EP2552676A1

EP2552676A1 - Method for producing a mechanical member from composite material, having an improved mechanical performance under traction-compression and bending

Info

Publication number: EP2552676A1
Application number: EP11711283A
Authority: EP
Inventors: Richard Masson; Patrick Dunleavy
Original assignee: Messier Bugatti Dowty SA
Current assignee: Safran Landing Systems SAS
Priority date: 2010-03-26
Filing date: 2011-03-24
Publication date: 2013-02-06
Also published as: FR2957844B1; BR112012024389A2; US20130105079A1; JP2013523488A; CA2794411A1; RU2012144846A; CN102844171A; WO2011116967A1; FR2957844A1

Abstract

The invention relates to a method for producing a mechanical member made from a composite material, such as a connecting rod (19), comprising successive operations involving the application of layers of reinforcing fibres braided around a mandrel, and, between two reinforcing fibre layer application operations, a step comprising: the positioning of at least one element formed by pultruded reinforcing fibres (14'') oriented longitudinally (AX); and the at least temporary securing of each pultruded element (14'') to the last layer of braided reinforcing fibres. According to the invention, a resin is subsequently injected into the different braided layers prior to the polymerisation of said resin in order to form a raw connecting rod.

Description

METHOD FOR MANUFACTURING A MECHANICAL MEMBER IN COMPOSITE MATERIAL HAVING INCREASED MECHANICAL TENSION-COMPRESSION AND BENDING

The invention relates to a method for manufacturing a mechanical component such as an aircraft landing gear strut.

BACKGROUND OF THE INVENTION

It is known, in particular from the patent document FR2932409, to manufacture such a connecting rod from a mandrel on which one or more layers of carbon fibers are superposed radially on one another.

This assembly is then installed in a mold for injecting resin into the various layers carried by the mandrel before polymerizing this resin, for example by heating, to form a rigid raw rod that can be machined at its interfaces to form screeds.

The braiding of the reinforcing fiber layers is then ensured with a braiding installation which is represented in FIG. 1 by being marked with 1. This installation essentially comprises a ring 2 extending in a vertical plane, the axis of revolution AX of this ring is thus horizontal. This ring 2 carries a set of coils of reinforcing fibers 3, converging towards a region located on the axis AX and offset from the plane of the ring.

When the braiding cycle is started, the mandrel which is marked by 4 is moved along the axis AX to cross the ring 2 beyond the point of convergence of the fibers. At the same time, the coils carried on the ring 2 by motorized mobile supports are actuated to manufacture a sock of reinforcing fibers on the outer face of this mandrel 4.

This sock covers the. -mandrin on all his length once it has completely traversed the ring, that is to say once it is located beyond the point of convergence of the fibers.

The reinforcing fiber layer is then cut downstream of the mandrel, and the mandrel is disassembled and then placed behind the ring, in order to cross it again for the formation of a second layer of reinforcing fibers radially superimposed on the first.

Thus, as shown schematically in FIG. 2, it is possible to manufacture a general structure comprising in its central region the mandrel forming a support for two layers of braided fibers 6, 7, or more, which extend all around it and over any its length.

Concretely, as represented in FIG. 2, a braided layer comprises, on the one hand, said spindle fibers 8 and 9 which are inclined for example about thirty degrees on one side and the other with respect to the axis AX, and secondly longitudinal fibers 11, parallel to the axis AX, which are held in position by the spindle fibers 8 and 9 which interlace them.

In such a connecting rod, it is essentially the longitudinal fibers that support the mechanical stresses occurring when the link is biased in traction-compression along the axis AX, and when it is biased in bending about any axis normal to the axis AX .

Given the tension of the spindle fibers necessary for braiding, and contrary to the schematic representation of FIG. 3, the longitudinal fibers 11 are in fact corrugated instead of being straight, which penalizes the level of mechanical stresses they are able to support according to AX direction. This loss of resistance in the longitudinal direction is all the more important as the corrugation of the longitudinal fibers is high, since the tension applied to the fibers during the braiding must itself be important in order to ensure the greatest overall compactness possible.

OBJECT OF THE INVENTION

The object of the invention is to propose a solution to remedy this drawback.

SUMMARY OF THE INVENTION

For this purpose, the subject of the invention is a method for manufacturing a mechanical member made of a composite material, such as a rod made of composite material, comprising successive operations for applying reinforcement fiber layers braided all around a mandrel and over all or part of the length of this mandrel being superimposed radially to one another, comprising between two operations of application of braided reinforcing fiber layers, a step:

placing on the last layer of braided fibers at least one element formed of pultruded reinforcing fibers, each pultruded element being oriented longitudinally and extending over at least a portion of the length of the mandrel;

and at least temporarily attaching each pultruded element to the last layer of braided reinforcing fibers,

and wherein once all the pultruded elements have been put in place and all the braided layers have been applied, a resin is injected into the various braided layers before polymerizing the assembly to form a blank.

With this solution, the pultruded elements constitute a set of fibers which remain substantially rectilinear after assembly with the braided layers and after injection and polymerization of the resin, which significantly increases the mechanical strength in the longitudinal direction.

The subject of the invention is also a method as defined above, in which each pultruded element is of the solid rod type.

The invention also relates to a method as defined above, in which the fixing of each pultruded element applied against the same layer of reinforcing fibers is provided with a product of glue or resin type.

The subject of the invention is also a method as defined above, in which the fixing of each pultruded element applied against the same layer of reinforcing fibers is ensured with a link passed around the assembly formed by the mandrel with the layers. he wears and pultruded elements to fix.

The subject of the invention is also a process as defined above, in which a plurality of pultruded elements which are regularly spaced from each other around the longitudinal direction of the mandrel are applied against the same layer of braided fibers.

The invention also relates to a method as defined above, in which different pultruded elements are assembled by connecting them to each other by one or more transverse links to form a rack-type assembly, before setting up this system. assembly on the same layer of reinforcing fibers.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a schematic representation showing in perspective a known braiding machine with a mandrel for receiving a layer of braided fibers;

FIG. 2 is a diagrammatic cross-sectional view showing the layers constituting a connecting rod of known composite material;

Figure 3 is a schematic view showing a portion of braided reinforcing fibers shown in perspective;

Figure 4 is a schematic cross-sectional view of a cylindrical section rod body manufactured according to the method according to the invention;

Figure 5 is a schematic cross-sectional view of an elliptical cross-section body manufactured in accordance with the method according to the invention;

Figure 6 is a perspective view of a finished rod made of composite material manufactured with the method according to the invention;

Figure 7 is a longitudinal sectional view of a rod made of composite material manufactured according to the method according to the invention;

Figure 8 is a schematic view of an assembly of pultruded elements before placement and attachment to a braided layer.

DETAILED DESCRIPTION OF THE INVENTION

The idea underlying the invention is to use a braiding manufacturing process in which prepolymerized or polymerized rectilinear rods, formed of pultruded reinforcing fibers, are integrated by placing them longitudinally between the consecutive braided fiber layers. Thus, longitudinal rods are integrated into the connecting rod which are perfectly rectilinear and thereby significantly increase the mechanical strength of the connecting rod in tension-compression and bending.

The pultruded profiles are industrially manufactured constant section composite sections in a continuous process. Concretely, the fibers in the form of coils are unrolled continuously to be impregnated with resin before passing through a heated die polymerizing or prepolymerizing this resin, so as to continuously form a rigid section which is cut portions length desired over the production.

These pultruded profiles are in particular in the form of solid or hollow rods consisting of parallel rectilinear reinforcing fibers being agglomerated to each other by the polymerized or prepolymerized resin. The mechanical strength of the pultruded profiles is important along the main axis of the profile for a very competitive manufacturing cost.

The invention thus consists in integrating pultruded elements between the braiding of reinforcing fiber layers, with an installation of the type shown in FIG. 1 in order to manufacture a connecting rod.

As shown diagrammatically in FIG. 4, a connecting rod manufactured in accordance with the invention thus comprises a mandrel 12, which here has a circular section, around which a layer of reinforcing fibers 13 is braided by passing through a braiding installation such as that of the figure 1.

Once this braid 13 has been applied over the entire length of the mandrel 12, that is to say once the mandrel has passed through the plane of the ring carrying the reinforcing fiber coils, the installation is stopped. The reinforcing fiber layer is then cut downstream of the mandrel, and the assembly formed by the mandrel 12 and the layer 13 that it carries are removed to be installed again upstream of the ring carrying the coils, with a view to braiding a new layer of reinforcing fibers.

At this stage, the pultruded elements 14 are placed on the layer 13, so as to extend longitudinally, that is to say parallel to the axis AX of the connecting rod, being regularly spaced from each other. others around this AX axis. These pultruded elements can be fixed by previously applying a product of the glue or resin type on the layer 13.

Another solution as regards the fixing of the pultruded elements consists in surrounding the assembly with a reinforcing fiber bond, so as to grip these elements against the outer face of the layer 13.

Once the pultruded elements have been put in place and they are held in position in a stable manner, the following reinforcing fiber layer 16 is braided. This braiding is ensured by moving the assembly formed by the mandrel 12, the braided fiber layer 13, and the pultruded elements 14 through the ring of the braiding installation, along the axis of this ring.

This operation has the effect of forming a layer of braided fibers which then surrounds the pultruded elements 14 by enclosing them without significantly changing their position. During the braiding operation of the layer 16, the elements 14 remain oriented longitudinally and regularly spaced from each other along the circumference of the layer 13.

Under these conditions, and as shown schematically in Figure 4, the elements 14 are then firmly gripped between the layers 14 and 16, and they are oriented longitudinally along the axis AX.

At this stage, the assembly formed by the mandrel 12, the layers 13 and 16 and the pultruded elements interposed between these layers, is installed in a mold for injecting resin through the layers of reinforcing fibers 14 and 16. When the pultruded sections are hollow rods, their ends are closed to prevent these rods from filling with resin during the injection phase.

A heating cycle is then triggered to polymerize this resin, to form a rigid raw link whose interfaces can then be machined by drilling to form screeds, before mounting in these holes metal rings.

FIG. 4 shows only a set of pultruded elements 14 interposed between two braided layers 13 and 16. However, the method according to the invention makes it possible to interpose between each pair of consecutive braided layers a set of elements pultruded for a generally increase the mechanical strength in traction-compression and bending of this rod, and thereby its resistance to buckling.

The pultruded elements 14 do not necessarily have to be distributed over the entire circumference of the braided layer which carries them, but they can advantageously be arranged only in certain zones of this circumference, without necessarily being regularly spaced from each other.

Thus, in the example of FIG. 5, the mandrel 12 'has a section which is elliptical instead of circular, to constitute a connecting rod having increased flexural strength around the minor axis of the ellipse corresponding to its section. . The resistance in traction-compression is also increased in this rod.

In this case, the first layer 13 'is braided around the mandrel 12', as for the example of FIG. 4. Pultruded elements 14 'are then placed only at the opposite ends which are furthest from this ellipse. , so as to increase the resistance to bending stress around the minor axis of this ellipse.

The next layer 16 'is then braided, before proceeding to the establishment of other pultruded elements 17', which are also placed at the level of ends of this ellipse that are furthest apart from each other. A new braided layer 18 'is then applied before proceeding with the resin injection in the assembly and its polymerization.

The pultruded elements extend essentially along the body of the connecting rod which is indicated by 21 in FIG. 6 where this connecting rod is shown in its finished state. This body 21 corresponds to the central region of the connecting rod 19, which is a wall of regulated type, this body 21 having for example a constant section.

However, the pultruded elements can marry substantially curved shapes, because their rigidity is relatively important allows them to marry these forms while curving as little as possible. In other words, these pultruded elements can be placed on curved shapes and their rigidity ensures that they adopt shapes that are not curved enough to offer high mechanical strength.

The pultruded elements marked here by 14 "are arranged radially in the form of three layers, but they do not cover a priori the ends 22 and 23 of the connecting rod 21, that is to say the interfaces of this rod, because these ends have highly scalable unregulated sections not suitable for the application of rectilinear elements.

Thus, as can be seen in FIG. 7, the pultruded elements 14 are radially distributed over three layers each interposed between two braided layers, but these elements are integrated into the connecting rod while extending only between the ends 22 and 23 of this connecting rod .

In the examples described in support of FIGS. 4 and 7, the pultruded elements can be applied and held one by one on the braided layer which makes them carry. But advantageously, the pultruded elements 14, 14 ', 14'',17' can be prepared prior to their application to form a rack type assembly shown schematically in FIG. 8.

In this case, the pultruded elements are for example arranged flat parallel to each other being spaced regularly from each other, and they are secured to each other by means of several pairs of reinforcing fibers 24 regularly spaced from each other along these elements.

Each pair 24 then comprises two fibers generally oriented in a direction perpendicular to the general direction of the pultruded elements, and these two fibers are interwoven around each pultruded element, which makes it possible to secure these elements to each other while keeping them parallel and spaced two by two from a predetermined distance.

The establishment of the elements pultruded on a layer of braided fibers consists of grasping the rack thus formed, to apply it to the outer face of the layer in question, and to stick to it, or to surround the whole with one or more circumferential reinforcing fiber bonds.

In the example of the figures, the rod manufactured according to the method according to the invention comprises two interfaces, which are here two screeds. But the invention applies equally well to other types of rods such as landing gears that have an interface at each of their ends and a third interface located between these ends.

Furthermore, the example of the figures illustrates the implementation of the invention for the manufacture of a rod of composite material. But the invention applies to the manufacture of other types of mechanical members, as for example the manufacture of carbon blades of an aircraft propeller, or the manufacture of a carbon mast intended to equip a sailboat.

Indeed, the blades of a propeller as well as the mast of a sailboat are subject to mechanical stresses oriented mainly according to their main direction, that is to say the direction of pultruded elements that are integrated, so that the method according to the invention then offers a significant increase in the mechanical strength for this type of mechanical member.

Claims

1. A method of manufacturing a mechanical member of composite material, such as a rod (19) of composite material, comprising successive operations of applying layers (13, 16; 13 ', 16', 18 ') of reinforcing fibers braided all around a mandrel (12; 12 ') and over all or part of the length of this mandrel (12; 12') being superposed radially to one another, comprising between two layers application operations (13, 16; 13 ', 16', 18 ') of braided reinforcing fibers, a step:

placing on the last layer of braided fibers (13; 13 ', 16') at least one element formed of pultruded reinforcing fibers (14; 14 ', 17'; 14 ''), each pultruded element; being oriented longitudinally (AX) and extending over at least a portion of the length of the mandrel (12; 12 ');

and at least temporarily attaching each pultruded element (14; 14 ', 17'; 14 '') to the last layer of braided reinforcing fibers,

and wherein after all the pultruded elements have been put into place and all the braided layers (13, 16; 13 ', 16', 18 ') have been applied, a resin is injected into the various braided layers (13). , 16; 13 ', 16', 18 ') before polymerizing the assembly to form a blank.

The method of claim 1, wherein each pultruded member (14; 14 ', 17'; 14 '') is of the solid rod type.

3. Method according to claim 1 or 2, wherein the fixing of each pultruded element (14; 14 ', 17'; 14 '') applied against the same layer of reinforcing fibers is provided with a product of glue or resin type.

4. Method according to claim 1 or 2, in the fixing of each pultruded element (14; 14 ', 17'; 14 ¹ ') applied against the same layer of reinforcing fibers is ensured with a link passed around the assembly constituted by the mandrel (12; 12') with the layers it carries and the pultruded elements to be fixed (14; 14 ', 17'; 14 * *).

5. Method according to one of claims 1 to 4, wherein is applied against a same layer of braided fibers (13, 16; 13 ', 16', 18 ') several pultruded elements (14; 14', 17 '; 14 '') which are regularly spaced from each other about the longitudinal direction (AX) of the mandrel (12; 12 ').

6. Method according to one of claims 1 to 5, wherein assemble different pultruded elements (14; 14 ', 17'; 14 '') by connecting them to each other by one or more transverse links to form an assembly type rack, before putting this assembly on the same layer of reinforcing fibers.