A composite material part with improved shock absorption capacity, and a manufacturing process for such a part.

Abstract

Composite material part with improved shock absorption capacity, and method for manufacturing such a part. The present invention relates to a composite material part with improved shock absorption capacity, comprising a fibrous reinforcement having an evolving textile weave (1) and densified by a matrix, said evolving textile weave comprising (i) at least one structural portion (3) formed by three-dimensional weaving of first yarns (10) with second yarns (20) and in which all or part of the first yarns have a first weave, and (ii) at least one damping portion (5) in which all or part of the first yarns are separated so as to have a second weave greater than the first weave and thus to define in the part shock absorption cavities having a lack of material or filled by a shock absorption material distinct from the matrix. Figure for the abstract: Fig. 1.

Description

Title of the invention: Composite material part with improved shock absorption capacity, and method of manufacturing such a part Technical field

[0001] The present invention relates to a part made of composite material with improved shock absorption capacity defining shock absorption cavities having a lack of material or filled with a shock absorption material, as well as the manufacture of such a part implementing a spacing of reinforcement wires in order to form these cavities. Prior art

[0002] Composite material parts are increasingly used in aeronautical turbomachines with a view to lightening the structures compared to metallic materials, while guaranteeing the desired mechanical properties. As such, the aircraft fan casing can be formed by three-dimensional weaving of a strip of carbon threads which is then wound on a tool and then densified by an organic matrix. The casing must provide a retention function by retaining debris ingested inside the engine, or blades or blade fragments projected by centrifugation, in order to prevent them from passing through the casing and reaching other parts of the aircraft. Known solutions effectively address these problems but it remains possible to further improve energy absorption during an impact on a composite material part. Statement of the invention

[0003] The present invention relates to a part made of composite material with improved shock absorption capacity, comprising a fibrous reinforcement having an evolving textile weave and densified by a matrix, said evolving textile weave comprising (i) at least one structural portion formed by three-dimensional weaving of first threads with second threads and in which all or part of the first threads have a first weave, and (ii) at least one damping portion in which all or part of the first threads are spaced apart so as to have a second weave greater than the first weave and thus to define in the part shock absorption cavities having a lack of material or filled with a shock absorption material distinct from the matrix.

[0004] The presence of shock absorption cavities provided within the textile armor itself due to the local spacing of the first threads makes it possible to break the propagation of shock waves. In addition, the crushing of the first spaced threads located around these cavities dissipate kinetic energy, which significantly reduces the transmission of acceleration to the rest of the structure. The invention thus provides a composite material part with improved shock absorption capacity.

[0005] In an exemplary embodiment, the evolving textile armor comprises, along a direction of potential impact, an alternation of structural portions and damping portions.

[0006] Such a feature makes it possible to further improve the attenuation of energy during impact.

[0007] In an exemplary embodiment, the evolving textile weave comprises a first damping portion in which all or part of the first threads are spaced apart so as to present the second damping, and a second damping portion in which all or part of the first threads are spaced apart so as to present a third damping greater than the first damping and different from the second damping.

[0008] Such a characteristic makes it possible to adapt the mechanical strength of the part more precisely to the stresses encountered in different areas of the part.

[0009] In an exemplary embodiment, the first fogging is less than or equal to 2%, and the second fogging, and the possible third fogging, greater than or equal to 4%.

[0010] Such a characteristic helps to optimize the mechanical resistance of the part to shocks.

[0011] In an exemplary embodiment, the first wires spaced from said at least one damping portion belong to unidirectional layers of wires.

[0012] Such a characteristic has the advantage of simplifying the textile operation of weaving the evolving textile armor and can be favored for armors that are relatively complex in the structural portion.

[0013] Alternatively, the first threads spaced from said at least one damping portion are woven by three-dimensional weaving.

[0014] Such a characteristic makes it possible to avoid carrying out a step of separating the first threads after weaving.

[0015] In an exemplary embodiment, the part is made of organic matrix composite material.

[0016] In particular, the part may be a fan casing, or a fan blade. More generally, the part may be a turbomachine part, in particular an aeronautical turbomachine.

[0017] The invention also relates to a method for manufacturing a part made of composite material as described above, comprising: - the formation of a fibrous preform of the part to be obtained having the evolving textile weave with, in said at least one damping portion, all or part first wires separated by spacers accessible from the outside of the preform or made of shock-absorbing material, and - densifying the fiber preform by the matrix, the method optionally further comprising, after densification, removing or eliminating the spacers accessible from the outside of the preform in order to obtain the part with shock-absorbing cavities having a lack of material. Brief description of the drawings

[0018] [Fig.l] [Fig.l] schematically and partially represents a fibrous strip intended to form the fibrous reinforcement of a fan casing according to the invention as well as the evolution of the textile armor along the strip.

[0019] [Fig.2] [Fig.2] represents a preform of the casing obtained by winding the strip of [Fig.l].

[0020] [Fig.3] [Fig.3] represents, schematically and partially in linear view, the evolving textile armor of [Fig.l] densified by the matrix.

[0021] [Fig.4] [Fig.4] represents, in a schematic and partial manner, a variant of damping portion of an evolving textile armor usable within the framework of the invention.

[0022] [Fig.5] [Fig.5] represents, in a schematic and partial manner, a variant of evolving textile armor intended to form the fibrous reinforcement of a fan blade. Description of the embodiments

[0023] [Fig. 1] represents a fibrous strip 1 intended to form a fibrous reinforcement for a fan casing with improved shock absorption capacity in the context of an example of application of the invention. The lower part of [Fig. 1] represents the strip 1 in top view and the upper part the textile weave thereof seen in a section plane containing the longitudinal direction X. In the example illustrated in [Fig. 1], the strip 1 has a textile weave that evolves along a longitudinal direction X with an alternation of structural portions 3 and damping portions 5. In other words, one passes successively from a structural portion 3 to a damping portion 5 then again to a structural portion 3 and so on.The portions 3 and 5 may have increasing lengths along the direction X so that each of them corresponds substantially to a complete turn of winding of the strip around the casing forming tool. According to a variant, each of the portions 3 and 5 may have a length corresponding substantially to a half-turn of winding of the strip around the tool. However, it does not depart from the scope of the invention when this is not the case.

[0024] Each portion 3 is formed by three-dimensional weaving of first yarns 10 with second yarns 20. The first yarns 10 may be the warp yarns and the second yarns 20 the weft yarns or vice versa, the roles between the warp and weft yarns being interchangeable. In the example illustrated, each portion 3 has an “interlock” weave, that is to say a weave weave in which each warp layer links several weft layers with all the yarns of the same warp column having the same movement in the plane of the weave, the person skilled in the art will recognize that the invention is not limited to a particular three-dimensional weave weave. For application to a fan part, first 10 and second 20 yarns of carbon, glass or a combination of carbon and glass yarns may be used.Each portion 3 may be woven so as to obtain in these portions, after densification, a solid composite material having a relatively high fiber content, typically greater than or equal to 50%. All or part of the first yarns 10, in particular the majority (more than 50%) or even all of them, may have a first weft less than or equal to 2% in each portion 3. Weft is a quantity known to those skilled in the art and quantifies the waviness of the yarns in a textile. The higher the weft, the more the yarn wavinesses in the textile. Weft corresponds to the relative difference between the length of the first yarns 10, denoted L in the formula below, and the length of the textile or the textile portion in which these first yarns are present, denoted Lo. Weft E is thus calculated by applying the formula below.

[0025] [Math.l] y a JC 100 X<'0

[0026] In the example illustrated, the portions 5 are in the textile extension of the portions 3, the same first yarn 10 extending alternately between a portion 3 and a portion 5. In the case of [Fig.l], each portion 5 was obtained by omitting to weave all or part of the first yarns with second yarns, thus defining unidirectional layers of first yarns 10 in these portions. These unidirectional layers can be separated by positioning spacers 30 between layers of first yarns 10 after weaving. The spacers 30 make it possible to increase the weaving of the first yarns 10 separated relative to the first weaving of these yarns in the portions 3, by bringing it to a second weaving greater than or equal to 4% for example. Those skilled in the art will recognize that different shapes of spacers 30 are conceivable, such as for example a bar shape with a circular, non-circular elliptical or polygonal section.Various materials may be used for the spacers 30 depending on whether or not the latter are intended to remain in the resulting part, as will be described below. All or part of the first wires 10, in particular the majority (more than . 50%) or even the entirety, can be separated in the portions 5 and present the second weaving. The weaving of the strip 1 illustrated in [Fig.l] uses a technique known per se by alternating 3D weaving portions to form the structural portions 3 and non-woven portions where the first threads 10 form unidirectional layers to form the damping portions 5 once separated. This gives a one-piece evolving textile weave comprising the alternation of portions 3 and 5 which is then wound around a form 50 so as to obtain a preform 60 of a fan casing. In the example illustrated, the structural 3 and damping 5 portions follow one another along the longitudinal direction X of the evolving textile weave. As indicated above, each portion 3 or 5 may or may not extend over exactly half a turn or a complete turn once wound on the form 50.After winding, a preform 60 is obtained, and then a part, having along a potential impact direction DI an alternation of structural portions 3 and damping portions 5 ([Fig.2]). The potential impact direction DI corresponds here to a radial direction and to the projection direction of a detached blade or a blade fragment driven by the centrifugal force in operation. A plurality of sectors 54 can then be positioned on the preform 60 in order to form an injection mold and a resin is introduced into the porosity of the preform in order to form the matrix by a technique known per se. This introduction can be followed by a heat treatment in the case of a thermosetting resin. A fan casing 11 is obtained densified by an organic matrix 40 as illustrated in [Fig.3] which is a linear view for the sake of simplification of the illustration, it being understood that the different zones following one another linearly are wound around each other in the fan casing obtained. Note the presence of shock absorption cavities 300 having a lack of material in the illustrated example. These cavities 300 were formed after removal of the spacers 30 once the densification was carried out. In the part obtained, the matrix 40 keeps the first wires 10 separated with the second embouchure in the portions 5. The first wires 10 separated are here located around the cavities 300. When the matrix material 40 was introduced, the spacers 30 were present which led to an introduction of the matrix material into the entire armor except at the level of the volumes occupied by the spacers 30. After formation of the matrix 40, the spacers 30, which were for example formed of a metallic material, were removed. In order to allow this removal, care was taken to ensure that the spacers 30 remained accessible from the outside of the textile strip. The spacers 30 may also be covered with a release agent (not shown) in order to facilitate this removal. As an example of a release agent, the commercial product Zyvax® Departure™ or polytetrafluoroethylene (Teflon™) may be used for an epoxy matrix. The removal of the spacers 30 advantageously makes it possible to minimize the mass of the part 11. It will be recognized that the spacers 30 can alternatively be removed chemically, for example by dissolving the spacer 30 in a selective solvent. Thus, the spacers 30 can be made of a polymeric material, for example thermoplastic, while being accessible from outside the part 11 in order to allow their removal by immersion in a bath of this solvent in order to form the shock absorption cavities 300. In general, care will be taken to choose the material of the spacers 30 so that it is not significantly affected during the introduction of the matrix material and its possible crosslinking. According to a variant not illustrated for the case of the example currently described, the spacers 30 can remain in the part mounted in the turbomachine.Thus, it may be preferred, in order to further increase the shock absorption capacity, to have spacers 30 formed from a shock absorption material distinct from the matrix, such as for example an elastomeric material, preferably not reinforced. The shock absorption material may have a damping factor, tangent delta, determined by dynamic mechanical analysis (“Dynamic Mechanical Analysis”; “DMA”) greater than or equal to 2%, for example greater than or equal to 10%, for example between 10% and 30%. Generally, a plurality of shock absorption cavities 300 are obtained in the part which may be separate from one another, as illustrated. By way of illustration, the volume proportion occupied by these cavities 300 in the part may be between 10% and 50%, for example between 20% and 40%, or even between 25% and 35%.An example is shown where the increased damping of the first wires 10 is substantially constant between each damping portion 5. It does not go beyond the scope of the invention when this damping is variable, for example due to the use of spacers of variable dimensions between different damping portions. According to one example, the damping of the first spaced wires 10 may decrease along the direction X so as to obtain maximum damping in the first layers of the winding.

[0027] An example has just been described, in connection with Figures 1 to 3, where the strip 1 is obtained by a first weaving operation so as to provide an alternation of 3D woven structural portions 3 and non-woven damping portions 5 formed by unidirectional layers, followed by a second operation of positioning the spacers 30 so as to separate the unidirectional layers in the portions 5. [Fig. 4] illustrates a variant where each damping portion 5a comprises first yarns 10 spaced apart but which are also woven with second yarns 20, for example with an “interlock” weave. However, in this case, the first yarns 10 have, in the portions 5, a greater weaving than that encountered in the portions 3 due to the weaving with second yarns 32 of larger diameter than the second yarns 20. These second yarns 32 may be made of a material shock absorption, for example. The rest of the process continues in a similar manner by introducing the matrix material, and obtaining the shock absorption cavities.

[0028] The examples which have just been described, in connection with figures 1 to 4 concern the case of a fan casing but the invention finds an application for other parts. In this respect, [Fig.5] illustrates the case of an evolving textile weave 1b intended to form a fibrous reinforcement of a fan blade. According to this example, the textile weave 1b comprises a structural part 3b defining a surface of the reinforcement and obtained by three-dimensional weaving, for example with “interlock” weave as well as a damping portion 5b which comprises first threads 10 untied from the portion 3b and having an increased damping by positioning spacers 30 in accordance with the principle described above. In the illustrated example, the structural portion 3b surrounds the damping portion 5b. According to this example, the portion 3b and the portion 5b are offset along a thickness of the blade. Each of the portions 3b and 5b extends in a longitudinal direction of the blade.Portions 3b and 5b run parallel to each other.

Claims

Claims

1. Fan casing (11) made of composite material with improved shock absorption capacity, comprising a fibrous reinforcement having a scalable textile weave (1) and densified by a matrix (40), said scalable textile weave comprising (i) at least one structural portion (3; 3b) formed by three-dimensional weaving of first threads (10) with second threads (20) and in which all or part of the first threads have a first weave, and (ii) at least one damping portion (5; 5a; 5b) in which all or part of the first threads are spaced apart so as to have a second weave greater than the first weave and thus to define in the casing shock absorption cavities (300) having a lack of material or filled with a shock absorption material (32) distinct from the matrix.

2. Fan casing (11) according to claim 1, in which the evolving textile armor (1) comprises, along a potential impact direction (DI), an alternation of structural portions (3) and damping portions (5).

3. Fan casing (11) according to claim 1 or 2, in which the evolving textile weave (1) comprises a first damping portion in which all or part of the first threads (10) are spaced apart so as to present the second damping, and a second damping portion in which all or part of the first threads are spaced apart so as to present a third damping greater than the first damping and different from the second damping.

4. Fan casing (11) according to any one of claims 1 to 3, in which the first fogging is less than or equal to 2%, and the second fogging, and the possible third fogging, greater than or equal to 4%.

5. A fan casing (11) according to any one of claims 1 to 4, wherein the first wires (10) spaced from said at least one damping portion belong to unidirectional layers of wires.

6. A fan casing (11) according to any one of claims 1 to 4, wherein the first yarns (10) spaced from said at least one damping portion are woven by three-dimensional weaving.

7. A fan casing (11) according to any one of claims 1 to 6, wherein the casing is made of an organic matrix composite material.

8. A method of manufacturing a fan casing made of composite material according to any one of claims 1 to 7, comprising: - forming a fiber preform of the casing to be obtained having the evolving textile weave with, in said at least one damping portion (5; 5a; 5b), all or part of the first threads (10) spaced apart by spacers (30) accessible from the outside of the preform or made of shock-absorbing material (32), and - densifying the fiber preform by the matrix (40), the method optionally further comprising, after densification, removing or eliminating the spacers accessible from the outside of the preform in order to obtain the casing with shock-absorbing cavities (300) having a lack of material.

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