PRE-IMPREGNATED ROVINGS FOR COMPOSITE MATERIAL

Abstract

A method for impregnating an oxide fibre roving with a matrix of alumina and silica includes a introducing an oxide fibre roving into an impregnation bath, wherein the impregnation bath is prepared by sol-gel process and includes a silica precursor in the form of a hybrid polymeric sol, an alumina precursor in the form of a colloidal sol and ceramic particles.

Claims

1. A method for impregnating an oxide fibre roving with a matrix of alumina and silica comprising introducing an oxide fibre roving into an impregnation bath, wherein the impregnation bath is prepared by sol-gel process and comprises a silica precursor in the form of a hybrid polymeric sol, an alumina precursor in the form of a colloidal sol and ceramic particles.

2. The impregnation method according to claim 1, wherein the rovings are aluminum oxide fibres.

3. The impregnation method according to claim 1, wherein the silica precursor is chosen from (3-glycidyloxypropyl)triethoxysilane-(GPTES), (3-glycidyloxypropyl)trimethoxysilane (GPTMS), (3-glycidyloxypropyl)diethoxysilane (GPDES) or ureidopropyltrimethoxysilane (UPS).

4. The impregnation method according to claim 1, wherein the alumina precursor is colloidal boehmite or aluminium isopropoxide (AIP).

5. The impregnation method according to claim 1, wherein the ceramic particles are alumina powder.

6. The impregnation method according to claim 1, wherein the impregnation bath further comprises an organic polymer selected from water-soluble thermoplastics or tackifying resins.

7. A method for manufacturing a part made of composite material having an alumina and silica matrix, comprising automatically placing pre-impregnated oxide fibres by an impregnation method according to claim 1, and sintering the pre-impregnated oxide fibres.

8. A roll comprising at least one oxide fibre roving pre impregnated by an impregnation method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] FIG. 1 is a schematic representation of a method of impregnating a roving according to an embodiment of the invention.

[0049] FIG. 2 is a schematic representation of a method for preparing a fibre preform according to an embodiment of the invention.

DESCRIPTION OF THE EMBODIMENTS

[0050] The invention is now described by means of particular embodiments which should not be interpreted in a limiting manner.

[0051] FIG. 1 shows a method for preparing a roll of pre-impregnated oxide fibre rovings.

[0052] As described above, it is the components of the impregnation bath 15 that will enable the pre-impregnated rovings 11 to be subsequently used in a method for preparing a fibre preform with an automatic fibre placement method.

[0053] In the method described in FIG. 1, the impregnation step 4 may be preceded by one or more steps making it possible to improve the impregnation of the roving 11 by the matrix of the impregnation bath 15.

[0054] Such optional and independent steps are illustrated schematically in FIG. 1. It should not be understood from FIG. 1 that all these steps must be present simultaneously, and they may each be present or not according to the impregnation needs.

[0055] For example, the method may comprise an unrolling step 1 then sizing removal step 2 before impregnation 4. During these steps, a previously sized oxide fibre roving 11 in the form of a roll 12 is unrolled and then the sizing is removed by means of a heat treatment, for example between 450 and 700° C., applied by means of a heating member 13.

[0056] Impregnation may also be preceded by a step 3 of spreading the fibres, during which a comb 14 spreads the oxide fibre rovings 11.

[0057] Such a spreading step 3 makes it possible to increase the contact surface between the impregnation bath 15 and the fibres of the rovings and thus allows better impregnation of the rovings 11 during contact with the impregnation bath 15.

[0058] The method can then comprise the step of impregnation by dipping 4 in the impregnation bath 15, having the characteristics described above.

[0059] The method may also comprise a drying step 5, carried out by means of a second heating member 17, then a rolling step 6, making it possible to roll the oxide fibre roving 11, which is now impregnated, around a roll 18.

[0060] As described above, it is the components of the impregnation bath 15 that make it possible to ensure that the pre-impregnated rovings obtained are compatible with the deposition conditions of an automatic fibre placement method.

[0061] FIG. 2 schematically illustrates a method for automatically placing the pre-impregnated fibres obtained according to one of the embodiments described above, allowing the manufacture of a part made of ceramic matrix composite material.

[0062] In such a manufacturing method, the pre-impregnated rovings 31 are deposited on the surface of a mould 32. The deposition tool 33 is equipped with a heating head 34 enabling the tackiness of the rovings to be activated, and the rovings 31 to adhere to the mould 32 or, where appropriate, to the rovings already placed. The arrow 40 represents the direction of movement of the tool 33.

[0063] The tooling is also provided with a compacting wheel 35 which makes it possible to apply pressure to the deposited rovings 31 and thus to enable the preform to be manufactured.

[0064] The preform thus obtained by the successive deposition of the rovings 31 is then sintered during a step (not shown) to arrive at a part made of ceramic matrix composite material.

[0065] This method combines the advantage of a pre-impregnated preform and the advantage of a fibre deposition method using an automatic fibre placement method. In fact, this method does not require a step of injection of the matrix, the latter being already contained in the deposited rovings. It also does not require the fibres to be placed by hand, since they are compatible with automatic placement.

Example

[0066] The invention is now illustrated by means of an example of embodiment which should not be interpreted restrictively.

[0067] An impregnation bath is prepared by introducing colloidal boehmite into a solution containing water and polyvinylpyrrolidone with a molecular weight of 3500 g/mol, to reach a concentration between 275 g/L and 1100 g/L. The colloidal boehmite is introduced in a concentration of 80 g/L, and has a particle size of around 0.2 μm. The solution is then peptised by introducing acetic acid in a concentration of mol/L.

[0068] The solution thus prepared is then stirred until the boehmite aggregates have completely disappeared. A dispersant is then added, for example ammonium polymethacrylate

[0069] Alumina powder is then added, and the solution is stirred for a few hours.

[0070] After this stirring, a hybrid silica precursor, (3-glycidyloxypropyl)triethoxysilane, is introduced dropwise into the solution and the mixture is then stirred for 12 hours.

[0071] The weight ratio between the silica precursor and the alumina precursor is 75/25.

[0072] The impregnation bath is then ready, and it is possible to impregnate oxide rovings, for example by means of a method illustrated schematically in FIG. 1, described above.

[0073] Such rovings can then be used during a manufacturing method with automatic placement of the fibres, for example the one illustrated in FIG. 2, described above.