Geodesic draping process on a non-developable shape

Abstract

Geodesic draping method on a non-developable form. The invention relates to a method for draping fibrous strips (m) onto a non-developable draping form (FQ) comprising: - a step of determining a fictitious developable form (FP), - a step of determining a set (E) of positions of the fictitious strips on the fictitious developable form (FP), and - a step of determining a set (E') of positions of the fibrous strips to be draped onto the non-developable draping form (FQ), and - a step of draping the fibrous strips (m) onto the non-developable draping form (FQ) according to the set (E) of positions of the fictitious strips. Figure for the abstract: Fig. 17

Description

Title of the invention: Geodesic draping method on a non-developable shape. Technical field

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

[0002] It is known to produce composite parts by draping layers or strata of dry or pre-impregnated fiber strips onto a mold. In some current techniques, the draping is performed manually by an operator. These techniques can lead to relatively high production costs and risks of errors in positioning the layers or fiber strips. This results in some variability in the mechanical performance of the resulting parts, or even parts with insufficient mechanical properties.

[0003] Mechanized solutions have thus been developed to reduce the production cost of these composite parts, such as the automated 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 "strands".

[0004] In the prior art, when it is desired to drape a non-developable drape shape Fo extending between a first end contour qOi and a second end contour qO2, the deposited fibers m0 and mi are arranged side by side and oriented according to the Cartesian coordinate system of the drape shape Fo, as schematically illustrated in [Fig. 1]. Several fibrous layers can thus be deposited, each fibrous layer having a different fiber orientation. It is therefore possible to achieve a quasi-isotropic drape. In the example schematically illustrated in [Fig. 1], a first fibrous layer formed by the fibers me with a first orientation and a second fibrous layer formed by the fibers mi with a second orientation different from the first orientation can thus be created.

[0005] However, it has been observed that the strands deposited using this method can exhibit significant deformations and undulations. The strength and mechanical properties of the draped part obtained by this method may therefore be insufficient. Furthermore, selecting the orientations of the strands on a non-developable drape shape can be complex in order to obtain satisfactory mechanical properties. Description of the invention

[0006] The present invention aims to overcome the aforementioned drawbacks. In particular, it has been observed that the further the draping form deviates from a cylindrical shape and the steeper its slopes, the more difficult it is to apply the wicks without waviness or deformation. Indeed, when the wick is laid on a steep slope using the prior art method(s), the two longitudinal edges of the wick do not travel the same distance along the draping form. Thus, the laid wick ripples or deforms. This phenomenon is even more pronounced when the cross-section of the draping form is small or when the width of the applied wick is large.

[0007] To this end, the invention proposes a method for 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 form, said developable form a 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 drape shape,

[0009] - a step of determining a set of positions of the fictitious strips on the a fictitious developable shape, such that the fictitious strips each extend along a trajectory corresponding to a straight line on the developed surface of the fictitious developable shape, and such that each fictitious strip extends from one of the contours and ends on 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 fibrous bands draped onto the non-developable draping form by projecting all the positions of the fictitious strips onto the non-developable draping form, and

[0011] - a draping step of the fibrous strips onto the undeveloped draping form loppable depending on the set of positions of the fictitious bands.

[0012] Thus, the draping process as described above makes it possible to drape non-developable shapes satisfactorily, 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" trajectories 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 drape shape. In particular, the surface area of ​​the fictitious developable shape may correspond to between 75% and 125% of the area of ​​the surface of the non-developable drape shape.

[0014] Thus, the fictitious developable shape is closer to the non-developable draping shape, which makes it easier to project all the positions of the fictitious strips 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 drape shape or in which the fictitious developable shape contains the non-developable drape shape.

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

[0017] Preferably, if the fictitious developable shape contains the non-developable drape shape, the volume enclosed by the fictitious developable shape represents at most 150% of the volume enclosed by the non-developable drape shape. In particular, if the fictitious developable shape contains the non-developable drape shape, the volume enclosed by the fictitious developable shape may represent at most 125% of the volume enclosed by the non-developable drape 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 shape thus determined therefore has a simple geometry while being close to the non-developable drape shape.

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

[0021] Thus, the fibrous preform obtained by the process as described above 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 frustoconical shape containing the non-developable draping shape.

[0023] The fictitious developable shape thus determined therefore has a simple geometry while being close to the non-developable drape shape.

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

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

[0026] According to a particular embodiment of the invention, the draping of the strips fibrous is achieved by programming the fictitious developable shape as a 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 in relation to all the positions of the fictitious strips.

[0028] According to a particular embodiment of the invention, the fictitious developable form includes 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 strips on the fictitious developable form.

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

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

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

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

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

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

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

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

[0037] - the positioning of a first set of parallel fictitious strips on the shape fictitious developable so as to form a first layer of fictitious strips on the fictitious developable shape, a portion of the fictitious strips of the first set extending to 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] - the deposit of a second set of parallel dummy strips on the first layer of strips so as to finish the second layer of strips and to start 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 dummy strips of the second set are positioned following the dummy strips from the first set that belong to the second layer. In order to avoid local excess thickness in the draped preform obtained, the second set of parallel dummy strips is deposited following and parallel to the first set previously deposited, in order to create a second uniform layer without excess thickness, even if it is formed by two sets of parallel dummy strips.

[0040] According to another particular embodiment of the invention, the step of determining a set of positions of the fictitious strips further includes the successive positioning 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 complete the layer of strips started by the previous set of parallel fictitious strips, the fictitious strips of the additional set being positioned parallel to the fictitious strips of the previous set belonging to said layer of strips started, a part of the fictitious strips of the additional set extending over said layer of strips thus completed so as to form at least a portion of additional layer of strips covering the layer of strips thus completed.

[0041] According to another embodiment of the invention, during the step of determining a set of positions of the fictitious strips, each set of fictitious strips positioned extends between the first fictitious strip positioned along a reference trajectory and a last 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 strips, the reference trajectory and the final trajectory correspond to generators of the fictitious developable shape.

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

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

[0045] [Fig.2] The [Fig.2] is a schematic perspective view of a non-developable drape shape.

[0046] [Fig.3] The [Fig.3] is a flowchart illustrating the draping process of the invention.

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

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

[0049] [Fig.6] The [Fig.6] is a schematic developed view of the fictitious developable shape of figures 4 and 5 on which the arrangement of a first set of parallel strips is in progress.

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

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

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

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

[0054] [Fig. 11] The [Fig. 11] is a schematic developed view of the fictitious developable shape 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] The [Fig. 12] is a schematic developed view of the fictitious developable shape on which the arrangement of a third set of parallel strips is completed.

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

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

[0058] [Fig. 15] The [Fig. 15] is a schematic perspective view of the draping shape non-developable on which the draping of the first set of parallel fibrous strips is in progress in accordance with the trajectories defined in figures 6 and 7.

[0059] [Fig. 16] The [Fig. 16] is a schematic perspective view of the non-developable draping form on which the draping of the first set of parallel fibrous strips is taking place and on which filling fibrous strips have been draped.

[0060] [Fig. 17] The [Fig. 17] is a schematic perspective view of the non-developable draping shape onto which all the parallel fibrous strip sets and the filling fibrous strips have been draped. Description of the implementation methods

[0061] The invention makes it possible to produce a fibrous preform having the shape of the part to be obtained by draping a plurality of fibrous strips over a draping form. The fibrous preform is intended to form the fibrous 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 draping shape whose draping surface is non-developable is designated as a "non-developable draping shape." 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 drape shape FQ. The drape shape FQ extends around a central axis A. The central axis A corresponds to the axis passing through the center of all the sections of the drape shape FQ. In the example illustrated in Figure 2, the drape shape FQ is a shape of revolution. The central axis A thus corresponds to the axis of revolution of the drape shape FQ. Of course, the invention remains within the scope of the invention if the non-developable drape shape is not a shape of revolution.

[0065] The draping shape FQ, or 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 with the smaller dimension. The second end contour Q2 then corresponds to the end contour of the draping shape FQ with the larger dimension.

[0066] According to the process of the invention, the draping of the non-developable draping shape Fq comprises several steps, as illustrated in [Fig.3].

[0067] According to a first step 1000 illustrated in [Fig. 4], a fictitious developable shape FP is determined from the non-developable drape shape FQ. The fictitious developable shape FP may be included in the non-developable drape shape FQ, or the fictitious developable shape FP may contain the non-developable drape shape FQ. Preferably, the fictitious developable shape FP is included in the non-developable drape shape FQ. Preferably, the fictitious developable shape FP and the non-developable drape shape FQ have the same length along the axis central A.

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

[0069] To facilitate the implementation of the method of the invention, the fictitious developable shape FP is preferably a conical or frustoconical shape. It is particularly advantageous for the fictitious developable shape FP to be the largest frustoconical shape contained within the non-developable draping shape FQ when the fictitious developable shape FP is contained within the non-developable draping shape Fq. It is particularly advantageous for the fictitious developable shape FP to be the smallest frustoconical shape that contains the non-developable draping shape FQ when the fictitious developable shape FP contains the non-developable draping shape Fq. Thus, the fictitious developable shape FP exhibits a simple geometry while having a geometry very close to that of the non-developable draping shape Fq.

[0070] More generally, the fictitious developable shape FP preferably has a simple geometry with the largest possible dimensions contained within the non-developable drape shape FQ when the fictitious developable shape FP is contained within the non-developable drape shape FQ. More generally, the fictitious developable shape FP preferably has a simple geometry with the smallest possible dimensions containing the non-developable drape shape FQ when the fictitious developable shape FP contains the non-developable drape shape FQ. Preferably, in order to obtain a fictitious developable shape FP that is as close as possible to the non-developable drape shape FQ, the aim is to obtain a fictitious developable shape FP with as many points as possible belonging to the non-developable drape shape FQ. Q-

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

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

[0073] The fictitious developable form FP may also have a complex developable form. Preferably, the fictitious developable form FP 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 FP extends around the central axis A.

[0075] Preferably, the draping form FQ is a form 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 form FQ is a form of revolution whose axis of revolution is the central axis A. Of course, it does not depart from the scope of the invention if the draping form FQ is a form of revolution whose axis of revolution is distinct from the central axis A.

[0076] The fictitious developable shape FP extends along the central axis A between a first end contour P1 and a second end contour P2. The first end contour P1 corresponds to the end contour of the smaller fictitious developable shape FP. The second end contour P2 corresponds to the end contour of the larger fictitious developable shape FP.

[0077] The length of the fictitious developable shape FP 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 shape FP comprises an infinite number of generatrices g, as illustrated in [Fig.5].

[0079] If the fictitious developable shape FP is conical or frustoconical, it is defined by an inclination angle α which corresponds to the angle formed between the central axis A of revolution and the generatrices g, as illustrated in [Fig. 5]. It will also be defined by a length R which corresponds to the length extending in the same direction as a generatrice g between the second end contour P2 and the central axis A. The length R is preferably constant angularly. It is thus defined by an opening angle θ which corresponds to the opening angle of the developed surface of the fictitious developable shape FP, as illustrated in [Fig. 5]. The mathematical relationship linking the inclination angle α to the opening angle θ is as follows: θ = 2 ir sin(α).

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

[0081] According to the invention, the position of the fictitious fibrous bands on the fictitious developable form FP is determined such that the fibers of said fibrous bands are superimposed parallel to straight lines on the developed surface of the form fictitious developable shape FP. Thus, the trajectories of the fibrous bands extend along straight lines of the developed surface of the fictitious developable shape FP.

[0082] The second step 2000 includes determining the positioning of a first set 100 of parallel strips on the fictitious developable shape FP along trajectories Ti, as illustrated in figures 6 to 10.

[0083] The position of a first strip of the first set 100 is determined along a reference trajectory T1A. Preferably, the reference trajectory T1A of the first strip of the first set corresponds to a generator g of the fictitious developable form FP.

[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 T1A and the generatrix g of the fictitious developable shape FP that intersects the first end contour Pi at the same point as the reference trajectory T1A. In the case where the reference trajectory TiA coincides with a generatrix g, as is the case in Figures 6 to 10, the reference inclination is 0°.

[0085] At least one band of the first set 100 of parallel bands extends along a trajectory TiB with generator g. As illustrated in Figures 6 and 7, the band of the first set 100 extending along a trajectory TiB with generator g is preferably the first band extending along the reference trajectory TiA, the reference trajectory TiA and the trajectory TiB with generator g thus being coincident.

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

[0087] By continuing to position adjacent strips belonging to the first set 100 along trajectories Ti parallel to the reference trajectory TiA, a strip is eventually positioned extending from the second end contour P2 back to the second end contour P2 along an extended trajectory TiC. This extended trajectory TiC can complete a full rotation of the fictitious developable shape FP, as illustrated in Figures 6 and 7. The extended trajectory TiC does not intersect the first end contour Pb but circumvents the first end contour Pb.

[0088] In the case where the reference trajectory TiA of the first strip of the first set 100 corresponds to a generatrix g of the fictitious developable form FP and in the case where the extended trajectory TiC makes a complete turn of the fictitious developable form FP, the extended trajectory Tic intersects the reference trajectory TiA 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 form FP. Indeed, these bands of the first set 100 positioned after the band extending along the extended trajectory TiC each have a first portion forming a first layer on the fictitious developable form FP followed by a second portion forming the portion of the second layer on the fictitious developable form FP.

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

[0091] As illustrated in [Fig. 10], the positioning of the first set 100 parallel strips is completed by positioning parallel strips extending between the second end contour P2 and the first end contour Pi along the extended trajectory Tic, covering the first layer of strips, until a strip extending along a final trajectory TiE is positioned. This final trajectory TiE is defined such that the angle formed between the final trajectory TiE and the generatrix g of the fictitious developable shape FP, which intersects the first end contour Pi at the same point as the final trajectory TiE, corresponds to the reference inclination of the first set 100 parallel strips. Thus, the final trajectory TiE has the same "inclination" as the reference trajectory TiA with respect to the fictitious developable shape FP.

[0092] In the example illustrated in Figures 6 to 10, the reference inclination of the first set 100 of parallel strips is 0°, that is, the reference trajectory TiA is a generatrix g of the fictitious developable form FP. Thus, the final trajectory T1E will also be a generatrix g of the fictitious developable form FP. Thus, in the example illustrated in [Fig. 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 along the extended trajectory Ijc until a strip extending along a generatrix g of the fictitious developable form FP is positioned, which will be the final trajectory T1E.

[0093] As illustrated in [Fig. 10], after positioning the first set 100 of parallel strips, a first layer of strips is obtained that completely or almost completely covers the fictitious developable shape FP, as well as a portion of a second layer. This results in a zone Zi formed by a single layer of strips and a zone Z2 formed by two layers of strips on the fictitious developable shape FP.

[0094] When angle 0 is less than or equal to 180°, the angle between the reference trajectory The angle between the reference trajectory TiA 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 strips corresponds to a percentage of the first layer of strips equal to (180°-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 TiA and the final trajectory TiE is equal to 360x(180°-0) / 0.

[0095] When angle 0 is greater than 180°, the angle between the reference trajectory and the extended trajectory TiC is equal to 0-180°. When angle 0 is greater than 180°, the area of ​​the portion of the second layer of bands corresponds to a percentage of the area of ​​the first layer of bands equal to (0-180°) / 0. When angle 0 is less than or equal to 180°, the angular offset around the central axis A between the reference trajectory TiA and the final trajectory TiE is equal to 360x(180°-0) / 0.

[0096] In the example illustrated in Figures 6 to 10, the angle 0 is 120°, which is less than 180°. Thus, the angle between the reference trajectory TiA and the extended trajectory T[C 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[E will be equal to 180°.

[0097] Next, a second set 200 of parallel strips is positioned on the fictitious developable shape FP along trajectories T2, as illustrated in [Fig. 11].

[0098] A first strip of the second set 200 is positioned along a reference trajectory T2A corresponding to the final trajectory Tm of the first set 100 of parallel strips, in the area 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 T2A is a generatrix g coinciding with the trajectory T2B of generatrix g.

[0099] Next, a plurality of adjacent strips are positioned along trajectories T2 parallel to the reference trajectory T2A, said strips extending from the second end contour P2 to the first end contour Pb. The strips of the second set 200 are thus positioned parallel to the first strip of the second set 200 in the area Zi comprising only a single layer of strips, in order to continue the construction of the second layer of strips. If the reference trajectory T2A is not itself a generator g, a strip from the second set 200 of parallel strips extending along the trajectory T2B with generator g is finally positioned.

[0100] By continuing to position adjacent strips belonging to the second Following trajectories T2 parallel to the reference trajectory T2A, a strip is finally positioned extending from the second end contour P2 back to the second end contour P2 along an extended trajectory T2C. This extended trajectory T2C can complete a full rotation of the fictitious developable shape FP, as illustrated in [Fig. 11]. The extended trajectory T2C does not intersect the first end contour Pb but circumvents it

[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 bands of the second set 200, positioned after the band extending along the extended trajectory T2C, each have a portion forming the second layer of bands followed by a portion forming the third layer of bands.

[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 emerge onto said second end contour P2 after a reduced length, without intersecting the reference trajectory T2A. These strips of the second set 200 follow end trajectories T2D, as illustrated in [Fig.11].

[0103] As illustrated in [Fig. 11], the positioning of the second set of 200 parallel strips is completed by positioning parallel strips extending between the second end contour P2 and the first end contour Pi along the extended trajectory T2C, covering the second layer of strips, until a strip extending along a final trajectory T2E is positioned. This final trajectory T2E is defined such that the angle formed between the final trajectory T2E and the generatrix g of the fictitious developable shape FP, which intersects the first end contour Pi at the same point as the final trajectory T2E, corresponds to the reference inclination of the first set of 100 parallel strips. Thus, the final trajectory T2E has the same "inclination" as the reference trajectories TiA and T2A with respect to the fictitious developable shape FP.

[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 TiA and T2A are generatrices g of the fictitious developable form FP. Thus, the final trajectory T2E will also be a generatrice g of the fictitious developable form FP. Thus, in the example illustrated in [Fig. 11], the positioning of the second set 200 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 T2C until a band extending along a generatrix g of the fictitious developable form FP, which will be the final trajectory T2E.

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

[0106] When angle 0 is less than or equal to 180°, the angle between the reference trajectory T2A and the extended trajectory T2C is equal to 0. When 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 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 T2A and the final trajectory T2E is equal to 360x(180°-0) / 0.

[0107] When angle 0 is greater than 180°, the angle between the reference trajectory T2A and the extended trajectory T2C is equal to 0-180°. When angle 0 is greater than 180°, the area of ​​the portion of the second layer corresponds to a percentage of the first layer equal to (0-180°) / 0. When 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 360x(180°-0) / 0.

[0108] In the example illustrated in [Fig. 11], the angle 0 is 120°, which is less than 180°. Thus, the angle between the reference trajectory T2A and the extended trajectory T2C 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 T2A and the final trajectory T2E will be equal to 180° on the draped part.

[0109] We can then proceed to position a third set 300 of parallel strips on the fictitious developable shape FP along trajectories T3, as illustrated in [Fig. 12].

[0110] A first strip of the third set 300 is positioned along a reference trajectory T3A corresponding to the final trajectory T2E of 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 [Fig. 12], the reference trajectory T3A is a generatrix g coinciding with the trajectory T3B of generatrix g.

[0111] A plurality of adjacent strips are then positioned along trajectories T3 parallel to the reference trajectory T3A, said strips extending from the second end contour P2 up to the first end contour Pb If the reference trajectory T3A is not itself a generator, we end up positioning a strip from the third set of parallel strips which extends along the trajectory T3B of generator g.

[0112] By continuing to position adjacent strips belonging to the third set 300 along trajectories T3 parallel to the reference trajectory T3A, a strip is eventually positioned extending from the second end contour P2 back to the second end contour P2 along an extended trajectory T3C. This extended trajectory T3C can complete a full rotation of the fictitious developable shape FP, as illustrated in [Fig. 12]. The extended trajectory T3C does not intersect the first end contour Pb but circumvents the first end contour Pb.

[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 a 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 emerge onto said second end contour P2 after a reduced length, without intersecting the reference trajectory T3A. These strips of the third set 300 follow end trajectories T3D, as illustrated in [Fig.12].

[0115] As illustrated in [Fig. 12], the positioning of the third set of 300 parallel strips is completed by positioning parallel strips extending between the second end contour P2 and the first end contour Pi along the extended trajectory T3C, covering the third layer of strips, until a strip extending along a final trajectory T3E is positioned. This final trajectory T3E is defined such that the angle formed between the final trajectory T3E and the generatrix g of the fictitious developable shape FP, which intersects the first end contour Pi at the same point as the final trajectory T3E, corresponds to the reference inclination of the first and second sets 100 and 200 of parallel strips. Thus, the final trajectory T3E has the same "inclination" as the reference trajectories TiA, T2A, and T3A with respect to the fictitious developable shape FP.

[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°, meaning that the reference trajectories T[A, T2A, and T3A are generatrices g of the fictitious developable form FP. Thus, the final trajectory T3E will also be a generatrice g of the fictitious developable form FP. Thus, in the example illustrated in [Fig. 12], the positioning of the third set 300 of parallel strips is completed by positioning Strips extending between the second end contour P2 and the first end contour Pi follow the extended trajectory T3C until a strip extending along a generatrix g of the fictitious developable shape FP is positioned; this will be the final trajectory T3E. As illustrated in [Fig. 12], after positioning the third set of 300 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 results in a zone Z4 formed by four layers of strips and a zone Z5 formed by five layers of strips on the fictitious developable shape FP.

[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 created on the fictitious developable form FP.

[0118] In the particular case illustrated in Figures 6 to 12, it can be seen that the first set of 100 parallel bands and the third set of 300 parallel bands are identical. The relationship between the number Y of parallel band sets and the number Z of band layers is as follows: Y = Z x 0 / 180°. It is preferable to obtain integer values ​​for both the number Y of parallel band sets and the number Z of band layers. In the example illustrated in Figures 6 to 12, 0 = 120°, which gives: Y = Z x 2 / 3. It can be seen in [Fig. 11] that by positioning Y = 2 parallel band sets, we obtain exactly Z = 3 band layers. It is therefore preferable to position an even number Y of parallel band sets for the case of an angle 0 of 120°.

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

[0120] The set E of positions of the fictitious strips determined in the second step 2000 is then used to drape the non-developable form FQ with fiber strips according to a fourth draping step 4000. In this fourth step 4000, the fiber strips will be draped over the non-developable form FQ according to a set E' of positions of the fiber strips. The set E' of positions of the draped fiber strips is determined as a function of the set E of positions of the strips on the fictitious developable form FP.

[0121] The set E' of positions of the draped fibrous strips can be determined according to a first embodiment in which a third anamorphosis step 3000 is performed. During this third step 3000 of determining the set E' of positions of the fibrous strips, a projection of the set E of positions of the fictitious strips is performed onto the non-developable draping shape FQ. The methods enabling such a projection from the fictitious developable shape FP onto the non-developable draping shape FQ are well known. Obviously for For a person skilled in the art, the projection of each imaginary strip onto the non-developable draping form FQ can be achieved by projecting the curve located at the center of said imaginary strip, also called the "neutral fiber". The neutral fiber is thus equidistant from each of the longitudinal edges of the imaginary strip along its entire length.

[0122] The set E' of positions of the draped fiber strips can also be determined according to a second embodiment in which said set E' of positions of the draped fiber 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 dummy developable form FP included in the non-developable draping form FQ close to said non-developable draping form FQ.

[0123] In this second embodiment, automated draping is performed 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, the fictitious developable shape FP is programmed as the draping shape. By programming the fictitious developable shape FP as the draping shape rather than the non-developable draping shape Fq, the need to calculate the set E' of fiber strip positions from the set E of fictitious strip positions is eliminated. Thus, during automated draping, the dispensing head will drape the fiber strips based on the set E of fictitious strip positions.Since the fictitious developable shape FP is included within the non-developable draping shape Fq, the dispensing head will encounter the non-developable draping shape FQ before reaching the coordinates programmed based on the fictitious developable shape FP, or at the latest upon reaching the coordinates programmed based on the fictitious developable shape FP. The dispensing head will thus drape fiber strips onto the non-developable draping shape FQ, having positions moderately different from the positions predicted by the set E of fictitious strip positions. These moderately different positions of the fiber strips will thus form the set E' of fiber strip positions. Therefore, this second embodiment allows the determination of the set E' of fiber strip positions to be performed simultaneously with the draping step 4000.

[0124] In the example illustrated in the figures, the fictitious developable shape FP extends between the first end contour Pi and the second end contour P2. The fictitious developable shape could also include 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 included 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 fibrous preform having one or more overthicknesses, 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 strips are preferably in the form of fibrous strands or layers of fabric. A "strand" is defined as a collection of long, substantially parallel fibers or filaments bound together in a nonwoven strip. The fibrous strips may comprise continuous, long fibers. When the fibrous strips are in the form of layers of fabric, they are generally formed by the woven interlacing of fibers along two directions, which are usually perpendicular to each other.

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

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

[0128] The fibrous strips may be impregnated with a thermoplastic or thermosetting material, which may contain solid fillers. The fibrous strips may also be impregnated with a thermoplastic or thermosetting material not containing solid fillers. The fibrous strips may be impregnated solely with an organic phase consisting of a thermoplastic material.

[0129] Thermoplastic materials suitable for impregnating the fibrous strips may be selected from: polyaryletherketones (PAEKs) such as polyetheretherketone (PEEK) and polyetherketoneketone (PEKK), polyetherimides (PEIs), polyphenylene sulfide (PPS), polyvinyl alcohol (PVA), aliphatic polyethers, and polysulfone (PSU). Thermosetting materials suitable for impregnating the fibrous strips may be selected from: epoxies, phenolics, and polybismaleimides (BMIs).

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

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

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

[0133] The strip or wick 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 in the form of a pair of counter-rotating rollers 5a and 5b between which the strip or wick 3 is positioned. The conveying element 5 advances the strip or wick 3 to the pressure application element 7. The pressure application element 7 applies pressure to the strip or wick 3 to deposit it onto the non-developable draping form Fq. The pressure application element 7 is in the form of a roller.

[0134] The dispensing head 1 may, in addition, include a heating element 9 located in the vicinity of the pressure application element 7. This heating element 9 allows, in the case of a strip or wick 3 impregnated with a thermoplastic polymer, the said impregnated strip or wick 3 to be heated during its dispensing in order to fluidize the thermoplastic polymer and thus to give the desired adhesion power to the dispensed strip or wick 3.

[0135] During deposition, the deposition head 1 is movable in order to apply the strip or strand 3 along a first predetermined trajectory onto 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 strand 3. After this cutting, a first fibrous strip, formed by a first section of the strip or strand 3, is thus deposited along a first trajectory onto the non-developable draping form FQ.

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

[0137] The non-developable draping shape 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 previously described.

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

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

[0141] Thus, the draping of the non-developable draping shape FQ includes the deposition of a first set of fibrous strips m along trajectories determined from the trajectories T i of the fictitious strips of the first set of fictitious strips determined during the second step 2000.

[0142] Thus, as illustrated in [Fig. 15], at least one fibrous band m of the first set of fibrous bands extends along a reference trajectory TiA' determined from the reference trajectory TiA of the corresponding fictitious band. Similarly, at least one fibrous band m of the first set of fibrous bands extends along a trajectory TiB' determined from the trajectory TiB of the generator of the corresponding fictitious band. In the example illustrated in Figures 15 to 17, the trajectories TiA' and TiB' coincide.

[0143] As illustrated in [Fig. 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 generatrix trajectory Tib. This process continues until a fibrous strip m of the first set of fibrous strips is deposited along an extended trajectory Tæ' determined from the extended trajectory TiC of the corresponding fictitious strip.

[0144] Thus, the progress of the draping on the non-developable draping form FQ illustrated in [Fig. 15] corresponds to the progress of the fictitious draping carried out on the fictitious developable form FP illustrated in Figures 6 and 7.

[0145] In the case where the non-developable drape shape FQ has a larger area than the fictitious developable shape FP, spaces may be present between The fiber strips are deposited according to the set E of positions of the fictitious strips. This is the case, for example, when the fictitious developable shape FP is included within the non-developable drape shape FQ. In this case, it can be useful to deposit filling fiber strips mc in the spaces left between the fiber strips m, as illustrated schematically in [Fig. 16]. The filling fiber strips mc are preferably made of the same material as the fiber strips m. The filling fiber strips mc can have the same width as the fiber strips m.

[0146] In the case where the non-developable drape shape FQ has a smaller area than the fictitious developable shape FP, for example when the fictitious developable shape FP contains the non-developable drape shape FQ, there will be areas where the deposited fibrous strips will 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 whose fibrous strips m are positioned in accordance with the set E' of positions of the draped fibrous strips, as illustrated in [Fig. 17].

[0148] The set of fibrous layers draped on the non-developable draping form Fq forms a fibrous 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 reverse gear rear body.

[0150] In particular, the densification step may include consolidation of the fibrous preform by a matrix followed by 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 include 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 includes a heat treatment step, possibly followed by sintering, enabling the formation of a matrix in the porosities of the fibrous preform at least partly from the matrix precursors present in said fibrous preform.

Claims

Claims

1. Method for draping fibrous strips (m) on 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 (FP), said fictitious developable form (FP) 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 (FP) having the same length along the central axis (A) as the non-developable draping form (FQ), - a step (2000) of determining a set (E) of positions of the fictitious strips on the fictitious developable form (FP), so that the fictitious strips each extend along a trajectory (Tb T2, T3) corresponding to a straight line of the developed surface of the fictitious developable form (FP),and such that each fictitious strip extends from one of the contours (Pb P2) and opens onto one of the contours (Pb P 2) of the fictitious developable shape (FP), the fictitious strips having the same width as the fibrous strips (m) to be draped, and - a step (3000) of determining a set (E') of positions of the fibrous strips (m) draped on the non-developable draping shape (Fq) by projection of the set (E) of positions of the fictitious strips onto the non-developable draping shape (FQ), and - a step (4000) of draping the fibrous strips (m) onto the non-developable draping shape (Fq) as a function of the set (E) of positions of the fictitious strips.,

2. The draping method according to claim 1, wherein the fictitious developable shape (FP) is included in the non-developable draping shape (Fq) or wherein the fictitious developable shape (FP) contains the non-developable draping shape (Fq).

3. A draping method according to claim 2, wherein the fictitious developable shape (FP) 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 (mc) between the fibrous strips (m) draped on the non-developable draping form (Fq).

5. A method of draping according to claim 2, wherein the shape deve- Fictitious loppable (FP) 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 (FP).

8. A draping method according to any one of claims 1 to 7, wherein the fictitious developable shape (FP) comprises one or more intermediate additional 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 for manufacturing a part made of composite material comprising: - producing a fiber preform by the draping method according to any one of claims 1 to 8, - densifying the fiber preform by a matrix so as to obtain a part made of composite material.

11. Composite material part obtained by the method of claim

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

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