Preform, mechanical part, lander and associated manufacturing process

Abstract

Preform of a mechanical part, the preform comprising at least: A first subpreform (4) which is formed at least in part from an assembly of fibers, A second subpreform (10) which is formed at least in part from an assembly of fibers, the second subpreform externally surrounding the first subpreform, the first and second subpreforms together forming a longitudinally extending body, the preform comprising at least one protection (13) of at least a portion of the preform, the protection being capable of covering at least an area of ​​at least one of the longitudinal faces of the body. Part, lander and associated methods. FIGURE IN ABRIDGED: Fig. 1

Description

Title of the invention: Preform, mechanical part, landing gear and associated manufacturing process

[0001] The present invention relates to a preform.

[0002] The present invention also relates to a mechanical part formed from such a preform.

[0003] The present invention also relates to a lander comprising such a mechanical part.

[0004] The present invention also relates to a method for manufacturing such a mechanical part.

[0005] BACKGROUND OF THE INVENTION

[0006] A landing gear generally comprises at least one strut articulated to a leg of the landing gear on one side and to a fixed part of the associated aircraft on the other. The strut is generally formed of two connecting rods: an upper connecting rod and a lower connecting rod. The connecting rods are articulated to each other and to other parts of the landing gear at their longitudinal ends.

[0007] These connecting rods are generally subjected in operation to significant mechanical stresses, mainly in compression and tension, oriented along the longitudinal axis of the connecting rod considered.

[0008] In order to reduce the mass of these connecting rods, it is now known to manufacture them from a composite material.

[0009] To this end, a connecting rod can be manufactured from an assembly of two three-dimensionally woven fibrous reinforcements. The first fibrous reinforcement extends longitudinally, while the second fibrous reinforcement forms a band around the first. The assembly also has two openings for the future articulation of the connecting rod.

[0010] Such an assembly makes it possible to propose a connecting rod exhibiting generally good structural qualities.

[0011] However, cracks tend to appear at the interface between the first fibrous reinforcement and the second fibrous reinforcement, which can considerably damage the connecting rod.

[0012] SUBJECT OF THE INVENTION

[0013] The invention aims in particular to provide a solution to limit the risk of mechanical degradation of an elongated part. Summary of the invention

[0014] For this purpose, according to the invention, a preform of a mechanical part is provided, the preform comprising at least: • A first sub-preform forming a core of the preform, the core comprising a fibrous reinforcement which is formed at least in part from an assembly of fibers, • A second sub-preform forming a belt of the preform, the belt comprising a fibrous reinforcement which is formed at least in part from an assembly of fibers, the second sub-preform externally surrounding the first sub-preform,

[0015] the first sub-preform and the second sub-preform together forming a body extending longitudinally along a given axis and provided at a first end with at least one first orifice and at a second end with at least one second orifice, each orifice opening onto two opposite longitudinal faces of the body.

[0016] According to the invention, the preform comprises at least one protection of at least a part of the preform, the protection comprising a fibrous reinforcement which is formed at least in part from an assembly of fibers, the protection being able to cover at least an area of ​​at least one of the longitudinal faces of the body at the level of an interface between the first sub-preform and the second sub-preform.

[0017] Thus, the protection limits a transfer of forces between the two sub-preforms at the interface between these two sub-preforms.

[0018] The protection makes it possible in particular to locally reinforce the area of ​​the interface between the two sub-preforms covered by the protection.

[0019] Optionally, the protection is formed at least in part of a material different from that of the first sub-perform and / or the second sub-preform.

[0020] Optionally, the protection is formed at least in part of a material identical to that of the first sub-perform and / or the second sub-preform.

[0021] Optionally, a one-piece fibrous blank jointly forms the fiber assembly of the fibrous core reinforcement and the fiber assembly of the fibrous belt reinforcement.

[0022] Optionally, the one-piece fibrous blank jointly forms the fiber assembly of the core fibrous reinforcement, the fiber assembly of the belt fibrous reinforcement, and the fiber assembly of the protection.

[0023] Optionally, the fiber assembly of the fibrous reinforcement of the protection is distinct from at least that of the core or the belt.

[0024] Optionally, the fiber assembly of the fibrous reinforcement of the protection is dry and / or pre-impregnated.

[0025] Optionally, at least a portion of the fibers of the fibrous reinforcement of the protection extends in an inclined direction at a given angle with respect to the given axis when the protection is in place against the body.

[0026] Optionally, the protection is shaped to cover at least the entire area of ​​the longitudinal face of the body forming the interface between the first sub-preform and the second sub-preform.

[0027] Optionally, the fibrous reinforcement of at least one of the core, belt or protection is formed at least in part by a weave of fibers.

[0028] Optionally, the fibrous reinforcement of at least one of the core, belt or protection includes carbon fibers.

[0029] Optionally, the fibrous reinforcement of at least one of the core, belt or protection is a three-dimensional assembly of fibers.

[0030] Optionally, the fiber assembly of the fibrous reinforcement of the protection is densified by a resin, the protection thus being made of composite material and intended to be fixed to the body.

[0031] Optionally, at least the protection is formed at least in part by a laminated composite.

[0032] Optionally, the protection is a first protection and the longitudinal face of the body a first longitudinal face of the body, the preform comprising at least a second protection of at least one other part of the preform, the second protection comprising a fibrous reinforcement which is formed at least in part of an assembly of fibers, the second protection being able to cover at least one other area of ​​at least one second of the longitudinal faces of the body at the level of an interface between the first sub-preform and the second sub-preform.

[0033] The invention also relates to a mechanical part comprising a preform as above, the first sub-preform, the second sub-preform and at least one protection being joined together and all densified by at least one resin.

[0034] Optionally, the part is a connecting rod of a strut for a lander.

[0035] The invention also relates to a lander comprising a part such as the one mentioned above.

[0036] The invention also relates to a method of manufacturing a mechanical part such as the one mentioned above, comprising at least one step of assembling fibers for the creation of the fibrous reinforcement of the belt, the core and at least one protection, and at least one step of densifying the fibrous reinforcements by at least one resin.

[0037] Optionally, the process includes: - a single step of assembling the fibers to form a one-piece fibrous blank which together forms the fibrous reinforcement of the core and the fibrous reinforcement of the belt and the fibrous reinforcement of at least one protection; - a single densification step of the fibrous blank comprising the successive phases of: • Impregnate the fibrous blank with a matrix-forming resin, • Polymerize the assembly formed from the fibrous blank and the resin.

[0038] Optionally, the process includes the successive steps of: - To carry out, separately or jointly, the fibrous reinforcement of the core and the belt, - Impregnate the fibrous core reinforcement and the fibrous belt reinforcement in the same mold with a matrix-forming resin, - Polymerize the assembly formed by the two fibrous reinforcements and the resin, - Attach at least one protective element to the assembled unit.

[0039] Optionally, the attachment of at least one protection to the assembly formed comprises at least the following phases: - Apply at least one protective layer to the assembled unit, with at least one layer being in the form of a pre-impregnated and / or dry assembly. - Impregnate the assembly with a matrix-forming resin, including at least one protective layer. - Polymerize the assembly of the formed unit and at least one protective layer.

[0040] Optionally, the attachment of at least one protection on the assembly formed is carried out by screwing and / or gluing.

[0041] Optionally, the process includes at least the steps of: - Separately form the fibrous reinforcement of the core, the belt, and at least one protective layer. - To bring together the three reinforcements in a single mold, - Impregnate the three assemblies with a matrix-forming resin, - Polymerize the assembly formed by these three assemblies.

[0042] Other features and advantages of the invention will become apparent from the following description of particular and non-limiting embodiments of the invention.

[0043] Hereafter, only the term "protection" may be used for simplicity. Unless otherwise indicated, it may refer to the first protection as well as any other protection of the preform (such as the second protection, for example). Brief description of the drawings

[0044] Reference will be made to the attached drawings, among which:

[0045] [Fig-1] [Fig.1] is a three-dimensional view of a body of a preform according to a first embodiment of the invention, inserts being inserted into said body;

[0046] [Fig.2] [Fig.2] is a three-dimensional view of the preform comprising the body represented in [Fig.1];

[0047] [Fig. 3] [Fig. 3] is a partial longitudinal sectional view of the preform represented in [Fig.2], the cutting plane passing through a protection of the pre-slab;

[0048] [Fig. 4] [Fig. 4] is a perspective view of an aircraft comprising a part manufactured from the preform shown in [Fig.3];

[0049] [Fig. 5] [Fig. 5] is a three-dimensional view of a preform according to a second method of embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0050] With reference to Figures 1 to 3, a preform 1 according to a first embodiment of the invention will now be described. The preform 1 comprises a body 5 which extends longitudinally along a longitudinal axis X.

[0051] The body 5 is elongated along the longitudinal axis X. The body 5 thus has a length which is greater than its width and thickness.

[0052] The body 5 has two longitudinal ends.

[0053] Furthermore, a first orifice 2 is provided in the body 5 at its first longitudinal end, and a second orifice 3 is provided in the body 5 at its second longitudinal end. Each orifice 2, 3 is open at both ends. The first orifice 2 thus opens at its first end onto a first longitudinal face of the body 5 and at its second end onto a second longitudinal face of the body 5 (opposite the first longitudinal face). The two longitudinal faces of the body 5 are, of course, external faces of said body.

[0054] Equivalently, the second orifice 3 thus opens at its first end onto the first longitudinal face of the body 5 and at a second end onto the second longitudinal face of the body 5.

[0055] The first orifice 2 extends into the body 5 along a first axis A, and the second orifice 3 extends into the body 5 along a second axis B. The first axis A and the second axis B are preferably parallel to each other. The longitudinal axis X intersects the first axis A and the second axis B. Preferably, the first axis A and the second axis B both extend orthogonally to the longitudinal axis X.

[0056] The body 5 is in fact composed of a first sub-preform 4 and a second sub-preform 10 of the preform 1.

[0057] The first sub-preform 4 thus forms a soul of the preform 1.

[0058] The first sub-preform 4 is for example shaped into a beam whose cross-section is in I. Optionally said cross-section has dimensions varying along the longitudinal axis X.

[0059] The first sub-preform 4 extends longitudinally along the longitudinal axis X. The first sub-preform 4 is elongated along the longitudinal axis X. The first sub-preform 4 thus has a length that is greater than its width and thickness. The first sub-preform therefore has two longitudinal ends 6, 7.

[0060] The first sub-preform 4 comprises a fibrous reinforcement which is formed at least in part from an assembly of fibers.

[0061] For example, this assembly is three-dimensional.

[0062] For example, the assembly can be achieved by braiding the fibers and / or weaving the fibers and / or embroidering the fibers and / or stacking layers of unidirectional and / or multidirectional fibers, etc.

[0063] The assembly can be in three dimensions single layer (the first sub-preform 4 thus has only one layer comprising a three-dimensional fiber assembly) and / or be in two dimensions multi-layer (the first sub-preform 4 thus has several superimposed layers, each layer comprising a dimensional fiber assembly, the different layers being optionally joined together for example by stitching and / or by gluing).

[0064] In the present case, the entire first sub-preform 4 is formed by a three-dimensional assembly of fibers and for example by a three-dimensional weaving of fibers.

[0065] Said assembly is formed here solely of dry fibers (i.e. the fibers are not pre-impregnated).

[0066] The fibers are, for example, at least some of them, and preferably most of them, carbon fibers. Optionally, all the fibers in the assembly are carbon fibers.

[0067] The first sub-preform 4 comprises warp fibers and weft fibers. The warp fibers extend, for the most part, in a general direction which is parallel to the longitudinal axis X. The warp fibers are therefore the fibers of the first sub-preform 4, mainly connecting the two openings 2, 3.

[0068] This allows, for example, to promote the mechanical resistance in compression of the preform 1 (when it is subjected to longitudinal compressive forces).

[0069] Preferably, the ratio "number of warp fibers" to "number of weft fibers" is not the same for the entire first sub-preform 4. Preferably, the material (comprising the weft fibers as well as the warp fibers) remains the same for the entire first sub-preform 4.

[0070] For example, said ratio is greater on a central section 5 of the first sub-preform 4 than on its longitudinal ends 6, 7. For example, said ratio corresponds to a central symmetry (along a plane of central symmetry whose normal is the longitudinal axis X). For example, the ratio is the same for both longitudinal ends of the first sub-preform 4.

[0071] For example, the two longitudinal ends 6, 7 of the first sub-preform 4 are defined so as to have a ratio between 0.5 and 1.5, and for example between 0.8 and 1.2, and is for example 1. For example, the central section 8 is defined so as to have a ratio between 1.75 and 2.75, and for example between 2 and 2.5, and is for example 2.3.

[0072] Preferably, the first sub-preform 4 has junction zones 9 between its central section 8 and each of its longitudinal ends 6, 7. Said junction zones 9 are defined so as to have a ratio that increases progressively as one approaches the central section 8.

[0073] It is noted here that the ratio is different on the length of the first sub-preform 4 (along the longitudinal axis X) but is identical on the other two dimensions of the first sub-preform 44.

[0074] As indicated above, the preform 1 also includes a second sub-preform 10. This second sub-preform 10 is arranged around the first sub-preform 4. The second sub-preform 10 thus forms an external belt to said first sub-preform 4. In particular, the second sub-preform 10 surrounds the first sub-preform 4 over its entire periphery. The second sub-preform 10 is thus closed.

[0075] In the present case, the second sub-preform 10 surrounds the upper and lower flanges of the first sub-preform 4 (the first sub-preform 4 here forming a beam with an I-shaped cross-section).

[0076] Preferably, the second sub-preform 10 has a width similar or identical to that of the soles of the first sub-preform 4. This allows for a relatively large contact area between the two sub-preforms. This improves the overall cohesion of the preform 1.

[0077] The width of the first sub-preform, like the width of the second sub-preform, like the width of the body 5, like the width of the preform 1, is considered along a lateral axis Y which is orthogonal to the longitudinal axis X and / or parallel to at least one of the first axis A or the second axis B. Preferably, the first sub-preform 4 is centered in the second sub-preform 10 at least along the lateral axis Y and preferably at least along the lateral axis Y and the longitudinal axis X.

[0078] The second sub-preform 10 allows, for example, to improve the mechanical tensile strength of the preform 1 (when it is subjected to longitudinal tensile forces).

[0079] The second sub-preform 10 comprises a fibrous reinforcement which is formed at least in part from an assembly of fibers. In the example, this assembly is three-dimensional.

[0080] For example, the entire second sub-preform 10 is formed by a three-dimensional assembly of fibers.

[0081] The assembly can be achieved by braiding the fibers and / or weaving the fibers and / or embroidering the fibers and / or stacking layers of unidirectional and / or multidirectional fibers, etc.

[0082] The assembly can be in three dimensions single layer (the second sub-preform 10 thus has only one layer comprising a three-dimensional fiber assembly) and / or be in two dimensions multi-layer (the second sub-preform 10 thus has several superimposed layers, each layer comprising a dimensional fiber assembly, the different layers being optionally joined together for example by stitching and / or by gluing).

[0083] Said assembly is formed here solely of dry fibers (i.e. the fibers are not pre-impregnated).

[0084] It is noted therefore that the first sub-preform 4 and the second sub-preform 10 together form the body 5 sec.

[0085] Conversely, and as will be indicated below, the body 5 will then be placed in a mold into which at least one resin will be injected. At the end of this step, an intermediate composite element will be obtained, since it will be composed of a three-dimensional assembly of fibers with a matrix (the resin in this case). In particular, the resin makes it possible to densify the associated fibrous network(s).

[0086] The fibers of the second sub-preform 10 are, for example, at least some of them, and preferably most of them, carbon fibers. Optionally, all the fibers of the assembly of the second sub-preform 10 are carbon fibers.

[0087] The second sub-preform 10 is here composed of a plurality of overlapping assembly layers. The second sub-preform 10 thus comprises between four and eight layers and here comprises six layers. All the layers are advantageously formed at least in part from a unidirectional and / or two-dimensional and / or three-dimensional assembly of fibers as described above. The different layers can optionally be pre-assembled together (by stitching, gluing, interlocking, etc.) before resin injection during the formation of the intermediate element. In all cases, the resin ensures the junction between the different layers of the second sub-preform 10 during the formation of the intermediate element.

[0088] The second sub-preform 10 allows a continuous fiber assembly to be formed around the first platform 4.

[0089] This makes it possible to improve the mechanical resistance of the preform 1 (in tension and / or in rupture and / or in shear).

[0090] The second sub-preform 10 comprises warp fibers and weft fibers. The warp fibers extend, for the most part, in a general direction which is parallel here to the longitudinal axis X.

[0091] Preferably, the ratio "number of warp fibers" to "number of weft fibers" is the same for the entire second sub-preform 10. Preferably, the material composing the weft fibers as well as the warp fibers remains the same for the entire second sub-preform 10.

[0092] For example, the second sub-preform 10 is defined so as to have a ratio between 1.75 and 2.75, and for example between 2 and 2.5, and for example 2.3.

[0093] The first orifice 2 and the second orifice 3 are provided in the first sub-platform 4 and / or in the second sub-preform 10.

[0094] In the present case, the first sub-platform 4 and the second sub-preform 10 jointly define the first orifice 2 and the second orifice 3. Thus, the first orifice 2 is formed partly in the first sub-platform 4 at the level of the first longitudinal end 6 of the first sub-platform 4 and partly in the second sub-platform 10 opposite the first longitudinal end 6 of the first sub-platform 4. Thus, the second orifice 3 is formed partly in the first sub-platform 4 at the level of the second longitudinal end 7 of the first sub-platform 4 and partly in the second sub-platform 10 opposite the second longitudinal end 7 of the first sub-platform 4.

[0095] For example, each of the two orifices is defined half by the first sub-platform 4 and half by the second sub-platform 10.

[0096] The first orifice 2 opens at its first end onto a first external face of the first sub-platform 4 and the second sub-platform 10, and at its second end onto a second face of the first sub-platform 4 and the second sub-platform 10 (opposite to the first external face). Equivalently, the second orifice 3 thus opens at its first end onto the first external face of the first sub-platform 4 and the second sub-platform 10 and at its second end onto the second external face of the first sub-platform 4 and the second sub-platform 10. In this way, the first orifice 2, like the second orifice 3, only open into the body 5 at the level of the two longitudinal faces of said body 5.

[0097] It is thus understood that the orifices 2, 3 are each located at the interface between the two sub-preforms 9, 10. Preferably, the preform 1 comprises at least one insert arranged in at least one of the orifices 2, 3.

[0098] Preferably, a first insert 11 is housed in the first orifice 2 and a second insert 12 is housed in the second orifice 3. At least one of the inserts 11, 12 has a central portion extending on either side of a flange, the flanges bearing against one of the two external faces of the preform 1 and / or a protective element as described below. At least one of the inserts 11, 12 is, for example, made of or based on metal. At least one of the inserts 11, 12 is, for example, made of titanium.

[0099] The preform 1 also includes at least one protection and preferably at least two protections.

[0100] The two protections are here identical (except potentially in terms of shape and / or dimensions) so that the following description of the first protection 13 is also applicable to the second protection.

[0101] The first protection 13 includes a fibrous reinforcement which is formed at least in part from an assembly of fibers.

[0102] The first protection 13 is here in a different material from the first sub-preform 4 and the second sub-preform 10. Thus, while the said sub-preforms are dry sub-preforms, the first protection 13 is in a prepreg material.

[0103] The first protective layer 13 is thus formed at least in part by an assembly of pre-impregnated fibers. For example, the first protective layer 13 is formed in part or in whole of carbon fibers pre-impregnated by at least one resin, for example by an epoxy resin.

[0104] The first protection 13 is thus here made of composite material.

[0105] The assembly can be achieved by braiding the fibers and / or weaving the fibers and / or embroidering the fibers and / or stacking layers of unidirectional and / or multidirectional fibers, etc.

[0106] The fiber assembly can be a single-layer three-dimensional assembly (the first protection 13 thus has only one layer comprising a three-dimensional fiber assembly) and / or be a multi-layer two-dimensional assembly (the protection 13 thus has several superimposed layers, each layer comprising an assembly of unidirectional and / or multidirectional fibers, the different layers being optionally joined together for example by sewing and / or gluing).

[0107] The first protection 13 is here composed of a plurality of overlapping assembly layers. The first protection 13 comprises, for example, between two and eight layers. In the present case, all the layers are advantageously formed, at least in part, from a unidirectional and / or two-dimensional and / or three-dimensional assembly of fibers as described above. The different layers may optionally be pre-assembled together (by stitching, gluing, interlocking, etc.).

[0108] The first protection 13 is thus formed here at least in part from a stratification of pre-impregnated fiber layers. Each layer here presents a two-dimensional assembly of fibers.

[0109] In the present case, the entire first protection 13 is composed of a stratification of pre-impregnated fiber layers. Each layer here presents a two-dimensional assembly of fibers.

[0110] Each layer comprises warp fibers and weft fibers.

[0111] For a given layer, the weft fibers extend for the most part in a general direction C and the warp fibers extend for the most part in a general direction D which is orthogonal to the general direction C).

[0112] Preferably, the first protection 13 is shaped so that, for at least one layer, the general direction C is inclined (i.e., neither parallel nor orthogonal) with respect to the longitudinal axis X. For example, the general direction C is inclined at an angle α between 5 and 50 degrees (absolute value), and for example at an angle α between 15 and 50 degrees (absolute value), and for example at an angle α between 30 and 45 degrees (absolute value). For example, α is approximately equal to 45 degrees (absolute value).

[0113] Preferably, the first protection 13 is shaped so that, for at least one layer, the general direction D is inclined (i.e., neither parallel nor orthogonal) with respect to the longitudinal axis X. For example, the general direction D is inclined at an angle α between 5 and 50 degrees (absolute value), and for example at an angle α between 15 and 50 degrees (absolute value), and for example at an angle α between 30 and 45 degrees (absolute value). For example, α is approximately equal to 45 degrees (absolute value).

[0114] In the present case, the general direction C is inclined at an angle a for the layer considered and the general direction D is therefore inclined at an angle - a for the same layer.

[0115] Optionally, for all the layers of the first protection, the weft fibers extend for the majority of them in the general direction C and the warp fibers extend for the majority of them in the general direction D.

[0116] Preferably, a layer in which the weft fibers extend for the majority of them in the general direction C, with said general direction C inclined at an angle +a with respect to the longitudinal axis X, (the warp fibers then extending for the majority of them in the general direction D, with said general direction D inclined at an angle -a with respect to the longitudinal axis X) is superimposed a layer in which the weft fibers extend for the majority of them in the general direction C, with said general direction C inclined at an angle -a with respect to the longitudinal axis X, (the warp fibers then extending for the majority of them in the general direction D, with said general direction D inclined at an angle +a with respect to the longitudinal axis X) and vice versa.

[0117] This allows for a first balanced protection 13 when considering the overall stacking of the different layers.

[0118] Regardless of its composition, the ratio "number of warp fibers" to "number of weft fibers" is the same for the entire first protection 13. Preferably, the material (comprising the weft fibers as well as the warp fibers) remains the same for the entire first protection 13.

[0119] For example, the ratio of the first protection is between 0.5 and 1.5, and is for example between 0.8 and 1.2, and is for example 1.

[0120] Whatever its composition, the first protection 13 is presented here in the form of a plate having two principal faces preferably parallel to each other.

[0121] The first protection 13 has a thickness defined along an axis which forms a normal to the principal faces of the first protection 13. Said thickness is for example between 0.2 and 5 millimeters, and is for example between 0.5 and 3 millimeters, and is for example between 1 and 2.5 millimeters and is for example between 1.8 and 2.2 millimeters and is for example 2 millimeters.

[0122] The first protection 13 has an opening that passes completely through its thickness. The opening thus leads at one end to the first main face of the first protection 13 and at a second end to the second main face of the first protection 13. The opening passes through the first protection, preferably extending along an axis that forms a normal to the main faces of the first protection 13.

[0123] The first protection 13 is preferably arranged on the intermediate element (and therefore on the body 5) so that its principal faces extend parallel to the longitudinal axis X and / or orthogonally to the lateral axis Y. The first protection 13 is preferably arranged in the preform 1 so that its principal faces extend parallel to one of the longitudinal faces of the body 5.

[0124] The first protection 13 is arranged on the body 5 to cover at least one area of ​​at least one of the longitudinal faces of the body 5, at the level of an interface between the first sub-preform 4 and the second sub-preform 10.

[0125] In this way, the first protection 13 forms an outer layer for at least a portion of the body 5.

[0126] Preferably, the area of ​​the body 5 covered by the first protection 13 includes the portion of the body 5 defining the first end of the first orifice 2.

[0127] Preferably, the first guard 13 is arranged here so as to surround the first end of the first orifice 2 at 360 degrees. The first guard 13 is thus arranged so that its opening extends coaxially with the first orifice 2. Preferably, the opening has a cross-section identical to that of the first orifice 2. In this way, the opening forms an extension of the first orifice 2.

[0128] Preferably, the first protection 13 is arranged to cover at least the entire interface between the first sub-preform 4 and the second sub-preform 10 on one of the longitudinal faces of the body 5. In the present case, the first protection 13 is arranged to cover the entire first longitudinal face of the body 5. Thus, the first protection forms an external layer to the entire first longitudinal face of the body 5.

[0129] Thus, the first protection 13 is arranged so as to cover the body 5 over its entire height (along a third axis Z which is orthogonal to the longitudinal axis X and to the lateral axis Y).

[0130] It is therefore understood that the first protection 13 covers the first longitudinal face of the body 5 and that the second protection 14 covers the second longitudinal face of the body 5.

[0131] In the present case, the first protection 13 and the fourth protection 14 are in line with each other (along the first axis A and the second axis B).

[0132] The two shields 13 and 14 are arranged so that the general direction C and the general direction D are the same for both shields. Alternatively, the general directions associated with their fiber reinforcements may be different from one shield to another.

[0133] It is therefore understood that each protection forms a unitary layer covering a part of the first sub-preform 4 and a part of the second sub-preform 10, and in particular their interface and more precisely their interface defining the orifice considered.

[0134] This allows for fiber continuity at the interface between the first sub-preform 4 and the second sub-preform 10, and in particular at the interface forming the orifices 2, 3.

[0135] The protections thus reinforce the structural characteristics of the body 5 and therefore of the intermediate element and therefore of the preform 1 and therefore of the part from which the preform 1 is derived.

[0136] The protections allow, for example, the transmission of force between the first sub-preform 4 and the second sub-preform 10 at their interface, the force being transferred mainly externally via the protections.

[0137] The protections make it possible, for example, to limit a deformation of the longitudinal ends of the preform 1 (and therefore of the associated part) in particular in the case of longitudinal forces in compression or tension.

[0138] The protections make it possible, for example, to delay the propagation of cracks at the interface between the first sub-preform 4 and the second sub-preform 10.

[0139] The protections make it possible, for example, to reduce the risk of initiating damage at the interface between the first sub-preform 4 and the second sub-preform 10, as well as to slow down the propagation of such damage.

[0140] Thus, the preform 1 and the associated part, and in particular the longitudinal ends of the preform 1 and the associated part, which can also be called "noses", are reinforced by a protection on each of their external longitudinal faces.

[0141] The preform 1 thus created is symmetrical along at least one plane of central symmetry and here along several planes of central symmetry (including at least one plane of symmetry with normal to the longitudinal axis X and passing through the center of the preform 1 and / or at least one plane of symmetry with normal to the lateral axis Y and passing through the center of the preform 1).

[0142] We will now describe the manufacture of such a preform 1 and an associated mechanical part 20.

[0143] In a first step, the two sub-preforms 4, 10 are produced by assembling fibers. In the example described, the two assemblies are carried out independently of each other so that the two sub-preforms 4 and 10 form two separate parts.

[0144] In a second step, the two sub-preforms 4, 10 are then nested one inside the other so that the second sub-preform 10 surrounds the first sub-preform 4. Optionally, the two sub-preforms 4, 10 are pre-assembled together (by sewing, by gluing, by nesting, etc.).

[0145] In a third step, the body 5 thus formed is deposited in a mold and then resin is injected. The two sub-preforms 4, 10 are thus impregnated with resin so that the resin penetrates and saturates the fibers (without, of course, completely filling them). the orifices 2, 3). The resin is, for example, epoxy resin. We therefore note that two sub-preforms 4, 10 are permeable to resins.

[0146] In a fourth step, the "body 5 + resin" assembly is polymerized, for example by heating at controlled pressure and temperature.

[0147] Upon hardening, the resin advantageously allows the two reinforcements 4, 10 to be joined together.

[0148] A finishing machining is optionally carried out on the intermediate element thus obtained.

[0149] The intermediate element is based on a composite material, with the two sub-preforms 4, 10 forming the reinforcement of the composite material and the resin forming the matrix of this composite material.

[0150] In a fifth step, the various protective elements 13, 14 are then attached to the longitudinal faces of the intermediate element. Optionally, a pre-assembly (by stitching, gluing, interlocking, etc.) is carried out between the protective elements 13, 14 and the intermediate element.

[0151] Preform 1 is thus created.

[0152] During a sixth step, the preform 1 is again deposited in a mold in order to undergo a heating phase at controlled pressure and temperature.

[0153] This allows the resin impregnated on the fibers of the protectors 13, 14 to crosslink. Thus, the protectors 13, 14 are bonded to the intermediate element.

[0154] A finishing machining is optionally carried out on the protected intermediate element thus obtained.

[0155] In a seventh step, the inserts 11, 12 are arranged in the protected intermediate element. This insertion can be achieved, for example, by shrink fitting.

[0156] Part 20 is thus created.

[0157] Such a part 20 here forms a connecting rod that can be articulated at each of its longitudinal ends to another part, the two axes of articulation of the connecting rod being the first axis A and the second axis B. Advantageously, the inserts 11, 12 form bearings facilitating this articulation.

[0158] The part 20 obtained can for example form one of the connecting rods of a strut of an aircraft landing gear as illustrated in [Fig.4].

[0159] A second embodiment will now be described with reference to [Fig.5].

[0160] This second embodiment is identical to the first embodiment in the the difference is that the guards 13 and 14 do not cover all the longitudinal faces of the associated body 5.

[0161] In practice, each protection 13, 14 extends, from the first orifice 2 towards the central section 8, along a length (considered along the longitudinal axis X) which is less than the diameter of the first orifice 2 and, for example, along a associated length which is between one quarter and three quarters of the diameter of the first orifice 2 and for example according to a length which is between 0.1 and 2 / 3 of the diameter of the first orifice 2.

[0162] This second embodiment is also different from the first embodiment in that it has a greater number of protections.

[0163] The preform 1 here includes a third protection 15 and a fourth protection 16. The third protection 15 and the fourth protection 16 are here identical to the first protection 13 and the second protection 14.

[0164] It is therefore understood that: - the first protection 13 covers a first longitudinal end of the first longitudinal face of the body 5, - the second protection 14 covers the first longitudinal end of the second longitudinal face of the body 5, - the third protection 15 covers a second longitudinal end of the first longitudinal face of the body 5, - the fourth protection 16 covers the first longitudinal end of the second longitudinal face of the body 5.

[0165] The protections 15, 16 extend, from the second orifice 3 towards the central section 8, along a length (considered along the longitudinal axis X) which is less than the diameter of the second orifice 3 and for example along an associated length which is between one quarter and three quarters of the diameter of the second orifice 3 and for example along a length which is between 0.1 and 2 / 3 of the diameter of the second orifice 3.

[0166] In the present case, the first guard 13 and the third guard 15 are in line with each other (along an axis parallel to the longitudinal axis X), and the second guard 14 and the fourth guard 16 are in line with each other. Furthermore, the third guard 15 and the fourth guard 16 are in line with each other (along the second axis B).

[0167] Apart from what has been said above, everything that is applicable to the first embodiment is also applicable to the second embodiment.

[0168] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0169] Although the part considered here is a strut for an aircraft landing gear, the part can be used for any other application requiring the use of an elongated part articulated at both longitudinal ends. For example, the part can be used in other parts of the aircraft or in applications other than in an aircraft. by being integrated, for example, into another vehicle such as a land or sea vehicle. The part could thus be a brake rod, for example, an aircraft brake rod. The part could be a connecting rod, and in particular a composite connecting rod.

[0170] The manufacturing process of the part may differ from that indicated.

[0171] Thus, although here the first sub-preform, the second sub-preform and the While all the protective elements may be formed by independent fiber reinforcements (and manufactured independently of each other), this may not be the case. It is thus possible to manufacture, in a single fiber assembly step, at least two components from among the following: the fiber reinforcement of the first sub-preform, the fiber reinforcement of the second sub-preform, and the fiber reinforcement of at least one of the protective elements. Therefore, the preform may include a single-piece fiber blank that jointly forms at least the fiber assembly of the fiber reinforcement of the first sub-preform and the fiber assembly of the fiber reinforcement of the second sub-preform. Optionally, the preform may include a single-piece fiber blank that jointly forms at least the fiber assembly of the fiber reinforcement of the first sub-preform, the fiber assembly of the fiber reinforcement of the second sub-preform, and the fiber assembly of at least one of the protective elements.

[0172] Although the protective elements here are pre-impregnated, at least one of them may be different. This protective element may consist solely of a dry fibrous reinforcement. In this case, it will not be made of a composite material. Alternatively, the protective element may be in the form of a plate of a composite material, i.e., in a finished form (whereas in the described embodiments, a crosslinking step was necessary to complete the manufacture of the protective elements). Potentially, it will then be necessary to drill through the protective element to extend the holes created by the assembly of the two reinforcements.

[0173] Although here the sub-preforms are dry, at least one of the sub-preforms may be pre-impregnated.

[0174] Furthermore, the different components of the preform may be fixed together differently from what has been described.

[0175] Thus, regardless of the shape of at least one of the protective elements, at least said protective element can be attached to the body and / or the intermediate element by fastening (screw type) and / or bonding and / or by injecting a resin into a mold and / or by cross-linking. In the case of a common fibrous blank, the protective element can be naturally attached to the body since it is directly integrated into the first sub-preform and / or the second sub-preform.

[0176] Before any final fixing step of an element A to an element B (first sub-preform, second sub-preform or protections) by one of the means indicated As mentioned in the previous paragraph, element A and element B may be pre-assembled to each other (for example, by weaving and / or gluing and / or interlocking). In the case of interlocking, the pre-assembly will be such that it allows at least one fiber of element A to pass through element B and / or vice versa.

[0177] Although here the protective elements are either attached to the body or integrated into it (in the case of a rough shape, at least partially common), at least one of the protective elements may be associated with the body differently. For example, at least one of the protective elements may be directly applied to the body by depositing a fibrous reinforcement onto it. It will therefore be understood that in this case, a single piece will not be directly attached to the body, but rather the protective element will be manufactured directly on the body. For example, successive layers of dry and / or prepreg material may be applied to the body.

[0178] Thus, regardless of the shape of at least one of the protective elements and / or the body, the manufacturing process for the preform and / or the added part may involve a different number of injection steps. It may be possible to have no injection steps at all if all the fibrous reinforcements are pre-impregnated. It may also be possible to have only one injection step: the two sub-preforms and the protective element(s) will then be arranged in the same mold for the single resin injection step (the sub-preforms and the protective elements forming, before resin injection, independent or not). It may also be possible to have more injection steps than indicated. It may also be possible, even if a fibrous reinforcement is pre-impregnated, to combine it with a resin injection step. Preferably, a heating step (under controlled temperature and / or pressure) will follow a resin injection step for the resin to cross-link.The heating stage may be common to several resin injection stages.

[0179] The fibers may be simple fibers and / or strands of at least two strands (the general direction of the aforementioned fibers will then be the general direction of the strands) and / or braids of at least two strands (the general direction of the aforementioned fibers will then be the general direction of the braids).

[0180] Although here all the protective elements are flat, at least one of them may not be flat. For example, at least one of the protective elements may partially surround the body. For example, at least one of the protective elements may surround at least part of a lateral side of the body (in addition to being opposite at least one longitudinal side of the body).

[0181] Although here the protections are defined such that the general direction of their weft and / or warp fibers is inclined with respect to the general direction of the warp fibers of the central core and / or the peripheral belt, it may be otherwise. At least one of the protections may thus be defined such that The general direction of its warp and / or weft fibers may be inclined relative to a general loading direction to which the associated part and / or at least one of the protectors is subjected. This design may be defined such that the general direction of its warp and / or weft fibers is parallel or orthogonal to the general direction of the warp fibers of the central core and / or the peripheral belt. Although here all the fibers of the fibrous reinforcement of at least one of the protectors extend in a direction inclined relative to the longitudinal axis of the body X, at least a portion of the fibers of the fibrous reinforcement of at least one of the protectors may extend in a direction orthogonal or parallel to the longitudinal axis X.

[0182] For example, if the protection is formed of a stratification of several layers:

[0183] - for a first layer, some of the fibers will extend for the majority of they along a general direction C and the other part of the fibers will extend for the majority of them along a general direction D which is orthogonal to the general direction C;

[0184] - for a second layer, part of the fibers will extend for the majority of they along a general direction E (optionally parallel to the general direction D or to the general direction C) and the other part of the fibers will extend for the majority of them along a general direction F which is orthogonal to the general direction E;

[0185] Etc. ;

[0186] With the different general directions (C, D, E, F, ...) inclined and / or parallel and / or orthogonal with respect to the longitudinal axis X.

[0187] Regardless of the configuration of the protections observed, the general direction(s) may be parallel to each other from one protection to another or may not be parallel to each other.

[0188] It is recalled that the "general direction" is the direction in which the majority of the considered fibres extend.

[0189] The fiber material of the central reinforcement and / or peripheral reinforcement and / or at least one of the protections may be different from what has been indicated.

[0190] Similarly, the resin or resins used may be different from what has been indicated.

[0191] At least one of the inserts may be covered by at least one of the protectors (so that its flange will then rest on an external face of the body) or may not be covered by said protection (so that its flange will then rest on an external face of the protection directly).

[0192] For the purposes of this application, "bonding" means both bonding with adhesive and bonding without adhesive.

[0193] Although here the first axis A and the second axis B are parallel to each other, the two axes A and B may not be parallel to each other. The first axis A and / or the second axis B may not be orthogonal to the longitudinal axis X, contrary to what was described above.

[0194] Although here the second sub-preform 10 has a width similar or identical to that of the soles of the first sub-preform 4, the first sub-preform 4 and / or the second sub-preform 10 may be shaped differently. Thus, the second sub-preform 4 may be shaped to have at least one edge covering at least part of at least one longitudinal face of the first sub-preform 3. The second sub-preform 4 may therefore include at least one section whose cross-section is shaped into an L or a U (the orientation of the L or U not being fixed with respect to the longitudinal axis of the first sub-preform), the bar(s) of the L or U forming an edge covering at least part of at least one longitudinal face of the first sub-preform 3. The protection may then not cover said part of said longitudinal face.

Claims

Demands

1. Preform of a mechanical part, the preform comprising at least: - A first sub-preform (4) forming a core of the preform, the core comprising a fibrous reinforcement which is formed at least in part from an assembly of fibers, - A second sub-preform (10) forming a belt of the preform, the belt comprising a fibrous reinforcement which is formed at least in part from an assembly of fibers, the second sub-preform externally surrounding the first sub-preform, the first sub-preform and the second sub-preform together forming a body (5) extending longitudinally along a given axis (X) and provided at a first end with at least one first orifice (2, 3) and at a second end with at least one second orifice (2, 3), each orifice opening onto two opposite longitudinal faces of the body, characterized in that the preform comprises at least one protection (13) of at least a part of the preform,the protection comprising a fibrous reinforcement which is formed at least in part from an assembly of fibers, the protection being capable of covering at least an area of ​​at least one of the longitudinal faces of the body at an interface between the first sub-preform and the second sub-preform.

2. Preform according to claim 1, wherein at least a portion of the fibers of the fibrous reinforcement of the protection (13) extends in an inclined direction at a given angle (a) with respect to the given axis (X) when the protection is in place against the body.

3. Preform according to any one of claims 1 to 2, wherein the protection (13) is shaped to cover at least the entire area of ​​the longitudinal face of the body forming the interface between the first sub-preform (4) and the second sub-preform (10).

4. Preform according to any one of the preceding claims, wherein the fibrous reinforcement of at least one of the core, belt or guard (13) is formed at least in part by a weave of fibers.

5. Preform according to any one of the preceding claims, wherein the fibrous reinforcement of at least one of the core, belt or guard (13) comprises carbon fibers.

6. Preform according to any one of the preceding claims, wherein the fibrous reinforcement of at least one of the core, belt or guard (13) is a three-dimensional assembly of fibers.

7. Preform according to any one of claims 1 to 6, wherein the fiber assembly of the fibrous reinforcement of the protection (13) is densified by a resin, the protection thus being made of composite material and intended to be fixed to the body (5).

8. Preform according to any one of claims 1 to 7, wherein at least the protection (13) is formed at least in part by a laminated composite.

9. Preform according to any one of the preceding claims, wherein the protection (13) is a first protection and the longitudinal face of the body is a first longitudinal face of the body, the preform comprising at least a second protection (14) of at least one other part of the preform, the second protection comprising a fibrous reinforcement which is formed at least in part of an assembly of fibers, the second protection being able to cover at least one other area of ​​at least a second of the longitudinal faces of the body at an interface between the first sub-preform and the second sub-preform.

10. Mechanical part comprising a preform according to one of the preceding claims, the first sub-preform (4), the second sub-preform (10) and at least one protection (13) being bonded together and all densified by at least one resin.

11. Part according to claim 10, wherein the part is a connecting rod of a lander strut.

12. Landing gear comprising a part according to one of claims 10 or 11.

13. A method for manufacturing a mechanical part according to claim 10 or claim 11, comprising at least one step of assembling fibers for the creation of the fibrous reinforcement of the belt, core and at least one protection, and at least one step of densifying the fibrous reinforcements with at least one resin.

14. A manufacturing method according to claim 13, comprising: - a single step of assembling the fibers so as to form a single-piece fiber blank jointly forming the fiber reinforcement of the core and the fiber reinforcement of the belt and the fiber reinforcement of at least one protection (13); - a single step of densification of the fiber blank comprising the successive phases of: • Impregnating the fiber blank with a matrix-forming resin, • Polymerizing the assembly formed from the fiber blank and the resin.

15. A manufacturing method according to claim 13, comprising the successive steps of: - Making the fiber reinforcement of the core and the belt separately or together, - Impregnating the fiber reinforcement of the core and the fiber reinforcement of the belt in the same mold with a matrix-forming resin, - Polymerizing the assembly formed of the two fiber reinforcements and the resin, - Fixing at least one protection (13) to the assembly formed.

16. A manufacturing method according to claim 15, wherein the attachment of at least one protection (13) to the assembly formed comprises at least the following steps: - Attaching at least one protection to the assembly formed, the at least one protection being in the form of a pre-impregnated and / or dry assembly, - Impregnating the assembly of the assembly and the at least one protection with a matrix-forming resin, - Polymerizing the assembly of the assembly formed and the at least one protection.

17. A manufacturing method according to claim 13, wherein the attachment of at least one protection to the assembly formed is carried out by screwing and / or gluing.

18. A manufacturing method according to claim 13, comprising at least the steps of: - Separately forming the fibrous reinforcement of the core, the belt and at least one protection (13), - Bringing said three reinforcements into the same mold, - Impregnating said three assemblies with a matrix-forming resin, - Polymerizing the assembly formed by these three assemblies.