ESDU STRUCT 07.03.01:1974

ESDU Struct 07.03.01 considers the transverse stiffness of a symmetrical sandwich panel in which the core and identical face-plates are of the same material. The corrugated core cross-section (that is, in a plane normal to the face-plates) is assumed to be composed of straight portions joined by circular arcs of a specific radius, in this case 0.18 of the core depth. However, it is noted that variations in that value from 0.12 to 0.27 associated with variations in the ratio of the corrugation thickness to face-plate thickness from 0.6 to 1.25 change shear stiffness by only 15 per cent. The corrugations may be of a different thickness from the face-plates. A graph gives five sets of curves for a shear stiffness factor as a function of the corrugation geometry (its pitch, depth and thickness), each set for a value of the angle made by the transverse portion of the corrugations with the face-plates. Each set consists of four curves each for a fixed value of the ratio of the core depth to the corrugation thickness. The stiffness factor is related to the transverse stiffness through an equation involving the material elastic modulus and Poisson's ratio together with the geometry of the corrugations and the thickness of the face-plates. It is noted that the transverse stiffness is affected by the method of attaching the corrugations to the face-plates; here it is assumed that they are attached by a line weld and the values should be considered to be only a guide if adhesive, rivet or spot welded connections are used. A worked example illustrates the use of the curves.

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