Impact protection device

Abstract

Impact protection device comprising: a dissipating panel provided with at least one aluminum foam plate (1a, 1b), a first sheet (2) of a ductile metallic material covering a first face of said aluminum foam plate to form a rear face of the panel and a second sheet (3) of a ductile metallic material covering a second face of said aluminum foam plate to form a front face of the panel, a support frame comprising a first frame (4) provided with first peripheral blades (41) applied under the periphery of said rear face of the panel, a peripheral reinforcement comprising a second frame (5) provided with second blades (51a) applied on the periphery of said front face of the panel, said reinforcement comprising fixing walls (52b), originating from said second peripheral blades, running along the sides of the panel and fixed on said support frame,for which the support frame and the peripheral reinforcement are each made from profiles assembled at the four sides of the panel.,

Description

Technical field

[0001] The invention relates to the field of protection devices against impacts of objects or premises. This involves protecting structures, pipes or cable trays outside buildings against the impacts of small projectiles such as hailstones, steel balls or punching objects or even vehicles. Such objects are particularly moved by strong winds, especially in the case of tornadoes. Prior art

[0002] Protective devices already qualified for impacts from projectiles carried by tornadoes exist. These devices are of the net or grating type which have a significant deflection and cover a relatively small surface area but also welded grids for example with bars of section 3 cm x 6 cm whose mass is of the order of 140 kg per m2 approximately for a pitch of 10 to 15 cm.

[0003] Kinetic energy dissipating materials are also used in the form of mattresses placed on a rigid support. These assemblies operate on impacts causing compression of the system.

[0004] Furthermore, metal foams are already used to protect military vehicles, or high-end civilian vehicles, against the effects of shocks. Technical problem

[0005] These known solutions remain complex to implement, the welded grids and gratings are heavy while the nets present significant deflection during impacts.

[0006] In the prior art, document WO 2022 / 079286 A1 also describes an impact protection device comprising a dissipating panel and a support frame and document FR 2 305 559 A1 describes metal sheets in addition to foam plates. Statement of the invention

[0007] The invention consists of using a material with a high capacity for dissipating kinetic energy, thanks to its behavior in compression, within a panel intended to protect sensitive installations from the impacts of projectiles carried by extreme climatic phenomena.

[0008] In view of this situation, the present disclosure proposes to use an aluminum foam as a protective shield against a punching projectile impact. However, the protection must dissipate the impact energy in the compression of the aluminum foam, while the latter is stressed in bending, which is not a traditional use.

[0009] Also, this disclosure provides an impact protection device comprising: a heat sink panel provided with at least one aluminum foam plate, a first sheet of a ductile metal material covering a first face of said aluminum foam plate to form a rear face of the panel and a second sheet of a ductile metal material covering a second face of said aluminum foam plate to form a front face of the panel, a support frame comprising a first frame provided with first peripheral blades applied under the periphery of said rear face of the panel, a peripheral reinforcement comprising a second frame provided with second blades applied on the periphery of said front face of the panel, said reinforcement comprising fixing walls, originating from said second peripheral blades, running along the sides of the panel and fixed on said support frame,for which the support frame and the peripheral reinforcement are each made from profiles assembled at the four sides of the panel.

[0010] The choice of aluminum foam is based on the fact that aluminum foam compacts according to a stress threshold, its behavior being independent of the impact speed. In other words, the chosen foam exhibits the same behavior law regardless of the impact speed.

[0011] Furthermore, the mass of the panels of the present disclosure is of the order of 50 kg per m 2 < which is much lower than the mass of the welded grids, the deflection during impacts is reduced compared to the nets while the protected surface is larger.

[0012] The panel of the present disclosure is suitable for protecting a device located behind the rear face of the panel from impacts of projectiles carried by strong winds, particularly during tornadoes and hurricanes. The device is designed to have a deflection much less than that of nets during an impact and has a mass much less than that of welded grids.

[0013] The device of the invention is designed to exploit the compression behavior of the aluminum foam, which is the preferred working mode, despite a loading and a geometric configuration which generate a bending behavior of the foam.

[0014] The characteristics set out in the following paragraphs correspond to embodiments which can be implemented independently of one another or in combination with one another: According to a preferred embodiment, the second frame can be produced by means of L-shaped section angles provided with first wings forming said second blades and second wings perpendicular to the first wings, forming said fixing walls, bolted onto beams fixed to the support frame.

[0015] The peripheral reinforcement may, according to one embodiment, be produced by means of U-shaped profiles, each provided with a first lateral wing which rests on the periphery of the front face of the panel to form the peripheral blades of said second frame, each provided with a central blade which extends parallel to the sides of the panel and provided with a second wing extending under the periphery of the panel between the first face and the support frame.

[0016] According to a particular embodiment, the panel comprises at least two plates of aluminum foam, one on top of the other, taken together between said sheets.

[0017] The said aluminum foam plates can be glued together.

[0018] The aluminum foam plate(s) are preferably plates with a density between 100 kg / m 3 and 300 kg / m 3.

[0019] The thickness of said sheets is advantageously 1 mm to 3 mm.

[0020] The peripheral reinforcement can be made with steel plates preferably 3 mm to 6 mm thick.

[0021] The support frame is advantageously made using H-shaped profiles provided with two soles connected by a central core and positioned under the panel.

[0022] A first sole of said profiles can in particular form said first blades, the central core form a support wall perpendicular to the rear face of the panel and a second sole of said profiles form a third support frame of the device on one or more fixing supports.

[0023] The fixing supports can be studs, a wall or a concrete slab for example.

[0024] The thickness of the soles can be from 10 mm to 15 mm.

[0025] The panel can be between 1 m and 3 m wide and long. Brief description of the drawings

[0026] Other characteristics, details and advantages of the invention will appear on reading the detailed description below of non-limiting exemplary embodiments, and on analyzing the appended drawings, in which: [ Fig. 1 ] shows an exploded view of a protective device made according to the present disclosure; [ Fig. 2 ] shows the device of the figure 1 assembled in perspective; [ Fig. 3 ] shows a cross-sectional detail of the device of the figure 1 ; [ Fig. 4A], [Fig. 4B ] are schematic sectional views of a device according to the invention respectively before impact and after impact; Description of the embodiments

[0027] The following drawings and description contain elements which may not only serve to better understand the present invention, but also contribute to its definition, where appropriate.

[0028] Reference is now made to the figure 1which represents the constituent elements of an impact protection device according to the present disclosure.

[0029] This device comprises a dissipating panel provided here with two plates 1a, 1b of aluminum foam, these plates being furthermore here divided into two and assembled in perpendicular directions. The thickness of the plate(s) and the number of superimposed plates depends on the energy of the impacts against which it is desired to protect. Two plates can in particular be used when the thickness of a single plate is not sufficient in relation to the type of impact to be absorbed but, depending on the needs, the panels can comprise more or less than two plates depending on the desired thickness for the panel.

[0030] The panel comprises, on a first side of the aluminum foam plate(s), a first sheet 2 of a ductile metallic material, in particular steel or aluminum, covering a first face of said aluminum foam plate or of the assembly of aluminum foam plates to form a rear face of the panel. The panel comprises a second sheet 3 of a ductile metallic material covering a second face of said aluminum foam plate or of the assembly of aluminum foam plates to form a front face of the panel.

[0031] In the example of the figure 1 the sheets are arranged on the external faces of an assembly comprising two aluminum foam plates.

[0032] The number of aluminum foam plates, the thickness of the metal sheets and the spans can vary depending on the configuration of the targets to be protected from impacts and the identified impact speed. The aluminum foam plates can be glued together to create a single-piece panel.

[0033] The aluminum foam plate(s) are plates with a density between 100 kg / m 3 and 300 kg / m 3. The thickness of said sheets is 1 mm to 3 mm for steel sheets.

[0034] The device further comprises a support frame comprising a first frame 4 provided with first peripheral blades 41 applied under the periphery of said rear face of the panel.

[0035] This support frame is made according to the example of figures 1 And 3 from H-shaped profiles 4a, 4b provided with two flanges connected by a central core 43 and positioned under the panel.

[0036] A first sole of said profiles forms the first blades 41 of the first frame and supports the panel, the central core 43 of the profiles forms a support wall perpendicular to the rear face of the panel and the second sole 42 of said profiles forms a third support frame of the device on one or more fixing supports 9.

[0037] The protection device further comprises a peripheral reinforcement for the panel, this reinforcement comprising a second frame 5 provided with second blades 51a applied to the periphery of said front face of the panel and fixing walls 52b, at 90° to said second peripheral blades, running along the sides of the panel and fixed to said support frame as notably shown in figures 1 And 2. According to the example, the second frame is produced by means of angles 5a, 5b of L-shaped section provided with first wings forming said second blades 51 and second wings perpendicular to the first wings, forming said fixing walls 52.

[0038] According to the figure 3 , these walls are fixed by means of bolts 6 on beams 7 fixed to the support frame, for example under the end of the first sole 41 by means of a weld bead 8.

[0039] The peripheral reinforcement is made with steel plates with a thickness of 3 mm to 6 mm while the support frame is made with a profile whose soles have a thickness of 10 mm to 15 mm.

[0040] According to the present disclosure, the support frame and the peripheral reinforcement are each made from profiles assembled at the four sides of the panel, which allows easy manufacture of the device.

[0041] Due to the clamping of the edges of the sheets between the peripheral reinforcement and the support frame, the foam undergoes compression from top to bottom in the middle and from bottom to top on the sides, which allows good absorption of impacts and reduced shrinkage of the panel which does not hit the object or structure to be protected as shown in Figures 4A and 4B which schematically represent in Figure 4A a device of the present disclosure before impact of an impactor 11 and in Figure 4B the device after impact.

[0042] According to these figures, the support frame 4 of the device is fixed on a ground such as a concrete ground forming a support 9 and an object to be protected 10 is positioned under the panel comprising the aluminum foam 1 and two steel sheets 2, 3.

[0043] In the latter case, there is a rise of the lower sheet 2 on the edges of the panel while the center of the panel flexes under the impact. The object to be protected 10 is not affected.

[0044] Several protection devices can be made depending on the dimensions of the objects to be protected, for example the panel is between 1 m and 3 m wide and long.

[0045] The compressive behavior law of the aluminum foam was experimentally characterized in dynamic mode, at impact speeds ranging from 5 m / s to 30 m / s. The characterization of its behavior in the face of punching also showed its low energy dissipation capacity during a perforating impact. However, the activation of the foam compression mechanism is possible here because the foam is held between the sheets and the fact that the panel rests on a sufficiently rigid structure. In addition, the aluminum foam compacts according to the stress threshold and has a behavior independent of the impact speed and the same behavior law according to the impacts.

[0046] The design of the dissipating panel allows for a screen system that works in flexion, while dissipating kinetic energy through a compression mechanism. This allows for the lowest possible resulting mass and operation over long spans, compatible with the protection of pipes and cable trays.

[0047] In the context of the present disclosure, a material with a high capacity for dissipating kinetic energy is used, thanks to its behavior in compression, within a panel intended to protect sensitive installations from the impacts of projectiles carried by extreme climatic phenomena. This material is an aluminum foam provided with a law of behavior in compression which has been experimentally characterized in dynamic regime, at impact speeds ranging from 5 m / s to 30 m / s. The characterization of its behavior in the face of punching has also shown its low capacity for dissipating energy during a perforating impact. Activation of the compression mechanism of the aluminum foam is also only possible if the foam plate or plates rest on a sufficiently rigid structure.A major technical barrier therefore appears when the equipment to be protected must not be in contact with the protection panel, whether in a normal situation or in an attack situation, and when the identified threat is a piercing projectile.

[0048] As seen above, the design of the dissipating panel of the present disclosure makes it possible to produce a screen system working in flexion, while dissipating kinetic energy by a compression mechanism. The constraints of the lowest possible resulting mass and operation over large spans were to be integrated into this design.

[0049] The models were initially validated on punching impact tests on a reduced-scale model, with an impactor of mass 130 kg falling from a height of 5 m, leading to an impact speed of 10m / s. The test body was a plate of aluminum foam, with a density of 100 kg / m 3< to 200 kg / m 3< and more precisely 130 kg / m 3< to 150 kg / m 3< , square with sides of 1 m, placed between two steel plates each 2 mm thick. This composite panel is placed on a square frame, then clamped on the upper edges by anti-theft stops. The aluminum foam has a density between 100 and 300 kg / m 3< , typically 140 kg / m 3< .

[0050] Calculations and tests confirmed the relevance of the device in that the composite panel is, on the one hand, supported on its 4 inner edges, and on the other hand that the 4 outer edges are blocked in out-of-plane movement so that the outer steel sheet remains integral with the foam over its entire surface.

[0051] The prototype as described, thus produced to ensure protection against a projectile carried by a tornado, was tested and validated by drop tests of a 130 kg steel tube from a height of 40 m, leading to an impact speed of 28 m / s. In the case of the prototype tested, the dissipating panel consists of two aluminum foam plates 1 sandwiched between two steel plates each 2 mm thick. It is supported linearly on its four inner edges on the frame 4, and its spans are 2 m. The blocking of the four edges of the panel from the outside is ensured by the angles bolted to the sides of the frame. The number of foam plates, the thicknesses of the steel plates and the spans can vary depending on the configuration of the targets to be protected from impacts and the identified impact speed.

[0052] The height of the frame is calibrated so that the deflection of the panel under such an impact does not allow the panel to strike a device under the panel.

[0053] The invention is not limited to the examples described above, only by way of example, but it encompasses all the variants that a person skilled in the art may envisage within the framework of the protection sought, for example the panels may be square or rectangular depending on the application envisaged.

Claims

1. Impact protection device comprising: a. a dissipating panel provided with at least one aluminum foam plate (1a, 1b), a first sheet (2) of a ductile metallic material covering a first face of said aluminum foam plate to form a rear face of the panel and a second sheet (3) of a ductile metallic material covering a second face of said aluminum foam plate to form a front face of the dissipating panel, b. a support frame comprising a first frame (4) provided with first peripheral blades (41) applied under the periphery of said rear face of the dissipating panel, c.a peripheral reinforcement comprising a second frame (5) provided with second blades (51a) applied to the periphery of said front face of the dissipating panel, said reinforcement comprising fixing walls (52b), originating from said second peripheral blades, running along the sides of the dissipating panel and fixed to said support frame, for which the support frame and the peripheral reinforcement are each made from profiles assembled at the four sides of the dissipating panel.

2. Impact protection device for which the second frame is produced by means of angle irons (5a, 5b) of L-shaped section provided with first wings forming said second blades (51) and second wings perpendicular to the first wings, forming said fixing walls (52), bolted (6) on beams (7) fixed to the support frame.

3. Impact protection device according to claim 1 or 2, for which the dissipating panel comprises at least two plates (1a, 1b) of aluminum foam, one on top of the other, taken together between said sheets (2, 3).

4. Impact protection device according to claim 3 wherein said aluminum foam plates are glued together.

5. Impact protection device according to any one of the preceding claims, wherein the aluminum foam plate(s) are plates with a density between 100 kg / m 3 and 300 kg / m 3 .

6. Impact protection device according to any one of the preceding claims, for which the thickness of said sheets is from 1 mm to 3 mm, the peripheral reinforcement being made with steel plates with a thickness of from 3 mm to 6 mm.

7. Impact protection device according to any one of the preceding claims, for which the support frame is produced by means of H-shaped profiles (4a, 4b) provided with two soles connected by a central core (43) and positioned under the panel so that a first sole of said profiles forms said first blades (41), that the central core (43) forms a support wall perpendicular to the rear face of the panel and that a second sole (42) of said profiles forms a third support frame of the device on one or more fixing supports (9).

8. Impact protection device according to claim 7 wherein the thickness of the soles is 10 mm to 15 mm.

9. Impact protection device according to any one of the preceding claims, wherein the panel is between 1 m and 3 m wide and long.

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