Composite panels having an integrated fixing feature and their manufacturing processes

Abstract

A composite panel includes a core structure having a main body and an attachment portion integrally formed with the main body. The core structure further includes at least one face. The attachment portion defines a first portion of the attachment opening. The composite panel further includes a composite sheet that is bonded to the at least one face of the core structure. The composite sheet extends between the main body and the attachment portion. The composite sheet defines a second portion of the attachment opening.

Description

Title of the invention: Composite panels having an integrated fastening feature and methods of manufacturing the same Technical field

[0001] The present description relates to composite panels, and more particularly to composite panels having central structures with a plurality of hollow cells. STATE OF PRIOR ART

[0002] Modern machines such as airplanes, automobiles, boats, rockets, space vehicles, or industrial equipment may be subjected to extreme operating conditions, which include high temperatures, high pressures, and high speeds. Reinforced ceramic matrix composites (“CMCs”) comprising fibers dispersed in continuous ceramic matrices of the same or different composition are well suited for structural applications due to their toughness, thermal resistance, high temperature strength, and chemical stability. Such composites typically have a high strength-to-weight ratio and retain this attribute over a wide temperature range that exceeds that of metal alloys.This makes them attractive in applications where weight is a concern and where high-temperature structural attributes severely constrain the design of components and systems, such as in aerospace and spacecraft applications. Their high-temperature stability makes CMCs highly suitable in applications where components are in contact with high-temperature gas, such as in a gas turbine engine and in spacecraft reentry conditions in terrestrial and non-terrestrial environments. Brief description of the drawings

[0003] A complete and useful description of the present disclosure, including the best mode thereof, intended for a person of ordinary skill in the art, is set forth in the specification, which refers to the accompanying figures, in which:

[0004] [Fig.l] illustrates an exploded perspective view of an exemplary composite panel with a plurality of cells, the cells being hexagonal in shape, in accordance with embodiments of the present disclosure;

[0005] [Fig.2] illustrates a top-down view of another exemplary central structure of a composite panel in accordance with exemplary aspects of the present disclosure;

[0006] [Fig. 3] illustrates a cross-sectional view of another exemplary composite panel having a central structure that is hollow and includes an attachment portion in accordance with embodiments of the present disclosure;

[0007] [Fig.4] illustrates a cross-sectional view of another exemplary composite panel having a central structure that is hollow and includes an attachment portion in accordance with embodiments of the present disclosure;

[0008] [Fig. 5] illustrates a cross-sectional view of another exemplary composite panel having a core structure that is solid and includes an attachment portion in accordance with embodiments of the present disclosure;

[0009] [Fig. 6] illustrates a cross-sectional view of another exemplary composite panel having a central structure that is hollow and includes an attachment portion in accordance with embodiments of the present disclosure;

[0010] [Fig. 7] illustrates a cross-sectional view of another exemplary composite panel assembly having a first composite panel and a second composite panel in contact with each other such that their respective attachment apertures align, in accordance with embodiments of the present disclosure;

[0011] [Fig.8] is a perspective view of a core structure of an exemplary composite panel in accordance with embodiments of the present disclosure;

[0012] [Fig.9] is a plan view of the central structure shown in [Fig.8], in accordance with embodiments of the present disclosure;

[0013] [Fig. 10] is a perspective view of another exemplary core structure of a composite panel in accordance with embodiments of the present disclosure;

[0014] [Fig. 11] is a plan view of the central structure shown in [Fig. 10] in accordance with embodiments of the present disclosure;

[0015] [Fig. 12] is a perspective view of another exemplary core structure of a composite panel in accordance with embodiments of the present disclosure;

[0016] [Fig. 13] is a plan view of the core structure shown in [Fig. 12] in accordance with embodiments of the present disclosure; and

[0017] [Fig. 14] is a flowchart diagram of an exemplary method of manufacturing a composite panel in accordance with embodiments of the present disclosure. DETAILED DESCRIPTION

[0018] We will now refer in detail to certain embodiments of the description, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and alphabetical designations to refer to features of the drawings. In the drawings and the description, like or similar designations have been used to refer to like or similar parts of the invention.

[0019] The term "exemplary" is used herein to mean "serving as an example, case, or illustration." Any implementation given herein "as an example" should not necessarily be construed as preferred or advantageous over other implementations. In addition, unless specifically stated otherwise, all embodiments described herein should be considered illustrative.

[0020] For the purposes of the following description, the terms "upper", "lower", "right", "left", "vertical", "horizontal", "above", "below", "lateral", "longitudinal" and their derivatives refer to the embodiments as oriented in the figures of the drawings. However, it is understood that the embodiments may adopt various alternative variations, unless expressly indicated otherwise. It is also understood that the specific devices illustrated in the accompanying drawings and described in the following specification are only exemplary embodiments of the disclosure. Accordingly, the specific dimensions and other physical characteristics related to the embodiments described herein should not be considered limiting.

[0021] Approximation terms, such as "about," "approximately," "generally," and "substantially," need not be limited to the precise value specified. In at least some cases, the approximation language may refer to the accuracy of an instrument for measuring the value, or to the accuracy of the processes or machines for constructing or manufacturing the components and systems. In at least some cases, the approximation language may refer to the accuracy of an instrument for measuring the value, or to the accuracy of the processes or machines for constructing or manufacturing the components and systems. For example, the approximation language may refer to a value falling within 1, 2, 4, 5, 10, 15, or 20 percent for the individual values, the range(s) of values, and the endpoints defining the range(s) of values.When used in the context of an angle or direction, these terms are understood to mean within ten degrees greater or less than the angle or direction indicated. For example, the phrase "generally vertical" includes directions within ten degrees of the vertical in any direction, e.g., clockwise or counterclockwise.

[0022] In this document, the terms "first", "second" and "third" may be used interchangeably to distinguish one component from another and are not intended to designate the location or importance of individual components.

[0023] The singular forms “un”, “une”, “la” and “le” include plural references, unless the context clearly indicates otherwise.

[0024] The expression "at least one of" in the context of, e.g., "at least one of A, B and C" refers to only A, only B, only C, or any combination of A, B and C.

[0025] Herein and throughout the specification and claims, range limitations are combined and interchanged, such ranges are identified and include all subranges contained therein, unless the context or language indicates otherwise. For example, all ranges described herein include endpoints, and endpoints may be independently combined with each other.

[0026] The term "turbomachine" or "turbomachines" refers to a machine comprising one or more compressors, a heat generating section (e.g., a combustion section), and one or more turbines that together generate an output torque.

[0027] The term "gas turbine engine" refers to an engine in which all or part of the power source is a turbomachine. Examples of gas turbine engines include turbofans, turboprops, turbojets, turboshafts, etc., as well as hybrid-electric versions of one or more of these engines.

[0028] As used herein, the term "integral" used to describe a structure refers to the structure formed from a continuous material or group of materials without seams, joint connections, or the like. The integral structure described herein may be formed by additive manufacturing to have the described structure, or alternatively by a casting process, etc. The term "unitary," as used herein, indicates that the final component has a construction in which the integrated parts are inseparable and is different from a component comprising a plurality of separate component pieces that have been joined but remain distinct and the single component is not inseparable (i.e., the pieces can be separated again). Thus, unitary components may comprise generally substantially continuous pieces of material or may comprise a plurality of parts that are permanently bonded to one another.In any event, the different parts forming a unitary component are integrated with each other, so that the unitary component is a single piece whose parts are inseparable.

[0029] The chemical elements are explained in this description using their common chemical abbreviation, as generally found in the periodic table of elements. For example, hydrogen is represented by its common chemical abbreviation H; helium is represented by its common chemical abbreviation He; and so on.

[0030] As used herein, the term "ceramic matrix composite" or "CMC" refers to a category of materials that includes a reinforcing material (e.g., reinforcing fibers) surrounded by a ceramic matrix phase. In general, the reinforcing fibers provide the structural integrity of the ceramic matrix. Some examples of CMC matrix materials may include, but are not limited to, non-oxide silicon-based materials (e.g., silicon carbide, silicon nitride, or mixtures thereof), oxide ceramics (e.g., silicon oxycarbides, silicon oxynitrides, aluminum oxide (Al2O3), silicon dioxide (SiO2), aluminosilicates, or mixtures thereof), or mixtures thereof. Ceramic particles (e.g., oxides of Si, Al, Zr, Y, and combinations thereof) and inorganic fillers (e.g.,, pyrophyllite, wollastonite, mica, talc, kyanite and montmorillonite) can also be included in the CMC matrix.

[0031] Some examples of CMC reinforcing fibers may include, but are not limited to, non-oxidized silicon-based materials (e.g., silicon carbide, silicon nitride, or mixtures thereof), non-oxidized carbon-based materials (e.g., carbon, silicon carbide, zirconium carbide), oxidized ceramics (e.g., silicon oxycarbides, silicon oxynitrides, aluminum oxide (A12O3), silicon dioxide (SiO2), aluminosilicates such as mullite, or mixtures thereof), or mixtures thereof.

[0032] Generally, particular CMCs may be referred to by their fiber type / matrix type combination. For example, C / SiC for carbon fiber reinforced silicon carbide; SiC / SiC for silicon carbide fiber reinforced silicon carbide, SiC / SiN for silicon carbide fiber reinforced silicon nitride; SiC / SiC-SiN for silicon carbide / silicon nitride fiber reinforced silicon carbide matrix mixture, etc. In other examples, CMCs may include a matrix and reinforcing fibers comprising oxide-based materials such as aluminum oxide (Al2O3), silicon dioxide (SiO2), aluminosilicates, and mixtures thereof. Aluminosilicates may include crystalline materials such as mullite (3Al2O3-2SiO2), as well as glassy aluminosilicates.

[0033] In some embodiments, the reinforcing fibers may be bundled or coated prior to inclusion within the matrix. For example, bundles of the fibers may be in the form of a reinforced ribbon, such as a unidirectional reinforced ribbon. A plurality of ribbons may be assembled to form a preform component. The fiber bundles may be impregnated with a slurry composition before or after formation of the preform. The preform may then undergo a thermal treatment, such as curing or burning to obtain a substantial char residue in the preform, and a subsequent chemical treatment, such as melt filtration with silicon, to arrive at a component formed from a CMC material having a desired chemical composition.

[0034] Such materials, as well as certain monolithic ceramics (i.e., ceramic materials without reinforcing material), are particularly suitable for high-temperature applications. In addition, these ceramic materials are lightweight compared to superalloys, but can still provide strength and durability to the component made from them. Therefore, these materials are currently being considered for many gas turbine, spacecraft structure, and propulsion components used in high-temperature sections, such as airfoils (e.g.,, turbines and blades), combustion chambers, fairings and other similar components, nozzles, transition ducts, thermal protection systems, TPS, aerodynamic control surfaces and leading edges that would benefit from the lighter weight and ability to withstand higher temperatures that these materials can offer.

[0035] As used herein, the term "additive manufacturing" generally refers to a manufacturing technology in which components are manufactured layer by layer. An exemplary additive manufacturing machine may be designed to use any suitable additive manufacturing technology. The additive manufacturing machine may use an additive manufacturing technology that includes powder bed fusion (PBF) technology, such as direct metal laser melting (DMLM) technology, selective laser melting (SLM) technology, directed metal laser sintering (DMLS) technology, or selective laser sintering (SLS) technology. In an exemplary PBF technology, thin layers of powder material are sequentially applied to a build plane and then selectively melted or fused together, layer by layer, to form one or more three-dimensional objects.Additively manufactured objects are typically monolithic in nature and may have a variety of integrated subcomponents.

[0036] Suitable additive manufacturing technologies in addition or alternatively may include, for example, Binder Jet technology, Fused Deposition Modeling (FDM) technology, Direct Energy Deposition (DED) technology, Laser Engineered Net Shaping (LENS) technology, Laser Net Shape Manufacturing (LNSM) technology, Direct Metal Deposition (DMD) technology, Digital Light Processing (DLP) technology and other additive manufacturing technologies that use an energy beam or other energy source to solidify an additive manufacturing material such as a powder material. In fact, any suitable additive manufacturing modality may be used with the subject matter of the present disclosure.

[0037] Additive manufacturing technology can generally be described as the manufacturing of objects by building objects point by point, line by line, layer by layer, typically in a vertical direction. Other manufacturing methods are contemplated and are within the scope of this disclosure. For example, although this document refers to the addition of material to form successive layers, the presently described object can be practiced with any additive manufacturing technology or other manufacturing technology, including layer-adding processes, layer-subtracting processes, or hybrid processes.

[0038] The additive manufacturing processes described herein may be used to form components using any suitable material. For example, the material may be metal, ceramic, polymer, epoxy, photopolymer resin, plastic, or any other suitable material that may be a solid, powder, sheet, wire, or any other suitable form, or combinations thereof. In addition, or as an alternative, exemplary materials may include metals, ceramics, or binders, as well as combinations thereof. Exemplary ceramics may be ultrahigh temperature ceramics or precursors of ultrahigh temperature ceramics, such as polymer precursors.Each successive layer may be, for example, between about 10 qm and 200 qm, although the thickness may be determined based on any number of parameters and may be of any suitable size.

[0039] As used herein, the term "build plane" refers to a plane defined by a surface upon which an energy beam impinges to selectively irradiate and thereby consolidate a powder material during an additive manufacturing process. Generally, the surface of a powder bed defines the build plane. During irradiation of a respective layer of the powder bed, a previously irradiated portion of the respective layer may define a portion of the build plane. Before distributing the powder material through a build module, a build plate that supports the powder bed typically defines the build plane.

[0040] As used herein, the term "consolidate" or "consolidating" refers to the densification and solidification of the powder material as a result of irradiation of the powder material, including by way of melting, smelting, sintering, or the like.

[0041] Joining one CMC subcomponent, or preform, to another CMC or ceramic subcomponent to form a complete component structure is of particular interest in the field of CMCs. For example, joining one CMC subcomponent to another may occur when the shape complexity of a complete overall structure may be too complex to be established in a single part. Another instance where joining one CMC subcomponent to another may occur is where a large complete structure is difficult to establish in a single part, and multiple subcomponents, or preforms, are fabricated and joined to form the large complete structure. Manufacturing complex composite components may require complex tooling and may involve forming fibers over small radii, which poses challenges in terms of manufacturability.Current procedures for bonding CMC subcomponents include, but are not limited to, diffusion bonding, reaction forming, melt infiltration, soldering, adhesives, or the like. Separation or failure of the joint that is formed during the joining procedure, under the influence of applied loads, is of particular concern in those CMC component structures that are formed from conjoined subcomponents.

[0042] Thus, an improved joint and an improved method of joining a CMC sub-component, or preform, to another monolithic ceramic sub-component or CMC sub-component to form a complete structure. The resulting joint provides the structure with strength and robustness that enables it to resist the influence of applied loads.

[0043] The present disclosure relates generally to composite panels that are constructed from composite materials. A core of the composite panel may be solid or comprise a plurality of hollow cells. Although composite materials provide good toughness, high thermal insulation, high temperature resistance, and chemical stability, raw materials and processing techniques can become expensive. Current structures capable of withstanding extreme operating conditions may be bulky, expensive, or have a short lifespan. Accordingly, a lighter, stronger, and more cost-effective structure would be welcome in the field. The panels Composites can provide similar properties while reducing the weight of a component formed from this construction, compared to other materials (e.g., superalloys). However, the relatively thin walls of the core structure provide a limited bonding area for connecting the core structure to one or more face sheets.

[0044] The present disclosure provides composite panels having core structures with attachment portions that facilitate coupling of the composite panel to other components. The attachment portions may have increased thickness to provide additional structural integrity to the composite panel, advantageously preventing joint failure or separation of the core structure from the composite sheets. In particular, the core structures may be additively manufactured with the attachment portions, minimizing machining of the final composite panel and allowing for better integration of the attachment portion with the composite sheets.

[0045] Referring now to the drawings, in which like reference numerals indicate the same or similar elements in different embodiments throughout the figures, [Fig. 1] shows an exploded view of the composite panel 100 according to one or more embodiments described herein. The composite panel 100 generally includes a core structure 120 and a first composite sheet 110 adhered to a first side 141 (or top side) of the core structure 120. In some embodiments, such as that illustrated in [Fig. 1], the composite panel 100 may further include a second composite sheet 150 adhered to a second side 143 (or bottom side) of the core structure 120 and opposite the first side 141. The core structure 120 may include a main body 122 and an attachment portion 124 formed integrally with the main body.The attachment portion 124 may define a first portion 135 of a attachment opening 137. Additionally, the main body 122 may define at least one face 126, such as a first face 142 (or top face) and a second face 144 (or bottom face). The core structure 120 may also include a cross-sectional geometry 101 that is non-uniform in a height direction between the first face 142 of the first side 141 and the second face 144 of the second side 143. Such a configuration may allow the first face 142 of the core structure 120, the second side 143 of the core structure 120, or a combination thereof, to produce a superior bond with the first composite sheet 110, the second composite sheet 150, or a combination thereof when present, while also producing a lighter composite panel 100 compared to an all-solid composite material.

[0046] The first composite sheet 110, the second composite sheet 150, and the core structure 120 may comprise a combination of different materials to facilitate meeting the structural and mechanical requirements of the composite panel 100. The first composite sheet 110 and the second composite sheet 150 (as well as the composite sheets 202, 204, and 206 discussed below with reference to FIGS. 5-7) may comprise any composite material. By way of non-limiting example, the composite material may comprise a CMC that generally comprises a fibrous reinforcing material incorporated into the matrix material. The reinforcing material serves as the load-bearing constituent of the CMC, while the matrix of a composite material serves to bond the fibers together and act as a support through which externally applied stress is transmitted and distributed to the fibers.In general, CMCs are well suited for structural applications due to their toughness, thermal resistance, high temperature strength, and chemical stability. Such composites can have a high strength-to-weight ratio that makes them attractive in applications where weight is an issue, such as in aerospace applications. In addition, their high temperature stability makes CMCs very suitable in applications where components are in contact with high-temperature gas, such as within a gas turbine engine.

[0047] Exemplary CMC materials include silicon carbide (SiC), silicon, silica, carbon, or alumina matrix materials and combinations thereof. Ceramic fibers may be incorporated within the matrix, such as oxidation-stable reinforcing fibers comprising monofilaments such as sapphire and silicon carbide (e.g., SCS-6 from Textron), as well as rods and yarns comprising silicon carbide (e.g., NICALON® from Nippon Carbon, TYRANNO® from Ube Industries and SYLRAMIC® from Dow Corning), alumina silicates (e.g., Nextel 440 and 480 from 3M), and tows and chopped fibers (e.g., Nextel 440 and SAFFIL® from 3M), and optionally ceramic particles (e.g., oxides of Si, Al, Zr, Y and combinations thereof) and inorganic fillers (e.g., pyrophyllite, wollastonite, mica, talc, kyanite and montmorillonite).For example, in some embodiments, fiber bundles, which may include a coating of refractory ceramic material, are formed as a reinforced ribbon, such as a unidirectional reinforced ribbon. A plurality of the ribbons may be formed together (e.g., as plies) to form a preform component. The fiber bundles may be impregnated with a slurry composition prior to preform formation (e.g., prepreg plies) or after preform formation. The preform may then undergo a heat treatment, such as curing or . combustion to obtain a substantial carbon residue in the preform, and subsequent chemical treatment, such as fusion filtration with silicon, to arrive at a component formed from a CMC material having a desired chemical composition. In other embodiments, the CMC material may be formed, e.g., from a carbon fiber fabric rather than a ribbon.

[0048] In a non-limiting example, the core structure 120 may comprise a different material compared to the first composite sheet 110 or the second composite sheet 150, such as an unreinforced ceramic material (e.g., a ceramic material lacking ceramic fibers). Similarly, the core structures 190 and 230 explained below with reference to FIGS. 5-7 may be formed from a different material compared to that of the composite sheets 202, 204, 206. As a non-limiting example, the core structure 120 may be a material that is less dense than the material of the first composite sheet 110 or the second composite sheet 150.However, even though the material of the core structure 120 is different, it is compatible with the first composite sheet 110 and the second composite sheet 150 to produce sufficient bonding between the components, including under extreme operating conditions such as high temperatures. In exemplary embodiments, the core structure 120 may comprise silicon, silicon carbide, alumina, carbon, or aluminosilicates, or combinations thereof. However, in some embodiments, the core structure 120 may comprise the same material as the first composite sheet 110 or the second composite sheet 150.

[0049] As illustrated in [Fig.l], the central structure 120 comprises a plurality of hollow cells 130 defined by a plurality of lattice walls 132 extending from a first face 142 on a top side 141 to a second face 144 on a bottom side 143. In a non-limiting example, each of the plurality of hollow cells 130 that form the central structure 120 may extend in a direction parallel to another. In other embodiments, one or more of the plurality of hollow cells may converge in cross-sectional area between the first face 142 and the second face 144. Further, each first face 142 of each of the plurality of hollow cells 130 may be planar relative to one another, such that the top side 141 of the core structure 120 comprises a substantially flat plane comprising a plurality of first faces 142 of the plurality of hollow cells 130.Similarly, each second face 144 of each of the plurality of hollow cells 130 may be planar relative to one another, such that the underside 143 of the central structure 120 comprises a substantially flat plane comprising a plurality of second faces 144 of the plurality of hollow cells 130. In such embodiments. embodiment, the first faces 142 and the second faces 144 may be parallel to each other, so that the first composite sheet 110 bonded to the top side 141 of the base structure 120 will be parallel to the second composite sheet 150 bonded to the bottom side 143 of the central structure 120.

[0050] While the central structure 120 of [Fig. 1] is illustrated as having a plurality of hollow cells 130 that are parallel to one another, are the same length as one another, and include a top side 141 parallel to a bottom side 143, it should be appreciated that a variety of alternative or additional configurations may also be realized within the scope of the present disclosure. For example, the plurality of hollow cells 130 may include different lengths, may include different orientations, may provide top sides 141 and bottom sides 143 that are not non-planar or not parallel to one another, or any combination thereof.

[0051] As illustrated in [Fig.l], the plurality of lattice walls 132 of the plurality of hollow cells 130 defines the shape, and more specifically, the cross-sectional geometry 101, of each of the plurality of hollow cells 130. In other words, the plurality of lattice walls 132 creates a partially enclosed structure (i.e., enclosed by the plurality of lattice walls 132 on the side but potentially open on the ends at the first face 142 or the second face 144) to define a hollow interior 149 to form a cross-sectional geometry 101 for each of the plurality of cells. As used herein, the term cross-sectional geometry 101 refers to the open or enclosed space between the plurality of lattice walls 132 at any point along the length of any individual cell.For example, each cell 130 has a top cross-sectional geometry 101a at its first face 142 at the top side 141 of the core structure 120, and a bottom cross-sectional geometry 101b at its second face 144 at the bottom side 143 of the core structure 120. The plurality of lattice walls 132 may be joined to form the plurality of hollow cells 130 using a variety of different techniques. For example, by way of non-limiting example, the plurality of lattice walls 132 may be formed unitarily, monolithically, or unitarily and monolithically.

[0052] The cross-sectional geometry 101 may include a variety of different shapes within each of the plurality of hollow cells 130. For example, as shown in the embodiment of [Fig.l], the cross-sectional geometry 101 of each hollow cell 130 may be a hexagon. In other words, each hollow cell 130 of the plurality of hollow cells 130 may have a hexagonal shape. However, the plurality of hollow cells 130 may have cross-sectional geometries 101 that are different, e.g., where the cross-sectional geometry 101 is one of a hexagon, a circle, a square, or a triangle in non-limiting examples.

[0053] [Fig. 2] illustrates a top-down view of a core structure 120 of an exemplary composite panel 100' in accordance with embodiments of the present disclosure. As illustrated, the core structure 120 may include the main body 122 having an attachment portion 124 integrally positioned therein. The attachment portion 124 may extend from the main body 122 or form a portion of the main body 122. Additionally, the main body 122 may define at least one face 126, such as the first face 142 and second face 144 discussed above with reference to [Fig. 1]. It will be noted that the components of the composite panel 100' shown in [Fig.2] which are similar to those of the composite panel 100 of [Fig.l] will share a common reference numeral, and the description of these components will be common to both composite panels 100, 100'.

[0054] In exemplary embodiments, the attachment portion 124 may be integrally positioned within the main body 122. In other words, the attachment portion 124 and the main body 122 may be integrally formed as a single component. For example, the attachment portion 124 and the main body 122 may be manufactured together as a single body. In exemplary embodiments, this may be accomplished using an additive manufacturing system. Integrally forming the attachment portion 124 with the main body, e.g., by additive manufacturing, may advantageously improve the overall strength of the core structure 120. Additionally, existing problems regarding, for example, leakage, quality of joints between separate parts, and overall performance may be advantageously reduced.

[0055] In various embodiments, the main body 122 may include end walls 123, which may be spaced apart and generally parallel to one another. Additionally, the main body 122 may include side walls 125 extending between the end walls 123. The side walls 125 may be generally parallel to one another and perpendicular to the end walls 123. Further, the main body 122 may include a plurality of lattice walls 132 that at least partially define a plurality of hollow cells 130. The plurality of hollow cells 130 may each define a cross-sectional geometry (e.g., in the longitudinal-transverse plane), which may have the shape of a hexagon (either a full hexagon or a portion of a hexagon). However, the plurality of hollow cells 130 may have other shapes, such as triangular, circular, rectangular, or others.

[0056] In many embodiments, each of the lattice walls 132 of the plurality of lattice walls may extend from one of the attachment portion 124, one of the end walls 123, one of the side walls 125, or another of the lattice walls 132 of the plurality of lattice walls 132. Thus, in addition to the lattice walls 132, the attachment portion 124, the side walls 125, and the end walls 123 may collectively define one or more of the hollow cells 130. For example, as shown in [Fig. 2], one or more of the hollow cells 130 of the plurality of hollow cells 130 may be collectively defined by the attachment portion 124 and a set of lattice walls 132 of the plurality of lattice walls 132.Additionally, as shown, one or more hollow cells 130 of the plurality of hollow cells 130 may be collectively defined by one of the end walls 123 and one or more lattice walls 132 of the plurality of lattice walls 132. Further, one or more hollow cells 130 may be collectively defined by one of the side walls 125 and one or more lattice walls 132 of the plurality of lattice walls 132. Additionally, one or more hollow cells 130 may be collectively defined by the attachment portion 124 and one or more lattice walls 132 of the plurality of lattice walls 132.

[0057] In exemplary embodiments, the fastening portion 124 may define the first portion 135 of the fastening opening 137. The fastening opening 137 may be sized and oriented to receive a fastener (such as a bolt or other fastener). In many embodiments, as shown, the fastening opening 137 may have a circular cross-sectional shape; however, this is not necessarily the case. The fastening opening 137 may have other cross-sectional shapes, for example, a non-circular cross-sectional shape. For example, referring again to [Fig. 1], as shown, the fastening opening 137 may have a circular or non-circular shape. In embodiments where the fastening opening 137 has a non-circular shape, the fastening opening 137 may have an elliptical, geometrically shaped cross-sectional shape (e.g.,, a rectangle with semi-circular ends), or other cross-sectional shapes. The non-circular cross-sectional shape may be advantageous due to the non-uniform thermal expansion / contraction of the core structure 120 and the entire composite panel 100.

[0058] Referring again to [Fig. 2], the attachment portion 124 may have the same cross-sectional shape as the plurality of hollow cells 130 (e.g., hexagonal). In the illustrated exemplary embodiment, the attachment portion may define six corners, and a lattice wall 132 may extend from each of the six corners. In other embodiments (not shown), the attachment portion 124 may have a different cross-sectional shape than the plurality of hollow cells 130.

[0059] In many embodiments, each of the lattice walls 132 may define a first thickness 160. In particular, each of the lattice walls 132 may define a first surface 161 and a second surface 163 opposite the first surface 161, and the first thickness 160 may be defined between the first surface 161 and the second surface 163. Similarly, the attachment portion 124 may define a second thickness 162. The second thickness may be defined between the first portion 135 of the attachment opening 137 and an outer surface 180 of the attachment portion 124. The outer surface 180 may be defined by the attachment portion 124. As shown in [Fig. 2], the second thickness 162 may vary around the circumference of the first portion 135 of the attachment opening 137 (e.g., the thickness may increase near the corners of the fixing part 124 of hexagonal shape).The second thickness 162 may be greater than the first thickness 160. For example, the second thickness 162 may be about 5% to about 450% greater than the first thickness 160, or about 10% to about 300% greater than the first thickness 160, or about 20% to about 200% greater than the first thickness 160, or about 40% to about 100% greater than the first thickness 160. The additional thickness of the attachment portion 124 may advantageously provide additional structural support and strength that allows the attachment portion 124 to support a joint (such as a bolted joint, a welded joint, or the like).

[0060] [Fig. 3] illustrates a cross-sectional view of an exemplary composite panel 100" in accordance with one embodiment of the present disclosure. [Fig. 4] illustrates a cross-sectional view of a similar exemplary composite panel 100"' in accordance with one embodiment of the present disclosure. As shown collectively in FIGS. 2-4, each respective composite panel 100', 100", 100"' may define a Cartesian coordinate system having a vertical direction V, a longitudinal direction L, and a transverse direction T mutually perpendicular to each other. As shown, each composite panel 100', 100", 100"' may include the core structure 120 and a composite sheet 109. In particular, each composite panel 100', 100", 100"' may include a first composite sheet 110 and a second composite sheet 150.As explained above, the central structure 120 may include an attachment portion 124 and a main body 122 having a plurality of lattice walls 132. The central structure 120 may define at least one face 126, and the composite sheet 109 may be bonded to the at least one face 126 of the central structure 120. In particular, the at least one face 126 includes the first face 142 (or top face) and the second face 144 (or bottom face). The first composite sheet . 110 may be bonded to the first face 142, and the second composite sheet 150 may be bonded to the second face 144.

[0061] The composite sheet 109 may extend between the main body 122 and the attachment portion 124 of the central structure 120 (e.g., on the at least one face 126). As shown in FIGS. 3 and 4, the attachment opening 137 may be collectively defined by the central structure 120, the first composite sheet 110, and the second composite sheet 150. In other words, the attachment portion 124 of the central structure 120 may define the first portion 135 of the attachment opening 137. The first portion 135 of the attachment opening may extend vertically from the first face 142 to the second face 144. The first composite sheet may define a second portion 136 of the attachment opening 137, and the second composite sheet may define a third portion 139 of the attachment opening 137.

[0062] As shown in FIGS. 3 and 4, the first portion 135, the second portion 136, and the third portion 139 of the attachment opening 137 may align along a common axis 164. The common axis 164 may extend vertically. A center point of the first portion 135, the second portion 136, and the third portion 139 may be positioned along the common axis 164.

[0063] As explained above, the main body 122 may include a plurality of lattice walls 132 that at least partially define a plurality of hollow cells 130. As shown in FIGS. 3 and 4, each of the hollow cells 130 may be collectively formed by a lattice wall 132, the attachment portion 124, a first wall 166 (or top wall), and a second wall 168 (or bottom wall). In some embodiments (not shown), one or more of the hollow cells 130 may not include a first wall 166 and a second wall 168, such that the one or more hollow cells 130 may have an open end (e.g., be open at the first face 142 or the second face 144). The first wall 166 and the second wall 168 may be generally perpendicular to the lattice wall 132.For example, each lattice wall 132 may extend generally vertically from the second wall 168 to the first wall 166, and the top wall may extend longitudinally (and transversely) from one or more lattice walls 132 to the attachment portion 124.

[0064] Each hollow cell 130 of the plurality of hollow cells 130 may define a hollow interior 149. In other words, the hollow interior 149 may be collectively defined by the first wall 166, the second wall 168, the attachment portion 124, and one or more lattice walls 132 of the plurality of lattice walls 132.

[0065] [Fig. 4] illustrates that the first wall 166 or the second wall 168 may define an opening 138 or an open face or to facilitate removal of the powder feedstock from a potentially otherwise enclosed hollow interior. A opening may be provided on both sides. Furthermore, the openings need not necessarily be on alternate sides and may be on only one side of the main body.

[0066] As shown in [Fig. 4], the composite sheet 109 (e.g., the first composite sheet 110) may include a recess 170. In particular, the first composite sheet 110 may include a first surface 172 and a second surface 174. The recess 170 may extend from the first surface 172 to the second surface 174. In particular, the recess 170 may extend from the first surface 172 to the second portion 136 of the attachment opening 137, and the second portion 136 of the attachment opening 137 may extend from the recess to the second surface 174 of the first composite sheet 110. The recess 170 may define a first width (or a first diameter) and the attachment opening 137 may define a second width (or a second diameter, if it is circular in nature). The first width may be greater than the second.The recess 170 may be configured to receive and seat a portion of a fastener, such as a bolt head, by way of non-limiting example, such that the bolt head may be below or flush with the first surface 172 of the first composite sheet 110 when the fastener is inserted into the fastener opening 137.

[0067] In the embodiments shown in FIGS. 3 and 4, the attachment portion 124 and the attachment opening 137 may extend along a common axis 164 that is generally parallel to the vertical direction V and generally parallel to the lattice walls 132 (e.g., between the first face 142 and the second face 144). However, in other embodiments, as shown in FIGS. 5 and 6, an attachment opening 214 may extend along a common axis 164 that is not parallel to the vertical direction V or to the lattice walls 233.

[0068] [Fig. 5] illustrates a cross-sectional view of a composite panel 500, and [Fig. 6] illustrates a cross-sectional view of a composite panel 600 in accordance with embodiments of the present disclosure. In particular, [Fig. 5] illustrates a composite panel 500 having a core structure 190 with a main body 192 that is solid. As used herein, the term "solid" may refer to one or more components that are free of voids, internal cavities, holes, etc. The main body 192 may have a first face 196 (e.g., a top face), a second face 198 (e.g., a side face), and a third face 200 (e.g., a bottom face) opposite the first face 196.

[0069] An attachment portion 194 extends away from the main body 192. In exemplary embodiments, as shown in [Fig. 5], the attachment portion 194 may extend away from the main body 192 to a terminal end 208. In a non-limiting example, the attachment portion 194 may extend from the first face 196 of the main body 192 to the terminal end 208. The attachment portion 194 may extend vertically from a base 210 to a terminal end 208. In one example, the base 210 (illustrated by the dotted line) may be coupled to the first face 196 of the main body 192, and the terminal end 208 may be a free end (e.g., not coupled to another component). Alternatively, the attachment portion and the main body 192 may be formed unitarily, such that the base 210 is integral with the main body 192.

[0070] The attachment portion 194 may define a first surface 222, a second surface 224, and the terminal end 208 extending between the first surface 222 and the second surface 224. As shown in [Fig. 5], the first surface 222 may have a curved portion and a straight portion. The curved portion may extend from the first face 196 of the main body 192 to the straight portion, and the straight portion may extend from the curved portion to the terminal end 208. The attachment portion 194 may define a width between the first surface 222 and the second surface 224, and the attachment portion 194 may converge in width as the attachment portion extends away from the main body 192 to the terminal end 208.

[0071] The composite panel 500 may comprise a first composite sheet 202, a second composite sheet 204 and a third composite sheet 206. The first composite sheet 202 may be bonded to a first face 196 of the main body 192 and to the first surface 222 of the attachment portion 194. The second composite sheet 204 may be bonded to the second face 198 of the main body 192 and to the second surface 224 of the attachment portion 194. The third composite sheet 206 may be bonded to the third face 200 of the main body 192.

[0072] As shown in [Fig. 5], a fastening opening 214 may be disposed through a section of the fastening portion 194. Additionally, an unreinforced section of the fastening portion 194 has an increased local thickness to accommodate the curvature of the first composite sheet 202, thereby extending from the first composite sheet 202 to the second composite sheet 204 and the third composite sheet 206. In the illustrated example, the fastening portion 194 forms a flange having an opening therethrough. In particular, the fastening opening 214 may be collectively defined by the first composite sheet 202, the fastening portion 194 of the core structure 190, and the second composite sheet 204. For example, the fastening portion 194 may define a first portion 216 of the fastening opening 214.The first portion 216 of the attachment opening 214 may extend from the first surface 222 to the second surface 224 of the attachment portion 194. The first composite sheet 202 may define a second portion 218 of the attachment opening 214, and the second composite sheet 204 may define a third portion 220 of the attachment opening 214. The first portion 216, the second portion 218, and the third portion . 220 may align with one another to collectively form the fastening opening 214 which is adapted to receive a bolt or other fastening mechanisms.

[0073] As shown in [Fig. 6], the composite panel 600 may comprise a central structure 230 having a main body 232 which is hollow. In other words, the main body 232 may comprise a plurality of hollow cells 231, which may have the same or similar structure as the hollow cells 130 explained above with reference to FIGS. 1 to 4.

[0074] The main body 232 may include a plurality of lattice walls 233 that at least partially define a plurality of hollow cells 231. As shown, each of the hollow cells 231 may be collectively formed by a lattice wall 233, a top wall 266, and a bottom wall 268. At least one hollow cell 231 may be collectively formed by a lattice wall 233, a top wall 266, a bottom wall 268, and an end wall 270. In some embodiments (not shown), one or more of the hollow cells 130 may not include the top wall 266 or the bottom wall 268, such that the one or more hollow cells 231 may have an open end (e.g., be open at the first face 142 or the second face 144).The top wall 266 and the bottom wall 268 may be generally perpendicular to the lattice walls 233 and perpendicular to the end wall 270. For example, each lattice wall 233 may extend generally vertically from the bottom wall 268 to the top wall 266.

[0075] Each hollow cell 231 of the plurality of hollow cells 231 may define a hollow interior 249. In other words, the hollow interior 249 may be collectively defined by the top wall 266, the bottom wall 268, and one or more lattice walls 233 of the plurality of lattice walls 233. In some embodiments, the top wall 266 or the bottom wall 268 may define an opening or open face or facilitate removal of the powder feedstock from a potentially otherwise enclosed hollow interior.

[0076] The central structure 230 may further comprise an attachment portion 194 extending from the main body 232. The main body 232 may comprise a first face 296 (e.g., a top face), a second face 298, a third face 300 (e.g., a bottom face) opposite the first face 296. Of course, other faces may be present depending on the design of the central structure 230. The first face 296 may be at least partially defined by the top wall 266, and the third face 300 may be at least partially defined by the bottom wall 268. The main body 232 of the central structure 230 may further comprise a second face 298 (e.g., a side face) defined at least partially by the end wall 270. The end wall 270 may have a structure similar to that of the lattice walls 233 or be thicker than the lattice walls 233.

[0077] The attachment portion 194 may define a first surface 222, a second surface 224, and the terminal end 208 extending between the first surface 222 and the second surface 224. The first surface 222 may include a curved portion and a straight portion. The curved portion may extend from the first face 296 of the main body 232 to the straight portion, and the straight portion may extend from the curved portion to the terminal end 208. The attachment portion 194 may define a width between the first surface 222 and the second surface 224, and the attachment portion 194 may converge in width as the attachment portion extends away from the main body 232 to the terminal end 208.

[0078] The attachment portion 194 may extend from the main body 232 to a terminal end 208. In particular, the attachment portion 194 may extend from the first face 296 of the main body 232 to the terminal end 208. The attachment portion 194 may extend vertically from a base 210 to the terminal end 208. The base 210 may be coupled to the first face 296 of the main body 232, and the terminal end 208 may be a free end (e.g., not coupled to another component). The attachment portion 194 may extend from the main body 232 to the terminal end 208 at the end wall 270 of the main body 232, such that the second surface 224 of the attachment portion 194 extends from the second face 298 of the main body 232 to the central structure 230.

[0079] The composite panel 600 may comprise a first composite sheet 202, a second composite sheet 204 and a third composite sheet 206. The first composite sheet 202 may be bonded to the first face 296 of the main body 232 and to the first surface 222 of the attachment portion 194. The second composite sheet 204 may be bonded to the second face 298 of the main body 232 and to the second surface 224 of the attachment portion 194. The third composite sheet 206 may be bonded to the third face 300 of the main body 122.

[0080] In many embodiments, the attachment portion 194 may define an angle with the main body 232. For example, while [Fig. 6] illustrates the attachment portion 194 extending generally perpendicular to the main body 232, such that the angle between the main body 232 and the attachment portion 194 is about 90°. In other embodiments, the angle may be between about 0° and about 180°, or between about 20° and about 160°, or between about 40° and about 120°, or between about 60° and about 100°.

[0081] As shown in [Fig.6], a fastening opening 214 may be disposed between the main body 232 and the terminal end 208 of the fastening portion 194. In In particular, the fastening opening 214 may be collectively defined by the first composite sheet 202, the fastening portion 194 of the core structure 230, and the second composite sheet 204. For example, the fastening portion 194 may define a first portion 216 of the fastening opening 214. The first portion 216 of the fastening opening 214 may extend from the first surface 222 to the second surface 224 of the fastening portion 194. The first composite sheet 202 may define a second portion 218 of the fastening opening 214, and the second composite sheet 204 may define a third portion 220 of the fastening opening 214. The first portion 216, the second portion 218, and the third portion 220 may align with one another to collectively form the fastening opening 214, which is configured to receive a bolt. or other fastening mechanisms.

[0082] [Fig. 7] illustrates a cross-sectional view of a composite panel assembly 400 in accordance with embodiments of the present disclosure. As shown, the composite panel assembly 400 includes a first composite panel 100A and a second composite panel 100B in contact with each other to form a joint therebetween. The first composite panel 100A and the second composite panel 100B may each be designed similarly to the composite panel 100 explained above with reference to [Fig. 5].

[0083] The first composite panel 100A may include a first central structure 190A having a first main body 192A, a first attachment portion 194A, a first face 196A, and a first exposed face 402A. The first composite panel 100A may further include a first top composite sheet 202A adhered to the first face 196A of the first central structure 190A. Additionally, the first composite panel 100A may include a first bottom composite sheet 404A adhered to a first face 200A of the first central structure 190A. In exemplary embodiments, the first attachment portion 194A and the first top composite sheet 202A collectively define a first attachment opening 406A.

[0084] The second composite panel 100B may include a second core structure 190B having a second main body 192B, a second attachment portion 194B, a second face 196B, and a second exposed face 402B. The second composite panel 100B may further include a second top composite sheet 202B adhered to the second face 196B of the second core structure 190B. Additionally, the second composite panel 100B may include a second bottom composite sheet 404B adhered to a second face 200B of the second core structure 190B. In exemplary embodiments, the second attachment portion 194B and the second top composite sheet 202B collectively define a second attachment opening 406B.

[0085] As shown in [Fig. 7], in exemplary embodiments, the first exposed face 402A and the second exposed face 402B may not be coupled to a composite sheet. Instead, the first exposed face 402A and the second exposed face 402B may contact each other such that the first fastening opening 406A aligns with the second fastening opening 406B. In many embodiments, a fastener, such as a bolt, may be inserted through the first fastening opening 406A and the second fastening opening 406B to connect the first composite panel 100A to the second composite panel 100B.

[0086] In many embodiments, the first attachment portion 194A may extend away from the first main body 192A to a first terminal end 208A. In such embodiments, the first attachment opening 406A may be disposed between the first main body 192A and the first terminal end 208A of the first attachment portion 194A. Similarly, as shown, the second attachment portion 194B may extend away from the second main body 192B to a second terminal end 208B. In such embodiments, the second attachment opening 406B may be disposed between the second main body 192B and the second terminal end 208B of the second attachment portion 194B.

[0087] Referring now to FIGS. 8-13, various embodiments of core structures are illustrated in accordance with aspects of the present disclosure. Such core structures may be used in the composite panels described above with reference to FIGS. 1-7. As shown in FIGS. 8-13, the core structure 120', 120", 120"' may include a plurality of lattice walls 132 that define one or more hollow patterns and cavities. In some embodiments, such as those shown in [Fig. 8], the respective central structure 120', 120" may include a main body 102 that defines a first lattice pattern 152 with the plurality of lattice walls 132 and an attachment portion 104 that defines a second lattice pattern 154 with the plurality of lattice walls 132 that is different from the first lattice pattern 152. In other embodiments, such as those shown in [Fig.12], the central structure 120"' may include a main body 102 that defines a first lattice pattern 152 with the plurality of lattice walls 132 and an attachment portion 104 that defines a second lattice pattern 154 with the plurality of lattice walls 132 that is the same as the first lattice pattern 152 but with a greater lattice wall thickness.

[0088] The attachment portion 104 may have a material density that is greater than a material density of the main body 102. For example, the attachment portion 104 may have a material density that is about 10% to about 300% greater than a material density of the main body 102, or about 50% to about 250% greater than a material density of the main body 102, or about 50% to about 150% greater than a material density of the main body 102. The difference in material density between the main body 102 and the attachment portion 104 may be accomplished by varying the distance between the lattice walls 132 in the main body 102 and the attachment portion 104 (e.g., by altering the pattern of the lattice walls 132 for the main body 102 and the attachment portion 104) or by varying the thickness of the lattice walls 132 in the main body 102 and the attachment portion 104. Thus, more material may be present in the attachment portion 104 to provide greater strength therein, as compared to the main body 102.

[0089] With specific reference to the embodiment shown in FIGS. 8 and 9, the main body 102 of the central structure 120' may define a first lattice pattern 152 that is different from a second lattice pattern 154 of the attachment portion 104. In the first lattice pattern 152, the plurality of lattice walls 132 forms a plurality of hexagonal units 301. Each hexagonal unit 301 may be formed from six lattice walls 132. Each hexagonal unit 301 may share the lattice walls 132 with at least one other hexagonal unit 301. In particular, each hexagonal unit 301 may share a lattice wall 132 with up to six other hexagonal units 301 and with the attachment portion 104. Furthermore, each hexagonal unit 301 of the first lattice pattern 152 may be of equal size (such that each of the lattice walls 132 constituting a hexagonal unit 301 has an equal length).

[0090] The second lattice pattern 154 may include a plurality of overlapping hexagonal units 301, each hexagonal unit 301 of the second lattice pattern 154 may partially overlap with one or more hexagonal units 301, resulting in a denser pattern than the first lattice pattern 152, thereby providing greater material strength near the attachment opening 137 (thus enabling a mechanical bond). Further, the hexagonal units 301 of the second lattice pattern 154 may have various sizes (such as a first size, a second size smaller than the first size, a third size smaller than the first and second sizes, and so on), although this is not necessarily the case.

[0091] Referring specifically to the embodiment shown in FIGS. 10 and 11, the main body 102 of the central structure 120” may define a first lattice pattern 152 that is different from a second lattice pattern 154 of the attachment portion 104. In the first lattice pattern 152, the plurality of lattice walls 132 form a plurality of hexagonal units 301. Each hexagonal unit 301 may be formed from six lattice walls 132. Each hexagonal unit 301 may share the walls into lattice 132 with at least one other hexagonal unit 301. In particular, each hexagonal unit 301 may share a lattice wall 132 with up to six other hexagonal units 301 and with the attachment portion 104. Further, each hexagonal unit 301 of the first lattice pattern 152 may be of equal size (such that each of the lattice walls 132 constituting a hexagonal unit 301 has an equal length).

[0092] The second lattice pattern 154 may include a star-shaped outer perimeter 302. In particular, the star-shaped outer perimeter 302 may have six outer vertices 306 and six inner vertices 308. The star-shaped outer perimeter 302 may have tips 304 that at least partially overlap one or more hexagonal units 301 in the first lattice pattern 152. The tips 304 may define the outer vertices 306. The attachment opening 137 may be defined in the center of the second lattice pattern 154. One or more support walls 310 may extend between the attachment opening 137 and the inner vertices 308. The second lattice pattern 154 may have a density that is greater than a density of the first lattice pattern 152 (e.g., 10% greater, or 50% greater, or 100% greater, or 200% greater, or more than 300% greater).

[0093] Referring specifically to the embodiment shown in FIGS. 12 and 13, the main body 102 of the base structure"' may define a first lattice pattern 152 that is the same as a second lattice pattern 154 of the attachment portion 104. More specifically, the geometric shape of the lattice walls may be considered identical. Although the geometric shape of the lattice walls is the same, the wall thickness between the first lattice pattern 152 and the second lattice pattern 154 is not the same. In this way, the density of the attachment portion 104 may be greater than the density of the main body 102 by varying the thickness of the walls forming the hexagonal units 106.For example, the attachment portion 104 may have a material density (i.e., mass of material per volume) that is about 10% greater than the material density of the main body 102 (or 50% greater, or 100% greater, or 200% greater, or more than 300% greater). This difference in material density may be accomplished by varying the ratio of wall to hollow space within the volume (i.e., thicker walls lead to greater material density, just as smaller openings lead to greater material density). A fastening opening 137 may be defined in the center of the attachment portion 104 (e.g., through a central hexagonal unit 312).In particular, the attachment portion 104 may comprise the central hexagonal unit 312, a first group 314 of hexagonal units 301 surrounding the central hexagonal unit 312, and a second group 315 of hexagonal units 301 surrounding the first group 314 of hexagonal units. 301. The first group 314 of hexagonal units 301 may be arranged between the central hexagonal unit 312 and the second group 315 of hexagonal units 301.

[0094] The hexagonal units 301 may gradually reduce in thickness from the attachment opening 137 to the main body 102. For example, the central hexagonal unit 312 may define a first thickness 320. The lattice walls 132 of each hexagonal unit 301 of the first group 314 of hexagonal units 301 may define a second thickness 322 that is less than the first thickness 320. The lattice walls 132 of each hexagonal unit 301 of the second group of hexagonal units 301 may define a third thickness 324 that is less than the first thickness 320 and the second thickness 322. Finally, the lattice walls 132 of the hexagonal units 301 in the main body 102 may define a fourth thickness 326 that is less than the first thickness 320, the second thickness 322, and the third thickness 324.

[0095] Referring now to [Fig. 14], a flowchart diagram of one embodiment of a method 800 for manufacturing a composite panel is illustrated in accordance with embodiments of the present subject matter. In general, the method 800 will be described herein with reference to the composite panels and core structures described above with reference to FIGS. 1-13. However, those of ordinary skill in the art will understand that the described method 800 can generally be used with any suitable composite panel. Furthermore, although [Fig. 14] depicts the steps performed in a particular order for purposes of illustration and explanation, the methods explained herein are not limited to any particular order or arrangement unless otherwise indicated in the claims.Those skilled in the art, using the descriptions provided herein, will appreciate that the various steps of the methods described herein may be omitted, rearranged, combined, or adapted in various ways without departing from the scope of this description. The dotted boxes may indicate optional steps of the method 800.

[0096] As shown in [Fig. 14], the method 800 may comprise at (802) fabricating a core structure comprising a main body, an attachment portion, and at least one face, the attachment portion defining a first portion of an attachment opening. As explained above with reference to FIGS. 1-13, the core structure may comprise a main body that comprises a plurality of hollow cells (FIGS. 1-4, 6, and 8-13) or that is solid (FIGS. 5 and 7).

[0097] In some embodiments, manufacturing at (802) may further comprise at (804) additively manufacturing the core structure. For example, all or a portion of the core structure may be additively manufactured, such as via binder jetting or a similar process to produce a core structure. additively manufactured. For example, the main body, the attachment portion, and the first portion of the attachment opening may be additively manufactured. Additively manufacturing the attachment portion and the first portion of the attachment opening may advantageously avoid the need for post-machining of the composite panel or core structure, thereby minimizing machining costs. In particular, the core structure shown in any one of the figures may be additively manufactured to produce the plurality of hollow cells. In this manner, the plurality of lattice walls may be additively manufactured by building up all or a portion of the plurality of lattice walls layer by layer, such as using a powder feedstock material.

[0098] In such embodiments, additive manufacturing of the plurality of lattice walls may result in a residual amount of loose unconsolidated powder feedstock within the hollow interior of each of the plurality of hollow cells. Thus, in some embodiments, the method 800 may further comprise removing the powder feedstock from at least one of the plurality of hollow cells. For example, the powder feedstock may be poured or sucked through an opening of the hollow cell. Removing the powder feedstock may also allow the unused powder feedstock to be recycled and used to manufacture core structures for additional composite panels or other portions of the composite panel.

[0099] Although additive manufacturing is described as an exemplary method of manufacturing the core structure, it will be appreciated that other ceramic processing techniques may also be used within the scope of the present disclosure, such as extrusion processing. Depending on the materials used, the manufacturing process, or other manufacturing variables, the core structure may be ready for use in the composite panel or may require one or more additional intermediate processing steps. For example, in some embodiments, the core structure may be in a green state after additive manufacturing. Thus, in such embodiments, the method may further comprise curing the core structure to remove moisture or sintering the core structure.

[0100] In exemplary embodiments, the method 800 may further comprise at (806) bonding a composite sheet to at least one face, such as a first face of the core structure. In non-limiting examples, the composite face sheet may be bonded to both the main body and the attachment portion of the core structure. The bonding may comprise any suitable process for mechanically integrating the composite sheet to the core structure. For example, the bonding at (806) may comprise adhesive bonding. In some embodiments, bonding to (806) may include one or more manufacturing steps used in the manufacture of ceramic matrix composites, such as infiltration of the ceramic material or curing.

[0101] In exemplary implementations, bonding at (806) may further comprise at (808) bonding the composite sheet to the at least one face such that a second portion of the attachment opening aligns with the first portion of the attachment opening. For example, the composite sheet may define the second portion of the attachment opening, which may be aligned with the first portion of the attachment opening before or during bonding of the composite sheet to the core structure.

[0102] In some embodiments, the method may further comprise adhering a second composite sheet to a second side of the core structure such that a third portion of the attachment opening aligns with the first and second portions of the attachment opening. For example, the second attachment sheet may adhere to another surface of the core structure, and the second attachment sheet may define a third portion of the attachment opening.

[0103] The composite panels as described and disclosed herein may be used in a variety of industrial machinery, including, but not limited to, one or more turbomachinery components. In addition, the composite panels described and disclosed herein may provide a more economical, lighter, and potentially stronger alternative to solid composite structures. It is understood that the features of each of the embodiments shown in the figures and explained above may be combined with the features of other embodiments. However, the composite panels described and disclosed herein further provide improved bonding between the core structure and the composite sheets.In some cases, the composite panels disclosed herein may allow for differential thermal growth, less set-up tooling (since the plies are set against the center), the ability to avoid beads or other filler materials to form bend radii, less machining of the final part (lower cost), less coated fibers (lower cost) by using coated fibers only where needed, or other advantages.

[0104] Other aspects are provided by the subject matter of the following clauses:

[0105] A composite panel comprising a central structure comprising a main body defining at least one face, wherein a fastening portion is formed integrally with the main body, and the fastening portion defines a first portion of a fastening opening, a composite sheet adhered to the at least one face of the central structure, wherein the composite sheet defines a second portion of the fastening opening, wherein the first portion of the fastening opening and the second portion of the fastening opening align along a common axis.

[0106] A composite panel according to any preceding clause, wherein the fixing portion forms a local thickened feature.

[0107] A composite panel according to any preceding clause, wherein the local thickened feature is a flange.

[0108] A composite panel according to any preceding clause, wherein the fixing portion extends away from the main body to a terminal end, and wherein the fixing aperture is disposed between the main body and the terminal end of the fixing portion.

[0109] A composite panel according to any preceding clause, wherein the at least one face comprises a first face and a second face, wherein the first portion of the fixing opening extends between the first face and the second face.

[0110] A composite panel according to any preceding clause, wherein the composite sheet is a first composite sheet bonded to the central structure at the first face, and wherein the composite panel further comprises a second composite sheet bonded to the central structure at the second face, wherein the first composite sheet defines the second portion of the attachment opening, and wherein the second composite sheet defines a third portion of the attachment opening.

[0111] A composite panel according to any one of the preceding clauses, wherein the central structure further comprises a plurality of hollow cells.

[0112] A composite panel according to any preceding clause, wherein at least one of the plurality of hollow cells comprises a hexagonal shape.

[0113] A composite panel according to any preceding clause, wherein the composite sheet comprises a recess, and wherein the second portion of the fixing opening extends from the recess.

[0114] A composite panel according to any preceding clause, wherein the fixing aperture defines a non-circular shape.

[0115] A composite panel according to any preceding clause, wherein the attachment portion has a material density that is greater than a material density of the main body.

[0116] A composite panel according to any preceding clause, wherein the main body is defined by a first lattice having a plurality of lattice walls in a first lattice pattern.

[0117] A composite panel according to any preceding clause, wherein the attachment portion is defined by a second lattice having a plurality of lattice walls in a second lattice pattern that is different from the first lattice pattern.

[0118] A composite panel according to any preceding clause, wherein the composite sheet comprises a ceramic matrix composite.

[0119] A composite panel according to any one of the preceding clauses, wherein the core structure comprises a matrix of silicon, silicon carbide, alumina, carbon, aluminosilicates, or combinations thereof.

[0120] A composite panel according to any preceding clause, wherein the core structure is an unreinforced core structure.

[0121] A method of manufacturing the composite panel according to any one of the preceding clauses, the method comprising the manufacturing of the central structure comprising the main body defining the at least one face, and the bonding of the composite sheet to the at least one face.

[0122] A method according to any one of the preceding clauses, wherein the manufacturing of the core structure comprises additive manufacturing of the core structure.

[0123] A method according to any one of the preceding clauses, wherein the core structure comprises silicon, silicon carbide, alumina, carbon, aluminosilicates or combinations thereof.

[0124] A method according to any preceding clause, wherein the composite sheet comprises a ceramic matrix composite.

[0125] This written description uses examples to describe the present disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including the manufacture and use of any devices or systems and the performance of any methods incorporated therein. The patentable scope of the description is defined by the claims, and may include other examples that occur to persons skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

Claims

1. 1 A composite panel comprising: a core structure comprising a main body defining at least one face, wherein a fastening portion is formed integrally with the main body, and the fastening portion defines a first portion of a fastening opening; and a composite sheet bonded to the at least one face of the core structure, wherein the composite sheet defines a second portion of the fastening opening, wherein the first portion of the fastening opening and the second portion of the fastening opening align along a common axis.

2. 2 A composite panel according to claim 1, wherein the fixing portion forms a local thickened feature.

3. 3 A composite panel according to claim 2, wherein the local thickened feature is a flange.

4. 4 A composite panel according to claim 1, wherein the fastening portion extends away from the main body to a terminal end, and wherein the fastening opening is disposed between the main body and the terminal end of the fastening portion.

5. 5 A composite panel according to claim 1, wherein the at least one face comprises a first face and a second face, wherein the first portion of the fixing opening extends between the first face and the second face.

6. 6 A composite panel according to claim 5, wherein the composite sheet is a first composite sheet bonded to the central structure at the first face, and wherein the composite panel further comprises a second composite sheet bonded to the central structure at the second face, wherein the first composite sheet defines the second portion of the attachment opening, and wherein the second composite sheet defines a third portion of the attachment opening.

7. 7 A composite panel according to claim 1, wherein the central structure further comprises a plurality of hollow cells.

8. 8 A composite panel according to claim 7, wherein at least one of the plurality of hollow cells comprises a hexagonal shape.

9. 9 A composite panel according to claim 1, wherein the composite sheet has a recess, and wherein the second portion of the fastening opening extends from the recess.

10. 10 A composite panel according to claim 1, wherein the attachment opening defines a non-circular shape.

11. 11 A composite panel according to claim 1, wherein the fixing portion comprises a material density that is greater than a material density of the main body.

12. 12 The composite panel of claim 1, wherein the main body is defined by a first lattice having a plurality of lattice walls in a first lattice pattern.

13. 13 A composite panel according to claim 12, wherein the attachment portion is defined by a second lattice having a plurality of lattice walls in a second lattice pattern that is different from the first lattice pattern.

14. 14 A composite panel according to claim 1, wherein the composite sheet comprises a ceramic matrix composite.

15. 15 A composite panel according to claim 1, wherein the core structure comprises a matrix of silicon, silicon carbide, alumina, carbon, aluminosilicates, or combinations thereof.

16. 16 A composite panel according to claim 15, wherein the core structure is an unreinforced core structure.

17. 17 A method of manufacturing the composite panel according to claim 1, the method comprising: manufacturing the central structure comprising the main body defining the at least one face; and bonding the composite sheet to the at least one face.

18. 18 The method of claim 17, wherein manufacturing the core structure comprises: additively manufacturing the core structure.

19. 19 The method of claim 18, wherein the core structure comprises silicon, silicon carbide, alumina, carbon, aluminosilicates or combinations thereof.

20. 20 The method of claim 17, wherein the composite sheet comprises a ceramic matrix composite.

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