FR3001698A1 - Housing for car, has vegetable material sheet arranged between polymer material layers, where sheet is made from bamboo, beech, chestnut, ash, birch, oak, alder, eucalyptus, woodland pine, spruce, Douglas wood, larch or mahogany tree - Google Patents

Abstract

The housing (1) has a vegetable material sheet (2) arranged between polymer material layers, where the sheet is made from bamboo, beech, chestnut, ash, birch, oak, alder, eucalyptus, woodland pine, spruce, Douglas wood, larch or mahogany tree. The sheet is designed with thickness ranging between 0.5 to 1.2 mm. A reinforcement unit i.e. U-shaped central cross-piece, designed in a predetermined form is arranged on an internal surface of the housing and directed towards interior of a cockpit. The reinforcement unit is made from metallic material and covered with composite material. An independent claim is also included for a method for manufacturing a housing of a car.

Description

The invention relates to a vehicle pavilion based on natural materials.

The various researches carried out in the automotive field are aimed not only at the mechanical and economical improvement of use, but also at the aesthetic aspect, in particular concerning the so-called upper parts of a vehicle, such as the roof or the roof.

It is known to make a roof or pavilion vehicles translucent or transparent to obtain a good brightness inside the cabin. For this purpose, two types of materials are conventionally used. The first material is a mineral glass in the form of a laminate of two glass layers and a polyvinyl butyral (PVB) core layer, the second material being an organic glass in the form of a polycarbonate (PC) layer or poly (methyl methacrylate) (PMMA). The thicknesses are different according to the vehicles, and they are conventionally around 4 mm for the mineral glass and 6 mm for the organic glass, which allow to ensure a mechanical resistance and an acceptable protection in the majority of the cases of the cockpit, in case of accident. However, the roof or roof of these materials having such thicknesses have the disadvantage of having a weight such that it is likely to induce additional mechanical stresses, undesirable, on the other parts of the vehicle.

The use of natural materials in various parts of the vehicle confers a particular aesthetic appeal. Indeed, the vision of a natural material outside a vehicle usually encourages a person to look inside the vehicle to discover the existence of other pieces of the same material.

However, the use of such aesthetic materials must also ensure a real structural strength of the material and allow to obtain a good brightness inside the cabin. It is therefore necessary to respect and optimize the technical feasibility of the natural material, architecture and its use in the automotive field, in particular in the manufacture of a vehicle roof, in order to ensure sufficient resistance to various mechanical stresses, in particular torsion and bending. Indeed, to make compatible the solution of a roof made of natural material, it is necessary to determine the shapes and the arrangement of an element in this material constituting a roof or roof, because the latter is generally not planar but has a double longitudinal and transverse curvature with large possible radius values. The natural material must therefore be able to be adapted to meet this double curvature constraint, especially during a molding process at a temperature above room temperature. In addition, the use of natural materials in outdoor areas is constraining because such materials are subjected to extreme temperatures, UV radiation, weather conditions and cleaning. The invention aims to overcome at least one of these disadvantages by providing a motor vehicle roof of composite material comprising a plant material sheet interposed between at least two layers of polymer material, said composite material ensuring rigidity and robustness of said flag, said plant material being selected from the group consisting of bamboo, beech, chestnut, ash, birch, oak, alder, eucalyptus, Scots pine, fir, spruce , Douglas fir, larch, Red Ceddar wood, Ipe, iroko, bankirai, teak, mahogany and their mixture. The Applicant has shown, after studies and research, that among the natural materials, the plant materials of the invention met the requirements of robustness and mechanical resistance to torsional and flexural stresses of the vehicle and shocks, to ensure the protection of the cockpit. In addition, particularly importantly, the sheets of plant material have been chosen for their behavior appropriate to the double curvature stress during the making of the flag, advantageously by molding, because the effect of the temperature of the molding process results in optimum softening of the composite material, in particular vegetable matter. In the context of the invention, the plant materials are therefore wood species and / or grass plants, such as bamboo in its widest definition, that is to say the family of bambusoideae and more particularly of the bambuseae tribe.

The double curvature may be defined by a first curvature in a longitudinal direction (front / rear axis of a vehicle), and by a second curvature in a transverse direction, imparting a curved arrangement to the composite material.

Therefore, the fixed roof or pavilion of a vehicle is a good candidate for the application integrating these plant materials, because their vision is as interesting from the outside as from the inside (extra pavilion dressing). But this part is subject to structural constraints related in particular to the overall torsion of cash. In addition, the use of this composite material, based on the plant material of the invention, in the outer zone, avoids the premature degradation of the pavilion subjected to various climatic constraints. The Applicant has shown that bamboo best meets these requirements, and therefore proves to be the most preferred among the plant materials cited. In the context of the invention, such a material is also referred to as solid composite material. The leaf of plant material is interposed between at least two layers of polymeric material, each layer can then form a plate, and can therefore be a central layer between a first layer of said higher polymeric material, in contact with the external environment, and a second layer of so-called lower polymer material, in contact with the interior of the passenger compartment. It is not excluded to envisage that one or the other of the polymer layers may be formed of several polymer layers of different materials or not. The sheet of plant material, depending on its size and surface, can result classically from a juxtaposition of lamellae of different sizes depending on the nature of the plant materials, which can be joined together by the side edges, by usual means , according to a floor type parquet arrangement. According to embodiments, the sheet of plant material may be made by mixing various of these plant materials, that is to say that the sheet may comprise an alternation of lamellae of plant material of different nature. Advantageously, the sheet of plant material may have a thickness of between 0.5 mm and 3 mm, preferably between 1.2 and 3 mm, and may be formed of at least two sheets superposed one against the other of to form a glued lamellar compound. Alternatively, it can be envisaged that the lamellar compound comprises a superposition of leaves of different plant material. The use of plant materials according to the invention may furthermore have the advantage of using only such thicknesses, which makes it possible to limit the thicknesses of the layers of polymer material in the composite material, thereby reducing its mass, which its turn will impose only limited constraints on the various parts of the vehicle. Very advantageously, when the plant material is bamboo, it may then be possible to use a thickness of the sheet lying towards the lower limit of the range given above, typically between 0.5 and 1.2. mm, while maintaining the desired performance, all things being equal. The polymeric material of each of the at least two layers may be the same or different, and may preferably be selected from the group consisting of thermosetting resins, such as epoxy or acrylic resins, a PMMA type thermoplastic polymer, and their admixture. The polymeric material may preferably be transparent or translucent, possibly colored, in order to impart a desired aesthetic appearance. In particular, the polymer material is transparent, colored or not, so as to enhance the leaf of plant material. The two layers may advantageously have identical or different respective thicknesses whose values may be between 1.4 and 2 mm. Of course, the surface dimensions of the two layers may correspond classically to those of the sheet of plant material. The sheets of plant material may be fixed on the layers of polymer material by an adhesive having for example a thickness of between 0.1 mm and 0.3 mm. The adhesive may for example be of the polymer type, to avoid any risk of delamination of the composite material, without however altering the desired mechanical and aesthetic properties. The pavilion of the vehicle may advantageously have a total thickness, for example between about 4 mm and 7 mm, which may be less than that of a flag of the prior art made of organic glass or laminated glass, while presenting robustness and resistance to mechanical stresses (double curvature constraint during the manufacture of the roof) and to increased shocks compared with those of the prior art (organic and mineral glass).

In the context of the invention, even when the thicknesses of the composite material are greater than those of the materials of the prior art above, it is possible to obtain an advantageous gain in mass, that is to say that the flag obtained thanks to the composite material has a weight lower than that obtained with the materials of the prior art. The pavilion composite material of the invention is generally rectangular or square, whose surface can be curved, according to conventional designs, the size and size of which depend on the model of the vehicle.

It is not excluded to include on the flag thus obtained various layers of materials, such as protective varnishes or dyes or other, conventionally used in the field of the invention. According to embodiments, the motor vehicle roof may be entirely made of composite material of the invention.

According to this embodiment, a process for preparing the composite material may advantageously be a molding method consisting in injecting under low pressure a thermosetting resin into a mold on which a fibrous reinforcement has been previously arranged. Such a method may be a resin injection molding (RTM) process known per se. RTM liquid resin injection molding is a manual or semi-automated process that takes place between a rigid mold and counter-mold. The reinforcements, in the form of mats, of the fabric or preform type, are placed in the gap of the mold. The mold is then firmly closed and the catalyzed resin is injected inside under low pressure. It is advantageously used when the polymer material is a thermoplastic polymer, such as PMMA. Preferably, the process can be carried out at pressures between 1.5 and 4 bar. It is also possible to use a thermoforming process using pressures of between 1.5 and 6 bar, and pressures greater than 6 bar, causing disintegration of the sheets of plant material. The operating temperatures are at most 80 ° C, higher temperatures causing a browning of leaves of plant material. This thermoforming process is preferably implemented when the polymer material is thermosetting resin, such as epoxy resins or acrylic.

These methods can therefore use means of implementation to achieve a flag according to the desired forms, convex preferences. According to other embodiments, the pavilion of a motor vehicle may be made of composite material comprising areas devoid of leaves of plant material. According to this embodiment, the roof of composite material may have perforated zones, which consist solely of layers of polymeric material.

The perforated zones are not limited in size and size, provided that the composite material thus perforated renders the desired properties. Preferably, the flag can be separated into a plurality of surface areas, preferably two areas, identical or not in sizes and dimensions, where the composite material is devoid of leaves of plant material, the respective interzones, of variable size, and the edge-end zones of the roof may consist of solid composite material. The surface areas may be square and / or rectangular, in particular transparent, colored or not. The composite solid material, in the edge-end zones of the roof, may extend over distances advantageously between 5 and 10 cm, from an edge end of the length or width of the roof towards the interior of the roof. the surface of the pavilion. Interzones of solid composite material are usually in the form of strips, the length of which may correspond to the width of the flag and whose width may be between 5 and 10 cm. According to other embodiments, the perforated zones of the flag may be in the form of strips, which allow to define areas of solid composite material having for example a diamond shape, pentagonal, hexagonal, triangular, square, rectangular etc. . A method of manufacturing such a pavilion made of perforated composite material may be one of the two processes mentioned above, resin injection molding or thermoforming, however the resin injection molding process implemented with a thermoplastic polymer. being the least preferred because of the possible appearance of air bubbles in the perforated zones, which can come from plant materials.

Advantageously, another method of manufacturing a pavilion composite material may be based on the encapsulation of plant materials in a pure thermoplastic polymer, such as pure PMMA. The process can use monomer formulations of these thermoplastic polymers, such as methyl methacrylate (MMA), capable of cold polymerization. The advantageous aim of this process is to decompose the encapsulation of vegetable matter in several steps in order to overcome withdrawal problems. According to this embodiment, the method of manufacturing a motor vehicle roof of composite material according to the invention may comprise the following steps consisting of: 1) placing a sheet of plant material on a first layer of thermoplastic polymer material and performing, on a plurality of edge ends of the sheet, a frame comprising a film of a demouldable compound, 2) extending on the plurality of edge ends of the sheet an ambient temperature polymerizable adhesive solution comprising a polymerization catalyst for obtaining a solid adhesive film; 3) after completion of the polymerization reaction of step 2), covering the surface of the sheet with said polymerizable adhesive liquid solution, and 4) before completion of the polymerization reaction of step 3), attaching, on the surface of the sheet covered with said adhesive liquid solution, a second layer of thermoplastic polymer material, for obtaining the motor vehicle roof of composite material. According to step 1), the plant material sheet is first placed on a first thermoplastic polymer plate, such as PMMA, capable of having a thickness indicated above and a double curvature along a longitudinal and transverse axis. A frame can then be made around the polymer plate using, for example, a release film of polyimide. This frame may allow, according to embodiments, to contain the monomeric material, for example methyl methacrylate (MMA), during casting for the manufacture, by polymerization, of the polymer plates. According to preferred embodiments, the plant material sheet can occupy the entire surface of the first polymer layer. As a variant, the sheet of plant material may have dimensions smaller than that of the first polymer layer, so as to ultimately produce a flag made of composite material having perforated zones, as described above. In this case, the sheet of plant material is a set of a plurality of sheets of plant material of dimensions smaller than that of the first polymer layer, without classically exceeding its surface. Step 2) advantageously consists in spreading on the edge ends of the plant material sheet, advantageously around all the edges, a film of an adhesive solution of polymerizable glue at ambient temperature and conditions, typically in the open air. , preferably transparent. This makes it possible to encapsulate the edge ends of the plant material without applying stress on the latter. With this operation, the leaf of plant material can be maintained on the surface of the first layer of polymeric material. Advantageously, this polymerizable adhesive solution may be a solution, preferably viscous, of monomer of the thermoplastic polymer, such as methyl methacrylate (MMA). A polymerization catalyst, known to those skilled in the art, is preferably added at the time of the implementation of this step to obtain a film of polymerized adhesive which is in solid form and which can thus correspond to the thermoplastic polymer. The polymerization time is usually between 1 h and 2 h, at room temperature. It is possible to accelerate the polymerization process by annealing at typical temperatures of 50 ° - 80 ° C. After completion of the polymerization reaction of step 2), said polymerizable adhesive liquid solution comprising a polymerization catalyst is spread on the surface of said sheet and the surface of the sheet of plant material is covered, preferably the whole surface. According to this step 3), a new film of the same adhesive is produced as in step 2), the thickness of which is, for example, approximately 0.5 mm to 1 mm, on the surface of the film. vegetable matter. As before, the polymerization reaction takes place in the open air, that is to say that no stress is applied for the formation of the film of polymerized adhesive in solid form. The polymerization time is usually from 1 to 2 hours at room temperature, but it is preferable to wait about 24 hours before further handling. It is possible to accelerate the polymerization process at typical temperatures of 50 ° - 80 ° C, in order to obtain an optimally bonded product after a maximum of 5 hours. Step 4) is to fix a second plate of thermoplastic polymer material on the surface of the plant material sheet, which is covered with liquid adhesive solution, before the polymerization process is completed, that is to say say before the formation of a solid adhesive film. Conventionally, the second layer of thermoplastic polymer material may have a surface and thickness identical to the first layer. Advantageously, steps 2) and 3) can be performed concomitantly, because the plant materials according to the invention are resistant to encapsulation constraints. Depending on the manner in which the roof is manufactured, the first layer of polymeric material may be either the outermost layer, in contact with the external environment, or the innermost layer, towards the interior of the passenger compartment of the vehicle automobile. It is the same for the second layer of polymeric material, which is therefore complementary to the first layer.

This method may further include other conventional steps of depositing other protective layers or dyes on the first and / or second layer (s) of polymer material at the end of the process, or during any of the steps 1) at 4). The method may comprise, preferably after step 4), an additional step (step 5)) of adaptation of the edge ends of the flag to those of the ends of a roof frame adapted to receive said flag. According to advantageous embodiments, the flag composite material may further comprise one or more reinforcing means (s), of predetermined shape, intended (s) to improve the mechanical properties of strength and resistance to bending and to the torsion of the pavilion. They can usually be in the form of one or a plurality of strips extending from one side to the other over at least a portion of the flag width, advantageously over the entire width of the flag, that is to say according to a transverse axis, as defined previously. The reinforcing means generally have a constant section according to the curvature of the roof and can usually be fixed on the inner surface of the roof, on a roof frame and / or on a vehicle body. The thickness of this section can usually be between 3 mm and 7 mm. The reinforcing means may be in the form of a U-shaped band or an inverted, flared IC, or a crenel with rounded or non-rounded edges, the edge ends of which may be fixed on the inner surface of the roof in composite material, for example by gluing. Alternatively, the reinforcing means may be a strip in the form of a double U or inverted CI, flared, or a double slot with rounded edges or not. According to advantageous embodiments, the reinforcing means may be of vegetable material, and may be roof crossbars in the form of a glued laminated strip, plywood or a solid block machined plant materials. According to other implementations, the reinforcing means may be made of a metallic material, such as steel or aluminum or the like, the surface of which, preferably the visible external surface, is directed towards the interior of the passenger compartment, is covered, partially or totally, with the composite material of the invention. The composite material covering the surface of the reinforcing means may preferably be held at said surface by gluing or by mechanical holding means, such as screws, staples or rivets.

The reinforcement means may be fixed at the central zone of the flag, that is to say, share the flag in substantially two identical surface areas. The reinforcing means may also be secured to the body and / or the roof frame. Fixing the reinforcing means on the roof of composite material is similar to that implemented with a metal roof, and may preferably be adhesive means, for example lines of mastics wedging or appropriate glue. However, it is obvious to avoid that these fastening means are means such as screws or nails. The reinforcement means may define orifices located in the end zones in contact with the roof frame or the body of a vehicle, which are capable of receiving additional fastening means, such as screws, nails or rivets, to reinforce the maintenance of the reinforcement means to the roof frame or the said box. The flag composite material of the invention is generally not assembled directly on the vehicle body, but in a method where the flag is secured to a frame called "flag frame".

In principle, the roof of the invention can be fixed by means of attachment, for example by gluing, to the roof frame, the shape and nature of which are conventionally those of a metal roof frame for the manufacture of classical metal pavilions. The adhesives used can be those commonly used in the field of motor vehicles, for example a polyurethane-based adhesive. According to conventional embodiments, the edge ends of the roof can cooperate with lateral recesses of the roof frame and the surfaces of the edge ends can be held, by plating and gluing, on the surfaces of the walls of the frame. Alternatively, the edge ends of the flag can be bent so that said ends are positioned on the ends of the frame by the surface of the section of the roof, and can be secured for example by gluing. According to this arrangement, the roof surface is not integral or in contact with the surface of the frame, except at the ends. The empty space between the two respective surfaces, typically a few millimeters, may contain additional fastening means, such as glue, to reinforce the bonding already performed by the edge ends. The end joining zone may also be provided with a seal, of polymeric or metallic material, whose shape may be toric. However, for this attachment of the flag on the roof frame, it is preferably useful that the edge ends of the roof can be adapted or complementary to those of the roof frame. Alternatively, the roof edge ends may be bent so that said ends are positioned on complementary surfaces of the roof frame without necessarily having the surfaces provided in the end regions of the frame. According to another variant, the positioning of the horn on the roof frame can be effected by lateral edges of the ends of the roof.

In general, a method of attaching a flag according to the invention to a vehicle body may conventionally comprise a step of fixing the flag on the flag frame, followed by a step of securing the flag frame to the body vehicle, the latter can be implemented by conventional sheet metal assembly processes of the field of the invention, in particular by welding.

This aspect is advantageous because it allows to keep a common flagbox, in order to achieve either a pavilion composite material or a conventional metal pavilion. The method may comprise a prior step of securing reinforcing means on the roof. In other aspects, a method of assembling a composite material roof of the invention on a vehicle body may advantageously comprise the following steps: a) securing a roof frame to the body of a vehicle, b) securing reinforcement means to said roof frame, c) attaching the composite roof to the roof frame of a vehicle. A roof frame can therefore first be secured to the body of a vehicle. Reinforcing means may be provided, for example a central roof cross member, which may advantageously be of plant material. The flag composite material can then be fixed by securing means, such by gluing, to the flag frame.

A step of securing, for example screwing, reinforcement means with the vehicle body can be provided, which results in a better anchoring. This screwing step can preferably be performed on the edge ends of the vehicle body.

The invention also relates to a motor vehicle comprising a roof made of a composite material according to the invention. The invention is now described in more detail with the non-limiting figures in which: - Figure 1 shows (A) a schematic perspective view of a vehicle roof and (B) a roof frame intended to receive the flag (A), according to an exemplary embodiment; FIG. 2 represents (A) an example of a reinforcement means of a vehicle roof and (B) a roof frame, on which is fixed a reinforcing means, positioned in this roof frame, according to an embodiment; FIG. 3 represents a sectional view of an example of a reinforcement means attached to the vehicle roof, according to one embodiment: FIG. 4 represents an example of a sectional view of the positioning of a roof, FIG. according to the invention, on a roof frame, (A) a roof front section, (B) a roof rear section and (C) a roof side section, according to an exemplary embodiment. According to the embodiment of FIG. 1 (A), the roof of a vehicle 1 is made of a composite material made from a superposition of two transparent thermoplastic polymer PMMA layers and a bamboo sheet 2 in the form of a plurality of laminated strips. glued (not visible in Figure 1), which sheet 2 is perforated, that is to say that it occupies only the edge ends of the flag 3. A strip of bamboo sheet 2 divides the flag 1 into two surface areas 4.

The surface areas 4 consist of the only PMMA polymer material which is transparent. Flag 1 is manufactured according to the encapsulation method described above. Figure 1 (B) shows a conventional metal horn frame 10 shaped to receive the horn 1 of Figure 1 (A). FIG. 2 (A) shows a reinforcement means 20, here a U-shaped central crosspiece, comprising edge ends 21 intended to cooperate with an inner surface of the roof 1, the crossbar 20 being fastened to the sheet strip of bamboo 2 by bonding the ends 21, the dimensions of the cross 20 and the strip 2 being identical. These divide the frame 10, fixed to the roof 1 by the edge ends 3, in two surface areas 4 (Figure 2 (B)). The cross 20 is here bamboo. The edge ends 21 define orifices 22 adapted to receive screws (not shown) for maintaining the cross member 20 on the body.

Figure 3 shows a sectional view of a reinforcing means, here a cross member 20, the outer surface is directed towards the direction of the passenger compartment of the vehicle. The crossbar 20 is here in the form of a double slot whose edge ends 21 are fixed by a polyurethane glue 6 on the internal surface of the roof 1, on the second layer of PMMA polymer 5bis, the roof 1 being made of material composite comprising a bamboo sheet 2 interposed between a first layer of PMMA polymer 5 and the second layer 5a.

The cross member 20 is in turn covered with the composite material (a bamboo sheet 2 interposed between the two layers of PMMA polymer 5, 5a). Staples 7 hold the composite material on the surface of the crosspiece 20.

Figure 4 (A) is a sectional view of a front section of positioning a flag 1 of composite material (a bamboo sheet 2 interposed between the two layers of PMMA polymer 5, 5a) on a roof frame 10 by the edge 8 of the horn on complementary surfaces 9 provided on the frame 10. Polyurethane glue 30 is placed between said surfaces 8, 9. A polymer gasket 40 is placed between said surfaces 8, 9. 4 (B) is a rear sectional view of positioning a flag 1 of composite material (a bamboo sheet 2 interposed between the two layers of PMMA polymer 5, 5a) on a roof frame 10 by the lateral ends the edge of the horn on complementary surfaces 9 provided on the frame 10. Polyurethane glue 30 is placed between said surfaces 8, 9. Figure 4 (C) shows a sectional view of a lateral positioning section. of a pavilion 1 composite material (a bamboo sheet 2 interposed between the two layers of polymer PMMA 5, 5a) on a roof frame 10 by the edge ends 8 of the roof on complementary surfaces 9 provided on the frame 10. Glue 30 is provided in the empty space between the pavilion and the frame surfaces. A polymer gasket 40 is placed between said surfaces 8, 9.25

Claims (11)

REVENDICATIONS1. Pavilion of a motor vehicle (1) made of composite material comprising a sheet of plant material (2) interposed between at least two layers of polymeric material (5, 5a), said composite material ensuring optimum rigidity and robustness of said flag, said plant material being selected from the group consisting of bamboo, beech, chestnut, ash, birch, oak, alder, eucalyptus, Scots pine, fir, spruce, Douglas fir, larch , Red Ceddar wood, Ipe, iroko, bankirai, teak, mahogany and their mixture. 2. Pavilion according to claim 1, wherein the sheet (2) of plant material has a thickness of between 0.5 mm and 3 mm, the at least two layers (5, 5a) having respective thicknesses the same or different, of which the values are between 1.4 and 2 mm. 3. Pavilion according to claim 2, wherein when the plant material is bamboo, the thickness of the sheet (2) is between 0.5 and 1.2 mm, 4. Pavilion according to one of claims 1 to 3, which is entirely made of composite material (2, 5, 5a). 5. Pavilion according to one of claims 1 to 3, which is made of composite material comprising areas devoid of leaves (2) of plant material. 6. Pavilion according to one of claims 1 to 5, further comprising one or more means (s) reinforcement (20) of predetermined shape, fixed (s) on the inner surface of the flag (1), on a frame of flag (10) and / or on a vehicle body. 7. Pavilion according to claim 6, wherein the reinforcing means (20) are of plant material. 30 8. Pavilion according to claim 6, wherein the reinforcing means (20) are made of a metallic material, whose outer surface, directed towards the interior of the passenger compartment, is covered with said composite material (2, 5, 5a) . 9. A method of manufacturing a motor vehicle roof (1) composite material (2, 5, 5a), as defined in any one of claims 1 to 8, comprising the following steps: 1) place a sheet (2) of plant material on a first layer of thermoplastic polymer material (5) and making, on a plurality of edge ends (3) of said sheet (2), a frame comprising a film of a compound capable of being demolded, 2) spreading on the plurality of edge ends (3) of the sheet (2) a room temperature polymerizable adhesive solution comprising a polymerization catalyst for obtaining a film of solid adhesive; 3) after completion of the polymerization reaction of step 2), covering the surface of the sheet (2) with said polymerizable adhesive liquid solution, and 4) before completion of the polymerization reaction of the step 3), fixing on the surface of the sheet (2) covered with said adhesive liquid solution, a second layer (5a) of thermoplastic polymer material, for obtaining the flag (1) of a motor vehicle of composite material (2, 5, 5bis). 10. A method of assembling a flag composite material (2, 5, 5a), as defined according to one of claims 1 to 8 or as obtained according to the implementation of the method of claim 9, on a vehicle body, comprising the following steps: a) securing a roof frame to the body of a vehicle, b) securing reinforcement means to said roof frame, c) attaching the composite roof to the frame flag of a vehicle. 11. Motor vehicle comprising a horn (1) of a composite material (2, 5, 5 bis), as defined according to one of claims 1 to 8 or as obtained according to the implementation of the method of claim 10.