EP4065923A1

EP4065923A1 - Device for protecting static or mobile land, sea or overhead structures against the blast from an explosion or detonation and associated projections of material

Info

Publication number: EP4065923A1
Application number: EP20807066.4A
Authority: EP
Inventors: Francis COLLOMBET; Yves-Henri GRUNEVALD; Alain ROUQUAND
Original assignee: Commissariat a lEnergie Atomique CEA; Universite Toulouse III Paul Sabatier; Composites Expertice and Solutions SARL CES; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Universite Toulouse III Paul Sabatier; Composites Expertice and Solutions SARL CES; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2019-11-27
Filing date: 2020-11-19
Publication date: 2022-10-05
Also published as: FR3103548B1; FR3103548A1; US20220404124A1; US12078457B2; WO2021104998A1

Abstract

The present invention relates to a device (2) for protecting a mobile or static structure against the blast from an explosion or detonation and associated projections of material, comprising a protective casing (21) made of a plurality of materials, wherein the protective casing (21) is situated at a distance from the structure to be protected and connected to the structure by elastomer connecting means, the protective casing (21) being resiliently deformable such that it can deform resiliently for the duration of the period of stress by oscillating in order to spread the energy of the explosion blast in a plurality of directions over its surface and over time, and then to return fully or in part to its original shape after a period of time has elapsed.

Description

Title of the invention: Device for protecting static or mobile, land, nautical or aerial structures against the blast of an explosion or detonation and the associated projections of matter Field of the invention

The technical field of the invention is that of protection devices for static or mobile structures, land, nautical or air, against explosions or detonations and associated material projections, such as explosions from buried mines for example.

More particularly, the present invention relates to devices for ensuring the protection of any physical body in contact or not with a floor of a land vehicle, these devices being arranged between the floor of a land vehicle and a machine explosive.

[0003] Such protection devices can also ensure the protection of a vertical face of the structure and in these cases constitute lateral protection. Finally, they can be placed on the upper face (for example a roof) in the event of a threat resulting from a detonation located above the system to be protected (for example an aerial detonation).

Prior art

[0004] By way of illustration, in the case of armed conflicts, military land vehicles, such as armored vehicles, are threatened by explosive devices, such as mines, designed to cause damage to the military land vehicle and to its occupants due in particular to the blast caused by the detonation of explosive devices and fragments and more generally to all the associated projections.

More specifically, the detonation of a mine located below a military land vehicle generates blast-type shock waves which can cause perforation of the floor of the military land vehicle directly exposing the occupants of the military land vehicle to the pressure of the blast and the intense heat generated by the explosion as well as the associated projections.

To protect the passengers of a military land vehicle from death or serious injury that they could suffer when their vehicle is subjected to a mine explosion, it is known to protect the floor of the land vehicle by placing under that -Here shielding or overprotection.

This overprotection can consist of a metal shell placed between the threat (placed on or buried in the ground) and the floor of the military land vehicle, at a distance from the latter, the shell making it possible to partially absorb the energy produced by the blast of the mine explosion.

[0008] One embodiment of this overprotection is described in American patent US Pat. No. 8,640,594.

[0009] The shell allows, in some cases but not always, to partially absorb the energy produced by the blast of the mine explosion through the principle of plastic deformation, for example.

However, this solution has a particular drawback. Indeed, the over protection is made of metal. This results in a large mass for overprotection which penalizes the mobility of the vehicle.

[0011] The overprotection can be used to deflect the blast of the explosion and can in this case have a cross-sectional profile having the general shape of a V, the top of the V pointing in a direction oriented towards the blast of the 'explosion.

[0012] One embodiment of this type of overprotection is described in American patent US 2007/0186762. However, this solution also presents in particular certain drawbacks. Indeed, it does not promote the significant absorption of energy, for example by plastic deformation, because its geometry gives it additional rigidity (principle of triangulation in mechanics). It is the same for the elastic deformation. To integrate such a V-shaped overprotection under the vehicle while keeping the same ground clearance, the total height of the vehicle must most often be increased. Such a V-profile favors a concentration of stresses at the level of the edge of the V which must, consequently, be reinforced. Finally, the stress is impulsive and can be broken down into two parts, a first part consisting of a shock wave resulting, for example in the case of a buried mine, from the arrival at super sonic speeds of a densified fluid consisting of by ejecta and projections (duration of a few tens of microseconds and pressure peak of several hundred bars). A second part consists of an overpressure wave resulting from the expansion of the gases at very high temperatures generated by the detonation (duration of a few hundred mi croseconds and a pressure peak of several tens of bars). The first part being purely impulsive, the shock wave is transmitted to the overprotection and therefore to the system to be protected before the flow is diverted. The form therefore intervenes only in the second part of the solicitation and, in all cases, quite reduced.

[0013] The overprotection is conventionally fixed to the vehicle by a set of mechanical connecting parts, such as deformable blocks, articulated panels, jacks, rods and / or ball joints, partly ensuring the absorption of the energy produced by the blast of the mine explosion. This set of parts is however subject to malfunctions, such as alignment problems, and stresses, such as corrosion. Moreover, this set of parts does not prevent the transmission of a significant part of the shock wave of the military land vehicle and particularly to the floor.

The object of the invention is to provide a protection device making it possible to overcome such drawbacks.

Disclosure of the invention

The invention relates to a device for protecting a mobile or static structure against the blast of an explosion or detonation and the associated projections of material, comprising a protective shell made of several materials, said shell being located at a distance from the structure to be protected and connected to said structure by elastomeric connecting means, said protective shell being elastically deformable so as to be able to deform elastically over the duration of the stress by oscillating to spread over its surface and in time the blast energy of the explosion in several directions, then fully or partially returning to its original form after a lapse of time.

[0016] This period of time is of the order of a few tens of milliseconds.

By partial return to its original shape is meant the fact that the protective shell is liable to undergo irreversible deformation.

To connect the protective shell to the mobile or static structure, which can be a military land vehicle, there are proposed connecting elements, for example in the form of a rod, made of elastomer, for example of silicone. These connecting elements to the torize the rotation and translation of the protective shell in all directions. The elastomer constituting the connecting elements undergoes an elastic deformation able to adapt at any time to the geometry and the position of the overprotection. Due to its low stiffness, it also constitutes an additional delay filter, the shock wave traveling through a material at a speed proportional to the stiffness of said material (so here about 3 times slower than in overprotection). The solution of the invention avoids the use of a link mechanism liable to malfunction (no corrosion, no seizing, no problem of precise alignment,

...). Finally, the system being easily removable in the event of aging for any reason, the elastomeric connecting element (s) concerned can be changed simply. In other words, no loss of performance is possible with the solution of the invention.

The main technical function of the protection device is to cause a delay effect and to diffuse as widely as possible, in space and time, the stress generated by the explosion towards the structure to be protected by choosing the most suitable entry path.

It also aims to store a significant amount of elastic energy allowing it, after a certain time, about 2 to 3 times the duration of the solicitation, that is to say approximately 1 to 2 milliseconds (for the record at that moment, the solicitation has been completely terminated for several hundred milliseconds), to generate a significant force in the direction opposite to the solicitation. This force can be used to cause the separation, for example through devices with a calibrated breaking level (for example a shear pin), of the overprotection of the system to be protected and thereby prevent any future dynamic interaction between the overprotection and the system to protect

When the mine explodes, initially, the stress is concentrated on a small area of the protective shell (the area of action of the first part of the stress) but its mechanical properties (average rigidity of a few tens of gigapascals) already allow it to have a local elastic deformation. This elastic deformation is globalized under the effect of time and of the second part of the stress. During all this time, the protection device will promote the distribution of all the stress over the entire surface of the protective shell by creating a first delay filter favored by a lower inertia compared to that of the structure to be protected .

[0022] There is no absorption of the stress of the explosion but a distribution of the effects of the stress on and within the overprotection up to the zones of interaction between the overprotection and the system to be protected.

[0023] The intrinsic structure of the protective device makes it possible to collect the stress, then to diffuse the effects within the protective shell. In other words, overprotection "deconcentrates" the solicitation (that is, "decreases the focus") and spread it out in time and space.

[0024] This diffusion takes place in a multimodal manner: the protective shell deforms elastically in a reversible manner by vibrating to propagate the shock wave in several directions. To facilitate this effect, the protective shell is made of one or more materials with a Young's modulus that is lower by a factor of 10 compared to prior art materials.

The multidirectional elastic deformation of the protective shell makes it possible to slow down the speed of propagation of these shock waves and improves their distribution in a much longer time than that necessary for the ejecta to have time to leave the area where they are could present a danger to the protected structure, its occupants and its contents.

For example, during tests carried out by the inventors, the aggregates were ejected over a period of between 0.2 ps and 100 ps after the explosion while the protective structure vibrated for several milliseconds (i.e. approximately 30 times more).

The elastomeric connecting elements have the remarkable feature of slowing the transmission of the shock wave to the structure to be protected and its constituents, by example the floor of a vehicle. There are therefore internal reflections of the shock wave at the very heart of the overprotection: the device of the invention thus functions as a mechanism for imprisoning the shock wave. The transmission of the shock wave to the connecting elements therefore takes place with a delay and by small amounts of energy spread over time. The elastomeric connecting elements induce a new delay which is added to the previous one. Unlike the devices of the prior art, the connecting elements only weakly transmit the echo of the shock wave to the vehicle floor.

The effectiveness of the technical protection function is essentially due to its ability to be able to be elastically deformed while allowing a return of the waves which will make the protective shell vibrate: during the oscillations of the protective shell, the floor vehicle does not "see" anything in the sense that it is not impacted by shock waves. These vibrations of the protective shell will filter the input signal, typically attenuating it by a factor of 5 to 20.

[0029] The invention operates without an energy dissipation mechanism. However, the protection device may additionally include a damping mechanism.

According to a particular approach, said shell has constituent materials whose Young's moduli are between 1000 and 200000 MPa in quasi-static.

[0031] According to a particular embodiment of the invention, said protective shell consists of a multilayer structure.

[0032] Advantageously, said protective shell comprises a first protective layer composed of several materials against the projections of materials and ejecta associated with said explosion, said first layer being intended to be oriented on the blast side of the explosion.

Advantageously, said protective shell comprises at least a first layer of material having a Young's modulus of between 1000 and 10,000 MPa, a first face oriented towards the structure to be protected, of which is covered by at least one structural layer and the second opposite face of which is covered by at least one other structural layer.

Advantageously, said structural layers are made of glass, basalt, aramid or carbon fibers.

[0035] According to a particular embodiment of the invention, the ends of at least part of the layers of material of said protective shell are curved.

According to a particular embodiment of the invention, the protective shell is of curved shape and is located at a distance from the part of the military land vehicle to be protected, said protective shell having a predefined radius of curvature when none stress is applied to it and being able to vibrate under the effect of blast of an explosion so as to have radii of curvature different from the initial radius of curvature, then to return completely or partially to its original shape once the blast of the explosion has dissipated.

The convex curved shape of the floor protection shell allows movement in the direction of the stress but also in other directions (for example horizontal in the case of a military land vehicle) to spread over time and in space the energy of the blast of the explosion at the structural scale and to transfer the forces to the rigid areas of the sides of the military land vehicle (side faces for a low tonnage armored vehicle (BFT), uprights for a light vehicle, such as a light reconnaissance and support vehicle (VLRA) or a special patrol vehicle (VPS)) via the elastomer connection means.

The arcuate curved shape of the protective shell promotes the lateral flow of the blast from the explosion. The geometric continuity of an arched structure makes it possible to obtain a progressive distribution of stresses.

[0039] Furthermore, this arched shape makes it possible to improve the ground clearance of the military land vehicle compared to V solutions.

In an alternative embodiment, the protective shell has an initial flat shape and an evolving curved geometry during stress. The protective shell may however have curved edges while being flat.

The protective shell is a combination of superimposed layers of composite material arranged according to a defined architecture, capable of withstanding the forces generated by the explosion of a given mine (for example an 8 kg NATO mine).

[0042] The composites, by their performance and their lightness, offer optimal protection capacities without penalizing the total mass of the military land vehicle, and therefore its mobility.

The diffusion of the forces of the explosion and the deflection of the mine shards on the sides of the military land vehicle make it possible to minimize the damage caused to the military land vehicle. Much of the charge from the blast is diffused into the protective structure of the military land vehicle in a relatively uniform manner. As a result of this device, the accelerations transmitted to the floor of the military land vehicle are significantly reduced (a factor of 5 to more than 20), which further reduces the risk of major trauma. Thus, the survivability of the crews is greatly improved.

Advantageously, the elastomeric connecting means are made of silicones, synthetic or natural rubber and the overprotection is only maintained in support on these elastomeric supports.

Advantageously, said shell is held on the elastomeric connecting means by means of removable devices and possibly to calibrated breaking level.

[0046] Thus, said overprotection is easily removable from said structure to be protected and from said elastomeric supports.

Advantageously, the means for maintaining said overprotection can be cut automatically beyond a certain level of stress as soon as the overprotection releases the elastic energy stored during said stress, or once the stress has ended .

Advantageously, the elastomeric connecting means are continuous or spaced supports extending around the periphery of the shell.

According to a particular aspect of the invention, the connecting elements are in the form of a beam or juxtaposed blocks which are of square or rec tangular section, for example.

[0050] According to a particular but non-limiting embodiment, the invention applies to the protection of a part of a military land vehicle.

The invention also provides a device for protecting part of a land, nautical (such as a boat or submarine), or aerial military vehicle against damage associated with detrimental events, such as explosions of mines or other explosive devices.

The protection device can be used to protect a military land vehicle against the blast of an explosion, with projection of materials or not, occurring below the military land vehicle. In this case, it is placed under the floor of the military land vehicle so as to protect the occupant or occupants of the military land vehicle while avoiding, in the particular case of this implementation, vertical movements of the floor, source major trauma for the occupants (in particular to the lower limbs).

In the case of a vertical structure to be protected, it is understood that the protection device prevents horizontal movements of said vertical structure.

Presentation of figures

[0054] Other characteristics and advantages of the invention will become apparent on reading the following description, given by way of indicative and non-limiting example, and the accompanying drawings, in which:

[0055] [fig.l] Figure 1 is a schematic representation of an embodiment of the protection device according to the invention;

[0056] [fig-2] Figure 2 is an exploded schematic representation of an embodiment of the protection device according to the invention;

[0057] [fig-3] FIG. 3 is a schematic representation in section of an embodiment lisation of the protection device according to the invention;

[0058] [fig-4] Figure 4 is a partial schematic representation of a vehicle equipped with a protection device according to the invention;

[0059] [fig-5] FIG. 5 is a detailed lateral schematic representation in section of elastomeric connecting means connecting a protection device according to the invention to a land vehicle;

[0060] [fig-6] Figure 6 is a schematic sectional view illustrating the different layers of the protective shell of the protective device according to an exemplary embodiment;

[0061] [Fig.7] Figure 7 shows schematically a first example of connecting and fixing elements of a protective device to a vehicle;

[0062] [Fig.8] Figure 8 shows schematically a second example of connecting and fixing elements of a protective device to a vehicle;

[0063] [fig-9] Figure 9 shows schematically a third example of connecting and fixing elements of a protective device to a vehicle;

[0064] [Fig.10] Figure 10 shows schematically a fourth example of connecting and fixing elements of a protective device to a vehicle;

[0065] [fig.l 1] Figure 11 shows schematically a fifth example of connecting and fixing elements of a protective device to a vehicle;

[0066] [Fig.12] Figure 12 shows schematically a sixth example of connecting and fixing elements of a protective device to a vehicle;

[0067] [fig.13 A] FIG. 13A is a lateral schematic representation of an unedged protective shell under the effect of the shock wave caused by the blast of the explosion of a mine buried in the ground;

[0068] [fig.l3B]: FIG. 13B is a lateral schematic representation of a protective shell having anti-delamination border zones under the effect of the shock wave caused by the blast of the explosion of 'a mine buried in the ground

[0069] [Fig.14] Figure 14 is a detailed lateral schematic representation of a first edging solution of a protective shell according to the invention;

[0070] [Fig.15] Figure 15 is a detailed lateral schematic representation of a second edging solution of a protective shell according to the invention;

[0071] [Fig.16] Figure 16 is a schematic perspective view of detail of a third edging solution of a protective shell according to the invention;

[0072] [Fig.17] Figure 17 schematically illustrates an example of non-structural layers of protection of a protective shell according to the invention, incorporating metal or ceramic tiles intended to improve puncture resistance ;

[0073] [fig.18]: Figure 18 is a lateral schematic representation of detail in section of an embodiment of the maintenance of the connecting elements on either side of a protective shell according to the invention by reversible fixing means. Detailed description of the invention

[0074] Note that the invention is presented for application to a military land vehicle. However, the invention is equally suitable for nautical (boats or submarines), military, civilian and commercial air or land vehicles (such as transport vehicles on wheels or tracks). It is also suitable for any static system, for example a side face or a roof of a building serving as a shelter (more commonly known as a "shelter" in the military field) or a protective wall.

Figures 1 to 3 show a protection device 2 against mines according to one embodiment of the invention.

FIG. 4 partially shows a vehicle 1 equipped with a protection device 2 against mines. The illustrated vehicle 1 is a wheeled military land vehicle provided with a chassis, a bodywork and a floor 11.

A blast mine placed on the ground S generates during its initiation a strong pressure on the floor 11 of the vehicle. According to the invention, to allow the floor 11 to withstand the effects of the blast, there is provided a protection device 2 making it possible to protect the floor 11 of the vehicle 1 above which the crew compartment is located.

In this particular case, the protection device 2 aims to protect the physical bodies (people, equipment, etc.) located above the floor 11. Indeed, it is tolerated that the floor 11 may be subjected to irreversible deformations. On the other hand, the bodies located on the floor 11 must not suffer damage or reduced damage. The protection must be so effective that no flames or particles penetrate into the interior of the vehicle 1.

This protection device 2 is in the form of a so-called over-protection shell 21, of curved shape in this example, located under the vehicle, between the floor 11 and the floor S. The shell 21 has a radius of predetermined curvature when no stress is applied to it.

It can, in a variant, be flat, have a variable radius of curvature, with or without curved edges.

The shell 21 is fixed to the vehicle 1 by means of connecting elements 22a, 22b, 23a, 23b which are deformable at each of its lateral ends. The shell 21 extends over the entire width and length of the floor 11.

In Figures 4 and 5, the shell 21 is shown partially and only the connecting elements 22a, 23a located at a lateral end of the shell 21 are illustrated. However, it will be understood that the connecting elements 22b, 23b are also provided at the level of the other lateral end of the shell 21 as shown in the figures. figures 1 to 3.

The goal sought by the implementation of the protection device 2 is to diffuse the effect of the blast of the explosion (parts one and two of the stress) as widely as possible, in space and time allowing an elastic deformation thereof. The curved shape favors the deflection of the breath but is not the primary goal; the curved shape having the main purpose of adjusting the flexibility of the overprotection without increasing its mass. To do this, there is displacement of the shell 21 both in the direction of the stress but also in other directions, without impact on the floor 11, and transfer of the energy of the explosion to the elements of longitudinal link 22a, 22b, 23a, 23b. The shell 21 is elastically deformed by vibrating and propagates the shock wave in several directions within it. The deformable connecting elements 22a, 22b, 23a, 23b also absorb part of the impact energy and return the wave to the shell 21.

The protection device 2 thus acts as a device which reduces the violence of the impact and the destructive effects on the cabin of the vehicle 1.

The shell 21 is able to oscillate under the effect of the blast of an explosion and then automatically resume its shape once the blast of the explosion has dissipated.

This protection device 2 constitutes a structural filter for protection against the blast of the explosion, with or without projection of materials. It is configured to reduce the effects of the detonation of an explosive device located in the ground (underground mine) or on the ground, such detonation being generally short and intense.

This protection device 2 acts as a filter to reduce the input signal, formed by the blast of the explosion, and reduce the accelerations transmitted to the protected object, the floor 11 in the example illustrated, this which prevents any physical body placed in the example on floor 11 from suffering serious damage. The tructor's breath provides a brief and intense "input signal", the slow movement of the protected structure constituting the "output response".

The protection device 2 of the floor 11 of the vehicle 1 comprises two main elements:

A composite shell 21, in the form of an arc in the example of Figures 1 and 2, located at a distance from the object to be protected (the floor 11 of the vehicle 1 in this case), and

[0090] connecting elements, taking the form of beams or struts, 22a, 22b, 23a, 23b made of elastomer, such as silicone in this example, which are integral with fixing or fastening elements 24a, 24b, 25a, 25b of the shell 21 to the vehicle 1, in the example of Figures 1 and 2.

The beams 22a, 22b, 23a, 23b allow the arched shell 21 to deploy in the elastic range.

The shell 21, which is made of composite material (fiberglass and plywood, by example), is light and flexible, in the sense that it is deformable in the elastic range under the range of stresses for which it is designed. Advantageously, the shell has a Young's modulus or overall elasticity of between 1 GPa and 200 GPa.

In the example of Figures 1 to 5, the shell 21 is of convex shape oriented towards the ground S and is located at a distance from the floor 11. It is curved outwardly in the transverse direction of the vehicle 1 and is composed of a single multi-layered piece.

This arched part can be deployed, or be stretched, and is capable of undergoing a controlled deformation under the effect of the force of an explosion, possibly of deflecting the blast (but this is not essential ) and automatically return to shape once the force has dissipated.

The shell 21 helps to attenuate, or even absorb and deflect the force of the blast, that is to say the shock waves.

The shell 21 can be deformed without coming into contact with the floor 11 and therefore without impacting the latter.

According to a particular implementation, the composite shell 21 is a light sandwich structure consisting of a compact stack of several layers, including one or more structural layers of glass fibers and matrix, for example epoxy, arranged on either side. another of at least one structural layer of plywood or of a material having specific properties (density, Young's modulus, compressive strength of the same order of magnitude) and a non-structural layer of protection against aggregates intended to be oriented towards the load side (figure 6).

In the example of Figure 6, the shell 21 is a composite structure composed of several layers of different materials:

A non-structural layer 211 for protection against aggregates: this layer, intended to be oriented on the side of the stress, can be destroyed without this adversely affecting performance;

[0100] structural layers 212, 214 (structural because multi-material assembly responding to mechanical properties). The strength to stiffness ratio of the materials in these layers is adapted to the target to be protected. Examples: glass fibers or carbon fibers;

[0101] a structural layer 213 of plywood, called a core (structural because it consists of several sheets of wood veneer glued to each other by crossing the direction of the grain of the wood).

The outer layer or layers 211 of fiberglass (exposed to the blast, and therefore oriented towards the side of the stress) have the function of protecting the floor 11 against flames and projections of materials (aggregates) thanks to their large size. resistance to physical and thermal shocks. This or these outer layers of centimetric thickness serve as an initial barrier and aim to prevent or limit the penetration of the aggregates projected by the blast, in order to sufficiently reduce the risk of damage to the following layers 212 (external structural skin) and 213 (core of the hull).

[0103] The number of layers is variable and is closely linked to the type of stress on the face and the scope of the application. For example, a prototype developed and tested by the inventors comprises 55 layers of fiberglass. Depending on the thickness allowed, the number of layers can be up to 240 or even more.

[0104] The thickness of each of the layers of glass fibers 212, 214 and plywood 213 may be greater or less depending on the design requirements, that is to say with regard to the maximum level of threat considered.

The core material, for example here plywood, is chosen to have, for a given and low density (of the order of 100 to 1000 kg / m3), good rigidity in the three directions (some GPA), good shear strength, good compressive strength. It is naturally a brake on the propagation of a wave and allows a continuous connection with the adjacent layers.

[0106] The plywood must be able to deform: the wave by moving in the thickness of the shell causes an effect of "swelling" then of contraction which is localized preferentially in the thickness of the plywood forming the structural layer. 213 which acts as a bellows spring. This change in thickness causes a mechanical impedance mismatch favorable to the desired effect between the shell 21 and the connecting elements 22a, 22b, 23a, 23b and contributes to the resistance to the movement transmitted by reducing the peeling forces between the layers.

[0107] It should be noted that the mechanical properties of the composite structure can be sy metric or asymmetric depending on the type of stress against which one seeks to protect oneself.

[0108] The arched shape of the protective structure makes it possible to avoid stress concentrations (no discontinuity) unlike a "V" structure present in the prior art.

[0109] Materials other than glass fibers can be considered for the structural layers 212, 214. By way of example, carbon fibers could be used.

[0110] In the example of Figure 5, the elastomeric connecting elements 22a, 23a

(silicone for example) are connected to fixing or support elements 24a, 25a of the shell 21 to the vehicle 1.

These fixing or support elements 24a, 25a take the form of longitudinal sections, or beams, which are here arranged on the sides of the vehicle on either side of the composite shell 21.

In Figure 5, the upper support is referenced 25a and is arranged under the body C of the vehicle 1. The lower support, referenced 24a, is removable which allows a rapid change of the overprotection shell 21. The overprotective shell 21 is mounted with a pre-tightening adapted to the stress of the elastomer blocks forming the connecting elements 22a, 23a.

[0113] This same support 24a can be fixed to the structure to be protected by screws or other devices which can shear automatically at a given level of force. If the stress exceeds a given level, once it has completely dissipated, the overprotection releases the stored elastic energy which causes an action in the opposite direction on said organs and will cause them to shear. The supports 24a and 24b will be ejected, which will automatically decouple the overprotection from the structure to be protected.

The floor 11 on which the feet of the passengers are intended to rest (FIG. 4) takes the form of a lowered area, or bowl, making it possible to reduce the total vehicle height and to minimize the “z” dimension without touching the its ground clearance (figure 5).

[0115] The games J1 and J2 (Figure 5) are such that they allow the free movement of the overprotective shell 21.

[0116] The connecting elements 22a, 23a are arranged symmetrically with respect to the shell 21 and are of rectangular section in FIG. 5. The lower stud forming a connecting element 23a may be smaller than the upper stud forming an element of link 22a. The overprotective shell 21 is positioned by clamping between these two connecting elements 22a, 23a.

[0117] The connecting elements 22a, 23a are able to deform so as to allow the rotation and the translation of the shell 21 (notion of elasticity), to be able to also absorb part of the energy of the blast by deformation. and in returning the wave to the shell 21. In other words, the connecting elements 22a, 23a fulfill the function of articulation and allow degrees of freedom, deforming without changing state.

These connecting means are compact and light. They make it possible to dispense with, for example, rods or ball joints forming connecting means in the solutions of the prior art. The connecting elements are compressible and are sized so that they can withstand stress without deteriorating under the effect of the high pressures generated during a mine explosion. Their Poisson's ratio is almost equal to 0.5 in a particular example.

The section of the connecting elements (beam or blocks) is square or rectangular, for example.

[0120] Various examples of connecting elements are described below in relation to FIGS. 7 to 12. They appear in several of these examples in the overall form of a parallelepiped. [0121] It is noted that, in general, the choice of the section of the connecting element (23, 23-1, 23-2, 23-3, 23 ', 23 ", 23", 23 "" ) is guided by the static and dynamic properties of the elastomer, the geometry of the overprotection and its mode of operation, the nature of the threat, ...

[0122] Furthermore, the stiffness of the support (24, 24 ', 24 ”) can be obtained by any common means (box structure, section with adapted inertia, etc.) · The support (24, 24', 24 ”) Can be metallic but also composite, for example.

[0123] In Figure 7, the connecting element 23 takes the form of an elastomeric block of rectangular section 255 mm * 135 mm and which extends continuously over the length of the overprotective shell 21. The upper face constitutes the bearing face against the shell 21, the lower face being housed in a support 24 (arranged on the chassis side) of appropriate stiffness according to the size of the overprotection shell 21 (and therefore of the vehicle), threat, ...

[0124] The flanges 241a, 241b on the support 24 make it possible to promote the lateral retention of the block constituting the connecting element 23.

FIG. 8 is a variant of the solution of FIG. 7 in which the connecting element consists of several blocks 23-1, 23-2, 23-3 spaced apart (the choice of three blocks is only illustrative) the number of which depends, for example, on the size of the vehicle (or the system to be protected) and the threat.

[0126] FIG. 9 is a variant of the solution of FIG. 7 in which the connecting element 23 ’has chamfers on its face oriented towards the chassis side, the support 24’ having a complementary shape. There could be chamfers on the other face facing the overprotection side (not shown here).

[0127] Figure 10 is another variant of the solution of Figure 7 in which the connecting element 23 "has four rounded corners, the support 24" having a complementary shape.

[0128] In Figure 11, the connecting element 23 "has a trapezoidal section, the reduction of the support section allows greater flexibility of lateral displacement.

[0129] In Figure 12, the connecting element 23 "" has an ellipsoidal section, the support 24 "having a complementary curved shape.

The operation of the protection device 2 according to the invention is as follows.

The protection device 2 according to the invention has a behavior during the detonation of a mine which is totally different from that of the known devices.

[0132] The known devices must above all be mechanically resistant to avoid any tearing. They can take advantage of a V or curved shape to deflect part of the breath or even use plastic deformation to absorb a small part of the energy, but they are heavy and are not designed to be able to deform significantly in the elastic range. (therefore without major damage) during period of demand, which greatly limits the effect of "deconcentration". Finally, they do not take advantage of the dynamic advantages of a multi-material multi-layer system based on the stacking of layers having very different properties (coefficient 5 to 10 on the thicknesses and Young's moduli in the plane for example)

[0133] If a small part of the blast is deflected by the convex arched shape of the hull 21, most of the stress received vertically (in the particular case of a military land vehicle) causes a progressive flattening of the hull 21 towards the floor 11 as well as a progressive lateral displacement of the ends of the arch.

This mechanical deformation has slower kinematics than that of known devices.

When an explosion occurs under the vehicle, the pressure is exerted on the shell 21 which is strong enough to elastically deform and also to stop splinters and projections. The dimensions of the shell 21 give it an appropriate rigidity allowing it to distribute part of the energy received over the lateral connecting elements 22a, 22b, 23a, 23b.

[0136] Thus, the forces of the explosion are transferred through the shell 21 substantially to the sides of the vehicle. The explosion is widely dispersed and absorbed by the composite shell 21. Following the impact, the arch-shaped shell 21 oscillates and can take a quasi-planar shape before taking a shape having a radius of curvature smaller than initially and finally, after several oscillations, returning to its initial position. curve.

[0137] The beams constituting the lateral connecting elements are dimensioned to deform in bending and in compression in a relatively localized manner and make it possible (with a reduced bulk) to consume part of the energy produced by the blast of the mine. and return it to the hull 21.

The beams are made of elastomer, silicone or neoprene for example. The silicone reflects part of the wave and transfers the rest to the structure to be protected. In addition to the delay effect mentioned, there is therefore a reduction. In fact, the silicone behaves like a free semi-edge (two media with very different properties): the wave cannot go any further and therefore largely returns to the over-protective shell. The silicone therefore participates in trapping the waves in the overprotection. The wave will therefore make many round trips before starting to feed the silicone. The vibratory response of the floor takes place very gradually, in small steps, and shifted in time.

[0139] It is thus possible to ensure effective protection of the floor 11 of the vehicle with a relatively low protection thickness of between 100mm and 200mm, which allows the protection of the floor 11 of vehicles with reduced ground clearance. [0140] The device of the invention has the following advantages in particular:

[0141] Strength, flexibility and shear resistance,

[0142] Multi-material and multi-layered arch structure making it possible to elastically withstand the stress, among other things, because it does not present any geometric discontinuity in the area of interest (no weak link),,

[0143] Protection against ejecta, aggregates, and more generally projections commonly encountered in this type of stress (shield function),

[0144] Elastomer beams allowing infinite compression,

[0145] Low mass: lightness and mobility,

[0146] Compact assembly (reduced size),

[0147] No metal part (no corrosion problem), and

[0148] Reduced or non-existent maintenance.

[0149] The protection device 2 of the invention thus has a reduced weight and a relatively small total thickness without, however, penalizing the protection performance (the thickness of the composite shell 2 is a compromise between the weight and a short answer).

[0150] By way of example, a prototype produced on a 1/3 scale withstood an acceleration of 8000 g ("g" being the acceleration of standard gravity) and at a speed of projections (part one stress) of the order of 1700m / s.

[0151] The person skilled in the art will size the protection device 2 according to the characteristics of the threat against which he wants to protect the vehicle as well as according to the characteristics of the vehicle itself.

[0152] It is also understood that the protection device 2 of the invention can be configured to protect parts other than a vehicle floor, or even something other than a vehicle.

[0153] Other geometries of the shell 21 are possible.

In general, all convex shapes with constant or variable curvature are possible.

[0155] The curvature of the shell 21, however, is not essential. It was thus verified that when the radius of curvature is large, that is to say when the shell 21 is flat or almost flat, the performance is only slightly degraded. However, a curvature of the shell 21 improves the efficiency of the protection device 2 by providing rigidity at a lower cost, by avoiding concentrating the stresses at one point and by naturally filtering a part of the normal forces at the point of explosion. .

The radius of curvature of the shell 21 may be equal to 2.4 m or 4.8 m, for example for a vehicle of width equal to 2.5 m. A larger radius of curvature makes it possible to reduce the bulk, but slightly reduces the efficiency of the system while remaining more efficient than a flat steel solution with the same parameters (everything being equal otherwise).

[0157] A curved shell 21 presents another advantage. Indeed, the curved shape induces an angle of inclination of the contact surface of the shell 21 on the connecting elements 24a, 24b, 25a, 25b. This angle favors deployment, that is, the resistance to lateral movements is lower (and the echo of the wave transmitted to the connecting elements is even lower). Indeed, the radius of curvature changes during the blast and this change promotes the shearing of the connecting elements. By deforming, the connecting elements transmit less movement to the floor 11.

[0158] The stacking of the layers of the shell 21 presents a vulnerability to shear at the level of the inter-layers which tend to propagate cracking when the edges are damaged. The inventors had the idea of bringing the layers of the shell 21 upwards to avoid delamination of the shell: the significant change in direction of the layers improves the mechanical strength. Thus, in border zones, the opposite side edges of the shell 21 are cleverly folded back to avoid delamination.

[0159] Figures 13A and 13B show the contribution of such anti-delamination zb border zones.

[0160] FIG. 13A shows a non-edged shell 21 under the effect of the shock wave O (blast forming an overpressure zone) caused by the explosion of a mine M buried in the ground S. At an identical load , the displacement of the shell 21 with border (zone zb) (FIG. 13B) is less by a value “d” than the displacement of the shell 21 without the border zone (FIG. 13A).

[0161] The displacement under the effect of the blast is reduced for a hull with edging, as is the risk of critical delamination (complete rupture of the overprotection).

[0162] FIG. 14 illustrates a first edging solution, only one side edge of the shell 21 being shown. Note here that the top structural layer 214 is folded down and the bottom structural layer 212 is folded up so that the skins overlap on the side edges of the core 213.

[0163] The core corresponds to a structure comprising an alternation of layers of plywood or equivalent materials and layers of several composite materials.

In the example of FIG. 15, the upper structural skin 214 can be distinguished and it is observed that the skin or lower structural layer 212 rises, which participates in the edging function (hooping) so that the link between the composite part (plies of composite 213a) of the core (the core 213 consisting of n stacks 213a and 213b (ply of plywood or other material with similar properties) and the structural bottom skin 212 is greatly improved. protective structure 211 of the shell 21 also rises in the same direction as the lower skin structural 212.

[0165] In the example of FIG. 16, each ply of the core 213 and of the upper skin 214 undergoes several changes of direction which decreases the risks of delamination. The non-structural protective layer 211 of the shell 21 goes up in the same direction as the structural lower skin 212.

[0166] The peripheral ring 215 UD has a movement blocking function. In other words, it prevents displacement perpendicular to the plane of the layer.

[0167] The envelope 211 (subjected to impacts, flame, etc.) forming the non-structural protective layer of the shell 21 against aggregates is damaged and / or ablative. It is, in the solution of FIG. 16, also curved on its side edges. This envelope is made of a mat of glass and an epoxy resin, but it could also be a polyurethane or a filled / reinforced elastomer. This non-structural protective layer can incorporate metal or ceramic tiles intended to improve puncture resistance.

[0168] FIG. 17 is a top view showing the principle of the tiles: approximately 100 mm on the side, separated by a layer of mat in each layer of tile. The numeric references 100 to 400 correspond to the stacking order of the tiles. In other words, the tiles 100 are stacked before the tiles 200, themselves stacked before the tiles 300, .... In short, the tiles can move with respect to each other without really providing additional stiffness. The overlap provides comprehensive coverage.

[0169] It is important to note that this edging acts as a fold containment frame in the event of delamination in the current area (area located inside the containment frame). It therefore adds a function, that of limiting the risk of projection of additional elements in the event that the threat is much greater than the maximum threat, which could end up damaging the overprotection.

[0170] An important technical effect of the invention is that the protection device functions as a blast wave trapping mechanism. The speed of wave propagation in a material is proportional to the Young's modulus of that material. To oppose the wave propagation speed, you need a material with a very low Young's modulus. The Young's modulus of the protective structure varies according to the layers between 10 MPa and 200,000 MPa.

[0171] For comparison, the Young's modulus range of the more rigid materials currently used in overprotection extends from 3,000 MPa to 200,000 MPa depending on the layer.

The Young's modulus in statics of the different layers of the shell is, for example, equal to:

[0173] approximately 10 MPa for the elastomer; [0174] approximately 6000 MPa for a glass mat, which is almost isotropic in the plane;

[0175] approximately 5000 MPa for a plywood core, quasi isotropic;

[0176] about 21,000 MPa for a ply of woven glass in the directions of the fibers;

[0177] approximately 36000 MPa in the fiber directions, 7000 MPa in the transverse directions, for a glass UD;

[0178] approximately 200,000 MPa for steel scales.

As has been said previously, one of the desired properties is the resistance to stiffness ratio of the structural layers which correspond to references 212 and 214 in FIG. 13, which in the case of a UD Glass is close to 0.035 in traction and 0.023 in compression. In the case of an HR carbon, these ratios are respectively 0.022 and 0.014 (approximately -40% / glass). This explains the interest of fiberglass but also illustrates the potential to use other fibers.

[0180] It is important to specify that the protective shell 21 is not embedded: it is the same mechanical principle as the bridge abutment that is applied.

[0181] A damping system can be introduced by selecting a flexible material which can be an ultra-damping rubber.

[0182] The connection elements 22a, 23a on either side of the shell 21 can be maintained in different ways, and in particular by reversible fixing means. Thus, according to a particular implementation illustrated in FIG. 18, this maintenance is effected by pinching, by a screw-nut system.

[0183] A shell 21 having the shape of an arc of an ellipse can also be envisaged.

Claims

[Claim 1] A device (2) for protecting a mobile or static structure against the blast of an explosion or detonation and the associated projections of material, comprising a protective shell (21) made of several materials, said shell (21 ) protection being located at a distance from the structure to be protected and connected to said structure by elastomeric connecting means, said protective shell (21) being elastically deformable so as to be able to deform elastically over the duration of the solicitation by oscillating to spread over its surface and in time the energy of the blast of the explosion in several directions, then to return completely or in part to its original form after a lapse of time.

[Claim 2] A protective device (2) according to claim 1, characterized in that said protective shell (21) has materials whose Young's moduli are between 1000 and 200000 MPa in quasi-static.

[Claim 3] Protective device (2) according to claim 1 or 2, characterized in that said protective shell (21) consists of a multilayer structure.

[Claim 4] A protective device (2) according to one of claims 1 to 3, characterized in that said protective shell (21) comprises a first protective layer composed of several materials against projections of materials and associated ejecta. to said explosion, said first layer being intended to be oriented towards the blast side of the explosion.

[Claim 5] A protective device (2) according to claim 3 or 4, characterized in that said protective shell (21) comprises at least a first layer of material having a Young's modulus of between 1,000 and 10,000 MPa, one of which is first face oriented towards the structure to be protected is covered by at least one structural layer and the second opposite face of which is covered by at least one other structural layer.

[Claim 6] A protective device (2) according to one of claims 3 to 5, characterized in that the ends of at least part of the material layers of said protective shell (21) are curved.

[Claim 7] A protective device (2) according to one of claims 1 to 6, characterized in that said protective shell (21) is mounted on the elastomeric connecting means by means of fastening means de- mountable and possibly with calibrated breaking level.

[Claim 8] A device for protecting (2) a part of a vehicle, according to any one of claims 1 to 7, characterized in that the elastomeric connecting means are continuous or spaced supports extending in length. periphery of the protective shell (21).

[Claim 9] Vehicle (1) comprising at least one protection device (2) according to any one of claims 1 to 8.

[Claim 10] Vehicle (1) according to claim 9, characterized in that it is a land vehicle comprising a floor below which is arranged a protection device (2) according to any one of claims 1 to 8.