ASTM D6415 is 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.
Before conducting ASTM D6415, it is important to read the entire specification. Standards can be obtained from appropriate standard authorities.