Method for producing a 3D composite element

Abstract

The invention relates to a method for producing a 3D composite element (2), comprising the following steps: - implementing at least one non-continuous strip (1) comprising long fibres oriented along the longitudinal axis of said non-continuous strip (1) and composed of segments (3), at least one segment (3) comprising a zone (4) of release to another adjacent segment (3), - producing a preform (7) comprising at least one non-continuous strip (1), - activating the release zone(s) (4), and - obtaining the 3D composite element (2).

Description

Description Title of the invention: Method for manufacturing a 3D composite element

[0001] The present invention relates to the technical field of manufacturing processes for a 3D composite element.

[0002] In the above field, there are known techniques for manufacturing a 3D composite element from a ribbon of material, including a molding step to obtain a desired final shape.

[0003] However, these techniques are very limiting both in terms of the materials used and the possible shapes.

[0004] There are also known manufacturing processes for hollow and tubular composite parts that include a step of transforming a preform by internal pressure within a female tooling. Such processes must address the issue of the difference in perimeter between the layers constituting the preform and the perimeter of the layers constituting the final part after consolidation under pressure within the female tooling.

[0005] It is common practice to have a preform perimeter slightly smaller than that of the female tooling shape to ensure that the fibers are properly tensioned. Some layers of the preform experience an increase in perimeter during the machining process. However, the use of so-called technical fibers such as glass, carbon, or Kevlar fibers does not have the mechanical properties to allow for such elongation under tension.

[0006] The present invention aims to propose a method for manufacturing a complex-shaped 3D composite element that can be hollow or tubular but also include a non-developable surface such as a hemisphere coming out of a plane.

[0007] The present invention makes it possible in particular to produce industrially and for large series, more complex geometries than are possible with state-of-the-art technologies and / or to optimize the mechanical properties of the composite elements thus obtained.

[0008] The invention relates to a method for manufacturing a 3D composite element comprising the following steps: - Implementation of at least one discontinuous ribbon comprising long fibers oriented along the longitudinal axis of said discontinuous ribbon and composed of segments, at minus a segment comprising a release zone to another adjacent segment, - Manufacturing a preform comprising at least one discontinuous ribbon, - Activation of the release zone(s), and - Obtaining the 3D composite element.

[0009] The implementation of at least one discontinuous ribbon composed of segments and one or more release zones to constitute the preform makes it possible in particular to guarantee a flexibility between the value of the perimeter of a complex shape of the preform and the value of the perimeter of the finished 3D composite element after the activation of the release zone(s).

[0010] According to the invention, at least one discontinuous ribbon is deposited to form the preform, and at least one release zone is left intact for the preform. The activation step of at least one release zone is a controlled step that allows the desired 3D composite element to be obtained. The activation step of at least one release zone includes control of the temperature and / or pressure and / or any mechanical tensile force on the discontinuous ribbon and / or a predetermined electrical current.

[0011] According to one feature of the invention, the discontinuous tape comprises long fibers oriented along its longitudinal axis. Positioning long fibers along the direction of the discontinuous tape facilitates the release of the segments, which are linked by at least one attachment point, as the segments are stressed in a direction substantially parallel to that of their constituent fibers. The use of carbon, glass, Kevlar, aramid / para-aramid, or flax fibers, for example, makes it possible to obtain a 3D composite element with very good mechanical strength.

[0012] Different embodiments of the activation step, with at least one release zone, allow for obtaining different final shapes for the 3D composite element; examples are described below. Furthermore, a discontinuous ribbon according to the invention can be used to manufacture different preform shapes. Thus, advantageously, the same discontinuous ribbon according to the invention can be used to manufacture various shapes of 3D composite elements.

[0013] In the context of the invention, a discontinuous ribbon composed of segments comprises discontinuous fibers. According to one embodiment, no fiber has a length greater than that of the segment(s). According to another embodiment of In realization, no fiber has a length greater in any direction than a length on the order of that of the segment(s).

[0014] According to one embodiment of the invention, a release zone comprises an overlap portion to another segment, the segments being linked two by two on their overlap portion by at least one attachment point, and the activation of the release zone comprises the release of at least one attachment point.

[0015] The implementation of segments linked in pairs on their overlapping part by at least one attachment point allows, on the one hand, the design of a discontinuous ribbon ready for use to manufacture the preform, on the other hand, the ability to reuse offcuts of segments obtained in the context of other manufacturing processes, and finally, the anticipation of the place of release of the attachment point(s) to transform the preform into the 3D composite element.

[0016] In addition, the attachment point helps to stabilize the overlap, the folding according to the shape of the discontinuous tape.

[0017] According to another embodiment of the invention, a release zone comprises two folds of the discontinuous tape, the folds being held by at least one attachment point, and the activation of the release zone comprises the release of at least one attachment point.

[0018] According to one feature of the invention, the release of at least one attachment point occurs under at least one predetermined condition, such as a certain temperature, pressure, mechanical tensile force on the discontinuous tape, or a predetermined electrical current. Controlling the environment that allows the release of the attachment points makes it possible to predict the final shape of the 3D composite element.

[0019] According to one embodiment of the invention, the segments comprise a thermoplastic or natural material such as cellulose, and the attachment points are formed by ultrasonic welding. The use of ultrasonic welding makes it possible to design a tape capable of easily releasing at each weld point during its transformation into a 3D composite element. Advantageously, this type of ultrasonic welding is highly compatible with the use of thermoplastic materials.

[0020] According to yet another embodiment of the invention, a release zone comprises at least two partial cutouts the width of the discontinuous tape, the cutouts being spaced along the longitudinal direction of the discontinuous tape. Such The spacing allows for continuity of the ribbon while ensuring that no fiber within the ribbon is continuous.

[0021] A release zone includes a ribbon cutting zone, the discontinuous ribbon comprising longitudinal unidirectional fibers, the discontinuous ribbon being cut at different places so that all the fibers are cut, making the ribbon discontinuous.

[0022] According to one embodiment, the fibers of the discontinuous tape are all discontinuous but the matrix binding the fibers is continuous, thus ensuring continuity of the discontinuous tape until the activation of the release zone(s), for example by an increase in temperature causing the matrix to melt.

[0023] According to one feature of the invention, at least one cut includes a cutting angle a between -90° and +90°, the value 0° being excluded, the cutting angle a being defined with respect to the longitudinal direction of the discontinuous strip corresponding to 0°.

[0024] Advantageously, the discontinuous tape according to the invention can be used on either side. The discontinuous tape can also be reversed.

[0025] According to another feature of the invention, the cutting step is done using a laser.

[0026] According to one embodiment of the invention, the preform comprises several layers capable of forming the preform, at least one layer comprising at least one discontinuous ribbon.

[0027] According to another embodiment of the invention, the preform comprises at least one longitudinal hollow part formed by at least one layer comprising a discontinuous ribbon, the discontinuous ribbon having a dispensing angle P between -90° and 90°, a dispensing angle of 0° corresponding to a dispensing parallel to the longitudinal direction of the preform, and a dispensing angle of 90° corresponding to a dispensing perpendicular to the longitudinal direction of the preform. Manufacturing the preform using a longitudinal guide comprising a substantially circular, polygonal, or freeform variable cross-section allows the final shape of the desired 3D composite element to be anticipated.

[0028] For manufacturing processes of hollow and tubular composite parts including a step of transforming a preform by internal pressure in a female tooling, the diameter of the preform is thus adapted to the diameter of the tooling. female during the internal pressure transformation step without risking damage to the discontinuous ribbon fibers of the preform or failing to conform the preform to the female tooling.

[0029] According to one embodiment, the preform comprises several layers of ribbon and at least one layer comprises a discontinuous ribbon as defined in the invention.

[0030] According to some embodiments of the manufacturing process, the preform includes layers of ribbon that are not intended for release. For example, depositing a layer of ribbon along a longitudinal direction onto the hollow, tubular preform is not problematic for a processing step that increases the diameter of the preform. Such a layer deposited at 0° may include a discontinuous ribbon, but activating the release zone(s) is not necessary to obtain the 3D composite element according to the invention.

[0031] In certain embodiments of a 3D composite element, the preform must include a release zone at one or more specific locations. Each singularity is thus anticipated by placing a release zone that allows the preform to deform at these specific points. The more complex the desired 3D composite element's shape, the more layers the corresponding preform comprises, including discontinuous ribbons as defined in the invention, in order to align each release zone with a singularity between the preform and the desired 3D composite element.

[0032] According to one feature of the invention, the length of the segments of each layer is chosen based on the layer's deposition angle and the chosen perimeter variation between said preform layer and the same layer of the 3D composite element. These angle and perimeter variation parameters can vary along the part, as can the associated segment length parameters between said preform layer and the same layer after consolidation in a tool.

[0033] According to one feature of the invention, a layer comprises several discontinuous ribbons, each discontinuous ribbon of the same layer having the same deposition angle p. This angle can thus evolve along the preform, but the ribbons constituting the same layer have, locally, the same angle.

[0034] According to another feature of the invention, the length of the segments of each discontinuous strip is chosen according to the deposition angle P of the corresponding layer as well as according to the chosen perimeter variation between said layer and the preform and the same layer of the 3D composite element. These angle and perimeter variation parameters can vary along the part, as can the associated segment length parameters between said preform layer and the same layer after consolidation in a tool.

[0035] According to one embodiment of the invention, the activation step of the release zone(s) includes a thermal shaping step under pressure. Under certain material usage conditions, the thermal shaping step under pressure includes temperature and pressure parameters suitable for activating the release zone(s). Advantageously, the thermal shaping step under pressure is a preform consolidation step or even a transformation step of the preform into the desired 3D composite element.

[0036] According to another embodiment of the invention, the activation step of the preform's release zone(s) includes a preform drawing or stamping step. Under certain material usage conditions, the drawing step includes temperature and pressure parameters suitable for activating the release zone(s). Advantageously, the stamping step is a preform consolidation step or even a transformation step of the preform into the desired 3D composite element.

[0037] Of course, the different features, variants and embodiments of the invention can be combined with each other in various ways as long as they are not incompatible or mutually exclusive.

[0038] Furthermore, various other features of the invention become apparent from the attached description made with reference to the drawings which illustrate non-limiting embodiments of the invention and where:

[0039] [Fig. 1] is a flat view of a first example of a discontinuous ribbon according to the invention,

[0040] [Fig.2] is a perspective view of the discontinuous ribbon in Figure 1,

[0041] [Fig.3] is a perspective view of an example of the realization of a layer of a preform comprising two discontinuous ribbons of figure 1,

[0042] [Fig.4] is a perspective view after the activation step of the release zones of the discontinuous ribbon segments of the preform layer of Figure 3,

[0043] [Fig. 5] is a flat view of a second example of an embodiment of a discontinuous ribbon according to the invention,

[0044] [Fig.6] is a flat view after the activation step of the release zone of the discontinuous ribbon segments of figure 5,

[0045] [Fig. 7] is a perspective view of an example of the realization of a layer of a preform comprising two discontinuous ribbons of figure 5,

[0046] [Fig.8] is a perspective view after the activation step of the release zones of the discontinuous ribbon segments of the preform layer of Figure 7,

[0047] [Fig.9] is a perspective view of another example of the realization of a preform comprising discontinuous ribbons of figure 5 with only one discontinuous ribbon shown,

[0048] [Fig.10] is a perspective view of the activation of the release zones of two segments of the discontinuous ribbon represented in the preform of Figure 9,

[0049] [Fig.11] is a perspective view of a third example of an embodiment of a discontinuous ribbon according to the invention,

[0050] [Fig.12] is a flat view after the activation step of the release zone of the discontinuous ribbon segments of figure 11,

[0051] [Fig. 13] is a perspective view of an example of the realization of a layer of a preform comprising two discontinuous ribbons of Figure 11, and

[0052] [Fig.14] is a perspective view after the activation step of the release zones of the discontinuous ribbon segments of the preform layer of Figure 13.

[0053] It should be noted that in these figures the structural and / or functional elements common to the different variants may have the same references.

[0054] The invention aims to provide a method for manufacturing a 3D composite element from at least one discontinuous strip.

[0055] For these purposes, a first step in the manufacturing process of a 3D composite element according to the invention therefore consists of implementing a discontinuous ribbon designated by reference 1 as illustrated in figures 1 and 2.

[0056] In the context of the invention, a discontinuous ribbon 1 is defined before its shaping.

[0057] A ribbon comprising longitudinal fibers is a discontinuous ribbon 1 if there are two adjacent segments of said ribbon for which the fibers are no longer continuous or if it there exists a segment of said ribbon for which the fibers are no longer arranged in a single direction, the shape of the segment being free.

[0058] According to the embodiment examples described below, the fibers of a discontinuous ribbon 1 are cut or folded, the folding embodiment example imposing a different direction of fibers.

[0059] Thus, a ribbon is considered a discontinuous ribbon 1 if there is no path parallel to one of its edges not crossing a discontinuity such as a fold on itself, an overlap or a cut.

[0060] The manufacturing process according to the invention makes it possible to design a 3D composite element 2 from a discontinuous ribbon 1.

[0061] A discontinuous tape 1 comprises fibers oriented along the axis of the discontinuous tape 1. The discontinuous tape 1 may, for example, comprise unidirectional fibers of carbon, glass, Kevlar, aramid / para-aramid, or flax, embedded in a matrix. In various embodiments, the matrix may comprise a thermoplastic, metallic, or thermosetting material. In other embodiments, the discontinuous tape 1 may comprise a natural material such as cellulose or natural fibers bonded directly to one another.

[0062] Three embodiments of a discontinuous ribbon 1 for the manufacturing process according to the invention are described below. Other embodiments of a discontinuous ribbon 1 compatible with the invention are possible. A discontinuous ribbon 1 compatible with the invention comprises at least two segments 3, with at least one segment 3 comprising a release zone 4 to another adjacent segment 3.

[0063] According to a first embodiment illustrated in particular in figures 1 and 2, the discontinuous ribbon 1 comprises several segments 3, one segment 3 comprising an overlap part 5 on another adjacent segment 3.

[0064] Each segment 3 situated between two segments 3 then comprises an overlapping portion 5 and a portion covered by an overlapping portion 5 of the adjacent segment 3. Such a segment 3 therefore comprises two release zones 4 with two segments 3 located on either side.

[0065] According to this first form of realization of a discontinuous ribbon 1, the release zone 4 includes the part of an overlap 5 of one segment 3 to another segment 3.

[0066] For a discontinuous ribbon 1, the length S of a segment 3 corresponds to the distance between two consecutive overlapping portions 5, the two overlapping portions 5 being inclusive. The length Z of the release zone 4 corresponds to the length of the overlapping portion 5, i.e., the length of the overlap of the two segments 3 along the longitudinal direction of the discontinuous ribbon 1.

[0067] For example, for a discontinuous ribbon 1 whose width is between 5 and 15 mm, the length Z of an overlap part 5 of one segment 3 on the other segment 3 is between 1 and 7 mm, preferably between 4 and 6 mm, preferably 5 mm.

[0068] More generally, an overlap portion 5 corresponds approximately to half the width of the discontinuous strip 1 while maintaining a value greater than 1 mm. The maximum value depends on the amount of length that will be consumed during the manufacturing process according to the invention, that is to say, according to the geometric complexity of the desired 3D composite element 2.

[0069] According to this embodiment example, the retention of the overlapping part 5 of one segment 3 to another segment 3 is guaranteed by means of at least one attachment point.

[0070] According to one embodiment of the process, and in particular for a discontinuous tape 1 comprising a thermoplastic matrix or comprising a natural material such as cellulose or even directly natural fibers welded together, the attachment points are created by ultrasonic welding.

[0071] According to other embodiments of the process, the attachment points may also include points of glue or other resins to ensure that the covering part 5 of one segment 3 is held to another segment 3.

[0072] According to a second step of the process according to the invention, a preform 7 is manufactured from at least one discontinuous ribbon 1. Different examples of preform 7 are described below.

[0073] The third step of the manufacturing process according to the invention includes an activation step of the release zone 4.

[0074] According to some embodiments, the activation step of the release zone 4 is controlled by providing one or more predetermined conditions, such as a certain temperature, pressure or any mechanical tensile force on the discontinuous tape 1 or even a predetermined electrical intensity.

[0075] According to the embodiment of a discontinuous ribbon 1 illustrated in Figures 1 and 2, the activation step of the release zone 4 partially enables the separation of two consecutive segments 3. The separation distance can be anticipated during the transformation of the preform 7 into the 3D composite element 2 by controlling the activation of the release zones 4.

[0076] Figure 3 illustrates a layer of a cylindrical preform 7 comprising two discontinuous strips 1, as defined in Figures 1 and 2, arranged parallel to each other and deposited with a gap between them. One or more such layers can thus constitute a preform 7 forming a hollow longitudinal part. According to other layer embodiments of a preform 7, the discontinuous strip(s) 1 are deposited in contact with each other, i.e., without a gap.

[0077] According to one embodiment of a cylindrical preform 7, the discontinuous strip(s) 1 are deposited onto a support or dispensing mandrel (not shown). This support or dispensing mandrel can be removed once the preform 7 is ready, used for a transformation step into the 3D composite element and subsequently removed, or it can form part of the resulting 3D composite element 2.

[0078] According to the embodiment illustrated in Figure 3, the two discontinuous ribbons 1 are deposited parallel to each other and along a deposit direction D forming a deposit angle P of approximately 55° with respect to the longitudinal direction X of the cylindrical preform 7.

[0079] According to an embodiment not shown, the preform 7 comprises several layers of discontinuous tape 1, each layer having a specific deposition angle for the respective discontinuous tape(s) 1, different from the immediately superior and / or inferior layer. For example, a first layer is deposited at 0°, two layers are deposited at angles of -30° and 30°, and a fourth layer is deposited at 85°. Depending on the complexity of the preform 7 and the singularity points between the preform 7 and the resulting 3D composite element 2, not all of the release zones 4 are activated.

[0080] To produce a preform 7 comprising an evolving cylindrical shape (not illustrated), that is to say comprising different diameters, several longitudinal pieces are implemented consecutively, the same discontinuous strip 1 being able to form at least in part a first longitudinal piece with a first diameter and at least in part a second longitudinal piece with a second diameter of a different value. first diameter. Several discontinuous ribbons 1 can also be implemented to design a preform 7 with at least one change in diameter size.

[0081] Figure 4 illustrates the activation of the release zones 4 of the two discontinuous ribbons 1 implemented in order to obtain at least in part the final shape of the desired 3D composite element 2, namely a cylindrical shape comprising a diameter greater than the diameter of the cylindrical shape of the preform layer 7 of Figure 3.

[0082] A second embodiment of a discontinuous ribbon 1 compatible with the invention is illustrated in figures 5 and 6.

[0083] According to this illustrated embodiment, the discontinuous ribbon 1 includes a release zone 4 formed by five cutouts 8.

[0084] The five cutouts 8 are all parallel to each other. Three cutouts 8 are along a first line Y1 and two other cutouts 8 are along a second line Y2 parallel to the first line Y1. This particular architecture forms a crenellated release zone 4.

[0085] According to this second example of realization, the length S of a segment 3 corresponds to a new iteration of a similar cut 8, that is to say the same cut 8 of the diagram and located at the next longitudinal coordinate along the longitudinal direction of the discontinuous ribbon 1. And, the length Z of the release zone 4 corresponds to the distance between the first line Y1 and the second line Y2 defined along the longitudinal direction of the discontinuous ribbon 1.

[0086] According to the embodiment illustrated in figures 5 and 6, the lines Y1,Y2 include a cutting angle α approximately equal to 15° with respect to the longitudinal direction of the discontinuous strip 1.

[0087] This cutting creation step 8 can be done using a laser or other precision cutting tools.

[0088] Figure 6 illustrates the activation of the release zone 4, the spaced cuts 8 created a crenellated structure between two consecutive segments 3.

[0089] According to one embodiment of a discontinuous ribbon 1 comprising a matrix capable of being softened under certain conditions, such as a metallic, thermoplastic, or thermosetting material, the activation step of the release zone 4 comprises an increase in temperature resulting in at least softening, if not the melting of the matrix leading to the slippage of the fibers and the opening into notches of the release zone 4.

[0090] According to another embodiment of a discontinuous ribbon 1 comprising a matrix less suitable for being softened, the activation step of the release zone 4 includes a tensioning causing the matrix to tear and the release zone 4 to open in notches.

[0091] A control of the activation of the release zone 4 allows you to choose the desired distance of separation between two segments 3.

[0092] For this form of realization of a discontinuous ribbon 1 comprising at least two cuts 8, many schemes are possible.

[0093] Two cuts 8 spaced at a distance Z which ensure a discontinuity of the longitudinal fibers of a segment 3 of a discontinuous ribbon 1 are necessary to form a release zone 4 according to the invention.

[0094] According to an embodiment of the discontinuous ribbon 1 comprising a width of at most 100mm, the distance Z is at most 100mm, preferably less than 25mm and even more preferably less than 10mm.

[0095] According to one embodiment of the discontinuous ribbon 1, the length of a cut 8 is at least 0.5mm

[0096] According to one embodiment of the discontinuous ribbon 1, the length of a cut 8 is at most one quarter of the width of the discontinuous ribbon 1 and preferably one eighth of the width of the discontinuous ribbon 1, the summed lengths of all the cuts 8 of a release zone Z being at least the width of the discontinuous ribbon 1.

[0097] The number of cuts 8, their spacing, their widths, the cutting angles a can thus vary according to the materials used but also in anticipation of the activation of the release zone of the preform 7 created from such a discontinuous ribbon 1.

[0098] For example, to form a layer of a cylindrical preform 7 as shown in Figure 7, two identical discontinuous strips 1, comprising release zones 4 formed by cuts 8 at an angle α, are deposited parallel to each other at a deposition angle P, for example on a cylindrical support. illustrated. Such a cutting angle a is chosen according to the deposition angle P of the discontinuous ribbon 1 to form at least in part the cylindrical preform 7.

[0099] According to the example illustrated in Figures 7 and 8, the cutting angle a is approximately 15° and the insertion angle P is approximately 55°. In this embodiment, the cuts 8 are located in a position approximately perpendicular to the longitudinal direction of the cylindrical preform 7.

[0100] To achieve this preferred position, the cutting angle a and the depositing angle P are interdependent.

[0101] If the value of the dispensing angle P approaches 0°, i.e. for dispensing along the longitudinal direction of the mandrel, the value of the cutting angle a must approach 0° to allow an effective release zone 4, namely to allow an increase in the diameter of the cylindrical preform 7 associated with a longitudinal elongation of said cylindrical preform 7.

[0102] If the cutting angle a approaches approximately 90° (is greater than 45°), the associated discontinuous strip 1 must be laid with a laying angle P preferably greater than 45° and even more preferably greater than 80°. Thus, the position of the cutting lines 8 on the preform 7 approaches the perpendicular to the support or laying mandrel.

[0103] According to one embodiment of the preform 7 implementation step, the length S of a segment 3 of a discontinuous strip 1 is chosen as a function of the width of the discontinuous strip 1 and the deposition angle P to form the cylindrical preform 7. According to one embodiment of a discontinuous strip 1 having a width between 5 and 15 mm, the length S is at most equal to five times, preferably 2.5 times, and at least one times the value of the helicoid of revolution of the cylindrical preform 7, the value of the helicoid depending on the diameter of the cylindrical preform 7 as well as the deposition angle p.

[0104] The embodiments described for the first example of making a layer of a preform 7 from at least one discontinuous strip 1 as shown in Figures 1 and 2 are compatible with the embodiment of a layer of a preform 7 illustrated in Figure 7.

[0105] Figure 8 illustrates the activation of the relaxation zones 4 of the layer of the cylindrical preform 7 of figure 7.

[0106] Figure 9 illustrates another example of a flat preform 7 formed from several discontinuous strips 1 comprising cutouts 8 as illustrated in Figure 5 and deposited parallel to each other. Only one discontinuous strip 1 appears in Figure 9 for better visibility. According to other embodiments, several layers of discontinuous strips 1 can be deposited to form the flat preform 7, each layer being oriented at its own specific deposition angle in the plane.

[0107] Figure 10 illustrates the activation of the release zone 4 shown in Figure 9. According to other embodiments not shown, the third step of the manufacturing process according to the invention allows the activation of all the release zones 4 of each of the discontinuous ribbons 1 forming the flat preform 7.

[0108] According to this embodiment of the manufacturing process, the activation of the release zones 4 occurs during a stamping step that defines such a hemispherical relief. The predetermined pressure and temperature of the stamping process control the activation of the release zones 4. The flat preform 7 is thus deformed to obtain this hemispherical shape, and the release zones allow the material formed by at least one layer of discontinuous strips 1 to spread evenly without creating lumps of material, thus ensuring a uniform surface finish.

[0109] The final step in the process consists of obtaining the 3D composite element thus formed.

[0110] According to a third embodiment illustrated in figure 11, the discontinuous ribbon 1 includes a release zone 4 formed by two folds 9,10. A first fold 9 at 180° is followed by a second fold 10 at 180° along the longitudinal direction of the discontinuous ribbon 1.

[0111] The length S of a segment 3 corresponds to a new iteration of a first fold 9 following and the length Z of the relaxation zone 4 corresponds to the distance between the two folds 9,10 along the longitudinal direction of the discontinuous ribbon 1.

[0112] For example, for a discontinuous ribbon 1 whose width is approximately between 5 and 15 mm, the length Z of the release zone 4 from one segment 3 to the other segment 3 is between 1 and 7 mm, preferably between 4 and 6 mm, preferably 5 mm. According to this embodiment with two folds, the maximum release length therefore corresponds to twice the value of the length Z of the release zone.

[0113] A segment 3 comprises two consecutive folds 9,10 which are reversibly held together by at least one attachment point per fold 9,10. Different processes are compatible depending on the materials used in a similar manner to the first form of realization of a discontinuous ribbon 1 by overlap.

[0114] According to one embodiment of the process, and in particular for a discontinuous ribbon 1 comprising a thermoplastic matrix, the attachment points can be created by ultrasonic welding.

[0115] According to another embodiment of the process, the attachment points may also include points of glue or other resins allowing the two folds 9,10 of a segment 3 to be held together.

[0116] Figure 13 illustrates a layer of a cylindrical preform 7 comprising two discontinuous strips 1, as defined in Figures 11 and 12, arranged parallel to each other and deposited with a gap between them. One or more such layers can thus constitute a preform 7 forming a hollow longitudinal part. According to other layer embodiments of a preform 7, the discontinuous strip(s) 1 are deposited in contact with each other, i.e., without a gap.

[0117] The embodiments described for the first example of making a layer of a preform 7 from at least one discontinuous strip 1 as shown in Figures 1 and 2 are compatible with the embodiment of a layer of a preform 7 illustrated in Figure 13.

[0118] Figure 14 illustrates the activation of the release zones 4 of the two discontinuous ribbons 1 implemented in order to obtain at least in part the final shape of the desired 3D composite element 2, namely a cylindrical shape comprising a diameter greater than the diameter of the cylindrical shape of the preform layer 7 of Figure 13.

[0119] Of course, various other modifications can be made to the invention within the scope of the attached claims.

Claims

Demands

1. A method for manufacturing a 3D composite element (2) comprising the following steps: - Implementation of at least one discontinuous tape (1) comprising long fibers oriented along the longitudinal axis of said discontinuous tape (1) and composed of segments (3), at least one segment (3) comprising a release zone (4) to another adjacent segment (3), - Manufacture of a preform (7) comprising at least one discontinuous ribbon (1), - Activation of the release zone(s) (4), and - Obtaining the 3D composite element (2).

2. A manufacturing method according to the preceding claim in which a release zone (4) comprises an overlap portion (5) to another segment (3), the segments (3) being linked two by two on their overlap portion (5) by at least one attachment point, and the activation step of the release zone (4) comprises the release of at least one attachment point.

3. A manufacturing method according to the preceding claim wherein a release zone (4) comprises two folds (9,10) of the discontinuous tape (1), the folds (9,10) being held by at least one attachment point, and the activation of the release zone (4) comprises the release of the attachment point(s).

4. A manufacturing method according to any one of claims 2 or 3 wherein the release of at least one attachment point is carried out according to at least one predetermined condition, such as a certain temperature, pressure or any mechanical tensile force on the discontinuous tape (1) or a predetermined electrical intensity.

5. A manufacturing method according to any one of claims 2 to 4 wherein the segments (3) comprise a thermoplastic or natural material such as cellulose and the attachment points are made by ultrasonic welding.

6. A manufacturing method according to claim 1 wherein a release zone (4) comprises at least two partial cuts (8) in a direction not parallel to the longitudinal direction of the discontinuous tape (1), the cuts (8) being spaced along the longitudinal direction of the discontinuous tape (1).

7. A manufacturing method according to the preceding claim, wherein at least one cut (8) comprises a cutting angle (a) between -90° and +90°, the value -0° being excluded, the cutting angle (a) being defined with respect to the longitudinal direction of the discontinuous strip (1) corresponding to 0°.

8. A manufacturing method according to any one of claims 6 or 7 wherein the cutting step is carried out using a laser.

9. A manufacturing method according to any one of the preceding claims wherein the preform (7) comprises at least one layer suitable for forming the preform (7), at least one layer comprising at least one discontinuous ribbon (1).

10. A manufacturing method according to any one of the preceding claims wherein the preform (7) comprises at least one longitudinal hollow part formed by at least one layer comprising a discontinuous ribbon (1), the discontinuous ribbon (1) comprising a deposition angle (P) between 0 and ±90°, a deposition angle (P) of 0° corresponds to a deposition in the longitudinal direction (X) of the preform (7) and a deposition angle (P) of 90° corresponds to a deposition perpendicular to the longitudinal direction (X) of the preform (7).

11. A manufacturing method according to the preceding claim in which the length of the segments (3) of each layer is chosen as a function of the deposition angle (P) of the layer as well as as a function of the chosen perimeter variation between said layer of the preform (7) and the same layer of the 3D composite element (2).

12. A manufacturing method according to any one of claims 10 or 11 wherein a layer comprises several discontinuous ribbons (1), each discontinuous ribbon (1) of the same layer comprising the same deposition angle (P).

13. A manufacturing method according to any one of claims 10 to 12 wherein the length of the segments (3) of each discontinuous strip (1) is chosen as a function of the deposition angle (P) of the corresponding layer as well as as a function of the chosen perimeter variation between said layer of the preform and the same layer of the 3D composite element.

14. A manufacturing method according to any one of the preceding claims wherein the step of activating the release zone(s) (4) includes a step of thermal conforming under pressure.

15. A manufacturing method according to the preceding claim in which the activation step of the release zone(s) (4) of the preform (7) includes a stamping step of the preform (7).

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