Procedure and installation for winding a pre-impregnated fabric strip onto an inclined surface

Abstract

A method for winding a pre-impregnated fabric strip (20) onto an inclined surface includes a step of deforming the strip by applying a differential traction force. This force is directed longitudinally (D) to the strip, and its value varies according to the strip's transverse direction (Dr). The application of the differential traction force is achieved by tensioning the strip between a pair of braking rollers (31, 32) and a traction device (33) located downstream of these rollers. This traction device drives the strip at different speeds depending on the strip's transverse direction (Dr). The process further includes a step of winding the deformed strip onto a surface of revolution (41) of a winding tool (40) comprising at least one portion that forms a non-zero angle with the axis of revolution (A). <40> ) of the surface of revolution (41).

Description

Background of the invention

[0001] The present invention relates to the formation of a fibrous preform by winding or wrapping a strip of fabric on an inclined surface, the preform being intended for the manufacture of parts in composite material having a non-developable shape.

[0002] As illustrated on the figure 1 A known winding method consists of depositing, between a pressure roller 61 and the non-developable outer surface of a rotating tool 62 about an axis A 62, one or more strips of fabric 70 pre-impregnated with a matrix precursor resin, the fabric strip(s) having dimensions and fiber orientations defined according to the final composite part to be produced. The pre-impregnated fabric strips 70 are wound onto the tool 62 parallel to its axis of revolution A 62.

[0003] Document EP 0 147 297 discloses a method for winding fabric strips onto a non-cylindrical rotary mandrel of revolution.

[0004] US document 2012 / 007278 A1 discloses a method and installation according to the preamble of claims 1 and 3.

[0005] While the process described above can be implemented at least semi-automatically, it does limit the quality of the preforms that can be obtained. Indeed, winding fabric strips parallel to the axis of revolution of a tool with a non-developable shape does not allow them to conform to the tool's shape. This can lead to creases in the edges of the deposited fabric strips and, consequently, irregularities in the preform, requiring subsequent machining or rework. Object and summary of the invention

[0006] It is therefore desirable to have a solution that allows pre-impregnated fabric strips to be wound onto tooling that has at least part of a non-developable surface of revolution, with strips that perfectly conform to each unique shape of the tooling, and this in an automatic and repeatable manner.

[0007] To this end, according to the invention and claim 1, a method is proposed for winding a pre-impregnated fabric strip onto an inclined surface, the pre-impregnated fabric strip extending lengthwise along a longitudinal direction and widthwise along a transverse direction, the method comprising: a step of deforming the pre-impregnated fabric strip by applying a differential tensile force to the pre-impregnated fabric strip, the tensile force being directed in the longitudinal direction of the strip, the value of the applied tensile force being different depending on the transverse direction of the strip, the application of the differential tensile force being carried out by tensioning the pre-impregnated fabric strip between, on the one hand, a pair of braking rollers and, on the other hand, a traction device present downstream of the pair of braking rollers, the traction device driving the pre-impregnated fabric strip at different speeds depending on the transverse direction of the strip, a step of winding the deformed strip onto a surface of revolution of a winding tool comprising at least one portion forming a non-zero angle with the axis of revolution of the surface of revolution.

[0008] By applying a different tensile force to the fabric strip along its transverse direction before winding it onto a non-developable surface of revolution, the strip is automatically deformed, giving it a curve by elongating one edge relative to the other. This allows the strip to more easily conform to the non-developable geometry of the winding tooling, resulting in a homogeneous, wrinkle-free preform that is obtained automatically, reliably, and repeatably. Winding speed can then be increased compared to a manually operated winding process, enabling high production rates.

[0009] The traction device includes the winding tooling having a surface of revolution comprising at least one portion forming a non-zero angle with the axis of revolution of the surface of revolution and a winding roller comprising a plurality of rollers free to rotate independently of each other, the winding tooling being driven in rotation and the winding roller exerting on the pre-impregnated fabric strip a contact pressure directed towards the surface of revolution of the winding tooling.

[0010] As the fabric web passes between the rollers of the winding roller and the surface of the winding tooling, it is deformed by the application of a differential tensile force directed along its longitudinal axis. The rollers rotate at different speeds depending on their position on the winding roller. More specifically, the roller at one end of the roller, in contact with a small-diameter section of the tooling, rotates at a lower speed than the adjacent rollers, which are in contact with larger-diameter sections of the tooling. Consequently, the tensile force applied to the web varies along its transverse direction, since the traction device formed by the winding roller and the winding tooling drives the web at different speeds depending on its transverse direction.Upon exiting the traction device, that is, when it is placed on the surface of the winding tooling, the strip is deformed to give it a curve. Thus, after deformation, the pre-impregnated fabric strip perfectly conforms to the geometry of the inclined surface of the winding tooling.

[0011] According to another embodiment of the winding process not part of the present invention, the traction device comprises first and second drive rollers, each comprising a plurality of rollers, the rollers of the first drive roller being respectively placed opposite the rollers of the second drive roller, the rollers of the first drive roller being driven in rotation at different rotational speeds while the rollers of the second drive roller are free to rotate independently of each other, the first drive roller exerting a contact pressure directed towards the second roller or vice versa.

[0012] The fabric web is deformed as it passes between the drive rollers, which move the web at different speeds depending on its transverse direction. The speed of each pair of rollers opposite the drive rollers can be set according to the geometry of the winding tooling surface onto which the web is to be deposited. Thus, after deformation, the pre-impregnated fabric web perfectly conforms to the geometry of the inclined surface of the winding tooling.

[0013] According to a particular feature of the process of the invention, it further comprises, before or during the deformation step, a heating step of the fabric strip pre-impregnated with a resin to a temperature equal to or greater than the softening temperature of the resin. This facilitates the deformation of the pre-impregnated fabric strip, particularly when the impregnation resin has a softening temperature significantly higher than the ambient temperature. The softening temperature of the resin corresponds to the temperature at which it begins to become sufficiently fluid, for example, pasty or liquid, to facilitate the deformation of the strip. However, the softening temperature is lower than the temperature at which the resin begins to polymerize.

[0014] The invention also relates, according to claim 3, to an installation for winding a pre-impregnated fabric strip onto an inclined surface, the installation comprising a winding tool having a surface of revolution having at least one portion forming a non-zero angle with the axis of revolution of the surface of revolution and a deformation device present downstream of the winding tool, the deformation device comprising a pair of braking rollers and a traction device present downstream of the pair of braking rollers, the traction device being capable of driving the pre-impregnated fabric strip at different speeds depending on the transverse direction of the strip.

[0015] The traction device includes a winding roller comprising a plurality of independently rotating rollers, the winding roller exerting a contact pressure directed towards the surface of revolution of the winding tooling. According to a particular aspect of this embodiment, the rollers of the winding roller are supported by a shaft capable of deformation in order to avoid edge effects such as pinching in the strips.

[0016] According to another embodiment of the installation not part of the present invention, the traction device comprises first and second drive rollers, each comprising a plurality of rollers, the rollers of the first drive roller being respectively placed opposite the rollers of the second drive roller, the first drive roller exerting a contact pressure directed towards the second roller or vice versa.

[0017] According to a particular feature of the installation of the invention, it further comprises a heating device located upstream of the traction device or integrated into it. Brief description of the drawings

[0018] Other features and advantages of the invention will become apparent from the following description of particular embodiments of the invention, given by way of non-limiting examples, with reference to the accompanying drawings, in which: there figure 1 is a schematic view of a winding installation according to the prior art, the figure 2 is a schematic perspective view of a winding installation for a pre-impregnated fabric strip according to an embodiment of the invention, the figure 3 is a top view of the installation of the figure 2 , there figure 4 is an enlarged view of the deformation device of the installation of the figure 2 , there figure 5is a schematic view showing the deformation of a pre-impregnated strip after passing through the deformation device of the plant. figure 2 , there figure 6 is a schematic perspective view of a winding installation for a pre-impregnated fabric strip according to another embodiment not forming part of the present invention. Detailed description of implementation methods

[0019] The invention applies generally to the winding of a pre-impregnated fabric strip on an inclined surface for the production of composite material parts corresponding in particular, but not exclusively, to parts of revolution such as rocket engine divergents.

[0020] THE figures 2 And 3represent an installation 1 for winding a pre-impregnated fabric strip according to an embodiment of the invention. The installation 1 comprises a reel 10 on which a pre-impregnated fabric strip 20 is stored, a deformation device 30 downstream of the reel 10, and a winding tool or mandrel 40 downstream of the deformation device 30 and onto which the pre-impregnated fabric strip 20 is intended to be wound.

[0021] The deformation device 30 comprises a pair of braking rollers 31 and 32 and a traction device 33 located downstream of the pair of braking rollers, the traction device 33 being capable of driving the pre-impregnated fabric strip at different speeds depending on the transverse direction of the strip. For this purpose, in the example described here and as illustrated in the figure 4The traction device includes a winding roller 330 formed by a plurality of adjacent rollers 331 that are free to rotate independently of each other. In the example described here, each roller 331 is mounted on a shaft 332 of the winding roller 330 via its own bearing (not shown in the diagram). figures 2 to 4 ) which allows it to be driven in rotation independently of the other rollers present on the shaft 332. The winding roller is held by two arms 334 and 335 connected respectively to the ends of the shaft 332. The arms 334 and 335 are connected to actuation means, for example cylinders 336 and 337, making it possible to exert on the winding roller a force F directed towards the surface of revolution 41 of the mandrel 40. In this way, the winding roller 330 exerts, via the rollers 331, a contact pressure on the surface of revolution 41 of the mandrel 40.

[0022] The surface of revolution 41 is inclined with respect to its axis of revolution A 40, that is to say, it forms a non-zero angle β with the axis A 40, which also corresponds to the axis of rotation of the chuck 40. The chuck 40 is mounted on a rotating shaft 42 which, in the example described here, is supported by a motorized spindle 43 and a tailstock 44 to drive the chuck 40 in rotation in the direction indicated by the arrow SR on the figure 2 .

[0023] The coil 10 and the deformation device 30, including the pair of braking rollers 31 and 32 and the traction device 33 (winding roller 330), are mounted on a carriage platform 2 which rests on rails 3, the carriage platform 2 being able to move on the rails 3 in two directions indicated by the double arrow DP on the figure 2as the winding progresses. The carriage platform 2 is also capable of moving along the DL direction to follow the thickness and profile of the deposited strip. In the example described here, the carriage platform 2 is connected to a worm gear 5 driven by a motor 4 to move the platform in both directions. The carriage platform 2 can be connected to any other hydraulic linear axis system.

[0024] During the winding of the pre-impregnated fabric strip 20 onto the surface 41 of the mandrel 40, the strip 20 is held against the surface 41 by the winding roller 330. As it passes between the rollers 331 of the winding roller 330 and the surface 41 of the mandrel 40, the strip 20 is deformed by the application of a differential tensile force directed along the longitudinal direction DL of the strip. The application of this differential tensile force on the pre-impregnated fabric strip 20 is achieved by tensioning it between, on the one hand, the pair of brake rollers 31 and 32 that hold the strip 20 and, on the other hand, the winding roller 330, which exerts a contact pressure on the strip 20 directed towards the surface of revolution 41 of the mandrel 40.

[0025] Furthermore, the rollers 331 are driven in rotation at different speeds depending on their position on the winding roller. More precisely, the roller 331a located at one end of the roller 330 ( figure 4 ) and in contact with a small diameter portion of the tooling 40 rotates at a lower speed compared to the other adjacent rollers 331 which are in contact with larger diameter portions of the tooling 40. The roller 331b located at the second end of the roller 330 ( figure 4 ) corresponds to the roller with the highest rotational speed, as opposed to roller 331a, which has the lowest rotational speed. The value of the traction force applied to the belt 20 is therefore different depending on the transverse direction DT of the belt, since the traction device 33, formed here by the winding roller 330, drives the belt 20 at different speeds depending on the transverse direction of the belt.

[0026] In other words, the two braking rollers 31 and 32, between which the pre-impregnated fabric strip 20 circulates, exert a braking or restraining force over the entire width of the strip 20, i.e. along the transverse direction DT of the strip 20. This braking or restraining force combined with a drive at differential speeds of the strip downstream of the braking rollers makes it possible to obtain the desired deformation.

[0027] Upon exiting the deformation device 30, i.e., when it is deposited on the surface 41 of the mandrel 40, the strip 20 is deformed so as to give it a curvature and lengthen its outer edge 20b relative to its inner edge 20b as shown in the figure 5 . There figure 5Figure 20 illustrates the strip 20 after deformation, that is, as it exits the deformation device 30. After deformation, the strip 20 has a curved shape with a substantially constant width between its inner edge 20a, corresponding to the inner radius Ri of the curved strip 20, and its outer edge 20b, corresponding to the outer radius Re of the curved strip 20. Thus, after deformation, the pre-impregnated fabric strip 20 perfectly conforms to the geometry of the inclined surface 41 of the mandrel 40.

[0028] The 20 band is a two-dimensional or three-dimensional fabric band which is formed in particular from carbon C fibers, Kevlar, or ceramic fibers, for example silica, glass, silicon carbide SiC and which has been pre-impregnated with a resin which can be chosen in particular from the following resins: epoxy resin, or matrix precursor resin, for example carbon C precursor or silicon carbide SiC precursor.

[0029] In the example described here, the installation 1 further includes a heating device 50 located upstream of the traction device, i.e., interposed between the braking rollers 31 and 32 and the winding roller 330. The heating device may be equipped, for example, with heating elements or infrared heating lamps. The heating device is intended to facilitate the deformation of the pre-impregnated fabric strip by heating it to a temperature close to the softening temperature of the impregnating resin.

[0030] However, the heating device is not essential, as deformation can already be achieved by applying differential tensile force to the belt.

[0031] According to a particular aspect of the invention, the winding roller shaft 332 is deformable, for example by using a deformable material for the shaft or by equipping it with an articulated structure. In this case, the winding roller can conform even more easily to the geometry of the mandrel's winding surface, particularly when the latter has variations in slope.

[0032] There figure 6 illustrates another winding installation according to an embodiment not forming part of the present invention and which differs from that described above in that the functions of deforming the pre-impregnated fabric strip and winding are separated. figure 6represents an installation 100 for winding a pre-impregnated fabric strip according to an embodiment of the invention. The installation 100 comprises a reel 110 on which a pre-impregnated fabric strip 120 is stored, a deformation device 130 downstream of the reel 110, a winding roller 140 and a winding tool or mandrel 150 downstream of the deformation device and on which the pre-impregnated fabric strip 120 is intended to be wound.

[0033] The coil 110, the deformation device 130 and the winding roller 140 are mounted on a trolley platform (not shown in the figure 6 ) similar to the trolley platform 2 already described in relation to the figures 2 And 3in order to move these elements as the winding progresses along the surface of revolution 151 of the chuck 150. The chuck 150 is mounted on a rotating shaft 152 supported by two pins (not shown in the figure 6 ) of which at least one includes a motor to drive the chuck 150 in rotation in the direction indicated by the arrow SR on the figure 6 and around an axis of rotation A 150 corresponding to the axis of revolution of the chuck 150.

[0034] The deformation device 130 comprises a pair of braking rollers 131 and 132 and a traction device 133 located downstream of the pair of braking rollers. The traction device 133 is capable of driving the pre-impregnated fabric strip at different speeds depending on the transverse direction of the strip. For this purpose, in the example described here, the traction device 133 comprises first and second drive rollers 134 and 135 located downstream of the braking rollers 131 and 132. The first drive roller 134 is formed by a plurality of adjacent rollers 1340 which are driven in rotation independently of each other, for example, by means of shafts nested one inside the other, each shaft being driven by a dedicated motor.The second drive roller 135 is formed by a plurality of adjacent rollers 1350 which are free to rotate independently of each other, each roller 1350 being mounted on a shaft 1352 via its own bearing (not shown in the . figure 6This allows it to be driven in rotation independently of the other rollers on the shaft 1352. The rollers 1340 of the first drive roller 134 are positioned opposite the rollers 1350 of the second drive roller 135. The first drive roller 134 is mounted on two arms 1360 and 1370. The arms 1360 and 1370 are connected to actuation means, such as cylinders, which exert a force F on the first drive roller 1340, directed towards the second drive roller 135, the latter being held in a fixed position. In this way, the first drive roller 134 exerts, via the rollers 1340, a contact pressure on the rollers 1350 of the second drive roller 135.According to one embodiment, the second drive roller is connected to arms and actuation means, for example jacks, so as to exert on the second drive roller a force directed towards the first drive roller, the latter being held in a fixed position.

[0035] The winding roller 140 is also formed of a plurality of 1400 rollers freely rotating independently of each other. The winding roller 140 is held by two arms 141 and 142 connected to actuation means such as cylinders 143 and 144, which exert a force F on the winding roller directed towards the surface of revolution 151 of the mandrel 150. In this way, the winding roller 140 exerts, via the rollers 1400, a contact pressure on the surface of revolution 151 of the mandrel 150, which compacts the pre-impregnated fabric strip 120 during its winding onto the mandrel 150. The surface of revolution 151 is inclined with respect to its axis of revolution A 150, that is to say, it forms a non-zero angle with the axis A 150, which also corresponds to the axis of rotation of the mandrel 150.

[0036] As it passes between the drive rollers 134 and 135, the belt 120 is deformed by the application of a differential tensile force directed along its longitudinal direction DL. This differential tensile force is applied to the pre-impregnated fabric belt 120 by tensioning it between, on the one hand, the pair of brake rollers 131 and 132 that hold the belt 120, and, on the other hand, the drive rollers 134 and 135, whose rollers rotate at different speeds.

[0037] More specifically, by way of non-limiting example, the pair of rollers 1340a and 1350a opposite each other located at one end of the rollers 134 and 135 rotate at a lower speed compared to those of the other pairs of rollers opposite the adjacent rollers 134 and 135. The rollers 1340b and 1350b opposite each other located at the second end of the rollers 134 and 135 correspond to the rollers which have the highest rotational speed as opposed to the rollers 1340a and 1350a which have the lowest rotational speed, the opposite rollers located between the pair of rollers 1340a and 1350a and the pair of rollers 1340b and 1350b having a rotational speed which increases progressively between the pair of rollers 1340a and 1350a and the pair of rollers 1340b and 1350b.The value of the traction force applied to the belt 120 is, therefore, different depending on the transverse direction DT of the belt since the traction device 133 formed here of the drive rollers 134 and 135 drives the belt 120 at different speeds depending on the transverse direction DT of the belt.

[0038] The speed of each pair of rollers 1340 and 1350 relative to the drive rollers 134 and 135 is determined by the geometry of the surface 151 of the mandrel 150 onto which the web 120 is to be laid. Thus, at the exit of the deformation device 130, that is, before passing between the winding roller 150 and the surface of revolution 151 of the mandrel 150, the web 120 is deformed to give it a curve and lengthen its outer edge 120b relative to its inner edge 120a. Therefore, after deformation, the pre-impregnated fabric web 120 perfectly conforms to the geometry of the inclined surface 151 of the mandrel 150.

[0039] During the winding of the pre-impregnated fabric strip 120 onto the surface 151 of the mandrel 150, the strip 120 is held pressed against the surface 151 by the winding roller 140.

[0040] In the example described here, the installation 100 further includes a heating device 160 integrated into the traction device, i.e., located between the braking rollers 131 and 132 and the drive rollers 134 and 135, so that the pre-impregnated fabric strip is heated during the deformation stage. The heating device may be equipped, for example, with heating elements or infrared heating lamps. The heating device is intended to facilitate the deformation of the pre-impregnated fabric strip by heating it to a temperature close to the softening temperature of the impregnating resin.

[0041] However, the heating device is not essential, as deformation can already be achieved by applying differential tensile force to the belt.

Claims

1. A method of winding a pre-impregnated fabric strip (20) onto a sloping surface (40), the pre-impregnated fabric strip extending lengthwise in a longitudinal direction (DL) and widthwise in a transverse direction (DT), the method comprising: • a step of deforming the pre-impregnated fabric strip (20) by applying differing traction forces to the pre-impregnated fabric strip, the traction forces being directed in the longitudinal direction (DL) of the strip, the values of the applied traction forces differing across the transverse direction (DT) of the strip, the differing traction forces being applied by tensioning the pre-impregnated fabric strip between firstly a pair of brake rollers and secondly a traction device present downstream from the pair of brake rollers (31,32), the traction device (33) driving the pre-impregnated fabric strip (20) at speeds that differ across the transverse direction (DT) of the strip; and • a step of winding the deformed strip onto a surface of revolution (41) of winding tooling (40) including at least one portion that forms a nonzero angle (β) with the axis of revolution (A40) of the surface of revolution (41), characterized the traction device (33) comprises the winding tooling (40) having a surface of revolution (41) including at least one portion forming a nonzero angle (β) with the axis of revolution (A40) of the surface of revolution (41) and a winding roller (330) having a plurality of wheels (331) that are free to rotate independently of one another, the winding tooling (40) being driven in rotation and the winding roller (330) exerting contact pressure on the pre-impregnated fabric strip (20), which pressure is directed towards the surface of revolution (41) of the winding tooling (40).

2. A method according to claim 1, further comprising, before or during the deformation step, a step of heating the fabric strip pre-impregnated with a resin to a temperature that is higher than or equal to the softening temperature of the resin.

3. An installation (1) for winding a pre-impregnated fabric strip (20) onto a sloping surface, the installation comprising winding tooling (40) presenting a surface of revolution (41) including at least one portion forming a nonzero angle (β) with the axis of revolution (A40) of the surface of revolution and a deformation device (30) present downstream from the winding tooling (40), the deformation device (30) comprising a pair of brake rollers (31, 32) and a traction device (33) present downstream from the pair of brake rollers, the traction device (33) being suitable for driving the pre-impregnated fabric strip at speeds that differ across the transverse direction (DT) of the strip characterized in that the traction device (33) comprises a winding roller (330) having a plurality of wheels (331) that are free to rotate independently of one another, the winding roller (330) exerting contact pressure directed towards the surface of revolution (41) of the winding tooling (40).

4. An installation according to claim 3, further comprising a heater device (50) present upstream from the traction device or integrated therewith.

5. An installation according to claim 3, wherein the wheels (331) of the winding roller (330) are supported by a shaft that is suitable for deforming.

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