RO130118A0 - Multifunctional sandwich structures with orthotropic geometric core - Google Patents

Abstract

The invention relates to light multifunctional panels of sandwich type, which have in common the fact that their cores are made of perforated and trapezoidally profiled components, which provide increased rigidity to the panels, allow the air circulation and perform the thermal transfer inside, these panels being used in the composition of assemblies intended to be as light and cheap as possible while bearing relatively heavy loads, to be used in aeronautical engineering, in the machine, ship, tramway, car, platform construction industry and the like. According to the invention, the panels consist of some cores (3) made of the same material as the faces (1) or a material differing therefrom, have some perforated and corrugated components (4), made by drawing, which provide the reinforcement of the faces on perpendicular directions and may be made of sheet metal assembled by brazing or laser welding, or of other materials, assembled by means of structural adhesives.

Description

The invention relates to light sandwich panel structures, which share the fact that the cores are made of perforated and trapezoidal profiled components, which provide high rigidity to the assembly. The panel is considered multifunctional because it allows air circulation and heat transfer through the interior.

In the case of panels where both the core and the faces are made of sheet metal, their assembly can be done by laser welding or welding. If the core and sides are made of different materials, the sandwich panel assembly is made with structural adhesives.

The proposed solutions can be used in the various assemblies where panels are required to be as light and cheap as possible, but to withstand relatively large loads: airplanes, containers, cars, ships, trams, wagons, platforms, etc.

Similar sandwich panel structures are known. Panel construction solutions having one or more thin triangular, rectangular, trapezoidal or sinusoidal corrugated plates made of metal, plastic, impregnated textile or paper (for example, US patents 1802522, US 3321826, US 4461665, US 7041187) have been patented. B2, JP 2001-138043, WO 2005/058593). In US Patent 4461665, the core of the panel consists of two sinusoidal corrugated plates that are mounted so that the wafer directions are orthogonal. US patent 7041187 B2 proposes a technology for the manufacture of polyethylene resin panels with rectangular embossed core. With special comb-shaped tools that incorporate electrical heating resistors, the core is plasticized and striated on both sides, along the waist "backs". Similarly, complementary strips are made on one side of each face. Thus, it is possible to assemble the faces with the core by mechanical coupling of type "finger joint" or by hybrid joint, mechanical and by gluing.

There are applications in which honeycomb or foam core plates (polymeric or metallic) cannot be used because they do not allow air circulation and heat transfer through the interior. One-way transfer is possible in the case of sandwich panels with core of embossed sheet / sheet or parallel trapezoidal profiles (examples are patents GB 2465870 B, JP 2004-090241, WO 2005/058593, AU 2008228154 B2).

A number of patents have as their object the technology of manufacturing light kernels by folding sheets according to the origami technique (for example, patents EP 1346092 Bl, DE 19716637, LS 3313080, US 6 935997 B2). Thus different configurations can be obtained, the simplest being the shape of a triangular wavy plate with zigzag waffles (EP patent 1694450 Bl). = (Λ-î ο 1 L - Ο Ο 7 7 2

6 -in- aut

The object of the present invention is to achieve constructive variants of sandwich structures, light, rigid and resistant, which allow air circulation through the interior. The connections between the components are not critical in terms of ensuring the integrity of the panel because they are made on sufficiently large surfaces.

Another object of the invention consists in the development of processes for the production of cores, technologically simple, involving small manufacturing costs.

By finite element analysis we can identify the most suitable values of the thicknesses of the semi-finished products (from the same material or from different materials) so as to ensure the capable load imposed by the design theme. According to the usual standards, these analyzes are performed when loading with uniform pressure on one side, the panel being rested on the contour of the opposite side.

A first embodiment of the invention, a core panel of two perforated and embossed plates, is shown in connection with Figures 1, 2, 3, 4, 5, 6.

Fig. 1 is a general view of a panel, consisting of the following components:

- the faces of the panel, 2 - strips of outline stiffening (with holes for air circulation), 3 - the center of the panel, 4 - perforated and corrugated plates forming the core; Fig. 2 shows perforated and embossed plates (4) before assembly, Fig. 3 shows the core (3) assembled,

Fig. 4 is a top view of one of the core components,

Fig. 5 shows the specific core substructure. Finite element modeling in order to evaluate the panel behavior, in different cases of request and support, is facilitated by the fact that the core is a periodic structure that results from the joining of an appropriate number of specific substructures.

Fig. 6 graphically highlights the process of obtaining a core component (4), from thin sheet, through perforation and trapezoidal corrugation.

According to figure 6, the blank (o) from which the core components (3) are obtained is a thin sheet, wrapped as a roll. The process of processing the sheet, which advances intermittently with a convenient value of the step, begins at the stamping station of the holes where the cutting plate (6) and the punches (c) which have an alternate round-trip stroke are vertical. At another processing station, the trapezoidal corrugation is done by cold plastic deformation. The support ruler (d) and the punch ruler (s) may be the working elements of a bending press or components of a similar pneumatically operated device. The reduction of maxPmȘ ^ mȘi: 'is significant because the volume of material of the perforated plate represents only 50% -60% of that of the hole plate, with the same dimensions.

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6 -10- 2014

A second embodiment of the invention is shown in connection with FIGS. 7 and 8. FIG. 7 is an overview of the panel with the following components:

- panel faces, 2 - contour stiffening strips, 3 - trapezoidal profiles with perforations;

Fig. 8 highlights the simplicity of the technology for obtaining the core of semi-finished products in the form of strips (a), perforated (b), profiled by cold bending (c), of which 45 ° coupons (d) of the desired length are cut. Due to the fact that the profiles are parallel and arranged at 45 ° to the sides of the panel, the rigidity at. cylindrical bending for a square panel of this kind is the same, regardless of which are the two parallel sides on which the support is made.

By applying the invention, significant advantages can be obtained in comparison with similar known solutions:

The proposed sandwich panels are multifunctional, because they can take over distributed loads or pressures, but they also allow air circulation and thermal transfer through the interior; The proposed sandwich panels have low specific masses because the core is not compact and all components are made of lightweight materials;

Due to its simplicity, the manufacturing time and the costs are reduced;

it is possible the structural optimization having as objective the minimization of the specific mass of the panel (per m ² covered) by analyzes with finite elements that aim to identify the thicknesses suitable for the components, under conditions of rigidity (or load) imposed; if the structural adhesives are used for the assembly, or the assembly is hybrid (for example with pop-nets and adhesive), the components may be of different materials;

In the case of metal panels, it is possible to join the components by brazing, laser welding or spot welding.

Claims (5)

1. Sandwich panel, with a convenient ratio between stiffness and mass, characterized in that the cores (3), of the same material with the faces (1) or of a material different from them, are made of components (4) that ensure the stiffening of the faces in perpendicular directions, while allowing air circulation and heat transfer through the interior. Sandwich panel structure (Fig. 1), according to claim 1, characterized in that the core (3) is made of two perforated and corrugated plates (4) which are mounted with the waffles in perpendicular directions, and which transform the faces ( 1) in plates with constructive orthotropy. 3. Process for obtaining perforated and embossed plates. from the core composition (3), made according to claim 2, characterized in that the thin sheet (a), available in rolls, advances intermittently with a convenient value of the step, from the hole stamping station, where the plate is located. cutting (b) and the punches (c), which have an alternate vertical travel to another processing station, where the trapezoidal corrugation is performed by cold plastic deformation, with the support ruler (d) and the ruler-punch (e) ). 4. Sandwich panel structure (Fig. 7), according to claim 1, characterized in that the core is made of parallel trapezoidal profiles and disposed at 45 ° to the sides of the panel, which gives a square panel the same rigidity when cylindrical bending, whatever the two parallel sides on which the support is made. 5. Process for obtaining the profiles comprising the core (3) of the sandwich panel composition according to claim 4, simple and inexpensive, characterized in that the blanks, in the form of strips (a), are perforated (â), profiled by bending at cold (c) and cut at 45 ° in the form of coupons of the desired length (d).