vierpunkt The flexural test using ASTM D 7264-07 is a 3-/ 4-Point-flexural test for the characterization of flexural properties of fibre reinforced thermosettings or thermoplasts. The test is conducted at constant speed of 1mm/s for standard samples until failure or a predefined deformation, while deformation and load are monitored. The samples are rectangular and flat with a length:height ratio of 32:1.

The 4-point flexural test provides a constant distribution of strain and deformation between the two loading pins which produces a smaller maximum shear stress in comparison to the 3-point flexural test.

Please note: To obtain valid flexural strength, the failure of the specimen must occur on either one of its outer surfaces, without a preceding interlaminar shear failure or a crushing failure under a support or loading nose. Failure on the tension surface may be a crack while that on the
compression surface may be local buckling. Buckling may be manifested as fiber micro-buckling or ply-level buckling. Ply-level buckling may result in, or be preceded by delamination
of the outer ply.