Production of composite sandwich structures

Abstract

Contoured sandwich radomes and other composite structures having a core consisting of a series of flexible foam mandrels laid side-by-side, with inner and outer facings made up of a fabric impregnated with a resin system, capable of providing superior breakdown voltage characteristics when cured in one stage. Such structures are obtained by a process comprising laying a plurality of first plies of resin impregnated fabric in a contoured mold to form an outer facing, providing a plurality of narrow straight but flexible mandrels of plastic foam, laving individual groups of such foam mandrels in side-by-side relation onto the outer facing, one series of the foam mandrel groups positioned in a substantially transverse direction in the mold and another series of the foam mandrel groups positioned in a substantially longitudinal direction in the mold. The inner ends of the mandrel groups abut the sides of adjacent mandrel groups, to form a foam core. The mandrels which are essentially straight before being installed in the mold are kept from springing up from the mold contour by a restraining collar which the outer ends of the mandrels abut, the collar being removed after the mandrels have been pressured under vacuum. A plurality of second plies of resin impregnated fabric are laid over the foam core, and the plies of resin impregnated fabric are cured to form the inner and outer facings.

Dependencies are inferred from the claim text.