Porous structure for aerospace applications having a substantially bidimensional development, related use and related device

Abstract

The present invention refers to a porous structure for aerospace applications having a substantially bidimensional development, comprising a first layer of composite material and, optionally, a second layer of composite material, wherein said first layer of composite material comprises a polymer matrix, a first fibrous filler and a second filler, said polymer matrix being a thermoplastic polymer, wherein said second layer of composite material is coupled to said first layer of composite material and comprises a non-crosslinked elastomer and a third filler, wherein said second filler and / or said third filler is in the form of a nano-filler and / or of a micro-filler, and wherein said first layer of composite material or said second layer of composite material has an average pore diameter lower than 1 mm; the present invention also refers to a device for trapping space debris comprising a support structure and said porous structure for aerospace applications having a substantially bidimensional development.

Description

[0001] Title: Porous structure for aerospace applications having a substantially bidimensional development, related use and related device

[0002] DESCRIPTION

[0003] Field of application

[0004] In its more general aspect, the present invention refers to a porous structure having a substantially bidimensional development, which is structured for having particular properties of absorption and distribution of high impact energies and adhesive properties.

[0005] The present invention also refers to a use of said porous structure having a substantially bidimensional development, as well as a device in aerospace field comprising the same porous structure having a substantially bidimensional development.

[0006] The present invention is generally but not limitedly applied in the space field for the collection of small-sized debris which is present in orbit.

[0007] Prior art

[0008] As is well known in the above-mentioned preferred technical field, over the past 37 years, thousands of space vehicles have been launched into orbit for scientific, commercial, earth observation and national security purposes.

[0009] An effect of this activity was the creation of a large population of debris orbiting around the Earth.

[0010] Debris essentially refers to artificial space objects that perform no useful function.

[0011] Human-made space debris has various sources:

[0012] - each rocket sent into orbit discards part of its engine casing once the fuel it contains has been exhausted; - many redundant satellites are simply left in orbit;

[0013] - debris is created when space vehicles explode due to the accidental detonation of fuel or unused batteries, about 200 are supposed to have done so, or are the result of collisions between space vehicles or pieces thereof.

[0014] Space orbits are estimated to contain more than 36,500 known pieces of large-sized space debris, approximately 1 million pieces of medium-sized debris, and more than 200 million small-sized pieces.

[0015] Regarding a definition of the size:

[0016] - large-sized debris means debris with an average size greater than 10 cm;

[0017] - medium-sized debris means debris with an average size comprised between around 1 cm and 10 cm;

[0018] - small-sized debris means debris with an average size comprised between 1 mm and around 1 cm.

[0019] Much of this debris will remain in orbit for hundreds of years or more, representing a long-term danger to future space activities.

[0020] In particular, objects smaller than 5 centimeters are difficult to track individually, even if they are in low earth orbit; therefore, population size estimates largely rely on statistical sampling and modeling techniques.

[0021] The fact that the society increasingly relies on satellites increases the risk of collision with the aforementioned space debris, which travels with an average impact speed of around some tens of km / s in low orbit, the orbit in which most commercial satellites are stationed.

[0022] Furthermore, space debris also threatens astronauts and, more generally, the manned space flight. The risk of collision is complex since it depends on both anthropic and natural factors. It is marked by reinforcing feedback circuits, wherein newly generated debris can create further debris.

[0023] It is difficult to evaluate the probability of occurrence, the severity, including in monetary terms, and the cascading effects.

[0024] A collision between an active satellite and a large debris object will most likely result in a catastrophic destruction of the satellite.

[0025] However, collisions with small-sized objects are also particularly problematic, potentially compromising the achievement of mission objectives, reducing mission duration or, depending on where the satellite is hit, causing mission failure.

[0026] For example, collisions with small-sized objects and solar panels can shorten useful life by reducing the ability to charge onboard batteries, while collisions with fuel tanks or communication electronics can instantly disable critical functions for the mission.

[0027] These small-sized debris are, therefore, commonly defined in technical jargon as "Lethal Non-Trackable debris" (LNT) due to the potentially serious consequences of the collision and the inability of tracking them.

[0028] In addition to the immediate damage that some collisions can cause, all collisions, both between active and inactive objects, produce additional debris that increases the overall risk of impacts with them, potentially causing a cascading process that would produce a field of debris that would make the low earth orbit permanently unusable and would cut off access to higher orbits.

[0029] The “Revus Project” study, carried out by the European Union, also demonstrated that the greatest risk for space vehicles is represented by objects in the range 2 to 3 mm.

[0030] From 2000 till today, the involvement of private companies in space field has not only consolidated but also expanded. In this new context, a marketing-oriented approach has emerged, characterized by ambitious initiatives and efforts to enter the space field with innovative business models.

[0031] There is therefore a large number of nations with their own space program and many private companies are also investing in the field. So, while there are currently around 3400 active satellites in the earth orbits, companies expect to have more than 40000 in the next decade, not including large structures that are being planned and developed, such as space stations for In Orbit Operations.

[0032] Even with good collision prevention operations and post-operation debris mitigation strategies, including de-orbiting capabilities, impacts with small-sized debris will increase, possibly creating more debris.

[0033] In recent years, global interest in the usability, sustainability and safety of orbit has become so great that it currently represents one of the priorities of institutions, which are trying to encourage science and industry to invest in finding possible solutions to the problem.

[0034] Laser ablation, a method for removing space debris by hitting it with a laser, was examined among the studied possibilities.

[0035] However, laser ablation requires a high-power laser device and a wide field of view and it could only remove space debris made of materials which are compatible with this technique.

[0036] Methods for removing space debris have also been proposed by placing satellites with damping structures in equatorial orbits, in order to be able to absorb and collect space debris in polar orbits which are nearly orthogonal to them.

[0037] However, even with this method, space debris would collide at extremely high speeds and the damping structures designed in this way would quickly deteriorate. Furthermore, a large amount of fuel would be required to allow recovery of the small-sized collected debris.

[0038] To date, in addition to these approaches, no systems have been developed for small-sized debris, which, as seen above, adds further drawbacks to those already envisaged in the prior art, as it is difficult to detect, potentially very harmful and in large amount.

[0039] CN109280306A discloses polymethacrylimide composite foam conductive wave absorbing material. This material is suited to absorb electromagnetic radiation and can be used for stealth of various aircrafts. This material comprises both a fibrous filler and a functional absorbing agent. However, this material is not suited to trap space debris and to withstand the high-energy impact with them.

[0040] WO2023137082A1 discloses a satellite comprising a space debris retaining structure comprising an energy-absorbing structure including itself a fibrous material having a mesh-like structure.

[0041] The technical problem of the present invention is to devise a device or a system which allows to overcome the above-mentioned drawbacks, specifically paying attention to the small- sized debris.

[0042] Further purpose is to provide a solution which guarantees structural resistance and integrity during operation.

[0043] Another purpose is to provide a solution which has flexibility and lightness characteristics, which are fundamental especially in space applications.

[0044] Still purpose of the present invention is to provide a device with a high thermal response capacity, since, again particularly in space applications, it is possible to have a variation of many degrees in a relatively short time.

[0045] Another purpose, still in particular for space applications, is to provide a device which can correctly be stored in compartments with predetermined size.

[0046] Finally, purpose of the invention is to provide a solution which has the lowest possible environmental impact, therefore paying attention to sustainability.

[0047] Summary

[0048] The solution to the aforementioned technical problem is to provide the use of an innovative high-performance material which can incorporate all the features of the purposes outlined above and can be adopted in a device which allows a maximum efficient use thereof.

[0049] Indeed, the technical problem is solved by a porous structure for aerospace applications having a substantially bidimensional development, comprising a first layer of composite material and, optionally, a second layer of composite material.

[0050] Said first layer of composite material comprises a polymer matrix, at least one first fibrous filler and at least one second filler.

[0051] Said second layer of composite material, if present, is coupled to said first layer of composite material and comprises a non-crosslinked elastomer and at least one third filler.

[0052] Specifically, said at least one second filler and / or said at least one third filler is in the form of a nano-filler and / or of a micro-filler, and said first layer of composite material or said second layer of composite material has an average pore diameter lower than 1 mm.

[0053] In particular, the average pore diameter of said first layer of composite material or of said second layer of composite material is calculated, based on SEM microscopy, according to the standard directive ISO / TS 21383:2021.

[0054] “Porous structure having a substantially bidimensional development” means a “sheet” having almost bidimensional size, wherein two dimensions, that is length and width, are preponderant or, in other words, prevail by several orders of magnitude over a third dimension, that is thickness, and which can for example be folded during storage and deployed in a operational step to be stretched, in case of space applications, in such a way as to trap and collect debris.

[0055] Advantageously, thanks to the suitable sizing of the pores of the first layer of composite material or the second layer of composite material, the present solution allows microparticles to be trapped.

[0056] Furthermore, thanks to the combination of high-resistance materials, including said first fibrous filler and said second filler, such as for example a dispersion of nano-fillers, which are present in said first layer of composite material, the present solution points out peculiar elasticity and mechanical resistance characteristics with regards to / with respect to high-energy impacts which prevent the deterioration of the macrostructure, carrying out its functions in extreme operating environments such as space and especially interacting with physical stimuli in an “intelligent” way, using non-linear responses to manage the stresses through the combination of specific properties of the material and through an arrangement of the stress over the entire porous structure.

[0057] Additionally, thanks to the combination the polymer matrix of the first layer of composite material with said at least one first fibrous filler and with said at least one second filler and / or the combination of the noncrosslinked elastomer of the second layer of composite material with said at least one third filler, the overall porous structure has a shape memory when stressed below its yield point and, therefore, the energy generated by the impact is handled by the entire structure, which deforms at the macroscopic level and returns to its initial shape after the debris is trapped.

[0058] Preferably, said first layer of composite material or said second layer of composite material has an average pore diameter comprised between 20 nm and 5 jim.

[0059] Preferably, the thermoplastic polymer is selected from a polyester, a polyester co-polymer, a polyaryletherketone, a polyaryletherketone copolymer or any combination thereof.

[0060] Preferably, the thermoplastic polymer is a polyester, more preferably a semi-aromatic or aromatic polyester, more preferably selected from polyethylene terephthalate, polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), copolymers thereof (that is, copolymers of corresponding monomers) or any combination of the foregoing.

[0061] More preferably, the polyethylene terephthalate can be selected from polyethylene terephthalate essentially made up of monomers deriving from terephthalic acid and ethylene glycol (PET) or it can comprise monomers deriving from terephthalic acid and ethylene glycol or modified derivatives thereof (for example, PETP or PET-P).

[0062] Preferably, the thermoplastic polymer is polyaryletherketone, more preferably polyether ether ketone (PEEK) .

[0063] Preferably, the thermoplastic polymer is selected from polyethylene naphthalate (PEN), polyether ether ketone (PEEK) or any combination thereof.

[0064] Advantageously, the present solution allows maintaining high mechanical performances, with a deformation that can be recovered based on the elastic response of the matrix of the first layer of composite material, thanks to the suitable use of a polymerization or cross-linking additive which can specifically be added to the thermoplastic polymer of the first layer of composite material, as will be seen below, or of the dynamic vulcanization of the soft phase dispersed in the second layer of composite material, thanks to the suitable use of a vulcanization control additive.

[0065] Preferably, in the first layer of composite material, said thermoplastic polymer has an elastic modulus between 1500 MPa and 5000 MPa, as calculated according to standard directive D3039 / ASTM D 3039M-08.

[0066] More preferably, said thermoplastic polymer has an elastic modulus higher than 1800 MPa and lower than or equal to 2000 MPa, as calculated according to standard directive D3039 / ASTM D 3039M-08.

[0067] Alternatively, in the first layer of composite material, said thermoplastic polymer has an elastic modulus higher than 2000 Mpa, preferably between 2000 Mpa and 5000 Mpa, as calculated according to the standard procedure D3039 / ASTM D 3039M-08.

[0068] Advantageously, the present invention guarantees to obtain an adequate elongation under strain of the porous structure for aerospace applications having a substantially bidimensional development according to the invention.

[0069] According to the present invention, the expression “fibrous filler” means a filler made of at least one type of fiber, that is by a single type of fiber or by a combination of different types of fibers; in particular, said fibers are high-melt fibers, that is fibers with high resistance to high temperatures and / or fibers having distortion temperatures higher than operating temperatures and / or fibers having a predetermined tensile strength.

[0070] Preferably, in the first layer of composite material, said fibrous filler is made of fibers which have a tensile strength equal to or higher than 400 MPa, more preferably comprised between 2000 and 6000 MPa.

[0071] Preferably, said first fibrous filler is in the form of a lattice weave, said lattice weave being embedded or immersed in the matrix of the first layer of polymeric material.

[0072] More preferably, in said first layer of composite material said first fibrous filler is selected from a carbon fiber, high modulus polypropylene (HMPP) fiber, ultra-high molecular weight polyethylene (UHMWPE) fiber, silicon carbide fibers, cellulose-based fibers or any combination thereof.

[0073] Even more preferably, in said first layer of composite material said first fibrous filler is selected from a carbon fiber, high modulus polypropylene (HMPP) fiber, ultra-high molecular weight polyethylene (UHMWPE) fiber, silicon carbide fibers or any combination thereof.

[0074] According to the present invention, the expression "in the form of nanofiller and / or micro-filler" means that the second filler and / or the third filler is in the form of particles with at least a size lower than 100 nm, that is it includes nano-fillers.

[0075] In particular, the second filler and / or the third filler is selected from the group comprising a nano-structured carbon allotrope, silica nanoparticles, lamellar silica, AI2O3 micro-particles, AI2O3 nano-particles, aluminosilicate nano-inclusions or any combination thereof.

[0076] Consistently, the terms “nano-structured carbon allotrope”, “silica nanoparticles”, “AI2O3 nano-particles” and “aluminosilicate nano-inclusions” refers to particles of any shape with at least one dimension lower than 100 nm or agglomerates (“clusters”) thereof.

[0077] In particular, the uniform dispersion of these particles increases the interfacial interaction between the matrix and the dispersed phase, with a relative increase in the contribution of the filler to the overall features of the material, thus requiring a lower quantity of filler, and conferring specific functionalities which the material otherwise does not have.

[0078] In particular, advantageously, the presence of the first fibrous filler and the second filler in the first layer of composite material and the presence of the third filler in the second layer of composite material, which is possibly present according to a particular embodiment of the present invention, allow obtaining an improved mechanical resistance of the selected matrix, as well as modulating the elastic properties of the matrix itself. The adhesion and the stable trapping of the debris to the surface of the first layer of composite material or to the second layer of composite material, if present, is typically achieved through a chemical attraction which is guaranteed by the components contained within said layers, or through a physical trapping.

[0079] Preferably, the first layer of composite material or, if present, the second layer of composite material can comprise at least one additive / filler adapted to provide magnetic adhesion properties.

[0080] Advantageously, an electromagnetic attraction interaction, which is alternative or complementary to a chemical attraction interaction, can be established between the first layer of composite material and the debris thus trapped, or between the second layer of composite material, if present, and the debris thus trapped.

[0081] Alternatively, according to a preferred embodiment of the invention, said at least one second filler or said at least one third filler can be provided with magnetic properties.

[0082] In an embodiment, said at least one second filler and / or said at least one third filler is a nano-structured carbon allotrope and is selected from graphene, graphene nano-platelets, carbon nanotubes, carbon nano-rods or any combination thereof.

[0083] Advantageously, thanks to the presence of said second filler or third filler, the present solution simultaneously allows an efficient and effective operation of the porous structure having a substantially bidimensional development and the overall lightness thereof, which is particularly suitable for operation in orbit and for transport.

[0084] More preferably, said at least one second filler is present in the first layer of composite material in a total quantity, said in other words with a concentration, comprised between 1% and 10% by weight on its total weight. Advantageously, this selection allows having the desired reinforcement effect with a low total quantity of the second filler.

[0085] Still more preferably, said first material layer has a density not greater than 1.5 g / cm3.

[0086] Considering said first layer in its complete form consisting of a number of phases (first fibrous filler, second filler and any others) equal to i, we obtain the theoretical density as: wherein Wt is the composite i-phases mass, Vi is the volume of i-phases, pt the i-phases density and pcis the composite density, respectively.

[0087] The composite density is calculated as: and

[0088] The comparison of measured real density and theoretical density through ASTM-D2734 allows the evaluation of void content (Vv): wherein pmis is the measured density.

[0089] Preferably, the thermoplastic polymer has a glass transition temperature (Tg) lower than + 120°C, more preferably lower than - 140°C, still more preferably lower than - 160°C.

[0090] In fact, advantageously, at an altitude of 400 km, the thermal gradient varies between around - 160°C and 120°C and, therefore, said thermoplastic polymer has a glass transition temperature (Tg) lower than the Minimum Operating Temperature.

[0091] Thus, it is possible to guarantee, for example, that a macro structure does not stiffen at very low temperatures.

[0092] Alternatively, according to a preferred embodiment of the present invention, said first layer of composite material comprises a, in particular polymeric, polymerization agent, wherein said polymerization agent preferably has a glass transition temperature lower than 120°C, more preferably lower than - 140°C, still more preferably lower than - 160°C.

[0093] According to the present invention, the glass transition temperature (Tg) of the thermoplastic polymer and of the polymerization agent of the first layer of composite material is calculated according to the standard directive ISO 11357- 1:2023.

[0094] Advantageously, therefore, the present solution guarantees high flexibility in low temperature conditions also during an operational step.

[0095] Preferably, in said second layer of composite material, said noncrosslinked elastomer is selected from thermoplastic polyurethane, silicone elastomers or any combination thereof

[0096] More preferably, according to a preferred embodiment of the present invention, said second layer of composite material comprises a vulcanization control additive.

[0097] Preferably, in said second layer of composite material, said noncrosslinked elastomer has a glass transition temperature (Tg) lower than 120°C, more preferably lower than - 140°C.

[0098] Still more preferably, in said second layer of composite material said noncrosslinked elastomer has a glass transition temperature lower than - 150°C, mostly preferably lower than - 160°C.

[0099] According to the present invention, the glass transition temperature (Tg) of the non-crosslinked elastomer of the second layer of composite material is calculated according to the standard directive ISO 11357- 1:2023.

[0100] According to a first preferred embodiment of the invention, the present porous structure for aerospace applications having a substantially bidimensional development substantially comprises said first layer of composite material, which has an average pore diameter lower than 1 mm, preferably comprised between 20 nm and 5 gm.

[0101] In particular, the average pore diameter of said first layer of composite material is calculated, based on SEM microscopy, according to the standard directive ISO / TS 21383:2021.

[0102] In other words, according to said first preferred embodiment, the present invention takes the form of a porous structure having a substantially bidimensional development comprising a single layer of composite and porous material.

[0103] Preferably, said first layer of composite material is at least partially coated with an adhesive coating, more preferably said adhesive coating being made of epoxy adhesives and / or thermoplastic adhesives.

[0104] Advantageously, the present invention, in a context of using at least one porous structure having a substantially bidimensional development, optimizes the adhesive function of the porous structure, preferably and specifically with materials which are suitable for high temperature and conditions which are approximating vacuum.

[0105] In particular, the first layer of composite material is sprayed or impregnated with said adhesive coating.

[0106] Advantageously, still in the context of a single layer (that is the first layer of composite material) adapted to carry out all the required functions, the present solution is designed to enhance the debris adhesion functionality to the porous structure having a substantially bidimensional development according to this embodiment of the invention.

[0107] Advantageously, while the composite material of the first layer guarantees a suitable condition to allow impact resistance and debris physical interception, the stable ability of trapping debris particles, therefore their chemical adhesion, is guaranteed by said adhesive coating.

[0108] According to a second alternative embodiment of the invention, the present porous structure for aerospace applications having a substantially bidimensional development comprises both said first layer of composite material, and said second layer of composite material, wherein the latter has an average pore diameter lower than 1 mm, preferably comprised between 20 nm and 5 gm.

[0109] Specifically, the average pore diameter of said second layer of composite material is calculated, based on SEM microscopy, according to the standard directive ISO / TS 21383:2021.

[0110] In particular, if present, said second layer of composite material has an average pore diameter lower than 1 mm, preferably comprised between 20 nm and 5 gm, and said first layer of composite material has an average pore diameter higher or equal to 5 gm, preferably higher or equal to 1 mm.

[0111] In other words, according to said second preferred embodiment, the present invention takes the form of a porous structure having a substantially bidimensional development comprising a double layer of composite and porous material, that is said first layer and said second layer.

[0112] Advantageously, the present invention allows to divide the functions of the porous structure having a substantially bidimensional development into a first layer adapted to provide resistance and flexibility and a second layer adapted to absorb part of the impact energy, to capture and to trap the debris particles, also allowing them to penetrate the second layer of composite material, which then closes on itself and retains said particles, incorporating them therein.

[0113] Advantageously, according to this alternative embodiment of the invention, the first layer of composite material guarantees support, therefore providing adequate impact resistance properties, while the second layer of composite material determines a stable ability of trapping the debris particles.

[0114] In particular, the ability of trapping the debris particle of the second layer of composite material is guaranteed by virtue of both the physical and mechanical properties of said composite material and of its chemical properties, the latter providing for the chemical adhesion of the debris particles to the second layer.

[0115] According to a preferred embodiment thereof, said porous bidimensional structure having a substantially bidimensional development can be made of a plurality of portions, which are connected to each other, wherein each portion of said plurality of portions comprises said first layer of composite material and, optionally, said second layer of composite material, wherein each portion of said plurality of portions can have a geometry and / or size which is different from the geometry and size of the adjacent portion of said plurality of portions and / or wherein in each portion of said plurality of portions the composition of said first layer of composite material and, if present, of said second layer of composite material can vary with respect to the composition of the first layer of composite material and, if present, of the second layer of composite material of the adjacent portion of said plurality of portions.

[0116] In other words, as defined in the previous paragraph, the bidimensional porous structure of the invention can be provided in a modular manner.

[0117] When the porous structure having a substantially bidimensional development is formed by combining a plurality of portions, said porous structure having a substantially bidimensional development can therefore provide a combination of different chemical-physical and mechanical, as well as geometrical, properties and each of said plurality of portions will synergistically work with the others in order to redistribute loads and stresses generated by a high-energy event, thus allowing the whole porous structure to manage the energy which was not absorbed in the local response of the material at the impact point.

[0118] Advantageously, the porous structure having a substantially bidimensional development can be designed to allow modifications and extensions of the performances, customizing the structure based on needs and applications. It is therefore a design based on modular macro structures, wherein the combination of geometries and chemicalphysical properties of the modular parts or cells allows maximizing the performances of the system as a whole. Each of several modular parts can coat a selected portion of the total impact surface, with a suitable combination of areas with trapping properties and areas that provide mechanical stability and movement.

[0119] Advantageously, the modularity allows geometrical scalability [and] ease of sizing, furthermore by varying the physical arrangement of the cells and by slightly varying the formulation of the phases, the properties and the behavior of the entire structure change, for example, priority can be given to heat resistance, if it is not necessary to have great mechanical resistance, or the electromagnetic interactions can be increased making it react to a greater quantity of stimuli.

[0120] According to another aspect, the present invention provides a use of the porous structure for aerospace applications having a substantially bidimensional development as described above, preferably for trapping space debris having a size lower than around 1 cm.

[0121] Advantageously, the present solution allows absorbing high-energy collisions of particularly small debris; in fact, considering, for convenience of exposition, a geostationary orbit, the collision with a debris of 1 cm in diameter which orbits at a height of 36000 km will occur at a speed of 10 km / s, with a quantity of energy comparable to the one of a small car crashing at 40 km / h.

[0122] According to another aspect, the present invention provides a device for trapping space debris comprising a support structure to which the aforementioned porous structure for aerospace applications having a substantially bidimensional development is connected.

[0123] In particular, in an exemplary and non-limiting embodiment, the support structure can be a simple satellite which is moved in orbit and is connected, for example, through a plurality of rods to the porous structure, so as to transport it in the collection function thereof.

[0124] Advantageously, the present solution is optimal for collecting small-sized space debris, managing the intense impact energy thereof and being very efficient thanks to the design and structuring of the adopted material.

[0125] Furthermore, advantageously, the present technical solution is also optimal during transport.

[0126] Advantageously, the materials of which said support structure is made are optimal in terms of mechanical resistance, thermal resistance and lightness with respect to the requirements usually expected in space applications.

[0127] Although the focus was, by way of example, on space applications, nothing prevents from adopting the porous structure having a substantially bidimensional development described above also in other fields of application which envisage similar operational requirements or which can anyway be resolved through the adoption of the present invention or the scalable configurations thereof.

[0128] Further features and advantages of the porous structure for aerospace applications having a substantially bidimensional development, of the related use and of the related device according to the present invention will result from the description, made hereinbelow, of a preferred embodiment example given by way of indicative and non-limiting example with reference to the attached figures.

[0129] Brief description of the figures

[0130] Figure 1 shows a schematic view of a distribution of small-sized debris which are present on the earth orbits;

[0131] Figure 2 shows a schematic sectional view of a first embodiment of a porous structure having a substantially [bidimensional] development made according to the invention;

[0132] Figure 3 shows a schematic sectional view of a second embodiment of a porous structure having a substantially [bidimensional] development made according to the invention;

[0133] Figures 4A and 4B shows a schematic view of a support structure connected to the porous structure having a substantially [bidimensional] development of Figure 2.

[0134] In the different figures, similar elements will be identified by similar reference numbers.

[0135] Detailed description

[0136] In Figure 1, an exemplary distribution of the target population of objects classified as small-sized debris or fragments is shown, whose size ranges from around one millimeter to slightly over one centimeter. Their distribution in space is on many orbital levels, from low to geostationary orbits. As already mentioned, in a geostationary orbit, a collision with a debris of 1 cm occurs at a speed of 10 km / s, and will therefore have the same amount of energy as a small car crashing at 40 km / h.

[0137] These numbers are easily obtained through the formula: v =^ / GMR

[0138] With reference to the attached Figure 2, 1 globally and schematically indicates a first embodiment of a porous structure having a substantially bidimensional development made according to the present invention.

[0139] In the present embodiment, the porous structure 1 having a substantially bidimensional development la comprises a first layer of composite material 2 comprising a polymer matrix, a first fibrous filler 3 and a second filler 4, wherein the polymer matrix is a thermoplastic polymer, the first fibrous filler 3 is a carbon fiber and the second filler 4 is a combination of carbon nano-tubes and lamellar silica.

[0140] As illustrated, according to the present embodiment, the first fibrous filler is in the form of a lattice weave, wherein said lattice weave is embedded, in other words “immersed”, in the polymer matrix of the first layer of polymeric material.

[0141] Advantageously, the adoption of this lattice weave gives the desired nanometric porosity and the combination with the other constituent components of the first layer of composite material guarantees the required structural features.

[0142] The first layer of composite material 2 of the porous structure 1 having a substantially bidimensional development represented in Figure 2 has an average pore diameter lower than 1 mm, in particular comprised between 20 nm and 5 gm.

[0143] Furthermore, the porous structure 1 having a substantially bidimensional development illustrated in Figure 2 also comprises an adhesive coating 10, wherein the adhesive coating is made of epoxy adhesives and / or thermoplastic adhesives and at least partially coats the first layer of composite material.

[0144] In the following, for the sake of terminology coherence and to make reference to the various components easier, the term "macro structure" will instead hereinafter indicate the totality of all components, phases and properties of the microstructures that will constitute the macroscopic assembly, while the term "microstructure" will indicate the single components such as the first fibrous filler, the second filler or any other additive or filler which is present in the porous structure having a substantially bidimensional development described therein, such as a polymerization agent.

[0145] The thermoplastic polymer, in the present exemplary and non-limiting embodiment, is therefore an aromatic polyester, specifically polyethylene naphthalate (PEN).

[0146] In particular, polyethylene naphthalate (PEN) maintains the required high-performance mechanical properties.

[0147] Thanks to the specific composition thereof, the deformation that the first layer of composite material undergoes due to the impact with the debris can be recovered based on the elastic response of the polymer matrix also thanks to the presence of the polymerization agent, said polymerization agent having a glass transition temperature lower than 120°C, in particular lower than - 140°C, more particularly lower than - 160°C.

[0148] The glass transition temperature (Tg) can be calculated according to the standard directive ISO 11357- 1:2023.

[0149] In case of low temperature during the operational step, it is therefore necessary that the material remains very flexible and with a glass transition temperature lower than the working temperature.

[0150] The microstructure is therefore made so that the porous structure 1 having a substantially bidimensional development of the invention represented in Figure 2 and essentially comprising the first layer 2 of composite material has a shape memory when stressed below its yield point.

[0151] This is achieved by using a polymer as a matrix, that is naphthenate polyethylene, with a yield stress value lower than the energy exerted by the impact of the debris. The second filler 4 is present with a concentration comprised between 1% and 10% by weight and said first layer of composite material has a density not greater than 1.5 g / cm3.

[0152] This allows obtaining the desired reinforcing effect with a low dispersion concentration, without significantly influencing the weight of the porous structure having a substantially bidimensional development.

[0153] In fact, in applications such as in space, the weight of the systems can constrain the type of operational mission. Indeed, oversized structures require an increase in both construction and operational complexity. Mass budget is a system constraint required for most space missions and applications.

[0154] A porous structure 1 having a substantially bidimensional development designed in this way allows obtaining a material which is able to give nonlinear responses to the stresses and to interactively and synergistically combine the different properties of the components.

[0155] According to a first embodiment, a single layer of a porous and nanofilled structure having a substantially bidimensional development is therefore provided, wherein a micro- and macro-structuring make it possible to obtain a material that is capable of giving a timely response to the stress generated by the impact. Its stable trapping ability will be achieved through the development of chemical adhesive properties and possibly magnetic properties, thanks to the optional addition of an additive adapted to provide magnetic adhesion characteristics and useful in case of metallic debris.

[0156] Said chemical adhesive properties and possibly magnetic properties allow the debris to adhere to the surface without risking it breaking free after impact.

[0157] The composite material of the macro structure therefore provides a stable particle trapping ability thanks to the adhesion effects specifically generated on the surface of the material. Furthermore, the composite material has mechanical and impact properties suitable for the application temperature to prevent shattering, forming of weak points and collapse of the macro structure.

[0158] In fact, the polymer matrix is substantially elastic, so that, at maximum extension, it maintains sufficient tensile strength to withstand the residual energy of the particles.

[0159] The nano-structuring with the second filler 4 is used to modulate the properties of the elastic matrix.

[0160] The reduction of the speed of the debris can be consistently achieved by elastic deformation of the macro structure which favors a longer contact time with the surface of the porous structure having a substantially bidimensional development.

[0161] The particles can be trapped by the macrostructure, while the impact therewith reduces the orbital speed thereof, thus preventing the elastic repulsion from being stronger than the trapping adhesion, while the net deformation facilitates the trapping and adhesion.

[0162] The adhesive capacity towards different types of particles is achieved by the presence of surface properties that exert the necessary attraction / adhesion towards particles made of different materials, in which said surface adhesion properties are in this case obtained by the presence of the adhesive coating 10.

[0163] Figure 3 shows a second embodiment of a porous structure 1’ having a substantially bidimensional development la'.

[0164] In this case the porous structure having a substantially bidimensional development la' is obtained by overlapping at least two layers, among which a first layer 2' of composite material can have a composition substantially coinciding with that of the first layer 2 of the porous structure having a substantially bidimensional development la referred to in Figure 2. The first layer 2' of composite material can be deprived of its adhesion features and can have a higher average pore diameter and consequently a density lower than the porous structure 1, this layer primarily playing the role of load-bearing structure.

[0165] The first layer 2' of composite material consistently has an average pore diameter with equivalent volume greater than or equal to 1 mm. In macrofunctions, its role is to give strength and flexibility to the entire macro stru ctu re .

[0166] The porous structure having a substantially bidimensional development la' also comprises a second layer 20 of composite material having an average pore diameter lower than 1 mm, in particular comprised between 20 nm and 5 gm.

[0167] The second layer 20 of composite material is coupled to the first layer 2’ of composite material and comprises a non-crosslinked elastomer and a third filler. The third filler is carbon nanotubes or allotropic forms thereof.

[0168] As illustrated, also in this case, according to the present embodiment, the first fibrous filler is in the form of a lattice weave, wherein said lattice weave is embedded in the polymer matrix of the first layer of polymeric material.

[0169] Advantageously, due to the presence of this lattice weave in the first layer of composite material and synergistically with the other constituent components of the first layer of composite material, the required structural features are given to the latter.

[0170] However, unlike the solution shown in Figure 2, in the present embodiment, this lattice weave does not give the first layer of composite material nanometric porosity characteristics, which are instead present in the second layer of composite material.

[0171] Advantageously, according to this alternative embodiment of the invention, the first layer 2' of composite material guarantees support to the structure as a whole, therefore resistance and redistribution of the part of the impact energy which was not absorbed by the second layer 20, while the second layer 20 of composite material determines a stable ability of physically trapping debris particles, as well as the chemical adhesion thereof.

[0172] It should be understood that the additional layer 20 comprises elastomeric material designed to absorb part of the impact energy of the debris particles.

[0173] In particular, the additional layer 20, in the present embodiment, comprises a non-crosslinked elastomer, in particular said noncrosslinked elastomer being selected from thermoplastic polyurethane, silicone elastomers, or any combination thereof.

[0174] Its main function is to capture and trap the specific debris allowing it to penetrate into the material, which then closes on itself and retains this debris, thus incorporating it.

[0175] The support layer 2' therefore interfaces with the second layer 20, which is denser and characterized by adequate flexibility which allows sufficient deformation to form a cavity which is capable of mechanically trapping the impacted debris.

[0176] This form allows the mechanical deformation of the second layer 20 and allows trapping debris, obtaining physical and chemical trapping, therefore a better adhesion thanks to the longer contact time.

[0177] The material of the second layer 20 can deform in two ways, depending on the used polymer, with a plastic deformation or a non-elastic deformation.

[0178] In the present embodiment, the impact of the micro-debris with the material causes the non-elastic deformation of the polymeric material of the second layer 20 of composite material, which is softer, thus generating the formation of a micro-pocket that traps the particle. The presence of the support layer, that is the first layer 2’ of composite material, is necessary to guarantee the mechanical stability of the macro structure. The maximum / limit trapping capacity, as mentioned, is given by the saturation of the second layer 20 of composite material by the microparticles, without any kind of failure of the macro structure.

[0179] In other words, the macrostructure is designed to have a shape memory property. The macro structure deforms at the macroscopic level to allow energy management, the second layer 20 in the same time permanently deforms at the microscopic level in order to create an entrapment pocket, while at the macroscopic level it is be able to provide elastic recovery by absorbing part of the debris impact energy.

[0180] The adhesive ability of trapping capacity towards different types of particles can also be favored by the presence of surface properties, such as electromagnetic attraction and chemical adhesion, which are necessary to achieve stable trapping.

[0181] Accordigly, first layer and / or the second layer may comprise an additive made of magnetic material.

[0182] This additive can be used to give said first layer and / or second layer electromagnetic properties, thus generating electromagnetic interactions with the metal debris. This way, electromagnetic attraction between the first layer and / or the second layer and metal debris is established and stable trapping of the latter is provided.

[0183] However, the reduction of the speed of the debris can be achieved much more significantly by the additional layer 20, wherein the particles lose a large part of the kinetic energy due to extended deformation of the elastomer.

[0184] For the second layer 20 of the porous structure having a substantially bidimensional development la', the elastomer is selected from polymers with high molecular mobility, such as silicone elastomers. Both the porous structure having a substantially bidimensional development la according to the first embodiment and the porous structure having a substantially bidimensional development la' according to the second embodiment are clearly suitably sized.

[0185] The macro structure can be suitably designed to be based on distinct materials dimensionally shaped into different parts, each with specific features and functions. This will involve the use, as seen, of composite materials with distinct structural and functional properties in order to create a macro structure with the ability to trap small-sized debris.

[0186] The macro structure of both configurations of porous structure having a substantially bidimensional development la, la' can be designed by combining several modular parts that each cover a selected portion of the total impact surface, with an appropriate combination of areas with trapping characteristics and areas that provide mechanical stability and movement.

[0187] These are, therefore, modular macrostructures in which joining geometries and chemical-physical properties of the modular parts allow maximizing the performances of the system as a whole. These parts are designed using combinations of polymer composites with different matrices and fillers, each with a range of properties that synergistically interconnect with the properties of the other modular parts.

[0188] The modular structure further allows modifications in order to modulate specific performances, customizing the porous structure having a substantially bidimensional development based on needs and applications.

[0189] Depending on the type of orbit they are in, targets can have quite high speeds, even several tens of km / s.

[0190] Since these are particles with very high speeds and energies, the mechanical properties of the layers of composite material and the macro structure are therefore very important as they represent key elements of the development.

[0191] Generally speaking, according to the present invention, the porous structure having a substantially bidimensional development can be developed as a material with a reticulated or spun shape.

[0192] Advantageously, these can be provided and interwoven into a complex sub-micro and macro-deformable structure.

[0193] Part of the energy provided in the impact of the particles is recovered through deformation, which facilitates adhesion contact and avoids the elastic repulsion.

[0194] The modular design allows interconnected cells with different properties to interface with adjacent portions or cells, allowing the creation of an overall "intelligent" porous structure.

[0195] This interface allows the distribution of stress and energy, initially concentrated at the point of impact, to the adjacent portions or cells, starting a cascading process.

[0196] The entire macro structure, in fact, acts synergistically, allowing the energy initially concentrated at the point of impact to be managed and absorbed through structural deformation with elastic recovery of the deformed parts of the porous structure having a substantially bidimensional development.

[0197] This also guarantees an adequate contact time between the particles and the porous structure having a substantially bidimensional development thus facilitating the adhesion.

[0198] This feature is obtained either directly from the macro structure as in case of a monolayer in the porous structure 1 or setting up a first layer 2' of composite material and a second layer of composite material 20, when the porous structure 1' is multilayered.

[0199] Following unexpected events, malfunctions or impacts with particles of size and energy higher than expected, the macrostructure maintains its integrity.

[0200] The possibility of more or less localized yielding does not compromise the structural integrity.

[0201] As a result, the macrostructure must not collapse or shatter into smaller pieces as a whole, thus ensuring that no fragments are formed and dispersed.

[0202] This is typical of tough polymeric materials that never break into fragments if they are held above the glass transition temperature.

[0203] The macrostructure must be organized as it must not create hinderances to its movement within possible support systems.

[0204] It is therefore advantageous to produce a composite material in which the matrix is significantly deformable to dissipate energetic stress resulting from external mechanical stresses, such as extension, compression and bending.

[0205] It is in fact essential that the material of the load-bearing porous structure, both in case of a monolayer structure and in case of a multilayer structure, the polymer of the matrix, possibly added with a polymerization agent, has a glass transition temperature below the working temperature, thus guaranteeing a specific degree of flexibility and therefore impact resistance.

[0206] Said polymerization agent having a low glass transition temperature can be dispersed as a second micro-phase in the more rigid part or in the matrix of the first layer of composite material.

[0207] The deformation of these dispersed soft domains guarantees adequate absorption of an important part of the impact energy coming from the debris characterized by high kinetic energy.

[0208] This will prevent the endurance of the entire porous structure from being compromised by damage to the system during the deformation movement and will reduce, through dissipation, part of the impact energy by external objects.

[0209] In case of space applications, it must be considered that the space environment offers extreme working conditions. In space, in fact, there are many types of radiations which are generally high energy radiations, such as ultraviolet radiation, X-rays, gamma rays and cosmic rays, notable differences in temperature between the part exposed to solar radiation and that in the shade or, in the lower orbits, presence of atomic oxygen.

[0210] All these features make the space environment a very complex place for the operational life of materials.

[0211] The structural features and the intrinsic properties of the material do not change and are not compromised by the specific characteristics of an extreme working environment.

[0212] The material and the macro structure are able to work in extreme environmental conditions, such as those in space, and are not modified or do not deteriorate if exposed to (“outgassing”), solar radiation pressure, the presence of atomic oxygen, high temperature gradients or microgravity.

[0213] This requires that the macro structure is designed by synergistically combining the intrinsic properties of the selected materials and that the entire porous structure can intelligently interact with the various scenarios and stimuli given by the overall behavior. This means a predisposition for the material design to intelligent engineering.

[0214] Operating temperatures in environments, such as space, can have very large thermal gradient variations. Therefore, it is possible to have a change of many degrees in a relatively short time.

[0215] Advantageously, in order to prevent the macro structure stiffening at very low temperatures, as mentioned, the matrix of the first layer of composite material and the elastomeric part of the possible second layer of composite material must be formulated with a glass transition temperature lower than the minimum operating temperature.

[0216] In the first layer of composite material, said thermoplastic polymer has an elastic modulus between 1500 MPa and 5000 MPa, as calculated according to standard directive D3039 / ASTM D 3039M-08.

[0217] Alternatively, the macro structure has an elastic modulus with a high value even at temperatures higher than the operating temperatures, specifically an elastic modulus higher than 2000 Mpa, as calculated according to the standard directive D3039 / ASTM D 3039M-08.

[0218] Advantageously, to achieve this feature, high-melt fibers may be used in the first layer of composite material, in particular fibers with distortion temperatures higher than operating temperatures.

[0219] Preferably, in the first layer of composite material, said fibrous filler is made of fibers which have a tensile strength equal to or higher than 400 MPa, more preferably comprised between 2000 and 6000 MPa.

[0220] This double feature of good mobility to obtain adhesion and trapping of micro-debris and mechanical resistance to withstand the impact of debris can be obtained by formulating different parts of the macro structure with different features.

[0221] Advantageously, the second layer comprises elastomers having a glass transition temperature lower than - 150°C.

[0222] The glass transition temperature (Tg) can be calculated according to the standard directive ISO 11357- 1:2023.

[0223] All the selected polymers show an excellent thermo-stability up to 250- 300°C.

[0224] Finally, in Figures 4A and 4B, a device for trapping space debris 100 and 100', respectively, is illustrated, the device comprising a support structure 30 or 30', respectively, and the porous structure 1 for aerospace applications having a substantially bidimensional development, already described with reference to Figure 2, wherein the porous structure 1 having a substantially bidimensional development is connected to said support structure.

[0225] In particular, in these exemplary and non-limiting embodiments, the support structure 30 is a simple satellite that is moved in orbit, connected through a plurality of rods, preferably in carbon fiber, to the porous structure, so as to place it in an arrangement which is suited to collect the debris particles. In Figure 4A, a so-called "kite" deployment mode is provided, while in Figure 4B a so-called "parachute" deployment mode is provided. Nothing prevents the skilled person from providing a different support structure.

[0226] With reference to the device 100, the deployment of the porous structure 1 for the trapping of particles dispersed in space will require its transport in space vehicles.

[0227] The size of the porous structure is variable depending on various applications of the invention based on specific needs and it can therefore be scaled in this way and routinely by a person skilled in the art, varying from a few meters to many meters.

[0228] The final shape depends on the operational mission configuration, the result of the mission analysis and the result of the final output after the material development.

[0229] In order to be contained within an assigned transport space and for operational purposes, the macro structure must be foldable.

[0230] Therefore, it may be necessary to fold the porous structure 1 into a dedicated compartment in the satellite so that the porous structure 1 can easily be transported. Once the system has been stabilized in orbit, it is possible to deploy the porous structure having a substantially bidimensional development so that it becomes operational.

[0231] The weight of the macro structure is an important parameter, since lightness is crucial both for the operation of the system in orbit and for its transport.

[0232] During the operational mission, especially in the space transport step, the macrostructure is exposed to a high degree of stress, for example due to the launch system.

[0233] In addition to high acceleration, one of the major stresses during a space launch is vibration.

[0234] Therefore, the porous structure 1 and the layers of composite material that can compose it must be able to structurally withstand strong vibrations, without showing any type of yielding or collapse that could compromise the correct operation of the material.

[0235] Furthermore, there must be no structural resonances in the macro structure that compromise the connections between the various components and phases of the composite material or between the various components and interfaces of the entire porous structure having a substantially bidimensional development.

[0236] A priority feature is also sustainability and, thanks to the formulation of composite materials and intelligent engineering that allow the use of low- cost starting components and by minimizing the use of more expensive parts, it is possible to also adequately take into account the concept of circular economy.

[0237] One of the main functions of the material is to permanently trap smallsized debris or fragments, many of which may be made of metal alloys and compounds. It is therefore possible to develop, by means of the device 100 according to the invention, extraction properties of the collected material in order to be able to recycle it.

[0238] The same porous structure having a substantially bidimensional development, once its operational mission has been completed, can be recovered and recycled, having adopted components suitable for reuse or recirculation in the production of new components.

[0239] Specifically, it is possible to provide both mechanical recycling and chemical recycling of the polymeric materials used in the production of a porous structure having a substantially bidimensional development and the production of new objects which are not necessarily usable in the space environment.

[0240] If it is not possible to recycle the used materials, it is alternatively possible to allocate what is recovered to the production of energy using the aforementioned materials as raw material.

[0241] Furthermore, advantages are immediately recognizable in the structures 1, 1', in terms of their ability to structurally withstand high energy shocks without degrading and in terms of their ability to trap and capture debris without letting it detach.

[0242] Furthermore, as previously mentioned, the "intelligent" ability to react and manage physical stimuli will allow the predisposition for an efficiency and optimization of the entire system. The modular structure has various advantages both for the specific purpose of particle trapping, but also for the ease of customization of the system, allowing changes in properties and extension of performances, based on specific needs.

[0243] Still advantageously, the solution according to the present invention guarantees a high efficiency of collection of small-sized debris.

[0244] Furthermore, advantageously, the present invention is particularly suitable for the space field thanks to the mechanical and thermal resistance features as well as weight and size features in line with the mission requirements.

[0245] A further advantage is also represented by the fact that the present solution can be adapted and customized according to specific needs.

[0246] Finally, an advantage of the present invention is given by the fact that the porous structure having a substantially bidimensional development la, la' of the present invention can also be adopted in different fields with needs similar to the properties provided by the porous structure having a substantially bidimensional development la, la' made with the related specific material.

[0247] It will be apparent to those skilled in the art that modifications and variations, all falling within the scope of the invention defined by the attached claims, can be made to the porous structure for aerospace applications having a substantially bidimensional development, to its use and to the related device described above according to the present invention.

[0248] For example, nothing prevents, as seen above, the adoption of different additives to give further specific properties for different needs to the porous structure having a substantially bidimensional development la, la' according to the invention.

Claims

CLAIMS1. A porous structure (1, 1’) for aerospace applications having a substantially bidimensional development (la, la’), comprising a first layer (2, 2’) of composite material and, optionally, a second layer (20) of composite material, wherein said first layer (2, 2’) of composite material comprises a polymer matrix, a first fibrous filler (3, 3’) and a second filler (4, 4’), said polymer matrix being a thermoplastic polymer, wherein said second layer (20) of composite material is coupled to said first layer (2, 2’) of composite material and comprises a non-crosslinked elastomer and a third filler, wherein said second filler (4, 4’) and / or said third filler is in the form of a nano-filler and / or of a micro-filler, and wherein said first layer (2, 2’) of composite material or said second layer (20) of composite material has an average pore diameter lower than 1 mm, as calculated according to the standard directive ISO / TS 21383:2021.

2. The porous structure (1, 1’) for aerospace applications having a substantially bidimensional development (la, la’) according to claim 1, wherein said first layer (2, 2’) of composite material or said second layer (20) of composite material has an average pore diameter comprised between 20 nm and 5 gm, as calculated according to the standard directive ISO / TS 21383:2021.

3. The porous structure (1, 1’) for aerospace applications having a substantially bidimensional development (la, la’) according to claim 1, wherein said thermoplastic polymer is a polyester, a polyester copolymer, polyaryletherketone, a polyaryletherketone co-polymer or any combination thereof.

4. The porous structure (1, 1’) for aerospace applications having a substantially bidimensional development (la, la’) according to claim 3, wherein said thermoplastic polymer is a polyester, preferably a semiaromatic or aromatic polyester, more preferably selected from polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, a copolymer thereof or any combination of the foregoing.

5. The porous structure (1, 1’) for aerospace applications having a substantially bidimensional development (la, la’) according to anyone of the preceding claims, wherein in said first layer (2, 2’) of composite material said thermoplastic polymer has an elastic modulus between 1500 MPa and 5000 MPa, as calculated according to Standard Directive D3039 / ASTM D 3039M-08.

6. The porous structure (1, 1’) for aerospace applications having a substantially bidimensional development (la, la’) according to anyone of the preceding claims, wherein in said first layer (2, 2’) of composite material said first fibrous filler (3, 3’) is in the form of a lattice weave, said lattice weave being embedded in the polymer matrix of the first layer (2, 2’).

7. The porous structure (1, 1’) for aerospace applications having a substantially bidimensional development (la, la’) according to anyone of the preceding claims, wherein said first fibrous filler is selected from a carbon fiber, high modulus polypropylene (HMPP) fiber, ultra-high molecular weight polyethylene (UHMWPE) fiber, silicon carbide fibers, cellulose-based fibers or any combination thereof.

8. The porous structure (1, 1’) for aerospace applications having a substantially bidimensional development (la, la’) according to anyone of the preceding claims, wherein said second filler (4, 4’) and / or said third filler is selected from the group comprising a nano-structured carbon allotrope, silica nano-particles, lamellar silica, AI2O3 micro-particles, AI2O3 nano-particles, aluminosilicate nano-inclusions or any combination thereof.

9. The porous structure (1, 1’) for aerospace applications having a substantially bidimensional development (la, la’) according to anyone of the preceding claims, wherein said second filler (4, 4’) is present in the first layer (2, 2’) of composite material in an overall quantity comprised between 1% and 10% by weight on its total weight and / or said first layer of composite material has a density not greater than 1.5 g / cm3.

10. The porous structure (1, 1’) for aerospace applications having a substantially bidimensional development (la, la’) according to anyone of the preceding claims, wherein in said second layer (20) of composite material said non-crosslinked elastomer is selected from thermoplastic polyurethane, silicone elastomers or any combination thereof.

11. The porous structure (1, 1’) for aerospace applications having a substantially bidimensional development (la, la’) according to anyone of the preceding claims, wherein said thermoplastic polymer has a glass transition temperature (Tg) lower than 120°C, preferably lower than - 140°C, more preferably lower than - 160°C, as calculated according to the standard directive ISO 11357- 1:2023, or wherein said first layer (2, 2’) of composite material comprises a polymerization agent having a glass transition temperature (Tg) lower than 120°C, preferably lower than - 140°C, more preferably lower than - 160°C, as calculated according to the standard directive ISO 11357- 1:2023.

12. The porous structure (1, 1’) for aerospace applications having a substantially bidimensional development (la, la’) according to anyone of the preceding claims, wherein said first layer (2, 2’) of composite material is at least partially coated with an adhesive coating, preferably said adhesive coating being made of epoxy adhesives and / or thermoplastic adhesives.

13. The porous structure (1, 1’) for aerospace applications having a substantially bidimensional development (la, la’) according to anyone of claims 1- 10, wherein said non-crosslinked elastomer has a glass transition temperature (Tg) lower than 120°C, preferably lower than -140°C, more preferably lower than - 160°C, as calculated according to the standard directive ISO 11357- 1:2023.

14. The porous structure (1, 1’) having a substantially bidimensional development (la, la’) according to anyone of preceding claims 1- 13, wherein said porous structure is made of a plurality of portions, which are connected to each other, wherein each portion of said plurality of portions comprises said first layer (2, 2’) of composite material and, optionally, said second layer (20) of composite material and wherein each portion of said plurality of portion has a geometry and / or size which is different from the geometry and size of the adjacent portion of said plurality of portions and / or wherein in each portion of said plurality of portions the composition of said first layer (2, 2 j of composite material and, if present, of said second layer (20) of composite material varies according to the composition of the first layer (2, 2 j of composite material and, if present, of the second layer (20) of composite material of the adjacent portion of said plurality of portions.

15. Use of the porous structure (1, lj for aerospace applications having a substantially bidimensional development (la, laj according to anyone of claims from 1 to 14 in aerospace field, preferably for trapping space debris having a size lower than around 1 cm.

16. Device for trapping space debris (100, 100 j comprising a support structure (30, 30 j and the porous structure (1, lj for aerospace applications having a substantially bidimensional development according to anyone of claims from 1 to 14, said porous structure (1, lj having a substantially bidimensional development (la, laj being connected to said support structure (30, 30 j.

Images