FR3071290B1 - AUXETICAL SHOCK - Google Patents

Abstract

An auxetic damper comprising a framework formed by rods connected to each other at primary and secondary junction points, the framework forming part of a rectangular parallelepiped volume mesh network having at least two non-square faces, each vertex of a mesh being each occupied by a primary junction point, the primary junction points of each face of a mesh being connected to each other by rods meeting at a secondary junction point offset from said face. The invention is of interest to all stakeholders interested in damping links in the space sector, automotive, railway or aeronautics.

Description

TECHNICAL FIELD [0001] In general, the invention relates to an auxetic damper, a method of manufacturing an auxetic damper and its use in the space, automotive, railway or aeronautical sectors.

BACKGROUND [0002] The damping bonds are usually made by assembling several pieces comprising several materials. For example, damping connections can be made by assembling metal parts (for mechanical strength) and elastomer parts for damping dynamic loads (eg shocks and / or vibrations).

JPH document 04113998 gives an example of damping element for the outside of a satellite. In particular, the document discloses a shock absorbing element selectively deployable around a satellite to absorb shocks. The absorbent element comprises a plurality of metal parts woven into a buffer element. The metal parts allow mechanical retention of the absorbent element. In addition to a difficult fabrication and deployment, the proposed solution absorbs shocks at the level of the woven connections less than at the level of the absorbent elements.

Technical Problem [0004] The objective of the present invention is to improve the existing solutions of damping bonds.

GENERAL DESCRIPTION OF THE INVENTION [0005] A first aspect of the invention relates to an auxetic damper comprising a framework formed by rods connected to each other at primary and secondary junction points. The framework is part of a mesh network with a rectangular parallelepiped volume having at least two non-square faces. Each vertex of a mesh is occupied by a primary junction point. The primary junction points of each face of a mesh are connected together by rods joining at a secondary junction point, offset from said face.

[0006] It will be appreciated that the fact of shifting the secondary junction points imposes constraints on the movements of the primary junction points in the case where a force is applied to the auxetic damper (eg compression, traction). The constraints implied by the offset of the secondary junction points define the auxetic behavior.

In particular, "auxetic damper" means a damper having at least one negative Poisson's ratio. A Poisson's ratio quantifies the ability of an object (here the auxetic damper) to expand or compress in one of the directions perpendicular to a direction of applied force (compression or traction). A Poisson's ratio quantifies the deformation ratio of the object in a direction perpendicular to an applied force (compression or traction) with respect to the deformation in the direction of the force applied.

According to one embodiment, the Poisson's ratio of the auxetic damper is between -1 and 0.5 preferably between -1 and -0.1, still more preferably between -1 and -0.5, depending on the direction of the effort applied. For example, if we consider an auxetic material whose Poisson's ratio is -k (for a direction of effort and a given direction of reaction of the material, perpendicular to the direction of effort, with k positive). When this material is compressed (respectively towed) by a length AL in the compression direction, the material will react by shrinking (or stretching) in said reaction direction of k AL.

According to one embodiment, the auxetic damper has a specific elastic stiffness and / or an anisotropic Poisson's ratio, that is to say one. a specific elastic rigidity and / or Poisson's ratio depending on the direction in which the force is applied and / or the reaction direction considered. Preferably, the specific elastic stiffness and / or a Poisson's ratio have cubic or orthotropic symmetry. "Specific elastic rigidity" means resistance to elastic deformation (elastic deformation by tension, compression, bending and / or shearing) of the auxetic damper. In particular, the specific elastic stiffness in the direction of an applied force is defined as the ratio of the modulus of elasticity in said direction to the volume fraction of the material. The resistance to deformation can be, p. ex. quantified by the stiffness tensor. According to a preferred embodiment, the specific elastic stiffness and / or the Poisson coefficients are different depending on whether the force is applied along one of the three axes defined by the network of meshes (ie the axes which extend in parallel with the edges -virtual-meshes) and / or in any direction in the orthonormal frame defined by the three axes of the network. According to one embodiment, the specific elastic stiffness of the damper amounts to between 10-5 and 10-3 times the Young's modulus of the constituent material of the rods and the junction points. According to one embodiment, the shear modulus of the damper is between 10-4 and 10_1 times the shear modulus of the material constituting the rods and the junction points.

It should be noted that in this document, the description of the auxetic damper and its structure is made in the case where the damper is at rest. "At rest" means the absence of external force applied to the auxetic damper. In the case where the auxetic damper tends to deform under the action of its own weight, this deformation is not taken into account in the description of the damper. It should be noted that the invention is not limited to idle dampers.

Preferably, the secondary junction point which joins the rods connecting the primary junction points of a face of a mesh is set back with respect to said face, inside said mesh.

[0012] Preferably, the network formed by the framework is an orthorhombic or tetragonal network. An orthorhombic network is invariant under the symmetry operations of the point groups 222, mmm and mm2 (expressed by the Hermann-Mauguin symbols). A tetragonal network is invariant under the symmetry operations of the point groups 4.4, 4 / m, 422.42m4 / mmm. [0013] Preferably, the secondary junction point relative to a face is located on the line normal to said passing face. by the isobarycenter of said face.

According to one embodiment, the meshs of the network are connected to each other (only) at the primary junction points. In this case, a primary junction point is generally shared by 8 meshes, unless it is located on one edge of the auxetic damper where the primary junction point is shared by four meshes (on one face), two meshes (on an edge), or belongs to a single mesh (on a corner).

The constituent material (s) of the rods may be selected from the following group of materials: alloys (eg 316L stainless steel), metals (eg aluminum), metals and / or alloys shape memory (eg nickel-titanium alloy), thermoplastic polymers (eg polyaryletherketones), thermosetting polymers (eg polyepoxides), elastomers (eg polyurethanes) and / or composite materials ( eg carbon fiber reinforced). The rods may optionally comprise several constituent materials of said group of materials.

Preferably, the rods are rectilinear. The rods may possibly deform elastically when a force is applied to the auxetic damper. The stems can, p. eg, flex, compress, etc.

The rods may be massive or hollow, and optionally include an internal framework (microstructured rods). The stems may also include joints so, e.g. eg, to control where the rods flex when a force is applied to the auxetic damper. The stems may also have a variable section (thickness) along the stem. It will be appreciated that these elements can contribute to the anisotropy of the reaction of the shock absorber vis-à-vis an external force (specific elastic stiffness and / or Poisson's ratio).

The mesh parameters (length, width and height), the constituent material (s) of the rods, the internal microstructure of the rods, the section (thickness) of the rods, the shape of the rods (for example, right pad, cylinder). right, cone) and / or the amount of constituent material used for the primary and / or secondary junction points may vary spatially (continuously or stepwise). In this way, porosity and density, stiffness, etc. of the damper can vary spatially.

A second aspect of the invention relates to a method of manufacturing an auxetic damper as described above. The method includes additive manufacturing (or 3D printing) of the auxetic damper. Alternatively or additionally, the process may comprise a molding, sintering, extrusion, radiation curing and / or rolling step.

A third aspect of the invention relates to a spacecraft comprising a damper based auxetic damper described above. The auxetic damper may optionally be positioned to mitigate dynamic stresses (e.g., shocks and / or vibrations) from, eg. ex. the propulsion of the machine on a payload transported by the spacecraft. In this context, the auxetic damper could be placed at the link between a satellite and the launcher intended to carry it into orbit.

A fourth aspect of the invention relates to a motor vehicle, railway or aeronautic comprising a vibration damper based auxetic damper described above. The auxetic damper may possibly be positioned in such a way as to attenuate the vibrations originating, e.g. eg, the vehicle engine (s).

It will be appreciated that, compared with conventional dampers, the various aspects of the invention allow greater simplicity of manufacture, a reduction of production costs and a reduction of the total mass of the damper.

BRIEF DESCRIPTION OF THE DRAWINGS [0023] Other features and characteristics of the invention will become apparent from the detailed description of certain advantageous embodiments presented below, by way of illustration, with reference to the appended drawings which show:

Fig. 1: a cross section at a launcher-satellite link representing the distribution of several auxetic dampers according to one embodiment of the invention;

Fig. 2: a detailed view showing the elementary meshes of an auxetic damper according to one embodiment of the invention;

Fig. 3: a view from another angle of the elementary mesh shown in FIG. 2;

Fig. 4: a simplified view of an elementary mesh of the auxetic damper according to one embodiment of the invention;

Fig. 5: a more complete view of the elementary mesh illustrated in FIG. 3 representing all the stems of an elementary mesh;

Fig. 6: a representation of an external force applied to an elementary cell as well as the reaction of the mesh to this effort; and

Fig. 7: an arrangement of several elementary meshes of an auxetic damper according to one embodiment of the invention.

Detailed Description of Embodiments of the Invention [0024] FIG. 1 illustrates the distribution of several auxetic dampers according to one embodiment of the invention. In particular, FIG. 1 illustrates the positioning of auxetic dampers 10 at the interface between a satellite and a launcher provided for the setting into orbit of the satellite. The dampers 10 are positioned regularly, along the circumference 12 of the launcher, in order to damp the dynamic stresses (eg shocks and / or vibrations) generated by the launcher. The attachment of the damper to the launcher elements and the satellite can be achieved by any appropriate means not involving the auxetic properties of the damper, p. ex. using screws. The dampers 10 may for example be used to support and dampen shocks for valves, pressure reducers, electrical equipment or even ensure the connection between the engine mount launcher and the rest of the launcher or satellite.

Typically, the dimensions of the auxetic damper 10 can be between 10 mm and 500 mm, preferably between 50 mm and 400 mm, more preferably between 100 mm and 300 mm in a first direction, between 4 mm and 200 mm preferably between 20 mm and 150 mm, more preferably between 40 mm and 100 mm in a second direction, perpendicular to the first direction, and between 2 mm and 100 mm, preferably between 10 mm and 70 mm, more preferably between 20 mm and 50 mm in a third direction, perpendicular to the first and second directions. Preferably, the directions are given by the edges of the meshs of the network.

[0026] FIG. 2 illustrates in more detail the auxetic damper 10 and the elemental meshes 14 constituting the frame of the damper 10. The auxetic damper 10 comprises in fact a plurality of meshes 14 comprising a plurality of rods. The damper 10 is an architectural material, whose structure is obtained by a repetition of the stitches 14. The mesh sizes are between 0.1 and 100 mm, preferably between 0.2 and 20 mm, more preferably between 0.5. and 10 mm.

The elementary meshes 14 of the damper 10 are interconnected by their vertices 16. FIG. 3 illustrates the elementary mesh 14 at another angle which makes it possible to show all the vertices 16 of the elementary mesh 14. The structure of the elementary meshes 14 is described hereinafter with reference to FIG. 4 and in FIG. 5.

In the embodiment illustrated in FIG. 4 and in FIG. 5, the mail 14 is a tetragonal mesh, ie a rectangular parallelepiped-shaped mesh of which two dimensions are equal and a third dimension is different from the first two. In particular, here the width and the height are equal (a) and the length is different (b).

Each vertex 20 of the mesh 14 corresponds to a primary junction point 20. The primary junction points 20 bind the different meshes 14 together, thus forming the damper 10.

The primary junction points 20 of each face of a mesh 14 are bonded together through rods 22 joining at a secondary junction point 24. FIG. 2 illustrates only the rods 22 in relation to the face 26 for clarity. Fig. 3 illustrates all the rods 22. A primary junction point is therefore a point where 24 rods meet, except in the case where the primary junction point is on an edge of the damper 10. The thickness of the rods is between 0.01 and 5 mm, preferably between 0.1 and 2.5 mm, more preferably between 0.1 and 1 mm. The secondary junction points have a size of between 0.01 and 5 mm, preferably between 0.1 and 2.5 mm, more preferably between 0.1 and 1 mm.

The secondary junction point 24 relative to the face 26 is located inside the mesh 14. As a result, the corresponding rods 22 are all directed towards the inside of the mesh 14. In the embodiment illustrated, four rods meet at each secondary junction point 24.

The rods of the embodiment illustrated in FIG. 4 and in FIG. 5 are rectilinear. In addition, the rods relating to a face are all the same length. Consequently, the secondary junction point 24 is situated on the line normal to the face 26 passing through the isobarycenter of the face 26. According to one embodiment, the rods relating to a face could have different lengths and, consequently , the secondary junction point 24 would be displaced with respect to the illustrated embodiment. It will be appreciated that, depending on the position of the secondary junction point 24, the reaction of the damper to an external force is different.

The rods 22 of the embodiment illustrated in FIG. 4 and in FIG. Preferably, rods formed of a shape memory alloy (eg NiTi) are preferred. In other embodiments, the rods are formed from alloys (eg Invar, 316L and 304L stainless steels, Inconel 718 and 625 superalloys, TA6V titanium alloys, aluminum alloys, etc.), metals (copper), thermoplastic polymers (polyamide (PA), polyimide (PI), polypropylene (PP), polystyrene (PS), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), etc.), thermosetting polymers (polyurethane (PU or PUR) ), vinylester (VE), polyepoxide (EP), bismaleimide (BMI), crosslinked polyimides (PIRP), etc.), elastomers (polyisoprene (IR), polybutadiene (BR), styrene-butadiene (SBR), thermoplastic polyurethane (TPU) thermoplastic elastomer (TPE), thermoplastic olefin (TPO), ethylene-propylene-diene (EPDM), neoprene (CR), etc.) and / or composite materials (fiber-reinforced polymer (GFRP), polymer with carbon fiber reinforcement (CFRP), etc.). The materials constituting the frame are chosen according to the application and the manufacturing method.

The rods 22 of the embodiment illustrated in FIG. 4 or in FIG. 5 are massive cylindrical rods (constant thickness along the entire length of the rods). According to other embodiments, the stems could be hollow, have an internal framework, have joints (flexible) in some places (eg near junction points), or a combination of these features.

[0035] FIG. 6 illustrates the reaction of a mesh 14 with an external force 28. While the force is transmitted from one mesh to the other through the primary junction points 22, the rods 22 impose constraints on the reaction of the mesh. In particular, the force 28 induces, through the rods 22, a displacement of the secondary junction points 24 towards the inside of the mesh 24. The displacement of the points secondary junction 24 forces the primary junction points 22 to move inwardly of the mesh 14, as represented by the arrows 30. In other words, when the mesh 14 is compressed by the force 28, the Reaction of the mesh to this compression is a narrowing in the transverse directions. This behavior is said to be "auxetic" and results in a negative Poisson's ratio. In addition, the auxetic damper has a specific elastic rigidity amounting to between 10-5 and 10-3 times the Young's modulus of the material constituting the rods and junction points.

While the embodiment illustrated in FIG. 7 refers to an assembly of a plurality of identical meshes, different elementary meshes could be combined to form the auxetic damper. Therefore, according to one embodiment, the mesh parameters (length, width, height of the mesh), the constituent material (s) of the rods, the thickness of the rods, the length of the rods, the microstructure of the rods and / or the quantity and density of the constituent material used for the primary and / or secondary junction points vary spatially.

According to a preferred embodiment, the mesh density is increased when one approaches the faces attached to the launcher and the satellite, e.g. ex. thanks to an increase in the thickness of the stems and / or a change in the dimensions of the elementary stitches.

It should be noted that all or part of the characteristics of the meshes and the frame of the damper 10 may be from an optimization process, p. ex. in order to comply with specifications. It will be appreciated that many degrees of freedom for optimization can cover a broad spectrum of requirements depending on the desired applications.

The damper 10 is preferably manufactured by an additive manufacturing process (3D printing), possibly controlled by a computer-aided design module (CAD). Optionally, CAD can be configured based on an optimization process.

Preferably, the additive manufacturing process comprises a selective laser sintering ("selective laser sintering" in English), a selective laser melting ("selective laser melting" in English) or electron beam ("electron beam"). additive manufacturing "), laser coating (" laser metal deposition "or" Laser cladding "in English), extrusion (eg rods) and / or stereolithography.

While particular embodiments have just been described in detail, those skilled in the art will appreciate that various modifications and alternatives to these can be developed in light of the overall teaching provided by the present disclosure of the invention. the invention. Therefore, the specific arrangements and / or methods described herein are intended to be given by way of illustration only, with no intention of limiting the scope of the invention.

Claims (13)

claims 1. An auxetic damper (10) comprising a framework formed by rods (22) connected to each other at primary (20) and secondary (24) junction points, the framework forming part of a network of meshes (14) rectangular parallelepipedal volume having at least two non-square faces (26), each vertex of a mesh being each occupied by a primary joining point (20), the primary joining points (20) of each face (26) of a mesh being connected together by rods (22) joining at a secondary junction point (24) offset from said face (26). 2. The auxetic damper (10) according to claim 1, wherein the secondary junction point (24) to which the rods (22) connecting the primary junction points (20) of a face (26) of a mesh is set back from said face (26), inside said mesh (14). 3. The auxetic damper (10) according to any one of claims 1 to 2, wherein the mesh (14) of the network are connected to each other at the primary junction points (20). 4. The auxetic damper (10) according to any one of claims 1 to 3, wherein the auxetic damper (10) has a specific elastic stiffness and / or an anisotropic Poisson's ratio. 5. The auxetic damper (10) according to any one of claims 1 to 4, wherein the specific elastic stiffness of the damper is between 10-5 and 10'3 times the Young's modulus of the constituent material. rods (22) and junction points (20, 24). 6. The auxetic damper (10) according to any one of claims 1 to 5, wherein the Poisson's ratio of the auxetic damper (10) is between -1 and 0.5. 7. The auxetic damper (10) according to any one of claims 1 to 6, wherein the mesh parameters (14), the constituent material or rods (22), the thickness of the rods (22), the internal microstructure of the rods (22), the shape of the rods (22) and / or the amount and density of constituent material used for the primary (20) and / or secondary (24) junction points vary spatially. 8. The auxetic damper (10) according to any one of claims 1 to 7, wherein the constituent material or rods (22) are selected from the group of materials: alloys, metals, metals and / or alloys shape memory, thermoplastic polymers, thermosetting polymers, elastomers and / or composite materials. 9. The auxetic damper (10) according to any one of claims 1 to 8, wherein the rods (22) are rectilinear. 10. The auxetic damper (10) according to any one of claims 1 to 9, wherein the secondary junction point (24) is located on the line normal to said face (26) passing through the isobarycentre of said face (26). 11. A method of manufacturing an auxetic damper (10) according to any one of claims 1 to 10, the method comprising the additive manufacturing of the auxetic damper (10). Spatial machine comprising a vibration damper based on the auxetic damper (10) according to any one of claims 1 to 10. Motor vehicle, railway or aircraft, comprising a vibration damper based auxetic damper (10) according to any one of claims 1 to 10.