WO2007141455A2

WO2007141455A2 - Method for preparing a composite material capable of being formed by impregnating a fibre reinforcement, resulting material and components prepared from same

Info

Publication number: WO2007141455A2
Application number: PCT/FR2007/051377
Authority: WO
Inventors: Manfred Buchler; Michel Davidovics
Original assignee: Pyromeral Sas
Priority date: 2006-06-06
Filing date: 2007-06-05
Publication date: 2007-12-13
Also published as: WO2007141455A3; FR2901786B1; FR2901786A1

Abstract

The invention concerns a method for preparing a composite material capable of being formed, which consists in impregnating a fiber reinforcement with a reaction mixture in the form of an aqueous composition. The invention also concerns the resulting material and components prepared from said material.

Description

PROCESS FOR PREPARING A COMPOSITE MATERIAL FORMABLE BY

IMPREGNATION OF A FIBROUS REINFORCEMENT, MATERIAL THUS OBTAINED AND

PARTS PREPARED FROM THIS MATERIAL

The present invention relates to the field of composite materials for the manufacture of parts resistant to very high temperatures. Indeed, there is today a need for composite materials allowing the realization in economically acceptable conditions of complex shapes, light, thin, useful as structural elements that can be exposed to temperatures of the order of 350 ⁰ C at 1000 ⁰ C for significant periods and at much higher temperatures for short periods.

In such conditions of temperature, conventional ceramics and glasses are not usable because too fragile. Metals are heavy, they expand and often lead to heat. Most plastics and composites with organic matrix destroy themselves quickly above 200 ⁰ C, and none durably resistant to more than 400 ⁰ C. Graphites or composites with carbon matrix are resistant durably to high temperatures only in a neutral or reducing atmosphere. Composite materials with a ceramic or glass matrix produced by deposition or infiltration techniques in the gaseous or liquid phase require long and costly elaboration processes that do not make it possible to obtain all the shapes of parts with small thicknesses.

Many attempts have been made using low temperature thermosetting silicates or alumino-silicate compounds as binders fibrous reinforcements to make elements of composite materials resistant to fire and high temperatures.

Prior art, in particular PCT patent applications published under the numbers WO 88/02741, WO91 / 13830, WO 9113840 and WO 96/28398, discloses materials based on binders and heat-curable matrices of the Alumino type. alkali silicates called geopolymers or polysialates these materials can be implemented according to the usual processes for manufacturing parts made of organic composite materials.

These processes comprise in particular: first the impregnation of short or long unit fibers, or fibrous textile reinforcements before, during or after their shaping with said polysialate binders, this impregnation can be done by bathing, removal, transfer or injection or any other appropriate technique,

and then shaping, possibly under vacuum or under pressure, or by combining the two, by techniques such as casting, pressing, laminar draping molding, injection molding, extrusion, pultrusion, filament winding, transfer molding or injection molding. resin, etc., and finally, a firing which is done by heating the material during or after shaping at low temperatures, preferably about 40 ⁰ C to 180 ⁰ C; this heating can be achieved by any means in the tooling or outside, in a chamber or by an external heat source, or by heating systems incorporated in the material or using the material itself. During cooking, the formed element will preferably remain under vacuum or pressure or both.

The piece is then demolded and possibly deburred and machined. The elements thus manufactured can be exposed to temperatures up to about 1000 ⁰ C while undergoing significant mechanical stresses. The fibrous reinforcements must of course be adapted, and compromises must be found between the duration of exposure, the amplitude and the frequency of the thermal cycles and the mechanical stresses undergone.

Nevertheless, a systematic weakening of the silicate, alumino-silicate or polysialate matrix is always observed when the operating temperatures exceed about 400 ^° C. This is due to a significant swelling of this matrix at high temperature. In many situations, an increase in the thickness of the material makes it possible to impart an acceptable mechanical resistance to the pieces, but to the detriment of the weight of the piece formed and its cost.

The materials obtained with the matrix described in the PCT patent application published under the number WO 96/28398, have substantially improved the oxidation behavior of the carbon fiber at high temperature, but they do not provide a solution to obtain structural mechanical characteristics for several days at temperatures above 400 ^° C. The carbon fiber is attacked despite the protection of the matrix and the matrix itself is deformed and becomes weakened.

The need for a composite material and a method for easily making parts having and retaining good structural characteristics when working sustainably, i.e., from several hours to several weeks in a high environment temperatures and undergoing significant mechanical stress is still not satisfied.

The present invention aims precisely to provide a technically and economically satisfactory solution to have a composite material capable of allowing the manufacture of parts resistant to very high temperatures.

The research work carried out by the applicant has enabled it to prepare composite fiber-reinforced composite parts having as matrix particular compositions of alkaline aluminosilicates. These low-temperature thermoformed parts have structural mechanical characteristics at high temperature substantially and durably improved through heat treatment carried out according to a suitable cycle, and at temperatures at least greater than their vitrification temperature is generally more than 600 ^° C. The result is obtained without having to keep the pieces in their mold, or to exert pressure or depression to keep their shape and dimensions during and after the heat treatment.

Indeed, the incorporation of agents known to be glass formers in an aqueous reaction mixture of alkali metal aluminosilicates with a high SiO ₂ / Al ₂ O ₃ molar ratio makes it possible to have a matrix for a fiber-reinforced composite material which can be transformed into glass when it is brought to its melting temperature after curing. It is thus possible to prepare glass-matrix composite parts with good accuracy, therefore with very little deformation, expansion or shrinkage with respect to the part before the vitrification phase. These parts have high temperature mechanical characteristics which are largely and durably improved compared to those obtained with a material without this heat treatment, or obtained with a heat-treated material but without the matrix being modified by the addition of glass-forming agents. Thus, it is possible to consider that this matrix is rather of the "glass" than "ceramic" type because it contains components usually used for the manufacture of glass and has gone through a melting stage. The composite materials obtained from this matrix have good mechanical properties at high temperatures, they are also light, expand little, conduct little heat, are machinable, repairable and even self-healing. Self-healing is understood to mean that the fissured matrix can be bonded by a simple exposure to its melting temperature, without any particular process of repair.

Thus, the subject of the invention is a reaction mixture in the form of an aqueous composition of alkaline aluminosilicates comprising: siliceous sources of aluminosilicate oxides with a raw composition of (2 SiO ₂ , AlO ₂ ) and (82.5 SiO ₂ , AlO ₂ ), an aqueous solution of alkali silicate or alumino-silicate, glass-forming agents, rheology agents or surface modifiers, the assembly prepared to have a SiO ₂ molar ratio. / Al ₂ C> 3 expressed in terms of oxides in the dehydrated state of between 6.5 and 165, and preferably between 24 and 95.

The incorporation into the reaction mixture of inorganic or organic compounds compatible with the medium of alkaline silicates, such as binders, gelling agents, accelerators or set retarders can improve the behavior of the reaction mixture during its preparation, storage, implementation. and the quality of materials obtained. The applicant has notably found that the presence of sugars, sugar compounds, sorbitols, fatty acids, glycerols or glycols known elsewhere to improve the drying of silicate-based coatings, surprisingly improved the qualities of impregnation of a fibrous reinforcement with the reaction mixture, as well as the properties of implementation of the impregnated fibrous reinforcement, both for the duration of use and its ability to be positioned and shaped. This reaction mixture may be carried out in one or more steps, each step may comprise a maturation time and storage time under suitable conditions. The final mixture can itself be matured and stored under suitable conditions.

The invention also relates to the impregnation of a fibrous reinforcement of this reaction mixture.

The impregnated fibrous reinforcement is shaped, most often by placing it in or against a mold or by passing it through a forming tool. Then it is thermoset, this thermosetting being carried out at low temperature, between 40 ⁰ C and 350 ⁰ C, preferably between 60 ⁰ C and 180 ⁰ C, advantageously under vacuum and / or under pressure, in or against the mold or the tool of forming.

The formed body constituting the workpiece is then removed from the mold of the forming tool, or from the holding support in shape, and then placed immediately or after cooling in an oven and carried gradually stepwise to a temperature where the matrix is transformed. glass generally around 800 ⁰ C and for a few hours. This post-cooking and vitrification phase can be broken down into several operations to adapt the process to the desired equipment and rates.

The formed body is then cooled in or out of the oven, in a controlled manner or not depending on the nature of the glass of the matrix.

The process of the invention is remarkable in that, surprisingly, the matrix sufficiently holds the fibrous reinforcement to prevent it from deforming, even at the vitreous transformation temperature of the matrix. In addition, the composition and the density of the matrix after its thermosetting, as well as the quality of impregnation of the fibrous reinforcement that it allows to obtain, then the vitrification process steps are such that the glass formed during vitrification provides sufficient mechanical and dimensional characteristics to the final material for long-term, high-temperature structural use.

The vitreous matrix piece thus obtained may be the subject of all the additional operations to make it fit to perform its function. It can be post-processed to confer special qualities. It can be deburred, and machined provided with fasteners, fasteners, or protection elements according to generally known techniques. It can be integrated with other mechanical parts, thus making it possible to break down in a mechanical assembly the heat resistance function of the other functions, such as, for example, the protection against shocks or the environment in general or the reworking of efforts.

It is also possible to insert during the initial forming any other element or material necessary for the function of the part, such as, for example, reinforcements, stiffeners, conductive materials, sensors, conduits, fasteners, insulating materials.

Other elements can be added to the part by overmoulding after thermosetting or after vitrification.

The invention makes it possible to easily obtain a glass-matrix composite formed part by dispensing with the necessity of densification of the matrix by high-temperature pressure in a mold. The invention makes it possible to generalize the use of such materials to areas for which they had prohibitive costs, or for which the manufacture of parts was technically impracticable, such as high performance heat shields, handling elements, support elements. or structural steel subjected to high temperatures, hot fluid conduits, thermal protection parts in the environment of engines, turbines and nacelles in industry, automobile and aviation, flaps and air guides or hot gases, turbine rotor blades, and more generally, all areas requiring parts having structural characteristics at high temperatures.

The invention therefore relates more particularly to a process for preparing a formable composite material, of the type consisting in impregnating a fibrous reinforcement with a reaction mixture in the form of an aqueous composition, characterized in that the content of water of said aqueous composition is between 5% and 40% of the weight of the composition, said composition comprising: compounds selected from the group consisting of silica oxides, alkali silicates and alkaline aluminosilicates, a portion of which is dissolved form, and the other part in the form of particles in suspension, and in a proportion such that the molar ratios of all these compounds, expressed in terms of oxides after dehydration, are between:

M ₂ CVSiO ₂ : 0.03 and 0.145 SiO ₂ / Al ₂ O ₃ : 6.50 and 165 M ₂ CVAl ₂ O ₃ : 0, 95 and 15

M representing an atom of Na, K, or Li or a mixture of two or all of them, and these compounds representing between 40 and 94.4% by weight of the composition; one or more glass forming agents or modifiers, at least one of which is selected from the group consisting of oxides, acids, salts or other forms of the following elements: Ge, B, P, As, Sb, Te,

Mo, W, Bi, Ga, V, Cr, Mn, Zr, Ti, Cd, Ga, Ca, F, the total weight of these agents, expressed by weight of their dehydrated oxides, being between 0.5% and 50%, preferably between 0.5 and 35% and most preferably between 0.5 and

15% of the weight of the dehydrated composition;

one or more rheological agents and / or modifiers of the surface characteristics of the liquids, such as surfactants or surfactants, in an amount of between 0.1% and 5% of the weight of the composition; one or more inorganic or organic compounds compatible with an alkaline silicate medium, selected from the group consisting of binders, gelling agents and accelerators or retarders of setting, sugars and sugar compounds, sorbitols, fatty acids , glycerols or glycols, in an amount of between 0 and 20% of the weight of the dehydrated composition. Advantageously, the aqueous composition comprises:

particles composed for more than 80% of their weight of silica oxides, of non-laminated structure, of dimension between 50 nm and 1 micron, preferably between 100 nm and 1 micron, undissolved even after maturation of the composition for more than one hour, these particles representing between 30% and 95% by weight of the dehydrated composition, and an aqueous alkaline silicate aqueous solution phase representing between 5 and 70% by weight of the dehydrated composition.

SiO 2 can come from all known sources of SiO 2, for example and without limitation sands, quartz, silica flours, glass powders, alkali silicates prepared in solution or solids, colloidal silica, precipitated silica, silica gels natural or synthetic aluminosilicate compounds, fumed silica or aluminosilicates. A significant part of the sources of SiO 2 will be chosen from siliceous or silico-aluminate compounds which do not dissolve completely in the reaction mixture even after maturation, impregnation and hardening, leaving mainly siliceous oxide particles of non-flake structure , of dimensions between 50 nm and 1 micron, preferably between 100 nm and 1 micron, for a level of between 30% and 90% of the reaction mixture counted in the dehydrated state.

Thus, preferably at least one third of the SiU2 input into the reaction mixture is made by silica fumes, which will be referred to hereinafter as "silico-aluminated silica fumes" comprising a silico-aluminate part such as formula of this silica fume is between (2Siθ2, AlC> 2) and (90SiO ₂ , AlO ₂ ) • Such silico-aluminated silica fumes come for example from the condensation and cooling of vapors produced at temperatures above 1800 ⁰ C and preferably above 2000 ⁰ C during electro-fusion of natural or synthetic compounds, sands, minerals or ores containing silica and alumina, or during the joint fusion, for example under a plasma torch, of silica and alumina as described for example in the patent application WO 96/28398 (page 5 lines 29 to 37 and page 6 lines 1 to 36). Depending on the nature of the compound (s) subjected to melting, oxides of various elements may be present in the silica-silico-aluminate fumes in addition to the oxides of Si and Al, for example Fe, C, Zr oxides. , Cr, Ti etc., some of which may have an effect on the kinetics of hardening of the matrix or on the formed glass.

Thus, it is preferred according to the process of the invention that at least 30% of the SiO ₂ oxide of the aqueous composition is provided in the form of a powder containing mainly an aluminosilicate oxide in which the number of elements Si and Al is such that its formula is between the following two formulas:

(2SiO ₂ , AlO ₂ ) and (82.5SiO ₂ , AlO ₂ ) said alumino-silicate oxide resulting from the condensation and cooling of vapors produced at temperatures above 1800 ⁰ C and preferably above 2000 ⁰ C during the electro-fusion of natural or synthetic compounds, sands, minerals or ores containing silica and alumina, or during the fusion-vaporization joint of silica and alumina, under a plasma torch for example at temperatures above 2000 ° C. The main part of the aluminosilicate oxides of the aqueous composition of the process of the invention comprise reactive Al sites allowing crosslinking of geopolymeric type during the rise in temperature.

The term "geopolymeric type crosslinking" is understood to mean the curing at a temperature ranging from room temperature to less than 200 ^° C. of alkaline aluminosilicates forming an amorphous or semi-crystalline structure of aluminosilicate oxides, probably as tetrahedra SiO4 and AlO4 sharing the oxygen atoms, and comprising positive ions to balance the negative charge of the AI in coordination IV. The Al oxides can come from all the aluminosilicate compounds. Preferably, those having the cation Al in coordination (IV or V) such as, for example, the oxide (SiO.sub.2, Al.sub.2O.sub.2), the silica fumes having a silicoaluminate part, in particular the silica-silico-aluminate fumes described herein. -above. These Al reactive sites can also be obtained by mechanical synthesis of aluminosilicate powders.

The aqueous composition used in the process according to the invention also has at least one of the following characteristics:

At least one of the glass forming or modifying compounds of the composition is based on boron, fluorine or phosphorus, for a total weight, expressed in terms of their dehydrated oxides, of between 0.5% and 15% by weight. relative to the weight of the dehydrated composition.

The rheology agents or modifiers of the surface characteristics of the liquids are chosen from the group comprising anionic surfactants, cationic, nonionic, or a mixture of two or more thereof, such as quaternary ammonium salts, alkyl-aryl sulfonates, organoamine salts.

At least half of the suspended particles are:

. of substantially spherical shape,. of diameter between 100 nm and 1 micron, consisting of an alumino-silicate compound with a quantity defined between the following two formulas: (24 SiO ₂ , AlO ₂ ) and (90 SiO ₂ , AlO ₂ ),

. includes not more than 5% by weight of compounds or oxides other than those of Si and Al.

Thus, by formative agents or glass modifiers are meant those other than the oxides of silica or aluminum or the oxides and hydroxides of K, Na, Li that we consider to constitute the very substantial network of the matrix, but that some include in the terminology "glass formers". The forming agents or glass modifiers may modify the kinetics of the curing reaction of the reaction mixture, but do not play any effective role of hardener during the phases of preparation of the mixture, impregnation and curing of the matrix. On the other hand, they are determinants during the vitrification phase in order to give the matrix the characteristics such as the temperature and the melting mode, the expansion, the viscosity, the wettability and more generally the structure, the mechanical characteristics, the behavior and the sensitivity to glass chemicals during and after processing.

The forming agents or glass modifiers are chosen from compounds providing the so-called forming elements or glass modifiers such as, for example, without limitation, the oxides of Ge, B, P, As, Sb, Te, Mo, W, Bi, Ga, V, Cr, Mn, Zr, Ti, Cd, Ga, Ca, F, the incorporation rate of each expressed by weight of their oxides, which may range from trace amounts up to 15% of the reaction mixture counted as dehydrated, the weight expressed as oxides of all the chosen agents must represent between 0.5 and 15% of the weight of the reaction mixture counted as dehydrated .

Their incorporation into the reaction mixture may be in the form of oxides, acids, salts or any other solid, liquid or gaseous compound suitable for the preparation of the reaction mixture.

The rhelogic agents or surface modifiers are chosen, for example, from anionic, cationic and / or nonionic surfactants, such as, but not limited to, quaternary ammonium salts, alkyl-aryl sulfonates, organoamine salts, or combination of them.

Their level of incoporation is between 0.1% and 5% by weight of the reaction mixture.

The preparation of the reaction mixture is generally carried out by first preparing an aqueous solution of alkali silicate or alumino silicate by incorporating at least one source of SiO ₂ in an aqueous alkaline solution such as sodium hydroxide solution, potassium hydroxide solution or lithium hydroxide solution. and then mixing the other components with this silicate or alkali silico-aluminate.

Some components may be incorporated from the preparation of the alkali silicate depending on dissolution requirements, exothermic or rheology, for example.

The heat supply can favor or accelerate certain phases of the preparation. It may be advantageous to make these mixtures by cooling and / or by creating a vacuum in the mixer.

For use in impregnating fibrous reinforcement the viscosity of the reaction mixture is adjusted with water during or after preparation, before or after storage.

The final water content of the reaction mixture will be between 5% and 40% of its weight. The reaction mixture thus obtained in one or more steps is subjected to a maturation at room temperature or controlled for a time not generally exceeding one hour, and depending on its composition, until dissolution of the siliceous or aluminosilicate compounds other than those specially chosen not to dissolve during this phase, such as those from silico-aluminated silica fumes which remain in suspension for the most part in the form of spherical nodules with a diameter of less than 1 micron, even after one hour of reaction mixture at room temperature.

The reaction mixture can be used immediately after ripening, or stored frozen, in which case it must be thawed gradually before use.

The reaction mixture may comprise gel modifiers or plasticizers known to produce their effects in the alkali silicate field.

Any reagents or agents may optionally be incorporated in the reaction mixture in order to obtain a particular nature, structure, appearance or behavior of the formed glass, after vitrification of the matrix. These agents or reagents can be extracted from industry literature and from ceramic and glass research. A simple test will verify their compatibility with the requirements of the process object of the present and if they actually provide the modification provided by the literature on the formed glass matrix.

Similarly, it is optionally possible to add to the reaction mixture fine glass particles whose diameter may vary from 100 nm to less than one micron, these particles may contribute usefully to the formation of the "glass" matrix.

Any product modifying the interface of the matrix with the fibrous reinforcement can also be incorporated in the reaction mixture. These are for example known products in the literature to enter the physical and chemical constitution of specific fibers and for their temperature behavior in a porous alkaline matrix. A simple adaptation test will often make it possible to verify their compatibility with the requirements of the process that is the subject of this document and to provide the modification provided for in the literature.

According to the Applicant's experience in alkaline aluminosilicate temperature hardening processes often referred to as geopolymerics, the possibilities of varying the molar ratios of this type of compounds as well as the curing temperatures and pressures make it It does not appear necessary in most cases to add hardeners such as those commonly used in the alkali silicate chemistry. Their addition to the reaction mixture can modify the kinetics of hardening without necessarily harming it.

It may be useful to add to the reaction mixture one part of organic resin compatible with the alkaline conditions thereof that can mix intimately with it and harden according to a similar cynetic polymerization. In this case, the proportion of this resin should not exceed 20% by weight relative to the aluminosilicate part (M ₂ O + SiO ₂ + Al ₂ Os) •

According to the process of the invention, the impregnation of the fibrous reinforcement is carried out by dipping followed or not by spinning, or by depositing a quantity determined by spraying, spraying or else by licking or transfer, or by infiltration, one or more operations.

The impregnation is advantageously carried out by exerting a depression on the fibrous reinforcement and possibly again under controlled temperature. Preferably, after impregnation, the water content of the aqueous composition is brought back to a content by weight of between 5% and 15% by weight of the composition, for example by evaporation carried out at a temperature of between 20 ^° C. and 45 ° C. optionally under vacuum, preferably before the material is shaped for its thermosetting.

The use of the vacuum during the impregnation can be advantageous. It becomes even essential in the case where the fibrous reinforcement is in place in a closed mold during the impregnation.

The fibrous reinforcement is dried to give it the necessary state to be put in place in the forming tool.

In the case of the preparation of a formable composite material of BMC type for "BuIk Molding Compound" according to the process of the invention, the fiber reinforcement is cut into small pieces or short fibers whose dimension is preferably between 0, 1 mm and 5 cm. The fibers can thus be in cut form from a few tens of microns in length to continuous fibers over several meters. They may, in order to constitute the fibrous reinforcement, be isolated in bulk, isolated continuously, grouped unidirectionally or pluridirectionally in a random or organized manner, woven or non-woven, knitted pressed or any other shaping, including with the aid of a small amount of binder or primer. Thus, the fibers constituting the reinforcement are chosen from those known to withstand without significantly losing their characteristics at temperatures ranging from 350 ⁰ C to above 1500 ⁰ C continuously under oxidizing conditions. The fiber reinforcement is, for example, made of fibers selected from the group consisting of carbon, glass, basalt, metal, ceramic and silicon carbide fibers.

According to a particular embodiment of the process of the invention, the formable composite material is wrapped with one or more films of organic polymer that is airtight, or it is placed sandwiched between two films of organic polymer that is impermeable to air. air, preferably less than 60 minutes after its impregnation and in that it is stored at a temperature below 0 ^° C., and preferably between -5 ° C. and -25 ° C.

The fibers may be specially treated to improve their resistance to the alkalinity of the reaction mixture.

The present invention also relates to a formable composite material capable of being prepared by the method described above. Such a formable composite material comprises a fibrous reinforcement impregnated with a reaction mixture in the form of an aqueous composition of aluminosilicates whose water content is between 5% and 15% of the weight of the composition, said composition comprising compounds selected from the group consisting of silica oxides, alkali silicates and alkaline aluminosilicates, part of which is in dissolved form, and the other part in the form of particles in suspension, and in a proportion such that the molar ratios of all these compounds, expressed in terms of oxides after dehydration are between:

M ₂ CVSiO ₂ : 0.03 and 0.145 SiO ₂ / Al ₂ O ₃ : 6.50 and 165

M ₂ CVAl ₂ O ₃ : 0, 95 and 15

M representing an atom of Na, K, or Li or a mixture of two or all of them, and these compounds representing between 65% and 94.4% by weight of said composition; one or more forming agents or glass modifiers, at least one of which is selected from oxides, acids, salts or other compounds of the following elements: Ge, B, P, As, Sb, Te, Mo, W, Bi, Ga, V, Cr, Mn, Zr, Ti, Cd, Ga, Ca, F, the total weight of these agents, expressed by weight of their dehydrated oxides, being between 0.5% and 15% of the weight of the composition dehydrated;

one or more rheological agents and / or modifiers of the surface characteristics of the liquids, such as surfactants or surfactants agents, in an amount of between 0.1% and 5% of the composition; one or more inorganic or organic compounds compatible with an alkali silicate medium, chosen from the group comprising the binders, gelling agents and accelerators or retarders of setting, sugars and sugar compounds, sorbitols, fatty acids, glycerols or glycols in an amount of between 0 and 20% of the weight of the dehydrated composition; this material is further characterized in that the weight of the reaction mixture in the dehydrated state is between 75% and 30% of the weight of the formable composite material in the dehydrated state. The fibrous reinforcement representing between 25% and

70% by weight of said dehydrated formable composite material.

As indicated above, the fiber reinforcement consists of fibers selected from the group consisting of carbon, glass, basalt, metal, ceramic and silicon carbide fibers.

In a preferred version of the formable composite material:

The MASNMR spectrum of the reaction mixture for 29Si has the following three resonance zones -87 + -5ppm, -98 + -5ppm, -107 + -5ppm.

The MASNMR spectrum of the 27Al reaction mixture has one or more of the following resonance zones -55 + -5ppm, -65 + -5ppm, -70 + -5ppm, indicating that the coordination of Al is AlO ₄ . In this case, the Al reactive sites are advantageously constituted by Al coordination cations (IV) and / or (V).

According to the process of the invention, in the formable composite material, at least one of the glass-forming or modifying compounds is based on boron, fluorine or phosphorus, for a total weight, expressed in terms of their dehydrated oxides. , between 0.5% and 15% relative to the weight of the dehydrated composition. The composite material thus prepared can be used immediately. It can also be sandwiched between two plastic films or wrapped in a plastic film, so that it can be stored for some time, preferably in the cold or in the frozen state. It can also be finely cut to prepare a compound of the type BMC "BuIk Molding Compound" can easily be shaped by pressing or extrusion for example. The lengths of impregnated fibers then cut will in this case advantageously but not limitatively lengths ranging from a few tenths of mm to a few centimeters. This BMC compound may also be granulated using known binders and techniques. This is of particular interest because there has been no possibility until now to produce high performance formable composites of the type BMC silicate matrix or silico-aluminate alkali because of the difficulty of impregnating a short fiber fiber reinforcement in bulk representing 30% or more of the weight of the composite material. The impregnated fibrous reinforcement is shaped and cured according to the techniques known in the composite materials industry, such as not limited to compression molding in open or closed mold, laminar layering by vacuum or non-vacuum superposed folds, in an autoclave or no, filament winding, pultrusion, extrusion, injection, transfer molding, infusion or injection of the reaction mixture, casting with or without vibration, etc.

Several phases using successively or in parallel one or more of the shaping techniques may be necessary for making a formed part. This may be useful for inserting reinforcements, fasteners or insulating materials, for example. The matrix is hardened by heat, during or after shaping the impregnated fiber reinforcement, between 40 ^° C. and 350 ^° C. and preferably between 60 ^° C. and 180 ^° C., at pressures ranging from atmospheric up to the usual pressure levels for processing high performance composite materials, for example at 35 bar autoclave or much more if using pressing, optionally vacuum under-bar, or under vacuum and simultaneous pressure.

The matrix at this stage, after curing, is characterized, (i) firstly that it is composed at 80 to 99.5% of its weight by a structure of alkaline aluminosilicates whose ratios Molars expressed in terms of oxides after dehydration are:

- yM2O: AL2O3: xSiO2, in which "x" is a value between 6.5 and 150, "y" is a value between 1 and 25, "M" being either Na, or K, or Li, or a mixture of two or three of them; and (ii) on the other hand, by the presence within:

A first siliceous nodular phase composed of particles of non-laminated structure, often of spherical shape, of diameter less than 1 micron, preferably less than 500 nm, this siliceous nodular phase representing between 30 and 95% by weight of the matrix.

A second polymeric phase consisting essentially of poly (aluminosilicate) and having the characteristics of the geopolymeric bonds as described and characterized in the PCT patent application published under the number WO 96/28398, this second phase representing from 10 to 50 parts in weight of the matrix, and containing the oxides of forming elements or glass modifiers described above.

The formed part is then cooled and removed from the mold, or more generally from its forming support. It is then subjected to a heat treatment to carry it progressively in one or more operations and in stages to the melting temperature of the matrix to form the glass, this without it being necessary to contain or maintain in shape and without of course to exert pressure to densify the matrix being transformed

The Applicant has noted with surprise that the composition of the matrix makes it possible to obtain, by melting, a remarkable density of the matrix. The melting temperature of the matrix is preferably between 600 ^° C. and 1200 ^° C., and depends on the nature of the glass to be formed. The vitrification treatment can be done optionally under a controlled atmosphere. The total duration of the heat treatment cycle can vary from 15 minutes to more than 24 hours.

The invention therefore also relates to a process for manufacturing a formed composite material part comprising shaping a formable composite material described above, and its curing by heating during and / or after the setting at a temperature of between 40 ^° C. and 350 ^° C., preferably between 60 ^° C. and 180 ^° C., under a pressure of between atmospheric pressure and about 1500 bar under vacuum or otherwise. Preferably, the hardening is carried out in an autoclave under a pressure of 5 to 35 bar under vacuum or not.

The shaping can be carried out by a molding technique chosen from the group comprising the compression in open or closed mold, or between continuous rolls, laminar layup by superimposed folds in a mold, under vacuum or not, filament winding or strips, pultrusion, extrusion, injection, molding by transfer-infiltration or resin injection.

The invention also relates to a part made of composite material that can be manufactured by the above method. Such a composite material formed part is characterized in that it consists mainly of a fibrous reinforcement and a matrix, the fibrous reinforcement representing by weight between 25 and 75% of the piece and the matrix representing by weight between % and 75% of the part in the dehydrated state, and in that the matrix after dehydration consists of: for 80 to 99.4% of its weight, one or more alkaline silico-aluminate compounds such as the molar ratios of all of its alkali silicoaluminate compounds expressed in terms of oxides after dehydration are between:

M represents an atom of Na, K, or Li or a mixture of two or all of them; one or more forming agents or glass modifiers, at least one of which consists of an oxide of the following elements: Ge, B, P, As, Sb, Te, Mo, W, Bi, Ga, V, Cr, Mn , Zr, Ti, Cd, Ga, Ca, F, the total weight of these agents expressed by weight of their dehydrated oxides being between 0.5% and 15% of the weight of the matrix and enclosed in the aluminosilicate matrix; one or more inorganic or organic compounds enclosed in said matrix and originating from residues, after polymerization of the matrix, rheology agents and surface modifiers and various inorganic or organic compounds incorporated in the reaction mixture for a maximum content between 0.1 and 15% of the weight of said dehydrated reaction mixture; this piece is further characterized in that said matrix is in the form of a nanocomposite structure comprising at least two phases: a first nodular phase composed of siliceous particles, of non-laminated structure, with dimensions of between 50 nm and 1 micron, of preferably between 100 nm and 1 micron, these particles representing between 30% and 95% by weight of the matrix,

a second phase consisting mainly of a mainly amorphous silico-aluminate structure embedding the nodular phase and containing at least one of the following oxides: Ge, B, P, As, Sb, Te, Mo, W, Bi, Ga, V, Cr, Mn, Zr, Ti, Cd, Ga, Ca, F, the total weight of these oxides expressed by weight of their dehydrated oxides being between 0.5% and 15% of the weight of the matrix.

In this composite material part, at least half of the particles of the nodular phase are spherical in shape. In addition, in a preferred version, the matrix has at least one of the following characteristics:

it possesses a 29Si MASNMR spectrum having the following three resonance zones: -87 + -5ppm, -98 + -5ppm, following -107 + -5ppm. it has a MASNMR spectrum for 27Al having one or more of the following resonance zones: -55 + -5ppm, -65 + -5ppm, -70 + -5ppm, these indicating that the coordination of Ai is AIO ₄ .

The vitreous matrix formed part can be subjected to various post-treatments, possibly at high temperatures, such as by liquid or gaseous infiltration or solid, liquid or gaseous deposition, painting, coating, enameling or any other surface treatment. These treatments can improve porosity, watertightness, friction characteristics, resistance to oxidation of fibers, reflection or absorption of waves and radiation, electrical insulation or conduction, hardness appearance or any other purpose.

Thus, the invention also relates to a method for obtaining a workpiece formed of composite material with fiber reinforcement and mainly glass matrix, characterized in that it consists in heating a workpiece as described above at a temperature greater than the melting temperature of the main components of the matrix for at least 15 minutes. Advantageously, the part is heated to a temperature of between 600 ^° C. and 1500 ^° C. This heating may be carried out under a non-oxidizing controlled atmosphere.

This method is remarkable in that the formed piece is not contained, maintained or supported by a mold or a support constituting a negative of the piece formed on more than 20% of its non-planar surface. The invention also relates to a piece formed of composite material with fiber reinforcement and mainly glass matrix obtained by the above method. This piece is characterized in that the MASNMR spectrum of the matrix for 27Al has one or more of the following resonance zones: -55 + -5ppm, -65 + -5ppm, -70 + -5ppm, the latter indicating that the coordination of Ai is A1O4.

The invention finally relates to a reaction mixture which can be used in the process for preparing a formable composite material of the invention. A reaction mixture according to the invention is in the form of an aqueous composition whose water content is between 5% and 40% of the weight of the composition, and in that it comprises: compounds selected from the group comprising silica oxides, alkali silicates and alkali aluminosilicates, one part of which is in dissolved form, and the other part in the form of particles in suspension, and in such a proportion that the molar ratios of all these compounds, expressed in terms of oxides after dehydration, are between: M ₂ CVSiO ₂ : 0.03 and 0.145 SiO ₂ / Al ₂ O ₃ : 6.50 and 165 M ₂ CVAl ₂ O ₃ : 0.95 and 15

M representing an atom of Na, K, or Li or a mixture of two or all of them, and these compounds representing between 40 and 94.4% by weight of the composition; one or more forming compounds or glass modifiers, at least one of which is selected from the group consisting of oxides, acids, salts or other forms of the following elements: Ge, B, P, As, Sb, Te, Mo, W, Bi, Ga, V, Cr, Mn, Zr, Ti, Cd, Ga, Ca, F, the total weight of these agents, expressed by weight of their dehydrated oxides, being between 0.5% and 15% of the weight of the dehydrated composition;

one or more rheological agents and / or modifiers of the surface characteristics of the liquids, such as surfactants or surfactants, in an amount of between 0.1% and 5% of the weight of the composition; one or more inorganic or organic compounds compatible with a silicate medium alkalis, selected from the group consisting of binders, gelling agents and accelerators or retarders, sugars and sugar compounds, sorbitols, fatty acids, glycerols or glycols, in an amount and 20% by weight of the dehydrated composition.

This reaction mixture is further characterized in that the aqueous composition comprises:

Preferably, at least 30% of the SiO ₂ oxide of the aqueous composition is provided in the form of a powder mainly containing an aluminosilicate oxide in which the number of elements Si and Al is such that its empirical formula is located between the following two formulas: (2SiO ₂ , AlO ₂ ) and (82.5SiO ₂ , Al ₂ O ₂ ) said alumino-silicate oxide resulting from the condensation and cooling of the vapors produced at temperatures above 1800 ⁰ C and preferably greater than 2000 ⁰ C during the electro-fusion of natural or synthetic compounds, sands, minerals or ores containing silica and alumina, or during the fusion-vaporization joint silica and alumina , under a plasma torch for example at temperatures above 2000 ° C. Preferably, in this reaction mixture, the main part of the aluminosilicate oxides of the aqueous composition comprises reactive Al sites allowing crosslinking of geopolymeric type during the rise in temperature. Thus, the Al reactive sites consist of Al coordination cations (IV) and / or

(V).

Preferably, this reaction mixture has at least one of the following characteristics: at least one of the glass-forming or modifying compounds is based on boron, fluorine or phosphorus, for a total weight, expressed in terms of their dehydrated oxides, between 0.5% and 15% relative to the weight of the dehydrated composition. - The rheology agents or modifiers of the liquid surface characteristics are selected from the group consisting of anionic, cationic, nonionic surfactants, or a mixture of two or more thereof, such as quaternary ammonium salts, alkyls -aryl sulfonates, organoamine salts. at least half of the suspended particles are:

. of substantially spherical shape,. of diameter between 100 nm and 1 micron, consisting of an alumino-silicate compound in an amount defined between the following two formulas: (24 SiO ₂ , AlO ₂ ) and (90 SiO ₂ , AlO ₂ ), includes not more than 5% by weight of compounds or oxides other than those of Si and Al.

Other features and advantages of the invention will become apparent from the following examples due in particular to the influence of glass formers and to the presence of nanoparticles: showing the difference due to the addition of glass forming agents.

EXAMPLE 1

490 g of a reaction mixture containing: H 2 O 7 moles; K 2 O 0.552 moles; SiO 2 5.018; AI 2 O 3 0.078 moles.

AI2O3 comes from an amorphous silico-aluminated silica fume prepared by electrofusion of silico-aluminate natural, whose particle size is less than 1μn, and an Al content of about 2.5%; Sio2 comes from this same silica fume and a solution of potassium silicate. K2O comes from a 50% potash solution. The assembly is adjusted so that the molar ratio of the reaction oxides is equal to:

245 g of this reaction mixture are taken and left to mature for 1 hour (mixture A).

The remaining 245 g of the reaction mixture are withdrawn and 0.019 moles of B are added to the glass-forming agents; 0.020 moles of F. B is derived from a boric acid and F from a fluosilicate.

This mixture is allowed to mature for 1 hour (mixture B); After ripening, blends A and B are used separately to impregnate a silicon carbide fiber (tyranno) fabric with 0 / 90-200 g / m2 orientation. It is arranged that the ratio between weight of fiber and the weight of the reaction mixture is 45/55. So we have two impregnated fabrics, one of the mixture A (Mat A) the other of the mixture B (Mat B).

Two samples are made of formable composite materials (Mat A and Mat B) 2 mm thick comprising 10 layers of impregnated fabric, and then placed on a metal plate on which a vacuum cover is made. The two composite samples are left under vacuum for 1 hour at room temperature in order to extract the maximum amount of air. The metal plate with the two samples and the vacuum tank is then placed in an autoclave where the samples will undergo 6 bars of pressure and 120 ⁰ C of temperature for 3 hours.

The samples of composites Mat A and Mat B are removed from the autoclave and are positioned in an oven for post-baking (ceramization-vitrification) at 750 ⁰ C for 1 hour. After this aftercooking, the flexural strength and the modulus are measured at room temperature.

RF Module

Mat Sample A 90Mpa 18

Sample Mat B 173MPa 36

The addition of glass forming agents such as the

Boron and Fluorine allowed an increase in flexion characteristic of 52% and 100% modulus

EXAMPLE 2

200 g of a reaction mixture comprising H 2 O 5.71 moles are prepared; K 2 O 0.451 moles; SiO 2 4.096 moles, to which are added 0.0155 glass forming agents of B and 0.0163 of F. K2O comes from a solution of 50% potassium hydroxide and SiO 2 from a silica fume originating from the manufacture of ferro-silicon, with a particle size of less than 1 μm.

B is derived from a boric acid and F from a Fluosilicate.

After ripening, a sample of the reaction mixture is taken and placed between two thin slides to be observed under a 20x magnification. The observation shows that the mixture is translucent and contains no undigested particles.

A sample of composite material is produced with this reaction mixture as in Example 1.

After post-baking, the sample is 10.6mm thick and its mechanical characteristics can not be measured.

200 g of a reaction mixture comprising H 2 O 5.71 moles are prepared; K 2 O 0.451 moles; SiO 2 4.096 moles, to which are added 0.0155 glass forming agents of B and 0.0163 of F.

K2O comes from a solution of 50% potassium hydroxide and SiO 2 of an amorphous silico-aluminated silica fume prepared by electrofusion of natural silico-aluminate having a content of approximately 2.5% Al and a particle size of less than 1 μm. . B is derived from a boric acid and F from a Fluosilicate.

After 1 hour of maturation, a sample of the reaction mixture is taken and placed between two thin slides to be observed under the microscope x20 magnification. The observation shows that the mixture is translucent but that the entire surface is coated with spherical particles less than 1 micron, undigested. A composite is prepared with this reaction mixture as in Example 1.

After impregnation of the tissue, a sample of the reaction mixture is taken from the tissue to be again observed microscopically between two thin sections.

The observation is identical that before impregnation that is to say, the totality of the observed surface comprises spherical particles less than 1μn undigested. After post-baking, the sample is 2.3 mm thick and its mechanical properties are measurable.

Claims

1) Process for preparing a formable composite material, of the type consisting in impregnating a fibrous reinforcement with a reaction mixture in the form of an aqueous composition, characterized in that the water content of said aqueous composition is between 5% and 40% of the weight of the composition, said composition comprising: - compounds selected from the group consisting of silica oxides, alkali silicates and alkaline aluminosilicates, a part of which is in dissolved form, and the other part in the form of particles in suspension, and in a proportion such that the molar ratios of all these compounds, expressed in terms of oxides after dehydration, are between:

M ₂ CVSiO ₂ : 0.03 and 0.145 SiO ₂ / Al ₂ O ₃ : 6.50 and 165 M ₂ O / Al ₂ O ₃ : 0, 95 and 15

M representing an atom of Na, K, or Li or a mixture of two or all of them, and these compounds representing between 40 and 94.4% by weight of the composition; one or more forming agents or glass modifiers, at least one of which is selected from the group consisting of oxides, acids, salts or other forms of the following elements: Ge, B, P, As, Sb, Te, Mo, W, Bi, Ga, V, Cr, Mn, Zr, Ti, Cd, Ga, Ca, F, the total weight of these agents, expressed by weight of their dehydrated oxides, being between 0.5% and 50%, preferably between 0.5 and 35% and most preferably between 0.5 and 15% of the weight of the dehydrated composition; one or more rheological agents and / or modifiers of the surface characteristics of the liquids, such as surfactants or surfactants, in an amount of between 0.1% and 5% of the weight of the composition; one or more inorganic or organic compounds compatible with an alkaline silicate medium, selected from the group consisting of binders, gelling agents and accelerators or retarders of setting, sugars and sugar compounds, sorbitols, fatty acids , glycerols or glycols in an amount of between 0 and 20% of the weight of the dehydrated composition.

2) Process according to claim 1, characterized in that the aqueous composition comprises:

3) Process according to one of claims 1 or 2, characterized in that at least 30% of the SiO ₂ oxide of the aqueous composition are provided in the form of a powder containing mainly an aluminosilicate oxide in which the number of elements Si and Al is such that its empirical formula is between the following two formulas: (2SiO ₂ , AlO ₂ ) and (82.5SiO ₂ , AlO ₂ ) said alumino-silicate oxide from the condensation and cooling of vapors produced at temperatures above 1800 ⁰ C and preferably above 2000 ⁰ C during the electro-fusion of natural or synthetic compounds, sands, minerals or ores containing silica and alumina, or during the fusion-vaporization joint silica and alumina, under a plasma torch for example at temperatures above

2000 ° C.

4) Process according to any one of claims 1 to 3, characterized in that the main part of the aluminosilicate oxides of the aqueous composition comprise reactive Al sites allowing crosslinking geopolymeric type during the rise in temperature.

5) Method according to claim 4, characterized in that the Al reactive sites are constituted by Al coordination cations (IV) and / or (V).

6) Process according to any one of the preceding claims, characterized in that at least one of the forming compounds or glass modifiers is based on boron, fluorine or phosphorus, for a total weight, expressed in terms of their dehydrated oxides, between 0.5% and 15% relative to the weight of the dehydrated composition.

7) Process according to any one of the preceding claims, characterized in that the rheology agents or modifiers of the surface characteristics of the liquids are chosen from the group comprising anionic surfactants, cationic, not ionic, or a mixture of two or more thereof, such as quaternary ammonium salts, alkyl-aryl sulfonates, organoamine salts.

8) Process according to any one of the preceding claims, characterized in that at least half of the particles in suspension are:

of substantially spherical shape,

with a diameter of between 100 nm and 1 micron, consisting of an alumino-silicate compound with a quantity defined between the following two formulas: (24 SiO ₂ , AlO ₂ ) and (90 SiO ₂ , AlO ₂ ),

- includes not more than 5% by weight of compounds or oxides other than those of Si and Al.

9) Process according to any one of the preceding claims, characterized in that the impregnation of the fibrous reinforcement is carried out by dipping followed or not by a spin, or by removal of a quantity determined by spraying, spraying or licking or transfer, or by infiltration, in one or more operations.

10) Method according to claim 9, characterized in that the impregnation is carried out by exerting a depression on the fibrous reinforcement and possibly again under controlled temperature.

11) Method according to one of claims 9 or

10, characterized in that the water content of the aqueous composition is brought back after impregnation to a content by weight of between 5% and 15% of the weight of the composition, for example by evaporation carried out at a temperature of between 20 ⁰ C and 45 ° C, optionally under vacuum, preferably before the material is shaped for its thermosetting.

12) Process for the preparation of a formable composite material of BMC type for "BuIk Molding Compound" according to any one of Claims 9 to 11, characterized in that the fibrous reinforcement is cut into small pieces or short fibers whose dimension is preferably between 0.1 mm and 5 cm.

13) Process according to any one of claims 1 to 12, characterized in that the fiber reinforcement consists of fibers selected from the group consisting of carbon fiber, glass, basalt, metal, ceramic, carbide silicon.

14) Process according to any one of the preceding claims, characterized in that the formable composite material is wrapped with one or more films of organic polymer airtight, or sandwiched between two polymer films organic airtight, preferably less than 60 minutes after impregnation and in that it is stored at a temperature below 0 ⁰ C, and preferably between -5 ° C and -25 ° C.

15) Formable composite material capable of being prepared by a method according to any one of claims 1 to 14.

16) A formable composite material according to claim 15, characterized in that it comprises a fibrous reinforcement impregnated with a reaction mixture under the form of an aqueous composition of alumino-silicates whose water content is between 5% and 15% of the weight of the composition, said composition comprising: compounds selected from the group consisting of silica oxides, alkali silicates and the alkaline aluminosilicates, a part of which is in dissolved form, and the other part in the form of particles in suspension, and in a proportion such that the molar ratios of all these compounds, expressed in terms of oxides after dehydration are between:

M ₂ CVSiO ₂ : 0.03 and 0.145 SiO ₂ / Al ₂ O ₃ : 6.50 and 165 M ₂ CVAl ₂ O ₃ : 0, 95 and 15 M representing an atom of Na, K, or Li or a mixture of two of them or all three, and these compounds representing between 65% and 94.4% by weight of said composition; one or more forming agents or glass modifiers, at least one of which is selected from oxides, acids, salts or other compounds of the following elements: Ge, B, P, As, Sb, Te, Mo, W, Bi, Ga, V, Cr, Mn, Zr, Ti, Cd, Ga, Ca, F, the total weight of these agents, expressed by weight of their dehydrated oxides, being between 0.5% and 15% of the weight of the composition dehydrated;

one or more rheological agents and / or modifiers of the surface characteristics of the liquids, such as surfactants or surfactants agents, in an amount of between 0.1% and 5% of the composition; one or more inorganic or organic compounds compatible with an alkaline silicate medium chosen from the group comprising binders, gelling agents and accelerators or setting retarders, sugars and sugar compounds, sorbitols, fatty acids, glycerols or glycols in an amount of between 0 and 20% by weight of the dehydrated composition; further characterized in that the weight of the reaction mixture in the dehydrated state is between 75% and 30% of the weight of the formable composite material in the dehydrated state.

17) A formable composite material according to one of claims 15 or 16, characterized in that the fibrous reinforcement representing between 25% and 70% by weight of said dehydrated formable composite material.

18) formable composite material according to any one of claims 15 to 17, characterized in that the fibrous reinforcement consists of fibers selected from the group consisting of carbon fiber, glass, basalt, metal, ceramic, silicon carbide.

19) Formable composite material according to any one of claims 15 to 18, characterized in that the MASNMR spectrum of the reaction mixture for 29Si has the following three resonance zones -87 + -5ppm, -98 + -5ppm, -107+ -5ppm.

20) Formable composite material according to any one of claims 15 to 19, characterized in that the MASNMR spectrum of the reaction mixture for 27Al has one or more of the following resonance zones -55 + -5ppm, -65 + -5ppm, - 70 + -5ppm, indicating that the coordination of AI is AlO ₄ .

21) Formable composite material according to claim 20, characterized in that the Al sites reagents are constituted by Al coordination cations (IV) and / or (V).

22) Composable formable material according to any one of claims 16 to 21, characterized in that at least one of the forming compounds or glass modifiers is based on boron, fluorine or phosphorus, for a total weight, expressed in terms of their dehydrated oxides, between 0.5% and 15% relative to the weight of the dehydrated composition.

23) A method of manufacturing a formed composite material part, characterized in that it comprises shaping a formable composite material according to one of claims 15 to 22, and its curing by heating during and / or after forming, at a temperature between 40 ⁰ C and 350 ⁰ C, preferably between 60 ⁰ C and 180 ⁰ C, at a pressure between atmospheric pressure and 1500 bar under vacuum or not.

24) Method according to claim 23, characterized in that the hardening is carried out in an autoclave under a pressure of 5 to 35 bar under vacuum or not.

25) Method according to one of claims 23 or 24, characterized in that the shaping is performed by a molding technique selected from the group comprising compression in open or closed mold, or between cylinders continuously laminar draping by superposed folds in a mold, under vacuum or not, filament winding or strips, pultrusion, extrusion, injection, transfer-infiltration molding or resin injection.

26) Part formed of composite material capable of being manufactured by a method according to one of claims 23 to 25.

27) formed composite material part according to claim 26, characterized in that it consists mainly of a fibrous reinforcement and a matrix, the fibrous reinforcement representing by weight between 25 and 75% of the piece and the matrix representing by weight between 30% and 75% of the part in the dehydrated state, and in that the matrix after dehydration is constituted by: - for 80 to 99.4% of its weight, one or more alkaline silico-aluminate compounds such as that the molar ratios of all of its alkali silicoaluminate compounds expressed in terms of oxides after dehydration are between: M ₂ CVSiO ₂ : 0.03 and 0.145

SiO ₂ / Al ₂ O ₃ : 6.50 and 165 M ₂ CVAl ₂ O ₃ : 0, 95 and 15

M represents an atom of Na, K, or Li or a mixture of two or all of them; one or more forming agents or glass modifiers, at least one of which consists of an oxide of the following elements: Ge, B, P, As, Sb, Te, Mo, W, Bi, Ga, V, Cr, Mn, Zr, Ti, Cd, Ga, Ca, F, the total weight of these agents expressed by weight of their dehydrated oxides being between 0.5% and 15% of the weight of the matrix and enclosed in the alumino-silicate matrix ; one or more inorganic or organic compounds enclosed in said matrix and coming from the residues, after polymerization of the matrix, of the agents of rheology and surface modifiers and various inorganic or organic compounds incorporated in the reaction mixture for a maximum content between 0.1 and -20% of the weight of said dehydrated reaction mixture; further characterized in that said matrix is in the form of a nanocomposite structure comprising at least two phases: a first nodular phase composed of siliceous particles, of non-laminated structure, of dimensions of between 50 nm and 1 micron, preferably between 100 nm and 1 micron, these particles representing between 30% and 95% by weight of the matrix,

28) composite formed part according to claim 27, characterized in that at least half of the particles of the nodular phase are spherical.

29) formed composite material part according to any one of claims 27 or 28, characterized in that the matrix has a spectrum 29Si MASNMR having the following three resonance zones: -87 + -5ppm, -98 + - 5ppm, following -107 + -5ppm.

30) formed composite material part according to any one of claims 27 to 29, characterized in that the MASNMR spectrum of the matrix for 27Al has one or more of the following resonance zones: -55 + -5ppm, -65 + -5ppm, -70 + -5ppm, the latter indicating that the coordination of the Ai is A104.

31) Process for obtaining a workpiece formed of composite material with fiber reinforcement and predominantly glass matrix, characterized in that it consists in heating a workpiece according to one of claims 26 to 30 at a temperature at least equal to the vitrification temperature of the matrix for at least 15 minutes.

32) Method according to claim 31, characterized in that the part is heated to a temperature between 600 ⁰ C and 1500 ⁰ C.

33) Method according to one of claims 31 or 32, characterized in that said heating is carried out in a non-oxidizing controlled atmosphere.

34) Method according to one of claims 31 to

33, characterized in that the formed piece is not contained, maintained or supported by a mold or a support constituting a negative of the piece formed on more than 20% of its non-planar surface.

35) Part formed of composite material with fibrous reinforcement and predominantly glass matrix, characterized in that it is obtained by a method according to one of claims 31 to 34.

36) Piece formed according to claim 35, characterized in that MASNMR spectrum of the matrix for 27Al has one or more of the zones of resonance: -55 + -5ppm, -65 + -5ppm, -70 + -5ppm, the latter indicating that the coordination of Ai is A104.

37) reaction mixture, capable of being implemented in a process according to any one of claims 1 to 14, characterized in that it is in the form of an aqueous composition whose water content is between 5% and 40% by weight of the composition, and in that it comprises: - compounds selected from the group consisting of silica oxides, alkali silicates and alkaline aluminosilicates, some of which is in dissolved form, and the other part in the form of particles in suspension, and in a proportion such that the molar ratios of all these compounds, expressed in terms of oxides after dehydration, are between: M ₂ CVSiO ₂ : 0.03 and 0.145 SiO ₂ / Al ₂ O ₃ : 6.50 and 165 M ₂ CVAl ₂ O ₃ : 0, 95 and 15 M representing an atom of Na, K, or Li or a mixture of two or all of them, and these compounds representing between 40 and 94.4% by weight of the composition; one or more glass forming or modifying compounds, at least one of which is selected from the group consisting of oxides, acids, salts or other forms of the following elements: Ge, B, P, As, Sb, Te, Mo , W, Bi, Ga, V, Cr, Mn, Zr, Ti, Cd, Ga, Ca, F, the total weight of these agents, expressed by weight of their dehydrated oxides, being between 0.5% and 15% by weight the dehydrated composition;

one or more rheology agents and / or modifiers of the surface characteristics of liquids such as surfactants or surfactants, in a amount between 0.1% and 5% of the weight of the composition; one or more inorganic or organic compounds compatible with an alkaline silicate medium, selected from the group consisting of binders, gelling agents and accelerators or retarders of setting, sugars and sugar compounds, sorbitols, fatty acids , glycerols or glycols, in an amount of between 0 and 20% of the weight of the dehydrated composition.

38) Reaction mixture according to claim

37, characterized in that the aqueous composition comprises:

39) reaction mixture according to one of claims 37 or 38, characterized in that at least 30% of the SiO ₂ oxide of the aqueous composition are provided in the form of a powder containing mainly an aluminosilicate oxide in where the number of elements Si and Al is such that its formula is between the following two formulas:

(2SiO ₂ , AlO ₂ ) and (82.5SiO ₂ , Al ₂ O ₂ ) said alumino-silicate oxide from the condensation and cooling of the vapors produced in temperatures higher than 1800 ⁰ C and preferably greater than 2000 ⁰ C during the electro-fusion of natural or synthetic compounds, sands, minerals or ores containing silica and alumina, or during the joint fusion-vaporization silica and alumina, under a plasma torch for example at temperatures above 2000 ° C.

40) A reaction mixture according to any one of claims 37 to 39, characterized in that the main part of the aluminosilicate oxides of the aqueous composition comprises reactive Al sites allowing a geopolymeric type of crosslinking during the rise in temperature.

41) Reaction mixture according to claim 40, characterized in that the Al reactive sites are constituted by coordination cations (IV) and / or (V).

42) Reaction mixture according to any one of claims 37 to 41, characterized in that at least one of the glass forming or modifying compounds is based on boron, fluorine or phosphorus, for a total weight, expressed as term of their dehydrated oxides, between 0.5% and 15% relative to the weight of the dehydrated composition.

43) Reaction mixture according to any one of claims 37 to 42, characterized in that the rheology agents or modifiers of the surface characteristics of the liquids are chosen from the group consisting of anionic, cationic and nonionic surfactants, or a mixture of two or more of these, as quaternary ammonium salts, alkyl-aryl sulfonates, organoamine salts.

44) Reaction mixture according to any one of claims 37 to 43, characterized in that at least half of the particles in suspension are:

of substantially spherical shape,

with a diameter of between 100 nm and 1 micron, consisting of an alumino-silicate compound with a quantity defined between the two following formulas:

(24 SiO ₂ , AlO ₂ ) and (90 SiO ₂ , AlO ₂ ),