EP0581635B1 - Process for preparing an article of composite material with a non-organic matrix - Google Patents

Description

The invention relates to a manufacturing process. of a piece of composite material, from wicks formed from filaments of an organic material such as carbon or ceramic, and inorganic material such as a metal or a metal alloy, with a view to make a part of composite material with a non-matrix organic.

To make parts from composite material non-organic matrix, we usually have spread wicks, wound on spools with separators dividers. These spread wicks are formed parallel filaments of organic material such as carbon or ceramic, coated with a material not organic intended to form the matrix of the composite material. This non-organic material consists either of a metal, either by a metal alloy.

The substantially parallel filaments which form the spread wick give it a discontinuous nature which makes it particularly difficult its grip and, consequently, its implementation during of the production of a composite material part. In particular, it is difficult, if not impossible, to cut and drape spread carbon wicks and metallic.

By the way, assuming that cutting and the draping of the spread wicks can be carried out, the thickness reduction that accompanies the thermomechanical cycle final to obtain the material part composite from the stack of spread wicks inevitably leads, in the case of non-planar parts, at the breaking of part of the filaments. Therefore, the composite part obtained is damaged and does not does not meet the required quality requirements.

We know from document FR-A-2 437 296 a process for manufacturing a matrix composite material metallic, in which we wind, helically on a mandrel, a strand of filaments, not spread out, then immerses the mandrel in a suspension of metallic powder in a pure solvent. After drying at temperature ambient, the mandrel is immersed in a metallic powder dispersed in a polymer-solvent solution. Air drying provides a sheet-shaped precomposite, which is cut and that we stack. The stack is then cold rolled to form a puff pastry. This laminate is placed in the mold of a press where it is heated under vacuum, so as to remove the solvent and decompose the polymer. The application of a thermomechanical cycle makes it possible to obtain the desired part.

In this known process, the polymer constitutes a temporary binder which makes it possible to obtain a precomposite leaf-shaped with handling and cutting are facilitated. However, the use of such a binder temporary to form an extremely thin film from a wick of filaments, spread out, is not envisaged.

In document FR-A-2 437 296, the laminated is obtained by cold rolling the stack of leaves. The temporary binder remains rigid during of this cold rolling operation. Therefore, filaments may break if the workpiece has a complex shape (half-shell, cap, etc.).

In the particular case of a tubular part, document FR-A-2 366 904 proposes to place in a mold heated a stack of sheets formed of fibers refractories embedded in a metallic matrix. The mold includes an expandable internal bladder and a non-deformable female imprint, allowing to apply a thermomechanical cycle determined on the stack. The filaments of each of the sheets in the stack can be bonded together by a polymerized glue. Prior to the application of the thermomechanical cycle, the glue is pyrolyzed by a first heating of the mold.

The main object of the invention is a process for manufacturing parts from material non-organic matrix composite of any shape, possibly complex, preserving continuity filaments and, therefore, the characteristics mechanical parts.

• formation d'une nappe à partir de mèches de filaments et d'un matériau apte à former ladite matrice ;
• imprégnation des mèches de la nappe par un liant provisoire, dissous dans un solvant ;
• évaporation du solvant par chauffage, de façon à conditionner la nappe sous la forme d'une feuille souple ;
• découpage de morceaux dans la feuille souple ;
• drapage de ces morceaux, de façon à former au moins un empilement ;
• réalisation d'une préforme d'épaisseur et de forme intermédiaires entre l'épaisseur et la forme de l'empilement et l'épaisseur et la forme de la pièce à fabriquer ;
• application d'un cycle thermomécanique sur la préforme, de façon à donner à cette dernière l'épaisseur et la forme de la pièce à fabriquer, et à dégrader le liant provisoire ;

caractérisé par le fait qu'on réalise la préforme en chauffant l'empilement jusqu'à une température de collage du liant provisoire, en exerçant une action mécanique sur l'empilement, puis en refroidissant ce dernier jusqu'à une température de durcissement du liant provisoire.In accordance with the invention, this result is obtained by means of a process for manufacturing a part made of a composite material with a non-organic matrix, comprising the following steps:

• forming a sheet from strands of filaments and a material capable of forming said matrix;
• impregnation of the strands of the sheet with a temporary binder, dissolved in a solvent;
• evaporation of the solvent by heating, so as to condition the sheet in the form of a flexible sheet;
• cutting pieces in the flexible sheet;
• draping of these pieces, so as to form at least one stack;
• production of a preform of thickness and intermediate shape between the thickness and the shape of the stack and the thickness and the shape of the part to be manufactured;
• application of a thermomechanical cycle on the preform, so as to give the latter the thickness and the shape of the part to be manufactured, and to degrade the temporary binder;

characterized by the fact that the preform is produced by heating the stack to a bonding temperature of the temporary binder, by exerting a mechanical action on the stack, then by cooling the latter to a curing temperature of the binder provisional.

When the draping has been carried out, the binder temporary, heated to a suitable temperature when thermal cycle, behaves like an adhesive which allows to make a preform, in one or more steps, before bringing the part to its final form when due final thermomechanical cycle. The passage of the room through one or more intermediate forms before its implementation final shape allows the filaments to take their place gradually, which allows the production of parts of complex shapes, without breaking of filaments and allows the use of less expensive tools to apply the final thermomechanical cycle.

Furthermore, the impregnation of the locks by a temporary binder, allows to condition these wicks under the shape of a flexible sheet formed of several wicks juxtaposed, which makes cutting and draping extremely easy. To allow the production of a film flexible, very wide, the impregnation step is advantageously preceded by a winding step of wicks spread on a mandrel, to form a layer of parallel filaments juxtaposed.

We also observe that the thermomechanical cycle which allows to get the final piece also has has the effect of degrading the temporary binder, i.e. to break it down in order to facilitate its suction out of the part by a gas sweep or by vacuum. In in some cases, the degraded temporary binder may also stay trapped in the room. However, he does not play then no role.

In a preferred embodiment of the invention, the temporary binder is a thermoplastic binder such as polystyrene.

Heating of the stack is then carried out at a bonding temperature between approximately 160 ° and around 280 ° C.

Depending on the shape and thickness of the piece that one wishes to achieve, the mechanical action exerted on the stack in order to achieve the preform can be different natures. So it can be one or several compacting actions, whether or not followed by one or more several shaping actions.

In the particular case where the part to be produced is tubular in shape, you can either make a stack single tubular, i.e. at least two stacking separate tubulars. In the latter case, the preform by exerting a mechanical compaction action on a first tubular stack, at the temperature of bonding of the temporary binder, cooling the first tubular stack thus compacted, having coaxially this first compacted tubular stack and a second tubular stack, exercising a new mechanical action of compaction at the temperature of the bonding of the temporary binder, cooling the first and the second tubular stacks thus compacted, and repeating these operations until all tubular stacks made previously to be compacted.

Still in the case of a tubular part, we drapes over an expandable bladder forming the inner element of a compaction mold, and exerts a mechanical compaction action on the stack by inflating said bladder. In addition, we apply mechanical compacting action on the preform by placing the latter on an expandable bladder forming the inner element of a consolidation mold, and inflating said bladder. The expandable bladder of the consolidation mold is advantageously made in stainless steel, in order to be able to withstand strong pressures implemented without risk of bursting.

When the material intended to form the matrix of the play justifies it, in particular because of its oxidisable nature, it is integrated into the stack at minus a surface protection sheet, when draping.

Preferably, it is impregnated with the provisional binder strands spread with parallel filaments, such that the evaporation of the solvent conditions these wicks spread in the form of a flexible film in which the parallel filaments are connected by the binder provisional stiffened.

Advantageously, the impregnation step is preceded by a winding step of the strands spread over a mandrel, to form a layer of parallel filaments juxtaposed.

In a preferred embodiment of the invention, the thermomechanical cycle comprises a first phase of degradation of the temporary binder, at during which the temperature is brought and maintained at a first bearing, without mechanical action on the preform, and a second consolidation phase, during from which the temperature is brought to and maintained at a second level, higher than the first, and an action mechanical compression is applied to the preform.

When it has been degraded, the temporary binder is advantageously evacuated from the room either by a gas sweep, either by vacuum.

• la figure 1 illustre schématiquement les étapes successives du procédé selon l'invention, dans le cas où la pièce à fabriquer est une demi-coquille présentant une section en forme d'Ω ;
• la figure 2 illustre schématiquement la phase de compactage du procédé selon l'invention, dans le cas où la pièce à fabriquer est de forme tubulaire ; et
• la figure 3 est une vue en coupe longitudinale représentant un moule utilisable lors du cycle thermomécanique final qui suit la phase de compactage illustrée sur la figure 2.

We will now describe, without limitation, two examples of implementation of the manufacturing method according to the invention, with reference to the accompanying drawings, in which:

• Figure 1 schematically illustrates the successive steps of the method according to the invention, in the case where the part to be manufactured is a half-shell having a section in the form of Ω;
• FIG. 2 schematically illustrates the compacting phase of the method according to the invention, in the case where the part to be manufactured is of tubular shape; and
• FIG. 3 is a view in longitudinal section showing a mold usable during the final thermomechanical cycle which follows the compaction phase illustrated in FIG. 2.

As previously indicated, the process of manufacture according to the invention applies to the manufacture of parts from matrix composite material inorganic, from wicks spread with filaments organic such as carbon or ceramic filaments, coated with inorganic material such as metal or a metal alloy intended to form the matrix composite material.

The first phase of this manufacturing process allows to condition the spread wicks, in the form a flexible film, in order to facilitate cutting and subsequent draping of these locks.

To carry out this pre-conditioning, we has spread wicks 10, formed for example of carbon filaments 11 substantially parallel between them and metallized. These spread wicks are wound on storage coils, along with a separator interlayer which prevents the filaments of successive layers to get tangled. For example, the width of the spread wick can be about 40 mm.

As shown schematically in Figure 1, a first step consists in coating a mandrel 12 an interface plate 13.

During a second stage aimed at obtaining a very wide tablecloth, the spread wick 10 is wound edge to edge or overlapped on the mandrel 12, coated with interface plate 13, as illustrated schematically Figure 1. This gives a sheet of parallel filaments 11 juxtaposed, forming a layer single filaments on the mandrel 12.

During a third stage of the first phase of the manufacturing process according to the invention, the interface sheet 13 carrying the layer of filaments 11 is deployed and flattened. To allow this operation, the sheet and filaments are cut according to a generator of the mandrel.

As illustrated schematically on the Figure 1, the sheet of filaments 11 resting on the sheet interface 13 is then impregnated with a temporary binder, dissolved in a solvent. We can use this effect a nozzle 14. In the embodiment considered, the temporary binder is a thermoplastic type binder such as polystyrene, which has the advantages to use a solvent (toluene) of reduced toxicity, allow the viscosity of the solution to be controlled obtained, to be able to be used at low temperature and be sufficiently rigid at room temperature. For example, approximately 100 g of polystyrene can be dissolved in one liter of toluene.

When the impregnation of the layer of filaments 11 resting on the interface sheet 13 is finished, the impregnated sheet is subjected to a thermal cycle as illustrated by the arrow 16 in FIG. 1. This thermal cycle, carried out at atmospheric pressure, has to evaporate the solvent, i.e. toluene in the example considered. It consists of heating the layer of filaments 11 impregnated with the polystyrene solution at a temperature of about 120 ° C.

The evaporation of toluene results in restore the polystyrene its rigidity when descending at room temperature. The polystyrene then ensures cohesion between the filaments 11 of the sheet resting on the interface plate 13. Consequently, when the thermal cycle is complete, the layer of filaments 11 separated from the interface plate 13 behaves like a flexible film 18, of very small thickness, formed of filaments juxtaposed parallels 11, interconnected by the polystyrene. This conditioning of the filaments under the shape of a flexible film makes it possible to cut them and to easy to handle during subsequent processing of the process, which was practically not possible before.

The second phase of the manufacturing process according to the invention consists in making a preform at using the flexible film obtained previously. Obtaining of this preform is permitted for shaped parts any, possibly complex, by the presence temporary binder such as polystyrene which is associated to the filaments 11 in the flexible film 18. Indeed, when the polystyrene is heated to a temperature between about 160 ° C and about 280 ° C, it behaves like a glue that keeps the relative to each other the different layers cut from the flexible film and give to the stack thus formed the desired thickness and shape. We understand that the realization of a preform thickness and shape intermediate between the thickness and the shape of the initial stack and the thickness and the shape of the workpiece facilitates shaping filaments and therefore very significantly limits the risks breakage of these filaments during manufacture of the part, even when the latter is shaped complex (half-shell, cap, etc.).

This phase of manufacturing a preform begins with film cutting and draping steps 18, to form a stack 20 of superimposed layers. More precisely, each of the layers of the stack is cut from the flexible film 18 and the filaments it contains are oriented in a specific direction, which takes into account the mechanical characteristics of the piece you want to make. In a layout conventional, the filaments of the adjacent layers can especially be oriented at angles which differ by about 45 ° from one layer to another.

Depending on the shape of the room you want achieve, the stack 20 can be achieved either by draping on a flat surface as illustrated schematically Figure 1, either by draping over a surface of different shape, such as a cylindrical mandrel when you want to make a tubular part, as we will see later.

When this draping operation is finished, we proceed to the realization of a preform by submitting stacking 20 to an accompanied thermal cycle a mechanical action of compacting and / or placing form.

When the preform to be produced differs from the stack 20 both by its thickness and by its shape, as in the example of embodiment illustrated in Figure 1, the realization of the preform advantageously takes place in two successive stages.

The first of these steps consists of a compacting operation to transform the stack 20 into a blank 22 which has the same shape as stack 20 (i.e. a planar shape in the example shown) but whose thickness is equal to that of the preform that we want to achieve. In others terms, this compacting operation involves reduce the thickness of the stack 20 in order to give the blank 22 a thickness intermediate between that of the stack 20 and that of the part to be produced.

The creation of the blank 22 from stacking 20 is carried out by subjecting the latter to a thermal cycle at a temperature sufficient to give with the provisional binder the characteristics of an adhesive. In the example described where the temporary binder is constituted by polystyrene, this temperature is at least equal to 160 ° C and must be kept at this level for a duration of at least 15 min. The temperature should however stay below about 280 ° C, to avoid any degradation or decomposition of the polystyrene at this manufacturing stage. Concretely, a heating of stacking 20 at about 180 ° C for about 30 min. ensures the bonding of the layers constituting the stack.

In order to reduce the thickness of the stack 20 to obtain the blank 22, this thermal cycle is accompanied a mechanical compaction action, obtained in subjecting the stack to a pressure greater than 1 bar (for example, about 20 bars) when stacking is at 180 ° C, then during cooling up to a temperature close to 70 ° C. The hardening polystyrene then allows the stack not to resume its initial thickness.

This compacting operation can be performed placing stack 20 in a press heated or in an autoclave.

In the embodiment illustrated on the FIG. 1, the preform 24 is then produced during of a second shaping operation. During this operation, the thickness of the blank 22 is practically not modified, but we give it a shape comparable to that of the part to be produced but whose contours are less accentuated, so that this shape is substantially intermediate between that of the blank 22 and that of the final part.

To perform this setting operation form of the blank 22, it is subjected to a thermal cycle comparable to that which was applied on the stack during the compacting operation. This here again, the thermal cycle gives the binder the characteristics of an adhesive when the shaping is performed. So we heat the blank 22 in an oven up to a temperature of about 180 ° C, then maintain the temperature at this level for about 30 min.

The mechanical action of shaping the blank 22 is exercised by placing the latter between a punch whose active part is preferably relatively flexible and a rigid matrix. To ensure shaping, a pressure of at least about 20 bars is applied between the punch and the die when the temperature reaches about 180 ° C and this pressure is held until the temperature has dropped up to a value close to 70 ° C. The provisional binder is then stiffened and maintains the preform in the final form obtained.

When the preform 24 has been obtained, the manufacturing of the composite material part is finished by implementing a final thermomechanical cycle to obtain the final part illustrated in 26 on the face. This final thermomechanical cycle is sometimes called "consolidation".

As shown schematically in Figure 1, in order to produce the part 26, the preform 24 is placed between a punch 28a and a die 28b whose surfaces are complementary to the opposite faces of the part 26 to achieve. The punch 28a as the die 28b have shapes different from those of the punch and the matrix used previously, during the second shaping operation, to make the preform 24. Indeed, we have seen previously that the shape of the final part 26 is different from that of the preform 24. In addition, the material which constitutes the punch 28a is different from that which constitutes the punch used during this second setting operation form.

After the preform 24 has been placed between the punch 28a and the die 28b, the thermomechanical cycle final is applied up to a temperature allowing welding-diffusion of non-organic material which coating the filaments contained in the preform, so that this material fills most of the inter-filament spaces and forms the matrix of the composite material. It is important to observe that this temperature is always higher than the degradation temperature or decomposition of the provisional binder, i.e. about 400 ° C in the case of polystyrene. As non-limiting example, when the composite material is made of carbon filaments embedded in a matrix aluminum, the final thermomechanical cycle corresponds to heating of the preform 24 to a temperature about 600 ° C for about 1 hour, a pressure relatively large, for example between about 100 bars and about 250 bars, being applied between the punch 28a and the die 28b.

When this final step is completed, we obtains a part 26 whose thickness is substantially reduced compared to that of the preform 24, itself lower than that of the initial stack 20. The passage by the preform 24, however, improves the conditions for forming the filaments inside of the part during its manufacture, so that the risks of rupture of these filaments are practically removed and the part obtained meets the requirements quality.

Depending on the case, the decomposed polystyrene residues during the final thermomechanical cycle can remain trapped in the composite material or at otherwise be flushed out of this material during the cycle thermomechanical. In the latter case, evacuation is obtained by vacuuming residues, either by performing a gas sweep, either by vacuum.

We will now describe, with reference to the figures 2 and 3, the manufacture of a tubular part by the method according to the invention.

The first phase of the process, leading to obtaining a flexible film 18 formed from organic filaments 11 juxtaposed parallels, coated with a material inorganic and linked together by a binder stiffened temporary such as polystyrene, is identical to that previously described with reference to in Figure 1.

The second phase of the process, illustrated on the Figure 2, consists in this case of making a preform tubular whose thickness is greater than that of the part to be produced.

More precisely, the thickness of the preform obtained at the end of this second phase is intermediate between that of a stack or a winding initial of pieces cut from the flexible film 18 and draped over a mandrel, and the thickness of the workpiece to achieve. Furthermore, the outside diameter of the preform is substantially equal to or barely less than that of the part to be produced, while its diameter interior is less than that of this room.

The second phase of the process begins with a step of cutting pieces of appropriate sizes in the flexible film 18.

This cutting step is followed by a step layup, performed in this case on a cylindrical mandrel.

Depending on the thickness of the piece you want obtain, a single draping operation followed by a single compaction step, or several operations of layup each followed by a compaction step can be performed, as shown schematically in figure 2.

When the thickness of the part is sufficient weak so that the preform can be obtained by a single compaction step, the pieces of the film flexible 18 previously cut are draped in a single operation on an expandable cylindrical mandrel consisting of an inflatable elastomeric bladder. This bladder forms the internal element of a compaction mold, comparable in structure to the consolidation mold used during the final thermomechanical cycle, which will be described thereafter with reference to FIG. 3.

The outside diameter of the inflatable bladder is significantly smaller than the inside diameter of the preform that we want to obtain, while the diameter outside of the stack or winding formed on the bladder is practically equal or very slightly lower the outside diameter of this preform.

The inflatable bladder carrying the stack or the winding is then placed in a rigid tube constituting the external element of the compaction mold. The compaction mold is then introduced into a oven or in an autoclave for applying a thermal cycle during compaction.

At first, the temperature is raised to a value sufficient to give the provisional binder of the characteristics of an adhesive, without cause its degradation or decomposition. In the case of polystyrene, we have already seen that heating at around 180 ° C, or more, for about 30 min ensures the bonding of the layers of the stack.

When the bonding temperature (e.g. 180 ° C) is reached, a compaction pressure is applied to the stack, by inflating the bladder inflatable. This compaction pressure is at least equal to approximately 20 bars. It is maintained during the preform cooling to a temperature of which the temporary binder is hardened. In the case of polystyrene, compaction pressure is maintained until the temperature has dropped to approximately 70 ° C.

Depressurization of the elastomeric bladder causes its removal and promotes the release of the preform thus obtained.

When the thickness of the part to be produced is too large, the preform is produced in several steps. Figure 2 illustrates the case where two cycles of successive compaction are applied in order to obtain the preform.

In this case, a stack is produced on the one hand external 20a on a first elastomeric bladder inflatable and, on the other hand, an internal stack 20b on a second inflatable elastomeric bladder. As when only one compaction cycle is applied, the inflatable metal bladders form the elements internal of two compaction molds similar to the mold of consolidation of figure 3.

The outer diameter of the outer stack 20a is practically equal or very slightly lower to the external diameter of the preform to be obtained. By elsewhere, the outside diameter of the internal stack 20b is practically equal or very slightly lower the inside diameter of the external stack 20a, when the latter has been compacted.

First of all, the compacting of the stack is carried out. external 20a according to a compaction process analogous to that previously described in the case where only one compaction step is necessary. For this, we place the first bladder carrying the stack external 20a in a rigid tube and the mold thus formed in an oven or in an autoclave. When the bonding temperature of the temporary binder is reached, a compaction pressure is applied to stacking, by means of the first bladder. This pressure is maintained after sufficient cooling so that the temporary binder is hardened. Stacking compacted external 22a is then removed from the mold.

Before proceeding to the second compaction cycle, placing the compacted external stack 22a around of the internal stack 20b, not yet compacted, formed on the second bladder. The assembly is then introduced in a rigid tube, and the mold thus formed is placed in a mold or in an autoclave.

As in the first compaction cycle, the temporary binder is first brought to its temperature of collage. When this temperature is reached, a compaction pressure is applied to the assembly formed by the non-compacted internal stack 20b and by the compacted external stack 22a, by means of the second bladder. This pressure is maintained until that the assembly is sufficiently cooled to ensure hardening of the temporary binder. When cooling is finished, we get a tubular preform 24 whose outside diameter is close to that of the part to be produced, but whose thickness is greater.

In accordance with the invention, the production phase tubular preform 24, including one or more several compaction operations, is followed by a thermomechanical consolidation cycle allowing give the room its final dimensions. During of this consolidation cycle, the inorganic material which coats the filaments is brought to its temperature of welding-diffusion, allowing it to fill spaces inter-filaments and form the matrix of the material composite.

This consolidation cycle is obtained by placing the tubular preform 24 in a consolidation mold 30 illustrated diagrammatically in FIG. 3. As already mentioned, the compaction mold (s) used during necessary compaction operations to the manufacturing of the preform do differ from this mold 30 only by their dimensions.

The consolidation mold 30 has a inflatable metal bladder 32, tubular in shape and uniform circular section, on which the tubular preform 24. This bladder is made in a metal or a sufficiently resistant metal alloy so that it can withstand the compaction pressure applied during consolidation, which can reach 100 to 250 bars. Under these conditions, the use of a bladder 32 made of thin stainless steel, is recommended, in particular by the fact that this material is inert from a physico-chemical point of view, for materials constituting the composite material part to to manufacture. The bladder 32 has a closed end and an open end, provided with a flange 32a.

The external element of the mold 30 is constituted by a rigid tube 34, for example of steel. This tube is made in two parts whose joint plane passes through its longitudinal axis, so as to allow demolding when the consolidation is complete.

The rigid tube 34 is itself placed in a non-deformable external security enclosure 36, tubular shape and very thick. This enclosure, made for example of refractory steel, takes up the forces applied to the tube 34 during inflation of the bladder 32. It has a frustoconical inner surface, complementary to a frustoconical exterior surface of tube 34. This characteristic makes it possible to extract the tube 34 containing the part and the bladder 32, when consolidation is complete.

The flange 32a is sealed between the corresponding ends of the rigid tube 34 and security enclosure 36 on the one hand and the cap 38 screwed onto the safety enclosure 36, on the other go. This plug 38 is crossed axially by a conduit 40 connected to a pressure source and opening inside the bladder 32. The other plug 38 is crossed by a conduit 42 adapted to be connected by a valve V1 either to a vacuum source 44 of a gas conditioning, i.e. to a sewer 46. A inside the mold 30, the duct 42 opens into the annular space 48 formed between the bladder 32 and the rigid tube 34. Another conduit 50 passes radially the security enclosure and communicates with space 48 by a passage 52 formed in the rigid tube 34. A outside the mold 30, the conduit 50 communicates with a source of neutral gas 54 from the gas conditioning, through a valve V2.

The mold 30 is itself placed in an oven tubular (not shown) for applying to the tubular preform 24 a determined temperature cycle. When the welding-diffusion temperature of the material non-organic intended to form the matrix is reached, the pressure necessary for consolidation is applied on the preform 24, by means of the bladder 32.

More precisely, before any application pressure on the tubular preform 24, the interior of the mold 30 is subjected to a sweeping of a neutral gas such as argon, via lines 42 and 56, valve V2 being open and the valve V1 open on the sewer 46. The temperature is then gradually raised to a first level, ensuring degradation or decomposition of the temporary binder. It is gradually removed from the preform by scanning gaseous.

When all the temporary binder has been removed, the mold is evacuated through line 42 (valve V2 closed and valve V1 open on the vacuum source 44) and the temperature is gradually raised again up to a second level, corresponding to the welding-diffusion temperature of the material intended for form the matrix. The bladder is then put under pressure to reduce the porosity of the room to a minimum value. The dimensions of the room then correspond to the desired value.

After cooling, the mold is removed of the room. For this, we extract the tube 34, containing the part and the bladder 32, of the enclosure 36, which is facilitated by the taper of the surfaces in contact with the tube 34 and enclosure 36. The tube 34 is then dismantled two parts. The extraction of bladder 32 is finally performed either by electrochemical machining or by chemical machining, either by machining one or several grooves along the entire length of the bladder, then "peeling" of the latter by thermomechanical traction.

It should be noted that the preform 24 can be coated with a protective metal sheet on its interior and exterior surfaces, when the material intended to form the matrix requires it, for example in because of its oxidizable nature. So if this material is magnesium, preform 24 is coated with sheets titanium.

In the case of a tubular preform, the protective sheets are put in place when or drapes, on the surfaces intended to form the interior and exterior surfaces of the preform. When an external stack 20a and an external stack 20b are produced separately, a protective sheet is placed around the external stack 20a and another protective sheet is placed inside of the internal stack 20b.

The two examples of implementation which come to be described with reference to Figure 1, then Figures 2 and 3 highlight the advantages which arise from the use of the manufacturing process according to the invention.

The main benefit stems from manufacturing an intermediate preform, thanks to the application mechanical action on the stack, after it has been heated to a temperature such that the temporary binder behaves like an adhesive which ensures the connection between the filaments of the different layers, while allowing their relative displacement. Because the mechanical action is maintained during cooling, until the temporary binder hardens, this then ensures cohesion and maintenance in the state of the preform thus produced. The use of this technique makes it possible to obtain shaped parts complex with practically no filament breakage, which was not possible with prior techniques.

As already mentioned, the preform which is performed before applying the thermomechanical cycle final can be obtained either directly, in one single operation, from the stack of layers, either in two or more operations, depending on the complexity of the shape of the part to be obtained and according to the reduction thickness that must be performed. In all cases, the quality of the part obtained is very appreciably improved compared to current techniques, without that it is necessary to use tools complex and expensive.

In the particular case of tubular parts, passing through an intermediate preform according to the technique described above makes it possible to manufacture such parts from spread wicks with filaments are prepreg of inorganic material, which was not possible with existing techniques. In indeed, the very high porosity of the stack requires very significantly reduce the thickness of the latter to get the desired tubular piece, and apply very high pressures. This inevitably results bursting of the expanding mold bladder, whatever either the material constituting this bladder, if the techniques are used.

Another benefit is provided by packaging wicks spread in the form of a film flexible 18, very thin, which can be easily cut, manipulated and implemented to achieve then without particular difficulty of the shaped parts any.

Claims (17)

1. Process for manufacturing a component (26) made of a composite having a non-organic matrix, comprising the following steps:

   formation of a web from rovings (10) of filaments (11) and of a material capable of forming the said matrix;

   impregnation of the rovings (10) of the web by a temporary binder dissolved in a solvent;

   evaporation of the solvent by heating, so as to package the web in the form of a flexible sheet (18);

   cutting of pieces from the flexible sheet;

   laying-up of these pieces, so as to form at least one stack (20);

   production of a preform (24) having a thickness and a shape which are intermediate between the thickness and the shape of the stack (20) and the thickness and the shape of the component (26) to be manufactured;

   application of a thermomechanical cycle to the preform (24), so as to give the latter the thickness and the shape of the component (26) to be manufactured, and to degrade the temporary binder;

   characterized in that the preform is produced by heating the stack (20) up to a bonding temperature of the temporary binder, by exerting a mechanical action on the stack (20) and then by cooling the latter down to a temperature for hardening the temporary binder.
2. Process according to Claim 1, characterized in that the temporary binder is of the thermoplastic type.
3. Process according to Claim 2, characterized in that the thermoplastic binder is polystyrene.
4. Process according to Claim 3, characterized in that the heating of the stack (20) is carried out at a bonding temperature of the polystyrene at least equal to approximately 160°C and at most equal to approximately 280°C.
5. Process according to any one of the preceding claims, characterized in that at least one mechanical compacting action is exerted on the stack (20).
6. Process according to any one of Claims 1 to 4, characterized in that at least one mechanical compacting action and at least one mechanical shaping action are exerted on the stack (20).
7. Process according to any one of Claims 1 to 4, applied to the manufacture of a tubular component, characterized in that at least two separate tubular stacks (20a, 20b) are produced and in that the preform is produced by exerting a mechanical compacting action on a first tubular stack (20a), at the bonding temperature of the temporary binder, by cooling the first tubular stack (20a) thus compacted, by placing this first compacted tubular stack (20a) coaxially with a second tubular stack (20b), by exerting a new mechanical compacting action at the bonding temperature of the temporary binder, by cooling the first and second tubular stacks (20a, 20b) thus compacted and by repeating these operations until all the tubular stacks produced previously are compacted.
8. Process according to any one of Claims 1 to 4 and 7, applied to the manufacture of a tubular component, characterized in that the laying-up is done over an expandable bladder forming the internal element of a compacting mould and in that a mechanical compacting action is exerted on the stack (20a, 20b) by inflating the said bladder.
9. Process according to Claim 8, characterized in that, during the thermomechanical cycle, a mechanical compacting action is applied to the preform (24) by placing the latter over an expandable bladder (32) forming the internal element of a consolidation mould (30) and by inflating the said bladder.
10. Process according to Claims 8 and 9 together, characterized in that the expandable bladder (32) of the consolidation mould (30) is made of stainless steel.
11. Process according to any one of the preceding claims, characterized in that at least one superficial protective sheet is integrated into the stack during the laying-up.
12. Process according to any one of the preceding claims, characterized in that spread-out rovings (10) of parallel filaments (11) are impregnated by the temporary binder in such a way that the evaporation of the solvent packages these spread-out rovings in the form of a flexible film (18) in which the parallel filaments are connected by the rigidified temporary binder.
13. Process according to Claim 12, characterized in that the impregnation step is preceded by a step in which the spread-out rovings (10) are wound over a mandrel (12) in order to form a layer of juxtaposed parallel filaments (11).
14. Process according to any one of the preceding claims, characterized in that the thermomechanical cycle comprises a first phase of degradation of the temporary binder, during which the temperature is brought to and held at a first level, without any mechanical action on the preform (24), and a second phase of consolidation, during which the temperature is brought to and held at a second level, greater than the first, and a mechanical compression action is applied to the preform (24).
15. Process according to Claim 14, characterized in that the degraded temporary binder is removed from the preform (24).
16. Process according to Claim 15, characterized in that the degraded temporary binder is removed by a gas purge.
17. Process according to Claim 15, characterized in that the degraded temporary binder is removed by vacuum.

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