Compression Creep Behaviour Testing | ISO 899 & ASTM D2990
Plastic and polymer components that experience continuous compressive loading can gradually deform over time, even when the applied stress is significantly below the material’s short-term compressive strength. This time-dependent deformation, known as creep, can affect the dimensional stability, functionality and service life of a component.
Materials used in supports, spacers, housings, seals and other load-bearing applications may remain under compression for extended periods. Excessive creep can result in changes in thickness, permanent deformation, loss of load-bearing capability, reduced dimensional accuracy or eventual component failure. Short-term mechanical testing alone may therefore be insufficient to understand how a material will behave throughout its intended service life.
Compression creep testing provides quantitative information about how plastics respond to sustained compressive loading. Testing to the relevant ISO 899 requirements and ASTM D2990 can support material selection, product design, comparative assessment and evaluation of long-term mechanical performance.
What Compression Creep Behaviour Testing Involves
Compression creep testing evaluates the time-dependent deformation of a material while it is subjected to a constant compressive load or stress for a specified period.
The ISO 899 series covers the determination of creep behaviour of plastics under specified loading conditions.
ASTM D2990 includes methods for determining compressive creep and creep-rupture behaviour of plastics under specified environmental conditions.
During compression creep testing, a specimen is subjected to a defined compressive stress and the resulting deformation is measured as a function of time. The applied load is maintained throughout the specified test period while relevant environmental conditions are controlled.
Testing can be performed on materials including:
- Thermoplastics
- Thermosetting plastics
- Engineering polymers
- Reinforced plastics
- Filled polymer compounds
- Moulded plastic materials
- Polymer-based engineering materials
- Materials intended for sustained compressive loading
Depending on the selected method and test programme, testing can provide information including:
- Compressive creep strain
- Time-dependent deformation
- Change in specimen thickness or displacement
- Creep curves
- Creep rate
- Long-term dimensional stability
- Comparative behaviour at different stress levels
- Influence of temperature and environmental conditions
- Creep-rupture behaviour where applicable
The resulting data can help engineers understand whether a material is capable of maintaining its dimensions and mechanical performance during prolonged compressive loading.
Methodology
At Impact Solutions, compression creep testing is carried out using controlled loading and measurement equipment in accordance with the applicable ISO 899 requirements or ASTM D2990.
A typical testing programme includes:
- Identification of the applicable test method, compressive stress, test duration and environmental conditions.
- Preparation of representative specimens appropriate to the material and test programme.
- Conditioning of specimens under the specified environmental conditions.
- Measurement of specimen dimensions before testing.
- Positioning and alignment of the specimen within the compression creep test equipment.
- Application of the specified compressive load or stress.
- Maintenance of the applied load for the required test duration.
- Measurement of deformation at specified time intervals throughout the test.
- Calculation and assessment of the required compressive creep properties.
- Comprehensive reporting of test conditions, time-dependent behaviour, results and relevant observations.
Where required, testing can be performed at multiple stress levels, temperatures or durations to investigate how these variables influence long-term compressive behaviour.
Relevant Industry Applications
Compression creep behaviour testing is widely applicable to:
- Automotive components
- Aerospace materials
- Construction products
- Engineering plastics
- Structural polymer components
- Plastic supports and spacers
- Electrical and electronic components
- Industrial equipment
- Consumer products
- Reinforced polymer materials
- Load-bearing plastic components
- Material development
- Product design and validation
- Research and development
- Quality assurance programmes
Benefits of Compression Creep Behaviour Testing
- Characterises long-term deformation under sustained compression
- Measures time-dependent compressive behaviour
- Supports selection of materials for continuously loaded applications
- Helps assess long-term dimensional stability
- Enables comparison between different polymers and formulations
- Evaluates the influence of applied stress on creep performance
- Can investigate the effects of temperature and environmental conditions
- Supports engineering design and material modelling
- Helps identify materials susceptible to excessive compressive deformation
- Provides performance data for product development and technical documentation
- Supports creep-rupture assessment where applicable
- Uses recognised ISO and ASTM creep testing methods
Need to understand how your materials perform under sustained compression?
Contact Impact Solutions to discuss compression creep testing to the applicable ISO 899 requirements and ASTM D2990 and obtain reliable long-term mechanical performance data for your plastics and polymer materials.
FAQ
Q: What is compression creep?
Compression creep is the gradual, time-dependent deformation of a material while it is subjected to a sustained compressive load or stress. A plastic material can continue to deform even though the applied load remains constant.
Q: What does the ISO 899 series cover?
The ISO 899 series addresses the determination of creep behaviour in plastics under specified loading conditions. The appropriate part and test configuration should be selected according to the required mode of loading and material behaviour being assessed.
Q: What is ASTM D2990?
ASTM D2990 covers methods for determining creep and creep-rupture behaviour of plastics. It includes compressive creep testing, allowing deformation to be measured over time while a specimen remains under a sustained compressive load.
