ASTM D790 Bend Test

ASTM D790 is commonly used in the plastics industry for measuring the flexural properties of unreinforced and reinforced plastics. This test can also be used on high-modulus composites and electrical insulating materials. The resulting data is often used to select materials for parts that will support loads without flexing.


These test methods utilize a three-point loading system applied to a simply supported beam. ASTM D790 has two possible procedures. Procedure A is used for measuring flexural properties such as flexural modulus, and Procedure B can be used for measurement of flexural strength. Procedure A is typically for materials that can break at small deflections, where B is used for stronger specimens. Since most materials can vary in strength depending on their ambient temperature, it may be best to test the materials at their intended environmental temperature.

Testing Procedure

A test sample bar rests on two supports and is loaded by means of a loading nose midway between the supports. A support span-to-depth ratio of 16 to 1 is generally used. The specimen is deflected until a breaking point occurs in the outer surface of the test specimen or until a maximum strain of 5 per cent is reached.

We recommend using a versatile universal testing machine with a three point bend fixture to bend plastic test bar specimens. If temperature is a factor in your testing, consider an environmental chamber. By means of our testing expertise and modular product design, we will help find the testing solution that is right for you. Give one of our application engineers a call today for help with creating the best budget and testing plan according to ASTM D790.

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