WO2012104083A1

WO2012104083A1 - Device for producing a preform having at least one longitudinal segment of decreasing thickness, and device for positioning and compacting said preform

Info

Publication number: WO2012104083A1
Application number: PCT/EP2012/000454
Authority: WO
Inventors: Christophe Perrier; Françoise BALDACCI; Jean Christophe Ichard
Original assignee: Latecoere
Priority date: 2011-02-04
Filing date: 2012-02-02
Publication date: 2012-08-09
Also published as: FR2971196B1; FR2971196A1

Abstract

The invention relates to a method for producing a preform (P) which is formed by a stack of reinforcing layers of fibrous structure and which comprises at least one longitudinal segment (2) of decreasing thickness. According to the invention, the method comprises the following steps consisting in: pre-compacting the preform (P1, P2) to a pre-determined intermediate compression level with respect to the final compression level, assembling the layers of each longitudinal segment of decreasing thickness (2) along tufting lines formed over most of the surface of the longitudinal segment, and compacting the pre-compacted preform in order to obtain the final compression ratio.

Description

Device for producing a preform comprising at least one longitudinal section of decreasing thickness, and device for positioning and compacting this preform

The invention relates to a method for producing a preform formed of a stack of reinforcement layers with a fibrous structure and comprising at least one longitudinal section of decreasing thickness. It extends to a device for positioning and compacting a preform of the implementation of this method.

The composite materials composed, principally, of preforms formed by stackings of reinforcement layers with a fibrous structure, and of a matrix generally consisting of a plastic material (thermoplastic or thermosetting resin) ensuring the cohesion of the structure, are a job more and more frequent in many industries and especially in the aerospace industry.

Some of these parts made of composite materials require preforms having at least one longitudinal section of decreasing thickness. For this purpose, these preforms are formed of a stack of reinforcement layers with a fibrous structure and each longitudinal section of decreasing thickness is obtained by gradually decreasing the number of layers constituting said longitudinal section. In addition, the preforms are then compacted to a level of compression adapted so that each longitudinal section has a predetermined slope.

Each longitudinal section of decreasing thickness of these preforms consists of a connection section between a preform section of greater thickness and a lower thickness preform section, and one of the functions of this connection section is to allow the transmission of forces biasing the upper section section to the lower section section.

Such a transmission of effort makes it necessary to limit the slope of the connecting sections, and the rule currently in force imposes to limit this slope to a value of approximately 10%.

Such a rule however proves compelling because it leads for example to: limit, for a fixed length and therefore a fixed slope, the maximum ratio of the upper and lower sections,

- Achieving link sections of great length and therefore a significant weight when the ratio between upper and lower sections is important.

At present, the only solution proposed to overcome these disadvantages is to strengthen these preforms by using mechanical assembly means, such as rivets, but this solution is also very disadvantageous in terms of added weight.

The present invention aims at overcoming these drawbacks and its main objective is to provide a method for producing a preform comprising at least one longitudinal section of decreasing thickness, making it possible to significantly increase the maximum allowable value of the slope of such sections, and leading to a significant reduction in the weight of said sections.

For this purpose, the invention provides a method for producing a preform formed of a stack of reinforcement layers with a fibrous structure and comprising at least one longitudinal section of decreasing thickness, obtained by a gradual decrease in the number of layers constituting said longitudinal section, then compaction of the preform at a final compression level adapted so that the longitudinal section has a predetermined slope. According to the invention, this method is characterized in that:

the preform is pre-compacted to a predetermined intermediate compression level of the final compression level,

the layers of each longitudinal section of decreasing thickness are assembled by stitching lines formed over most of the surface of said longitudinal section,

and compacting the pre-compacted preform so as to obtain the final compression ratio.

According to this method, the mechanical properties of the decreasing thickness sections are increased by the presence of stitching lines (made according to the technique known as "tufting") formed so as to assemble the reinforcing layers. In addition, these stitching lines are made, according to the invention, after pre-compaction of the preform, so that the folding stitching son intervenes only during the final compaction phase and is therefore very limited. Thus, these son, intended to work in tension, have a very high reactivity guaranteeing in particular against any risk of crack propagation.

In practice, such a method makes it possible to significantly increase the maximum allowable value of the slope of such sections, and consequently to significantly reduce the weight of these sections,

As an indication, the allowable value of the slope of the sections made according to the method of the invention is of the order of 20%.

According to an advantageous embodiment of the invention, the preform is pre-compacted to a level of compression substantially between 60% and 70% of the final compression level.

In addition, the stitching lines are advantageously made substantially orthogonal to the slope of each longitudinal section.

These stitching lines are furthermore advantageously made by means of yarns having a high tensile strength, such as "Kevlar®" yarns or carbon yarns.

Moreover, according to another advantageous embodiment of the invention:

each longitudinal section is pre-compacted by means of parallel compaction strips extending substantially perpendicular to the slope of said longitudinal section,

a first series of stitching lines formed after removal of one of two compaction strips,

- And a second series of stitching lines is performed after replacing the compacting strips previously removed and removing the previously used compacting strips.

Thus, only strips of narrow width are released simultaneously for the realization of the stitching lines, so that the preform does not undergo "decompression" during these stitching operations. In addition, it is advantageous to use compacting strips adapted so that a predetermined width interval is formed between the neighboring compacting strips.

As will be better understood later, such an implementation makes it possible to achieve a greater number of tap lines per unit area without affecting the uniformity of pre-compaction.

Furthermore, the final compaction of each longitudinal section is advantageously carried out by means of pairs of compacting strips comprising a compacting strip identical to those used during the pre-compacting, and a compacting strip of width equal to the width of the strips of compacting. compaction used during pre-compaction plus the width of the gap between two compacting strips during said pre-compaction.

The invention extends to a device for positioning and compacting a preform formed of a stack of reinforcement layers with a fibrous structure and comprising at least one longitudinal section of decreasing thickness, comprising:

two trays defining conjugate surfaces of each of the faces of the preform, at least one of said trays comprising, for each longitudinal section of decreasing thickness of the preform, removable shutter elements of windows, adapted to allow the realization of stitching lines in the surface portions of the preform released during removal of said removable elements,

and means for relative displacement of the two plates. In addition, the removable shutter elements of the windows advantageously comprise, according to the invention, for each longitudinal section of the preform, compaction strips extending substantially perpendicular to the slope of said longitudinal section.

In addition, advantageously according to the invention the device comprises two sets of shutter strips windows:

a first set of compacting strips adapted to provide a predetermined width interval between each of said compacting strips,

and a second set of compacting strips composed of pairs of compacting strips comprising a compacting strip identical to those of the first set of compacting strips, and a compacting strip of width equal to the width of the compacting strips of the first set plus the width of the gap separating said compacting strips of the first set.

Other features and advantages of the invention will become apparent from the detailed description which follows with reference to the accompanying drawings which represent by way of non-limiting example a preferred embodiment. On these drawings:

FIG. 1 is a perspective view, in exploded mode, of a positioning and compacting device according to the invention and of the preform intended to be assembled and compacted by means of said device,

FIGS. 2 to 6 are perspective views showing successive closing steps of the positioning and compacting device according to the invention, and pre-compaction and compacting of a preform positioned in said device;

and FIG. 7 is a perspective view of a preform made by means of the positioning and compacting device according to the invention.

(For purposes of simplification of the description, the positioning and compacting device according to the invention is described, below, arranged on a horizontal support and the terms defining the orientation of the various constituent elements, such as horizontal, vertical ... are used with reference to such a provision).

The method according to the invention is illustrated by taking as an example the production of a preform P as described in the patent application FR 2 928 620, forming one of the end pieces of the longitudinal members of an aircraft cabin door. formed of the juxtaposition of two identical elementary preforms P1, P2. Each of these elementary preforms P1, P2 is formed of a stack of reinforcement layers with a fibrous structure and has a first rectangular portion 1 of constant thickness, extended laterally by a second rectangular portion 2 of decreasing thickness, having, along its junction edge with the first portion 1, a maximum thickness greater than that of said first portion, forming a shoulder 3 with the latter. Once superimposed, these two elementary preforms P1, P2 are adapted, as shown in FIG. 7, to form a preform P comprising a first section composed of the first portions 1 of the elementary preforms P1, P2 delimiting a recess 4, and a second section consisting of second rectangular portions 2 and having the shape of a point of isosceles triangular section.

The positioning and compaction device according to the invention shown in FIGS. 1 to 6 comprises two vertical flanges 5a, 5b between which, in the first place, a support plate 6 of rectangular shape conjugates with that of the first section 1, 4 of the preform P, adapted to support the latter.

This support plate 6 is mounted so as to be able to be displaced vertically, and for this purpose it is extended longitudinally, on either side, by two pins such as 7, 8 housed in vertical grooves as 9 formed in the flanges 5a, 5b.

In addition, this support plate 6 is pierced, substantially at each of its vertices, with an orifice such as 10, 11 in the extension of each of which is secured, in the underside of said support plate, a nut 12 of conjugated internal diameter of said orifices.

The device according to the invention also comprises two rectangular trays 13, 14, said lower and upper, articulated around a horizontal axis 15 extending between the two flanges 5a, 5b, and secured to them.

Each of these plates 13, 14 has the shape of a frame whose longitudinal uprights are connected by cross members such as 20 delimiting three identical substantially square windows 17-19.

In addition, each of these plates 13, 14 has a rebate 16, the rebate of the lower plate 13 being adapted to cooperate with a rabbet (not shown) of the support plate 6 so that the support plate assembly 6 / lower plate 13 has a dihedral-shaped upper face adapted to support the elementary preform P1.

The device according to the invention also comprises an intermediate profile 21 T-shaped adapted to extend between the two flanges 5a, 5b and to be secured to them. Each of these profiles 21 comprises a core 22 of shape adapted to be positioned in the recess 4 of the preform P, and a stiffening wing 23, the said core and wing being pierced longitudinally with threaded blind holes such as 24 for their fastening to the flanges 5a, 5b by means of bolts such as 25.

In addition, the core 22 is also pierced, substantially at each of its peaks, with an orifice such as 26, 27 arranged to extend axially with the orifice 10, 11 formed vis-à- screw in the support plate 6.

The positioning and compaction device further comprises an upper plate 28 of rectangular shape conjugate to that of the first section 1, 4 of the preform P, adapted to cover the latter.

This upper plate 28 is mounted so that it can be moved vertically, and, for this purpose, it is extended longitudinally, on either side, by two pins such as 29, 30 housed in vertical grooves 31, 32 formed in the flanges 5a, 5b.

In addition, this upper plate 28 is also pierced, substantially at each of its peaks, with an orifice such as 34, 35 arranged to extend axially with the orifices 10, 11, 26, 27 arranged in in the support plate 6 and the intermediate section 21.

This upper plate 28 has, finally a rebate 33 adapted to cooperate, as shown in the detail view of Figure 2, with the rabbet 16 of the upper plate 14 in the position of the latter closed on the lower plate 13, so the upper plate assembly 28 / upper plate 14 has a dihedral-shaped bottom face adapted to cover the elementary preform P2.

In order to cause a simultaneous displacement of the support plate 6 and the upper plate 28 tending to bring them together and to cause simultaneous pivoting of the two plates 13, 14, the device comprises bolts such as 36, 37 adapted for s extend in the orifices 10, 11, 26, 27, 34, 35 and to cooperate with the bolts 12 fixed under the face of the support plate 6.

Although the displacement means described above are strictly manual, it is obvious that this movement can it can also be generated by motorized moving means with manual control or with numerical control ...

Finally, the device according to the invention comprises compacting strips adapted to extend in the windows 17-19 of the two plates 13, 14 and to be fixed on the crosspieces 20 of said plates by means of screws such as 41 fastening the compacting strips in threaded bores formed in said sleepers.

Two sets of compacting strips are provided according to the invention, intended to perform respectively a first pre-compacting action and a final compaction action.

The first set of compaction strips shown in Figures 1 to 5 consists of strips of the same width 38-40 adapted for a constant width interval is formed between the neighboring compacting strips.

The second set of compaction strips shown in Figure 6 consists of pairs of compacting strips with a compacting strip 38-40 identical to those of the first set of compacting strips, and a compacting strip 42-44 of equal width. to the width of compacting strips 38-40 of the first set plus the width of the gap separating the said compacting strips from the first set.

This second set of compacting strips is therefore adapted so that the compacting strips completely close the windows 17-19 in which they are arranged.

In order to implement the method according to the invention, the first set of compacting strips 38-40 is fixed in the windows of the two plates 13, 14, then successively:

the preform P1 is positioned on the support plate 6 / lower plate assembly 13, in the open position of the upper plate 14,

the intermediate profile 21 is fixed between the flanges 5a,

5b,

the preform P2 is put in place on the intermediate profiled assembly 21 / preform P1, in the open position of the upper plate 14, the upper plate 14 is closed on the lower plate 13, and the upper plate 28 is put in place by introducing the pins 29, 30 into the grooves 31, 32 (FIG. 2),

- And the bolts 36, 37 are positioned in the orifices 10, 11, 26, 27, 34, 35 until they cooperate with the nuts 12.

Once these preliminary operations have been performed, the first step consists of a precompaction step represented in FIG. 3, obtained by screwing bolts 36, 37 by a determined number of steps adapted to compact the preform P at a compression level. substantially between 60% and 70% of the final compression level.

The next step consists, as shown in FIG. 5, in removing one of two compaction strips 38-40 in order to release, in the two plates 13, 14, strips of width in which stitching lines are made. .

The next step then consists in making a second series of stitching lines after replacing the compacting strips 38-40 previously removed and removing the compacting strips previously left in place.

All these stitching lines may, in addition, be through, when assembling a number of reinforcement layers less than a number of layers depending on the nature of the material forming the layers, the thickness of these layers. .., or not through when assembling a number of layers of reinforcement greater than this number of layers. The last step finally consists in replacing a compacting strip 38-40 of the first set of strips on two, by a compacting strip 42-44 of great width of the second set of strips, then to compact the preform P so as to obtain the final compression ratio.

Moreover, as an example intended to highlight the interest of making two sets of compacting strips according to the invention, the first set may consist of compacting strips 38-40 with a width of 10 mm spaced apart. an interval of 5 mm.

The second set consists of compacting strips 38-40 with a width of 10 mm and compacting strips 42-44 with a width of 15 mm. Such sets of ruler make it possible, in fact, to make stitching lines spaced 5 mm without risk of "decompression" of the preform P during the stitching operations, and without risk of "collision" between the stitching needle and the compacting strips.

Such a device according to the invention therefore makes it possible to significantly increase the maximum admissible value of the slope of the longitudinal sections of decreasing thickness of the preforms and thus leads, in particular, to a significant reduction in the weight and bulk of the said sections.

Claims

1 / A process for producing a preform (P) formed of a stack of reinforcement layers with a fibrous structure and comprising at least one longitudinal section (2) of decreasing thickness, obtained by a gradual decrease in the number of layers constituting the said longitudinal section, then compaction of the preform at a final compression level adapted so that the longitudinal section (2) has a predetermined slope, the said method being characterized in that:

the preform (P) is pre-compacted to a predetermined intermediate compression level of the final compression level,

the layers of each longitudinal section of decreasing thickness (2) are assembled by stitching lines formed over most of the surface of said longitudinal section,

and compacting the pre-compacted preform (P) so as to obtain the final compression ratio.

21 Process for producing a preform according to claim 1 characterized in that the preform (P) is pre-compacted to a level of compression substantially between 60 ° and 70 ° of the final compression level.

3 / A method of producing a preform according to one of claims 1 or 2, characterized in that one carries out substantially orthogonal tapping lines to the slope of each longitudinal section (2).

4 / A method of producing a preform according to claim 3 characterized in that:

- each longitudinal section (2) is pre-compacted by means of parallel compaction strips (38-40) extending substantially perpendicular to the slope of said longitudinal section,

a first series of stitching lines formed after removal of one compacting strip (38-40) out of two is carried out,

- And a second series of stitching lines is performed after replacing the compacting strips (38-40) previously removed and removing the compacting strips (38-40) previously used.

5 / A process for producing a preform according to claim 4, characterized in that compacting strips are used. (38-40) adapted so that a predetermined width interval is provided between the neighboring compacting strips.

6 / A method of producing a preform according to claim 5 characterized in that one carries out the final compaction of each longitudinal section (2) by means of pairs of compacting strips comprising a compacting strip (38-40) identical to those used during the pre-compaction, and a compacting strip (42-44) of width equal to the width of the compacting strips (38-40) used during the precompacting plus the width of the gap separating two strips of compacting (38-40) during said pre-compaction.

Method for producing a preform according to one of the preceding claims, characterized in that the stitching lines are produced by means of yarns having a high tensile strength, such as "Kevlar®" yarns or carbon threads.

8 / Device for positioning and compaction of a preform formed of a stack of reinforcement layers with a fibrous structure and comprising at least one longitudinal section (2) of decreasing thickness, characterized in that it comprises:

two plates (6, 13, 14, 28) defining conjugate surfaces of each of the faces of the preform (P), at least one of said plates comprising, for each longitudinal section of decreasing thickness (2) of the preform ( P), removable elements (38-40, 42-44) for closing windows (17-19), adapted to allow stitching lines to be produced in the surface portions of the preform (P) that are disengaged during the withdrawal. said removable elements,

and relative displacement means (12, 36, 37) of the two plates (6, 13, 14, 28).

9 / positioning and compacting device according to claim 8 characterized in that the removable shutter elements of the windows (17-19) comprise, for each longitudinal section (2) of the preform (P), compacting strips ( 38-40, 42-44) extending substantially perpendicular to the slope of said longitudinal section.

10 / positioning and compacting device according to claim 9 characterized in that it comprises two sets of shutter strips windows (17-19): a first set of compacting strips (38-40) adapted to provide a predetermined width interval between each of said compacting strips,

- and a second set of compacting strips (38-40, 42-44) composed of pairs of compacting strips comprising a compacting strip (38-40) identical to those of the first set of compacting strips (38-40) , and a compacting strip (42-44) of width equal to the width of the compacting strips (38-40) of the first set plus the width of the gap separating said compacting strips from the first set.