Patent Publication Number: US-2023143092-A1

Title: Formed structural panel with open core

Description:
TECHNICAL FIELD 
     The present disclosure relates to the field of transportation, and, more particularly, to structural panels. The structural panels may be used as insulated structural panels for insulated cargo containers or insulated walls for structures. 
     BACKGROUND 
     Air cargo is typically transported in a container generally referred to as Unit Load Device (“ULD”), which is stowed in a cargo hold of an aircraft, which can either be below and/or above the deck, e.g., below the deck in a passenger aircraft or below and above the deck in transport aircraft. The outer size and shape of ULDs vary depending upon the type of aircraft such that the outer dimensions of the ULDs are determined by the type of aircraft. Typically, and regardless of the shape or geometry of the container, one end or side of the ULD is open for loading and unloading cargo. Various door closures can be used for opening and closing the open ends ULDs. The unloaded weight of the ULD is significant as even a slight reduction in the unloaded weight of the ULD will result in substantial savings in the cost of fuel to transport the ULD over its life. In addition, a reduction in the unloaded weight of the ULD will allow for an increased weight capacity for cargo. 
     Transporting perishable air cargo may require a ULD to be insulated and/or refrigerated. Some perishable air cargo may require an interior of a ULD to be maintained below a specific temperature or within a specific temperature range. Typically to insulate a ULD, insulated panels including foam cores or foam cores with air pockets have been used to achieve a suitable R-value. The foam cores generally have an R-value of R-5 per inch and tend to be thick, e.g., at least 1 inch, to achieve a suitable R-value. The thickness of the panels may reduce cargo space within a ULD and/or increase an unloaded weight of the ULD. Generally, to refrigerate a ULD, specialized refrigeration equipment that is certified for use in aircraft is used and disposed within the ULD or secured to the ULD. The specialized refrigeration equipment can also include batteries that are certified for use in aircraft. The refrigeration equipment and batteries tend to be heavy and bulky increasing the weight of the ULD and reducing cargo space of a ULD. 
     Structural panels have also been used as a building material to form walls for fixed structures and buildings. It may be beneficial to insulate such structural panels to reduce thermal transfer into or out of the structure formed of the structural panels. For example, insulating structural panels may improve a thermal efficiency of a heating and cooling system of a building formed of the structural panels. 
     SUMMARY 
     The present disclosure is directed to a structural panel that is formed from a first board and a second board that are spaced apart from one another to define a cavity therebetween. Each of the first board and the second board include a core sandwiched between two skins. The first board and the second board are spaced apart by one or more edge caps that are configured to transfer forces between the first board and the second board such that the cavity is isolated from the forces being transferred between the first board and the second board. 
     In an embodiment of the present disclosure, a panel includes a first board, a second board, and an edge cap. The first board includes a first core that is sandwiched between and bonded to a first skin and a second skin. The second board includes a second core that is sandwiched between and bonded to a third skin and a fourth skin. The edge cap is positioned between and bonded to the first board and the second board such that a cavity is defined by the first board, the second board, and the edge cap. The cavity is configured to receive an insert with the cavity being isolated from forces transferred between he first board and the second board. 
     In embodiments, the edge cap is configured to transfer shear forces between the first board and the second board. The insert may be disposed within the cavity. The insert may be an insulative insert, a fire-resistant insert, or signal-blocking insert. The insert may be a vacuum insulated panel. The insert may be bonded to the first board or the second board. The insert may be encapsulated in a non-combustible fabric to contain the contents of the insert and prevent burn-through. 
     In some embodiments, portions of the first board, the second board, and the edge cap may be thermoformed into an edge profile. Portions of the first skin, the second skin, the third skin, and the fourth skin may be consolidated together to form the edge profile. The edge profile may include an arcuate section. The edge profile may include a flat edge section. 
     In certain embodiments, the first skin has a first thickness and the second skin has a second thickness that is different from the first thickness. The first skin may have a first composition and the second skin may have a second composition different from the first skin. 
     In another embodiment of the present disclosure, a cargo container includes a first panel and a second panel as disclosed and described herein. The first panel has a first edge portion and the second panel has a second edge portion. The second panel is joined to the first panel such that the first edge portion is adjacent the second edge portion. 
     In embodiments, the first edge portion is secured directly to the second edge portion. The cargo container may include a frame element that is disposed between the first edge portion and the second edge portion. The first edge portion and the second edge portion may each be secured directly to the frame element. 
     In another embodiment of the present disclosure, a panel includes a first board, a second board, and a cap. The first board includes a first core that has a first skin bonded on a first side of the first core and a second skin that is bonded on a second side of the first core that is opposite the first side. The second board includes a second core that has a third skin bonded to a first side of the second core and a fourth skin that is bonded on a second side of the second core that is opposite the first side of the second skin. The cap is positioned between and bonded to the first board and the second board such that a cavity is defined by the first board, the second board, and the cap. The cap is configured to transfer shear forces between the first board to the second board. 
     In embodiments, the panel includes an insert that is disposed within the cavity. The insert may be isolated from shear forces of the first board and the second board. The first board, the second board, and the edge cap may be thermoformed into an edge profile. 
     In another embodiment of the present disclosure, a method of manufacturing a panel includes positioning an end cap on a first board, positioning a second board on the end cap such that a cavity is defined by the end cap, and thermoforming a portion of the first board, the second board, and the end cap such that the first board, the second board, and the end cap are bonded together to form an edge profile of the panel. The first board includes a first skin, a second skin, and a first core that is disposed between and bonded to the first skin and the second skin. The second board has a third skin, a fourth skin, and a second core that is disposed between and bonded to the third skin and the fourth skin. 
     In embodiments, thermoforming the portion of the first board, the second board, and the end cap may include consolidating the first skin, the second skin, the third skin, and the fourth skin in the edge profile of the panel. 
     Further, to the extent consistent, any of the embodiments or aspects described herein may be used in conjunction with any or all of the other embodiments or aspects described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of the present disclosure are described hereinbelow with reference to the drawings, which are incorporated in and constitute a part of this specification, wherein: 
         FIG.  1    is a cut-away, perspective view of a structural board provided in accordance with an embodiment of the present disclosure; 
         FIG.  2    is a cut-away, perspective view of a structural panel provided in accordance with an embodiment of the present disclosure; 
         FIG.  3    is a cut-away, perspective view of a first edge profile of the structural panel of  FIG.  2   ; 
         FIG.  4    is a cut-away, perspective view of two structural panels of  FIG.  3    secured directly to one another without a frame; 
         FIG.  5    is a cut-away, perspective view of a second edge profile of the structural panel of  FIG.  2   ; 
         FIG.  6    is a cut-away, perspective view of two structural panels of  FIG.  5    secured to one another with a frame element; 
         FIG.  7    is a flow chart of a method of manufacturing a structural panel in accordance with an embodiment of the present disclosure; and 
         FIG.  8    is a flow chart of a method of assembling a structure provided in accordance with an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure will now be described more fully hereinafter with reference to example embodiments thereof with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. These example embodiments are described so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Features from one embodiment or aspect can be combined with features from any other embodiment or aspect in any appropriate combination. For example, any individual or collective features of method aspects or embodiments can be applied to apparatus, product, or component aspects or embodiments and vice versa. The disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. As used in the specification and the appended claims, the singular forms “a,” “an,” “the,” and the like include plural referents unless the context clearly dictates otherwise. In addition, while reference may be made herein to quantitative measures, values, geometric relationships or the like, unless otherwise stated, any one or more if not all of these may be absolute or approximate to account for acceptable variations that may occur, such as those due to manufacturing or engineering tolerances or the like. 
     As used in the description and the appended claims, the phrases “unit load device” (ULD) or “air cargo container,” is defined as containers used to load luggage, freight, mail, and the like on aircraft including wide-body aircraft and narrow-body aircraft. While the containers described herein are directed to ULDs for use with aircraft, it is contemplated that cargo containers including the disclosed vacuum insulated panels may be used in other transportation vehicles such as trucks, trailers, ships, or trains such that the described use with aircraft should not be seen as limiting. In addition, while the panels described herein are described with respect to forming air cargo containers, it is contemplated that the panels described herein may be used with other transportation vehicles or as structural panels for construction such as interior or exterior walls, refrigerator panels, etc. As used herein, the term “vacuum” refers to a pressure of 3×10 3  Pa or less. 
     The temperature of cargo within a ULD designed with thermal insulation properties in mind may extend how long cargo is able to maintain a desired internal temperature. The desired internal temperature may be above or below an ambient temperature. Specifically, while an aircraft idles on the ground waiting to take off, during flight, and during unloading of the aircraft. In addition, a thermally insulated ULD may maintain an internal temperature range with a decreased amount of passive temperature control material, e.g., dry ice, or a decreased size of active cooling/heating equipment, e.g., refrigeration/heating equipment. 
     Referring now to  FIG.  1   , a structural board is provided in accordance with an embodiment of the present disclosure which is referred to generally as board  20 . The board  20  may be a thermoplastic panel that can be formed into different shapes under heat and pressure. The board  20  is a composite panel including a top or first skin  22 , a core  24 , and a bottom or second skin  26  that are bonded together to form a sandwich panel. The first skin  22  and the bottom skin  26  may be fiber-reinforced thermoplastic resin. The fibers of the first skin  22  and/or the bottom skin  26  may include thermoplastic fibers such as fiberglass fibers, carbon fibers, aramid fibers, ceramic fibers, other fibers typically used in composite construction, or combinations thereof. The resin of the first skin  22  and/or the bottom skin  26  may be a thermoplastic resin such as polypropylene, polyester, nylon, polyetherimide (PEI), polyether ether ketone (PEEK), or other thermoplastic resin used in the composites industry. 
     The skins  22 ,  26  may be the same or may be different. For example, the first skin  22  may have a thickness greater or lesser than the second skin  26 . Additionally or alternatively, the fibers and/or the resin of the first skin  22  and the second skin  26  may be the same or different from one another. The first skin  22  and the second skin  26  may differ based on the ultimate position of the skin  22 ,  26  in a final panel assembly as detailed below. For example, the first skin  22  may be configured to be exposed to external elements and the second skin  26  may be configured to be an internal layer protected from external elements as detailed below. In some embodiments, the first skin  22  or the second skin  26  may include fiberglass fibers and a polypropylene resin of which the fiberglass fibers may account for 64% of the weight of the particular skin  22 ,  26 . 
     In certain embodiments, the first skin  22  and the second skin  26  may comprise fiberglass fibers, aramid fibers including Kevlar fibers, ultra-high molecular weight polyethylene (UHMWPE) fibers, carbon fibers, polypropylene fibers, or a wide variety of medium to high modulus fibers. The fibers forming the first skin  22  or the second skin  26  may be woven into a cloth or laid up as unidirectional plies. The first skin  22  or the second skin  26  may have a thickness in a range of 0.05 mm to 3 mm, e.g., in a range of 0.5 mm to 1 mm. In certain embodiments, the first skin  22  or the second skin  26  may have thickness greater than 3 mm. The thickness of the first skin  22  or the second skin  26  may be optimized based on structural strength, impact resistance, weight, and cost. 
     For example, a fiberglass/polypropylene skin having a thickness of 0.4 mm has been tested and shown to handle required structural loading for a ULD panel when properly designed and manufactured. A skin having a thickness of 0.4 mm may provide a superior weight and cost. During use, ULD panels and skins forming ULD panels may be impacted by forklift tines. Managing this impact and avoiding damage requiring repair is a key requirement of panels for ULDs. A skin having a thickness of 0.4 mm may performs better than aluminum which is commonly used in this application. Since one of the goals of this type of product construction is to minimize operating costs and downtime, a calculation can be made to optimize impact resistance with weight and cost (assuming that structural requirements are met). The thickness of impact facing skins may be increased to absorb higher impacts without visual damage. 
     As noted above, the board  20  may be thermoformed and pressure formed into different shapes. During the forming process, fibers of the skins  22 ,  26  may wrinkle instead of stretching. This wrinkling may reduce the compressive strength of the respective skin  22 ,  26  and thus, the board  20  as a whole. As such, the geometry of the fibers of the skins  22 ,  26  may be designed to account for a subsequent forming process as detailed below. The orientation or geometry of the fibers of the skins  22 ,  26  may depend on a location within the skin  22 ,  26 . For example, the fibers of adjacent edges may have orientations that are perpendicular to one another with opposite edges having similar orientations. 
     The core  24  provides compressive strength and may increase durability of the board  20 . The core  24  is designed to have a shear strength and compressive strength that is sufficient to transfer loads between the first skin  22  and the second skin  26 . The core  24  may be a foam core, honeycomb core, or a foam-filled thermoplastic honeycomb core. A honeycomb core may provide increased shear strength or compressive strength compared to a foam core, a honeycomb core may have a lower insulation value relative to a foam core. A foam-filled honeycomb core may provide the strength of a honeycomb core with an insulation value approaching that of a fully foam core. In some embodiments, the core  24  includes a closed-cell foam. In embodiments where the core  24  includes a foam, the density of the foam may be selected to balance the structural strength of a dense foam with the insulative value of a less dense foam. The foam used to form a foam core may balance the strength requirements of the core  24  with the weight of the core  24 . This balance is important in applications where weight of the overall panel  10  is important such as when the panel is used to form a ULD or to form other panels for use in aircraft or shipping. While a denser foam may provide greater structural strength, denser foams may have a lower insulation value. In particular embodiments, the core  24  includes a closed-cell polypropylene foam that has a density of 64 kg/m 3 . 
     In embodiments, the thickness of the core  24  may vary from 6 mm to 75 mm. In some embodiments, the core  24  may have a thickness less than 6 mm or a thickness greater than 75 mm. The thickness of the core  24  may be increased to provide an improved insulation value. The thickness of the core  24  may be decreased to improve transfer of shear loading between the skins  22 ,  26  such that a thin core  24  may create a stiff and strong composite sandwich panel. As the thickness of the core  24  increases, the shear modulus of the core  24  may be increased to effectively transfer shear forces between the skins  22 ,  26 . To increase a shear modulus of the core  24 , a density of the core  24  may be increased. Increasing the density of the core  24  may reduce the insulation value of the core  24  and increase the weight of the core  24 . A decrease in the insulation value of the core or an increase in weight of the core are undesirable. A method of optimizing a thickness of the core  24  is discussed below in greater detail. 
     The first skin  22  and the second skin  26  are bonded to the core  24  such that shear loads are transferred between the skins  22 ,  26  through the core  24 . The core  24  may be sandwiched between the first skin  22  and the second skin  26  under pressure and/or heat to form the board  20 . The bond between the skins  22 ,  26  prevents delamination which would result in a significant reduction in stiffness of the board  20 . In embodiments where the core  24  includes a foam, the foam of the core  24  may be compatible with the resin of the first skin  22  or the second skin  26  such that a bond between the skins  22 ,  26  have sufficient strength. 
     With reference to  FIG.  2   , a structural panel is provided in accordance with embodiments of the present disclosure and is referred to generally as panel  100 . The panel  100  includes a first board  120 , a second board  220 , and a central core  150  positioned between the first board  120  and the second board  220 . The first board  120  and the second board  220  are each a structural board with a first skin  122 ,  222 ; a second skin  126 ,  226 ; and a core  124 ,  224  as detailed above with respect to board  20 . 
     The central core  150  includes end portions or caps  160  that extend along the external edges of the central core  150  and are bonded to opposing skins  126 ,  222  of the first board  120  and the second board  220 . The caps  160  are formed of a thermoplastic foam. The thermoplastic foam of the caps  160  may be compatible with the resin of the internal skins  126 ,  222  of the first board  120  and the second board  220  such that the caps  160  are structurally bonded to the first board  120  and the second board  220 . In addition, the thermoplastic foam of the caps  160  may have one or more properties similar to foam of the cores  124 ,  224  of the first board  120  and the second board  220 . For example, the foam of the caps  160  may have a melt rate similar to the cores  124 ,  224 . 
     The central core  150  includes a cavity  170  defined by the second or internal skin  126  of the first board  120 , the first or internal skin  222  of the second board  220 , and each of the caps  160 . The caps  160  are bonded to the first board  120  and the second board  220  such that shear forces and compressive forces are transferred between the first board  120  and the second board  220  through the caps  160 . The caps  160  may allow for all of the shear forces and the compressive forces to be transferred between the first board  120  and the second board  220  with the cavity  170  being isolated from experiencing shear forces and compressive forces experienced by the first board  120  or the second board  220 . The construction of the first board  120  and the second board  220  provide structural strength of the panel  100 . In addition, the stiffness of the first board  120  and the second board  220  prevent bowing or “oil-canning” of the individual boards  120 ,  220 . For example, the internal and externals skins of the first board  120  and the second board  220  may provide additional strength that prevent bowing as opposed to boards having only a single skin on either the interior or exterior of the board. 
     The panel  100  may include an insulative insert  180  disposed within the cavity  170 . An insulative insert might be formed of a less dense foam than the caps  160  such that the insert  180  has a greater insulative value than the caps  160 . In some embodiments, the insert  180  may be a vacuum insulated panel (VIP). An exemplary VIP panel  280  may include a filler material  282  and a barrier or envelope  284 . The filler material  282  may be a porous fabric or a porous foam material. The envelope  284  is disposed over the filler material  282  such that the filler material  282  is hermetically sealed within the interior of the VIP  280 . The envelope  284  may be a thin metallic layer, e.g., an aluminum layer, that is impenetrable. During manufacturing of the VIP  280 , a vacuum is applied such that when the envelope  284  is sealed over the filler material  282 , the envelope  284  holds a vacuum therewithin. The filler material  282  prevents the envelope  284  from collapsing and maintains a volume within the envelope  284 . The VIP  280  may have an R-value above R-15 per inch of thickness, e.g., R-20, R-30, R-40, R-45, or R-50 per inch of thickness. By isolating the VIP  280  within the cavity  170 , the VIP  280  is protected by the first board  120  and the second board  220  to prevent the seal of the envelope  284  from being compromised and thus, prevent the VIP  280  from losing its vacuum. In some embodiments, the VIP  280  may include a vacuum port  286  that allows a vacuum to be drawn in the VIP  280 . In certain embodiments, the VIP  280  includes a vacuum indicator  288  that provides an indication of a vacuum within the VIP  280 . In particular embodiments, the vacuum port  286  and/or the vacuum indicator  288  may be accessible through the first board  120  or the second board  220 . Examples of VIPs including VIPs with vacuum ports and vacuum indicators are disclosed in U.S. Patent Publication No. 2020/0407149, the entire contents of which are hereby incorporated by reference. 
     In certain embodiments, the envelope  284  may be formed of a non-combustible material or fabric. Such a non-combustible material may improve fire containment of the panel including a VIP  280 . The non-combustible material may be a quartz fabric or other high-temperature fabric. The non-combustible material may be a fabric covering or encapsulating the VIP  280  to provide an impenetrable fire barrier. In embodiments, the VIP  280  may be formed of fireproof silica or glass fiber. However, when exposed to fire, the VIP  280  may lose structural integrity. An envelope  284  surrounding the VIP  280  may contain the material of the VIP  280  when exposed to fire to prevent destruction of the VIP  280  which may otherwise be destroyed when exposed to fire. The envelope  284  may encapsulate the VIP  280  to contain the contents of the insert and prevent burn-through. In some embodiments, the envelope  284  may include an inner layer that maintains the vacuum of the VIP  280  and an outer layer which is formed of a non-combustible material or fabric. In certain embodiments, the envelope  284  includes a single layer that is both non-combustible and maintains the vacuum of the VIP  280 . In particular embodiments, the envelope  284  is integrated into the VIP  280  and in other embodiments the envelope  284  is formed separate from the VIP  280 . 
     Additionally or alternatively, the panel  100  may include other inserts disposed within the cavity  170 . For example, the panel  100  may include a fire-resistant insert or a signal-blocking insert. As the inserts within the cavity  170  are non-structural, a variety of different inserts may be disposed within the panel  100  to improve attributes of the panel or add functionality of the panel  100 . In certain embodiments, the insert for the cavity  170  may be a solid insert made from insulating materials such as phenolic, fiberglass, or similar materials with high compressive strengths. In some embodiments, the inserts may include attachment points as necessary. In particular embodiments, it may be possible to form a VIP panel with a hole so that this type of insert can be used as an attachment point. In certain embodiments, attachment inserts may be within the cores  124 ,  224 . In embodiments, the insert may not have the structural ability to support compressive loading or transmit shear loading between the boards. The construction detailed herein with respect to first board and a second board forming the cavity  170  may allow for less structural materials to be used in the cavity  170  as an insert. 
     Continuing to refer to  FIG.  2   , a method of optimizing skin thickness is disclosed in accordance with the present disclosure. The method may include determining a thickness of an outside facing skin  226  to be the thickest to resist impact from forklift tines, e.g., high speed impact from forklift tines. The thickness of an inside facing skin, e.g., skin  122 , may be thinner than the thickness of the outside facing skin  226  as the inside facing skin  122  may be impacted by cargo pallets and low-speed forklift tines in contrast to high speed forklift tines. The interior skins  126  and  222  may have a thickness less than the skins  122  and  226  as the skins  126  and  222  are disposed in the interior of the panel and thus, will experience the lowest impact. The interior skins  126 ,  222  may provide a tension layer across the cores  124  and  224  to make a structurally stiff sandwich composite panel. The thickness of the skins  122 ,  126 ,  222 ,  226  may be selected to have enough stiffness relative to the shear strength of the foam to resist buckling during bending. For example, the outside facing skin  226  may have a thickness of 1.5 mm, the inside facing skin  122  may have a thickness of 0.7 mm, and the two interior skins  126 ,  222  may each have a thickness of 0.4 mm. In some applications, this construction may simultaneously address structural, impact, weight, and cost considerations. 
     In some embodiments, the method may include optimizing the thickness of the cores  124 ,  224  based on structural and impact scenarios of the panel  100 . In some embodiments, the filler material  282  and the caps  160  may be optimized for weight, cost, and insulation value. The panel  100  may be configured such that most of the structural loading of the panel is carried by the two outer boards  120 ,  220  such that the filler material  282  and the caps  160  may be configured to increase an insulation value of the panel  100  and/or to provide sufficient compressive strength to avoid deformation or buckling of the boards  120 ,  220 . The filler material  282  may be a Vacuum Insulated Panels to provide a high insulation to weight/thickness ratio and the caps  160  may be an expanded or extruded polypropylene foam to provide a durable and formable with a lower but still effective insulation value. 
     With additional reference to  FIG.  3   , the panel  100  may include one or more formed edges with an exemplary formed edge portion  110  being shown. The first board  120 , the second board  220 , and the caps  160  are formed of thermoplastic materials which allows for thermoplastic forming of the edge portion  110  of the panel  100 . As shown, the formed edge portion  110  is formed by thermoforming portions of the first board  120 , the second board  220 , and the cap  160  along an edge of the panel  100  under heat and pressure. The formed edge portion  110  is compressed to have an angled section  112  and a profiled section  116 . In the angled section  112 , the first board  120 , the second board  220 , and the cap  160  are compressed towards the external or second skin  226  of the second board  220  such that a thickness of the panel  100  substantially linearly decreases as the panel  100  extends towards the edge of the panel  100 . The profiled section  116  extends from the angled section  112  to form a terminal edge  118  of the panel  100 . The profiled section  116  may have substantially constant thickness and form a variety of shapes. As shown, the profiled section  116  has an arcuate profile. Thermoforming the edge portions  110  of the panel  100  may increase or form the bond between the first board  120 , the second board  220 , and the caps  160 . For example, skins of the boards  120 ,  220  may consolidate during the forming of the profiled section  116 . The edge portion  110  may create a shear layer between the first board  120  and the second board  220  such that the boards  120 ,  220  act in concert with one another and have a high stiffness. This high stiffness may be enhanced at or adjacent the edge portions  110 . 
     With additional reference to  FIG.  4   , the edge portions  110  of adjacent panels  100  may be configured to fit together. The edge portions  110  of adjacent panels  100  may overlap one another such that a fastener may be passed through the edge portions  110  and in particular, the profiled sections  116  of the edge portions  110  to secure the edge portions  110  together. The fasteners may be selected from, but not be limited to, rivets, lockbolts, or threaded fasteners. As shown, the edge portions  110  are joined together at a 90-degree angle. However, the angle between the panels  100  may be any angle as long as the edge portions  110  are compatible with one another. As such, while the edge portions  110  shown in  FIG.  4    are the same, it is contemplated that edge portions  110  having differing shapes may be compatible with one another and joined together in a similar manner to form a corner with or without a frame. 
     As shown in  FIG.  4   , the panels  100  may be joined together without the use of a frame. Allowing the panels  100  to be joined together without a frame may increase a life of a container as rigid frame members may be prone to damage. The shape and the materials of the edge portions may provide a durable and resilient corner that is capable of withstanding impacts in common usage of cargo containers including ULDs. In some embodiments, the profiled sections  116  may be disposed about a frame. 
     Referring now to  FIGS.  5  and  6   , a panel  100 ′ is shown having a flat formed edge portion  110 ′. The panel  100 ′ is similar to the panel  100  and as such only the differences will be detailed herein for brevity. The flat formed edge portion  110 ′ has an angled section  112 ′ and a profiled section  116 ′. The profiled section  116 ′ is substantially flat and extending from exterior skin  122  of the first board  120  such that the outer surface  117 ′ of the profiled section  116 ′ is substantially planer with an outer surface of the exterior skin  122 . 
     The profiled section  116 ′ may be shaped to secure to a frame member  310  as shown in  FIG.  6   . The frame member  310  may be a pultrusion, metallic, or non-metallic with a profile to complement and fill an area between the edge portions  110  of adjacent panels  100 ′. In some embodiments the frame member  310  is formed of a fiberglass protrusion. Such pultrusions may be made with 60-80% by weight glass fiber with a polyurethane, polyester resin, or vinyl ester resin. Such a pultrusion may have a lower heat transfer constant than other structural materials and thus, reduce heat transfer through the frame member  310 . Pultrusions may allow for resilience in both the panels and the frame to allow for deformation and recovery from impacts. In certain embodiments, the frame member  310  may be an extruded aluminum or other conductive material. The frame member  310  may have a rigid corner element  316 ′ that is configured to be exposed to form a corner of a container or structure. The frame member  310  may be hollow and filled with an insulative material  318  such as a foam or an aerogel. The profiled sections  116 ′ of the panels  100 ′ are secured directly to the frame member  310  such that the panels  100 ′ are secured together. The profiled sections  116 ′ may be adhered, bonded, or fastened to the frame member  310 . For example, a fastener may pass through the profiled sections  116 ′ and into the frame member  310 . The fasteners may be blind rivets that pass through the profiled sections  116 ′ and into the frame member  310 . 
     Referring now to  FIG.  7   , a method for manufacturing a panel is provided in accordance with embodiments of the present disclosure and is referred to generally as method  500  with reference to the boards  20  and the panels  100 ,  100 ′ of  FIGS.  1 - 6   . To manufacture a panel, such as panel  100 , a first structural board  120  having a first or external skin  122 , a core  124 , and a second or internal skin  126  is positioned with the external skin  122  facing downward (Step  530 ). One or more caps  160  are positioned on the internal skin  126  of the first structural board  120  at or adjacent edges of the first structural board  120  (Step  540 ). The one or more caps  160  may be individual pieces of foam which are arranged to form the cavity  170  therebetween. Alternatively, the caps  160  may be a single or unitary piece of foam with the cavity  170  cut therefrom. In particular embodiments, the method  500  includes positioning a monolithic piece of foam or multiple pieces of foam around the edges of the first structural board  120  and cutting a cavity  170  from the monolithic piece or multiple pieces of foam (Step  544 ). In some embodiments, positioning the caps  160  includes bonding the one or more caps  160  to the internal skin  126  with a bonding agent or an adhesive (Step  546 ). 
     With the one or more caps  160  positioned or bonded to the internal skin  126  of the first structural board  120 , an insert may be disposed within the cavity  170  (Step  550 ). The insert may be an insulative insert (e.g., insulative insert  180 , VIP panel  180 ), a fire-resistant insert, an attachment insert, a solid inset, or a signal-blocking insert. In some embodiments, the method  500  may include extending access tunnels through the first structural board  120  or the one or more of the caps  160  (Step  554 ). The access tunnels may provide access to one or more ports of an insert. For example, the access tunnels may provide access to a vacuum port of a VIP panel, an indicator of the insert, an antenna of an insert, or electronics of an insert. In certain embodiments, the insert may be bonded to the internal skin  126  of the first structural board  120  or the one or more of the caps  160  (Step  556 ). 
     With the insert disposed within the cavity  170 , a second structural board  220  having a first or external skin  222 , a core  224 , and a second or internal skin  226  is positioned with the internal skin  226  opposing the internal skin  126  of the first structural board  120  (Step  560 ). The second structural board  220  is positioned such that the external skin  222  is opposite the external skin  122  of the first structural board  120  with the insert disposed between the first structural board  120  and the second structural board  220 . The internal skin  226  may be bonded to the one or more caps  160  with a bonding agent or an adhesive (Step  562 ). In certain embodiments, the internal skin  226  may be bonded to the insert within the cavity  170  (Step  566 ). For example, an elastomeric layer or a structural adhesive may be used to bond the insert to the internal skins  126 ,  226 . Bonding the insert to one or more of the internal skins  126 ,  226  may reduce movement of the insert within the cavity  170 . Reducing movement of the insert within the cavity  170  may reduce abrasion between the insert and the surfaces defining the cavity  170 , e.g., the internal skins  126 ,  226  and the caps  160 . Bonding of the insert to the one or more of the internal skins may provide additional shear strength to the panel  100 . 
     When the first structural board  120  and the second structural board  220  are positioned relative to one another such that the one or more caps  160  and the insert are sandwiched between the first structural board  120  and the second structural board  220 , the edges of the first structural board  120  and the second structural board  220  are thermoformed to shape the edge portions  110  of the panel  100  and to bond the first structural board  120  to the second structural board  220  (Process  570 ). The edge portions  110  of the panel  100  may be thermoformed by heating a first die and a second die and pressing an edge of the first structural board  120  and the second structural board  220  together to form the edge portion  110  (Step  572 ). The first and second dies may be heated to a temperature and applied together such the first structural board  120 , the second structural board  220 , and a cap  160  sandwiched between the boards  120 ,  220  are melted and bonded together. During thermoforming, the skins of the panels  100  may slip relative to one another to form a new shape. As the new shape is formed, a new bond may be formed between the skins and the foam, e.g., the cores  124 ,  224  and the caps  160 . The density of the foam in the edge portions  110  may be increased during thermoforming. For example, a foam having a density of 2% to 20% solid polymer may be increased to a density of 80% to 100% during thermoforming. In an exemplary embodiment, a 13 mm foam core of 64 kg/m 3  foam was melted and compressed to a consolidated thickness of 0.93 mm. In another exemplary embodiment, a 63 mm thick panel was thermoformed to have a profiled section with a thickness of 5 mm. The compression and consolidation during thermoforming may increase a compressive strength of the edge portions and may allow for a high fastener pull-out resistance. 
     Once the edge portions  110  are formed, the dies may be allowed to cool or be actively chilled such that the edge portions  110  are consolidated or solidified before being released from the dies (Step  574 ). 
     As the edge portion  110  is formed, the first structural board  120 , the second structural board  220 , and the cap  160  sandwiched between the boards  120 ,  220  are bonded together. As detailed above, the materials forming the first structural board  120 , the second structural board  220 , and the cap  160  may be compatible with one another such that as the edge portion  110  is formed, the first structural board  120 , the second structural board  220 , and the cap  160  are melted and bonded together. In some embodiments, as the edge portions  110  are formed, the cavity  170  is sealed along the edge portion  110 . 
     With the edge portion  110  of the panel  100  formed, the panel  100  may be repositioned by rotating the panels or moving the dies such that another edge portion  110  of the panel  100  is positioned between the dies (Step  576 ). The panel  100  may be rotated or dies be moved such that an edge portion  110  opposite or adjacent the formed edge portion  110  is disposed between the dies. With the unformed edge portion  110  between the dies, the dies are heated and pressed together to form the edge portion  110  in a manner similar to that detailed above (Steps  572  &amp;  574 ). This rotating of the panel  100  or the moving of the dies and forming of the unformed edge portions  110  is repeated until all the edge portions  110  of the panel  100  are formed. In some embodiments, one or more of the edge portions  110  are left unformed. In some embodiments, all the edge portions  110  are formed into the same profile. In certain embodiments, adjacent edge portions  110  are formed having differing profiles from one another. In particular embodiments, opposite edge portions  110  are formed having differing profiles from one another. 
     In certain embodiments, the method  500  includes forming the first structural board  120  and the second structural board  220  (Process  510 ). Forming the first structural board  120  and the second structural board  220  includes sandwiching a core  24  between a first skin  22  and a second skin  26  (Step  512 ). The core  24  is bonded to the first skin  22  and the second skin  26  such that the first skin  22  and the second skin  26  are capable of transferring forces therebetween through the core  24  (Step  514 ). Bonding the first skin  22  or the second skin  26  to the core  24  may be performed under heat and/or pressure to form a structural bond therebetween. The first skin  22  and the second skin  26  may be identical in thickness, material, and composition to one another or the first skin  22  and the second skin  26  may differ in thickness, material, or composition from one another. Step  512  and step  514  may be utilized to form the first structural board  120  and/or to form the second structural board  220 . The first structural board  120  and the second structural board  220  may be identical to one another or may differ from one another. In embodiments, the skins  22 ,  26  of each structural board  120 ,  220  may be optimized for the position within the final panel  100 . For example, the external skin  122  of the first structural board  120  may have a thickness greater than the internal skin  126  thereof. In some embodiments, the external skin  122  of the first structural board  120  may have a thickness greater than the external skin  222  of the second structural board  220 . In certain embodiments, the internal skins  126 ,  226  have the same thickness while in other embodiments, the internal skins  126 ,  226  may have differing thicknesses. 
     With reference to  FIG.  8   , a method for joining a first panel  100  to second panel  100  in accordance with the present disclosure and is referred to generally as method  600 . Joining the panels  100  includes aligning or positioning the first panel  100  adjacent the second panel  100  such that an edge portion  110  of each panel  100  is adjacent one another (Step  610 ). Positioning the panels  100  may include the edge portions  110  of the panels  100  overlapping one another such that a fastener may be passed through the edge portions  110  of each panel  100  to secure the panels  100  to one another (Step  612 ). In certain embodiments, joining the panels  100  may include placing a connector between the edge portions  110  (Step  614 ) and securing the first panel  100  to the connector (Step  616 ) and securing the second panel  100  to the connector (Step  618 ) such that the panels are secured to one another. Step  610  may be repeated until a shipping container, a truck body, a ULD, or a structure is formed. 
     The panels detailed herein may be constructed with structural characteristics suitable for other applications including cargo containers for use on trucks, ships, or trains. Such cargo containers by be in the form of a trailer for a truck, a shipping container for a ship, or a train car. In addition, the panels detailed herein may be suitable for buildings requiring insulated walls. For example, the panels detailed herein may be suitable for exterior walls or as an insulating layer on the outer surface of a wall. In addition, the panels detailed herein may be used to construct refrigeration units such as those used in hospitality, restaurant, or laboratory environments. When an enclosure or container is formed of the panels detailed herein, the enclosure or container may maintain an elevated or a reduced temperature to an environment surrounding the enclosure or container with minimal transfer of energy through the panels. In addition, the panels detailed herein may be used to add functionality to structures without compromising the structure. 
     While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Any combination of the above embodiments is also envisioned and is within the scope of the appended claims. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope of the claims appended hereto.