ASTM D2990

Standard Test Methods for Tensile, Compressive and Flexural Creep and Creep-Rupture of Plastics

Summary Description

The ASTM D2990 test standard specifies the characterization of tensile, compressive and flexural creep and creep-rupture of plastics under specified environmental conditions. The test is performed by applying a constant tensile, compressive or flexural load to a standard specimen and measuring the extension, compression or deflection, respectively, as a function of time and time-to-rupture. Common properties that reference ASTM D2990 include tensile strain vs. time, compressive strain vs. time and flexural strain vs. time, as well as isochronous tensile stress-strain curves.

Additional Test Standards of Relevance

  • ISO 899-1
  • ISO 899-2

Characterization Measurements and Relevant Tests

DatapointLabs offers a number of tests that address different properties covered under the ASTM D2990 standard. These include the following characterization measurements [bracketed links refer to relevant tests in the DatapointLabs Test Catalog]:

Tensile Creep (Ambient and Non-Ambient Conditions)

  • Tensile strain vs. time , isochronous tensile stress-strain curves (ambient) [M-250]

  • Tensile strain vs. time, isochronous tensile stress-strain curves (non-ambient: between 23°C-120°C and 20%-80% relative humidity) [M-250H]

Compressive Creep

  • Compressive strain vs. time [M-251]

Flexural Creep

Test Procedure and Equipment Used

In general, a creep apparatus is used to apply a specified load (stress) to the sample. The duration of the test is typically 1000 hours (or longer at a client's request, with additional cost based on daily rate). A constant load – either pneumatic, for tensile and compressive creep, or gravitational, for flexural creep – is applied to the specimen at the start of the test, and strain measurements are then made at specified time intervals throughout the duration of the test.

For tensile creep, the specimen is typically a tensile bar, which is clamped between grips with strain measured by a contact extensometer. For compressive creep, the specimen is typically a rectangular or cylindrical bar, which is placed between two compression platens with strain measured by a dial indicator. For flexural creep, the specimen is typically a flex bar, which is placed on a test rack with a load applied via a stirrup located mid-span and with strain (deflection) measured by a dial indicator.

Sample Conditioning and Non-Ambient 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. Non-ambient testing is not available for compressive and flexural creep but may be carried out for tensile creep between 23°C-120°C and 20%-80% relative humidity [M-250H].

Test Specimen Specification and Description

Specimen specifications under ASTM D2990 are as follows:

  • For tensile creep, tensile bar specimens specified by ASTM D638 Type I or Type IV, or ISO 527 Type IA are most typical; ASTM D638 Type V and straight-sided specimens are not suitable; see Specimens for further details

  • For compressive creep, creep bar specimens are typically 4.85mm (0.2”) square x 51mm (2”) long; see Compressive Creep Specimens for further details

  • For flexural creep, flex bar specimens specified by ASTM D790 or ISO 178 are most typical; see Flex Bars for further details

Characterization Measurement Descriptions

Typical characterization measurements under ASTM D2990 include:

  • Tensile Strain vs. Time: The time-dependent strain (elongation) under a constant applied tensile load, due to creep deformation of a material

  • Isochronous Tensile Stress-Strain Curves: A set of curves, each corresponding to a given total time of applied load, showing the relationship between the applied constant tensile stress and total strain (elongation) for a set of creep tests with systematically varied applied stress level and total time

  • Compressive Strain vs. Time: The time-dependent strain (compression) under a constant applied compressive load, due to creep deformation of a material

  • Flexural Strain vs. Time: The time-dependent strain (deflection) under a constant applied flexural load, due to creep deformation of a material

Complete Listing of DatapointLabs Tests Referencing ASTM D2990

The entire list of tests in the DatapointLabs test catalog that reference ASTM D2990 are as follows:

Standard Description
M-250 Tensile Creep
M-250H Tensile Creep With Humidity
M-251 Compressive Creep
M-252 Flexural Creep
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