 The loading system must be so designed that the
6.1.5.2 If, for any reason, the specified relative humidity
load applied and maintained on the specimen is within 61%
cannot be achieved or the test is conducted to determine the
of the desired load. The loading mechanism must allow
sensitivity of the product to high humidity, the actual average
reproductivelyrapidandsmoothloadingasspecifiedin11.1.3.
value and fluctuation of relative humidity used should be
In creep-rupture tests, provision must be made to ensure that
reported.
shock loading, caused by a specimen failure, is not transferred
6.1.5.3 The composition of the test environment shall be
to other specimens undergoing testing. The accuracy of the
maintained constant throughout the test.
loading system shall be verified at least once each year in
accordance with Practices E4.
NOTE 3—Warning:Safety precautions should be taken to void per-
sonal contact, to eliminate toxic vapors, and to guard against explosion
6.1.1.2 Loading systems that provide a mechanical advan-
hazardsinaccordancewithanypossiblehazardousnatureoftheparticular
tage require careful design to maintain constant load through-
environment being used.
out the test. For example, lever systems must be designed so
thattheloaddoesnotchangeastheleverarmmovesduringthe 6.1.6 Vibration Control—Creep tests are quite sensitive to
test. shock and vibration. The location of the apparatus, the test
6.1.2 Compression and Deflection Measurements: equipment, and mounting shall be so designated that the
6.1.2.1 The accuracy of the deformation measuring device specimen is isolated from vibration. Multiple-station test
shall be within 61% of the deformation to be measured. equipment must be of sufficient rigidity so that no significant
D6112–97
deflection occurs in the test equipment during creep or creep- where such specification are available . Other grades may be
rupture testing. During time-to-rupture or failure, means to used, provided it is first ascertained that the reagent is of
prevent jarring of other test specimens by the falling load from sufficiently high purity to permit its use without lessening the
a failed test specimen shall be provided by a suitable net or accuracy of the determination.
cushion.
7.2 Purity of Water— Unless otherwise indicated, refer-
6.2 Compressive Creep: ences to water shall be understood to mean distilled water or
6.2.1 Platens—Parallel platens shall be used to apply the water of equal purity.
load to the unconfined-type specimen (see 8.2). One of the 7.3 Specified Reagents—Should this test method be refer-
platens of the machine shall preferably be self-aligning and
encedinamaterialspecification,thespecificreagenttobeused
shall,inorderthattheloadmaybeappliedevenlyovertheface shall be as stipulated in the specification.
ofthespecimen,bearrangedsothatthespecimenisaccurately
7.4 Standard Reagents—A list of standard reagents is also
centered and the resultant of the load is through its center.
available in Test Method D543.
6.2.2 The compression of specimen gage length under load
shall be measured by means of any device that will not
8. Test Specimen
influence the specimen behavior by mechanical (undesirable
8.1 General:
deformation,notches,etc.)physical(heatingofspecimen,etc.),
8.1.1 Test specimens may be made by any of the techniques
or chemical effects. Alternatively, the compression of the
normally employed to produce plastic lumber. When the
specimen can be measured using platen displacement with the
testingobjectiveistoobtaindesigndata,themethodofsample
entire length of the specimen serving as the gage length.
fabrication shall be the same as that used in the application.
6.3 Flexural Creep:
8.1.2 In the case of materials whose dimensions are known
6.3.1 Test Rack—A rigid test rack shall be used to provide
to change significantly due to the specified environment alone
support of the test specimen at both ends with a span equal to
(for example, the shrinkage of some thermosetting plastics due
16 (tolerant +4 and −2) times the depth of the specimen. In
to post-curing at elevated temperatures), provision shall be
ordertoavoidexcessiveindentationofthespecimen,theradius
made to test unloaded control specimens alongside the test
of the support shall be a minimum of 0.5 in. (12.7 mm) and up
specimensothatcompensationmaybemadeforchangesother
to1.5timesthedepthofthespecimen.Sufficientspacemustbe
than creep. A minimum of three control specimens shall be
allowed below the specimen for dead-weight loading.
tested at each test temperature.
6.3.2 Loading Beam— The loading beam shall be config-
8.1.3 In creep testing at a single temperature, the minimum
ured with loading noses with cylindrical surfaces (see Fig. 1).
number of test specimens at each stress shall be two if four or
The radius of noses shall be at least 0.5 in. (12.7 mm) or all
more levels of stress are used or three if fewer than four levels
specimens. For large specimens the radius of the supports may
are used.
be up to 1.5 times the specimen depth.
8.1.4 Increep-rupturetesting,aminimumoftwospecimens
6.3.3 A four point loading arrangement shall be used as
shall be tested at each of the stress levels specified in 10.2.1 at
shown in Fig. 1.
each temperature.
6.3.4 For flexural testing the deflection of the specimen
shall be measured at the midpoint of the load span at the NOTE 4—The scatter of creep-rupture data is considerable, with one
half to a full decade of variation in time-to-rupture being typical.
bottom face of the specimen.
Therefore, it may be necessary to test more than two specimens at each
stress level to obtain satisfactory results.
7. Reagents
8.2 Compressive Creep:
7.1 Purity of Reagents—Reagent grade chemicals shall be
8.2.1 The standard test specimen shall be in the form of a
used in all tests. Unless otherwise indicated, it is intended that
all reagents shall conform to the specifications of the Commit- right prism. With the exception that specimen cross sections
are the full sections of any manufact
...
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