Flexural Properties of Composites by ASTM D7264

Flexural properties ASTM D7264 Scope:
ASTM D7264 outlines 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. The test method summarizes two procedures. Procedure A outlines a three point loading system for center loading. Procedure B outlines a four point loading system for two equal loading points. This test method is 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. Fabric-reinforced textile composite materials are also referenced within the ASTM D7264 method.

Flexural properties of many materials can vary depending on temperature, rate of strain and specimen thickness, it may be appropriate to test materials at varied parameters.

Test procedure:
Procedure A outlines a three point loading system for center loading. Most commonly the specimen lies on a support span and the load is applied to the center by the loading nose producing three-point bending at a specified rate. Procedure B outlines a four point loading system for two equal loading points. For the four point flexural test, the specimen lies on a span and stress is uniformly distributed between the loading noses.

Elevated or reduced temperature test procedure:
A thermal chamber is installed on the Universal Testing Machine. The chamber is designed to allow the test mounts from the base and crosshead of the 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 and uses external carbon dioxide gas as a coolant for reduced temperatures.

Specimen size: Standard specimen thickness is 4 mm (0.16 in), standard specimen width is 13 mm (0.5 in) and standard specimen length is 20% longer than the support span. If the standard specimen is not available, alternative specimen sizes may be used.

Data:
Flexural Strength
Maximum Flexural Stress
Maximum Strain
Stress at Strain
Flexural Secant Modulus of Elasticity
Flexural Chord Modulus of Elasticity
Failure Mode and Location

Equipment Used:
Universal Testing Machine
Four Point Flexural Fixture
Three Point Flexural Fixture