ASTM D6108-97

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 6108 – 97
Standard Test Method for
Compressive Properties of Plastic Lumber and Shapes
This standard is issued under the fixed designation D 6108; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope E 83 Practice for Verification and Classification of Exten-
someters
1.1 This test method covers the determination of the me-
D 6111 Test Method for Bulk Density and Specific Gravity
chanical properties of plastic lumber and shapes, when the
of Plastic Lumber and Shapes by Displacement
entire cross-section is loaded in compression at relatively low
uniform rates of straining or loading. Test specimens in the
3. Terminology
“as-manufactured” form are employed. As such, this is a test
3.1 Definitions:
method for evaluating the properties of plastic lumber or
3.1.1 compressive deformation—the decrease in length pro-
shapes as a product and not a material property test method.
duced in the gage length of the test specimen by a compressive
1.2 Plastic lumber and plastic shapes are currently made
load. It is expressed in units of length.
predominantly with recycled plastics. However, this test
3.1.2 compressive strain—the ratio of compressive defor-
method would also be applicable to similar manufactured
mation to the gage length of the test specimen, that is, the
plastic products made from virgin resins, or where the product
change in length per unit of original gage length along the
is non-homogenous in the cross-section.
longitudinal axis. It is expressed as a dimensionless ratio.
1.3 The values stated in inch–pound units are to be regarded
3.1.3 compressive strength—the maximum compressive
as the standard. The values given in parentheses are for
stress (nominal) carried by a test specimen during a compres-
information only.
sion test. It may or may not be the compressive stress
1.4 This standard does not purport to address all of the
(nominal) carried by the specimen at the moment of rupture.
safety concerns, if any, associated with its use. It is the
3.1.4 compressive stress (nominal)—the compressive load
responsibility of the user of this standard to establish appro-
per unit area of minimum (or effective as calculated in
priate safety and health practices and determine the applica-
accordance with Test Method D 6111) original cross section
bility of regulatory limitations prior to use.
within the gage boundaries, carried by the test specimen at any
NOTE 1—There is no similar or equivalent ISO standard.
given moment. It is expressed in force per unit area.
3.1.4.1 Discussion—The expression of compressive stress
2. Referenced Documents
in terms of the minimum original cross section is almost
2.1 ASTM Standards:
universally used. Under some circumstances the compressive
D 618 Practice for Conditioning Plastics for Testing
stress has been expressed per unit of prevailing cross section.
D 883 Terminology Relating to Plastics
This stress is called the “true compressive stress”.
D 4000 Classification System for Specifying Plastic Mate-
3.1.5 compressive stress-strain diagram—a diagram in
rials
which values of compressive stress are plotted as ordinates
D 5033 Guide for the Development of Standards Relating to
against corresponding values of compressive strain as abscis-
the Proper Use of Recycled Plastics
sas.
D 5947 Test Methods for Physical Dimensions of Solid
3.1.6 compressive yield point—the first point on the stress-
Plastics Specimens
strain diagram at which an increase in strain occurs without an
E 4 Practices for Load Verification of Testing Machines
increase in stress.
3.1.7 modulus of elasticity—the ratio of compressive stress
(nominal) to corresponding compressive strain below the
These test methods are under the jurisdiction of ASTM Committee D-20 on
proportional limit of a material. It is expressed in force per unit
Plastics and are the direct responsibility of Subcommittee D20.20 on Plastic
Products (Section D20.20.01).
area based on the effective/average initial cross-sectional area.
Current edition approved July 10, 1997. Published February 1998.
3.1.8 percent compressive strain—the compressive defor-
Annual Book of ASTM Standards, Vol 08.01.
3 mation of a test specimen expressed as a percent of the original
Annual Book of ASTM Standards, Vol 08.02
Annual Book of ASTM Standards, Vol 08.03. gage length.
Annual Book of ASTM Standards, Vol 03.01.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D6108–97
3.1.9 plastic lumber, n—a manufactured product composed yield point. Compressive strength can have no real meaning in
of more than 50 weight percent resin, and in which the product such cases. For plastic lumber, the stress at a given strain of
generally is rectangular in cross-section and typically supplied 3 % (0.03 in./in. (mm/mm)) is typically used.
in board and dimensional lumber sizes, may be filled or
4.3 Compression tests provide a standard method of obtain-
unfilled, and may be composed of single or multiple resin ing data for research and development, quality control, accep-
blends.
tance or rejection under specifications, and special purposes.
3.1.10 plastic shape, n—a manufactured product composed The tests cannot be considered significant for engineering
of more than 50 weight percent resin, and in which the product design in applications differing widely from the load-time scale
generally is not rectangular in cross-section, may be filled or of the standard test. Such applications require additional tests
unfilled, and may be composed of single or multiple resin such as impact, creep, and fatigue.
blends.
3.1.11 proportional limit—the greatest compressive stress
5. Apparatus
that a material is capable of sustaining without any deviation
5.1 Testing Machine— Any suitable testing machine ca-
from proportionality of stress to strain (Hooke’s law). It is
pable of control of constant-rate-of-crosshead movement and
expressed in force per unit area.
comprising essentially the following:
3.1.12 resin, n—a solid or pseudosolid organic material
5.1.1 Drive Mechanism— A drive mechanism for imparting
often of high molecular weight, which exhibits a tendency to
to the cross-head movable member, a uniform, controlled rate
flow when subjected to stress, usually has a softening or
of movement with respect to the base (fixed member), with this
melting range, and usually fractures conchoidally. (See Termi-
cross-head rate to be regulated as specified in Section 9.
nology D 883.)
5.1.2 Load Indicator— A load-indicating mechanism ca-
3.1.12.1 Discussion—In a broad sense, the term is used to
pable of showing the total compressive load carried by the test
designate any polymer that is a basic material for plastics.
specimen. The mechanism shall be essentially free from
3.1.13 secant modulus—the ratio of the compressive stress
inertia-lag at the specified rate of testing and shall indicate the
(nominal) to the corresponding value of compressive strain on
load with an accuracy of 61 % of the maximum indicated
the stress-strain diagram at a specified value of strain, typically
value of the test (load). The accuracy of the testing machine
one percent strain (0.01 mm / mm) for plastic lumber. It is
shall be verified at least once a year in accordance with
expressed in force per unit area based on the effective initial
Practices E 4.
cross-sectional area.
5.2 Compressometer— A suitable instrument for determin-
3.1.14 stress at a given strain—the stress on the stress-strain
ing the distance between two fixed points on the test specimen
curve at a specified value of strain.
at any time during the test. It is desirable that this instrument
3.1.14.1 Discussion—The stress at a given strain should not
automatically record this distance (or any change in it) as a
be taken as the ultimate strength at failure. Typically a strain
function of the load on the test specimen. The instrument shall
value of 3 % or 0.03 mm/mm is used for plastic lumber. The
be essentially free of inertia-lag at the specified rate of loading
ultimate strength, or the maximum value of stress on the
and shall conform to the requirements for a Class C extensom-
stress-strain diagram, can be higher for plastic lumber occur-
eter as defined in Practice E 83.
ring at values of strain much greater than 3 %.
5.2.1 The requirements for extensometers cited herein apply
3.2 Additional definition of terms applying to this test
to compressometers as well.
method appear in Terminology D 883 and Guide D 5033.
5.2.2 Compression platen movement may be used to deter-
mine compressive displacements of test samples.
4. Significance and Use
5.3 Compression Platens—A compression platen for apply-
4.1 Compression tests provide information about the com-
ing the load to the test specimen. Parallel platens shall be used
pressive properties of plastic lumber and shapes when these
to apply the load to an unconfined type specimen. One of the
products are used under conditions approximating those under
compression platens shall be self aligning in order that the load
which the tests are made. For many materials, there may be a
may be applied evenly over the face of the specimen.
specification that requires the use of this test method, but with
5.4 Micrometers— Suitable micrometers, reading to 0.01 in.
some procedural modifications that take precedence when
for measuring the width, thickness, and length of the speci-
adhering to the specification. Therefore, it is advisable to refer
mens.
to that material specification before using this test method.
Table 1 in Classification D 4000 lists the ASTM materials
6. Test Specimens
standards that currently exist.
4.2 Compressive properties include modulus of elasticity, 6.1 Test specimens for determining compressive properties
secant modulus, compressive strength, and stress at a given of plastic lumber and shapes shall be cut from the “as
strain. In the case of a material that fails in compression by a manufactured” profile. Great care shall be taken in cutting and
shattering fracture, the compressive strength has a very definite machining the ends so that smooth, flat parallel surfaces and
value. In the case of a material that does not fail in compression sharp, clean edges result and are within 1/300 (0.0033) of the
by a shattering fracture nor exhibits a compressive yield point, specimen length perpendicular to the long axis of the speci-
the compressive strength is an arbitrary one depending upon men. Plastic lumber is gener
...