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SPECIFICATIONS

DESIGN DATA FOR HONEYCOMB SANDWICH PANELS

This section presents design criteria for structural sandwich panel constructions under various types of loading.   Detailed design procedures are presented for determining deflections of sandwich panels or beams and buckling of sandwich columns and simply supported panels under edge loadings.  Also included are formulas for calculating facing stresses and core shear stresses.

A structural sandwich is a layered construction formed by bonding two thin facings to a thicker core.  The basic design concept is to space strong thin facings far enough apart with a thick core to assure the combination will be stiff, to provide a core that is stiff and strong enough to hold the facings flat with an adhesive layer, and to provide a core material of sufficient shearing resistance.  The structural sandwich panel is analogous to an I-beam, with the facings carrying compression and tension loads, as do I-beam flanges, and the core material carrying shear loads, as does the I-beam web.

The American society for Testing Materials under their classification ASTM C274-53 defines a structural sandwich as follows: "A laminar construction comprising a combination of alternating dissimilar simple or composite materials assembled and intimately fixed in relation to each other so as to use the properties of each to attain specific structural advantages for the whole assembly."

In conventional beam formulas for maximum deflection the product of the moment of inertia I and the modulus of elasticity E is the measure of stiffness and is expressed as the composite term EI.  Honeycomb type core contributes nothing to the stiffness of a sandwich construction other than to make the two faces function as a unit.  The stiffness, EI, of a given construction is therefore based entirely upon the physical properties and dimensions of the two faces.