EP3372718A1 - Method for manufacturing a needled fibrous structure - Google Patents

Abstract

The invention relates to a method of manufacturing a needled fibrous structure using a needling machine (100) provided with a needling head (110), the method comprising at least the following steps: placing a first fibrous layer (10) on a support (120); needling the first layer, the needling head being in a first position relative to the support; relative movement of the support relative to the needling head, made after needling the first layer, so as to pass the needling head in a second position, different from the first, relative to the support; placing a second fibrous layer (20) on the first layer; and the needling of the second fibrous layer placed on the first layer, the needling head being in the second position relative to the support at the beginning of the needling of the second layer.

Description

Background of the invention

The present invention relates to the general field of processes for manufacturing needled fibrous structures, which can be used for the manufacture of parts made of composite material.

Several types of needling machines are known that can be used to produce needle-punched textile structures. In a first plane-type machine, needling fibrous layers stacked on a table, the table moving in horizontal translation in front of a vertically movable needling head. In a second machine of the circular type, the needling is made of a continuous fibrous layer wound around a rotating mandrel. The mandrel has a surface of revolution around which the layer is wound, the layer being located in front of a needling head movable in a direction perpendicular to this surface.

By using one or the other of these machines to needle several superimposed fibrous layers, it is observed that the fibrous structures obtained obtained have areas of weakness. These areas of weakness are mainly due to recurrent needling on the same area between two consecutive fibrous layers. In particular, when the needling head moves along the fibrous layer to needling (for example by translation of the table or rotation of the mandrel), the successive passages of the head between two layers can produce holes aligned in the direction scrolling of the layer (phenomenon called "lineage"). These alignments of holes within the same layer and between the different layers can lead to premature failure of the fibrous structure needled along these lines of holes. As a result, it is observed that the composite material parts resulting from the densification of these fibrous needled structures are also subject to mechanical strength problems, which is undesirable.

There is therefore a need for a method of manufacturing a needle-punched textile structure on a planar or circular needling machine, which does not have the aforementioned drawbacks.

Object and summary of the invention

• le placement d'une première couche fibreuse sur un support,
• l'aiguilletage de la première couche fibreuse, la tête d'aiguilletage étant dans une première position par rapport au support au moins à la fin de l'aiguilletage de la première couche,
• le déplacement relatif du support par rapport à la tête d'aiguilletage, réalisé après l'aiguilletage de la première couche, de façon à faire passer la tête d'aiguilletage de la première position à une deuxième position, différente de la première, par rapport au support,
• le placement d'une deuxième couche fibreuse sur la première couche fibreuse aiguilletée, et
• l'aiguilletage de la deuxième couche fibreuse placée sur la première couche fibreuse, la tête d'aiguilletage étant dans la deuxième position par rapport au support au moins au début de l'aiguilletage de la deuxième couche fibreuse.

The main object of the present invention is therefore to overcome such drawbacks by proposing a process for manufacturing a needled fibrous structure using a needling machine equipped with a needling head, the process comprising at least one the following steps:

• placing a first fibrous layer on a support,
• needling the first fibrous layer, the needling head being in a first position relative to the support at least at the end of the needling of the first layer,
• the relative displacement of the support with respect to the needling head, made after the needling of the first layer, so as to pass the needling head of the first position to a second position, different from the first, relative to the support,
• placing a second fibrous layer on the first needled fibrous layer, and
• the needling of the second fibrous layer placed on the first fibrous layer, the needling head being in the second position relative to the support at least at the beginning of the needling of the second fibrous layer.

The process according to the invention makes it possible to reduce the risk that needles of the needling head may need to point twice the same place between two successive fibrous layers. Indeed, the step of relative displacement of the support relative to the needling head, corresponding to a relative offset of these elements relative to each other, prevents the needles hit globally to the same place between two successive layers. In particular, the method according to the invention makes it possible to prevent the formation of needled hole lines ("lineage" phenomenon) between two successive layers and to reduce the problems of fragility caused by them. The composite material parts resulting from the subsequent densification of a needled fibrous structure obtained by a method according to the invention thus have improved mechanical strength.

The support may be a rotary table or mandrel about an axis of rotation. When the support is a table, the needling head may, during a needling step, move in translation perpendicular to the surface of the table with a vertical movement alternative. In addition, the table can move in translation in front of the needling head to needle a fibrous layer of larger size than that of the needling head. When the support is a rotating mandrel, the needling head may, during a needling step, move perpendicularly to the surface of the mandrel with a vertical reciprocating movement, that is to say in a radial direction by relative to the axis of rotation of the mandrel.

In the following exemplary embodiments, the support may advantageously be a table, mobile or otherwise in translation in front of the needling head.

In an exemplary embodiment, the relative displacement of the support relative to the needling head may comprise a relative rotation of the support relative to the needling head.

In particular, the relative rotation of the support relative to the needling head may be a rotation of the support along an axis perpendicular to a surface of the support.

In an exemplary embodiment, the support can rotate at a non-zero angle less than or equal to 5 °, for example less than or equal to 2 °. A range of angles reduced in this way avoids the presence of so-called "dead zones" where the fibrous layers are not needled.

In the following exemplary embodiments, the support may advantageously be a mandrel rotating around an axis of rotation and on which a fibrous structure may be wound, a layer of fibrous structure for example making a turn around the mandrel.

In an exemplary embodiment, the relative displacement of the support relative to the needling head may comprise a relative translation of the support relative to the needling head.

In particular, the support of the needling machine may be rotatable about an axis of rotation, the relative displacement of the support relative to the needling head then being a relative translation of the needling head relative to the support in a direction parallel to the axis of rotation of the support.

In an exemplary embodiment, the needling head or the support can be translated from a non-zero distance of less than or equal to 30 mm, for example less than or equal to 15 mm, in particular to reduce the presence of dead zones in needled layers.

• la fabrication d'une structure fibreuse aiguilletée destinée à former le renfort fibreux de la pièce par un procédé tel que celui décrit précédemment, et
• la formation d'une matrice dans la porosité de la structure fibreuse aiguilletée de façon à obtenir la pièce en matériau composite.

The invention also aims, according to another aspect, a method of manufacturing a composite material part comprising a fiber reinforcement densified by a matrix, the method comprising at least the following steps:

• the manufacture of a fibrous needled structure intended to form the fibrous reinforcement of the part by a process such as that described above, and
• the formation of a matrix in the porosity of the fibrous structure needled to obtain the composite material part.

Brief description of the drawings

• les figures 1A à 3B illustrent les étapes d'un procédé selon un premier mode de réalisation de l'invention, mettant en oeuvre une machine d'aiguilletage du type plan, et
• les figures 4A à 5B illustrent les étapes d'un procédé selon un deuxième mode de réalisation de l'invention, mettant en oeuvre une machine d'aiguilletage du type plan.

Other features and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate an embodiment having no limiting character. In the figures:

• the Figures 1A to 3B illustrate the steps of a method according to a first embodiment of the invention, implementing a needling machine of the planar type, and
• the Figures 4A to 5B illustrate the steps of a method according to a second embodiment of the invention, implementing a needling machine of the planar type.

Detailed description of the invention

The Figures 1A to 3B illustrate the steps of a method according to a first embodiment of the invention. In this example, a plane-type needling machine 100 is used which comprises a needling head 110 and a support constituted by a table 120. The needling head 110 carries a determined number of needles 111 which are provided with barbs, hooks or forks to take fibers from the fibrous layers and transfer them through them as they penetrate them. In a manner known per se, these needles 111 can be arranged in several rows of needles 111. The needling head 110 can move vertically, that is to say in the direction Z indicated in the figures, above of the table 120. The needling head 110 can in particular move up and down and upwards in the vertical direction Z with a vertical reciprocating movement relative to the table 120, as illustrated by the double arrow 112. The table 120 extends in turn in horizontal directions X and Y perpendicular to the direction Z. The table 120 is here mounted on a pole 130 movable in translation in a rail 140 extending along the direction X, so that the table 120 can be moved in rectilinear translation according to the X direction in front of the needling head 110 (double arrow 131). In the example illustrated, the needling head 110 can not move in the X and Y directions. In the example illustrated, the table 120 is rotatable about an axis A, parallel to the axis Z, and perpendicular to the surface 121 of the table on which the needling fibrous layers will be made. Note that, in an equivalent variant not shown, the table 120 may be fixed in the X direction, while the needling head 110 may be movable in translation in the X direction.

On the Figure 1A a first fibrous layer 10 is disposed and held on the table 120. The fibrous layer 10 has been needled by the needling head 110, for example by making a round trip to the needling head 110 by moving the table 120 in the rail 140. During the needling, and in a well known manner, the needling head 110 is driven in a movement along the double arrow 112. The needles 111 then enter the fibrous layer or layers present on the table for fibers interpenetrating the different fibrous layers in the direction Z. The displacement of the table 120 in front of the head 110 may, during the needling, be carried out step by step, that is to say with an alternation of phases of displacement and stopping phases, the needling being performed by the head 120 during the stopping phases. This advantageously makes it possible to reduce the shearing of the fibrous layer during needling and to further improve the mechanical properties of the part.

The Figure 1B shows a top view of the first fibrous layer 10 on the table 120, as well as holes 11 corresponding to the location where the needles are retracted into the first fibrous layer 10 during its needling. In the example illustrated, the needles 111 are distributed uniformly over a surface of the needling head 110. Following this needling step, the needling head 110 is in a first position compared to table 120, illustrated on the Figures 1A, 1B and 2 . This first position is defined here in particular by the orientation of the table 120 relative to the needling head 110.

To the figure 2 a second fibrous layer 20 is positioned on the first fibrous layer 10 which has already been needled. Here the edges of the two fibrous layers 10 and 20 are aligned on the table 120. In a variant, the second layer 20 may be arranged in a different manner on the first layer 10.

Then, as illustrated on the figure 3A a step of relative displacement of the table 120 (on which the two fibrous layers 10 and 20 are present) relative to the needling head 110 is carried out. In this example, this step corresponds to a rotation of the table 120 around its axis of rotation A of an angle a, the needling head 110 being here fixed horizontally. The angle α may be less than or equal to 5 ° (that is to say between -5 ° and 5 ° relative to the first position), or even less than or equal to 2 ° (i.e. say between -2 ° and 2 ° relative to the first position), in order to limit the size of the dead zones, that is to say not needled, in the fibrous layers. Of course, α is not equal to 0. The needling head 110 is thus in a second position, different from the first position.

After relative movement of the table 120 with respect to the needling head 110, the second fibrous layer 20 is needled, the needling head 110 being in the second position at least at the beginning of the needling of the second layer 20. The needling of the second fibrous layer 20 may be performed identically to the needling of the first fibrous layer 10. In particular the table 120 may also move in front of the needling head 110 in the X direction and can go back and forth to whet all the second layer 20.

On the figure 3B the first position of the table 120 can be seen in dotted lines, and the second position of the table 120 in a solid line. The position of the holes 11 made in the first layer 10 during the needling of the first layer is also seen. 10, and the position of the holes 21 made during the needling of the second layer 20. It is thus observed that the needles do not hit the layers 10 and 20 in the same place, which reduces the formation of areas of fragility within the resulting fibrous structure resulting in particular preventing lineage phenomenon.

The Figures 4A to 5B illustrate the steps of a method according to a second embodiment of the invention. In this example, it implements a needling machine 200 of the circular type which comprises a needling head 210 provided with needles 211 and a support here constituted by a mandrel 220 around which a fibrous structure 30 is intended to be wound . The mandrel 220 is rotatable about an axis B. The needling head 210 can move, during the needling, in a direction Z perpendicular to the surface of the mandrel, this direction also corresponding to a radial direction relative to to the axis B of the mandrel 220. In this example, the mandrel 220 is only rotatable about the axis B, and the needling head 210 is movable in translation only in the directions X and Z. The fibrous structure May be in the form of a fibrous web stored on a mandrel 230.

In the following, it is considered that when the fibrous structure 30 is wound with less than one turn on the mandrel 220, the wound portion forms a first fibrous layer 31 on the mandrel 220. When the structure 30 is wound with more than one turn and less than two turns, the portion that covers the first layer 31 forms a second fibrous layer 32 on the mandrel 220.

In known manner, to needle the first layer 31, the mandrel 220 is rotated progressively (arrow 221) to scroll the first layer 31 in front of the needling head 210. At the same time, the needling head 210 is animated a movement according to the double arrow 212 to needle the entire first layer 31. Following the needling of the first layer 31, the needling head 210 is in a first position relative to the mandrel 220 This first position is defined here in particular by the position along the axis X of the needling head 210 with respect to the mandrel 220. As in the previous example, the movement of the fibrous structure 30 in front of the needling head 210 can be achieved step by step, in particular to reduce the shearing of the fibrous layer during needling.

Similar to the previous example, the Figure 4B shows a view of the first layer 31 at the beginning of its needling and the position of the holes 31a resulting therefrom.

Then, as illustrated on the Figure 5A , the relative displacement step of the mandrel 220 (on which the two fibrous layers 31 and 32 are present) is carried out with respect to the needling head 210. In this example, this step corresponds to a translation of the head of needling 210 of a distance ΔX in the X direction parallel to the axis of rotation B of the mandrel. The distance ΔX may be less than or equal to 30 mm (that is to say that the displacement may be between -30mm and + 30mm relative to the first position), or even less than or equal to 15mm (that is, that is to say between -15mm and + 15mm relative to the first position), in order to limit the size of the dead zones, that is to say not needled, in the fibrous layers. Of course, ΔX is not equal to 0. The needling head 210 is thus in a second position, different from the first position.

After relative displacement of the mandrel 220 with respect to the needling head 210, the second fibrous layer 32 is needled, the needling head 210 being in the second position at least at the beginning of the needling of the second fibrous layer 32. The needling of the second fibrous layer 32 may be performed identically to the needling of the first fibrous layer 31. In particular the mandrel 220 can rotate around the axis B so as to scroll the second layer 32 in front of the needling head 210 which is moved back and forth in the direction Z.

On the Figure 5B the first position of the head 210 can be seen in dashed lines, and the second position of the head 210 in solid lines. The position of the holes 31a made in the first layer 31 during the needling of the first layer is also seen. 31, and the position of the holes 32a made during the needling of the second layer 32. It is thus observed that the needles do not hit the layers 31 and 32 in the same place, which reduces the formation of areas of fragility within the resulting fibrous structure resulting in particular preventing lineage phenomenon.

Examples of processes according to the invention have been described in connection with a plane-type needling machine 100 and with a Circular type needling machine 200. In one or the other of these machines 100 and 200, the steps of relative movement of the support relative to the needling head correspond to particular movements of the support or the head. , for example a translation or a rotation, particularly adapted to the machine in question. Of course, it is not beyond the scope of the present invention when the step of relative displacement of the support relative to the needling head successively comprises several types of movements, for example a translation followed by a rotation or vice versa.

A fibrous layer may for example comprise a unidirectional fiber web, or a textile web having a two-dimensional weave. The fibers of the fibrous layer may be fibers of a refractory material such as carbon, or ceramic fibers, for example silicon carbide or glass.

In addition, for reasons of simplification, the examples of processes according to the invention have been described with the needling of only two stacked fibrous layers, but it is obvious that the invention applies to the needling of a number more important fibrous layers, which can be of various shapes and sizes. Also, when we need a fibrous layer, it is usually present on another underlying fibrous layer. In the illustrated examples, the fibrous layer underlying the first layer 10 or 21 has not been shown. It should be noted that in some cases it is possible to needle a fibrous layer alone without an underlying fibrous layer being present. In the latter case, it will be possible to interpose a felt layer (not shown) between the table or mandrel and the first fibrous layer.

Moreover, when the process according to the invention is repeated, for example when a third fibrous layer is stacked on the second, then a fourth on the third, etc. it may be advantageous to choose randomly the value of the angle of rotation α or of the translation distance ΔX for each step of relative displacement of the support relative to the needling head which is performed between each needling step .

In this presentation, the expression "between ... and ..." is to be understood as including the terminals.

Claims (5)

A method of manufacturing a needled fibrous structure using a needling machine (100; 200) provided with a needling head (110; 210) comprising a plurality of needles, the method comprising at least the following steps: placing a first fibrous layer (10; 31) on a support (120; 220), - The needling of the first fibrous layer, the needling head being in a first position relative to the support at least at the end of the needling of the first layer, the relative displacement of the support with respect to the needling head, made after the needling of the first layer, so as to move the needling head from the first position to a second position, different from the first, by relation to the support, placing a second fibrous layer (20; 32) on the first needled fibrous layer, and - The needling of the second fibrous layer placed on the first fibrous layer, the needling head being in the second position relative to the support at least at the beginning of the needling of the second fibrous layer; wherein the relative displacement is configured so that the needling head needles do not strike the first (10; 31) and second (20; 32) layers at the same location, and
wherein (i) the relative displacement comprises a relative rotation of the support (120) with respect to the needling head (110), or (ii) the support (220) is a rotating mandrel and the relative displacement is a relative translation the needling head (210) relative to the support in a direction (X) parallel to an axis (B) of rotation of the support. The method of claim 1, wherein the relative rotation of the carrier (120) relative to the needling head (110) is a rotation of the carrier along an axis (A) perpendicular to a surface (121) of the carrier. The method of claim 1 or 2, wherein the support (120) rotates at a non-zero angle (α) of less than or equal to 5 °. Method according to claim 1, wherein the needling head (210) or the support (220) is translated from a non-zero distance (ΔX) of less than or equal to 30 mm. A method of manufacturing a composite material part comprising a matrix-densified fiber reinforcement, the method comprising at least the following steps: the manufacture of a fibrous needled structure intended to form the fibrous reinforcement of the part by a method according to any one of claims 1 to 4, and - The formation of a matrix in the porosity of the fibrous structure needled so as to obtain the piece of composite material.

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