The Use of Miniature Disc Bend Tests with Plastic Materials

The use of miniaturised disc bend tests, a method that is commonly used with metallic materials, is assessed for use with polymeric materials. The test method uses the indention force/displacement characteristics for a hemispherical-ended punch forced onto a small disc of the test material. Characterisation tests were performed using acetal, PMMA and polypropylene, under a range of different test rates and temperatures. These were compared with conventional tensile tests under the same conditions. Although no quantitative comparison between the two methods has been formulated, good qualitative agreement was found for all materials, including a wider comparison with nine materials. The advantages of the disc bend test are that smaller amounts of material are needed, the sample preparation is easier, the test is often easier to perform, it shows ductile–brittle transitions more sharply and is a very convenient method of performing environmental stress cracking tests.