ASTM D695
Standard Test Method for Compressive Properties of Rigid Plastics
Summary Description
The ASTM D695 test standard specifies the characterization of compressive
properties of unreinforced and reinforced rigid plastics. The test is
performed by applying a compressive load to a standard specimen. Common
properties that reference ASTM D695 include the compressive modulus,
compressive strength and strain at yield or rupture (if observed),
engineering compressive stressstrain curve, true compressive stressstrain
curve (calculated), and offset yield stress and strain in compression.
Additional Test Standards of Relevance
Characterization Measurements and Relevant Tests
DatapointLabs offers a number of tests that address different properties
covered under the ASTM D695 standard. These include the following
characterization measurements [bracketed links refer to relevant tests in
the DatapointLabs Test Catalog]:
Compressive Modulus

Compressive modulus of elasticity [M012]
Compressive Strength

Compressive modulus of elasticity, as well as compressive strength and
compressive strain at yield or rupture (if observed) [M031]
Compressive StressStrain (General, Foams)

Compressive modulus, engineering compressive stressstrain curve, true
compressive stressstrain curve (calculated), compressive strength and
strain at yield or rupture (if observed), offset yield stress and strain in
compression [M210]

Compression testing of foams: compressive modulus, engineering
compressive stressstrain curve, unloading compressive stressstrain curve,
compressive strength and strain at yield or ultimate, and offset yield
stress and strain in compression at quasistatic speeds [M215]
HighSpeed Compressive StressStrain (Foams)

Compression testing of foams: compressive modulus, engineering
compressive stressstrain curve, compressive strength and strain at yield
or ultimate, and offset yield stress and strain in compression at crosshead
speeds up to 1m/s and strain rates up to 100/s [M233]
Biaxial Tension via Uniaxial Compression

[Uniaxial compression with lubricated platens is equivalent to biaxial
tension]
Compressive modulus, engineering compressive stressstrain curve, true
compressive stressstrain curve (calculated), compressive strength and
strain at yield or rupture (if observed), offset yield stress and strain in
compression [M211]
Test Procedure and Equipment Used
The specific test procedure will vary by test and the individual test
webpages (linked to above and below) should be consulted for relevant
descriptions. In general, a universal testing machine (UTM) is used to
determine the appropriate compressive property or properties under measure.
The test specimen is placed between compression platens, which may be
unlubricated or lubricated as appropriate to the test, and compressed at a
constant crosshead speed to yield or rupture. A compressometer is used to
measure compressive strain. For highspeed compressive characterization, an
Instron 8872 servohydraulic UTM is used.
Sample Conditioning and NonAmbient Testing
Sample conditioning, if required, is carried out following specimen
preparation in accordance with ASTM D618. Typical conditioning selections
are ‘dry as molded’ (low humidity storage at 23°C) and 40 hours at 23°C and
50% relative humidity. Nonambient testing may be carried out at any
temperature between 53°C and 200°C.
Test Specimen Specification and Description
Specimen specifications under ASTM D695 are as follows:

Compression bars specified by ASTM D695; see
Compression Bars
for further details

Compression prisms, typically 25.4mm (1”) diameter x 12.7mm (0.5”)
thickness; see
Compression Prisms
for further details

Foam disks, typically 50mm diameter x 3.2mm thickness; see Compression
Disks for further details
Characterization Measurement Descriptions
Typical characterization measurements under ASTM D695 include:

Compressive Modulus: The ratio of compressive stress (load) to the
corresponding strain (compression), measured below the elastic limit of a
material

Compressive Strength at Yield: The maximum compressive stress at the
point where a material transitions from elastic to plastic behavior (Yield
Point)

Compressive Strain at Yield: The maximum strain at the point where a
material transitions from elastic to plastic behavior (Yield Point)

Compressive Ultimate Strength: The maximum compressive stress at the
point of material rupture

Compressive Ultimate Strain: The maximum strain at the point of material
rupture

Engineering Compressive StressStrain Curve: The graphical relationship
between stress and strain in a material under compressive load, based on
the original crosssection of the test specimen

True Compressive StressStrain Curve: The graphical relationship between
stress and strain in a material under compressive load, calculated from the
engineering compressive stressstrain curve

Offset Yield Stress in Compression: The offset yield method determines
the yield point by the intercept of the stressstrain curve and a line with
slope corresponding to the elastic modulus and a strain offset (nominally
0.2%); the offset yield stress is the stress at the determined intercept

Offset Yield Strain in Compression: The offset yield method determines
the yield point by the intercept of the stressstrain curve and a line with
slope corresponding to the elastic modulus and a strain offset (nominally
0.2%); the offset yield strain is the strain at the determined intercept
Complete Listing of DatapointLabs Tests Referencing ASTM D695
The entire list of tests in the DatapointLabs test catalog that reference
ASTM D695 are as follows: