Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02K—JET-PROPULSION PLANTS
  • F02K9/00—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof
  • F02K9/08—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof using solid propellants
  • F02K9/32—Constructional parts; Details not otherwise provided for
  • F02K9/34—Casings; Combustion chambers; Liners thereof
  • F02K9/346—Liners, e.g. inhibitors
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C53/00—Shaping by bending, folding, twisting, straightening or flattening; Apparatus therefor
  • B29C53/56—Winding and joining, e.g. winding spirally
  • B29C53/58—Winding and joining, e.g. winding spirally helically
  • B29C53/60—Winding and joining, e.g. winding spirally helically using internal forming surfaces, e.g. mandrels
  • B29C53/602—Winding and joining, e.g. winding spirally helically using internal forming surfaces, e.g. mandrels for tubular articles having closed or nearly closed ends, e.g. vessels, tanks, containers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02K—JET-PROPULSION PLANTS
  • F02K9/00—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof
  • F02K9/08—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof using solid propellants
  • F02K9/32—Constructional parts; Details not otherwise provided for
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2031/00—Other particular articles
  • B29L2031/712—Containers; Packaging elements or accessories, Packages
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2300/00—Materials; Properties thereof
  • F05D2300/60—Properties or characteristics given to material by treatment or manufacturing
  • F05D2300/611—Coating

Definitions

• the present invention relates to a method for producing an internal and / or external thermal protective coating of a propellant structure, in particular of a solid propellant propellant. It also relates to a method for producing a propellant structure and the propellant structure thus produced.
• the structure of a solid propellant propellant essentially consists of a resistant envelope, for example of composite material, usually provided with an internal thermal protection coating which must fulfill three essential functions: thermally protecting the resistant composite envelope from aggression of the hot gases resulting from the combustion of the propellant, attenuating the mechanical stresses generated by the deformation under pressure of the resistant casing during the combustion phase of the propellant, and ensuring the sealing of the resistant casing against leaks of gas.
• thermal protection coatings inside the resistant envelope of the propellant structure There are different methods for applying the thermal protection coatings inside the resistant envelope of the propellant structure.
• One of them consists, starting from a rubber produced by conventional means of the rubber industry (cylinder mixers, internal mixers, ...) in the state of unvulcanized semi-product and viscous consistency, to transform this rubber into elastomer sheets intended to be cut and then draped over a mandrel before vulcanization in an autoclave.
• the various thermal protection elements thus produced are then disassembled from their respective mandrels to be assembled on another mandrel (generally metallic and removable) used for the filament winding of the composite envelope on the thermal protection thus formed. This process leads to long production cycles which give this technology a particularly high cost of implementation.
• flexible thermal protection coatings use rubbers (combination of specific ingredients) specially formulated to perform the three main functions mentioned above, namely resistance to ablation against thermal aggression and propellant combustion gas mechanics, thermal insulation of the structure and reduction of mechanical stresses.
• rubbers combination of specific ingredients
• thermal insulation of the structure namely resistance to ablation against thermal aggression and propellant combustion gas mechanics, thermal insulation of the structure and reduction of mechanical stresses.
• optimizing the performance of a solid propellant propellant involves reducing the weight of inert masses (which includes internal thermal protection)
• the ideal material for achieving this protection internal thermal must have a very good resistance to ablation vis-à-vis the thermal and mechanical aggression of combustion gases associated with low density and low thermal conductivity.
• the present invention therefore aims to overcome such drawbacks by proposing a method for producing a thermal protective coating of a propellant structure which considerably reduces the implementation operations in order to simplify the production cycles and the necessary tools.
• This method according to the invention makes it possible to obtain a coating which optimally fulfills the functions associated with a thermal protection coating of a propellant structure.
• the invention also aims to propose a method making it possible to carry out both internal thermal protection and external thermal protection of a propellant structure.
• the invention also relates to the production of a propellant structure provided with an internal and / or external thermal protection coating as obtained by the method, as well as a propellant structure thus produced.
• a method for producing a thermal protective coating of a propellant structure characterized in that it consists in continuously metering and mixing at least one polyurethane with a mixture of polymerization in which specific fillers have been previously dispersed, to coat a cylindrical support surface in rotation by the continuous casting of a ribbon of contiguous turns of mixture thus obtained, and to pre-polymerize at coating pressure the coating thus obtained of so that the polyurethane becomes sufficiently polymerized to be mechanically stressed.
• the various stages of the method according to the invention can be carried out on a single multifunctional work station and succeed one another continuously and without interruption as regards the stages of mixing and casting, and can be almost entirely automated.
• the mixture intended to coat the support surface consists in particular of a polyurethane of the prepolymer type.
• this is isocyanate-terminated and advantageously results from the reaction of a polyether with diphenyl-methane-diisocyanate.
• the polymerization agents are advantageously of the amine type and / or of the polyol type.
• powdery and / or fibrous fillers will preferably be chosen.
• the pulverulent fillers can be of the silica type and / or an antimony trioxide and / or chlorinated compounds and / or glass microballoons and / or silica microballoons and / or acrylonitrile microballoons.
• the fibrous fillers can be discontinuous of the aramid type and / or of the cellulosic type. Such a mixture is remarkable in that it occurs, despite the high charge rate necessary to ensure the thermal protection function, in a substantially liquid state at its outlet from a casting head, gels quickly so as not to flow outside the surface of. support when it is deposited thereon and passes, after its pre-polymerization at ambient pressure, to a partially but sufficiently polymerized so that the coating can be mechanically stressed.
• variable thicknesses By varying continuously and automatically different process parameters (such as the rate of the different polymerization agents, the flow rate, the speed of rotation of the support surface, the speed of movement of the casting head), it is possible to deposit variable thicknesses on both cylindrical and spherical surfaces. In addition, in the case of the production of a very thick thermal protective coating, it is also possible to carry out the removal in several successive passes while keeping the continuous and automated nature of the process.
• process parameters such as the rate of the different polymerization agents, the flow rate, the speed of rotation of the support surface, the speed of movement of the casting head
• the dosages of polyurethane and polymerization agents can vary so as to obtain a first and at least a second mixture.
• a coating of the support surface by superimposing a casting of a ribbon of a first mixture, for example having good resistance to l ablation with respect to the combustion gases, and a casting of a ribbon of a second mixture, for example having a low density and a low thermal conductivity.
• the method may further include a step of machining the pre-polymerized coating to a desired exterior profile.
• a final step can also be provided, consisting in polymerizing the pre-polymerized coating by baking.
• the method for producing a propellant structure according to the invention consists in providing a resistant envelope with an internal coating and / or an external thermal protection coating produced according to the method described above.
• Such a method can be applied to the production of a propellant structure in which the support surface used for the production of an internal thermal protection coating is an external surface of a rotating mandrel.
• the resistant casing of the propellant is then deposited and adhered to an external surface of the coating thus produced.
• the resistant casing of the propellant is obtained by filament winding of a composite material, this winding of composite material is preferably polymerized simultaneously with the polymerization of the coating by firing.
• the propellant structure thus produced is then disassembled from the mandrel.
• This method can also be applied to the production of a propellant structure in which the support surface used for producing an internal thermal protection coating is an internal surface of the resistant casing of the propellant.
• the resistant casing of the propellant which is preferably obtained by filament winding of a fibrous material prepreg on an external surface of a mandrel is produced prior to coating.
• the internal thermal protection coating is then produced on an internal surface of the latter and it is preferably polymerized by baking simultaneously with the polymerization of the filament winding.
• the method can be applied to the production of a propellant structure having a resistant envelope provided with an external thermal protection coating, alone or in combination with an internal thermal protection coating.
• the external thermal protection coating is deposited and adhered to an external surface of the resistant envelope always according to the same process.
• the method for producing a thermal protective coating of a propellant structure essentially consists in: a) continuously dosing and mixing at least one polyurethane with a mixture of polymerization agents in which have been previously dispersed specific charges; b) coating a cylindrical support surface in rotation by the continuous casting of a ribbon of contiguous turns of the mixture thus obtained; and c) pre-polymerizing the coating thus obtained at ambient pressure so that the polyurethane becomes sufficiently polymerized to be mechanically stressed.
• steps for implementing the method are carried out using devices for producing cylindrical coatings.
• Such devices differ from the devices for producing internal thermal protection coatings known from the prior art in that the means for depositing the coating employ simple casting means and not extrusion means. As such, these devices are not described in detail in the present application.
• these devices fall into two categories: devices which form a coating on the external surface of a rotating mandrel, the resistant casing of the propellant being subsequently deposited and adhered to the coating thus formed; and devices which form a coating directly on the internal surface or the external surface of the resistant casing of the propellant.
• the device for producing a thermal protective coating comprises a mandrel 2, for example metallic, mounted on a rotary shaft 4 held by a driving headstock 6 and a movable frame 8.
• the mandrel 2 can rotate continuously in the direction of the arrow F.
• a longitudinal bench 10, parallel to the mandrel 2 serves as a support for a carriage 12 capable of moving longitudinally on the bench.
• a casting head 14 is carried by the carriage 12 via an axis 16 perpendicular to the axis of the mandrel and the bench.
• Step a) of the process according to the invention consists in continuously preparing the mixture containing polyurethane intended to form the thermal protection coating.
• the polyurethane can be a prepolymer of the isocyanate-terminated type.
• this polyurethane prepolymer results from the reaction of a polyether with diphenylmethane diisocyanate.
• the polyurethane is dosed and mixed in the casting head 14 with polymerization agents in which specific charges have been previously dispersed.
• the polyurethane, the different polymerization agent (s) (catalysts) and the different filler (s) are each stored in a container of their own. Using the conduits and metering pumps connected to these containers, it is then possible to route the desired components in quantity and at the desired rate to the casting head. Thus, the dosage of the components can vary continuously without interrupting the pouring of the mixture obtained.
• the polymerization agent (s) are chosen for their rheological and polymerization characteristics so that the polyurethane passes from a substantially liquid state on leaving the casting head to a state sufficiently viscous to adhere to the external surface of the mandrel 2 without flow out of it.
• the “setting time” of the mixture thus obtained must therefore be very short.
• preferably powdery or fibrous fillers will be chosen.
• the pulverulent fillers can be of the silica type and either an antimony trioxide and / or chlorinated compounds and / or glass microballoons and / or silica microballoons and / or acrylonitrile microballoons.
• the fibrous fillers can be discontinuous of the aramid type and / or of the cellulosic type.
• Step b) of the method consists in coating the external surface of the mandrel 2 by continuously casting in contiguous turns a ribbon 18 of mixture thus obtained.
• the mixture flows at the outlet of the casting head 14 onto the external surface of the mandrel and thus forms a continuous ribbon 18.
• the polyurethane "setting time" being made very short by the addition of the polymerization agents, the mixing ribbon 18 gels to become viscous and not to flow during the continuous rotation of the mandrel.
• step c) of the process the coating thus obtained is pre-polymerized.
• This pre-polymerization step is carried out at ambient pressure, and advantageously at ambient temperature. It therefore does not require an autoclave, which considerably reduces the costs of implementing the process.
• This pre-polymerization phase allows the coating to pass from a substantially viscous state to a sufficiently polymerized state to be mechanically stressed, for example during subsequent machining or over-winding steps.
• This change in state of the coating can be understood by the fact that the liquid polyurethane is mixed with one or more polymerization catalysts.
• a final polymerization step by baking the coating thus pre-polymerized can be provided.
• This coating is also baked under ambient pressure in an oven. It gives the coating its optimal mechanical and thermal properties. Cooking can be ensured before depositing and adhering the resistant casing of the propellant (in particular when it is metallic) or after depositing and adhering it.
• the resistant casing of the propellant is produced by filament winding of a prepreg fibrous material (for example winding of a carbon, glass or polyaramide wire impregnated with a non-polymerized thermosetting resin) on the external surface of the coating
• a prepreg fibrous material for example winding of a carbon, glass or polyaramide wire impregnated with a non-polymerized thermosetting resin
• the simultaneous polymerization step can also make it possible to obtain the bond between the coating and the composite structure by means of a bonding agent previously deposited on the external surface of the coating.
• the method according to the invention as described above with reference to the figure is implemented by a device which forms an internal coating by casting a tape on the external surface of a rotating mandrel, the resistant casing of the propellant being subsequently deposited and adhered to the coating thus formed.
• the method according to the invention also applies to a device which forms the internal coating by casting a tape directly on the internal surface of the resistant casing of the propellant.
• the hollow casing of the propellant structure metallic or advantageously made of polymerized composite material, is previously produced with the thermal protective coating and then rotated between a driving doll and a movable frame.
• the coating device also comprises a casting head which can move inside the casing of the propellant, along its longitudinal axis.
• the process for producing the thermal protective coating is identical to that described above.
• the internal surface of the casing of the propellant Prior to the step of continuously casting a ribbon in contiguous turns of the mixture, the internal surface of the casing of the propellant is degreased and treated with the aid of a bonding agent.
• the coating obtained is pre-polymerized at room temperature and pressure, then optionally machined.
• the coating can also be subjected to an oven polymerization.
• the method according to the invention also generates a gain in terms of reduction in production costs.
• the method according to the invention can be applied to the production of an external thermal protection coating for propellant structure. Such an external coating is deposited and adhered to an external surface of the resistant envelope of the propellant structure.
• This external thermal protection coating can be used either alone or in combination with an internal thermal protection coating.
• a resistant envelope made of composite material provided with both an internal coating and an external coating it is advantageous to carry out the polymerization of the two coatings simultaneously with the polymerization phase of the filament winding of the envelope resistant.
• the adhesion between the thermal protection coating (s) and the resistant envelope of the propellant structure is obtained either using a known type of adhesion agent or using an adhesive polyurethane film. In the latter case, such a film is obtained by metering the polyurethane specially formulated as an adhesive in the casting head 14 and its deposition is carried out by casting a continuous ribbon in contiguous turns, according to the method of the invention.
• This solution makes it possible to avoid the use of certain known adhesion agents such as isocyanates deposited using a gun which pose safety and environmental problems since they require the use of solvents.
• Example 1 (polyurethane coating loaded with silica:
• the mixture obtained was deposited by continuously casting a ribbon of contiguous turns on the external surface of a rotating cylindrical mandrel (mandrel with a diameter of 0.3 m and a length of 1 m).
• the flow rate of the mixture, the speed of rotation of the mandrel and the speed of movement of the casting head were adjusted so as to deposit in two successive 5 mm passes a coating of uniform thickness of 10 mm.
• the coating I thus produced has been disassembled from its mandrel in order to undergo certain resistance tests specific to internal thermal protections, namely: mechanical resistance in traction, thermal resistance (thermal conductivity and specific heat) and tests of shooting characteristics (measurement of the rate of erosion under thermal aggression and propellant combustion mechanics).
• resistance tests specific to internal thermal protections namely: mechanical resistance in traction, thermal resistance (thermal conductivity and specific heat) and tests of shooting characteristics (measurement of the rate of erosion under thermal aggression and propellant combustion mechanics).
• Example 2 low density polyurethane coating loaded with glass microballoons:
• the densities measured on samples taken at different points of the coating III are approximately 0.68 which is close to the theoretical density (0.66) calculated on the basis of the rate and the density of the various constituents. This shows that the glass microballoons are little affected during all the phases of mixing of the various constituents. Furthermore, no defect in bubble-like material or poor adhesion between the two layers was noted.
• Example 3 (coating with superposition of layers corresponding to different formulations:
• the various constituents of the formulation defined in Example 1 were dosed and then mixed in the casting head of the casting device.
• the mixture obtained was deposited by continuously casting a ribbon of contiguous turns on the external surface of a rotating cylindrical mandrel (mandrel with a diameter of 0.3 m and a length of 1 m).
• the flow rate of the mixture, the speed of rotation of the mandrel and the speed of movement of the casting head were adjusted so as to deposit in a pass a layer of thickness 5 mm.
• the process was repeated with the constituents of the formulation defined in Example 2.
• the casting of this mixture was carried out in two successive passes of 5 mm each in order to obtain a 10 mm thick layer.
• Example 4 (coating of polyurethane loaded with silica coated with a resistant epoxy carbon shell:
• Example 1 The various constituents of the formulation defined in Example 1 were dosed and then mixed in the casting head of the casting device.
• the mixture obtained was deposited by continuously casting a ribbon of contiguous turns on the external surface of a rotating cylindrical mandrel (mandrel with a diameter of 0.3 m and a length of 1 m).
• the flow rate of the mixture, the speed of rotation of the mandrel and the speed of movement of the casting head were adjusted so as to deposit in a pass a layer of thickness 5 mm.
• a carbon fiber wet impregnated with an epoxy resin of class 120 ° C is wound circumferentially on the coating to a thickness of about 4 mm.
• the mandrel thus equipped is placed in a ventilated oven for a polymerization cycle consisting of a temperature rise of 1 ° per minute to 140 ° C, followed by a two-hour plateau at 140 ° C and a temperature drop of 1 ° per minute.
• samples are taken by machining 25 mm wide, about 9 mm thick and about 300 mm curvilinear length.
• the adhesion between the thermal protective coating and the resistant envelope was tested using a specific tensile tool and by a peel test with an angle of approximately 90 ° between the envelope and the covering tongue through which the traction is exerted.
• the tensile force to be exerted to disassemble the coating of the envelope is greater than 25 daN, which corresponds to good adhesion between these two elements.
• the present invention has many advantages, and in particular: - it uses a series of automatic operations which follow one another continuously. Indeed, the coating devices used allow ensuring continuous dosing and mixing of the ingredients and pouring of the mixture obtained, the pre-polymerization of the coating obtained does not require drying, which allows the same support to be used for the possible polymerization phase ; - It leads to short production cycles, reduces the implementation time and the necessary tools and therefore reduces the costs of producing the coating.
• the number of workstations is in particular reduced since from a single station, it is possible to implement the steps of coating, machining, pre-polymerization and possible winding. It is also not necessary to disassemble the coating from its support in order to carry out the polymerization step, which simplifies this step of the process.
• the resistant casing of the propellant is produced by filament winding of a composite material, it is also possible to directly use the mandrel used later in this winding step. Thus, it is possible to make large propellant structures; - It makes it possible to obtain a thermal protection coating having improved characteristics. In fact, it is possible to produce coatings having several superimposed layers of different composition (as described in Example 3). For example, it will be possible to deposit a first layer of adequate thickness and formulated specifically to exhibit good resistance to ablation with respect to the thermal and mechanical aggression generated by the combustion of gases and a second layer, superimposed on the first, specially formulated to have low density and low thermal conductivity.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• General Engineering & Computer Science (AREA)
• Moulding By Coating Moulds (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Paints Or Removers (AREA)

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• 2002
  • 2002-12-31 FR FR0216905A patent/FR2849404B1/fr not_active Expired - Fee Related
• 2003
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  • 2003-12-17 RU RU2005121496/06A patent/RU2330981C2/ru not_active IP Right Cessation
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  • 2003-12-17 UA UAA200507487A patent/UA80739C2/uk unknown
  • 2003-12-17 JP JP2004567017A patent/JP2006512202A/ja active Pending
  • 2003-12-17 WO PCT/FR2003/003763 patent/WO2004065106A1/fr active Application Filing
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