How to Perform ASTM D1621 Plastic Compression Testing

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Summary of Test

ASTM D1621 is a test method used to determine the compressive properties of rigid cellular materials, particularly expanded plastics. The calculations that can be derived from this method include compressive strength, compressive strain, compressive stress and Modulus of Elasticity.

A universal testing machine capable of performing a compression test at a constant crosshead speed with enough force capacity to compress the specimen by 13% of its height is needed to perform this test. Before conducting ASTM D1621, it is important to read the entire specification in the relevant ASTM publication.

eXpert 2600 Universal Testing System
eXpert 7600 Universal Testing System
eXpert 5600 Modular Electromechanical Testing System

Compression Platens
Deflectometer

Testing Procedure

Prepare the specimen as described in the standard. The specimen should be square or circular in cross section with a minimum of 25.8 cm2 (4 in2) and maximum of 232 cm2 (36 in2). Minimum height should be 25.4 mm (1 in) and the maximum height shouldn’t exceed the width or the diameter of the specimen.
Place the specimen between the compression platens ensuring it is aligned with the center-line of the platen. Attach the deflectometer.
Apply a compressive force at a crosshead displacement of 2.5 mm/min (0.1 in/min) for each 25.4 mm (1 in) of specimen thickness.
Stop test when the sample is compressed by 13% of its height. Record force and deformation data.

Calculations:

If no yield point is observed determine the force at 10% deformation.
If a yield point is observed, report the force at the yield point and determine the percent deformation at the yield point.
Compressive Modulus
Apparent Modulus