METHOD FOR PREPARING THE LAYING UP AND FORMING OF A COMPOSITE PREFORM

Abstract

A method for making a first ply for laying up a fibrous preform on a tool. An attachment zone is made on the laying up surface of the tool. The zone is integral with the laying up surface of the tool. A polymer is deposited by additive manufacturing on the surface of the tool. The polymer deposit passes on the attachment zone. The first ply is laid up by activating the tackiness of the polymer deposited using additive manufacturing, so as to make the deposited fibers adhere to the material deposited by additive manufacturing.

Claims

1-10. (canceled)

11. A method for making a first ply for laying up a fibrous preform on a tool, comprising steps of: making an attachment zone on a laying up surface of the tool, the attachment zone being integral with the laying up surface of the tool; depositing a polymer by an additive manufacturing on the laying up surface of the tool, wherein said polymer deposit passes on the attachment zone; and laying up the first ply by activating tackiness of the polymer deposited using said additive manufacturing, so as to make deposited fibers adhere to a material deposited by said additive manufacturing.

12. The method according to claim 11, wherein the attachment zone is mechanically connected to a mold and comprises a surface suitable for adhesion of the polymer deposited by said additive manufacturing.

13. The method according to claim 11, wherein the attachment zone is materialized by a pressure-sensitive adhesive.

14. The method according to claim 11, wherein the polymer deposited by said additive manufacturing is a thermoplastic polymer.

15. The method according to claim 14, further comprising a step of heating during the laying up step to activate the tackiness of the polymer deposited by said additive manufacturing.

16. The method according to claim 15, wherein the laying up surface of the tool is made of a material that does not adhere to the polymer deposited by said additive manufacturing.

17. The method according to claim 11, wherein the laying up surface of the tool is convex and the attachment zone is located at a top of the tool.

18. The method according to claim 11, wherein the laying up surface of the tool is concave and the attachment zone is located at a bottom of the tool.

19. The method according to claim 1, wherein the depositing step deposits the polymer in strips organized to form a net on the laying up surface of the tool.

20. The method according to claim 17, wherein the tool comprises a recess to introduce a stiffener, a sole of the stiffener projects out in relation to the laying up surface of the tool, and the method further comprises a step of using additive manufacturing to form a gradual geometric transition zone between a top of the sole of the stiffener and the laying up surface of the tool.

Description

[0023] The invention is described below in its preferred embodiments, which are not limitative in any way, and by reference to FIGS. 1 and 2, wherein:

[0024] FIG. 1 is a schematic perspective view of the different steps for implementing an exemplary embodiment of the method according to the invention using a convex tool; and

[0025] FIG. 2 is a partial sectional view of another exemplary implementation of the method according to the invention on a tool comprising a recess for a stiffener.

[0026] In FIG. 1, the method according to the invention uses a forming tool (100). In this exemplary implementation, the laying up surface (101) of the tool is a convex surface. In a first step of implementation of this method, an attachment zone (120) is placed at the top of the tool. The extent of this attachment zone is smaller than the surface of the tool. Represented as a continuous strip in this exemplary embodiment, said attachment zone is, in an alternative exemplary embodiment (not shown), made up of attachment segments on the surface of the tool. Said attachment zone (120) is intended to maintain the link between the attachment film of the first laying up ply of the preform and the tool, at the same time making it easier to separate the film from the tool after laying up. As a non-limitative example, said attachment zone (120) is made up of a double-sided adhesive tape that is sensitive to pressure. In another embodiment, said attachment zone (120) is a mechanical part joined to the tool (100), for example using a key system, the surface of which is treated to allow the adhesion of the polymer deposited by additive manufacturing. In a second step, polymer is deposited on the laying up surface (101) by means of an additive manufacturing method, wherein depositing starts in the attachment zone. Different additive manufacturing techniques may be used to that end; as a non-limitative example, said attachment film is deposited using a technique of spraying thermoplastic polymer powder that is melted by a laser source. In an exemplary embodiment, said polymer is deposited in the form of lines (131, 132) or narrow strips to form a net so as to cover the laying up surface (101) of the tool. The mesh size of the net is adapted according to the shape and the laid up fiber. The lines (131) or strips fixed to the attachment zone (120) are deposited first, followed by the other lines (132) or strips, joined to the first ones (131). Said strips (131, 132) or lines do not adhere to the laying up surface (101) of the tool, which surface (101) is prepared to that end.

[0027] In this exemplary embodiment, this thermoplastic polymer net is used to anchor the first ply deposited by laying up during the third step of the method according to the invention. Thus, the pre-impregnated or dry fibers deposited by placing fibers during the third step adhere to the net as a result of the thermal activation of the polymer deposited using additive manufacturing. Such thermal activation is achieved by heating said polymer to a temperature sufficient to make it tacky, generally a temperature between the glass transition temperature and the melting temperature of said polymer. Said thermal activation is achieved using any means known in the prior art and compatible with the nature of the laid up fiber, for example, by mechanical contact with a heated surface, blowing hot air, laser, microwave or induction, but these examples are not exhaustive. In these last two examples of thermal activation means, the laying up surface (101) of the tool is advantageously treated to react to electromagnetic radiation in the appropriate wavelength. In another exemplary embodiment, the polymer forming the net is combined, at the time of deposition using additive manufacturing, with a phase sensitive to electromagnetic radiation, for example ferrite powder. After the first ply is attached, the laying up of the fibrous preform continues using the laying up techniques known in the prior art. When the preform is laid up, it is then removed by separating the attachment zone (120) from the attachment film. Said attachment film or the net in this exemplary embodiment remains stuck to the preform. Alternatively, said attachment film is removed from the surface of the preform using machining or abrasion.

[0028] In FIG. 2 of another exemplary implementation of the method according to the invention, the tool (200) comprises means (250) to hold a stiffener (240), the sole of which projects out in relation to the laying up surface (201). In this implementation, the method according to the invention comprises a step of creating, using additive manufacturing, gradual geometric transition zones (230) between the edges of the sole and the laying up surface (201) of the tool. The gradual raising made possible by the transition zones enables the deposited fibers to follow that rise, at the same time keeping them in contact in all locations with the preform or said transition zones.

[0029] The description above and the exemplary embodiments show that the invention achieves the objectives sought; in particular, it makes it possible to automatically make an attachment layer for the first ply on a forming tool in order to make a preform by laying up, particularly by placing fibers.