Method for impregnation of a fibrous preform and device for implementation of the said method

Abstract

A method of impregnating a fiber preform with an impregnation composition, includes applying a liquid on a structure, the structure including a chamber in which a fiber preform for impregnating is present, the chamber being defined between a rigid support on which the fiber preform is placed and a wall, the wall having a face situated facing the fiber preform; and an impregnation composition for impregnating the fiber preform, the impregnation composition being present in the chamber; the liquid being applied against the wall on its side opposite from the chamber, the wall being configured so that its face situated facing the fiber preform conserves its shape during the application of the liquid, the applied liquid enabling sufficient pressure to be created to move the wall towards the rigid support and impregnate the fiber preform with the impregnation composition.

Claims

1. A method of impregnating a fiber preform with an impregnation composition, the method comprising: a) applying a liquid on a structure, the structure comprising: a chamber in which a fiber preform for impregnating is present, the chamber being defined between a rigid support on which the fiber preform is placed and a wall, the wall having a face situated facing the fiber preform; and an impregnation composition, for impregnating the fiber preform, the impregnation composition being present in the chamber; the liquid being applied against the wall on its side opposite from the chamber, the wall being sufficient rigid so that its face situated facing the fiber preform conserves its shape and avoid being deformed during the application of the liquid, the applied liquid enabling sufficient pressure to be created to move the wall towards the rigid support and impregnate the fiber preform with the impregnation composition.

2. A method according to claim 1, wherein, prior to step a), the method further comprises injecting the impregnation composition into the chamber.

3. A method according to claim 2, wherein the impregnation composition is injected into the chamber after placing the fiber preform on the support, and wherein the impregnation composition is injected between the fiber preform and the wall.

4. A method according to claim 1, wherein, prior to applying the liquid, the impregnation composition is superposed on the fiber preform over at least half of a length of the fiber preform.

5. A method according to claim 1, wherein the structure also includes an impermeable membrane covering the wall, and wherein the wall is situated between the chamber and the impermeable membrane, and wherein the liquid is applied against the impermeable membrane on its side opposite from the chamber.

6. A method of fabricating a part comprising a fiber preform densified by a matrix, the method comprising: b) densifying a fiber preform that has been impregnated by an impregnation composition that is a densification matrix precursor in order to obtain a part comprising a fiber preform densified by a matrix, the impregnated preform being obtained by performing a method according to claim 1.

7. A method according to claim 6, wherein the densification is performed while maintaining the pressure exerted by the wall on the impregnated preform as a result of the application of the liquid.

8. A method according to claim 6, wherein the part constitutes a turbine engine blade.

9. A device for performing a method according to claim 1, the device comprising: a structure including a chamber defined between a rigid support and a wall, the wall having a face situated facing the rigid support, the chamber defining an internal volume in which a fiber preform impregnated by a matrix precursor impregnation composition is to be present, the chamber being configured to be subjected to heat treatment for the purpose of densifying the fiber preform; and a liquid injection device configured to apply a liquid against the wall on its side opposite from the chamber; the device being configured so that the application of the liquid against the wall on its side opposite from the chamber does not change the shape of the face of the wall situated facing the rigid support and generates sufficient pressure on the wall to move it towards the support and reduce the internal volume of the chamber.

10. A device according to claim 9, wherein the structure further includes an impermeable membrane covering the wall, and wherein the wall is situated between the chamber and the impermeable membrane, and wherein the liquid injection device is configured to apply the liquid against the impermeable membrane on its side opposite from the chamber.

11. A device according to claim 9, further comprising a heater member configured to perform heat treatment on the impregnation composition enabling the fiber preform to be densified.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other characteristics and advantages of the invention appear from the following description of particular implementations of the invention given as non-limiting examples and with reference to the accompanying drawings, in which:

(2) FIG. 1 is a fragmentary and diagrammatic view of the fiber preform that is to be impregnated by the method of the invention, shown placed in a device of the invention;

(3) FIG. 2 is a fragmentary and diagrammatic view of the FIG. 1 assembly after injecting the impregnation composition;

(4) FIG. 3 is a fragmentary and diagrammatic view of the FIG. 2 assembly after applying the fluid;

(5) FIG. 4 is a fragmentary and diagrammatic view of the assembly obtained after impregnating the fiber preform with the impregnation composition; and

(6) FIG. 5 is a fragmentary and diagrammatic view of the part obtained after curing the impregnation composition.

DETAILED DESCRIPTION OF IMPLEMENTATIONS

(7) With reference to FIGS. 1 to 4, there follows a description of various steps of an impregnation method of the invention.

(8) FIG. 1 shows a device 1 of the invention comprising a rigid support 3 on which the fiber preform 10 is placed. A chamber 2 in which the fiber preform 10 is present is defined by the rigid support 3 and the wall 4. Furthermore, the chamber 2 is defined by side walls 9a and 9b of the support 3. As shown, the chamber 2 has an empty volume 7 situated between the fiber preform 10 and the wall 4. The wall 4 presents a face 4a situated facing the fiber preform 10.

(9) The wall 4 may be moved relative to the support 3 when sufficient pressure is exerted thereon. In the example shown, the wall 4 has two ends 8a and 8b co-operating with the side walls 9a and 9b. The ends 8a and 8b in cooperation with the side walls 9a and 9b serve to guide the wall 4 relative to the support 3. By way of example, these ends 8a and 8b may constitute upwardly extending edges, as shown. It would not go beyond the ambit of the present invention for the ends 8a and 8b to be of some other shape suitable for co-operating with the walls 9a and 9b in order to enable the wall 4 to move relative to the support 3.

(10) In the example shown, an impermeable membrane 5 covers the wall 4, the wall 4 being situated between the chamber 2 and the impregnable membrane 5. By way of example, the impregnable membrane 5 may be flush with the wall 4. As shown, the impregnable membrane 5 may cover the wall 4 in full. It would not go beyond the ambit of the present invention for the impregnable membrane 5 to be omitted.

(11) Opposite from the chamber 2, the device 1 also includes a cavity 6 overlying the wall 4. The cavity 6 may be defined by a lid 7. As described in detail below, the cavity 6 is for filling with the fluid when performing the impregnation method of the invention. The device 1 also includes a fluid injection device (not shown) enabling the fluid to be applied in the cavity 6.

(12) FIG. 2 shows the FIG. 1 device as obtained after performing a step of injecting an impregnation composition in the form of a resin 20 into the chamber 2. As shown, the resin 20 is injected into the empty volume 7 of the chamber 2. In the example shown, the resin 20 was injected after placing the fiber preform 10 on the support 3 between the preform 10 and the wall 4. In a variant that is not shown, the impregnation composition could be present between the fiber preform and the support. Thus, in a variant that is not shown, the impregnation composition could be inserted into the chamber prior to placing the fiber preform on top of it.

(13) Once the resin 20 has been injected, it may overlie the fiber preform 10 over substantially the entire length ? of the fiber preform 10.

(14) As mentioned above, such a configuration advantageously enables the resin 20 to infiltrate the preform 10 over a large area, thereby improving impregnation.

(15) By way of example, when the part that is to be obtained is a fan blade, the resin 20, prior to applying the fluid, may be situated beside the face of the fiber preform 10 that is to form the suction side of the blade.

(16) The layer of resin 20 present in the chamber 2 and not impregnating the fiber preform 10 may present a thickness e, as shown.

(17) Once the resin 20 is present in the chamber 2, a fluid 30, e.g. a liquid, is injected into the cavity 6 by the fluid injection device. The assembly that is obtained after adding the fluid 30 to the cavity 6 is shown in FIG. 3. The fluid 30 is applied against the wall 4 on its side opposite from the chamber 2. In other words, once the fluid 30 is applied against the wall 4, the wall 4 is present between the chamber 2 and the fluid 30. In the example shown, the fluid 30 is pressed against the wall 4 once injection of the resin 20 into the chamber 2 has terminated. Furthermore, in the example shown, once the fluid 30 has been applied, the impermeable membrane 5 is present between the applied fluid 30 and the wall 4.

(18) The applied fluid 30 exerts pressure on the wall 4 through the impermeable membrane 5. The isostatic pressure of the fluid 30 forces the resin 20 through the fiber preform 10, moves the wall 4 towards the support 3, and pushes the wall 4 against the preform 10.

(19) Application of the fluid 30 does not change the shape of the wall 4 since it is sufficiently rigid for its shape to remain unaffected by the application of the fluid 30. Thus, the application of the fluid 30 causes the wall 4 to move towards the support 3 without changing the shape of the wall 4. In particular, the face 4a of the wall 4 situated facing the fiber preform 10 conserves its shape after application of the fluid. As shown, the ends 8a and 8b of the wall 4 move towards the support 3 as a result of the fluid 30 being applied. The wall 4 presents the same shape throughout the step of impregnating the fiber preform 10 with the resin 20.

(20) The movement of the wall 4 as a result of applying the fluid 30 leads to a reduction in the volume of the chamber 2. As shown, the thickness e of the layer of resin 20 present in the chamber 2 and not impregnating the fiber preform 10 decreases progressively as a result of the pressure exerted by the fluid 30. In parallel, the impregnation front 21 of the resin 20 inside the preform 10 progresses across the thickness of the preform 10 because of the pressure exerted by the fluid 30. The impregnation front 21 of the resin 20 in the preform 10 progresses in the travel direction of the wall 4, as shown.

(21) Once the preform 10 is completely impregnated by the resin 20, the result shown in FIG. 4 is obtained. As mentioned above, the support 3 is sufficiently rigid to impart the shape of the face 3a of the facing support 3 to the face 10b of the impregnated preform. The wall 4 is sufficiently rigid to impart the shape of the face 4a of the facing wall 4 to the face 10a of the impregnated preform. In the example shown, the opposite faces 10a and 10b do not have the same shape, in particular they do not have the same curvature.

(22) FIG. 4 shows the device 1 while curing the resin 20. The isostatic pressure of the fluid 30 propagates into the resin-impregnated preform and the pressure exerted by the fluid 30 is maintained while cross-linking the resin.

(23) FIG. 5 shows the result that is obtained after densifying a fiber preform that has been impregnated with a resin that is a precursor of a densification matrix. As shown, a part 40 is obtained that comprises the fiber preform densified by a matrix. The support 3 is sufficiently rigid to impart the shape of the face 3a of the facing support 3 to the face 40b of the part 40. The wall 4 is sufficiently rigid to impart the shape of the face 4a of the facing wall 4 to the face 40a of the part 40. In the example shown, the opposite faces 40a and 40b do not have the same shape, and in particular they do not have the same curvature. As shown, the wall 4 acts during curing of the resin to maintain an isostatic pressure by using the fluid 30 applied against the wall 4. The fluid 30 may be unaffected by the densification step. In other words, the fluid 30 need not change shape during the densification step.

(24) The device 1 may include a heater member (not shown) for performing the heat treatment that enables the resin to be transformed into a densification matrix.

(25) The resulting part 40 may constitute a turbine engine blade, preferably a fan blade.

(26) The method of the invention advantageously makes it possible to control the shape of opposite faces 40a and 40b of the resulting part 40, in particular as a result of using the wall 4 and the rigid support 3.

EXAMPLES

Example 1 (Applying a Liquid)

(27) A fiber preform including carbon fibers and in the form of a plate having dimensions of 100?100?10 mm.sup.3 was placed in a chamber defined between a rigid support made of steel and having dimensions of 150?150?50 mm.sup.3 and a wall likewise made of steel and having a thickness of 2 mm.

(28) Thereafter, a volume of 40 cubic centimeters (cm.sup.3) of PR520 type epoxy resin was injected into the chamber.

(29) Thereafter, oil was applied against the wall opposite from the chamber in order to exert a pressure of 4 bars and impregnate the preform with the resin.

(30) After impregnation, a plate was obtained having a carbon fiber volume content equal to 60%. The temperature imposed during impregnation was 160? C.

(31) Thereafter, a step of densifying the impregnated fiber preform was performed by heating to 180? C. in order to cross-link the resin completely.

Example 2 (Applying a Gas)

(32) A fiber preform including carbon fibers and in the form of a plate having dimensions of 100?100?10 mm.sup.3 was placed in a chamber defined between a rigid support made of steel and having dimensions of 150?150?50 mm.sup.3 and a wall likewise made of steel and having a thickness of 2 mm.

(33) Thereafter, a volume of 40 cm.sup.3 of PR520 type epoxy resin was injected into the chamber.

(34) Thereafter, compressed air was applied against the wall opposite from the chamber in order to exert a pressure of 4 bars and impregnate the preform with the resin.

(35) After impregnation, a plate was obtained having a carbon fiber volume content equal to 60%. The temperature imposed during impregnation was 160? C.

(36) Thereafter, a step of densifying the impregnated fiber preform was performed by heating to 180? C. in order to cross-link the resin completely.

(37) The term comprising/containing a should be understood as comprising/containing at least one.

(38) The term lying in the range . . . to . . . should be understood as including the limits of the range.