METHOD FOR MANUFACTURING AN INTERIOR FEATURE FOR AN AIRCRAFT CAPACITY

Abstract

The invention relates to a laminated panel (20) comprising at least one core (26) sandwiched between at least two multilayer structures (28) comprising at least one non-woven layer (24) made from fiber scraps (22), in particular carbon fibers, and a binder, in particular thermoplastic or thermosetting. Figure for the abstract: Fig. 2

Description

Title of the invention: METHOD FOR MANUFACTURING A FITTING ELEMENT FOR AN AIRCRAFT CABIN Technical field of the invention

[0001] The invention relates to the technical field of fitting elements for aircraft cabins, such fitting elements being, for example, seats or seat shells. Technical background

[0002] The use of composite materials for the production of fitting elements for an aircraft cabin is well known. Such a material generally comprises fibers embedded in a polymer matrix. It is, for example, known to use glass fibers, carbon fibers, etc.

[0003] Carbon fiber consumption has increased significantly over the past ten years. Production has adapted to meet the growing demand.

[0004] Mainly used in composite structures, carbon fibers are widely used in the production of woven composite material parts in the aeronautical field, in particular woven composite blades for turbojets.

[0005] During their manufacture, layers of warp and weft threads are released as a preform of the composite material part is created, in order to achieve the different desired thicknesses. When the preform is released from the loom, an operation of cutting the warp and weft floats is carried out. The cut carbon threads then become scraps from the weaving process.

[0006] Thus, carbon fiber scraps represent a potentially significant volume across all production plants.

[0007] Furthermore, the carbon fiber scraps have mechanical performance that is still intact, because they have not been stressed. They can therefore be reused for the manufacture of new parts in composite materials.

[0008] However, until recently, carbon fiber scraps were practically not recovered. Indeed, although reprocessing channels for such carbon fiber scraps have developed, they are saturated with demand, particularly from the automotive industry.

[0009] Carbon fiber scraps are therefore not highly valued and outlets for the reuse of such fibers are still underdeveloped. They are mostly pyrolyzed then ground into powder constituting fillers for primers, paints or thermoplastic materials.

[0010] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states.

[0011] In particular, an ambitious standard applies both to new types of aircraft and those in circulation requiring the implementation of technological solutions in order to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.

[0012] Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft.

[0013] The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-consuming, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental consequences with the aim of improving the energy efficiency of aircraft.

[0014] The research and development work supported focuses in particular on lightening the devices, in particular through the materials used and the lightened on-board equipment.

[0015] It was therefore considered to recover carbon fiber scraps in order to set up a new sector. In this regard, research and development efforts have made it possible to develop a semi-finished recycling product based on carbon fiber scraps and a process for manufacturing such a product.

[0016] The product is in the form of a roll of a strip or a non-woven layer comprising scraps of carbon fibers and a binder ensuring the cohesion of the fibers between them and the holding of the strip.

[0017] However, to date, no measures aimed at exploiting such a product have been undertaken. The invention therefore aims to provide a method for manufacturing an element for fitting out an aircraft cabin, by recycling carbon fiber scraps.

[0018] To this end, the invention is the result of technological research aimed at very significantly improving the performance of aircraft and, in this sense, contributes to reducing the environmental impact of aircraft. Summary of the invention

[0019] For this purpose, the invention relates to a laminated panel comprising at least one core interposed between at least two multilayer structures. More specifically, the multilayer structures comprise at least one non-woven layer based on fiber scraps, in particular carbon fibers, and a binder, in particular thermoplastic or thermoset sand.

[0020] The invention thus proposes to recover fiber scraps, such as carbon fibers, and thus to recycle them. The invention therefore makes it possible to produce development elements from recycled material, which is particularly advantageous from an environmental and economic point of view.

[0021] The recycling of noble aeronautical material, such as carbon fibers, makes it possible to have an isotropic or quasi-isotropic non-woven structure, particularly in the plane, with properties similar to those produced from a woven structure, for example in glass fibers, while significantly reducing the mass of the product.

[0022] In the present description, the term "furnishing element" must be understood as being an element used to furnish, for example to furnish and / or to dress an aircraft cabin. It may, for example, be a seat, a part of a seat, a trim panel and / or a storage compartment, etc.

[0023] Furthermore, in the present description, the term “laminated panel” must be understood as being a panel composed of a stack of several layers, that is to say a so-called “sandwich” panel. The number of layers is not limiting.

[0024] The panel may comprise at least one core, in particular two or three for example, at least one multilayer structure, in particular two or more multilayer structures. By definition, the multilayer structure may comprise several superimposed layers.

[0025] Furthermore, in the present description, the term "non-woven layer" must be understood as being a layer composed of fibers which are not woven together and which have a random orientation in the non-woven layer. The fibers of the non-woven layer are bound together by at least one binder, a binding material and / or a matrix, in particular a thermoplastic matrix, which ensures a certain cohesion of the non-woven layer.

[0026] The present invention may include other features, described in the following, which may be considered independently or in combination with each other: - the core comprises a cellular structure, in particular a honeycomb structure, and / or a porous structure, in particular a foam; - the fiber scraps, in particular carbon fibers, have a length less than or equal to 100mm, in particular between 5mm and 50mm, in particular between 12.5mm and 25mm; - the non-woven layers of the structures are identical to each other, in particular having an identical composition and / or thickness;

[0027] — the multi-layer structure comprises between two and eight non-woven layers; - the laminated panel comprises at least two cores, one of the mul- structures layers being located between the souls;

[0028] — the laminated panel comprises at least three multi-layer structures, one of the multi-layer structures being located between the cores and the other two multi-layer structures being located on either side of the cores; - the core has a thickness between 5mm and 50mm, in particular between 5mm and 30mm; - the non-woven layer of the multi-layer structure has a thickness of between 0.1 mm and 0.6 mm, in particular between 0.2 mm and 0.4 mm; and / or - the multi-layer structure comprises, in particular between two adjacent layers, a layer of adhesive.

[0029] The present invention also relates to a fitting element for an aircraft cabin, such as a seat element, in particular a shell, for example a seat, a seat, a backrest, an armrest and / or a shelf.

[0030] More particularly, the fitting element comprises at least one laminated panel as described previously.

[0031] The present invention also relates to a method of manufacturing a fitting element, in particular for an aircraft cabin, comprising at least: a. a step of producing and shaping a laminated panel comprising at least one core inserted between at least two multilayer structures, and b. a step of producing the fitting element.

[0032] More particularly, the multilayer structures comprise at least one non-woven layer comprising scraps of fibers, in particular carbon fibers, and a binder, in particular thermoplastic or thermosetting.

[0033] The present invention may include other features, described in the following, which may be considered independently or in combination with each other: - during the production and shaping step a), the non-woven layer is covered with at least one layer of adhesive; - the non-woven layer covered with the adhesive layer undergoes a baking treatment to pre-bond the non-woven layer; - during the production and shaping stage a), the multi-layer structures and the core are stacked; - the multi-layer structures and the stacked core undergo a cooking treatment, in particular under vacuum and / or under press; - during the production and shaping stage a), the multi-layer structures and the core are cut, stacked and / or pre-glued;

[0034] — the non-woven layer is formed from a thermoplastic binder;

[0035] — the non-woven layer is consolidated prior to the production and installation step shaped to form a plate; and / or - the non-woven layer is formed from offcuts of pre-impregnated fibers with a binder, in particular thermosetting, prior to the production and shaping step a), to form a skin.

[0036] In the present description, the term “plate” must be understood as being an element having a certain rigidity and therefore a certain strength, and the term “skin” must be understood as being a relatively supple and / or flexible element.

[0037] Furthermore, the manufacturing method according to the invention, which is particularly advantageous for the purpose of reducing the environmental impact of aircraft, relates to a fitting element for an aircraft cabin, such as a seat element, in particular a shell, a seat, a backrest, an armrest and / or a shelf, obtained by a manufacturing method as described above. Brief description of the figures

[0038] The present invention will be better understood and other objects, characteristics and advantages of the invention will appear more clearly on reading the following description, comprising examples of embodiments of development elements presented as non-limiting examples which may serve to complete the understanding of the present invention and the description of its embodiment and, where appropriate, contribute to its definition. This detailed description is made with reference to the appended figures, in which: - [Fig.l] [Fig.l] is a schematic perspective view of a seat shell made from a laminated panel; - [Fig.2] [Fig.2] are schematic views illustrating stages of a manufacturing method according to the invention; - [Fig.3] [Fig.3] is a schematic sectional view illustrating a laminated panel produced according to a first embodiment of the manufacturing method according to the invention; - [Fig.4] [Fig.4] is a schematic sectional view illustrating a panel laminate produced according to a second embodiment of the manufacturing method according to the invention; and - [Fig.5] [Fig.5] is a schematic sectional view illustrating part of a fitting element produced by the manufacturing method according to the invention. Detailed description of the invention

[0039] [Fig.l] is a schematic perspective view of a portion of a furnishing element 10, such as a seat shell 12, made from a laminated panel.

[0040] More particularly, [Fig.l] represents the part of the fitting element 10 of an aircraft cabin, and in particular the shell 12 of a passenger seat.

[0041] The shell 12 comprises - a seat part, comprising a backrest 14 and armrests 16, and - a shelf portion 18, extending on one side of the seat portion, in particular in the extension of one of the armrests 16.

[0042] Such a type of shell 12 makes it possible in particular to produce a seat for “business” or “first” class.

[0043] According to the invention, the shell 12 is formed from a laminated panel produced and shaped by a manufacturing method according to the invention.

[0044] The manufacturing process essentially comprises at least two steps, consisting of:

[0045] a) a step of producing and shaping a laminated panel comprising at least one core inserted between at least two multilayer structures, and

[0046] b) a step of producing the fitting element 10.

[0047] The particularity of the manufacturing method according to the invention lies in the fact that each of the multilayer structures of a laminated panel comprises non-woven layers based on fiber scraps, in particular carbon fibers and a binder, in particular thermoplastic or thermosetting.

[0048] In the present description, the term “binder” must be understood as being an element making it possible to ensure cohesion of the non-woven layer, such as a binder material and / or a matrix.

[0049] The manufacturing method according to the invention aims to recycle fiber scraps in order to manufacture the fitting element 10, for example of the type illustrated in [Fig.l].

[0050] [Fig.2] comprises schematic views illustrating steps of the manufacturing method according to the invention.

[0051] More particularly, [Fig.2] shows in a simple and schematic manner the different phases of construction of a laminated panel 20. In particular, [Fig.2] shows sub-steps of step a) of production and shaping of a laminated panel of the manufacturing method.

[0052] The steps of the manufacturing method according to the invention aim at manufacturing the fitting element 10, in particular for an aircraft cabin.

[0053] Image 2a of [Fig.2] shows fiber scraps 22, in particular carbon fiber scraps, recovered in bulk, for example after the manufacture of composite material parts in the aeronautical field as mentioned above.

[0054] The fiber scraps 22 are used to produce a non-woven layer 24, such as represented in image 2b of [Fig.2]. For this, the manufacturing process can provide at least:

[0055] i) a disentangling sub-step, during which the fibers 22, in particular the carbon fibers, are disentangled and can be mixed with a binding material;

[0056] ii) a dispersion sub-step, during which a dry air flow is used to disperse the fibers 22;

[0057] iii) a manufacturing sub-step, during which a fiber mat is produced, the fiber mat comprising the fibers 22, air and the binding material; and

[0058] iv) a calendering sub-step, during which the fiber mat is hot calendered to a temperature greater than or equal to the glass transition or melting temperature of the binder material, so as to produce a semi-finished recycling product in the form of a roll of non-woven strip or layer 24.

[0059] The disentangling sub-step i) consists of disentangling the fibers 22 and, optionally, mixing them with a binder material, in particular at low temperature. The binder material may be in the form of particles and / or fibers, for example of a resin-based thermoplastic type, such as polyethylene (PE), polypropylene (PP) or in a PE-PP copolymer.

[0060] The disentangling sub-step i) may further comprise a mixture of the fibers 22, in particular carbon fibers, with thermoplastic fibers, such as polyetherimides (PEI), poly(phenylene sulfide) (PPS) or polycarbonate (PC).

[0061] The thermoplastic fibers preferably have a glass transition or melting temperature higher than that of the binder material.

[0062] The calendering sub-step iv) is carried out at the glass transition or melting temperature of the binder material and is intended not to soften the thermoplastic fibers intended to be softened during subsequent processing.

[0063] In the absence of such thermoplastic fibers, the non-woven layer 24 can subsequently be used in combination with any resin, in particular a thermosetting or thermoplastic resin, in particular via impregnation of the bath, hot-melt, film or powdering type, etc.

[0064] The dispersion sub-step ii) and the production sub-step iii) of the manufacturing method according to the invention make it possible, using a flow of dry air, to disperse the fibers 22 and to produce a fiber mat comprising the fibers 22, air and the binding material.

[0065] The calendering sub-step iv) makes it possible to produce the semi-finished recycling product in the form of a roll of non-woven strip or layer 24.

[0066] Image 2c of [Fig.2] shows the laminated panel 20 obtained during the manufacturing process according to the invention.

[0067] The laminated panel 20 comprises: - at least one core 26, - at least one multi-layer structure 28.

[0068] The laminated panel 20 may comprise at least two multilayer structures 28 separated from one another, or from each other by the core 26 or one of the cores 26. Thus arranged, the core 26 is interposed between two multilayer structures 28.

[0069] The core 26 may comprise a honeycomb structure, in particular a honeycomb, and / or a porous structure, in particular a foam. In the example of [Fig. 2], the cores 26 all comprise a honeycomb structure.

[0070] The core 26 preferably has a thickness of between 5mm and 50mm, in particular of between 5mm and 30mm,

[0071] The multilayer structure 28 comprises a stack of several layers, in particular several non-woven layers 24 of fiber scraps 22, in particular carbon fibers, and possibly a binder, for example made of thermoplastic or thermosetting material.

[0072] The fiber scraps 22 generally have a length less than or equal to 100 mm, and in particular between 5 mm and 50 mm, in particular between 12.5 mm and 25 mm.

[0073] According to an exemplary embodiment, the non-woven layers 24 of the multi-layer structure 28 are identical to each other. It is thus possible to use the same roll of non-woven layers 24, to cut it to form several non-woven layers 24 and to use the cut non-woven layers 24 to produce the multi-layer structure 28.

[0074] According to various embodiments, the multilayer structure 28 may, for example, comprise between two and eight non-woven layers 24.

[0075] The non-woven layer 24 of the multilayer structure 28 has, in particular, a thickness of between 0.1 mm and 0.6 mm, in particular of between 0.2 mm and 0.4 mm.

[0076] Furthermore, the non-woven layer 24 may be associated with a binder or a binding material, in particular of the thermoplastic or thermosetting type. For this purpose, the thermoplastic binder may, for example, be poly(phenylene sulfide) (PPS), polyetherimides (PEI), polyetheretherketone (PEEK), polycarbonate (PC), polyethersulfone (PESU) or polyphenylsulfone (PPSU°.).

[0077] The thermosetting binder may, for example, be an epoxy resin, a phenolic resin, a furfuryl alcohol-based resin or perfluoroalkoxy.

[0078] The non-woven layer 24 may have a surface density of between 100g / m2 and 1000g / m2, in particular of between 200g / m2 and 600g / m2.

[0079] [Fig. 3] is a schematic sectional view illustrating the laminated panel 20 produced according to a first embodiment of the manufacturing method according to the invention.

[0080] More specifically, [Fig. 3] shows an exploded view of the laminated panel 20 used in the context of the present invention. The laminated panel 20 comprises a core 26 interposed between two multilayer structures 28 each comprising two non-woven layers 24 of fiber scraps 22, in particular carbon fibers.

[0081] In the embodiment of [Fig. 3], the binder used in the non-woven layer 24 is in particular thermosetting.

[0082] Alternatively, the non-woven layer24 may comprise a thermoplastic plate, in particular manufactured beforehand.

[0083] The fiber scraps 22 are, in particular, pre-impregnated with the binder, in particular thermosetting, prior to the step of producing and shaping a) the laminated panel 20, to form a skin, that is to say a relatively supple and flexible element.

[0084] In the example of [Fig.3], the multilayer structure 28 is therefore composed of at least two pre-impregnated skins, previously manufactured.

[0085] The manufacture of the laminated panel 20 of [Fig. 3] may comprise at least: - a step of cutting a core, during which a structure, in particular a honeycomb structure, is cut according to desired dimensions to form a core 26, - a layer cutting step, during which at least one non-woven layer 24 comprising fiber scraps 22 is cut to desired dimensions, - a draping step, during which the non-woven layer 24 is draped, manually or automatically, over the core 26, - a cooking step, during which a cooking cycle, in particular under vacuum, in an oven, press and / or autoclave, is carried out, in order to compact and consolidate the laminated panel 20 - a demolding step, during which the laminated panel 20 is demolded.

[0086] The cooking cycle used in the cooking step depends on the composition of the matrix and / or the binder which impregnates the fibers.

[0087] In particular, the firing is carried out at a temperature greater than or equal to the glass transition or melting temperature of the matrix and / or the binder.

[0088] Depending on the nature of the matrix and / or the binder or to improve the cohesion of the non-woven layer 24 in the multi-layer structure 28, it may be useful or advantageous to provide a layer or sheet of adhesive 30 between the non-woven layers 24.

[0089] In addition or as an alternative, it may be useful or advantageous to provide a layer or sheet of adhesive 30 between the multilayer structure 28 and the core 24.

[0090] The multilayer structure 28 may then comprise, between two adjacent non-woven layers 24 of fiber scraps 22, a layer or sheet of adhesive 30.

[0091] [Fig.4] is a schematic sectional view illustrating the laminated panel 20 produced

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[0101] according to a second embodiment of the manufacturing method according to the invention. More specifically, [Fig.4] illustrates an alternative embodiment of the manufacturing method in which at least layers or sheets of adhesive 30 are used. The laminated panel 20 comprises a core 26 interposed between two multi-layer structures 28 respectively comprising two non-woven layers 24 of fiber scraps 22 and at least one layer of adhesive 30. The adhesive layer 30 may be disposed between two non-woven layers 24 and / or the non-woven layer 24 and the core 26. In the embodiment of [Fig.4], the binder used in the non-woven layer 24 is, in particular, thermoplastic. The non-woven layer 24 is, in particular, consolidated, that is to say stiffened, prior to the step of producing and shaping a) the laminated panel 20, to form a plate, in particular a laminated plate. The manufacture of the laminated panel 20 of [Fig.4] may comprise at least: - a step of carrying out a first cooking cycle, during which at least one layer of adhesive 30 is pre-glued onto one face of the consolidated non-woven layer 24. Consequently, the manufacture of the laminated panel 20 of [Fig.4] can comprise at least: - a step of cutting a core, during which a structure, in particular a honeycomb structure, is cut according to desired dimensions to form a core 26, - a layer cutting step, during which at least one consolidated non-woven layer 24 comprising fiber scraps 22 is cut to desired dimensions, - a draping step, during which the consolidated non-woven layer 24 is draped, manually or automatically, over the core 26, - a cooking step, during which a cooking cycle, in particular under vacuum in an oven, press or autoclave, is carried out, in order to compact and consolidate the laminated panel 20 - a demolding step, during which the laminated panel 20 is demolded. The cooking cycle used in the cooking stage depends on the composition of the matrix and / or the binder that impregnates the fibers. The pre-bonding may, in particular, be carried out at a temperature greater than or equal to the glass transition or melting temperature of the adhesive layer 30. In particular, the baking is carried out at a temperature greater than or equal to the glass transition or melting temperature of the adhesive layer 30, of the matrix and / or binder.

[0102] It is then understood that during the step of producing and shaping a) the laminated panel 20, each of the non-woven layers 24 of fiber scraps 22 is covered with at least one layer or sheet of adhesive 30. Subsequently, the assembly thus formed undergoes a cooking treatment to carry out pre-bonding of each of the non-woven layers of fiber scraps 22.

[0103] In the manufacturing processes of the laminated panel 20 of Figures 3 and 4, it is further understood that, during the production and shaping step a), the non-woven layer(s) 24 and the core(s) 26 are stacked. Subsequently, the assembly thus formed undergoes a cooking treatment, in particular under vacuum, in an oven, press and / or autoclave.

[0104] [Fig. 5] is a schematic sectional view illustrating a portion of the fitting element 10 produced by the manufacturing method according to the invention. More specifically, [Fig. 5] is a schematic sectional view of the fitting element 10 comprising the laminated panel 20 according to the invention.

[0105] The laminated panel 20 may be machined to produce through-holes 32 and / or housings 34. The through-holes 32 and / or the housings 34 are capable of allowing mounting and / or fixing of different elements such as: - a metal reinforcing element 36; in particular housed in a housing 34 of a peripheral edge of the laminated panel 20, - a filling element 38; in particular housed in a housing 34 of a peripheral edge of the laminated panel 20, - an edging element 40 / finishing element; in particular fixed to the filling element 38, in order to achieve a desired finish of the laminated panel 20, and / or - an insert 42; in particular engaged and fixed in an orifice 32.

[0106] Furthermore, a metal plate 44 can be fixed, in particular by means of an adhesive film 46, on one of the faces of the laminated panel 20.

[0107] The present invention provides several advantages, including: - a reduction in material losses (particularly carbon fibers) during the composite manufacturing cycle in the aeronautics sector, - recycling of this material for the interior fittings of an aircraft, such as airplane seats, - a reduction in the mass of the interior fittings thus obtained and, consequently, a reduction in the carbon footprint linked to air transport, - etc.

Claims

Claims

1. Laminated panel (20) comprising at least one core (26) interposed between at least two multilayer structures (28), characterized in that the multilayer structures (28) comprise at least one non-woven layer (24) based on fiber scraps (22), in particular carbon fibers, and a binder, in particular thermoplastic or thermosetting.

2. Laminated panel (20) according to claim 1, in which the core (26) or comprises a cellular structure, in particular a honeycomb, and / or a porous structure, in particular a foam.

3. Laminated panel (20) according to claim 1 or 2, in which the fiber scraps (22) have a length less than or equal to 100mm, in particular between 5mm and 50mm, in particular between 12.5mm and 25mm.

4. Laminated panel (20) according to any one of the preceding claims, in which the non-woven layers (24) of the multi-layer structures (28) are identical to each other.

5. A laminated panel (20) according to any preceding claim, wherein it comprises at least two cores (26), one of the multi-layer structures (28) being located between the cores (26).

6. Laminated panel (20) according to any one of the preceding claims, wherein the core (26) has a thickness of between 5mm and 50mm, in particular between 5mm and 30mm, and / or wherein the non-woven layer (24) of the multi-layer structure (28) has a thickness of between 0.1mm and 0.6mm, in particular between 0.2mm and 0.4mm.

7. Laminated panel (20) according to any one of the preceding claims, in which the multilayer structure (28) comprises, in particular between two adjacent non-woven layers (24), a layer of adhesive (30).

8. Fitting element (10) for an aircraft cabin, such as a seat element, in particular a shell, a seat, a backrest, an armrest and / or a shelf, characterized in that it comprises at least one laminated panel (20) according to any one of the preceding claims.

9. Method of manufacturing a fitting element (10), in particular for an aircraft cabin, comprising at least: a. a step of producing and shaping a laminated panel (20) comprising at least one core (26) interposed between at least two multilayer structures (28), and b. a step of producing the fitting element (10), characterized in that the multilayer structures (28) comprise at least one non-woven layer (24) comprising scraps of fibers (22), in particular carbon fibers, and a binder, in particular thermoplastic or thermosetting.

10. Manufacturing method according to claim 9, wherein, during the production and shaping step a), the non-woven layer (24) is covered with at least one layer of adhesive (30).

11. A manufacturing method according to claim 10, wherein the non-woven layer (24) covered with the adhesive layer (30) undergoes a baking treatment to achieve pre-bonding of the non-woven layer (24).

12. Manufacturing method according to any one of claims 9 to 11, wherein, during the production and shaping step a), the multilayer structures (28) and the core (26) are stacked.

13. Manufacturing method according to claim 12, in which the stacked multilayer structures (28) and core (26) undergo a cooking treatment, in particular under vacuum and / or under press.

14. Manufacturing method according to any one of claims 9 to 13, wherein, during the production and shaping step a), the multilayer structures (28) and the core (26) are cut, stacked and / or pre-glued.

15. Manufacturing method according to any one of claims 9 to 14, in which the non-woven layer (24) is formed from scraps of fibers (22) pre-impregnated with a binder, in particular thermosetting, prior to the production and shaping step a), to form a skin.

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