Flexural Properties of Composites ASTM D7264
Flexural testing is a widely used method for evaluating the mechanical properties of materials, particularly polymer matrix composites. The American Society for Testing and Materials (ASTM) has established various standards for testing the flexural properties of materials. One such standard is ASTM D7264, which outlines the testing of flexural properties of polymer matrix composites using a bar of rectangular cross section supported on a beam and deflected at a constant rate.
ASTM D7264 comprises two procedures for flexural testing, namely Procedure A and Procedure B. Procedure A uses a three-point loading system for center loading, while Procedure B uses a four-point loading system for two equal loading points. The test method is specifically designed for polymer matrix composites and uses a standard 32:1 span-to-thickness ratio in comparison to other methods such as ASTM D790, a three-point flexure for plastics, which uses a standard 16:1 span-to-thickness ratio or ASTM D6272 which is a four-point flexure. Additionally, fabric-reinforced textile composite materials are also referenced within the ASTM D7264 method.
The test procedure involves placing the specimen on a support span and applying a load at a constant rate either to the center or two equal loading points. Elevated or reduced temperature testing can also be conducted using a thermal chamber that is installed on the Universal Testing Machine. The chamber allows the test mounts from the base and crosshead of the Tester to pass through the top and bottom of the chamber, with standard test fixtures installed inside the chamber.
The standard specimen size for flexural testing according to ASTM D7264 is 4 mm (0.16 in) in thickness, 13 mm (0.5 in) in width, and 20% longer than the support span. However, alternative specimen sizes may be used if the standard specimen is not available.
The data obtained from flexural testing includes the flexural strength, maximum flexural stress, maximum strain, stress at strain, flexural secant modulus of elasticity, flexural chord modulus of elasticity, and failure mode and location.
Flexural testing is an essential tool for evaluating the mechanical properties of materials, particularly polymer matrix composites. ASTM D7264 provides a standardized test procedure that ensures consistency and accuracy in test results.