Flexural Properties Testing

Flexural Properties Testing: Understanding the Scope, Procedure, and Importance

Flexural properties testing is an important method for measuring the force required to bend a beam under three point loading conditions. This test is often used to select materials for parts that will support loads without flexing, and to determine the stiffness of a material when flexed. In this article, we will discuss the scope, procedure, and importance of flexural properties testing.

Scope of Flexural Properties Testing

The flexural test is conducted on a specimen that is placed on a support span, and the load is applied to the center by the loading nose producing three point bending at a specified rate. The parameters for this test are the support span, the speed of the loading, and the maximum deflection for the test. These parameters are based on the test specimen thickness and are defined differently by ASTM and ISO. ASTM D790 specifies that the test is stopped when the specimen reaches 5% deflection or the specimen breaks before 5%. In contrast, for ISO 178, the test is stopped when the specimen breaks. If the specimen does not break, the test is continued as far as possible, and the stress at 3.5% (conventional deflection) is reported.

The physical properties of many materials, especially thermoplastics, can vary depending on the ambient temperature. Therefore, it is sometimes appropriate to test materials at temperatures that simulate the intended end-use environment. To test the flexural properties of materials at elevated or reduced temperatures, a thermal chamber is installed on the universal test machine. The chamber is designed to allow the test mounts from the base and crosshead of the universal tester to pass through the top and bottom of the chamber. Standard test fixtures are installed inside the chamber, and testing is conducted inside the controlled thermal environment, the same as it would be at ambient temperature. The chamber has internal electric heaters for elevated temperatures, using external carbon dioxide gas as a coolant for reduced temperatures.

Specimen Size for Flexural Properties Testing

A variety of specimen shapes can be used for this test, but the most commonly used specimen size for ASTM is 3.2mm x 12.7mm x 125mm (0.125" x 0.5" x 5.0") and for ISO is 10mm x 4mm x 80mm.

Importance of Flexural Properties Testing

Flexural properties testing is a critical method for selecting the right materials for parts that will support loads without flexing. It is used to determine the stiffness of a material when flexed and to identify the physical properties of materials at elevated or reduced temperatures. The data obtained from this test is useful in designing and developing products for a wide range of applications, from consumer goods to industrial equipment.

In our opinion, flexural properties testing is an important method for evaluating the physical properties of materials under flexural loads. The procedure involves measuring the force required to bend a beam under three point loading conditions, and the parameters for this test are defined differently by ASTM and ISO. This test is useful in selecting the right materials for parts that will support loads without flexing, and in identifying the physical properties of materials at elevated or reduced temperatures.