ASTM D2990 Standard Test Methods for Tensile, Compressive, and Flexural Creep and Creep-Rupture of Plastics
What is ASTM D2990?
ASTM D2990 is a standard test method for tensile, compressive, and flexural creep and creep-rupture of plastics under specified environmental conditions. This method helps manufacturers to determine how plastic deforms and withstands sustained loads over time. The standard uses tensile and compressive loading for creep evaluation and uses three-point loading for flexural creep. Four-point loading can also be used for flexural creep in the laboratory. ASTM D2990 (Test Methods for Tensile, Compressive, and Flexural Creep and Creep-Rupture of Plastics) is a standard test method for tensile, compressive, and flexural creep and creep-rupture of plastics under specified environmental conditions. This standard defines tension as the preferred stress mode for creep-rupture measurements because some ductile plastics may not rupture during flexural or compression testing.
Get Certified ASTM D2990 Testing for Reliable Plastic Creep Performance
Under long-duration continuous loading, plastic elements can gradually deform. This time-dependent behavior is measured in accordance with standardized procedures in ASTM D2990. The data provide a means for the plastics industry to compare plastics, to characterize long-term performance, to support fabricated-part design, and to provide engineering data for parts that are subjected to sustained loading.
What is the scope of the ASTM D2990 test standard?
ASTM D2990 specifies creep and creep-rupture testing of plastics under defined environmental conditions. This standard presents tensile, compressive, and flexural methods, allowing laboratories to choose the loading mode best suited to the material application. The ASTM D2990 standard-
Determines tensile creep of plastics, compressive creep of plastics, flexural creep, and creep-rupture behavior.
Uses three-point loading for flexural creep and allows four-point loading as an alternative for flexural creep.
Uses tension as the preferred mode for creep-rupture testing.
What are the uses of ASTM D2990 testing?
ASTM D2990 testing helps laboratories determine the long-term performance of plastics under sustained loads. Manufacturers use these results to evaluate deformation, compare materials, and support plastic component design. This testing-
Evaluates tensile creep, compressive creep, and flexural creep.
Determines creep-rupture behavior and helps compare different plastic materials.
Enables long-term plastic performance assessment.
Which materials can be tested under ASTM D2990?
ASTM D2990 evaluates plastics for creep or creep-rupture under specified environmental conditions. Technicians can prepare specimens using injection molding, compression molding, or cutting from sheets and other fabricated shapes.
Why is ASTM D2990 Important?
ASTM D2990 provides a standardized way to characterize the time-dependent deformation and failure behavior of plastics. Engineers use this creep data to predict long-term deformation, creep modulus, creep strength, and any possible dimensional changes under sustained load.
ASTM D2990 Equipment and Sample Preparation Guide
ASTM D2990 provides alternative specimen configurations and loading equipment for the various creep modes. Laboratories should first verify the material specification, as it may determine specimens, size, conditioning, and testing parameters per ASTM D2990.
Technicians prepare plastic specimens for tensile, compressive, or flexural creep testing.
Specimen Preparation
Technicians may use injection molding, compression molding, or machining of sheets and fabricated parts to prepare specimens.
Specimen Dimensions
Technicians should prepare dimensions having a cross section of 12.7 × 12.7 mm or a cylinder 12.7 mm in diameter for compression specimens and 63.5 × 12.7 × 3.18 mm or 127 × 12.7 × 6.4 mm for flexural specimens.
Instrumentation
Creep-testing machine, tensile grips, compression fixtures, flexural loading fixture, loading weights or force application system, displacement-measuring equipment, environmental conditioning equipment, and appropriate dimensional-measuring instruments.
Test Procedures and Requirements for ASTM D2990
According to ASTM D2990, technicians should choose the correct loading mode, prepare specimens correctly, apply a control load, and observe deformation or rupture during the specified test period. Laboratories should use the material specification when it provides specific testing conditions. Other reference ASTM documents include D543, D618, D638, D695, D790, D883, D1822, D4000, D4065, D4968, D5947, and D6272. The testing procedures and requirements for ASTM D2990 are given as-
Specimen Selection and Preparation
Analysts should select a tensile, compressive, or flexural specimen as required and prepare specimens by injection molding, compression molding, machining, or other acceptable means.
Conditioning and Load Application
Then, they condition the specimens and apply load based on material application and controlled environmental conditions.
Creep Measurement
Analysts measure deformation over time under the applied load.
Flexural Creep and Creep-Rupture
Analysts use three-point loading or the permitted four-point loading arrangement for flexural creep and monitor the specimen until rupture.
Data Recording
Engineers document load, deformation, elapsed time, temperature, environmental conditions, specimen information, and rupture observations.
ASTM D2990 Testing Process and Data Collection
Laboratories first determine the plastic material and check applicable material specifications. Technicians then choose the correct specimen configuration and prepare the specimens using the necessary fabrication technique. Technicians then condition the specimens, load them into the appropriate tensile, compression, or flexural test setup, and apply load continuously or periodically while measuring over time. For creep-rupture testing, technicians monitor the specimen until rupture and record the corresponding test information. Manufacturers use the resulting data to evaluate the long-term deformation behavior, creep modulus, creep strength, and creep-rupture characteristics.
ASTM D2990 Universal Testing Machine
Common Challenges and Troubleshooting
To achieve accurate creep testing, specimens must be prepared the same, loaded in a controlled manner, conditioned the same, and deformations measured reliably. Creep results are subject to variation due to specimen fabrication, specimen size, environmental conditions, and loading. Common problems include inconsistent specimen preparation, inadequate specimen dimensions, improper specimen conditioning, unstable applied load, misalignment in the loading fixture, inaccurate deformation measurements, and temperature fluctuations during extended testing. Technicians should be concerned with the size of the specimen, calibration of load and measurement systems, control of environmental conditions, and compliance with material specifications.
ASTM D2990 Analysis Results and Interpretation
Laboratories report the ASTM D2990 results based on the selected tensile, compressive, or flexural creep or creep-rupture procedure.
Laboratories report results for creep modulus in MPa, temperature in ºC, deformation in %, and time in seconds (s).
Laboratories can report creep modulus in MPa when the applicable calculation determines modulus from stress and strain.
Laboratories measure the applied load or stress, deformation or strain, time, temperature, specimen configuration, and environmental conditions.
Rohit Dhembare is an Operations Associate at Matestlab Inc., holds a postgraduate degree in Organic Chemistry and is trained in Materials Science testing techniques. Know More
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