IMPACT PROTECTION DEVICE

Abstract

Impact protection device comprising: a dissipative 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 chassis comprising a first frame (4) provided with first peripheral blades (41) applying under the periphery of said rear face of the panel, a peripheral reinforcement comprising a second frame (5) provided with second blades (51a) applying on the periphery of said front face of the panel, said reinforcement comprising fixing walls (52b), extending from said second peripheral blades, running along the sides of the panel and fixed to said support chassis,for which the support frame and the peripheral reinforcement are each made from profiles assembled on all four sides of the panel.

Description

Title of the invention: IMPACT PROTECTION DEVICE technical field

[0001] The invention relates to the field of impact protection devices for objects or premises. Specifically, it concerns protecting structures, pipes, or cable trays external to buildings against impacts from small projectiles such as hailstones, steel balls, or other sharp objects, or even vehicles. Such objects are particularly easily moved by strong winds, especially in the case of tornadoes. Previous technique

[0002] Protective devices already qualified against impacts from projectiles carried by tornadoes exist. These devices are of the type of nets or gratings which offer significant deflection and cover a relatively small area, but also welded grids, for example with bars of 3 cm x 6 cm cross-section, the mass of which is on the order of 140 kg per m2 for a spacing of 10 to 15 cm.

[0003] Kinetic energy dissipating materials are also used in the form of mats placed on a rigid support. These assemblies function by absorbing impacts that cause compression of the system.

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

[0005] These known solutions remain complex to implement, welded grids and gratings are heavy while nets exhibit significant deflection upon impact. Description of the invention

[0006] 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.

[0007] In light of this situation, the present disclosure proposes using aluminum foam as a protective shield against impact from a penetrating projectile. However, the protection must dissipate the impact energy in the compression of the aluminum foam, while the latter is subjected to bending stress, which is not a traditional application.

[0008] This disclosure also provides for an impact protection device comprising:

[0009] - a heat sink panel provided with at least one aluminum foam plate, of a first sheet of ductile metallic material covering one face of said aluminum foam plate to form a back face of the panel and of a second sheet of ductile metallic material covering a second face of said aluminum foam plate to form a front face of the panel,

[0010] - a support chassis comprising a first frame equipped with first blades peripherals applying below the periphery of said rear face of the panel,

[0011] - a peripheral reinforcement comprising a second frame equipped with second blades applying to 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 to said support frame,

[0012] for which the support frame and the peripheral reinforcement are each made from profiles assembled at the level of the four sides of the panel.

[0013] The choice of aluminum foam is based on the fact that aluminum foam compacts according to a threshold of force, its behavior being independent of the impact velocity. In other words, the chosen foam exhibits the same constitutive law regardless of the impact velocity.

[0014] Moreover, the mass of the panels of the present disclosure is on the order of 50 kg per m2 which is much lower than the mass of welded grids, the deflection during impacts is reduced compared to nets while the protected area is larger.

[0015] The panel of this disclosure is adapted to protect 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 exhibit a deflection much lower than that of nets upon impact and has a mass much lower than that of welded grids.

[0016] The device of the invention is designed to exploit the compression behavior of the aluminum foam, which is its preferred mode of operation, despite a load and a geometric configuration that generate a flexural behavior of the foam.

[0017] The features described in the following paragraphs correspond to embodiments that can be implemented independently of each other or in combination with each other:

[0018] According to a preferred embodiment, the second frame can be made by means of L-shaped section angles provided with first wings forming said second blades and second wings perpendicular to the first wings, forming the said fixing walls, bolted onto beams fixed to the support chassis.

[0019] The peripheral reinforcement can, according to one embodiment, be made by means of U-shaped profiles, each having a first lateral flange which rests on the periphery of the front face of the panel to form the peripheral blades of said second frame, each having a central blade which extends parallel to the sides of the panel and having a second flange extending under the periphery of the panel between the first face and the support frame.

[0020] According to a particular embodiment, the panel comprises at least two aluminum foam plates one on top of the other taken together between said sheets.

[0021] Said aluminum foam plates can be glued together.

[0022] The aluminium foam plate(s) are preferably plates with a density between 100 kg / m3 and 300 kg / m3.

[0023] The thickness of said sheets is advantageously from 1 mm to 3 mm.

[0024] The peripheral reinforcement can be made with steel plates preferably 3 mm to 6 mm thick.

[0025] The support frame is advantageously made using H-shaped profiles provided with two flanges connected by a central web and positioned under the panel.

[0026] A first base 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 base of said profiles form a third support frame of the device on one or more fixing supports.

[0027] The fixing supports can be blocks, a wall or a concrete slab for example.

[0028] The thickness of the soles can in particular be from 10 mm to 15 mm.

[0029] The panel can be of width and length between 1 m and 3 m. Brief description of the drawings

[0030] Other features, details and advantages of the invention will become apparent from the following detailed description of non-limiting embodiments and from the analysis of the accompanying drawings, in which:

[0031] [Fig-1] shows an exploded view of a protective device made according to the present disclosure ;

[0032] [Fig.2] shows the device of [Fig.1] assembled in perspective;

[0033] [Fig.3] shows a cross-sectional detail of the device in [Fig.1];

[0034] [Fig.4A], [Fig.4B] are schematic cross-sectional views of a device according to the invention respectively before impact and after impact; Description of the implementation methods

[0035] The drawings and description below contain elements that can not only serve to better understand the present invention, but also contribute to its definition, if necessary.

[0036] Reference is now made to [Fig. 1] which represents the constituent elements of an impact protection device according to the present disclosure.

[0037] This device comprises a dissipative panel provided here with two aluminum foam plates, 1a, 1b, these plates being further divided in two and assembled along perpendicular directions. The thickness of the plate(s) and the number of superimposed plates depend on the energy of the impacts against which protection is sought. Two plates can be used, in particular, when the thickness of a single plate is insufficient for the type of impact to be absorbed, but, depending on the requirements, the panels can have more or fewer than two plates depending on the desired panel thickness.

[0038] 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.

[0039] In the example of [Fig.1] the sheets are arranged on the external faces of an assembly comprising two aluminum foam plates.

[0040] The number of aluminum foam panels, 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 velocity. The aluminum foam panels can be bonded together to create a single-piece panel.

[0041] The aluminum foam plate(s) are plates with a density between 100 kg / m3 and 300 kg / m3. The thickness of said plates is from 1 mm to 3 mm for steel plates.

[0042] The device further comprises a support chassis comprising a first frame 4 provided with first peripheral blades 41 applying under the periphery of said rear face of the panel.

[0043] This support frame is made according to the example of figures 1 and 3 from H profiles 4a, 4b provided with two flanges connected by a central web 43 and positioned under the panel.

[0044] A first base of said profiles forms the first blades 41 of the first frame and supports the panel; the central web 43 of the profiles forms a support wall perpendicular to the rear face of the panel and the second base 42 of said profiles forms a third support frame of the device on one or more fixing supports 9.

[0045] The protective device further comprises a peripheral reinforcement for the panel, this reinforcement comprising a second frame 5 equipped 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 shown in particular in Figures 1 and 2. According to the example, the second frame is made by means of L-section angle brackets 5a, 5b provided with first wings forming said second blades 51 and second wings perpendicular to the first wings, forming said fixing walls 52.

[0046] According to [Fig. 3], these walls are fixed by means of bolts 6 onto beams 7 fixed to the support frame, for example under the end of the first base plate 41 by means of a weld bead 8.

[0047] 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 flanges have a thickness of 10 mm to 15 mm.

[0048] According to this disclosure, the support frame and the peripheral reinforcement are each made from profiles assembled at the level of the four sides of the panel, which allows for easy manufacturing of the device.

[0049] Due to the bracing 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 come to strike the object or structure to be protected, as shown in Figures 4A and 4B, which schematically represent in [Fig.4A] a device of the present disclosure before impact of an impactor 11 and in [Fig.4B] the device after impact.

[0050] According to these figures, the support frame 4 of the device is fixed on a floor such as a concrete floor 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.

[0051] In this latter case, the lower sheet metal 2 is observed to rise up on the edges of the panel while the center of the panel flexes under the impact. The object to be protected 10 is not touched.

[0052] Several protective devices can be made depending on the dimensions of the objects to be protected, for example the panel is of width and length between 1 m and 3 m.

[0053] The compressive constitutive law of the aluminum foam was experimentally characterized in dynamic regime, at impact velocities ranging from 5 m / s to 30 m / s. Characterization of its puncture resistance also revealed its low energy dissipation capacity during a penetrating impact. However, activation of the foam compression mechanism is possible here because the foam is held between the metal sheets and the panel rests on a sufficiently rigid structure. Furthermore, the aluminum foam compacts according to the stress threshold and exhibits behavior independent of impact velocity, with a consistent constitutive law across different impacts.

[0054] The design of the dissipative panel allows for a flexural shielding system, while dissipating kinetic energy through a compression mechanism. This results in the lowest possible net mass and operation over long spans, compatible with the protection of pipes and cable trays.

[0055] In the context of this disclosure, a material with a high capacity for dissipating kinetic energy, due to its compressive behavior, is used in a panel designed to protect sensitive installations from projectile impacts during extreme weather events. This material is an aluminum foam whose compressive behavior has been experimentally characterized under dynamic conditions, at impact velocities ranging from 5 m / s to 30 m / s. Characterization of its puncture resistance also demonstrated its low energy dissipation capacity during a penetrating impact. Furthermore, activation of the aluminum foam's compression mechanism is only possible if the foam panel(s) rest on a sufficiently rigid structure.A major technical obstacle therefore arises when the equipment to be protected must not be in contact with the protective panel, whether in normal or aggressive situations, and when the identified threat is a penetrating projectile.

[0056] As seen above, the design of the dissipating panel in this disclosure makes it possible to implement a screen system operating in bending, while dissipating kinetic energy through a compression mechanism. The constraints of the lowest possible resulting mass and operation over long spans had to be incorporated into this design.

[0057] The models were initially validated by impact tests on a reduced-scale mock-up, with a 130 kg impactor dropped from a height of 5 m, resulting in an impact velocity of 10 m / s. The test specimen was a square aluminum foam plate, with a density of 100 kg / m³ to 200 kg / m³, and more specifically 130 kg / m³ to 150 kg / m³, measuring 1 m on each side, placed between two steel plates, each 2 mm thick. This composite panel is placed on a square frame, then secured at the top edges by anti-lift stops. The aluminum foam has a density between 100 and 300 kg / m3, typically 140 kg / m3.

[0058] Calculations and tests have confirmed the suitability 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 prevented from moving out of plane so that the outer steel sheet remains attached to the foam over its entire surface.

[0059] The prototype as described, designed to provide 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, resulting in an impact velocity of 28 m / s. In the case of the tested prototype, the dissipative panel consists of two aluminum foam plates 1 sandwiched between two steel plates, each 2 mm thick. It rests linearly on its four inner edges against the chassis 4, and its spans are 2 m. The four edges of the panel are secured externally by angle brackets bolted to the sides of the chassis. 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 against impacts and the identified impact velocity.

[0060] The height of the chassis 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.

[0061] The invention is not limited to the examples described above, only by way of example, but encompasses all the variants that a person skilled in the art may consider within the framework of the protection sought, for example the panels may be square or rectangular depending on the application envisaged.

Claims

Demands

1. Impact protection device comprising: a. a dissipative panel having at least one aluminum foam plate (la, 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 dissipative panel, b. a support chassis having a first frame (4) having first peripheral blades (41) applying under the periphery of said rear face of the dissipative panel, c.a peripheral reinforcement comprising a second frame (5) equipped with second blades (51a) applied to the periphery of said front face of the heat sink panel, said reinforcement comprising fixing walls (52b), originating from said second peripheral blades, running along the sides of the heat sink panel and fixed to said support chassis, for which the support chassis and the peripheral reinforcement are each made from profiles assembled at the level of the four sides of the heat sink panel.

2. Impact protection device wherein the second frame is made by means of L-section angle brackets (5a, 5b) having first wings forming said second blades (51) and second wings perpendicular to the first wings, forming said fixing walls (52), bolted (6) onto beams (7) fixed to the support chassis.

3. Impact protection device according to claim 1 or 2 wherein the dissipative panel comprises at least two plates (la, 1b) of aluminium foam one on top of the other taken together between said plates (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 aluminium foam plate(s) are plates with a density between 100 kg / m3 and 300 kg /

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

7. Impact protection device according to any one of the preceding claims wherein the support frame is made by means of H-profiles (4a, 4b) having two flanges connected by a central web (43) and positioned under the panel such that a first flange of said profiles forms said first blades (41), that the central web (43) forms a support wall perpendicular to the rear face of the panel and that a second flange (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 of width and length between 1 m and 3 m.