PRODUCT WITH A SET OF CENTRAL ELEMENTS OR HOLES AND INTERPOSED SHEETS AND PROCEDURES FOR FORMING SAID PRODUCT

Abstract

A panel (20) having opposing surfaces (22, 24) and including laminae (42, 43) and elongated cores or cavities (40). The cores / cavities extend parallel along a first direction (X), are arranged adjacent to each other in a second direction (Y), and include an outermost core / cavity (40a) along an edge of the panel (26). Each lamina includes a medial portion (44, 45) between two adjacent cores / cavities, a first lateral portion (46, 47) folded away from the medial portion over an adjacent core / cavity and toward the second direction along the first surface, and a second lateral portion (48, 49) folded away from the medial portion over another adjacent core / cavity and toward a second negative direction (-Y) along the second surface.The sheets include a wrap-around sheet (43), the first lateral portion (47) of which extends into a folded lateral region (50, 52) that at the edge of the panel is folded around the outermost core / void, and extends in the second negative direction towards the second surface.

Description

PRODUCT WITH A SET OF CENTRAL ELEMENTS OR HOLES AND INTERPOSED SHEETS AND PROCEDURES FOR FORMING SAID PRODUCT Technical field The invention relates to a product with a set of central or hollow elements and interposed sheets. Furthermore, the invention relates to methods for manufacturing said product. Technical background There are panels known to be particularly well-suited for supporting stationary and / or moving objects with a large mass. A bridge deck, for example, must be strong enough to support the combined weight of the bridge and the traffic it carries, and it also needs a robust surface that remains intact when subjected to local loads from traffic, falling objects, and the like. Patent publication WO2010 / 008293A2 describes a composite panel consisting of a series of parallel core elements connected by strips that extend between the core elements and continue above and below them, overlapping to form outer cladding layers. The strips are bonded using a hardened resin applied and cured via resin transfer molding (RTM). This known construction method results in a robust bond between the core elements and the outer cladding layers, helping to reduce the likelihood of the outer cladding layers detaching from the core elements under localized loads. It would be desirable to provide a panel or similar product with improved robustness. Brief description of the inventionTherefore, according to a first aspect of the invention, a product, such as a panel, is provided, defining opposing first and second surfaces. The product comprises sheets and core elements or hollows between the sheets. The core elements or hollows are elongated and extend parallel to each other along a first direction. These core elements or hollows are arranged adjacent to each other in a second direction and include an outermost core element or hollow along an edge of the product. Each sheet defines a medial portion, a first lateral portion, and a second lateral portion. The medial portion is interposed between two adjacent core elements or hollows. The first lateral portion is folded away from the medial portion over one of the two adjacent core elements or hollows, predominantly in the second direction along the first surface.The second lateral portion is folded away from the medial portion over another of the two central elements or two adjacent hollows, and predominantly in a second negative direction along the second surface. The sheets include at least one enveloping sheet whose first lateral portion extends into a folded lateral region located at or near the edge of the product, folded away from the first surface and around the outermost central element or hollow, to extend with a non-zero component in the second negative direction toward the second surface. The term sheet is used here to refer to a piece of material that is thin compared to its length and width dimensions. Preferably, such a sheet is quadrilateral in shape, and more preferably rectangular. Medial portions are interposed between the core elements or voids of the sheets, and these continue with the lateral portions above and below the cores / voids in an overlapping manner, to jointly form outer coating layers along the first and second surfaces. The first and second lateral portions of adjacent sheets overlap each other, at least partially, on the first and second surfaces, respectively, to form the outer coating layers. The product sheets, according to this aspect, can be made of various materials, which may be initially rigid (i.e., before product construction) but plastically deformable to allow bending or folding of the sheet along desired bend lines when subjected to forces, while other regions of the sheet remain dimensionally stable under the loads associated with normal product operating conditions. For example, the initially rigid sheet materials may consist essentially of aluminum sheet material, steel sheet material, thermoplastic sheet material, or similar materials. Alternatively, the sheet material may be initially flexible (before product construction) to allow bending or folding into a desired sheet configuration.The manufacture of this product must include a hardening step for the sheets, allowing them to settle into essentially fixed orientations with respect to the finished product. This hardening step may include, for example, impregnating the sheets with a resin, followed by curing the resin to form a rigid matrix into which the sheet material is embedded. Impregnation of the sheets may be carried out, for example, by resin transfer molding (RTM) or void-assisted resin transfer molding (VARTM) of a preformed arrangement of sheets. Alternatively, individual sheets may be impregnated and molded in advance (pre-impregnated sheets), followed by stacking and bonding the sheets to form a desired profile.Alternatively, the sheets can be impregnated directly before being arranged in the desired profile, for example, by immersion. The material of the initially flexible sheets can consist, for example, of a woven fiber material (e.g., a net, mesh, or mat). In other alternative embodiments, composite constructions can be used with initially rigid sheets and initially flexible sheets, for example, laminated structures of glass-reinforced aluminum. The sheets extend along and between the core or cavity elements in a Z-shaped pattern, with individual medial portions of the sheets sandwiched between two adjacent cores or cavities. The phrase "predominantly toward a second positive direction +Y along the first surface" is used here to indicate that the first lateral portion of each sheet extends with a large vector component in the second positive direction parallel to the first panel surface, compared to a relatively small or vanishing vector component in a third direction—that is, out of the plane. The first lateral portions may be oriented at a slight non-zero angle to this second positive direction.Similarly, the phrase "predominantly toward a second negative direction—and along the second surface" is used here to indicate that the second side portion of each sheet extends with a large vector component in the second negative direction parallel to the second surface of the panel, compared to a relatively small or vanishing vector component in an out-of-plane direction. The second side portions may also be oriented at a slight non-zero angle with respect to this second negative direction. The product may include elongated core elements, which help define the product's shape during construction and provide additional rigidity. These core elements can be made, for example, of a rigid, lightweight material such as polyurethane (PU) foam. However, the space between the sheets does not need to be filled with core material. The molded sheet material (e.g., folded or hardened) in the finished panel may already have sufficient rigidity, thus eliminating the need for core elements. Composite panels with voids instead of cores, enclosed by respective pairs of adjacent medial sheet portions and pairs of lateral sheet portions, can be manufactured using pultrusion and autoclave techniques, which are known per se (e.g., from the publication of patent WO2016 / 085336A1). The term "outermost center element or cavity" here refers to a center element or cavity located closer to an edge of the product that is parallel to the direction of elongation of the center elements. The term "closest" here refers to a distance on the order of less than one typical transverse dimension of the center elements or cavities. The term "wrap sheet" here refers to a sheet that extends lengthwise between adjacent core elements or hollows in a regular arrangement (e.g., a Z pattern), but also extends around the outermost core element or hollow, wrapping it in transverse and vertical directions (but not necessarily in longitudinal directions). If at least one of the interposed sheets is made of fiber material, such as a wrap sheet that folds around the outermost core element or hollow and toward the second surface, the edge of the product can be effectively sealed by the sheet. The resulting arrangement of cores / hollows and sheets produces a panel with a sealed and reinforced edge. Preferably, the folded side region of the wrap sheet covers at least a second side portion of an adjacent sheet. A product of this type can be used, for example, in a composite construction, in the form of a panel (e.g., in a bridge, bridge deck, or lock gate), an airfoil (e.g., a wing, rudder blade, or turbine blade), or a similar structure. The product defines first and second surfaces on opposite sides, both surfaces extending with a significant vector component along the second Y direction. Such a product may, for example, constitute or include a panel, in which the first and second faces are predominantly planar (i.e., flat). The first and second surfaces may be oriented parallel to each other to obtain a product (e.g., a panel) with a predominantly rectangular cross-section and uniform thickness.The first surface can also be oriented at a non-zero angle with respect to the second surface, to obtain a product with a prismatic (e.g., trapezoidal) cross-section. Furthermore, the first and second surfaces can be curved along the second Y direction, for example, in the shape of a curved wing. According to one embodiment, the central or hollow elements include a penultimate central or hollow element, which is arranged lengthwise and adjacent to the outermost central or hollow element, and the laminae include an outermost lamina. The medial portion of this outermost lamina is interposed between the outermost central or hollow element and the penultimate central or hollow element. The first lateral portion of this outermost lamina is folded from the medial portion over the outermost central or hollow element predominantly in the second positive direction along the first surface, and the second lateral portion of this outermost lamina is folded from the corresponding medial portion over the penultimate central or hollow element predominantly in the second negative direction along the second surface. The folded lateral region of the enveloping sheet includes another folded lateral region that is folded predominantly towards the second negative direction along the second surface to overlap, at least partially, with the second lateral portion of the outermost sheet. The term outermost sheet here refers to a sheet member that is positioned with its medial sheet portion between the outermost core / hole and the adjacent (i.e., penultimate) core / hole. By arranging the outermost sheet with a first lateral portion folded around the outermost core / hole and backward to rest on its second lateral portion, the structural integrity and / or edge sealing of the product can be further enhanced. The term overlap and the expression A overlaps (with) B are used here to indicate that part or all of object A extends over and covers at least part or all of object B. Furthermore, the expression A overlaps (with) B in / along direction Q is used here to indicate that A extends in the manner described over part or all of B along direction Q. As a result, object A covers part or all of object B when viewed along at least one direction perpendicular to Q. Consequently, object A covers part or all of object B when viewed along at least one direction perpendicular to Q. The overlap of A and B may imply, but does not necessarily imply, that A and B are in direct physical contact. Overlap defines a reciprocal spatial relationship, in that A overlapping B also implies that B overlapping A. To further improve the strength and sealing of the product's edge, the outermost sheet can be formed as one of the wrapping sheets. This outermost sheet includes a first lateral portion extending into a lateral region that is folded away from the first surface and along the outermost central element, and another folded lateral region that is folded in the opposite direction along the second surface, to overlap at least partially with the second lateral portion of the outermost sheet. However, the outermost sheet does not necessarily have to form one of the wrapping sheets. Instead, the wrapping sheets can be associated with cores or cavities located further from the edge of the product, while the outermost sheet is folded in a regular arrangement (for example, following a Z pattern) without extending around the outermost core or cavity. According to one embodiment, the sheets comprise a penultimate sheet whose corresponding first lateral portion extends into a folded lateral region that is folded outward from the first surface around the outermost central element or cavity, and another folded lateral region that is folded predominantly toward the second negative direction along the second surface, to overlap at least partially with the second lateral portion of the outermost sheet, and optionally also overlaps at least partially with another folded lateral region of the outermost sheet. The outermost sheet can be a wrapping sheet, and the additional lateral region of the penultimate sheet can overlap (partially) with the second lateral portion, as well as with the additional lateral region of the outermost sheet. In this arrangement, the additional lateral region of the outermost sheet is positioned between the additional lateral region of the penultimate sheet, on one side, and the second lateral portion of the outermost sheet, on the other. Alternatively, the outermost lamina may be a non-enveloping lamina, and the outermost lamina region of the penultimate lamina may overlap (partially) directly with the second lateral portion of the outermost lamina. According to one embodiment, the core elements or hollows include a series of consecutive outer core elements or hollows, and the sheets include a series of consecutive wrapping sheets, the first lateral portion of which extends into a folded lateral region that is folded away from the first surface around the outermost core element or hollow, and into an additional folded lateral region that is folded predominantly towards the second negative direction along the second surface to overlap at least partially with the additional folded lateral region of a previous wrapping sheet. MA / a / ZUZZ / UU l According to some embodiments, the product includes one or more reinforcing strips in various locations. The strips may be made of a fiber-reinforced plastic sheet, a solid body of plate material, or a composite material. The strips may be made, for example, of a unidirectional fiber composite material having a modulus of elasticity along the fiber exceeding 35 gigapascals (GPa) or, preferably, exceeding 100 GPa, and a tensile strength along the fiber exceeding 800 megapascals (MPa) or, preferably, exceeding 1200 MPa.Examples of webbing materials include unidirectional glass fiber composite (webbing modulus E ~ 39 GPa, tensile strength ~ 900 MPa), high-strength unidirectional carbon fiber composite (webbing modulus E ~ 120 GPa, tensile strength ~ 1900 MPa), or high-modulus unidirectional carbon fiber composite (webbing modulus E = 330 GPa, tensile strength = 1300 MPa). For example, the product may include at least one strip, which extends close to the second surface and is substantially parallel to at least one core or gap, and which is sandwiched between the second side portions of two adjacent sheets. Alternatively or additionally, the product may include an intermediate strip, which extends close to the second surface substantially parallel to at least one central element or gap, and which is sandwiched between the most folded side region of a wrapping sheet and the second side portion of the same wrapping sheet, or sandwiched between the most folded side region of the wrapping sheet and the second side portion of an adjacent non-wrapping sheet. Alternatively or additionally, the product may include at least one edge band extending close to the second surface substantially parallel to at least one center element or gap, and sandwiched between the most folded side regions of two adjacent wrapper sheets. One of these edge bands may be located, for example, along the outermost center element, between the most folded side region of the outermost sheet and the most folded side region of the penultimate sheet. Alternatively or additionally, the product may include at least one more strip, extending close to the first surface substantially parallel to at least one central element or gap, and situated between the first side portions of two adjacent sheets. One of these additional strips may be situated, for example, along the outermost central element, and between the first side portion of the outermost sheet and the first side portion of the penultimate sheet. Any of the strips and / or additional strips may be sandwiched along their entire length between two side sheet portions. Alternatively, any of the strips may be positioned with a portion extending lengthwise along and touching a surface of a core element facing the second panel surface, or extending lengthwise along a corresponding surface of a core cavity. Similarly, any of the additional strips may be partially positioned lengthwise along and touching a surface of a core element facing the first panel surface, or extending lengthwise along a corresponding surface of a core cavity. In some embodiments, the first lateral portion of each sheet is folded predominantly in the second positive direction along the first surface, such that the first lateral portion forms a first inclination angle β1 in the range of 0° < β1 < 5° with respect to the first surface. Preferably, the first inclination angle β1 is in the range of 0° < β1 < 2°. Alternatively or additionally, the second lateral portion of each sheet may be folded predominantly in the second negative direction along the second surface, such that the second lateral portion is at a second inclination angle β2 in the range of 0° < β2 < 5° with respect to the second surface. Preferably, the second inclination angle β2 is in the range of 0° < β2 < 2°. In the case where the first and second surfaces of the product are essentially parallel, the first and second inclination angles are preferably essentially identical (β1 = β2). iviA / a / ¿u¿¿ / uu / 4yo According to some embodiments, the first lateral portion of the sheet is folded predominantly in the second positive direction, along the first surface, over a sequence of at least three central elements or three adjacent gaps. The resulting overlapping arrangement of the sheet portions then includes overlaps of at least three first lateral portions of the corresponding three adjacent sheets. The overlap of the first lateral portions of the sheet can include, for example, four to six layers, to achieve a good balance between product strength and manufacturing complexity. Alternatively or additionally, the second lateral portion of the sheet is folded predominantly in the second negative direction, along the second surface, over a sequence of at least three opposing adjacent cores or hollows. The resulting overlapping arrangement may therefore include overlaps of at least three second lateral portions of the corresponding three adjacent sheets. Similarly, the overlap of the second lateral portions of the sheets may include, for example, four, five, or six layers. Preferably, the number of overlapping sheet layers is the same on both surfaces of the product. Furthermore, the lengths of the (more) folded side regions can be such that the number of overlapping layers near the edge of the product is the same as that of the second overlapping side portions (i.e., three or more). The arrangement of the sheets and cores or cavities according to the first aspect (and its various embodiments) can be similarly applied on another edge of the product, for example, on the edge of the product on the opposite side of the core or cavity assembly, viewed along the second direction. One or more enveloping sheets can be arranged around another, more external core or cavity on this opposite edge of the product, and can be arranged symmetrically to the third direction. In some embodiments, the core elements or voids have cross-sectional symmetry about planes perpendicular to the first direction. These planes are parallel to the second and third directions, and the cross-sectional shapes of the core elements or voids can be symmetric about a line within this plane, or rotationally symmetric about an axis along the first direction. Alternatively or additionally, the core elements or voids may be geometric prisms with polygonal cross-sectional shapes in planes perpendicular to the first direction. Preferably, these polygonal shapes are triangular, quadrilateral, pentagonal, or hexagonal. More preferably, these polygonal shapes are regular triangles or rectangles. The product may be substantially flat along the third direction, or it may have a concave shape with a smooth curvature in the third direction depending on the first and / or second directions. According to a second aspect, and in accordance with the advantages and effects described above, a reinforced composite material construction is provided, in particular a bridge, bridge deck, lock gate, turbine blade, or wing. This reinforced composite material construction includes a product (for example, a panel or an airfoil profile) according to the first aspect. The product embodiments according to the first aspect can be manufactured using various procedures. Different procedures can be selected for products with different characteristics. For example, a product can be manufactured using RTM techniques and include core elements enclosed between the various sheet portions, or it can be manufactured using pultrusion techniques and include voids instead of core elements in several or all of the corresponding positions. According to a third aspect, a procedure is provided for manufacturing a product with first and second surfaces on opposite sides. The procedure comprises placing elongated central elements parallel to each other, and placing sheets of foldable material extending along and between the central elements in a support structure.This placement of the core elements and laminae includes: - placing the core elements mutually parallel and extending along a first direction, and adjacent to each other in a set along a second direction, with an outermost core element along an edge; interposing a medial portion of a lamina between two adjacent core elements; folding a first lateral portion of the lamina away from its medial portion over one of the two adjacent core elements and predominantly towards the second direction along the first surface; and - folding a second lateral portion of each lamina away from its medial portion over another of the two adjacent core elements and towards a second negative direction along the second surface.The sheets include an enveloping sheet with a first lateral portion extending into a lateral region and another lateral region, and the procedure further comprises: - folding the lateral region away from the first surface and around the outermost core element, and folding the additional lateral region with a non-zero component in the second negative direction towards the second surface. The procedure may further comprise placing the sheets in a sheet arrangement in which the side portions and other side portions of adjacent sheets overlap at least partially. According to one embodiment, the sheets include an outermost sheet with a first lateral portion extending into a lateral region and another lateral region, and with a second lateral portion. The procedure may comprise: - folding the lateral region away from the first surface and around the outermost central element, and - folding the additional lateral region in the second negative direction along the second surface to create at least a partial overlap with the second lateral portion of the outermost sheet. In another embodiment, the procedure comprises placing at least one strip along a respective central element. The strip(s) is / are sandwiched between the first side portions of two adjacent sheets, the second side portions of two adjacent sheets, the most folded side region of an enclosing sheet and the second side portion of the same enclosing sheet, the most folded side region of the enclosing sheet and the second side portion of an adjacent non-enclosing sheet, or the most folded side regions of two adjacent enclosing sheets. In some embodiments, the sheets essentially comprise foldable fiber material, and the process comprises: impregnating the sheets or the assembly of sheets with folded side portions with a hardenable substance (for example, a resin), and allowing the hardenable substance to harden to form the product, thereby fixing the first overlapping side portions and the second overlapping side portions of the sheets together. If one or more reinforcing strips are placed between adjacent sheets, these strips can be impregnated with the hardenable substance along with the sheets before hardening. The support structure may be, for example, a mold to delimit the set of sheets and core elements during the impregnation stage. This mold may include a mold rim to delimit the product during molding, and the outermost core element may be positioned along the mold rim. The process may further include, during the impregnation stage, enclosing the cores and sheets under a temporary covering layer in a manner airtight with respect to the mold. In other alternative embodiments of the process, the sheets may already be provided in the form of rigid structures. The sheets can then be positioned and fastened together in the desired arrangement using appropriate methods, which can be selected based on the sheet material used, for example, by using adhesives, welding, rivets, or fusion bonding. According to a fourth aspect, a method for manufacturing a product (e.g., a panel) is provided. This method comprises: - providing a plurality of sheets of fiber material; - providing an arrangement of forming elements, which extend predominantly in a first direction, and which are arranged adjacent to each other in a second direction, simultaneously defining gaps between pairs of adjacent forming elements;- move continuously and simultaneously the laminae predominantly in the first direction through the gaps and along the forming elements - during the movement, bend each lamina around a respective forming element to form a medial lamina portion between two adjacent forming elements, a first lateral lamina portion that projects predominantly in a second positive direction transversely with respect to the medial lamina portion, and a second lateral lamina portion that projects predominantly in a second negative direction transversely with respect to the medial lamina portion;- causing the first side sheet portions of different sheets to at least partially overlap each other, and causing the second side sheet portions of different sheets to at least partially overlap each other. In this way, a sheet assembly is formed with folded side sheet portions and gaps, wherein the gaps are enclosed by a pair of adjacent medial portions and a pair of first and second side sheet portions. These steps can be carried out, for example, using a forming device with forming elements as described in Figures 2a-3c and in paragraphs 30-34 of patent publication WO2016 / 085336A1, which is incorporated herein by reference. However, the procedure according to this fourth aspect further comprises: - while moving the sheets, folding a lateral region of the first lateral portion of at least one enveloping sheet at or near the edge of the product, away from a first surface around an outermost forming element, and with a non-zero component in the second negative direction towards a second surface. The outermost gap is thus also enclosed by a medial sheet portion and the first lateral portion of the enveloping sheet. In one embodiment, the process includes folding the first side portions of the sheet and the second side portions of the sheet by moving a forming element, such as a roller, in the second and third directions around a contour, which is defined by the forming elements and which has a contour axis directed predominantly along the first direction. In some embodiments, at least one reinforcing strip is continuously and simultaneously inserted between the sheets as they move through the gaps and along the forming elements. Such strips may be interposed between the first lateral portions of two adjacent sheets, the second lateral portions of two adjacent sheets, the most folded lateral region of an enveloping sheet and the second lateral portion of the same enveloping sheet, the most folded lateral region of the enveloping sheet and the second lateral portion of an adjacent non-enveloping sheet, or the most folded lateral regions of two adjacent enveloping sheets. In some embodiments, the procedure further comprises: impregnating the sheets or the set of sheets with folded side portions with a hardening substance, and causing the hardening substance to harden to form the product, such that gaps remain, where each gap is enclosed by a pair of adjacent middle portions and a pair of first and second side sheet portions. Brief description of the drawings The embodiments will now be described, by way of example only, with reference to the accompanying schematic drawings, in which the corresponding reference symbols indicate the corresponding parts. In the drawings, similar numbers designate similar elements. Multiple instances of an element may each include separate letters appended to the element number. For example, two specific instances of a particular element 20 may be labeled with appended letters, for example, 20a and 20b. The element label may be used with an index i0j (for example, 20i) to refer to an unspecified instance of the element, while the element label may be used without an appended letter (for example, 20) to refer generally to every instance of the element. Figure 1 schematically shows a perspective view of a part of a composite panel according to one embodiment; Figure 2 presents a schematic cross-sectional view of the panel in Figure 1, and Figure 3 shows a cross-sectional view of an alternative embodiment of a composite panel. The figures are for illustrative purposes only and do not serve to restrict the scope or protection established in the claims. Description of the achievements The following describes certain embodiments of the invention, given only by way of example and with reference to the figures. In the figures, Cartesian coordinates will be used to describe the spatial relationships of the example embodiments of the product. The term surface is used herein to refer generally to a two-dimensional parametric surface region, which may have a completely or partially flat shape (e.g., a planar or polygonal surface), a curved shape (e.g., a cylindrical, spherical, parabolic surface, etc.), a recessed shape (e.g., a stepped or wavy surface), or a more complex shape. The term plane is used here to refer to a flat surface defined by three non-coincident points. Figure 1 schematically shows a perspective view of a portion of a composite panel 20 according to one embodiment. In Figure 1, some portions of panel 20 have been virtually cut in a stepped fashion, simply to illustrate the arrangement of the various core elements and fiber-reinforced sheets. However, it should be understood that the relative positions of the cross-sectioned sides of the elements and sheets may deviate from Figure 1, and they may all be aligned, for example, along the same nominal plane (e.g., being bounded by a projecting edge of a molding table). Figure 2 presents a schematic cross-sectional view of panel 20 of Figure 1. Figures 1 and 2 show that panel 20 includes a series of core elements 40 and fiber-reinforced sheets 42 and 43. Each core element 40 (index i = a, b, c...) has an elongated shape extending along a longitudinal direction X. The core elements 40 are arranged parallel to and adjacent to one another in a set along a transverse direction Y, which is perpendicular to X. A vertical direction Z is defined perpendicular to both X and Y. The arrangement of the core elements 40 defines a first surface 22 and a second surface 24 on opposite sides of panel 20, oriented along the positive and negative vertical directions ±Z, respectively. In this embodiment, panel 20 is substantially flat, such that the characteristic dimensions of the panel in the longitudinal and transverse directions X, Y are substantially larger than in the vertical direction Z. Each core element 40 is symmetric about the YZ planes of the cross-section, which are perpendicular to the longitudinal direction X.In this example, the core elements 40 have rectangular cross-section shapes in the local YZ planes, which are rotationally symmetric about the associated central axes A (only the nominal axis Aa is shown in Figure 1). The arrangement of the cores 40 includes an outermost core element 40a, which extends along a longitudinal edge 26 of panel 20. A penultimate core element 40b and a third-to-last core element 40c are arranged in sequence directly next to the outermost core element 40a. Other core elements 40d, etc., are arranged in consecutive positions along the negative transverse -Y direction. Sheets 42, 43 with fiber material can be distinguished into sheets 42 that are located far from the edge of panel 26 and do not wrap around the outermost central element 40a (non-wrapping sheets), and sheets 43 that are located towards the longitudinal edge of panel 26 and do wrap around the outermost central element 40a (wrapping sheets) in the transverse and vertical Y, Z directions. Each lamina 42, 43 includes a medial portion 44, 45, a first lateral portion 46, 47, and a second lateral portion 48, 49. The medial portion 44, 45 is interposed between two corresponding adjacent central elements 40. The first lateral portion 46, 47 of each lamina 42, 43 is folded from the medial portion 44, 45 over the corresponding adjacent first central element 40, in this case in a positive transverse +Y direction, to extend predominantly along the first surface 22. The second lateral portion 48, 49 of each lamina 42, 43 is folded out of the medial portion 44, 45 over the corresponding adjacent second central element 40, in this example in a negative transverse -Y direction, to extend predominantly along the second surface 24. The first lateral portions 46, 47 of the adjacent sheets 42, 43 are arranged in a manner that is at least partially overlapping. The first lateral portion 46, 47 of each sheet 42, 43 is folded over a sequence of three adjacent central elements 40, resulting in an imbricated overlap of three layers along the first surface 22. Similarly, the second lateral portions 48, 49 of the adjacent sheets 42, 43 are arranged in a manner that is at least partially overlapping. The second lateral portion 48, 49 of each sheet 42, 43 is folded over a sequence of three adjacent central elements 40 in the opposite direction, also producing an imbricated overlap of three layers along the second surface 24.The resulting arrangement of the overlapping sheets can be described as an oblique layered material, and the arrangement of the cores and overlapping sheets can be described as a composite oblique layered structure. The first lateral portion 46, 47 of each sheet 42, 43 is oriented along the transverse Y direction at a first tilt angle β1 with respect to the first surface 22. Similarly, the second lateral portion 48, 49 of each sheet 42, 43 is oriented along the transverse Y direction at a second tilt angle β2 with respect to the second surface 24. The top and bottom surfaces of the rectangular cores 40 are tilted at similar angles, with each core 40 of the assembly slightly rotated around its central axis of core A (e.g., core 40a around the nominal axis Aa in Figure 1). This tilted arrangement allows the lateral portions of the sheets 46–49 to extend flat along each other, thereby taking advantage of the sheets' tensile strength and improving the panel's strength.In this example, the first and second surfaces of panel 22, 24 are essentially parallel, and the first and second tilt angles are essentially identical β1 = β2. The value of these angles is preferably small, for example, 0° < β1, β2 < 5° or even 0° < β1, β2 < 2°. MA / a / ZUZZ / UU l The enveloping sheets 43 include an outermost sheet 43a along the longitudinal edge of panel 26. In addition, the enveloping sheets 43 include a penultimate sheet 43b, and an antepenultimate enveloping sheet 43c, which are arranged sequentially and associated with the subsequent central elements 40. The medial portion 45a of the outermost sheet 43a is interposed between the outermost central element 40a and a penultimate central element 40b. The first lateral portion 47a of the outermost sheet 43a extends into a lateral region 50a and another lateral region 52a. These lateral sheet regions 50a-52a form flat regions that are folded at different angles to each other. The first lateral sheet region 50a is folded out of the first lateral portion 47a along the first surface 22, and downward in a negative vertical -Z direction along the outermost central element 40a and the longitudinal edge of panel 26. The second lateral sheet region 52a is folded out of the lateral sheet region 50a, in the opposite transverse -Y direction along the second surface 24.The second lateral plate region 52a extends further along the second surface 24, to overlap at least partially with the second lateral portion 49a of the outermost plate 43a. The medial portion 45b of the penultimate lamina 43b lies between the penultimate core element 40b and a subsequent core element 40c, which is directly adjacent to the penultimate core element 40b. The first lateral portion 47b of the penultimate lamina 43b is folded away from the medial portion 45b and extends in the positive transverse +Y direction along the first surface 22 and over the penultimate core element 40b and the outermost core element 40a. This first lateral portion 47b also extends into a first lateral lamina region 50b and a second lateral lamina region 52b. These lateral lamina regions 50b-52b also form planar regions that fold at different angles to each other. The first side region of sheet 50b is folded out of the first surface 22 and the first side portion 47b, downward in the negative vertical -Z direction and along the outermost center element 40a and the longitudinal edge of panel 26. In this example, the first side sheet region 50b of the penultimate sheet 43b covers the first side sheet region 50a of the outermost sheet 43a. The second side sheet region 52b is folded out of the first side sheet region 50b, in the negative transverse -Y direction and along the second surface 24. In this example, the second side region of sheet 52b of the penultimate sheet 43b covers the second side region of sheet 43a. The side sheet portion 47c and the 50c-52c regions of the third-to-last sheet 43c are arranged analogously and overlap with the corresponding sheet portions 47a-47b and at least part of the sheet regions 50b-52c of the penultimate and outermost sheets 43b, 43a. In this example, the lengths of the most folded side regions 52a-c of the enveloping sheets 43a-c are such that the overlapping arrangement of sheet portions 49 and sheet regions 52 on the second side of panel 24 is also triple-layered near the edge of panel 26. Figure 3 shows a cross-sectional view of an alternative embodiment of a composite panel 120. The features of panel 120 already described above with reference to panel 20 in Figures 1 and 2 may also be present in the panel 120 shown in Figure 3 and will not be discussed again here. For the discussion with reference to Figure 3, and to distinguish the various embodiments, similar features are designated with similar reference numbers preceded by 100. Unlike the embodiment shown in Figure 1, the spaces defined between the various sheet portions of panel 120 form voids 141, which are not occupied by solid core elements. This panel 120 can be manufactured using pultrusion techniques. In other alternative embodiments, some or all of the voids 141 can be occupied by solid core elements similar to the cores 40 in Figure 1. In this embodiment, panel 120 comprises several strips 160-163 of rigid material. In this example, the strips 160-163 are made of a unidirectional fiber composite material having a modulus of elasticity along the fiber greater than 35 GPa and a tensile strength along the fiber greater than 800 MPa. The various strips 160-163 reinforce the resulting panel 120, particularly along its longitudinal edge 126. Strips 160a-160b are arranged close to the second surface 124, extending substantially parallel to the corresponding gaps 141 along the longitudinal X direction. Each of these strips 160 is sandwiched between the second lateral portions 148, 149 of two adjacent sheets 142, 143. In this example, each of the lower strips 160 has a lateral extension of approximately 2.5 times the width of a gap 141. Other strips 163a-163d are arranged close to the first surface 122, and also extend substantially parallel to the corresponding gaps 141 along the longitudinal X direction. Each additional strip 163 is sandwiched between the first lateral portions 146, 147 of two adjacent sheets 142, 143. In this example, an intermediate strip 161 extends close to and along the penultimate gap 141b, close to the second surface of panel 124. This intermediate strip 161 is sandwiched directly between the second side portion 149a and the side region 152a of the outermost sheet 143a. In this example, two edge strips 162a-162b are provided, extending close to and along the outermost gap 141a, on the underside near the second surface of panel 124. The edge strip 162a is sandwiched directly between the side regions 152b, 152c of the penultimate and third wrap-around sheets 143b, 143c. Similarly, the edge protector 162b is sandwiched directly between the side regions 152a, 152b of the outer and penultimate wrap-around sheets 143a, 143b. The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The embodiments described herein should be considered in all respects as illustrative only and not restrictive. In the embodiments described by way of example, the outermost sheet formed a wrap-around sheet, with the first lateral portion extending into a sheet region that folded around the outermost central element and the edge of the product, and then returning along the opposite surface of the panel to cover the second lateral portion of the same outermost sheet. In other panel embodiments, however, only the sheets furthest from the edge of the product may form wrap-around sheets with sheet regions that fold around the outermost central element and toward the second surface of the panel. The product may have fewer or more than three wrapping sheets. In the latter case, additional edge strips may be provided, each of which is sandwiched directly between other folded side regions of adjacent wrapping sheets. Although the panel embodiments described above were predominantly flat, it should be understood that the panel can have different shapes in alternative embodiments. For example, the panel can have a simple concave shape, gradually curving towards the vertical Z direction as a function of the longitudinal X coordinate. Alternatively, the panel can have a concave curvature towards the vertical Z direction as a function of the transverse Y coordinate. More complex shapes can also be conceived, for example, through double curvatures in the longitudinal and transverse directions and / or curvatures with multiple local minima / maxima and / or inflection points. The products can be manufactured using various methods. For example, the product may include core elements enclosed between different sheet metal portions, or it may include gaps instead of core elements in several or all of the corresponding positions. Furthermore, central elements or voids should not be considered limited to elongated structures with essentially square cross-sectional shapes. Central elements with other shapes are also possible. As alternative examples, central elements may have a cross-sectional shape that exhibits discrete rotational symmetry under rotations about their body axis A along the X direction (e.g., a triangular or rectangular shape), and / or have mirror symmetry with respect to one or more lines in the YZ planes, or have more general polygonal (e.g., quadrilateral) or curved cross-sectional shapes. Therefore, the scope of the invention is defined by the appended claims rather than by the preceding description. It will be evident to a person skilled in the art that alternative and equivalent embodiments of the invention can be conceived and reduced to practice. All modifications that affect the meaning and range of the five equivalents of the claims must be included within their scope. Please note that, for reasons of conciseness, the reference numbers corresponding to similar elements in the various embodiments (e.g., elements 110, 210 which are similar to element 10) have been indicated collectively in the 10 claims only by their base numbers, i.e. without the multiples of hundreds. However, this does not suggest that the claimed elements should be interpreted as referring only to the characteristics corresponding to the base numbers. Although similar reference numbers have been omitted from the claims, their applicability will be evident upon comparison with the figures. MA / a / ZUZ^ / UU l List of reference symbols Similar reference numbers used in the description to indicate similar items (but differing only in the hundreds) should be considered implicitly included. mold support surface mold edge mold support frame panel panel surface second panel surface first panel edge (longitudinal edge) second panel edge (opposite longitudinal edge) third panel edge fourth panel edge core element non-wrapping sheet (e.g., strip or plate material) wrapping sheet (e.g., strip or plate material) medial portion of non-wrapping sheet medial portion of wrapping sheet first lateral portion of non-wrapping sheet first lateral portion of wrapping sheet second lateral portion of non-wrapping sheet second lateral portion of wrapping sheet folded lateral region further folded lateral region curable substance (e.g., resin) 141 core hole 160 strips 161 middle strip 162 edge strip 163 additional strip Nominal axis (of the central element) ζ first direction (longitudinal direction) Y second direction (transverse direction) ζ third direction (vertical direction) β1 5 β2 first tilt angle second tilt angle MA / a / ZUZZ / UU ι 4υο

Claims

CLAIMS 1. A product (20), such as a panel, defining opposing first and second surfaces (22, 24), and comprising: - central elements or hollows (40, 141), which are elongated and extend parallel to each other along a first direction (X), which are arranged adjacent to each other in a set along a second direction (Y), and which include an outermost central element or hollow (40a, 141a) along an edge of the product (26); sheets (42, 43), wherein each sheet defines: a medial portion (44, 45) interposed between two adjacent central elements or hollows; a first lateral portion (46, 47) folded opposite to the medial portion over one of the two adjacent central elements or hollows, and predominantly towards a second positive direction (+Y) along the first surface (22);a second lateral portion (48, 49) folded in the opposite direction to the medial portion over another of the two adjacent central elements or hollows, and predominantly towards a second negative direction (-Y) along the second surface (24); wherein the sheets include at least one enveloping sheet (43), the first lateral portion (47) of which extends into a folded lateral region (50, 52) that is on or near the edge of the folded product outside the first surface and around the outermost central element or hollow, to extend with a non-zero component in the second negative direction (-Y) towards the second surface, and which preferably covers at least a second lateral portion (48, 49) of an adjacent sheet.

2. The product (20) according to claim 1, wherein the central elements or hollows (40, 141) include a penultimate central element or hollow (40b, 141b) adjacent to the outermost central element or hollow (40a, 141a), wherein the sheets (42, 43) include an outermost sheet (43a) having a medial portion (45a) interposed between the outermost central element or hollow and the penultimate central element or hollow, a first lateral portion (47a) folded away from the medial portion (45a) around the outermost central element or hollow and predominantly towards the second direction (Y) along the first surface (22), and a second lateral portion (49a) folded away from the corresponding medial portion (45a) over the penultimate central element or hollow predominantly towards the second negative direction (-Y) along the second surface (24);wherein the folded lateral region (50, 52) of the enclosing sheet (43) includes another folded lateral region (52) that is folded predominantly towards the second negative direction along the second surface (24) to overlap, at least partially, with the second lateral portion (49a) of the outermost sheet.; 3. The product (20) according to claim 2, wherein the at least one enclosing sheet (43) includes the outermost sheet (43a), such that the most folded lateral region (52a) of the outermost sheet is folded predominantly towards the second negative (-Y) direction along the second surface (24) to overlap at least partially with the second lateral portion (49a) of the outermost sheet.

4. The product (20) according to claim 2 or 3, wherein the sheets (42) comprise a penultimate sheet (43b) in which the corresponding first lateral portion (47b) extends to: a lateral region (50b) that is folded out from the first surface (22) around the outermost central element or gap (40a, 141a), and another lateral region (52b) that is folded predominantly towards the second negative (-Y) direction along the second surface (24), to overlap at least partially with the second lateral portion (49a) of the outermost sheet (43a), and optionally also overlaps at least partially with another lateral region (52a) of the outermost sheet.

5. The product (20) according to any one of claims 1-4, wherein the central elements or hollows (40, 141) include a series of consecutive outer central elements or hollows (40b, 40c; 141b, 141c), and wherein the sheets (42, 43) include a series of consecutive enveloping sheets (43b, 43c), the first lateral portion (47b, 47c) of which extends into a lateral region (50b, 50c) that is folded outward from the first surface (22) around the outermost central element or hollow (40a, 141a), and into another lateral region (52b, 52c) that is folded predominantly in the second negative (-Y) direction along the second surface (24) to overlap, at least partially, with the other lateral region (52a, 52b) of a anterior enveloping sheet (43a, 43b).

6. The product (120) according to any one of claims 1-5, comprising a strip (160), extending close to the second surface (124) and substantially parallel to at least one central element or gap (40, 141), and sandwiched between the second side portions (148, 149) of two adjacent sheets (142, 143).

7. The product (120) according to any one of claims 1-6, comprising an intermediate strip (161), extending close to the second surface (124) substantially parallel to at least one central element or gap (40, 141), and sandwiched between the additional side region (152) of an enveloping sheet (143) and the second side portion (149) of the same enveloping sheet, or sandwiched between the additional side region (152) of the enveloping sheet (143) and the second side portion (148) of an adjacent non-enveloping sheet (142).

8. The product (120) according to any one of claims 1-7, comprising an edge band (162), extending close to the second surface (124) substantially parallel to at least one central element or gap (40, 141), and sandwiched between the additional side regions (152) of two adjacent enveloping sheets (143).

9. The product (120) according to any one of claims 1-8, comprising another band (163), which extends close to the first surface (122) substantially parallel to at least one central element or gap (40, 141), and which is situated between the first lateral portions (146, 147) of two adjacent sheets (142, 143).

10. The product (20) according to any one of claims 1-9, wherein the first lateral portion (46, 47) of each sheet (42, 43) is folded predominantly in the second direction (Y) along the first surface (22), such that the first lateral portion extends along the second direction (Y) with a first inclination angle β1 in a range of 0° < β1 < 5° with respect to the first surface, and preferably in a range of 0° < β1 < 2°.

11. The product (20) according to any one of claims 1-10, wherein the second lateral portion (48, 49) of each sheet (42, 43) is folded predominantly towards the second negative direction (-Y) along the second surface (24), such that the second lateral portion extends along the second direction (Y) with a second inclination angle β2 in a range of 0° < β2 < 5° with respect to the second surface, and preferably in a range of 0° < β2 < 2°.

12. The product (20) according to any one of claims 1-11, wherein the first lateral portion (46,47) of the sheet (42,43) is folded predominantly in the second direction (Y) along the first surface (22) over a sequence of at least three adjacent central or hollow elements (40), and preferably over at least four adjacent central or hollow elements.

13. The product (20) according to any one of claims 1-12, wherein the second side portion (48, 49) of the sheet (42, 43) is folded predominantly towards the second negative direction (-Y) along the second surface (24) over a sequence of at least three opposing adjacent core elements or hollows (40, 141), and preferably over at least four opposing adjacent core elements or hollows.

14. The product (20) according to any one of claims 1-13, wherein the central elements or the hollows (40) have transverse symmetry in planes perpendicular to the first direction (X).

15. The product (20) according to any one of claims 1-14, wherein the central elements or hollows (40, 141) have polygonal cross-section shapes, preferably selected from the group of triangular, quadrilateral, pentagonal and hexagonal shapes, more preferably selected from the subgroup of regular triangular or rectangular shapes.

16. The product (20) according to any one of claims 1-15, having a concave shape with a smooth curvature in a third direction (Z) as a function along the first direction (X), the first and third directions being substantially perpendicular to the second direction (Y).

17. A reinforced composite construction, in particular a bridge, bridge deck, lock gate, turbine blade or wing, wherein the reinforced composite construction includes a product (20), for example a panel or wing profile, according to any one of claims 1-16.

18. A method for manufacturing a product (20), such as a panel, the product being defined by first and second surfaces (22, 24) on opposite sides, wherein the method comprises placing elongated core elements (40) and sheets (42) with foldable material extending along and between the core elements in a support structure (10), including: placing the core elements mutually parallel and extending predominantly along a first direction (X), and adjacent to each other in an assembly along a second direction (Y), with an outermost core element (40a) along an edge (26);interposition of a medial portion (44, 45) of a sheet between two adjacent central elements, folding of a first lateral portion (46, 47) of the sheet away from its medial portion over one of the two adjacent central elements and predominantly towards the second direction (Y) along the first surface (22); folding of a second lateral portion (48, 49) of the sheet away from its medial portion over another of the two adjacent central elements and towards a second negative direction (-Y) along the second surface (24); wherein the sheets include an enveloping sheet (43a-c) with a first lateral portion (47a-c) extending into a lateral region (50a-c) and another lateral region (52a-c), wherein the procedure further comprises: folding of the lateral region away from the first surface and around the outermost central element;folding of the additional lateral region with a non-zero component in the second negative (-Y) direction towards the second surface.; 19. The method according to claim 18, wherein the sheets include an outermost sheet (43a) with a first lateral portion (47a) extending into a lateral region (50a) and another lateral region (52a), and with a second lateral portion (49a), wherein the method comprises: folding the lateral region away from the first surface (22) and around the outermost central element (40a); folding the additional lateral region back in the second negative (-Y) direction along the second surface (24) to create at least a partial overlap with the second lateral portion (49a) of the outermost sheet.

20. The method according to claim 19, comprising: placing at least one strip (160-163) along a respective central element (40), the strip being sandwiched between: the first side portions (146,147) of two adjacent sheets (142, 143); the second side portions (148,149) of two adjacent sheets (142, 143); the additional folded side region (152) of an enveloping sheet (143) and the second side portion (149) of the same enveloping sheet; the additional folded side region (152) of the enveloping sheet (143) and the second side portion (148) of an adjacent non-enveloping sheet (142), or the additional folded side regions (152) of two adjacent enveloping sheets (143).

21. A method for manufacturing a product (120), such as a panel, comprising: providing a plurality of sheets (142, 143) of foldable material; providing an arrangement of forming elements, which extend parallel to each other along a first direction (X), and which are arranged adjacent to each other in a second direction (Y), while at the same time defining gaps between pairs of adjacent forming elements; continuously and simultaneously displacing the sheets (142, 143), predominantly in the first direction through the gaps and along the forming elements;During movement, folding of each lamina around a respective forming element to form a medial lamina portion (144, 145) between two adjacent forming elements, a first lateral lamina portion (146, 147) projecting predominantly in the second direction (Y), transversely with respect to the medial lamina portion, and a second lateral lamina portion (148, 149) projecting predominantly in a second negative direction (-Y), transversely with respect to the medial lamina portion;- causing the first lateral portions of the sheet (146, 147) of different sheets to at least partially overlap each other, and causing the second lateral portions of the sheet (148, 149) of different sheets to at least partially overlap each other, and folding a lateral region (150, 152) of at least one enveloping sheet (143) at or near the first edge of the product (126), away from a first surface (122) and surrounding an outermost forming element, and with a non-zero component in the second negative (-Y) direction returning towards a second surface (124); thereby forming a set of sheets with folded lateral sheet portions and gaps (141), wherein each gap is enclosed by a pair of adjacent medial portions (144, 145) and a pair of first and second lateral sheet portions (146-149).

22. The method according to claim 23, comprising: bending the first lateral portions of the sheet (146, 147) and the second lateral portions of the sheet (148, 149) by moving a forming element, such as a roller, in the second (±Y) and third (±Z) directions around a contour, which is defined by the forming elements and has a contour axis directed predominantly along the first (X) direction.

23. The process according to any one of claims 18-22, wherein the 5 sheets (42, 43) essentially comprise foldable fiber material, and wherein the process comprises: impregnating the sheets (42, 43) or the assembly of sheets with folded side sheet portions (46-49) with a hardening substance (64), such as a resin; causing the hardening substance to harden to form the product, thereby mutually fixing the first overlapping side portions (46, 47) and the second overlapping side portions (48, 49) of the sheets.

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