Due to anisotropic properties of honeycombs, MIL handbook 17B does not recommend ASTM C393, or 3 point bend test as a valid indicator of honeycomb cored panel behavior. It is viewed as a possible quality control test but not indicative of the real attributes of the structure. It is generally felt that a better indicator would be the ASTM D 6146-99) (Standard Test Method for Two-dimensional Flexural Properties of Simply Supported Sandwich Composite Plates Subjected to a Distributed Load) or also known as "The Hydramat test". These tests have produced results that validate the accompanying Strength of Materials Data. The viscoelastic behavior of Nida-Core Polypropylene Honeycomb will typically permit far greater deflections without structural failures so the Deflection at Load is supplied for comparison but this does not imply a Load to fail.
