Lightweight sandwich structures and methods of manufacturing the same

Abstract

A method of forming a sandwich structure including at least partially filling an open volume of an open cellular core with a sacrificial mold material, consolidating the sacrificial mold material to form a sacrificial mold, laying up a composite facesheet on each of at least two surfaces of the open cellular core, co-curing the composite facesheets by applying a consolidation temperature and a compaction pressure to the composite facesheets to form the sandwich structure, and removing the sacrificial mold. The compaction pressure is greater than a compressive strength of the open cellular core and less than a combined compressive strength of the open cellular core and the sacrificial mold.

What is claimed is: 
     
         1 . A sandwich structure comprising:
 an open cellular core having a first surface and a second surface opposite the first surface, the open cellular core defining an open volume;   a first composite facesheet bonded to the first surface of the open cellular core, the first composite facesheet conforming continuously to the open cellular core along the first surface; and   a second composite facesheet bonded to the second surface of the open cellular core, the second composite facesheet conforming continuously to the open cellular core along the second surface.   
     
     
         2 . The sandwich structure of  claim 1 , wherein the open cellular core comprises a plurality of interconnected struts arranged in a lattice structure. 
     
     
         3 . The sandwich structure of  claim 2 , wherein each strut of the plurality of interconnected struts has a hollow cross-section. 
     
     
         4 . The sandwich structure of  claim 2 , wherein each strut of the plurality of interconnected struts has a solid cross-section. 
     
     
         5 . The sandwich structure of  claim 2 , wherein the lattice structure comprises a plurality of repeating unit cells. 
     
     
         6 . The sandwich structure of  claim 2 , wherein the lattice structure comprises a plurality of repeating half unit cells. 
     
     
         7 . The sandwich structure of  claim 2 , wherein the plurality of interconnected struts comprise at least one material selected from the group consisting of metal, silicon carbide, silicon oxycarbide, alumina, silicon carbonitrile, polymer, ceramic, and combinations thereof. 
     
     
         8 . The sandwich structure of  claim 1 , wherein the open cellular core has a density in a range from about 0.02 grams per cubic centimeter to about 1 gram per cubic centimeter. 
     
     
         9 . The sandwich structure of  claim 1 , wherein each of the first composite facesheet and the second composite facesheet comprises a plurality of plies and a matrix around the piles. 
     
     
         10 . The sandwich structure of  claim 9 , wherein at least one sheet selected from the group consisting of the first composite facesheet and the second composite facesheet is bonded to the open cellular core only by excess in material of the matrix of the one sheet. 
     
     
         11 . The sandwich structure of  claim 9 , wherein the matrix comprises at least one material selected from the group consisting of epoxy, silicone, urethane, cyanate ester, polyimide, bismaleimide, acrylate, carbosilane, siloxane, sequisiloxane, and combinations thereof. 
     
     
         12 . The sandwich structure of  claim 9 , wherein each of the first composite facesheet and the second composite facesheet further comprises a fiber reinforcement. 
     
     
         13 . The sandwich structure of  claim 12 , wherein the fiber reinforcement comprises a at least one material selected from the group consisting of carbon, glass, alumina, silicon carbide, boron, aramid, polyethylene, and combinations thereof. 
     
     
         14 . The sandwich structure of  claim 12 , wherein the fiber reinforcement comprises a fiber reinforcement ply having at least one configuration selected from the group consisting of continuous unidirectional fibers, woven fibers, knit fibers, braided fibers, discontinuous chopped fibers, whiskers, platelets, particulates, and combinations thereof. 
     
     
         15 . The sandwich structure of  claim 12 , wherein a fiber volume fraction of at least one sheet selected from the group consisting of the first composite facesheet and the second composite facesheet is at least about 65%. 
     
     
         16 . The sandwich structure of  claim 1 , wherein:
 each of the first composite facesheet and the second composite facesheet has a thickness of about 1 mm; and   the open cellular core has a thickness in a range from about 0.5 mm to about 50 mm.   
     
     
         17 . The sandwich structure of  claim 1 , wherein the open volume extends along three orthogonal axes. 
     
     
         18 . The sandwich structure of  claim 1 , wherein at least one sheet selected from the group consisting of the first composite facesheet and the second composite facesheet is curved. 
     
     
         19 . The sandwich structure of  claim 1 , wherein:
 the open cellular core comprises a plurality of interconnected struts arranged in a lattice structure;   the open cellular core has a density in a range from about 0.02 grams per cubic centimeter to about 1 gram per cubic centimeter;   each of the first composite facesheet and the second composite facesheet comprises a plurality of plies and a matrix around the piles;   each of the first composite facesheet and the second composite facesheet has a thickness of about 1 mm; and   the open cellular core has a thickness in a range from about 0.5 mm to about 50 mm.   
     
     
         20 . The sandwich structure of  claim 19 , wherein:
 the lattice structure comprises a plurality of repeating half unit cells;   the plurality of interconnected struts comprise at least one material selected from the group consisting of metal, silicon carbide, silicon oxycarbide, alumina, silicon carbonitrile, polymer, ceramic, and combinations thereof; and   at least one sheet selected from the group consisting of the first composite facesheet and the second composite facesheet is bonded to the open cellular core only by excess in material of the matrix of the one sheet.