Flexure test methods

This standard was based on ISO 178 - flexure testing of plates supported by ASTM D790, JIS 7074, EN 63, CRAG 200, EN Aerospace 2562 and 2746. The major changes are the addition of a 4-point loading configuration (see Figure II) and a larger test span-to-specimen thickness ratio for unidirectional carbon-fibre based systems. Materials are divided into four classes related to their structure and ratio of Young's Modulus (E) to through-thickness shear modulus(G13).

The different spans partly ensure that the error in the apparent flexural modulus due to the deformation occurring in shear is similar. The error increases with increasing ratio of E/(G13). Care is required in determining the failure mode. In some cases failure of the compression face can be avoided by the, optional, use of a 0.2 mm thick pad of polypropylene beneath the centre loading roller, following Japanese practice. However, flexure tests would not be recommended for the determination of design data.