# US 5,344,685 A · Production of composite sandwich structures > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,344,685 A - Document ID: US5344685A - Status: Granted - Kind: A - Application number: 08/024,340 - Filed: 1993-03-01 - Granted: 1994-09-06 - Earliest claimed: 1993-03-01 - Assignees: McDonnell Douglas Corporation - Inventors: George Cassell - Web page: https://patentgrep.com/patent/US5344685A ## CPC - B32B 5/245: {another layer next to it being a foam layer} - B32B 1/00: Layered products having a non-planar shape - B32B 3/18: characterised by an internal layer formed of separate pieces of material {which are juxtaposed side-by-side (B32B5/02 takes precedence)} - B32B 5/18: characterised by features of a layer {of} foamed material - B32B 5/32: {at least two} layers being foamed {and next to each other} - H01Q 1/422: {comprising two or more layers of dielectric material (H01Q1/425 takes precedence)} - B32B 2260/021: Fibrous or filamentary layer - B32B 2260/046: Synthetic resin - B32B 2262/101: Glass fibres - Y10T 428/21: Circular sheet or circular blank - Y10T 428/233: Foamed or expanded material encased - Y10T 428/249953: Composite having voids in a component [e.g., porous, cellular, etc.] - Y10T 428/249981: Plural void-containing components - B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM - H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## 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. ## Claims ### Claim 1 A foam core radome structure in the form of a contoured shell which comprises inner and outer facings on said shell, each formed of glass fabric impregnated with a resin and a contoured foam core disposed between said inner and outer facings, said foam core formed of a plurality of foam mandrel groups, each comprised of a multiplicity of straight relatively stiff narrow foam mandrels, one series of said foam mandrel groups being positioned in side-by-side relation in a substantially transverse direction in said shell, and another series of said foam mandrel groups being positioned in side-by-side relation in a substantially longitudinal direction in said shell, said foam mandrels being sufficiently narrow in width so as to conform to the contour of the shell. ### Claim 2 (depends on 1) The structure of claim 1, the adjacent foam mandrel groups in said one series of foam mandrels being in tightly fitting side-by-side relation, and the adjacent foam mandrel groups in said another series of mandrels being in tightly fitting side-by-side relation. ### Claim 3 (depends on 2) The structure of claim 2, wherein the adjacent mandrel groups in a substantially transverse direction are successively shorter in length and the adjacent mandrel groups in a substantially longitudinal direction are also successively shorter in length, the mandrel groups being applied with the inner ends of one mandrel group in a substantially longitudinal direction abutting the side of a mandrel group in a substantially transverse direction and the inner ends of a mandrel group in a substantially transverse direction abutting the side of a mandrel group in a substantially longitudinal direction. ### Claim 4 (depends on 1) The structure of claim 1, the adjacent foam mandrels of the foam mandrel groups being bonded together cured resin in the interfaces between the mandrels. ### Claim 5 (depends on 1) The structure of claim 1, said inner and outer facings each being formed of a plurality of plies of glass fabric impregnated with an epoxy resin. ### Claim 6 (depends on 1) The structure of claim 1, said foam core being formed of a polymeric alloy of cross-linked aromatic polyamide-urea and linear vinyl polymer, the density of said foam being about 7.+-.1 lb/ft.sup.3. ### Claim 7 (depends on 1) The structure of claim 1 , said foam mandrels having a thickness ranging from about 0.1 to about 0.5 inch and a width ranging from about 0.2 to about 0.75 inch. ### Claim 8 A foam core radome structure in the form of a contoured shell which comprises inner and outer facings on said shell, each formed of glass fabric impregnated with a resin, a contoured form core disposed between said inner and outer facings, said foam core formed of a plurality of foam mandrel groups, each comprised of a multiplicity of straight relatively stiff narrow foam mandrels, one series of said form mandrel groups being positioned in side-by-side relation in a substantially transverse direction in said shell, and another series of said foam mandrel groups being positioned in side-by-side relation in a substantially longitudinal direction in said shell, said foam mandrels being sufficiently narrow in width so as to conform to the contour of the shell, and a triangular piece of foam around the outer periphery of said foam core to form a transition, said inner facing and said outer facing extending over said transition to form an attach flange for said radome structure.