US-12623431-B2 - Foam sheet core for composite sandwich structures and method of making the same

Abstract

A foam sheet core, including a plurality of foam sheet walls defining an array of hollow cells, wherein the plurality of foam sheet walls are bonded together to form the array of hollow cells, each of the plurality of foam sheet walls has a thickness from about 0.002 inches to about 0.08 inches, and each of the plurality of foam sheet walls has an average height from about 0.05 inches to about 5 inches.

Inventors

• Xiaoxi Wang
• Gary E. Georgeson

Assignees

• THE BOEING COMPANY

Dates

Publication Date

20260512

Application Date

20240422

Claims (20)

1. 1 . A method of making a foam sheet core for a composite sandwich structure, comprising: stacking two or more foam sheets into a foam sheet block; fusion bonding the stacked foam sheet block; slicing the bonded foam sheet block into one or more strips of foam sheet; and expanding the one or more strips of foam sheet into a foam sheet core, wherein the two or more foam sheets comprise a foamed polymer with a relative density to solid from about 30% to about 80% and a melting temperature from about 270° F. to about 800° F., and wherein the foam sheet core comprises a plurality of foam sheet walls fusion bonded together to form an array of hollow cells.
2. 2 . The method of claim 1 , wherein the bonding of the stacked foam sheet block comprising fusion bonding the two or more foam sheets together as they are stacked into the foam sheet block.
3. 3 . The method of claim 2 , wherein the two or more foam sheets are fusion bonded using hot air with moving blocking plates.
4. 4 . The method of claim 2 , wherein the plurality of foam sheet walls comprise a foamed polymer having a relative density to solid from about 50% to about 60% that are fusion bonded together to form the array of hollow cells, and wherein the foam sheet core does not include an adhesive.
5. 5 . The method of claim 1 , further comprising filling one or more hollow cells of the array of hollow cells with a filling material.
6. 6 . The method of claim 5 , wherein the filling material comprises at least one of rubber foam, epoxy, phenolic, polystyrene (PS) foam, polyurethane (PU) foam, polyester foam, melamine foam, or combinations thereof.
7. 7 . The method of claim 6 , wherein the filling material is different from the foamed polymer forming the foam sheet walls, and wherein the filling material enhances at least one of a fire-retardance of the foam sheet core, a rigidity or stiffness of the foam sheet core, an acoustic insulation of the foam sheet core, an impact resistance of the foam sheet core, or combinations thereof.
8. 8 . The method of claim 1 , wherein each of the plurality of foam sheet walls has a thickness from about 0.002 inches to about 0.08 inches, and wherein each of the plurality of foam sheet walls has an average height from about 0.05 inches to about 5 inches.
9. 9 . The method of claim 8 , wherein each of the array of hollow cells has an average diameter from about 0.1 inches to about 1.0 inches.
10. 10 . The method of claim 1 , wherein the foamed polymer comprises at least one of phenolic, epoxy, polystyrene (PS), polyethylene (PE), polypropylene (PP), polyamide (PA), polyethylene terephthalate (PET), polyether ether ketone (PEEK), polyetherketoneketone (PEKK), polycarbonate (PC), polyetherimide (PEI), polyphenylsulfone (PPSU), thermoplastic polyurethane (TPU), acrylonitrile butadiene styrene (ABS), polyvinyl Chloride (PVC), polyurethane (PU), or combinations thereof.
11. 11 . The method of claim 10 , wherein at least one of the plurality of foam sheet walls comprises a different foamed polymer than the rest of the plurality of foam sheet walls.
12. 12 . The method of claim 1 , wherein the plurality of foam sheet walls further comprise reinforcing fibers, and wherein the reinforcing fibers comprise one or more of carbon fibers, fiberglass fibers, aramid fibers, ultra-high molecular weight polyethylene (UHMWPE) fibers, polyester fibers, polypropylene (PP) fibers, polyethylene (PE) fibers, polyamide fibers, or combinations thereof.
13. 13 . The method of claim 1 , further comprising coating the foam sheet core with a resin coat.
14. 14 . A method of making a composite sandwich structure comprising: providing one or more foam sheet cores; and fusion bonding the one or more foam sheet cores to one or more skin panels to form the composite sandwich structure, wherein the one or more foam sheet cores comprise a plurality of foam sheet walls fusion bonded together to form an array of hollow cells, and where the plurality of foam sheet walls comprise a foamed polymer with a relative density to solid from about 30% to about 80% and a melting temperature from about 270° F. to about 800° F.
15. 15 . The method of claim 14 , wherein the one or more foam sheet cores are formed by stacking two or more foam sheets into a foam sheet block, bonding the foam sheet block, slicing the bonded foam sheet block into a strip of foam sheet, and expanding the strip of foam sheet into a foam sheet core.
16. 16 . The method of claim 15 , wherein the plurality of foam sheet walls comprise a foamed polymer having a relative density to solid from about 50% to about 60% that are fusion bonded together to form the array of hollow cells, and wherein each of the plurality of foam sheet walls has a thickness from about 0.002 inches to about 0.08 inches.
17. 17 . The method of claim 16 , wherein the bonding of the foam sheet block comprises fusion bonding the two or more foam sheets together as they are stacked into the foam sheet block, and wherein the two or more foam sheets are fusion bonded using hot air with moving blocking plates.
18. 18 . The method of claim 14 , wherein the one or more foam sheet cores do not include an adhesive.
19. 19 . The method of claim 14 , wherein the one or more foam sheet cores are fusion bonded to the one or more skin panels.
20. 20 . The method of claim 19 , wherein the one or more skin panels are uncured before bonding, and wherein bonding the one or more foam sheet cores to the one or more skin panels comprises applying a curing temperature or pressure to the one or more skin panels to fusion bond the one or more foam sheet cores to the one or more skin panels.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. patent application Ser. No. 17/370,259 filed on Jul. 8, 2021, which is incorporated by reference herein in its entirety. TECHNICAL FIELD The present disclosure generally relates to composite sandwich structures, and more particularly, to foam sheet cores for composite sandwich structures and methods for making the same. BACKGROUND Composite sandwich structures generally include a core sandwiched between two face sheets. Often, the core includes cells or air pockets to reduce the weight of the composite sandwich structure as compared to equivalent structures made of solid materials. This reduced weight has led to increased use of composite sandwich structures in the aerospace industry to reduce the weight of aircraft components. The core may be formed of various materials, including, but not limited to, metal, laminate, or paper honeycombs, or solid or machined polymer foams. The face sheets may be formed from composite sheets, such as those formed of multiple laminated plies of a fiber reinforced resin. However, a number of chemicals are involved in the creation of traditional honeycombs, such as adhesives and thermoset resins, which are difficult to recycle. In addition, traditional honeycomb cores have almost reached a limit in the weight reduction they offer, while traditional foam cores lack the large open cells of honeycomb cores. Accordingly, there is a need for composite sandwich cores that offer improvements in weight reduction and offer reduction in the use adhesives and thermoset resins, as well as offering variability of core density. In addition, there is a desire for composite sandwich cores that require no curing process or may be formed as an out of autoclave process. BRIEF SUMMARY This summary is intended merely to introduce a simplified summary of some aspects of one or more implementations of the present disclosure. This summary is not an extensive overview, nor is it intended to identify key or critical elements of the present teachings, nor to delineate the scope of the disclosure. Rather, its purpose is merely to present one or more concepts in simplified form as a prelude to the detailed description below. The foregoing and/or other aspects and utilities exemplified in the present disclosure may be achieved by providing a foam sheet core, including a plurality of foam sheet walls defining an array of hollow cells, wherein the plurality of foam sheet walls can be bonded together to form the array of hollow cells, wherein each of the plurality of foam sheet walls can have a thickness from about 0.002 inches to about 0.08 inches, and wherein each of the plurality of foam sheet walls can have an average height from about 0.05 inches to about 5 inches. The plurality of foam sheet walls can be fusion bonded together to form the array of hollow cells, the foam sheet core can consist essentially of the plurality of foam sheet walls defining the array of hollow cells, and the foam sheet core may not include an adhesive. Each of the array of hollow cells can have an average diameter from about 0.1 inches to about 1.0 inches and an average height from about 0.05 inches to about 5 inches. The plurality of foam sheet walls can include a foamed polymer, and the foamed polymer can include at least one of phenolic, epoxy, polystyrene (PS), polyethylene (PE), polypropylene (PP), polyamide (PA), polyethylene terephthalate (PET), polyether ether ketone (PEEK), polyetherketoneketone (PEKK), polycarbonate (PC), polyetherimide (PEI), polyphenylsulfone (PPSU), thermoplastic polyurethane (TPU), acrylonitrile butadiene styrene (ABS), polyvinyl Chloride (PVC), polyurethane (PU), or combinations thereof. At least one of the plurality of foam sheet walls can include a different foamed polymer than the rest of the plurality of foam sheet walls. The foamed polymer can have a relative density to solid from about 2.5% to about 100% and a melting temperature from about 270° F. to about 800° F. The plurality of foam sheet walls can further include reinforcing fibers, and the reinforcing fibers can include one or more of carbon fibers, fiberglass fibers, aramid fibers, ultra-high molecular weight polyethylene (UHMWPE) fibers, polyester fibers, polypropylene (PP) fibers, polyethylene (PE) fibers, polyamide fibers, or combinations thereof. At least one of the hollow cells in the array of hollow cells can include a filling material, and the filling material can include at least one of rubber foam, epoxy, phenolic, polystyrene (PS) foam, polyurethane (PU) foam, polyester foam, melamine foam, or combinations thereof. The filling material can be different from the foamed polymer forming the foam sheet walls, and the filling material can enhance at least one of a fire-retardance of the foam sheet core, a rigidity or stiffness of the foam sheet core, an acoustic insulation of the foam sheet core, an impact resistance of the foam sheet core, or co