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National Advisory Committee for Aeronautics, Technical Notes - Compressive Buckling of Flat Rectangular Metalite Type Sandwich Plate With Simply Supported Loaded Edges and Clamped Unloaded Edges

A theoretical solution is obtained for the problem of the compres—
sive buckling of flat rectangular Metalite type sandwich plates with
simply supported loaded edges and clamped unloaded edges. The solution
is based upon the general small-deflection theory for flat sandwich
plates developed in NACA Rep. 899. A comparison is made of the present
results and other solutions of the problem.

A comparison is also made between the present theory and experi-
mental results for two types of sandwich plates: plates having alclad
2hS-T aluminum-alloy faces and end-grain balsa—wood or cellular-cellulose—
acetate cores. Better agreement is found between computed and experi—
mental buckling stresses of sandwich plates with cellular-cellulose-
acetate cores than for sandwich plates having end-grain balsa-wood cores.

The increasing use of sandwich materials in aircraft design makes
the problem of analyzing the buckling of sandwich plates one of impor-
tance. Since sandwich plates cannot be analyzed by ordinary plate theory
because of the appreciable effect of low core shear stiffness on deflec—
tions, a general small-deflection theory for elastic bending and buckling
of flat sandwich plates was developed in reference 1. This theory was
extended to include plastic buckling in reference 2 and was applied to
the problem of the elastic and plastic compressive buckling of simply
supported flat rectangular Metalite type sandwich plates.

In the present paper, the elastic compressive buckling of flat rec-
tangular Metalite type sandwich plates with simply supported loaded edges
and clamped unloaded edges (fig. 1) is investigated. The differential
equations of reference 1 are solved to yield a stability criterion giving
elastic-buckling—stress coefficients implicitly in terms of the plate »
aspect ratio and the ratio of the plate flexural stiffness to the core
shear stiffness. Charts are presented to facilitate the determination
of elastic-compressive-buckling loads and an approximate correction for
plasticity is outlined.