Application head for automated fiber placement

Abstract

The invention relates to an application head (1) for automatically applying fibers, the application head comprising at least: an application roller (3) designed to apply the fibers to a mold (F), the application roller being rotatably movable on its axis for applying the fibers to the mold; and a feeding device (10) comprising a winding of a strip (12) of fibers (16) having a predefined orientation, the fiber strip being configured to be transferred to the application roller by unwinding from the feeding device, wherein at least a portion of the fibers of the strip are oriented such that they are not perpendicular to the axis of the roller.

Description

Technical Field

[0001] The present invention relates to an application head for automated fiber placement capable of depositing the fibers in a predefined orientation transversely to the direction of movement of an application roller, so as to allow obtaining the desired orientation of reinforcements for parts made of composite material of specific geometry and large dimensions, such as blades or propellers having a base with extra thickness. Background Art

[0002] Aeronautical components made of composite materials include fiber reinforcements that can be manufactured by weaving. However, when these components have large dimensions, it is complicated to manufacture the reinforcements by weaving. This is particularly likely to be the case for propulsion propellers of shell-free structures (called "open rotors"). These propellers are usually able to pivot around an axis by having a root with an extra thickness portion for fixing to the wheel disc, which is called a "bulb-shaped root" or "tulip-shaped root", with a spherical shape, for example, that is difficult to manufacture by three-dimensional weaving.

[0003] The use of automated fiber placement methods (known as "AFP") to form such parts may be considered to cope with the limitations of the braiding technology. However, using conventional methods, one may encounter the problem of swelling of the machine head deposited at the neck, that is, the area of ​​reduced diameter just above the tulip root. In fact, when this head moves along the longitudinal axis of the part, there is a risk of contacting the neck of the part. One solution is to modify the shape of the part locally, but since the parts are built for a specific function, this approach is not entirely satisfactory.

[0004] The present invention proposes a response to the limitations of the prior art. Summary of the invention

[0005] The present invention relates to an application head for automatic fiber placement, the application head comprising at least:

[0006] an application roller intended to apply the fibers to the forming tool, the application roller being rotatably movable on its axis for applying the fibers to the forming tool; and

[0007] - a feeding device comprising a winding of a fiber strip having a predefined orientation, the fiber strip being configured to be transferred to an application roller by unwinding from the feeding device, wherein at least a portion of the fibers of the strip are oriented such that they are not perpendicular to the axis of the roller.

[0008] The invention is characterized by implementing a fiber strip with a predefined orientation that allows the fiber strip to be deposited transversely to the movement of the application roller (perpendicular to its axis) instead of parallel to this movement as in conventional automated fiber placement techniques. In this way and as will be described in more detail below, the invention allows various orientations of reinforcement to be obtained for specific geometries such as a tulip-shaped root, without the risk of the head hitting the forming tool used to manufacture the part. The invention thus allows the manufacture of reinforcements for forming tools for parts of various shapes to be optimized.

[0009] In an exemplary embodiment, the head further includes a pre-application roller upstream of the application roller, the pre-application roller being movable between a retracted position configured to not apply the strip to the forming tool and a deposition position configured to apply the strip to the forming tool.

[0010] The depositing position ensures that the strip is initially applied to the forming tool, and the retracted position allows more freedom of movement of the head relative to the surface to be coated.The pre-application roller may be moved transversely to the surface of the forming tool.

[0011] In an exemplary embodiment, the strip is coated with a release film and the head further comprises a separating device capable of separating the release film from the strip upstream of the application roller.

[0012] Such a property advantageously allows the use of strips impregnated with a resin having adhesive strength at room temperature and avoids the need to heat the strips when depositing them on the forming tool. The strips can be impregnated with a matrix material or a precursor of such a material, or with a binder intended to provide adhesive strength for the deposition of the fibers but not constituting or not constituting completely the matrix to be obtained. Furthermore, the separator film can have a supporting function allowing the orientation of the fibers to be maintained. The separating device can be capable of rolling up the separated separator film.

[0013] In an exemplary embodiment, the fibers of the strip form an angle with the axis of the roller that is less than or equal to 45°, such as less than or equal to 30°, such as being substantially parallel to the axis of the roller.

[0014] In an exemplary embodiment, the head further comprises a cutting device capable of cutting the strip.

[0015] The cutting device allows the strip to be cut at the end of each deposition phase. Note that the presence of this cutting device is optional for the fibers of the strip forming a small angle with respect to the axis of the roller, the supply of the strip being stopped while the application roller continues to advance, which is sufficient to separate the deposited portion of the strip from the not yet deposited portion present on the roller.

[0016] In one exemplary embodiment, the strip comprises at least a first fiber layer having a first predefined orientation and a second fiber layer superimposed on the first fiber layer and having a second predefined orientation different from the first orientation.

[0017] Such a machine configuration allows depositing several layers of fibers simultaneously in an organized way without wrinkles and allows obtaining a more complex orientation of the reinforcement, thus allowing a better adaptation to the requirements. This therefore combines optimized overall mechanical strength with reduced draping time.

[0018] In an exemplary embodiment, the head further comprises at least one second feeding device capable of supplying one or more fiber bands configured to be transferred from the second feeding device to the application roller, wherein the fibers of the one or more bands are oriented perpendicular to the axis of the roller.

[0019] This feature relates to a "hybrid" application head that is able to deposit, simultaneously or sequentially, tapes oriented along the motion of the roller (as used in conventional AFP technology) and fiber strips oriented transversely to the motion. Such a head is particularly suitable for the manufacture of parts of complex shape requiring a change in fiber direction, in particular blades and blade roots. In the following, these tapes may be referred to as "AFP tapes".

[0020] The invention also relates to a method for manufacturing a fiber preform by automatic fiber placement using an application head as described above, comprising depositing a fiber strip at least on a forming tool by means of an application roller, at least a portion of the fibers of the strip being deposited transversely to the direction of movement of the application roller.

[0021] In particular, the method further comprises depositing one or more tapes on the forming tool by an application roller and depositing the strips sequentially or simultaneously, the fibers of the one or more tapes being deposited along the direction of movement of the application roller.

[0022] This case relates to the case where the preform is produced using the same application head (the above-mentioned "mixed" head) carrying one or more AFP tapes and fiber strips. Of course, it does not depart from the scope of the invention if the fiber preform is formed using a first application head covering a fiber strip oriented as described above and a second different application head covering one or more fiber strips corresponding to a conventional AFP application head.

[0023] In particular, the width of the deposited fiber strip may be greater than the total width of the deposited one or more fiber strips.

[0024] According to this example, the transverse fibers cover the strips by extending outside one or more strips, which advantageously allows to ensure the continuity of mechanical strength through their combination with the superimposed and offset suspension.

[0025] In an exemplary embodiment, the fiber preform is a preform of a blade or propeller tulip root, wherein the head is moved at least about the longitudinal axis of the forming tool to effect application of the fibers allowing the fiber preform to be formed.

[0026] The invention is particularly concerned with the formation of a tulip-shaped root, since it allows in particular to manufacture a structure with optimized mechanical properties, having a thick root and being continuous with the airfoil portion.

[0027] The present invention also relates to a fiber preform of a tulip-shaped root of a blade or propeller, which can be obtained by implementing the method as described above, comprising at least a first group of fiber strip portions and a second group of fiber strip portions, the fibers of the first group of fiber strip portions being oriented with a non-zero component along the longitudinal axis of the tulip-shaped root, and the fibers of the second group of fiber strip portions being oriented circumferentially around the longitudinal axis and transversely to the first group of fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] [ Figure 1 ] Figure 1 An example of an application head for automated fiber placement according to the invention is shown schematically and partially.

[0029] [ Figure 2 ] Figure 2 Shows the use of Figure 1 The head deposits the fibers with respect to the axis of the application roll and its direction of motion.

[0030] [ Figure 3 ] Figure 3 Another possible orientation of the fibers of a fiber strip is shown.

[0031] [ Figure 4 ] Figure 4 A variant of the application head according to the invention is shown schematically and partially.

[0032] [ Figure 5 ] Figure 5 A fiber preform for forming a tulip-shaped root of a blade or propeller using an application head according to the invention is schematically and partially shown.

[0033] [ Figure 6 ] Figure 6 A tulip-shaped root preform according to the invention is shown.

[0034] [ Figure 7 ] Figure 7 A variant of a multilayer tape with oriented fibers that can be used in the context of the present invention is schematically and partially shown. DETAILED DESCRIPTION

[0035] Figure 1An example of an application head 1 for automatic fiber placement according to the invention is shown. In the example considered, the head 1 comprises a body 2 enclosing a module for depositing an AFP tape and a module for depositing an oriented fiber strip. The head 1 is mounted on a movement and orientation system allowing it to achieve the same degrees of freedom as a conventional AFP head. The AFP tape deposition module corresponds to a conventional structure and comprises, in a manner known per se, a feeding device 4 capable of supplying a fiber tape 5, for example in the form of a plurality of feed reels. The tape 5 is transferred to an application roller 3 by unwinding the reel, which is intended to allow deposition on a forming tool F. To facilitate this transfer, there are guide elements 6, such as one or more rotating elements equipped with guide grooves. The roller 3 is deformable so as to adopt the local curvature of the forming tool F, thereby depositing the material in the desired local geometry. The roller 3 has a substantially cylindrical shape when at rest and is rotatable on its axis X corresponding to the height axis of the roller when moving along the forming tool F. In the accompanying drawings, the direction of movement of the roller 3 along the forming tool F is indicated by an arrow DD. The rotation of the roller 3 during deposition is again indicated by the arrow R. The strip cutting means 7 allow them to be cut to the desired length during deposition, and there are redirecting elements (not shown) to transfer the not yet deposited portion of the strip to the roller 3 after cutting. The cutting means can generally be a simple linear or rotary cutting blade, an ultrasonic vibrating blade or a laser cutting device. There are heating means 8 which allow the adhesive strength of the resin present in the strip 5 to be activated to promote its adhesion with the material already deposited. For example, the width of the strip 5 measured perpendicularly to the direction of movement DD of the roller 3 can be less than or equal to 25 mm, for example comprised between 3 mm and 25 mm.

[0036] The body 2 of the head 1 also comprises a feed device 10 comprising a winding of a strip 12 with a predefined orientation of fibers 16. The strip 12 is impregnated with a resin intended to allow adhesion to the material deposited during application by the roller 3. The strip 12 is here coated with a release film 14 which can constitute a support for the fibers of the strip, but can also provide a non-stick function to avoid undesired bonding of the layers of the rolled strip before deposition, in particular when using a resin that is viscous at room temperature (20° C.). However, if this film 14 is omitted, it does not depart from the scope of the invention. Similar to the AFP tape module 5, the strip 12 is transferred to the application roller 3 by unwinding from the feed device 10. In parallel with this transfer, the film 14 is separated by rewinding by rotating the separation device 20 before the strip 12 reaches the application roller 3. There are cutting devices 30 for cutting the strip into the desired length, as well as redirecting elements (not shown). If necessary, a guide device 17 can also be added to the AFP module. The same heating member 8 is shown which allows heating of the tape 5 and the strip 12 during their deposition, but it would not depart from the scope of the invention if there were multiple heating members for the tape and the strip, respectively. The number and position of the heating elements can be chosen as desired. It is also possible not to use a heating element if a resin having adhesive strength at room temperature is used.

[0037] Characteristically, the orientation of the fibers 16 of the strip 12 is predefined in a specific manner and transverse to the orientation of the fibers of the AFP tape. Figure 2 and Figure 3 As shown, the orientation of the fibers 16 at the roller 3 is not perpendicular to the axis X, which causes these fibers to be deposited transversely to the direction of movement DD. In other words, the fibers 16 are elongated along an extension direction that is not perpendicular to the axis X. The fibers 16 are oriented at a non-zero angle relative to the length of the strip 12. The connections between the fibers of the strip 12 in the direction DD can be relatively weak, giving the fibers 16 a certain degree of freedom to move away from each other and deform according to the length of the curve that will be described. Figure 2 As shown, the fibers 16 of the strip 12 are deposited by the roller 3 with an orientation substantially parallel to the axis X, ie substantially perpendicular to the direction of movement DD. However, the orientation of the fibers 16 can be modulated according to the desired orientation of the reinforcement of the component under consideration. Figure 3 The case of a strip 120 with fibers 160 tilted to the axis is shown. Other orientations of the fibers of the strip are also possible, such as the case of a strip 220 having at least two superimposed layers, wherein the fibers 220a of the first layer are oriented in a first orientation relative to the axis X, and the fibers 220 of the second layer superimposed on the first layer are oriented in a second orientation relative to the axis X different from the first orientation, for example the fibers 220a and 220b are oriented at + / - 30° relative to the axis X (see Figure 7). In this case, the stacked layers may have the same or different widths. As described above, for example, in the case of fibers 16 such as Figure 2 In the case of a strong tilting relative to the direction DD as shown, the cutting device 30 can be omitted. In general, the strip 12 can comprise at least one unidirectional fiber layer 16 parallel to each other. Before the strip 12 is assembled in the head 1, it is constituted by assembling and arranging the fibers 16 held together, for example, by a resin, the assembly possibly being performed on the membrane 14. The AFP tapes 5 are in turn deposited parallel to the direction DD and therefore transversely to the fibers 16. The strip 12 has a width LB measured perpendicularly to the direction DD, which is greater than the width of each tape 5. For example, the width of the strip 12 is greater than or equal to 100 mm, for example between 100 mm and 300 mm. As Figure 2 As shown, the width LB of the strips can advantageously be greater than the total (cumulative) width LR of the deposited ribbons 5. As shown, the deposited strips 12 can cover and extend beyond the area covered by the deposited ribbons 5. In general, the width LB of the strips 12 and the number of ribbons 5 to be deposited will be determined by a person skilled in the art as required. In general, the fibers of the ribbons 5 and the strips 12 can be made of carbon or glass.

[0038] Figure 4 A variant embodiment is shown in which the body 2 of the head 1 also comprises a pre-application roller 40 upstream of the roller 3, which can be moved between a retracted position PR, in which the head 1 does not press the strip 12 to deposit it on the forming tool, and a depositing position PD, in which the head 1 applies the strip 12 to the forming tool. In the example shown, the roller 40 is in the retracted position PR above the roller 3 and in the depositing position PD at the roller 3 to press the forming tool F. Those skilled in the art will recognize that various systems can be used to move the pre-application roller 40. Like the roller 3, the pre-application roller 40 is movable in rotation on its axis.

[0039] Various details have just been described relating to an example of an application head according to the invention. Although a "mixing" head has been Figure 1 , but it should be noted that it would not depart from the scope of the invention when the AFP module is omitted and the head considered comprises only the strip 12 to be deposited by the roller 3.

[0040] The following attempts to refer to Figure 5 and Figure 6 A possible use of the head according to the invention is described in the context of manufacturing a tulip-shaped root of a blade or propeller.

[0041] Figure 5A manufacturing process for a fiber preform is shown, in which a head 1 is moved about the longitudinal axis XF of a forming tool F to carry out the application of the fibers. This prevents the head from moving along the longitudinal axis XF with the risk of it colliding with the part being formed. Full or partial draping can be carried out by depositing tapes 5 and strips 12 alternately in number, width and direction to optimize the mechanical properties of the part obtained. Full or partial draping can be carried out using a machine that simultaneously distributes tapes 5 and fiber strips transversely to the direction DD. Figure 6 An example of a tulip-shaped root preform 100 obtained in the context of the present invention is shown, said tulip-shaped root preform comprising a first set of fiber strip portions formed by fibers 16 oriented with a non-zero component along the axis XF and a second set of fiber strip portions, the fibers 52 of which are oriented circumferentially around this axis and transversely to the fibers 16. The stacking and the position of the fiber strip portions and the fiber tape portions can be alternating. Thus, if the molding tool comprises the shape of the spar on which it is deposited and advantageously has material continuity between the airfoil and the tulip-shaped root, it is possible to obtain an overhang forming a tulip-shaped root as well as a portion of the airfoil. Baking can then be performed to polymerize the resin impregnating the preform so as to obtain the final part. The present invention is therefore particularly concerned with manufacturing parts with strong curvatures, such as the spherical blade root just described, in an economically efficient manner. The tulip-shaped root can be made with the same “hybrid” head 1 allowing deposition of both ribbon 5 and strip 12 , but it would not depart from the scope of the invention if a head according to the invention allowing deposition of only strip 12 and a separate conventional AFP head for deposition of ribbon 5 were used.

[0042] The expression “included between… and…” must be understood as including the limitation.

Claims

1. An application head (1) for automatic fiber placement, comprising at least: - an application roller (3) intended to apply the fibers to a forming tool (F), said application roller being rotatably movable on its axis (X) for applying the fibers to said forming tool; as well as a feeding device (10) comprising a strip (12) of wound fibers (16) having a predefined orientation, the strip of fibers being configured to be transferred to the application roller by unwinding from the feeding device, wherein at least a portion of the fibers of the strip are oriented such that they are not perpendicular to the axis of the roller, The head further comprises at least one second feeding device (4) capable of supplying one or more fiber bands (5) configured to be transferred from the second feeding device to the application roller, wherein the fibers of the one or more bands are oriented perpendicular to the axis of the roller.

2. The head (1) according to claim 1, characterized in that The head also includes a pre-application roller (40) upstream of the application roller (3), the pre-application roller being movable between a retracted position (PR) configured not to apply the strip (12) to the forming tool (F) and a deposition position (PD) configured to apply the strip to the forming tool.

3. The head (1) according to claim 1 or 2, characterized in that: The strip (12) is coated with a release film (14), and the head further comprises a separation device (20) capable of separating the release film from the strip upstream of the application roller (3).

4. The head (1) according to claim 1 or 2, characterized in that: The fibers (16) of the strip form an angle (α) less than or equal to 45° with the axis (X) of the roller.

5. The head (1) according to claim 1 or 2, characterized in that: The head also comprises cutting means (30) capable of cutting the strip (12).

6. The head (1) according to claim 1 or 2, characterized in that: The strip comprises at least a first fiber layer (220a) having a first predefined orientation and a second fiber layer (220b) superposed on the first fiber layer and having a second predefined orientation different from the first orientation.

7. A method for manufacturing a fiber preform by automatic fiber placement using an application head (1) according to any one of claims 1 to 6, comprising depositing a fiber (16) strip (12) at least on the forming tool (F) by means of an application roller (3), at least a part of the fibers of the strip being deposited transversely to the movement direction (DD) of the application roller.

8. The method according to claim 7, characterized in that The method further comprises depositing the one or more fiber bands (5) on the forming tool (F) by the application roller (3) and depositing the strips (12) sequentially or simultaneously, the fibers of the one or more bands being deposited along the direction of movement (DD) of the application roller.

9. The method according to claim 8, characterized in that The width (LB) of the deposited strip (12) of fibers (16) is greater than the total width (LR) of the deposited one or more fiber strips (5).

10. The method according to any one of claims 7 to 9, characterized in that The fiber preform is a preform of a blade or propeller tulip root, wherein the head (1) moves at least about the longitudinal axis (XF) of the forming tool to effect the application of fibers, allowing the fiber preform to be formed.

11. A fiber preform (100) for a tulip-shaped root of a blade or propeller, the fiber preform being obtainable by implementing the method according to claim 10, comprising at least a first group of fiber strip portions and a second group of fiber strip portions, the fibers (16) of the first group of fiber strip portions being oriented with a non-zero component along the longitudinal axis (XF) of the tulip-shaped root, the fibers (52) of the second group of fiber strip portions being oriented circumferentially around the longitudinal axis and transversely to the first group of fibers.

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