ASTM C393 specifies a bend testing procedure for sandwich constructions of composite materials in order to analyze the shear properties of the core. This batch of tests is used as a shear test of the core materials, rather than a flexure test of the entire beam. ASTM D7250 covers the flexure tests. ASTM C393 is focused on obtaining the core shear strength or the core-to-facing shear strength of the sandwich beam.
This test procedure uses a sandwich construction which is flat and beam shaped. The form of the core material may be continuously bonded such as with foam, or could be discontinuous such as with a honeycomb structure.
A three point bending fixture is needed to perform the ASTM C393 test. The specific dimensions of the span points and the bend fixture are specified in the official ASTM publication.
Calculations for ASTM C393 are focused on the shear properties of the core sandwich material. The core shear strength and shear modulus calculation can be analyzed seperately from the core-to-facing and the entire sandwich beam.