ASTM D6415 Composite Curved Beam Strength Testing

ASTM D6415 | Composites | Bend Testing

ASTM D6415 is a testing standard designed to measure the curved beam strength properties of fiber reinforced composites using a 90˚ curved beam specimen. The curved beam strength represents the moment per unit width which causes a delamination to form. The curved beam specimen consists of two legs connected by a 90˚ bend with a 6.4 mm (0.25 in) inner radius. It is loaded in four-point bending to apply a constant bending moment across the curved test section. An out-of-plane tensile stress is produced in the curved section of the specimen to cause failure.

This test method may also be used to measure the interlaminar tensile strength if a unidirectional specimen is used where the fibers run continuously along the legs and around the bend.

The test utilizes a standard universal testing machine with a four-point bend fixture. The cylindrical loading bars of the bend fixture should have diameters of 6 to 10 mm (0.25 to 0.40 in.) and be mounted on roller bearings. The span length for the bottom bar should be 100 mm (4 in) and the span length for the top bar should be 75 mm (3 in). Before conducting ASTM D6415, it is important to read the entire specification in the relevant ASTM publication.