Method for geodesic layup on a non-developable shape

Abstract

The invention relates to a method for laying up fibrous strips (m) on a non-developable layup shape (FQ), comprising: - a step of determining an imaginary developable shape (F P), - a step of determining a set (E) of positions of the imaginary strips on the imaginary developable shape (F P), and - a step of determining a set (E") of positions of the fibrous strips to be laid up on the non-developable layup shape (F Q), and - a step of laying up the fibrous strips (m) on the non-developable layup shape (F Q) as a function of the set (E) of positions of the imaginary strips.

Description

Description Title of the invention: Method of geodesic draping on a non-developable shape Technical Field

[0001] The present invention relates to the general field of methods for draping a shape using fibrous strips. Prior art

[0002] It is known to produce composite parts by draping them over a form of strata or layers of dry or pre-impregnated fibrous strips. In some current techniques, draping is carried out manually by an operator. These techniques can lead to relatively high part production costs and risks of positioning errors in the layers or fibrous strips. This leads to a certain variability in the mechanical performance of the parts obtained, or even to parts with insufficient mechanical properties.

[0003] Mechanized solutions have been developed to reduce the production cost of these composite material parts, such as the automatic fiber placement technique, also known as AFP for "Automated Fiber Placement". Such a technique is described in particular in document FR 3 066 719. The fibers are then automatically deposited in the form of fibrous strips called "wicks".

[0004] In the prior art, when it is desired to drape a non-developable draping shape F o extending between a first end contour q Oi and a second end contour qo2, the wicks m0 and mi deposited are arranged next to each other and oriented according to the Cartesian coordinate system of the draping shape F o, as schematically illustrated in Figure 1. It is thus possible to deposit several fibrous layers, each fibrous layer having a different fiber orientation. It is thus possible to achieve quasi-isotropic draping. In the example schematically illustrated in Figure 1, it is thus possible to produce a first layer fibrous layer formed by the mo strands having a first orientation and a second fibrous layer formed by the mi strands having a second orientation different from the first orientation.

[0005] However, it has been found that rovings deposited using this method can exhibit significant deformations and undulations. The strength and mechanical characteristics of the draped part obtained using this method may therefore be insufficient. In addition, the choice of roving orientations on a non-developable draping form can be complex in order to obtain satisfactory mechanical characteristics. Statement of the invention

[0006] The present invention aims to overcome the aforementioned drawbacks. In particular, it has been found that the further the draping form is from the shape of a cylinder and the steeper the slopes, the more difficult it is to apply the strands without undulations or deformations. Indeed, when the strand is placed on a steep slope using the method(s) of the prior art, the two longitudinal edges of the strand do not cover the same distance on the draping form. Thus, the deposited strand undulates or deforms. This phenomenon is even more marked when the cross-section of the draping form is reduced or when the width of the applied strand is large.

[0007] To this end, the invention proposes a method of draping fibrous strips onto a non-developable draping form extending around a central axis so as to obtain a fibrous preform, the method comprising:

[0008] - a step of determining a fictitious developable shape, said fictitious developable shape extending around the central axis and extending along the central axis between a first end contour and a second end contour, the fictitious developable shape having the same length along the central axis as the non-developable draping shape,

[0009] - a step of determining a set of positions of the fictitious bands on the fictitious developable shape, so that the fictitious bands each extend along a trajectory corresponding to a straight line of the developed surface of the fictitious developable shape, and so that each fictitious band extends from one of the contours and opens onto one of the contours of the fictitious developable shape, the fictitious strips having the same width as the fibrous strips to be draped, and

[0010] - a step of determining a set of positions of the draped fibrous strips on the non-developable draping shape by projecting all of the positions of the fictitious strips onto the non-developable draping shape, and

[0011] - a step of draping the fibrous strips on the non-developable draping shape according to all the positions of the fictitious strips.

[0012] Thus, the draping process as described above makes it possible to drape non-developable shapes satisfactorily, by limiting the undulations and deformations of the deposited fibrous strips. Indeed, the trajectories of the draped fibrous strips are determined from fictitious trajectories called "geodesic" which do not generate undulations or deformations.

[0013] Preferably, the surface area of ​​the fictitious developable shape corresponds to between 50% and 150% of the surface area of ​​the non-developable draping shape. In particular, the surface area of ​​the fictitious developable shape may correspond to between 75% and 125% of the surface area of ​​the non-developable draping shape.

[0014] Thus, the fictitious developable shape is closer to the non-developable draping shape, which makes it easier to project all the fictitious strip positions onto the non-developable draping shape and the draping step.

[0015] According to a particular embodiment of the invention, the fictitious developable shape is included in the non-developable draping shape or in which the fictitious developable shape contains the non-developable draping shape.

[0016] Preferably, if the fictitious developable shape is included in the non-developable draping shape, the volume bounded by the fictitious developable shape represents at least 50% of the volume bounded by the non-developable draping shape. In particular, if the fictitious developable shape is included in the non-developable draping shape, the volume bounded by the fictitious developable shape may represent at least 75% of the volume bounded by the non-developable draping shape.

[0017] Preferably, if the fictitious developable shape contains the non-developable draping shape, the volume bounded by the fictitious developable shape represents at most 150% of the volume bounded by the non-developable draping shape. In particular, if the fictitious developable shape contains the non-developable draping shape, the volume bounded by the fictitious developable shape may represent at most 125% of the volume bounded by the non-developable draping shape.

[0018] According to another particular embodiment of the invention, the fictitious developable shape is the largest frustoconical shape included in the non-developable draping shape.

[0019] The fictitious developable form thus determined therefore presents a simple geometry while being close to the non-developable draping form.

[0020] According to a particular embodiment of the invention, the method further comprising draping fibrous filling strips between the draped fibrous strips on the non-developable draping form.

[0021] Thus, the fiber preform obtained by the process as described previously has few “free” spaces despite its non-developable shape.

[0022] According to another particular embodiment of the invention, the fictitious developable shape is the small truncated cone shape containing the non-developable draping shape.

[0023] The fictitious developable form thus determined therefore presents a simple geometry while being close to the non-developable draping form.

[0024] According to another particular embodiment of the invention, the draping is carried out by automatic placement of fibers.

[0025] The use of automatic fiber placement draping improves process repeatability and quality while limiting manufacturing costs.

[0026] According to a particular embodiment of the invention, the draping of the fibrous strips is carried out by programming the fictitious developable shape as the draping shape for the automatic placement of fibers.

[0027] This embodiment makes it possible to avoid a calculation step aimed at calculating all the positions of the fibrous strips to be draped relative to all the positions of the fictitious strips.

[0028] According to a particular embodiment of the invention, the fictitious developable shape comprises one or more additional intermediate contours present between the first end contour and the second end contour, considered as contours during the step of determining a set of positions of the fictitious bands on the fictitious developable shape.

[0029] Thus, it is possible to create a fiber preform with excess thicknesses on certain areas delimited between the contours.

[0030] The invention also relates to a fiber preform obtained by the draping process described above.

[0031] Furthermore, the invention relates to a method of manufacturing a part made of composite material comprising:

[0032] - the production of a fiber preform by the draping process as described previously,

[0033] - densification of the fiber preform by a matrix so as to obtain a part in composite material.

[0034] The invention also relates to a part made of composite material obtained by the method of manufacturing a part made of composite material as described above.

[0035] Finally, the invention relates to an aircraft engine comprising a composite material part as described previously.

[0036] According to another particular embodiment of the invention, the step of determining a set of positions of the fictitious bands comprises:

[0037] - positioning a first set of parallel fictitious strips on the fictitious developable shape so as to form a first layer of strips fictitious on the fictitious developable form, a portion of the fictitious strips of the first set extending at the level of the first layer of strips so as to form a portion of the second layer of strips which is superimposed with the first layer of strips, then

[0038] - depositing a second set of parallel fictitious strips on the first layer of strips so as to complete the second layer of strips and to begin a third layer of strips, the fictitious strips of the second set being draped parallel to the last fictitious strip of the first set belonging to the second layer of strips.

[0039] Thus, the fictitious strips of the second set are positioned following the fictitious strips of the first set which belong to the second layer. In order to avoid local excess thicknesses in the draped preform obtained, the second set of parallel fictitious strips is deposited following and parallel to the first set previously deposited, in order to produce a second uniform layer without excess thickness, even if this is formed by two sets of parallel fictitious strips.

[0040] According to another particular embodiment of the invention, the step of determining a set of positions of the fictitious strips further comprises the successive positioning(s) of one or more additional sets of parallel fictitious strips on the fictitious developable form, each additional set of parallel fictitious strips being positioned so as to terminate the layer of strips started by the preceding set of parallel fictitious strips, the fictitious strips of the additional set being positioned parallel to the fictitious strips of the preceding set belonging to said layer of strips started, a portion of the fictitious strips of the additional set extending above said layer of strips thus terminated so as to form at least a portion of additional layer of strips covering the layer of strips thus terminated.

[0041] According to another embodiment of the invention, during the step of determining a set of positions of the fictitious bands, each set of fictitious bands positioned extends between the first fictitious band positioned next a reference trajectory and a final fictitious strip positioned along a final trajectory, the angle formed between the reference trajectory and the generatrix of the fictitious developable shape which intersects the first end contour at the same point as the reference trajectory corresponding to the angle formed between the final trajectory and the generatrix of the fictitious developable shape which intersects the first end contour at the same point as the final trajectory.

[0042] According to another particular embodiment of the invention, during the step of determining a set of positions of the fictitious bands, the reference trajectory and the final trajectory correspond to generators of the fictitious developable form.

[0043] The implementation of the method of the invention will thus be facilitated, making it easier to obtain a homogeneous drape. Brief description of the drawings

[0044] [Fig. 1] Figure 1 is a schematic perspective view of a non-developable draping form on which fibrous strands according to the prior art are draped.

[0045] [Fig. 2] Figure 2 is a schematic perspective view of a non-developable draping form.

[0046] [Fig. 3] Figure 3 is a flowchart illustrating the draping method of the invention.

[0047] [Fig. 4] Figure 4 is a schematic perspective view of a fictitious developable shape derived from the non-developable draping shape of Figure 2.

[0048] [Fig. 5] Figure 5 is a schematic representation of the developed surface of the fictitious developable form of Figure 4.

[0049] [Fig. 6] Figure 6 is a developed schematic view of the fictitious developable form of Figures 4 and 5 in which the arrangement of a first set of parallel strips is in progress.

[0050] [Fig. 7] Figure 7 is a schematic perspective view of the fictitious developable form on which the arrangement of the first set of parallel strips is in progress and in the same state as in Figure 6.

[0051] [Fig. 8] Figure 8 is a developed schematic view of the fictitious developable form on which the arrangement of a first set of parallel strips is in progress and in a more advanced state than in Figures 6 and 7.

[0052] [Fig. 9] Figure 9 is a schematic perspective view of the fictitious developable form on which the arrangement of the first set of parallel strips is in progress and in the same state as in Figure 8.

[0053] [Fig. 10] Figure 10 is a developed schematic view of the fictitious developable form on which the arrangement of the first set of parallel strips is completed.

[0054] [Fig. 11] Figure 11 is a developed schematic view of the fictitious developable form on which the arrangement of a second set of parallel strips is completed, the second set of parallel strips being superimposed on the first set.

[0055] [Fig. 12] Figure 12 is a developed schematic view of the fictitious developable form on which the arrangement of a third set of parallel strips is completed.

[0056] [Fig. 13] Figure 13 is a schematic perspective view of the fictitious developable form on which all the sets of parallel strips have been arranged.

[0057] [Fig. 14] Figure 14 is a schematic sectional view of an AFP dispensing head.

[0058] [Fig. 15] Figure 15 is a schematic perspective view of the non-developable lay-up form on which the lay-up of the first set of parallel fibrous strips is in progress in accordance with the paths defined in Figures 6 and 7.

[0059] [Fig. 16] Figure 16 is a schematic perspective view of the non-developable draping form over which draping of the first set of parallel fibrous strips is in progress and over which filler fibrous strips have been draped.

[0060] [Fig. 17] Figure 17 is a schematic perspective view of the non-developable draping form onto which all sets of parallel fibrous strips and the filler fibrous strips have been draped. Description of the embodiments

[0061] The invention makes it possible to produce a fiber preform having the shape of the part to be obtained by draping a plurality of fiber strips on a draping form. The fiber preform is intended to form the fiber reinforcement of the part to be obtained.

[0062] The draping form comprises an internal or external draping surface intended to be draped by the fibrous strips. The draping of the draping form is carried out by applying fibrous strips to the draping surface of said draping form. Preferably, the draping is carried out on the external surface of the draping form, which is more accessible. However, it does not depart from the scope of the invention if the draping is carried out on the internal surface of the draping form.

[0063] The draping surface is non-developable. By extension, a "non-developable draping shape" refers to a draping shape whose draping surface is non-developable. The non-developable draping surface may have developable portions. For example, the non-developable draping surface may have a cylindrical or frustoconical portion.

[0064] Figure 2 illustrates an example of a non-developable FQ draping shape. The FQ draping shape extends around a central axis A. The central axis A corresponds to the axis passing through the center of all sections of the FQ draping shape. In the example illustrated in Figure 2, the FQ draping shape is a shape of revolution. The central axis A thus corresponds to the axis of revolution of the FQ draping shape. It is of course not outside the scope of the invention if the non-developable draping shape is not a shape of revolution.

[0065] The draping shape FQ, OR the draping surface, extends between a first end contour Qi and a second end contour Q2. If the first and second contours Qi and Q2 have different lengths, the first end contour Qi corresponds to the end contour of the draping shape FQ of smaller dimension. The second end contour Q2 then corresponds to the end contour of the draping shape FQ of larger dimension.

[0066] According to the method of the invention, the draping of the non-developable draping shape FQ comprises several steps, as illustrated in Figure 3.

[0067] According to a first step 1000 illustrated in figure 4, a fictitious developable form F is determined P from the non-developable draping form FQ. The fictitious developable form F P can be included in the non-developable draping form FQ OR the fictitious developable form F Pmay contain the non-developable draping form FQ. Preferably, the fictitious developable form F P is included in the non-developable draping form FQ. Preferably, the fictitious developable form F P and the non-developable draping shape FQ have the same length along the central axis A.

[0068] Preferably, the surface area of ​​the fictitious developable shape corresponds to between 50% and 150% of the surface area of ​​the non-developable draping shape. In particular, the surface area of ​​the fictitious developable shape may correspond to between 75% and 125% of the surface area of ​​the non-developable draping shape. Here, the surface area of ​​the draping shape intended to be draped and the surface area of ​​the fictitious developable shape on which the fictitious strips are placed are considered.

[0069] In order to facilitate the implementation of the method of the invention, the fictitious developable form F Pis preferably a conical or truncated conical shape. It is particularly interesting that the fictitious developable form F P be the largest truncated cone shape included in the non-developable draping shape FQ when the fictitious developable shape F P is included in the non-developable draping form FQ. It is particularly interesting that the fictitious developable form F P be the smallest truncated cone shape that contains the non-developable draping shape FQ when the developable shape fictitious F P contains the non-developable draping form FQ. Thus, the fictitious developable form F P has a simple geometry while having a geometry very close to that of the non-developable draping form FQ.

[0070] More generally, the fictitious developable form F Ppreferably has a simple geometry with the largest possible dimensions included in the non-developable draping shape FQ when the fictitious developable shape F P is included in the non-developable draping form FQ. More generally, the fictitious developable form F P preferably has a simple geometry with the smallest possible dimensions containing the non-developable draping shape FQ when the fictitious developable shape F P contains the non-developable draping form FQ. Preferably, in order to obtain a fictitious developable form F P as close as possible to the non-developable draping form FQ, we seek to obtain a fictitious developable form F P having the most possible points belonging to the non-developable draping form FQ.

[0071] Preferably, if the fictitious developable shape is included in the non-developable draping shape, the volume bounded by the fictitious developable shape represents at least 50% of the volume bounded by the non-developable draping shape. In particular, if the fictitious developable shape is included in the non-developable draping shape, the volume bounded by the fictitious developable shape may represent at least 75% of the volume bounded by the non-developable draping shape.

[0072] Preferably, if the fictitious developable shape contains the non-developable draping shape, the volume bounded by the fictitious developable shape represents at most 150% of the volume bounded by the non-developable draping shape. In particular, if the fictitious developable shape contains the non-developable draping shape, the volume bounded by the fictitious developable shape may represent at most 125% of the volume bounded by the non-developable draping shape.

[0073] The fictitious developable form F P may also have a complex developable form. Preferably, the fictitious developable form F P is a form of revolution, in order to simplify the implementation of the method of the invention.

[0074] As illustrated in Figures 4 and 5, the fictitious developable form F P extends around the central axis A.

[0075] Preferably, the draping shape FQ is a shape of revolution, in order to facilitate the implementation of the method of the invention. In the example illustrated in Figures 4 and 5, the draping shape FQ is a shape of revolution whose axis of revolution is the central axis A. It is of course not outside the scope of the invention if the draping shape FQ is a shape of revolution whose axis of revolution is distinct from the central axis A.

[0076] The fictitious developable form F Pextends along the central axis A between a first end contour Pi and a second end contour P2. The first end contour Pi corresponds to the end contour of the fictitious developable form F P of smaller dimension. The second end contour P2 corresponds to the end contour of the fictitious developable form F P of larger dimension.

[0077] The length of the fictitious developable form F P along the central axis A is equal to the length of the non-developable draping shape FQ.

[0078] The draping surface of the fictitious developable form F P includes an infinity of generators g, as illustrated in Figure 5.

[0079] If the fictitious developable form F Pis conical or truncated, it is defined by an angle of inclination a which corresponds to the angle formed between the central axis A of revolution and the generatrices g, as illustrated in Figure 5. It will also be defined by a length R which corresponds to the length which extends in the same direction as a generatrix g between the second end contour P2 and the central axis A. The length R is preferably angularly constant. It is thus defined by an opening angle 0 which corresponds to the opening angle of the developed surface of the fictitious developable form F P , as illustrated in Figure 5. The mathematical relationship between the inclination angle a and the opening angle 0 is: 0 = 2 n sin(o).

[0080] According to a second step 2000 illustrated in figures 6 to 13, the position of the fictitious fibrous bands on the fictitious developable shape F is determined. P . There second step 2000 thus makes it possible to determine a set E of the positions of the fictitious bands on the fictitious developable form F P .

[0081] According to the invention, the position of the fictitious fibrous strips on the fictitious developable form F P is determined so that the fibers of said fibrous bands overlap parallel to straight lines of the developed surface of the fictitious developable form F P . Thus, the trajectories of the fibrous bands extend along straight lines of the developed surface of the fictitious developable form F P .

[0082] The second step 2000 comprises determining the positioning of a first set 100 of parallel strips on the fictitious developable shape F P following trajectories Ti, as illustrated in Figures 6 to 10.

[0083] The position of a first band of the first set 100 is determined along a reference trajectory TI. A . Preferably, the reference trajectory TIA of the first band of the first set corresponds to a generator g of the fictitious developable form F P .

[0084] The first set 100 of parallel strips is defined by a reference inclination. The reference inclination is the value of the angle formed between the reference trajectory T iA and the generator g of the fictitious developable form F P which intersects the first end contour Pi at the same point as the reference trajectory T iA . In the case where reference trajectory T iA is confused with a generator g, as is the case in figures 6 to 10, the reference inclination is 0°.

[0085] At least one strip of the first set 100 of parallel strips extends along a trajectory TI Bof generator g. As illustrated in Figures 6 and 7, the strip of the first set 100 extending along a trajectory TI B of generator g is preferably the first band extending along the reference trajectory TIA, the reference trajectory TIA and the trajectory TIB of generator g thus being merged.

[0086] The position of a plurality of adjacent bands is then determined along trajectories Ti parallel to the reference trajectory TI. A , the said bands extending from the second end contour P2 to the first end contour Pi.

[0087] By continuing to position adjacent bands belonging to the first set 100 along trajectories Ti parallel to the reference trajectory T iA, we end up positioning a strip extending from the second end contour P2 until returning to the second end contour P2 following an extended trajectory Tic. This extended trajectory Tic can make a complete turn of the fictitious developable form F P , as shown in Figures 6 and 7. The extended trajectory Tic does not meet the first end contour Pi, but goes around the first end contour Pi.

[0088] In the case where the reference trajectory T iA of the first band of the first set 100 corresponds to a generator g of the fictitious developable form F P and in the case where the extended trajectory T iC completes a complete turn of the fictitious developable form F P , the extended trajectory Tic intersects the reference trajectory T iA at an angle equal to the opening angle 0 of C.

[0089] The positioning of the first set of parallel strips is then continued as illustrated in Figures 8 and 9, the strips of the first set 100 thus positioned simultaneously forming a first layer and a portion of a second layer on the fictitious developable shape F P . Indeed, these bands of the first set 100 positioned after the band extending along the extended trajectory T iC each have a first portion forming a first layer on the fictitious developable form F P followed by a second portion forming the second layer portion on the fictitious developable shape F P .

[0090] The positioning of the first set 100 of parallel strips is optionally continued by the positioning of strips close to the second end contour P2, which extend from the second end contour P2 and open onto said second end contour P2 after a reduced length, without intersecting the reference trajectory T iA . These bands of the first set 100 follow end trajectories TI D , as illustrated in Figure 8.

[0091] As illustrated in Figure 10, the positioning of the first set 100 of parallel strips is completed by positioning parallel strips extending between the second end contour P2 and the first end contour Pi following the extended trajectory Tic by covering the first layer of strips, until a strip extending along a final trajectory T is positioned. iE , the said final trajectory T iEbeing defined so that the angle formed between the final trajectory T iE and the generator g of the fictitious developable form F P which intersects the first end contour Pi at the same point as the final trajectory T iE corresponds to the reference inclination of the first set 100 of parallel strips. Thus, the final trajectory T iE has the same “inclination” as the reference trajectory T i compared to the fictitious developable form F P .

[0092] In the example illustrated in Figures 6 to 10, the reference inclination of the first set 100 of parallel strips is 0°, i.e. the reference trajectory T iA is a generator g of the fictitious developable form F P . Thus, the final trajectory T iE will also be a generator g of the fictitious developable form F P. Thus, in the example illustrated in Figure 10, the positioning of the first set 100 of parallel strips is completed by positioning strips extending between the second end contour P2 and the first end contour Pi following the extended trajectory Tic until a strip extending along a generator g of the fictitious developable form F is positioned. P , which will be the final trajectory T iE .

[0093] As illustrated in Figure 10, after positioning the first set 100 of parallel strips, a first layer of strips is obtained, completely or almost completely covering the fictitious developable shape F. P as well as a portion of the second layer. We thus obtain on the fictitious developable form F P a zone Zi formed by a single layer of bands and a zone Z2 formed by two layers of bands.

[0094] When angle 0 is less than or equal to 180°, the angle between the reference trajectory T iA and the extended trajectory Tic is equal to 0. When the angle 0 is less than or equal to 180°, the area of ​​the portion of the second layer of stripes corresponds to a percentage of the area of ​​the first layer of stripes which is equal to (180°-0) / 0. When angle 0 is less than or equal to 180°, the angular offset around the central axis A between the reference trajectory T iA and the final trajectory T iE is equal to 36Ox(18O°-0) / 0.

[0095] When the angle 0 is greater than 180°, the angle between the reference trajectory and the extended trajectory Tic is equal to 0-180°. When the angle 0 is greater than 180°, the area of ​​the portion of the second layer of stripes corresponds to a percentage of the area of ​​the first layer of stripes which is equal to (0-180°) / 0. When the angle 0 is less than or equal to 180°, the angular offset around the central axis A between the reference trajectory T iA and the final trajectory TIE is equal to 36Ox(18O°-0) / 0.

[0096] In the example shown in Figures 6 to 10, the angle 0 is 120°, which is less than 180°. Thus, the angle between the reference trajectory T iA and the extended trajectory Tic will be equal to 120°, the area of ​​the portion of the second layer will correspond to 50% of the area of ​​the first layer and the angular offset between the reference trajectory T iA and the final trajectory T iE will be equal to 180°.

[0097] We then proceed to position a second set 200 of parallel strips on the fictitious developable form F P following T2 trajectories, as illustrated in Figure 11.

[0098] A first strip of the second set 200 is positioned along a reference trajectory T 2A corresponding to the final trajectory T iD of the first set 100 of parallel strips, in the zone Zi comprising only a single layer of strips. The first strip of the second set 200 is thus positioned directly following the strips of the first set 100 belonging to the portion of the second layer and parallel to said strips of the first set 100 belonging to the second layer. In the example illustrated in FIG. 11, the reference trajectory T 2A is a generator g coincident with the trajectory T 2B of generator g.

[0099] A plurality of adjacent strips are then positioned along trajectories T2 parallel to the reference trajectory T 2A , said bands extending from the second end contour P2 to the first end contour Pi. The strips of the second set 200 are thus positioned parallel to the first strip of the second set 200 in the zone Zi comprising only one layer of strips, in order to continue the production of the second layer of strips. If the reference trajectory T 2A , is not itself a generator g, we end up positioning a strip of the second set 200 of parallel strips which extends along the trajectory T 2B of generator g.

[0100] By continuing to position adjacent bands belonging to the second set along trajectories T2 parallel to the reference trajectory T 2A, we end up positioning a strip extending from the second end contour P2 until returning to the second end contour P2 following an extended trajectory T 2C . This extended trajectory T 2C can perform a complete turn of the fictitious developable form F P , as shown in Figure 11. The extended trajectory T 2C does not meet the first end contour P b but bypasses the first end contour Pi.

[0101] The positioning of the second set 200 of parallel strips is then continued as illustrated in FIG. 11, the strips of the second set 200 thus positioned simultaneously forming the second layer of strips and a portion of the third layer of strips. Indeed, these strips of the second set 200 positioned after the strip extending along the extended trajectory T 2Ceach have a portion forming the second layer of strips followed by a portion forming the third layer portion of strips.

[0102] The positioning of the second set 200 of parallel strips is continued by positioning strips close to the second end contour P2, which extend from the second end contour P2 and open onto said second end contour P2 after a reduced length, without intersecting the reference trajectory T 2A . These bands of the second set 200 follow end trajectories T 2D , as illustrated in Figure 11.

[0103] As illustrated in Figure 11, the positioning of the second set 200 of parallel strips is completed by positioning parallel strips extending between the second end contour P2 and the first end contour Pi following the extended trajectory T 2C by covering the second layer of strips, until a strip extending along a final trajectory T is positioned 2E , the said final trajectory T 2E being defined so that the angle formed between the final trajectory T 2E and the generator g of the fictitious developable form F P which intersects the first end contour Pi at the same point as the final trajectory T 2E corresponds to the reference inclination of the first set 100 of parallel strips. Thus, the final trajectory T 2E has the same “inclination” as the reference trajectories T iA and T 2A compared to the fictitious developable form F P .

[0104] In the example illustrated in Figures 6 to 11, the reference inclination of the first set 100 and the second set 200 of parallel strips is 0°, i.e. the reference trajectories T iA and T 2Aare generators g of the fictitious developable form F P . Thus, the final trajectory T 2E will also be a generator g of the fictitious developable form F P . Thus, in the example illustrated in Figure 11, the positioning of the second set 200 of parallel strips is completed by the positioning of strips extending between the second end contour P2 and the first end contour Pi following the extended trajectory T 2C until a strip extending along a generator g of the fictitious developable form F is positioned P , which will be the final trajectory T 2E .

[0105] As illustrated in Figure 11, after positioning the second set of parallel strips, a second layer of strips is obtained, completely or almost completely covering the first layer of strips, as well as a portion of the third layer of strips. In the particular case illustrated in Figure 11, the second set of parallel strips makes it possible to produce a complete third layer of strips. This gives a zone Z3 formed by three layers of strips on the fictitious developable shape F P .

[0106] When angle 0 is less than or equal to 180°, the angle between the reference trajectory T 2A and the extended trajectory T 2Cis equal to 0. When the angle 0 is less than or equal to 180°, the area of ​​the portion of the second layer corresponds to a percentage of the area of ​​the first layer which is equal to (18O°-0) / 0. When the angle 0 is less than or equal to 180°, the angular offset around the central axis A between the reference trajectory T 2A and the final trajectory T 2E is equal to 360x(180°- 0) / 0.

[0107] When angle 0 is greater than 180°, the angle between the reference trajectory T 2A and the extended trajectory T2c is equal to 0-180°. When the angle 0 is greater than 180°, the area of ​​the portion of the second layer corresponds to a percentage of the area of ​​the first layer which is equal to (0-18O°) / 0. When the angle 0 is less than or equal to 180°, the angular offset around the central axis A between the reference trajectory and the final trajectory is equal to 36Ox(18O°-0) / 0.

[0108] In the example shown in Figure 11, angle 0 is 120°, which is less than 180°. Thus, the angle between the reference trajectory T 2A and the extended trajectory T 2C will be equal to 120°, the area of ​​the portion of the second layer will correspond to 50% of the area of ​​the first layer 100 and the angular offset between the reference trajectory T 2A and the final trajectory T 2E will be equal to 180° on the draped piece.

[0109] We can then proceed to position a third set 300 of parallel strips on the fictitious developable form F P following T3 trajectories, as illustrated in Figure 12.

[0110] A first strip of the third set 300 is positioned along a reference trajectory T 3A corresponding to the final trajectory T 2Eof the second set 200 of parallel strips. The first strip of the third set 300 is thus positioned directly following the strips of the second set 200 and parallel to said strips of the second set 200. In the example illustrated in Figure 12, the reference trajectory T 3A is a generator g coincident with the trajectory T 3B of generator g. [YES] A plurality of adjacent strips are then positioned along trajectories T3 parallel to the reference trajectory T 3A , said bands extending from the second end contour P2 to the first end contour Pi. If the reference trajectory T 3A , is not itself a generator, we end up positioning a band of the third set of parallel bands which extends along the trajectory T 3B of generator g.

[0112] By continuing to position adjacent strips belonging to the third set 300 along trajectories T3 parallel to the reference trajectory T 3A , we end up positioning a strip extending from the second end contour P2 until returning to the second end contour P2 following an extended trajectory T 3C . This extended trajectory T 3C can perform a complete turn of the fictitious developable form F P , as shown in Figure 12. The extended trajectory T 3C does not meet the first end contour Pi, but goes around the first end contour Pi.

[0113] The positioning of the third set 300 of parallel strips is then continued as illustrated in FIG. 12, the strips of the third set 300 thus positioned simultaneously forming the third layer of strips, a fourth layer of strips and a portion of the fifth layer of strips.

[0114] The positioning of the third set 300 of parallel strips is continued by positioning strips close to the second end contour P2, which extend from the second end contour P2 and open onto said second end contour P2 after a reduced length, without intersecting the reference trajectory T 3A . These bands of the third set 300 follow end trajectories T 3D , as illustrated in Figure 12.

[0115] As illustrated in Figure 12, the positioning of the third set 300 of parallel strips is completed by positioning parallel strips extending between the second end contour P2 and the first end contour Pi following the extended trajectory T 3C by covering the third layer of strips, until a strip extending along a final trajectory T is positioned 3E , the said final trajectory T 3Ebeing defined so that the angle formed between the final trajectory T 3E and the generator g of the fictitious developable form F P which intersects the first end contour Pi at the same point as the final trajectory T 3E corresponds to the reference inclination of the first and second sets 100 and 200 of parallel strips. Thus, the final trajectory T 3E presents the same "tilt" than the reference trajectories T iA , T 2A and T 3A compared to the fictitious developable form F P .

[0116] In the example illustrated in Figures 6 to 12, the reference inclination of the sets 100, 200 and 300 of parallel strips is 0°, i.e. the reference trajectories T iA , T 2A and T 3A are generators g of the fictitious developable form F P . Thus, the final trajectory T 3E will also be a generator g of the fictitious developable form F P . Thus, in the example illustrated in Figure 12, the positioning of the third set 300 of parallel strips is completed by the positioning of strips extending between the second end contour P2 and the first end contour Pi following the extended trajectory T 3C until a strip extending along a generator g of the fictitious developable form F is positioned P , which will be the final trajectory T 3E . As illustrated in Figure 12, after positioning the third set 300 of parallel strips, a fourth layer of strips is obtained, completely or almost completely covering the third layer of strips, as well as a fifth layer of strips partially covering the fourth layer of strips. This gives a zone Z4 formed by four layers of strips and a zone Z5 formed by five layers of strips on the fictitious developable shape F P .

[0117] Preferably, the successive positioning of a plurality of sets of parallel strips is carried out in this way. Several layers of strips are thus produced on the fictitious developable shape F P .

[0118] In the particular case illustrated in Figures 6 to 12, we see that the first set 100 of parallel strips and the third set 300 of parallel strips are identical. The relationship between the number Y of sets of parallel strips and the number Z of layers of strips is as follows: Y = Z x 0 / 180°. We preferably seek to obtain integer values ​​for both the number Y of sets of parallel strips and the number Z of layers of strips. In the example illustrated in Figures 6 to 12, 0 = 120°, which gives: Y = Z x 2 / 3. We can clearly see in Figure 11 that by positioning Y=2 sets of parallel strips, we obtain exactly Z=3 layers of strips. We will therefore prefer to position an even number Y of sets of parallel strips for the case of an angle 0 of 120°.

[0119] As illustrated in Figure 13, we thus obtain a set E of the positions of the bands on the fictitious developable form F P .

[0120] The set E of positions of the fictitious bands determined during the second step 2000 is then used to carry out the draping of the non-developable shape FQ with fibrous bands according to a fourth draping step 4000. In this fourth step 4000, the fibrous strips will be draped over the non-developable shape FQ in accordance with a set E' of the positions of the fibrous strips. The set E' of the positions of the draped fibrous strips is determined as a function of the set E of the positions of the strips on the fictitious developable shape F P .

[0121] The set E' of the positions of the draped fibrous strips can be determined according to a first embodiment in which a third anamorphosis step 3000 is carried out. During this third step 3000 of determining the set E' of the positions of the fibrous strips, a projection of the set E of the positions of the fictitious strips onto the non-developable draping shape FQ is carried out. The methods allowing such a projection of the fictitious developable shape F P to the non-developable draping shape FQ are well known. Obviously for those skilled in the art, the projection of each fictitious strip onto the non-developable draping shape FQ can be carried out by projecting the curve located at the center of said fictitious strip, also called "neutral fiber". The neutral fiber is thus present at an equal distance from each of the longitudinal edges of the fictitious strip over the entire length of said fictitious strip.

[0122] The set E' of positions of the draped fibrous strips can also be determined according to a second embodiment in which said set E' of positions of the draped fibrous strips is obtained at the same time as the actual draping is carried out on the non-developable draping form FQ. The implementation of this second embodiment requires an automated draping method and a fictitious developable form F P included in the non-developable draping shape FQ close to said non-developable draping shape FQ.

[0123] In this second embodiment, the automated draping is performed by using the non-developable draping shape FQ as the draping mandrel, in a conventional manner. However, instead of programming the actual draping shape, which is the non-developable draping shape FQ, as the draping shape, the fictitious developable shape F is programmed as the draping shape. P. By programming as a draping form the fictitious developable form F P rather than the non-developable draping form FQ, we free ourselves from the need to have to calculate the set E' of fiber strip positions from the set E of fictitious strip positions. Thus, during automated layup, the layup head will lay up the fiber strips based on the set E of fictitious strip positions. As the fictitious developable form F P is included in the non-developable draping shape FQ, the dispensing head will encounter the non-developable draping shape FQ before reaching the programmed coordinates based on the fictitious developable shape F P , or at the latest when reaching the programmed coordinates based on the fictitious developable form F PThe deposition head will thus proceed to drape on the non-developable draping form FQ fibrous strips having positions moderately different from the positions provided by the set E of the positions of the fictitious strips. These moderately different positions of the fibrous strips will thus form the set E' of the positions of the fibrous strips. Thus, this second embodiment makes it possible to carry out the determination of the set E' of the positions of the fibrous strips simultaneously with the draping step 4000.

[0124] In the example illustrated in the figures, the fictitious developable form F Pextends between the first end contour Pi and the second end contour P2. The fictitious developable shape could also comprise one or more intermediate contours arranged between the first end contour Pi and the second end contour P2, and fulfilling the same function as a contour during the second step 2000. The intermediate contour is preferably comprised in a plane parallel to the planes comprising the first end contour Pi and the second end contour P2. Thus, in order to produce a fiber preform having an excess thickness or several excess thicknesses, the draping of the invention could be carried out for example between the first end contour Pi and the second end contour P2, then between the intermediate end contour and one of the contours among the first end contour Pi and the second end contour P2.

[0125] The fibrous webs are preferably in the form of fibrous strands or fabric layers. A "strand" is understood to mean a collection of long fibers or filaments substantially parallel to each other and joined together in a non-woven web. Fibrous webs can consist of continuous, long fibers. In the case where the fibrous webs are in the form of fabric layers, they are usually formed by the woven interlacing of fibers in two directions, which are usually perpendicular to each other.

[0126] The fibers of the fibrous webs may be ceramic, glass, or carbon fibers. The ceramic fibers may be fibers made of a non-oxide material, such as silicon carbide (SiC), or of an oxide material, such as alumina, or of a material comprising predominantly alumina. The glass fibers may comprise a mixture predominantly based on silica.

[0127] The fibrous webs may be dry, i.e. not impregnated with a resin, pre-impregnated or filled with particles. The fibers of the dry fibrous webs may, however, be coated with a temporary binder, for example organic, which may or may not be removed before the densification of said fibrous webs.

[0128] The fibrous webs may be impregnated with a thermoplastic or thermosetting material, which may include solid fillers. The fibrous webs may also be impregnated with a thermoplastic or thermosetting material that does not include solid fillers. The fibrous webs may be impregnated solely with an organic phase consisting of a thermoplastic material.

[0129] Thermoplastic materials that can impregnate the fibrous webs can be chosen from: polyaryletherketones (PAEK) such as polyetheretherketone (PEEK) and polyetherketoneketone (PEKK), polyetherimides (PEI), polyphenylene sulfide (PPS), polyvinyl alcohol (PVA), aliphatic polyethers and polysulfone (PSU). Thermosetting materials that can impregnate the fibrous webs can be chosen from: epoxies, phenolics and polybismaleimides (BMI).

[0130] Pre-impregnation of the fibrous strips can be carried out by any conventional technique, for example by full bath dipping, by application by licking roller or by spraying.

[0131] The fibrous strips can be applied to the non-developable FQ lay-up form by manual lay-up. Preferably, in order to improve the repeatability and quality of the application of the fibrous strips to the non-developable FQ lay-up form while reducing the operating time, the fibrous strips are applied to the non-developable FQ form by automatic fiber placement.

[0132] Figure 14 schematically illustrates the structure of a deposition head 1 of a device for implementing an automatic fiber placement technique. The structure of the deposition head 1 is well known. The deposition head 1 is fed by the fiber strips 3, preferably in the form of wicks. Advantageously, each fiber strip 3 is formed by a set of several wicks.

[0133] The strip or roving 3 can be conveyed by a conveying element 5 to a pressure application element 7 located on the side of the non-developable draping form FQ. The conveying element 5 is here in the form of a pair of counter-rotating rollers 5a and 5b between which the strip or roving 3 is present. The conveying element 5 makes it possible to advance the strip or roving 3 to the pressure application element 7. The pressure application element 7 applies pressure to the strip or roving 3 in order to carry out the deposition on the non-developable draping form FQ. The pressure application element 7 is here in the form of a roller.

[0134] The deposition head 1 may, in addition, comprise a heating element 9 located in the vicinity of the pressure application element 7. This heating element 9 makes it possible, in the case of a strip or wick 3 impregnated with a thermoplastic polymer, to heat said impregnated strip or wick 3 during its deposition in order to fluidify the thermoplastic polymer and thus to confer the desired adhesive power to the strip or wick 3 deposited.

[0135] During deposition, the deposition head 1 is movable in order to apply the strip or wick 3 along a first determined trajectory on the non-developable draping form FQ. Once the application has been carried out along this first trajectory, a cutting element 8 of the deposition head 1 cuts the strip or wick 3. After this cutting, the deposition of a first fibrous strip is thus obtained, formed by a first section of the strip or wick 3, along a first trajectory on the non-developable draping shape FQ.

[0136] The draping operation is then continued by advancing the strip or roving 3 in the deposition head 1 to the pressure application element 7 by actuating the conveying element 5. The deposition head 1 can be moved in order to deposit the roving or strip 3 along a second trajectory on the non-developable draping form FQ. The deposition of a second fibrous strip, formed by a second section of the strip or roving 3 along a second trajectory, is then obtained in a manner similar to that described previously.

[0137] The non-developable draping form FQ can obviously be rotated around its central axis A during draping to facilitate the deposition of the fibrous strips.

[0138] The draping is then continued by depositing several fibrous strips in the same manner as described previously.

[0139] Figures 15 to 17 illustrate the fourth step 4000 of draping fibrous strips m onto the non-developable draping form FQ.

[0140] The fibrous strips m are arranged on the non-developable draping form FQ in accordance with the set E' of positions of the draped fibrous strips. Thus, the fibrous strips m are arranged on the non-developable draping form FQ in accordance with trajectories determined from the trajectories T1, T2, T3 of the fictitious strips determined during the second step 2000. Thus, the fourth step comprises the draping of several sets of fibrous strips m, each set of fibrous strips m deposited corresponding to a set of fictitious strips as determined during the second step 2000.

[0141] Thus, the draping of the non-developable draping form FQ comprises the deposition of a first set of fibrous strips m following trajectories determined from the trajectories Ti of the fictitious strips of the first set of fictitious strips determined during the second step 2000. Tl

[0142] Thus, as illustrated in Figure 15, at least one fibrous strip m of the first set of fibrous strips extends along a reference trajectory TIA' determined from the reference trajectory T iA of the corresponding fictitious band. Similarly, at least one fibrous band m of the first set of fibrous bands extends along a trajectory TI B ' determined from the trajectory T iB of the generator of the corresponding fictitious band. In the example illustrated in figures 15 to 17, the trajectories TIA' and TIB' are merged.

[0143] As illustrated in Figure 15, a plurality of fibrous strips are then deposited along trajectories corresponding to the trajectories Ti of the adjacent fictitious strips parallel to the fictitious strip extending along the reference trajectory TIA OR the generator trajectory TIB. This continues until a fibrous strip m of the first set of fibrous strips extending along an extended trajectory Tic' determined from the extended trajectory Tic of the corresponding fictitious strip is deposited.

[0144] Thus, the progress of the draping on the non-developable draping shape FQ illustrated in Figure 15 corresponds to the progress of the fictitious draping carried out on the fictitious developable shape F P illustrated in Figures 6 and 7.

[0145] In the case where the non-developable draping shape FQ has a larger area than the fictitious developable shape F P, spaces may be present between the deposited fibrous bands depending on the set E of positions of the fictitious bands. This is for example the case when the fictitious developable form F P is included in the non-developable draping form FQ. In this case, it may be useful to deposit fibrous filling strips m c in the spaces left between the fibrous bands m, as illustrated very schematically in Figure 16. The fibrous filling bands m c are preferably made of the same material as the fibrous strips m. The fibrous filling strips m c may have the same width as the fibrous bands m.

[0146] In the case where the non-developable draping shape FQ has a smaller area than the fictitious developable shape F P , for example when the form fictitious developable F Pcontains the non-developable drape form FQ, there will be areas where the deposited fibrous bands overlap.

[0147] When the draping of the first set of fibrous strips m is completed, the draping of the other sets of fibrous strips m is carried out according to the results of the second step 2000, until several sets of fibrous strips m are obtained, the fibrous strips m of which are positioned in accordance with the set E' of the positions of the draped fibrous strips, as illustrated in Figure 17.

[0148] The set of fiber layers draped over the non-developable draping form FQ forms a fiber preform.

[0149] The fibrous preform thus obtained can be densified in a well-known manner by a matrix to obtain a part made of composite material, for example an engine exhaust cone or a rear inverter body.

[0150] In particular, the densification step may include consolidation of the fiber preform by a matrix and then sintering of the matrix.

[0151] If the fibrous strips are impregnated with a binder, debinding can be carried out before densification by the matrix.

[0152] If the fibrous strips are not impregnated with a matrix precursor, the densification step may comprise a step of injecting a matrix precursor into the porosities of the fibrous preform, then transforming it into a matrix by heat treatment.

[0153] If the fibrous strips are impregnated with a matrix precursor, the densification step comprises a heat treatment step, possibly followed by sintering, making it possible to form a matrix in the porosities of the fibrous preform at least in part from the matrix precursors present in said fibrous preform.

Claims

Claims

1. A method of draping fibrous strips (m) onto a non-developable draping form (FQ) extending around a central axis (A) so as to obtain a fibrous preform, the method comprising: - a step (1000) of determining a fictitious developable form (F P ), said fictitious developable form (F P ) extending around the central axis (A) and extending along the central axis (A) between a first end contour (Pi) and a second end contour (P2), the fictitious developable form (F P ) having the same length along the central axis (A) as the non-developable draping shape (FQ), - a step (2000) of determining a set (E) of positions of the fictitious bands on the fictitious developable form (F P), so that the fictitious bands each extend along a trajectory (Ti, T2, T3) corresponding to a straight line of the developed surface of the fictitious developable form (F P ), and so that each fictitious band extends from one of the contours (Pi, P2) and opens onto one of the contours (Pi, P2) of the fictitious developable form (F P ), the fictitious strips having the same width as the fibrous strips (m) to be draped, and - a step (3000) of determining a set (E 7 ) of positions of the fibrous bands (m) draped on the non-developable draping shape (FQ) by projection of the set (E) of positions of the fictitious bands on the non-developable draping shape (FQ), and - a step (4000) of draping the fibrous strips (m) on the non-developable draping shape (FQ) as a function of the set (E) of positions of the fictitious strips.

2. A draping method according to claim 1, wherein the fictitious developable shape (F P ) is included in the non-developable draping form (FQ) OR in which the fictitious developable form (F P ) contains the non-developable draping form (FQ).

3. A draping method according to claim 2, wherein the fictitious developable shape (F P ) is the largest frustoconical shape included in the non-developable draping shape (FQ).

4. A method of draping according to claim 3, wherein the method further comprises draping fibrous filler strips (m c ) between the fibrous strips (m) draped on the non-developable draping form (FQ).

5. A draping method according to claim 2, wherein the fictitious developable shape (F P) is the smallest frustoconical shape containing the non-developable draping shape (FQ).

6. A method of draping according to any one of claims 1 to 5, wherein the draping is carried out by automatic placement of fibers.

7. A draping method according to claim 6, wherein the draping of the fibrous strips (m) is carried out by programming as draping shape for automatic fiber placement the fictitious developable shape (F P ).

8. A draping method according to any one of claims 1 to 7, wherein the fictitious developable shape (F P ) comprises one or more additional intermediate contours present between the first end contour (Pi) and the second end contour (P2), considered as contours during the step (2000) of determining a set (E) of positions of the fictitious bands on the fictitious developable shape (FP ).

9. Fibrous preform obtained by the draping process according to any one of claims 1 to 8.

10. Method of manufacturing a part made of composite material comprising: - the production of a fiber preform by the draping process according to any one of claims 1 to 8, - densification of the fiber preform by a matrix so as to obtain a part in composite material.

11. Part made of composite material obtained by the method of claim 10.

12. Aircraft engine comprising a composite material part according to claim 11.

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