Tensile Creep Behaviour Testing | ISO 899-1 & ASTM D2990

Plastic and polymer materials can perform well during short-term mechanical testing but behave very differently when subjected to a constant load over an extended period. Even when the applied stress is below the material’s immediate tensile strength, gradual deformation known as creep can occur.

For components expected to carry sustained loads, this time-dependent deformation can result in dimensional changes, loss of stiffness, reduced functionality or eventual failure. Temperature, applied stress, material formulation, reinforcement and environmental conditions can all significantly influence creep behaviour.

Tensile creep testing provides manufacturers and engineers with data on how materials deform under sustained tensile loading. Testing to ISO 899-1 and ASTM D2990 can support long-term material selection, product design, comparative material assessment and prediction of performance under prolonged loading conditions.

What Tensile Creep Behaviour Testing Involves

Tensile creep testing evaluates the time-dependent deformation of a material while it is subjected to a constant tensile load or stress for a specified period.

ISO 899-1 specifies a method for determining the tensile creep behaviour of plastics in the form of standard test specimens under specified conditions, including the determination of tensile creep modulus.

ASTM D2990 covers methods for determining tensile and compressive creep and creep-rupture behaviour of plastics under specified environmental conditions.

During a tensile creep test, a specimen is subjected to a defined tensile stress and its deformation is measured as a function of time. Depending on the test programme, measurements may continue for hours, days or substantially longer periods to characterise long-term behaviour.

Testing can be performed on materials including:

Thermoplastics

Thermosetting plastics

Engineering polymers

Reinforced plastics

Filled polymer compounds

Plastic sheets and moulded materials

Polymer-based engineering materials

Materials intended for sustained-load applications

Depending on the selected test method and programme, testing can provide information including:

Tensile creep strain

Tensile creep modulus

Time-dependent deformation

Creep curves

Creep rate

Creep-rupture behaviour where applicable

Time to rupture where applicable

Comparative performance at different stress levels

Effects of temperature and environmental conditions

The resulting data provides valuable insight into how a polymer material may behave when subjected to sustained mechanical loading over time.

Methodology

At Impact Solutions, tensile creep testing is carried out using controlled loading and measurement equipment in accordance with ISO 899-1 or ASTM D2990.

A typical testing programme includes:

Identification of the applicable standard, required stress level, test duration and environmental conditions.
Preparation of representative test specimens in accordance with the applicable test method.
Conditioning of specimens under specified environmental conditions.
Measurement of specimen dimensions prior to testing.
Installation and alignment of the specimen within the creep testing equipment.
Application of the specified tensile load or stress.
Maintenance of the applied load for the required test duration.
Measurement of specimen deformation at specified time intervals throughout the test.
Calculation of tensile creep strain, creep modulus or other required creep properties.
Comprehensive reporting of test conditions, creep behaviour, results and relevant observations.

Where required, testing programmes can incorporate different stress levels, temperatures or durations to investigate how these variables affect long-term material performance.

Relevant Industry Applications

Tensile creep behaviour testing is widely applicable to:

Automotive components

Aerospace materials

Construction products

Pipes and engineering systems

Electrical and electronic components

Industrial equipment

Consumer products

Engineering plastics

Reinforced polymer materials

Long-term load-bearing components

Material development

Product design and validation

Research and development

Quality assurance programmes

Benefits of Tensile Creep Behaviour Testing

Characterises long-term deformation under sustained tensile loading

Determines tensile creep modulus

Provides time-dependent material performance data

Supports selection of materials for long-term load-bearing applications

Enables comparison between different polymers and formulations

Evaluates the influence of stress and temperature on creep behaviour

Supports engineering design and material modelling

Helps identify materials susceptible to excessive long-term deformation

Provides data for product development and technical documentation

Supports creep-rupture assessment where applicable

Uses internationally recognised ISO and ASTM test methods

Need to understand how your materials perform under sustained tensile loading?

Contact Impact Solutions to discuss tensile creep behaviour testing to ISO 899-1 and ASTM D2990 and obtain reliable long-term mechanical performance data for your plastics and polymer materials.

FAQ

Q: What is tensile creep?

Tensile creep is the gradual, time-dependent deformation of a material while it is subjected to a sustained tensile stress. A material can continue to deform even when the applied load remains constant.

Q: What is ISO 899-1?

ISO 899-1 specifies a method for determining the tensile creep behaviour of plastics under specified conditions. It can be used to determine properties including tensile creep strain and tensile creep modulus.

Q: What is ASTM D2990?

ASTM D2990 covers creep and creep-rupture testing of plastics under specified environmental conditions. It includes methods for tensile and compressive loading and can be used to evaluate deformation over time and, where required, creep rupture.