Advanced vacuum-enhanced origami composite sandwich panels and assembly methods for optimal thermal performance

Abstract

A vacuum insulated panel having an external skin and an internal core which together delimit channels and / or cells that are vacuously isolated from one another to ensure that the vacuum is robustly maintained while also providing a safeguard against system-5 wide failure, should the vacuum in one channel or cell be compromised, the vacuum insulated panel being configured for use independently or arranged in a succession with other such panels where shiplap, tongue-in-groove, and other geometries may be used to facilitate joinery and reduce thermal bridging.

Description

[0001]ADVANCED VACUUM-ENHANCED ORIGAMI COMPOSITE SANDWICH PANELS AND ASSEMBLY METHODS FOR OPTIMAL THERMAL PERFORMANCE TECHNICAL FIELD This disclosure concerns the realm of energy-efficient construction materials and methods, focusing on vacuum-enhanced composite sandwich panels. These panels have a wide array of applications, ranging from aerospace to construction, where superior thermal insulation and mechanical strength are prerequisites. BACKGROUND Traditionally, vacuum insulated panels (VIPs) have often been plagued by issues of thermal bridging and limited structural capabilities. In this way, VIPs are readily considered to be inefficient from a thermal context and too fragile in terms of structural capacity. Moreover, traditional VIPs are relatively expensive. As a result, for various applications, existing VIPs are economically inaccessible and structurally and thermally insufficient. Furthermore, conventional VIPs rely on microporous materials like aerogel or fumed silica, which achieve low thermal conductivity under moderate vacuum due to microscopic pores. However, this approach leaves the entire panel vulnerable to failure if the vacuum seal is compromised. Standard non-VIP insulating materials are cheaper and are often employed in transportation, aerospace, and construction applications. However, these traditional insulating materials are thermally inefficient and can be quite fragile. Accordingly, a new VIP is desired which provides limited thermal bridging, robust structural performance, ease of manufacture and assembly, and reduced cost. BRIEF SUMMARY A composite sandwich panel system is provided that employs a plurality of materials and innovative methods for joining and assembly. Unlike traditional insulation panels, the core of the panel is designed to maintain a vacuum, thereby substantially elevating its thermal insulation capabilities. The internal structure of the panel features a unique geometry of cells that are interconnected in a single dimension. This design ensures that the vacuum is robustly maintained while also providing a safeguard against system-wide failure, should the vacuum in one cell be compromised. Moreover, the assembly process using high surface area lap and scarf joints enables longer thermal paths to ensure reduced thermal bridging. The present disclosure builds upon existing technologies by synergistically integrating advanced materials and novel assembly methods. It aims to set new benchmarks in thermal insulation through its unique internal structure and vacuum-enhanced features. The solution presented herein is to take a structural panel and turn it into a vacuum insulated panel. Moreover, the structural panel is formed of a structured cellular material which is engineered to provided thermal anisotropy, and which can be used to further increase efficiency. The present disclosure utilizes a multifunctional cellular core design, where the panel is divided into isolated vacuum channels, and the configuration of the cellular core allows for sufficient compressive and shear stiffness and strength such that the vacuum does not collapse the material. Each channel is individually sealed, which compartmentalizes the vacuum within smaller regions. This redundant structure ensures that a puncture or vacuum loss in one channel does not compromise the thermal performance of the entire panel. By employing stronger vacuum levels and cellular materials with larger pores, the invention optimizes insulation while enhancing durability. This isolated channel approach prevents the collapse often associated with traditional microporous VIPs, thus increasing the panel’s longevity and resilience. The result is a new VIP which provides limited thermal bridging, robust structural performance, ease of manufacture and assembly, and reduced cost. BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts, in which: Figures 1(a) – 1(d) show top, isometric, right, and front views, respectively, of an exemplary embodiment of a unit cell of a core of a vacuum insulated panel; Figure 2 shows an exemplary embodiment of a core structure of a VIP formed by repeating the unit cell of Figure 1; Figure 3 shows an exemplary embodiment of a panel assembly including the core structure of Figure 2; Figures 4A-B show an exemplary embodiment of VIPs having a shiplap construction; Figure 5A-B show another exemplary embodiment VIPs having a tongue in groove construction; Figures 6A, 6B show plots of R values and strength of the disclosed core and VIP as compared to existing materials; Figure 7A shows a plot of theoretical predictions for thermal anisotropy; Figure 7B is a schematic cross section view of a VIP in one embodiment of the present disclosure; Figure 8: shows another exemplary embodiment of a core interior structure of a VIP in accordance with the present disclosure; Figure 9 is a partial enlarged view of Figure 8; Figure 10 is a partial enlarged view of Figure 9; Figure 11 shows a cross-sectional view of a panel formed with the core of Figures 8- 10; Figure 12 shows an exemplary embodiment of a core interior structure of a VIP in with shiplap joints, in accordance with the present disclosure; Figure 13 is a partial enlarged view of Figure 11; Figure 14 is another partial enlarged view of Figure 11; Figure 15A-B show a multi-layer thermal arrangement having a tongue-in-groove configuration; Figures 16A-B show the multi-layer thermal arrangement having shiplap configuration; and Figure 17 shows a cross sectional view of a VIP. DETAILED DESCRIPTION Figure 1 shows various views of a a representative unit cell 10 comprising polygonal intersecting facets 12 that combine to create a complex three-dimensional structure with interconnected internal cells whose mechanical and thermal properties are designed to have programmable orthotropic behavior, to promote isotropy or to control anisotropy. Figure 2 shows an example of an interior core structure 20 utilized in a vacuum insulated panel (VIP). The unit cell 10 or any of its parametric embodiments as described with reference to Figure 1, when tessellated in space, generates an ordered foam-like structure with mechanical and thermal properties determined from engineering calculations. Figure 3 shows a panel assembly 30 composed of the interior core structure 20 of Figure 2 and a structural skin 32 disposed on opposite sides of the core structure 20. The interior core structure 20, when combined with an impermeable membrane and the structural skin 32, forms a robust sandwich panel that can be used for structural purposes. A vacuum pump and quick release system is used to provide an evacuated region on the insides of the interior structure, thus forming a vacuum insulated panel and decreasing the overall thermal conductivity of the panel assembly. In one exemplary embodiment, the outer skin 32 of the panel 30 is crafted from high- strength, thin-gauge steel, ranging between about 80ksi to about 110ksi and having a thickness of about 0.013” to about 0.016”. Notably, the steel undergoes industry-standard treatments such as galvannealing or hot-dip galvanizing, often represented by alloys like ASME A653. These treatments, coupled with additional layers of primer coatings or paint, serve to enhance the material's corrosion resistance, thereby extending the panel's lifespan. The internal core 20 builds on Applicant’s previous work for developing pro-isotropic materials (known commercially as, “METACORE”), as disclosed, for example, in U.S. Patent Application Serial Numbers 18 / 012047, 18 / 277246, and 63 / 471699, the entire contents of which are hereby incorporated by reference. For the present application, the interior core 20 is primarily composed of advanced plastics known for their low outgassing characteristics – PVC, PE, PET. The core 20 features an open-cell structure specifically engineered to mitigate thermal conductivity and convection, thereby complementing the vacuum-enhanced insulation properties. Central to this disclosure is the method employed for achieving and maintaining the vacuum within the interior core 20. The vacuum is initiated using high-performance vacuum pumps, capable of achieving pressures as low as 10^-3 Torr. The core material 20 is enveloped in high-barrier films made from materials like metallized polyester or aluminum foil, which are known for their low permeability to gases. An edge sealant used to maintain the vacuum typically comprises specialized, low- outgassing silicone or epoxy resins. These materials ensure a hermetic seal, critical for long- term vacuum retention. Additionally, industry-standard vacuum bagging techniques are employed to envelop the panel during the vacuum process, further ensuring the integrity of the vacuum space. In terms of assembly, the present panels can employ a tongue-in-groove and shiplap geometry, designed to provide a large surface area for adhesive bonding, thereby maximizing the joint strength. Figures 4A-B illustrate panel assemblies 30 having a shiplap construction. Each panel 30 includes an internal core 20 comprising an outer skin 32 disposed on opposite major sides of the core 20. As can be seen particularly in Figure 4B, the skins 32 on the top of the cores 20 terminate in an aligned matter with a right edge of the core 20, whereas the skins 32 extend beyond a left edge of the cores 20. Similarly, as seen in the drawing, the skins 32 on the bottom of the cores 20 align in a terminal fashion with the left edge of the cores 20, while the skins 32 extend beyond the right side edge of the cores 20. This construction allows for an overlap region 34 at the interface of the panels 30 where the upper skin 32 of the right side panel 30 (as depicted in Figure 4B) overlaps the upper skin 32 of the left side panel 30. Similarly, the lower skin 32 of the left side panel 30 overlaps the lower skin 32 of the right side panel 32. The overlap provided by the present panel construction creates bonding areas where the overlapping skins 32 may be bonded to the underlying skins 32. This results in enhanced structural connection integrity, and reduces or eliminates the need for rivets or other mechanical fastening elements, thus minimizing thermal bridging and increasing overall efficiency of the panel assemblies 30. Figures 5A-B illustrate a panel assemblies 30 having a tongue in groove construction. As shown particularly in Figure 5B, the left side panel 30 has skins 32 disposed on opposite sides of the core 20, where the skins 32 extend beyond a right edge of the core 20 and which terminate before reaching the left edge of the core 20. This construction creates a ‘tongue’ at the left edge of the left side panel 30 and a groove at the right edge. The right side panel 32, as shown in the drawing, is of identical construction as the right side panel 32. That is, the right side panel 32 includes skins 32 which extend beyond a right edge of the core 20 and which terminate short of the left edge of the core 20, thus forming a complimentary tongue and groove arrangement. As illustrated, the tongue formed by the extending core 20 of the right side panel 32 is received in the groove formed by the extending skins 32 of the left side panel. This construction creates the overlap region 34 at which the adjacent panels 32 are adjoined. Particularly, the skins 32 of the left side panel 30 overlap the core 20 of the right side panel 30 creating bonding areas where the overlapping skins 32 may be bonded to the underlying core 20. Here again, this results in enhanced structural connection integrity, and reduces or eliminates the need for rivets or other mechanical fastening elements, thus minimizing thermal bridging and increasing overall efficiency of the panel assemblies 30. Additionally, the geometry is engineered to elongate the thermal path through the assembly, effectively reducing thermal bridging. That is, the techniques used for joining adjacent panels reduces or eliminates traditional fasteners, such as screws, bolts, rivets, etc., that would normally create short thermal pathways through which heat can rapidly migrate. In the panels of the present disclosure, elongated thermal pathways exist only across the outer skins, while shortened paths through the thickness of the panel are omitted. Thus, insulative capacity is increased. Further applicable joinery techniques are disclosed in International Patent Application Number PCT / US2024 / 032911 designating the U.S., and having an international filing date of June 07, 2024, the entire contents of which are herein incorporated by reference. In one exemplary embodiment, the skins 32 applied to the VIPs 30 may be formed of high strength steel having a thin gauge (e.g., 80ksi to 110ksi 0.013” to 0.016”). The steel may be treated in a manner consistent with industry standards. Representative alloys include ASME A653 galvannealed or hot dip galvanized steel, with appropriate backer or primer coatings, paint, and / or other surface treatments. In another exemplary embodiment, the structural skin 32 of the VIPs 30 may be formed of a fiber-reinforced thermoplastic composite. Continuous fibers, such as glass, carbon, basalt, boron nitride, jute, etc., or a combination thereof, may be embedded in a unidirectional tape, and then laid up in a multi-ply laminate with orientation optimized for the structural goals of the application. The internal core 20 of the VIPs 30 may be formed of plastic having open cellular structures of an appropriate size to minimize thermal conductivity and convection. The material utilized may be composed of a plastic with low outgassing characteristics (e.g. PVC, PE, PS, etc., or combinations thereof). Figure 6A illustrates theoretical predictions for R values of the internal core 20 individually and incorporated into a VIP 30, as compared to existing materials. More particularly, Figure 6A shows the results of applying a vacuum to the core 20 and panel assemblies 30 shown in Figures 1 through 3, and compares the thermal insulation provided thereby against other commonly used insulating materials. The x-axis shows the R value per inch, a measurement of thermal insulation per inch of thickness of the subject material. The y-axis displays the cost per footboard per R value. A footboard, or FBM, is defined as a unit of volume equal to 1” by 1 square foot. The plot provides a very dense representation of cost per thermal efficiency. An ideal material would fall within the area on the graph labeled as “unicorn zone”. The panel assembly 30 incorporating the internal core 20 of the present disclosure, as is shown in the graph, costs less than traditional VIPs while being more thermally efficient than cheap building materials like EPS and XPS. Figure 6B shows a similar chart comparing the compressive and shear strengths of the proposed panel 30 to existing materials, illustrating that the inventive panel is structurally superior when compared to known technologies, in addition to being thermally insulating. Adding vacuum insulation, in accordance with this disclosure, further increases efficiency. Figure 7A illustrates theoretical predictions for thermal anisotropy determined by geometric parameters and material selection. More particularly, Figure 7A displays how the structured cellular core gives rise to thermal conductivity anisotropy. Most materials like foams and aerogels used in conventional insulating materials are thermally isotropic, meaning that they conduct heat in the same manner in all relative directions. To the contrary, he structured cellular core 20 of the present disclosure, when surrounded by vacuum in the panel 30, conducts heat anisotropically. In this way, the panel 30 can be constructed to direct heat laterally across a surface, rather than through the thickness of the panel. This directs the heat away from the interior of a structure cladded with the panel 30 (e.g., cargo van, house, etc.), and can provide additional efficiency above and beyond pure insulating value. Figure 7B is a schematic of the core material, an impermeable membrane, and the structural skin. Particularly, a gas-impermeable membrane 38 is disposed on both sides of the core 20 and the structural skin 32 is applied over the membrane 38. The membrane 38 can be formed of any material sufficient for rendering the core 20 gas-impermeable, for example, the membrane 38 may be formed of polyamides, ethylene vinyl alcohol, or aluminized biaxially oriented polyethylene teraphthelate, or a combination thereof. The illustrated layers of the panel 20 may be affixed to one another using thermal bonding, coextrusion, adhesive bonding, or any suitable technique for ensuring reliable fixation. Figures 8-10 show various views of another embodiment of an internal core 40 which may be incorporated into the vacuum insulated panel disclosed herein. Here, the core 40 includes a plurality of intersecting polygonal facets 42 which repeat to form an array. The facets 42 are designed to promote isotropic properties and to increase a shear strength density scaling and increased contact area for enhanced adhesion to mating surfaces. On each side of the core 40, an outward extent of the polygonal facets 42 include coplanar surfaces which facilitate bonding of the core 40 to the skins 32, as discussed further herein. The polygonal facets 42 comprise a plurality of the bonding structures 44 extending across a front side of the core 40 and, correspondingly, in mirror like fashion, across a rear side. These bonding structures 44 intersect at an intersection axis A-A which traverses a length of the illustrated portion of the core 40. This arrangement is repeated across the core 40 to form a herringbone-like pattern (see, e.g., FIG.8). The bonding structures 44 at the front side of the core 40 are coplanar with one another, and the bonding structures 44 at the rear side of the core 40 are coplanar with one another. Across the length of the core 40, the bonding structures 44 alternate between the front side and the rear side and are connected by alternating angled polygonal portions 46. In the illustrated example, the angled polygonal portions 46 extend at about 135orelative the bonding portions 44. Likewise, the bonding structures 44 and the angled polygonal portions 46 extend at an angle of 135orelative the intersection axis A-A form a repeating V-shape pattern on the core 40. Figures 11A-B show a cross sectional view of a VIP 50 formed with the internal core 40. The skins 32 are affixed to opposing sides of the core 40. More specifically, the skins 32 are bonded via adhesive or other comparable technique to the coplanar surfaces of the bonding structures 44 of the core 40. As a result, individual channels 48 are delimited by skins 32, the angled polygonal portions 46, and the bonding structures 44. With this construction, every channel 48 is isolated from every other channel 48. A vacuum is applied to the channels 48 to remove entrapped gas and reduce air pressure. Edges of the panel 50 are sealed to form the VIP. As described herein, the resulting VIP 50 has robust structural properties and is highly thermally insulative. Moreover, because each channel 48 is isolated from every other channel 48, failure of the vacuum in one channel 48, e.g., due to puncture, does not effect the vacuum condition in the remaining channels 48. Figures 12 -14 show various views of the panel 50 of Figure 11 with the skins 32 arranged thereon in a shiplap configuration. That is, as shown in Figure 12, the skin 32 on the front face of the panel 50 terminates at a lower edge of the core 40, whereas the skin 32 terminates short of the upper edge of the core 40. On the opposite rear side of the panel 50, the skin 32 terminates at the upper edge of the core 40 and stops short of the lower edge of the core 40. This panel 50 may be adjoined to a second panel 50 as described above with reference to Figure 4. Figures 15-16 show multi-layer thermal arrangements 60, each comprising two vacuum insulated panels 50 arranged parallel to one another with an insulating layer 62 disposed therebetween. The insulating layer 62 may be a traditional aerogel or fumed silica material. The panels 50 may be disposed upon the insulating layer 62 so as to form a tongue in groove arrangement, as shown in Figures 15A-B, or a shiplap arrangement, as shown in Figures 16A-B, in order to facilitate joinery, similarly to that described above with regard to Figures 4-5. The multi-layer thermal arrangement 60 is illustrated as including the panels 50, but may alternatively include the panels 30, or a combination of the panels 30 and 50, or any other panels falling within the broad scope of this disclosure. Figure 17 shows an edge view of the VIP 50 and a cross-section thereof taken along line B-B. As illustrated in this embodiment, an adhesive spacer or sealant 52 is laid down on the perimeter of the panel. This spacer 52 has chemistry chosen to be compatible with the skin materials so that it bonds appropriately. For example, the spacer 52 may be formed of a polyisobutylene primary sealant, a silicone-based sealant, or a reactive thermoplastic. The spacer / sealant element 52 can also be seen in Figures 11B, 15B, and 16B. In one embodiment, the VIP 50 is formed using a traditional insulating glass manufacturing line. A first structural skin 32 is shuttled down a conveyor belt and has the reactive thermoplastic spacer 52 applied to its edges. Then the skin 32 is shuttled further down the line to be attached to the core 20 and the opposing skin 32. Before the sealant cures, the conveyor shuttles the assembly to a ledge that temporarily pries the edges apart at a leading edge, and argon is flood-filled into the channels 48. The panels are then pressed and cured. The vacuum insulated panel described herein is designed to be thermally bonded to structural composite skins, eliminating the need for high outgassing adhesives, although low outgassing epoxies, sealants, and adhesives may be used for certain material choices. Sealing between individual channels and vapor barriers between the core and the structural skins are accomplished using aluminized plastics that are amenable to thermal bonding, or ethylene vinyl alcohol (EVOH) or polyamides co-extruded on the core material prior to thermoforming. Because the sandwich panel is composed of materials that are amenable to bonding to one another, joinery methods that eliminate mechanical fasteners are employed to eliminate the risks of thermal bridging. In conventional insulation materials, when sections are joined metallic pins / rivets / bolts that penetrate through the material create thermal “shorts” or “bridges” that decrease the overall thermal efficiency of the assembly. By bonding sandwich panels together using the disclosed shiplap, tongue-in-groove, or other adhesive methods (see, e.g., Figures 4-5, etc.), high thermal conductivity materials like metallic alloys are avoided, and thermal bridging is mitigated. Additionally, the structural nature of the panels can be used to form multi-layer thermal protection systems by incorporating conventional high insulation value materials as cores (see, e.g., Figures 15-17). In these embodiments, the structural panels act as the load- bearing skin for a thicker composite panel with a traditional aerogel or fumed silica VIP acting as the fragile core material. This allows for the benefits of composite joinery (shiplap, tongue-in-groove, etc) while also providing enhanced stiffness to weight ratio and a massive increase in R value per inch. Various embodiments of the present invention are described herein with reference to the related drawings. Alternative embodiments can be devised without departing from the scope of this invention. It is noted that various connections and positional relationships (e.g., over, below, adjacent, etc.) are set forth between elements in the following description and in the drawings. These connections and / or positional relationships, unless specified otherwise, can be direct or indirect, and the present invention is not intended to be limiting in this respect. Accordingly, a coupling of entities can refer to either a direct or an indirect coupling, and a positional relationship between entities can be a direct or indirect positional relationship. The term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms "at least one" and "one or more" are understood to include any integer number greater than or equal to one, i.e. one, two, three, four, etc. The terms "a plurality" are understood to include any integer number greater than or equal to two, i.e. two, three, four, five, etc. Terms such as "connected to", “affixed to”, etc., can include both an indirect "connection" and a direct "connection." The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

CLAIMS:

1. A vacuum insulated panel, comprising: an internal core having a plurality of bonding structures at a front side of the core and a corresponding plurality of bonding structures at an opposing rear side, where each bonding structure on the front side of the core is connected to an adjacent bonding structure on the rear of the core by an angled polygonal surface; a structural skin disposed on the opposing front and rear sides of the core and bonded with the core at an exterior of the bonding structures; and a plurality of channels, each channel delimited by the respective skin, an interior of the bonding structure, and the angled polygonal surfaces; wherein the channels comprise a vacuum condition; and wherein the channels are vacuously isolated from one another.

2. The vacuum insulated panel of claim 1, wherein the structural skin is composed of a high strength steel of 80ksi to 110ksi and having and a thin gauge of 0.013” to 0.016”, where the steel is treated in a manner consistent with industry standards.

3. The vacuum insulated panel according to any one of the preceding claims, wherein the internal core is composed of plastic having open cellular structures of an appropriate size to minimize thermal conductivity and convection, wherein the core material is composed of a plastic with low outgassing characteristics.

4. The vacuum insulated panel according to any one of the preceding claims, wherein the vacuum condition is formed by one or more of the following: silicone or epoxy edge sealant; an Industrial metallized polyester impermeable envelope; and vacuum pumping connectors and quick-release for pumping and back-filling.

5. The vacuum insulated panel of according to any one of the preceding claims, wherein the high strength steel comprises ASME A653 galvannealed or hot dip galvanized steel.

6. The vacuum insulated panel of according to any one of the preceding claims, wherein the high strength steel includes appropriate backer or primer coatings, paint, and / or other surface treatments.

7. The vacuum insulated panel according to any one of the preceding claims, wherein the structural skin is composed of a fiber-reinforced thermoplastic composite.

8. The vacuum insulated panel according to any of the preceding claims, wherein the fiber- reinforced thermoplastic composite comprises continuous fibers, preferably at least one of glass, carbon, basalt, boron nitride, and jute, embedded in a unidirectional tape, and laid up in a multi-ply laminate with orientation optimized for predetermined structural goals.

9. The vacuum insulated panel according to any of the preceding claims, wherein the continuous fibers comprise at least one of glass, carbon, basalt, boron nitride, and jute.

10. The vacuum insulated panel according to any of the preceding claims, further comprising a tongue-in-groove, shiplap, and / or scarf geometry.

11. The vacuum insulated panel according to any of the preceding claims, wherein the panel is assembled having a two-part post created from an advanced thermoplastic composite to mitigate thermal bridging and maintain a high effective thermal resistance.

12. The vacuum insulated panel according to any of the preceding claims, wherein the panel is assembled with an adhesive.

13. A multi-layer thermal arrangement, comprising: a first vacuum insulated panel according to any of the preceding claims; a second vacuum insulated panel according to any of the preceding claims; and an insulating layer disposed between the first and second vacuum insulated panels.

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