Mould for drying and compacting fiber preforms

Abstract

The invention relates to a mould (10) for drying fibrous preforms, said mould (10) comprising at least one portion (11) having an inner surface (13.1-13.5) defining a cavity (14) of said mould (10), said fibrous preforms wetted by a wetting liquid being intended to contact said cavity (14), said portion (11) having a structure of through-holes, the through-hole structure allows the wetting liquid to pass through the portion of the mold (10), the through-hole portion (11) comprising a plurality of intersecting filaments (17) defining through-holes (18) allowing the wetting liquid to pass through.

Description

Technical Field

[0001] The invention relates to a mould for drying and possibly compacting fiber preforms. The invention is particularly advantageous, but not exclusively, for the production of turbine components from woven preforms. Background Art

[0002] It is known to manufacture turbine components from composite materials comprising a fiber-reinforced structure embedded in a polymer matrix, known as a fiber preform. As described in documents WO-2013 / 088037 and FR-3062659, fiber preforms are produced by 3D weaving using a Jacquard loom. Looms allow the production of three-dimensional (3D) preforms by weaving multiple layers between multiple warp and weft yarn layers. These yarns are, for example, carbon yarns.

[0003] The preform is usually produced flat, that is, it has a generally flat shape at the loom exit, although its thickness may vary. The preform is then shaped, according to a shaping step, to obtain a shape that approximates the shape of the part to be manufactured. This shaping is performed by pressing against the stamping portion of the mold.

[0004] The challenge in forming is to achieve a shape that is as natural as possible without changing the weave pattern on the surface and in the core of the preform. It is important that the fibers are extensible to allow these manipulations, especially in the thickest areas of the preform. This manipulation requires sufficient wetting of the preform, as wet fibers slide together better once lubricated by a wetting liquid (usually water).

[0005] Once formed, the preform must be dried to remove the water that is undesirably retained in the mold during resin injection. In fact, the presence of water is a major disadvantage and can be a source of porosity in injection molded parts.

[0006] The operations of drying and compacting the preform are carried out using a machined mould made of metal, typically aluminium. 'Free' areas without any compacting surfaces or drainage areas, such as holes, may be provided in the mould.

[0007] However, this type of mold may tolerate a certain amount of moisture and / or require significant drying time to ensure proper drying of the fiber preform. Summary of the Invention

[0008] The object of the present invention is to effectively overcome the above-mentioned disadvantages by proposing a mold for drying fiber preforms, the mold comprising at least one portion including an inner surface defining an imprint of the mold, the fiber preform wetted by a wetting liquid being brought into contact with the imprint for shaping, characterized in that the portion has a void structure allowing the wetting liquid to pass through the portion of the mold, the portion having the void structure comprising a plurality of intersecting filaments defining through-holes for the passage of the wetting liquid.

[0009] Thus, thanks to the void structure of the portion, the present invention allows for optimization of the drying time and drying level of the preform. During the compaction operation, the fiber preform is mechanically wrung out by a counter-die that cooperates with the die stamping, and the wetting liquid can be expelled to the exterior of the die through the portion having the void structure. Furthermore, the structure comprising multiple filaments is easy to manufacture, as it is inherently well-suited to additive manufacturing by filament deposition. The present invention also allows for the creation of highly voided (that is, highly porous) structures designed to drain the fiber wetting liquid.

[0010] According to one embodiment of the present invention, the gap between two adjacent filaments is between 0.2 mm and 2 mm, or even between 0.2 mm and 1 mm.

[0011] According to one embodiment of the present invention, the mold is obtained by an additive manufacturing process of filament deposition.

[0012] According to one embodiment of the present invention, the mold further comprises a portion having a rigid structure, and the portion having the rigid structure is arranged to surround the portion having the void structure.

[0013] According to one embodiment of the present invention, the portion having the rigid structure has a higher density than the portion having the void structure.

[0014] According to an embodiment of the present invention, the portion having the rigid structure is made of a dense material.

[0015] According to one embodiment of the present invention, the portion having the void structure and the portion having the rigid structure are formed in a single piece.

[0016] According to one embodiment of the invention, the mold comprises a pneumatic connector in fluid communication with the portion having a void structure, the portion having a rigid structure defining a sealed enclosure at least partially surrounding the portion having a void structure.

[0017] According to one embodiment of the present invention, the portion having the void structure is made of amorphous thermoplastic polyetherimide resin.

[0018] The invention also relates to a method for drying a fiber preform, said method comprising at least one step of placing the fiber preform in a drying mould as previously defined. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The invention will be better understood and other characteristics and advantages will emerge from reading the following detailed description, which includes an embodiment given for illustrative purposes with reference to the accompanying drawings, which are presented by way of non-limiting examples and which may serve to complete the understanding of the description of the invention and its implementation and ultimately contribute to its definition, in which:

[0020] [ Figure 1 ] Figure 1 is a photograph of a perspective view of a compacting and drying mold according to the present invention;

[0021] [ Figure 2 ] Figure 2 is a photograph of a top view of a compacting and drying mold according to the present invention;

[0022] [ Figure 3 ] Figure 3 is a photograph of a bottom view of a compacting and drying mold according to the present invention;

[0023] [ Figure 4 ] Figure 4 Details of the void structure of the portion of the compacting and drying mold including the embossing are shown according to the present invention.

[0024] It should be noted that in the accompanying drawings, structural elements and / or functional elements common to different embodiments may have the same reference numerals. Therefore, unless otherwise specified, these elements have the same structure, size and material properties. DETAILED DESCRIPTION

[0025] Figure 1 、 2 3 show a drying and compacting mould 10 for a fiber preform (not shown), comprising a portion 11 having a void structure and a portion 12 serving as a mechanical reinforcement and / or a waterproof enclosure surrounding the first portion 11 .

[0026] The portion 11 with a void structure comprises inner surfaces 13.1-13.5 defining an embossing 14 of the mould 10, with which the fibre preform, wetted with a wetting liquid, in particular water, comes into contact for shaping. The portion 11 with a void structure allows the wetting liquid to pass through said portion of the mould 10.

[0027] In this case, the portion 12 having a rigid structure is intended to ensure force recovery during the operation of compacting the fiber preform by a mating mold that cooperates with the embossing portion 14 of the mold 10. The portion 12 having a rigid structure is arranged around the portion 11 having a void structure. The portion 12 having a rigid structure has a higher density than the portion 11 having a void structure.

[0028] More specifically, the void structure portion 11 includes two opposing, parallel side walls 15.1 and 15.2. Each side wall 15.1 and 15.2 includes an inner surface 13.1 and 13.3, respectively. These walls 15.1 and 15.2 are connected to each other by two other opposing, substantially parallel side walls 15.3 and 15.4. Each side wall 15.3 and 15.4 includes an inner surface 13.2 and 13.4, respectively. The portion 11 also has a bottom wall 15.5 including an inner surface 13.5. Thus, the void structure portion 11 has a parallelepiped shape that is open in a direction D perpendicular to the bottom wall 15.5 to accommodate the fiber preform.

[0029] like Figure 4 As shown, the portion 11 having the void structure includes a plurality of interwoven filaments 17 defining through-holes 18 .

[0030] According to exemplary embodiments, the gap L1 between two adjacent filaments 17 is between 0.2 mm and 2 mm, or even between 0.2 mm and 1 mm. Below 0.2 mm, the filaments 17 may stick together, thereby making the area "waterproof," which is contrary to the research objectives. Furthermore, too small a gap hinders the drainage of the wetting liquid. Above 2 mm, the mold fibers may mark and / or deform the preform. The width L2 or diameter of the filaments 17 is, for example, between 0.2 mm and 1 mm, or even between 0.2 mm and 0.5 mm.

[0031] The void structure may include a plurality of first parallel filaments 17 extending in a first direction D1 and a plurality of second parallel filaments 17 extending in a second direction D2. In this case, the first direction D1 and the second direction D2 form an angle of approximately 90 degrees. Alternatively, the directions D1 and D2 may form an angle of 45 degrees or any other non-zero angle suitable for the application. The gap L1 may be measured between two adjacent filaments 17 extending in the direction D1 or between two adjacent filaments 17 extending in the direction D2.

[0032] Due to the presence of through holes 18 between the filaments 17, the portion 11 allows internal circulation of the wetting liquid from at least one inner surface to at least one outer surface opposite the inner surface of the portion 11. In other words, the wetting liquid can pass directly through the portion 11.

[0033] Furthermore, the rigid portion 12 comprises two opposing and parallel side walls 21.1, 21.2, which are connected to each other via two further opposing and parallel side walls 21.3, 21.4.

[0034] The inner surfaces of the walls 21.1, 21.2 of the portion 12 are in contact with the outer surfaces of the walls 15.1, 15.2 of the portion 11. The inner surfaces of the walls 21.3, 21.4 are in contact with the outer surfaces of the walls 15.3, 15.4 of the portion 11.

[0035] Thus, the portion 12 has a parallelepiped shape which defines a through hole in the opening direction D of the portion 11 having the void structure. Thus, the bottom wall 15 . 5 of the portion 11 is open on the side of one end of the opening in the portion 12 .

[0036] Section 12 need not be open and may also include a bottom opposite to bottom wall 15.5 of section 11 having a void structure. However, the more open the mold 10 is, the easier it is for moisture in the fiber preform to escape from the mold 10. Furthermore, the mold 10 requires less material to manufacture. Consequently, manufacturing is faster and less expensive.

[0037] The portion 12 may be made of a dense material. Thus, the portion 12 does not include any internal cavities that could weaken its structure.

[0038] Of course, the mold 10 is not limited to a parallelepiped shape and may have any other geometric shape suitable for the application.

[0039] Advantageously, the pneumatic connector 23 is in fluid communication with the portion 11 having the interstitial structure. The pneumatic connector 23 is fixed to the portion 12, through which it passes. In this case, the portion 12 defines a sealed enclosure that at least partially, but preferably completely, surrounds the portion 11 having the interstitial structure (except in the upper portion of the portion 11 having the interstitial structure, the upper portion of which is intended to be closed by a cover). To this end, the outer or inner wall defining the portion 12 is sealed. Alternatively, the portion 12 is made of a dense material.

[0040] The pneumatic connector 23 is connected to a vacuum pump in order to suck the moistening liquid from the preform via the portion 11. This vacuum suction of the liquid can be performed in addition to a thermal drying or mechanical wringing process associated with a compacting force applied to the moistened fiber preform.

[0041] Depending on the level of drying required, vacuum extraction is not necessary. In fact, it is possible to carry out drying only, for example at a temperature above 100° C. to reach the boiling temperature of water, without using the pneumatic connector 23 .

[0042] Alternatively, the drying process can be carried out simultaneously with the pressing process by means of a counter-mold which presses the fiber preform against the mold 10 .

[0043] To achieve an optimal drying level, the drying process and vacuum extraction can be performed together through the mold 10. Such an embodiment requires closing the mold 10 and providing vacuum ports around the mold 10 so that the vacuum can draw the wetting liquid from the fiber preform. Alternatively, where the portion 12 includes a sealed bottom or is secured to such a bottom, a cover and seal attached to the upper surface of the portion 12 can be used.

[0044] Advantageously, the portion 11 with the void structure and the portion 12 with the rigid structure are formed in a single piece. The two portions 11 and 12 are integral with each other in a fixed manner. There can be material continuity between the portion 11 and the portion 12. In particular, there can be material continuity between the filaments 17 in the portion 11 and the filaments 17 in the portion 12. In order to give the portion 11 a void structure, the filaments 17 are, as previously described, interlaced and spaced apart. In order to give the portion 12 a rigid structure, the filaments 17 are arranged edge to edge in order to obtain a dense material, or are spaced apart by very small gaps (e.g., less than 0.2 mm).

[0045] Preferably, the entire mold 10 or at least the portion 11 (having a void structure) is made of an amorphous thermoplastic polyetherimide resin known as PEI. Advantageously, the material used is Ultem 1010 (registered trademark) because its glass transition temperature (Tg) of 215°C is compatible with a drying temperature of approximately 100°C. Furthermore, this material has good mechanical properties. Alternatively, Ultem 9085 (registered trademark) with a glass transition temperature (Tg) of 185°C can be used.

[0046] The mold 10 or at least the portion 11 (with the void structure) is preferably obtained by an additive manufacturing process of depositing filaments 17. This manufacturing method is inherently well-adapted to the part to be manufactured, as long as the manufacturing of the different rows of filaments is carried out one by one by successive addition of material. Alternatively, the mold 10 can be manufactured by metal additive manufacturing, for example in the form of a mesh, or by any other manufacturing process suitable for the application.

[0047] Alternatively, the portion 12 having a rigid structure is made of a metallic material (eg, aluminum) or a plastic material.

[0048] It should be noted that in some cases the mold 10 may be used only to dry the fiber preform, without suction or pressing other than necessary to introduce the fiber preform into the mold 10 .

[0049] The invention also relates to a method for drying a fiber preform, comprising at least one step of placing the fiber preform in a drying mold 10 .

[0050] Of course, different features, variants and / or embodiments of the present invention can be associated with one another in various combinations, as long as they are compatible with or do not exclude one another.

[0051] In addition, the present invention is not limited to the above-described embodiments and is provided by way of example only. It includes various modifications, alternative forms and other variations that can be imagined by those skilled in the art in the context of the present invention, and in particular, any combination of the above-described various operating modes can be adopted individually or in combination.

Claims

1. A method for drying a fiber preform, characterized in that The method comprises at least one step of placing the fiber preform into a mold (10) to dry the fiber preform, the fiber preform comprising at least one portion (11), the at least one portion (11) comprising an inner surface (13.1-13.5) of an imprinting portion (14) defining the mold (10), the fiber preform wetted by a wetting liquid being brought into contact with the imprinting portion (14) for shaping, the portion (11) having a void structure allowing the wetting liquid to pass through the portion of the mold (10), the portion (11) having the void structure comprising a plurality of intersecting filaments (17) defining through-holes (18) for the passage of the wetting liquid.

2. The method according to claim 2, characterized in that The gap between two adjacent filaments (17) is between 0.2 mm and 2 mm, or even between 0.2 mm and 1 mm.

3. The method according to claim 1 or 2, characterized in that The mold (10) is obtained by an additive manufacturing process of depositing filaments (17).

4. The method according to any one of claims 1 to 3, characterized in that The mold (10) further comprises a portion (12) having a rigid structure, wherein the portion (12) having a rigid structure surrounds the portion (11) having a void structure.

5. The method according to claim 4, characterized in that The portion (12) having a rigid structure has a higher density than the portion (11) having a void structure.

6. The method according to claim 4 or 5, characterized in that The portion (12) having a rigid structure is made of a dense material.

7. The method according to any one of claims 4 to 6, characterized in that The portion (11) having the void structure and the portion (12) having the rigid structure are formed in a single piece.

8. The method according to any one of claims 4 to 7, characterized in that The mold (10) includes a pneumatic connector (23) in fluid communication with the portion (11) having a void structure, and the portion (12) having a rigid structure defines a sealed enclosure at least partially surrounding the portion (11) having a void structure.

9. The method according to any one of claims 1 to 8, characterized in that The portion (11) having a void structure is made of an amorphous thermoplastic polyetherimide resin.

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