METHOD FOR PRODUCING A BENT PART MADE OF COMPOSITE MATERIAL AND CORRESPONDING BENT PART

Abstract

A bent structured element and a method for producing a bent structural element comprising a first portion extending in a first direction, a second portion extending in a second direction, and a curved joining portion connecting the first portion to the second portion. The production of the bent structural element includes the production of superimposed plies by applying unidirectional continuous fibers extending longitudinally from the first portion to the second portion, and the winding of a tie around the plies in the joining portion. The bent part and a method for producing a bent part is provided comprising the production of at least two bent structural elements, and the assembly of the at least two bent structural elements in order to form the bent part.

Claims

1. Method of producing a bent structural element having a first portion extending in a first direction, a second portion extending in a second direction, and a curved joining portion connecting the first portion to the second portion characterized in that the production of the bent structural element comprises: the production of superimposed plies by applying continuous unidirectional fibers extending longitudinally from the first portion to the second portion, and the winding of a tie around the plies in the joining portion.

2. Method according to claim 1, wherein each ply is formed by applying one or more bands onto a laying up surface or onto bands of the preceding ply, each band being formed of one or more fibers.

3. Method according to claim 1, wherein the width-to-thickness ratio (W/T) of the bent structural element is at most equal to 1, and preferably at most equal to , more preferably at most equal to .

4. Method according to claim 1, wherein the winding of the tie is made at 90 to the orientation of the fibers.

5. Method according to claim 1, wherein each ply is produced without curvature in the plane of the fiber.

6. Method according to any one of the preceding claims, characterized in that the plies are made by application by contact, by means of an application roller.

7. Method according to claim 1, wherein the plies are made by the application of continuous unidirectional fibers onto the lay-up surface of a laying up tool having a convex portion corresponding to the concavity of the desired structural element before winding.

8. Method according to claim 1, wherein the tie is formed of one or more fibers and/or one or more threads.

9. Method according to claim 1, comprising the production of additional plies onto the existing plies by application of continuous unidirectional fibers outside the joining portion.

10. Method for producing a bent part, wherein it comprises the production of at least two bent structural elements according to claim 1, and the assembly of at least two said bent structural elements to form the bent part.

11. Method according to claim 10 wherein the assembly of at least two said bent structural elements is carried out so that the bent structural elements are edge-to-edge.

12. Method according to claim 11, including the winding of a tie around at least two edge to edge bent structural elements.

13. Method according to claim 1, wherein the assembly of at least two said bent structural elements is carried out in such a way that bent structural elements are mounted on an assembly support.

14. Bent structural element comprising a first portion extending along a first direction, a second portion extending along a second direction, and a curved joining portion connecting the first portion to the second portion, characterized in that it comprises: plies superimposed by application of continuous unidirectional fibers extending longitudinally from the first portion to the second portion, and a tie wound around the plies in the joining portion.

15. Bent part comprising at least two bent structural elements according to claim 14 assembled by assembly means to form the bent part.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1 represents a schematic perspective view of an example of a bent structural element obtained after a first step of the method according to the invention;

[0042] FIG. 2 represents a schematic perspective view of the bent structural element of FIG. 1 after a second step of the method according to an embodiment of the invention;

[0043] FIG. 3 represents a schematic perspective view of the bent structural element of FIG. 2 after a third step of the method according to an embodiment of the invention;

[0044] FIG. 4 represents a schematic perspective view of a bent part obtained following the assembly edge to edge of bent structural elements obtained following the second step or the third step of the method according to an embodiment of the invention;

[0045] FIG. 5 represents a schematic perspective view of a bent part obtained following the assembly onto an assembly support of the bent structural elements obtained following the second step or the third step of the method according to an embodiment of the invention;

[0046] FIG. 6 is a schematic side view illustrating the laying up operation of a bent structural element;

[0047] FIG. 7 is a partial and schematic cross section of the hull of a boat with a foil made from the method of an embodiment of the invention;

[0048] FIG. 8 represents a schematic section of the foil along the cutting plane VIII-VIII of FIG. 7, the foil being produced according to a first embodiment of the invention;

[0049] FIG. 9 represents a schematic perspective view of a section of the foil in FIG. 8;

[0050] FIG. 10 represents a schematic section of the foil along the cutting plane VIII-VIII of FIG. 7, the foil being produced according to a second embodiment of the invention; and

[0051] FIG. 11 represents a schematic side view of a bent structural element before winding, used for the foil in FIG. 10.

DETAILED DESCRIPTION

[0052] FIG. 1 illustrates an example of bent structural element 10 obtained after a first step of the method according to the invention. The bent structural element 10 has an L shape and comprises a first portion 11 extending along a first elongation direction X, a second portion 13 extending along a second elongation direction Z, the second portion 13 being connected to the first portion 11 by a curved joining portion 12.

[0053] The joining portion 12 has a sharp curvature effecting the transition between the first direction X and the second direction Z, these first and second directions being orthogonal to each other.

[0054] The bent structural element 10 consists of superimposed plies 101, 102. Each ply is formed of a band comprising a single continuous fiber having a flat ribbon shape of constant width and extending in the first direction X in the first portion 11 and along the second direction Z in the second portion 13. In the joining portion 12, the fiber follows the curvature. The bent structural element has two opposing lateral faces 103, which are here substantially planar, a concave inner face 104 and a convex outer face 105.

[0055] According to another embodiment, the bent structural element 10 has a general V shape, the joining portion connecting the first portion and the second portion so that the first portion and the second portion form an angle less than 90, or a general flared V shape, the first portion and the second portion then forming an angle greater than 90.

[0056] Each ply is made without curvature in the plane of the fiber, along a path whose projection in a plane tangent to the ply is rectilinear. That is to say that the plies are made by laying up without steering according to the English term commonly used by those skilled in the art. The absence of steering is for example obtained by orienting the fibers along an orientation forming at any point an angle of 90 with the fillet line or axis of curvature of the joining portion.

[0057] According to another embodiment, the first and second directions are not orthogonal to the axis of curvature of the joining portion, the fibers being inclined in relation to said axis of curvature.

[0058] The plies are superimposed in the thickness E of the bent structural element 10. The thickness is therefore orthogonal to the plane of the fibers and corresponds to the distance between the inner face 104 and the outer face 105. In the example of the figure, the width L of the bent structural element merges with the width of the fibers which constitute it and corresponds to the distance between the lateral faces 103. The smaller the width-to-thickness (W/T) ratio, the more the force resulting from the tension applied during winding is exerted in the direction of the compaction of the plies between them and therefore the more the resultant force counteracts the delamination or detachment of plies. For example, the width to thickness ratio is .

[0059] As a variant, each ply comprises one or more bands, each band comprising one or more fibers.

[0060] FIG. 2 illustrates the bent structural element 10 after a second step of the method according to the invention. At the end of the second step, the bent structural element 10 further comprises a tie 120 wound around the plies 101, 102 in the joining portion 12. The tie is wound substantially along the radius of curvature so as to be at 90 to the orientation of the plies. In a variant, the tie is furthermore wound at +/45 to the orientation of the plies on either side of the joining portion 12.

[0061] The tie is wound under tension so as to exert a compaction force on the plies in order to limit the delamination or detachment of the plies. For example, winding is performed by means of a winding machine, applying a tension ranging between 2 daN and 10 daN, preferably 5 daN to 10 daN.

[0062] The tie 120 is formed of one or more fibers and/or one or more threads. The winding is for example made with a tie consisting of a fiber pre-impregnated with a thermoplastic polymer, identical to that used to make the plies, the winding comprising for example four superimposed layers or plies, and is achieved by applying heat in order to obtain an in situ consolidation of the polymer.

[0063] FIG. 3 illustrates the bent structural element 10 after a third step of the method of the invention. At the end of the third step, the bent structural element 10 further comprises additional plies on the existing plies through the application of continuous unidirectional fibers outside the joining portion. The addition of additional plies makes it possible to fill the break in alignment introduced in the bent structural element 10 by the wound tie, in particular on its lateral faces 103 and/or its outer face 105.

[0064] One or more additional plies 112, 132 are made on each lateral face 103, firstly in the area of the first portion 11, and secondly in the area of the second portion 12, these additional plies being laid at 90 to the plies resulting from the first step. The fibers of these additional plies 112 of the first portion are here laid in the first direction X, and the fibers of these additional plies 132 of the second portion are laid in the second direction Z, each ply being for example formed of a band of four fibers. As a variant, the fibers of the additional plies of the first portion are laid in the second direction Y, and the fibers of the additional plies of the second portion are laid in the first direction X.

[0065] One or more additional plies 111, 131 are made on the outer face 105 firstly in the area of the first portion 11, and secondly in the area of the second portion 12, these plies, each formed of a fiber are parallel to the plies from the first step.

[0066] Following the subsequent use of the bent structural element, additional plies can also be provided to compensate for the break in alignment on the inner face 104.

[0067] According to an alternative embodiment, the aforementioned additional plies are made after the completion of the plies of the first step, and before winding.

[0068] FIG. 4 illustrates a bent part 1 obtained following the assembly edge-to-edge of bent structural elements 10a, 10b, 10c obtained following the second step or the third step of the method according to embodiments of the invention. The assembly of the bent structural elements is made by mechanical assembly, for example by transverse bolting, bonding or by thermo welding. Additional plies 112, 132 on each lateral face facilitate the edge-to-edge assembly of the bent elements. As an alternative to the additional plies, the spaces between the bent structural elements generated by the winding are filled with resin during assembly.

[0069] According to a particular embodiment of the invention not shown, the method comprises the winding of a tie around at least two edge-to-edge bent structural elements obtained from the second or third step of the method.

[0070] FIG. 5 illustrates a bent part 1 obtained following the assembly on an assembly support 2 of bent structural elements 10a, 10b, 10c obtained following the second step or the third step of the method according to the invention. The assembly support 2 constitutes a portion of the shell giving the bent part the desired aerodynamic or hydrodynamic shape, the shape having at least one curvature. The bent structural elements are mounted on the assembly support 2 by mechanical assembly for example by bolting, bonding or thermo welding. In the example, the bent structural elements are evenly distributed and positioned so that the joining portion of each bent structural element 10a, 10b, 10c matches the curvature of the bent part 1, the outer face 105 of the structural elements being arranged facing the concave inner face of the assembly support.

[0071] According to variants of the invention, a shell is added subsequently to an assembly of bent structural elements as described with reference to FIG. 4, or the shell is obtained by over moulding on the bent structural elements, the bent structural elements being for example positioned in an injection mold, a polymer then being injected into the mold to form the shell.

[0072] FIG. 6 illustrates the first step of the method according to the invention in the case where the plies are made through application by contact, by means of an application or compaction roller. The application by contact is conventionally called laying up by fiber placement. The plies of the continuous fiber are laid on the laying up surface or application surface 40 of a laying up tool 4, the laying up surface corresponding to the shape of the desired inner face 104 of the bent structural element to be laid up, the surface comprising two planar portions connected by a convex portion corresponding to the concavity of the inner face. In reference to FIG. 6, the laying up is carried out by means of a fiber placement head 3, known per se, allowing automatic lay-up by contact of bands formed of one or more fibers. The fibers F enter the head 3 in the form of two layers of fibers, and the head comprises a guiding system 31 for guiding the fibers towards the compaction roller 32 in the form of a band of fibers in which the fibers are arranged side by side, for example substantially edge to edge. The head comprises, on either side of the guiding system, cutting means 33 for individually cutting each fiber passing through the guiding system, blocking means 34 for blocking each fiber that has just been cut, and feeding means 35 to individually feed each fiber, in order to be able to stop and resume the application of a fiber at any time, as well as to choose the width of the band. The laying up of a band is achieved by relative movement of the head in relation to the layup surface of the draping tool. The head comprises for example a support structure (not shown) on which is mounted the guiding system and by which the head can be assembled to a displacement system, adapted to move the head in at least two directions perpendicular to each other. The head is for example designed to receive four fibers, and allow the application of bands of one to four fibers of 6.35 mm ( inch) wide.

[0073] For example, the head is used for the production of bent structural elements, from fibers pre-impregnated with a thermoplastic polymer. The fibers are for example flat continuous carbon fibers, of the tows type, comprising a multitude of carbon threads or filaments, with a thermoplastic polymer present in quantity in the order of 40% by weight.

[0074] The head 3 is equipped with a heating system (not shown), for example of the IR lamp or laser type, in order to heat the polymer during the application of the fibers, and thus to allow at least an adhesion of the fibers of the different plies and ensure the cohesion of all the plies of the preform. The heating system heats the fibers before they are applied to the application surface, as well as the application surface or the fibers previously laid, upstream of the roller relative to the direction of advancement. Each structural element is for example formed of 100 superimposed plies, each ply being formed of one fiber. The fibers are oriented at 90 to the fillet or axis of curvature of the convex portion of the layup surface. To improve compaction via the compaction roller, shims can be added during laying up, on both sides of the laid plies, for example after each set of ten laid plies. During laying up, an in situ consolidation of the thermoplastic polymer is performed.

[0075] FIG. 7 represents an example of a boat 5 comprising a hull 6 equipped with foils 7, a hydrodynamic appendage of the hull of a sailing boat transmitting a lifting force to the hull so as to raise it up in relation to the surface of the water. The foil is made from a process according to the invention. In the example, the boat is a monohull sailing boat.

[0076] The foil 7 comprises two parts interconnected by a bend 702, a first part 701 constituting a lift plane and a second part 703 constituting a linking arm with the hull 6, ensuring during the operation of the boat the transmission of the forces of the righting moment and reducing the lateral motion of the boat.

[0077] FIG. 8 represents a section of the foil 7 along the cutting plane VIII-VIII of FIG. 7, the foil being made according to a first embodiment of the invention. The foil 7 comprises a bent structural part 71 formed of several bent structural elements 10a, 10b, 10c assembled edge to edge. The foil further comprises a core 72 and an outer skin or shell 73, for example obtained by over moulding from the bent part 71.

[0078] FIG. 9 represents the bent structural part 71 of the foil of FIG. 8. The bent structural part 71 comprises a first portion 711 at the first portion 701 of the foil 7, the first portion 711 consisting of all the first portions of the bent structural elements 10a, 10b, 10c assembled edge to edge. The bent structural part 71 further comprises a second portion 713 at the second portion 703 of the foil 7, the second portion 713 being constituted by all the second portions of the bent structural elements 10a, 10b, 10c assembled edge to edge. The bent structural part 71 also has a bent portion 712 at the bend 702 of the foil 7, the bent portion 712 being made up of all the joining portions of the bent structural elements 10a, 10b, 10c assembled edge to edge. For the sake of simplification, the foil illustrated here has a simple schematic L shape. The foil can of course be formed from bent structural elements whose first and second portions form an angle other than 90, and/or with a bent portion having a larger radius of curvature and/or whose first and/or second portions are extended by curved portions and/or planar portions.

[0079] FIG. 10 illustrates a section of the foil along the cutting plane VIII-VIII of FIG. 8, the foil 7 being made according to a second embodiment of the invention. The foil 7 comprises a bent structural part 71 formed as previously of several structural elements 10a, 10b, 10c. In reference to FIG. 11, each bent structural element comprises a first set of plies 106 of fibers and a second set of plies 107 of fibers between which is interposed a core 100. Each structural element is for example obtained by laying up the first set of plies 106 on a lay-up tool 4, such as described above with reference to FIG. 6, positioning a core 100 on this first set of plies, preferably with an assembly by bonding the core onto the first set, and by layup of the second set of plies 107 on the core. A winding of a tie is then performed in the area of the bent portion of this bent structural element.

[0080] These resulting bent structural elements, possibly preassembled between them edge to edge by bonding, are for example placed in an injection mold in which the core 72 and the shell 73 are made by over moulding by injection.

[0081] The core is for example formed of a thermoplastic polymer. The core can have a honeycomb structure combining lightness and robustness.

[0082] The invention is described in the above by way of example. It is understood that one skilled in the art is able to achieve different embodiments of the invention, by associating for example the different characteristics above taken alone or in combination, without departing from the scope of the invention.