FR3050682A1 - PROCESS FOR PRODUCING THE SELF-ARRAYING COMPOSITE STRUCTURE, IMPLEMENTATION EQUIPMENT AND CORRESPONDING MONOBLOCK PIECE - Google Patents

Abstract

The invention aims to achieve, in a single operation, a self-stiffened laminate structure and substantially free of porosity to form complex parts, large and can integrate multiple stiffening functions. To do this, it is proposed to use a multiple natural drainage of the resin in each elemental area of a mesh of the skin configuration developed from an estimate of the permeability. According to one embodiment, equipment for implementing the method for producing a self-stiffening structure according to the invention comprises a counter-form (9) in which resin injection channels (4) are cut. The counter-form (9) rests on elementary infusion zones (2, 20a, 20b) which incorporate stiffeners (Ra, Rb) associated with the skin (1) and is covered in a sealed manner by a flexible bladder (10) evacuation. The injection channels (4) and connecting slots (4f) are cut in the counterfoil (9) in line with the median lines (5, 5a, 5b) of the elementary zones (2, 20a, 20b). Reinforcement interfaces (8a, 8b) define the boundaries between the elementary zones (2, 20a, 20b).

Description

METHOD FOR MAKING SELF-ARRAY COMPOSITE STRUCTURE, IMPLEMENTATION EQUIPMENT AND CORRESPONDING MONOBLOCK PART

DESCRIPTION

TECHNICAL AREA

The invention relates to a method of producing a self-stiffening structure of composite material, to an equipment for implementing such a method, and to a monobloc part formed from such a structure.

[0002] A self-stiffened composite structure is generally composed of a basic laminated structure comprising one or more composite material skins associated with solid or hollow stiffeners, also of composite material, and extending transversely, radially and / or or circularly depending on the overall shape of the piece.

Such self-stiffening structures are intended to constitute directly used composite parts or constituting molds / tooling parts, mainly for the aviation industry (monoblock fuselages, reactor mast fairings, wing panels, floors). aircraft industry, etc.), the space industry (reflector antennas), or telecommunications (ground-based transmit / receive antennas), renewable energy (wind turbine blades), rail, automobile or building.

Each skin of the laminated structure consists of fibers impregnated with a thermosetting resin, typically an epoxy resin, forming a binder ensuring the cohesion of the skin and transmitting the forces. The fibers used are generally carbon or glass fibers, or aramid or ceramic fibers depending on the desired characteristics: high mechanical properties (carbon fibers made from acrylic fibers and aramid fibers reinforced by glass-type hybridizations). keviar® or carbon-keviar®), performance / cost ratio (glass fiber) or resistance to high temperatures, for example up to about 2000 ° C (ceramic fibers).

The skin has a composite texture laminated by draping, that is to say by superposition or stack of successive layers, also called folds, resin impregnated fibers. The stacks of plies are uni- or bidirectional, that is to say, in this case, oriented in directions differentiated from one layer to another and recurrent in order to obtain the desired mechanical strength properties (traction, compression , shear, etc.).

Laminated structures intended to undergo twists or flexions are more particularly built on a model of the "sandwich" type. This model consists of two laminated composite skins bonded by bonding to a central core using a compatible resin. The core is a composite material in the form of "honeycomb", corrugations or foam to resist off-plane shear stresses.

There are also multidirectional textures made from voluminal weaves of type 2D to 4D or more, with a corresponding number of directions of fibers or stitching in an additional direction, or according to cylindrical or conical weavings for making parts presenting these forms. Such massive structures are intended more particularly for the aeronautical industry (nozzles, tanks, etc.).

In general, the self-stiffened composite structures are made by draping by pre-impregnation or liquid impregnation of an uncured resin. The skins or skins of the laminated structure are thus formed in a predetermined configuration having, for example, stiffeners, to put the assembly under vacuum and then to polymerize the resin using a crosslinking agent by a heat treatment in an oven , usually an autoclave oven.

This treatment makes it possible to compaction of the stratified textures of the plies with simultaneous hardening of the resin, which guarantees a bonding of the stiffeners and the laminated texture with a low porosity rate and therefore a good material health (c '). that is to say a minimization of defects and shrinkage, a good orientation of the fibers and a resin ratio adapted to the desired mechanical characteristics).

STATE OF THE ART

However, the passage in the autoclave oven is a step that generates a bottleneck in the industrial cycle with a significant downtime, delicate implementation conditions when draping is manual or the impossibility of achieving complex shaped parts that can integrate multiple functions with automatic topping machines, a high labor rate to drape the pre-impregnated sheets or to remedy handling errors that can cause automatic topping, and a duration of limited life of pre-impregnated fabrics that makes inventory management difficult.

To improve these aspects by avoiding the passage in autoclave oven, it is known to use a liquid injection technology vacuum - so-called infusion - which involves draining equipment, strainer type, net , plate or grid, for driving and distributing the resin between and in fiber locks. The crosslinking of the resin can be accelerated by a heat treatment or by subsequent radiation, after shaping of the structure to be produced, in particular by the addition of reinforcing ribs. Such a technology is for example described in US patent document 2011315824, US 2015099834 or US 2015102535.

The principle of the infusion technology is illustrated in Figure 1 by a schematic sectional view of a laminated skin 1 (called "the laminate") of carbon fibers. The laminate 1 resting on a mold support Ml and integrates, on the surface, a draining grid 11 (called "draining"). A bladder 10 hermetically seals the laminate 1 on the support M1 and the vacuum is generated by a pump (not shown) through a conduit 12 in connection with the bladder 10. The thermosetting resin 6 - generally an epoxy resin (alternatively polyester or vinyl ester) is injected onto the laminate 1 via an inlet valve 13, generally from a spiral feed sheath (not shown).

The resin 6 penetrates into the laminate 1 with impregnation edges F1 and F2 in the longitudinal directions D1 and transverse Dt. The impregnation fronts F1 and F2 have different profiles in the draining line 11 and in the laminate 1 : in the drain 11, the impregnation front F1 is constant and moves in the longitudinal direction D1 with a constant and relatively high speed (arrow V1), whereas in the laminate 1 the impregnation front F2 has an inclined slope moving with a significantly lower speed and linearly variable. Indeed, the resin 6 penetrates in the transverse direction Dj of the laminate 1 with a delay which accumulates due to the high density of fibers 7 which induces a low transverse permeability. And the higher the permeability of the drainant 11 is higher the impregnation front F2 is inclined.

Under these conditions, intra-fiber porosities appear in the impregnating start of the laminate 1 close to the drainant 11 because the impregnation speed is then too high and the resin 6 does not have the time necessary for penetration at the heart of the carbon fibers 7 which are, in general, of the multi-filament type (the filaments forming wicks). Conversely, more deeply in the transverse direction Dt of the laminate 1, the low penetration rate induces the formation of inter-fiber porosities in areas which empty with the infiltration of resin 6 in the neighboring locks, the feed then being insufficient. to fill the laminate 1 in depth.

Finally, the impregnation of the resin 6 in the laminate 1 is performed correctly, without generating porosity while promoting a healthy material, only in a thin central portion of the laminate 1. In addition to water retention, these laminates therefore pose material health control problems, which complicates maintenance in the operational phase during the life of the product. Moreover, the draining structures are not very compatible with the integration of stiffening and complex shape functions and do not make it possible to guarantee the geometry of the shapes during the evacuation.

STATEMENT OF THE INVENTION

The invention aims precisely to achieve, in a single operation, a self-stiffening laminated reinforcement structure to form complex configuration parts, large dimensions regardless of the thickness, and can integrate multiple stiffening functions - This eliminates the phases of assembly by riveting-, from a structure substantially devoid of porosity, while producing a very low rate of waste and effluents. To do this, the invention does not use a drainage support but a multiple natural drainage, specific to the draping of the fibers, by cutting into elementary zones of resin infusion according to a mesh of the configuration developed according to a estimation of the permeability of the layers of the laminate. An infusion of the resin is then implemented simultaneously in all the elementary zones of this mesh, which makes it possible to optimize the rate of impregnation of the resin in the reinforcement.

For this purpose, the present invention relates to a method for producing a self-stiffening structure of composite material by a liquid route, comprising a step of forming a determined configuration of a skin associated with stiffeners arranged on the skin, the skin and the stiffeners consisting of a laminate of layers of fibers superimposed according to pre-established directions; a step of estimating the permeabilities of the laminate along three axes in sectors of the laminate of different thicknesses, different orientations of the layers of fibers and limits formed by stiffening interfaces of the different stiffeners; a step of meshing this configuration into cut elementary infusion zones, in proportion to the permeability estimates of the laminate, according to substantially equal element widths in the skin sectors without stiffener and substantially greater widths in the stiffening sectors, according to thicknesses substantially equal to that of the corresponding sector, as well as in lengths and orientations by segmentation adapted to said configuration; a step of positioning resin injection channels in each elementary zone, the channels and the elementary zones being covered in a sealed manner throughout said configuration; a step of pressure conditioning and resin injection in proportion to the dimensions and the permeability of the elementary zones in injection ports in connection with said channels; then, after the impregnation of resin in the fiber sheets, a step of baking the resin followed by a step of removing the channels after atmospheric pressure has been restored.

Under these conditions, for the same duration, the distance traveled by the resin in each channel is on average 100 to 1000 times greater than that traveled by the resin in the laminate. The invention thus makes it possible to impregnate, for the same duration, laminate surfaces of a much larger size than those impregnated with traditional methods. In addition, the lack of draining means and spiral resin feed sheath significantly reduces the waste and the loss of resin in this equipment.

According to preferred embodiments: the steps for estimating the permeabilities and the mesh size of the configuration in elementary zones of infusion are carried out on the basis of measurements of the resin impregnation monitoring in the sectors according to three axes; the steps for estimating the three-axis permeabilities and for meshing the configuration in elementary infusion zones are implemented by modeling the configuration and by simulation, in particular at the input-output boundary conditions, of the resin injections in resin entrances and resin impregnation monitoring; the channel paths are segmented with a balanced distribution of the channels according to main directions of the configuration, a grouping of the resin injection entries according to the quantities of resin to be injected and a limitation of the length of the channel paths; the injection inlets are aligned at one end of primary channels forming a first segment of their path; the channels have a section in increasing evolution from the resin injection inlets, this evolution making it possible to compensate for the resin charge losses in the channels; each sheet of fibers is composed of elementary preforms stamped automatically in press so that the structure exhibits excellent material health despite the absence of compaction during the cooking phase; the stiffeners are previously formed according to a predetermined configuration, in particular by pre-impregnation of resin powder and precooking; the elementary zones form an impregnation network which is repeated sequentially to supply a laminate which has a repetitive conformation; - The pressure setting means are vacuum means or means that exert a pressurization of the configuration, during the step of injecting the resin.

The invention also relates to equipment for implementing the method of producing a self-stiffening structure of composite material from a laminate, as defined above. Such equipment comprises a counter-form in which are cut the resin injection channels in connection with the injection inlets of the resin channels, the counter-form being covered with a pressure-tight sealing envelope and the skin configuration on which the counterform is resting is supported on a mold support.

According to preferred embodiments: the envelope consists of a flexible bladder comprising means for sealing the mold support to achieve a vacuum, the bladder having an output connected to means for putting under empty; the vacuum outlet is located, in the case of a rectangular or multi-rectangular type configuration, opposite the resin supply inlets aligned in a supply duct, and located centrally in the case of a circular configuration; - The envelope consists of a pressure mold in connection with the support mold to exert a determined pressure on the configuration; the channels are connected to an upper face of the counter-form by a connection orifice through which the resin is guided from the injection inlets.

The invention also relates to a one-piece piece formed from a structure made by the method according to the invention with the aid of the equipment defined above. This piece may have, at least partially, a skin surface of variable curvature and is characterized by dimensions of up to a hundred meters with stiffeners separated by a distance adapted to the configuration to be impregnated, in particular between 50 and 500 mm , see more.

PRESENTATION OF FIGURES

Other data, characteristics and advantages of the present invention will appear on reading the following nonlimited description, with reference to the appended figures which represent, respectively: FIG. 1, a schematic sectional view of a stratified skin of carbon fibers during its impregnation with a resin via a draining strainer (already commented); FIGS. 2a and 2b, two upper views of examples of rectangular and circular skin configurations cut into elementary infusion strips in a suitable mesh, with positioning of the channels and resin injection inlets; FIGS. 3a and 3b, upper and lateral views of an elementary zone of infusion of flat surface skin during its impregnation with a resin, highlighting the impregnation fronts from a central channel of resin supply; FIGS. 4a to 4c, cross-sectional views of an elementary infusion zone of "omega" type, "U" type and "solid" type stiffeners resting on a plane surface skin; FIGS. 5a and 5b, sectional views of counter-shaped portions integrating, respectively, a feed channel of an elementary infusion zone of a flat skin, and feed channels of elementary zones of infusion of a "U" stiffener and an "omega" stiffener separated by an elementary flat skin infusion band; FIG. 6, a perspective view of a self-stiffening terrestrial antenna according to the method of the invention, and FIG. 7, a perspective view of a self-stiffened aircraft fuselage panel according to the method. of the invention.

In the figures, identical or similar elements are identified by a same reference sign which refers to (x) passage (s) which describes (s) such an element. The qualifiers "upper" and "lower" refer to the relative position of elements in relation to the basic structure to which these elements relate. The adjectives "longitudinal", "lateral" and "transverse" refer respectively to a principal direction along a principal dimension of an element, to a direction perpendicular to that principal direction in a principal plane of the skin structure, and to a direction perpendicular to this principal direction in a plane perpendicular to the main plane of the skin structure.

DETAILED DESCRIPTION

Referring to the upper view of Figure 2a, a laminated skin configuration 1 'has a planar upper face generally forming a rectangle "R". Such a configuration can be for example applied to aircraft fuselages. The rectangle "R" is here extended, on a C1 side, by a forward A1 contiguous to another A2 extended to fit a particular cut. The skin configuration 1 'is cut into elementary infusion zones, here elementary strips 2 extending from a resin supply sheath 3, via injection channels 4. Advantageously, to carry out an impregnation With nearly simultaneous resin throughout the configuration, the sheath 3 extends linearly and is arranged on a side C2 of the rectangle "R" adjacent to the side C1.

In this simplified example, the configuration T has a substantially constant thickness and fiber sheets uniformly distributed in a fiber density substantially the same throughout the configuration 1 ', the permeability of the laminate is constant in each of the three basic directions (also called "three-axis permeability"), the direction D1 according to the supply sheath 3, the direction D2 perpendicular to this sheath in the plane of the rectangle "R" and according to the constant thickness of the skin 1 (direction Dj in Figure 1), or in the directions Dl, De, Dj (see Figure 3a).

The constancy of the permeabilities can be verified by resin impregnation test measurements in different sectors of the configuration 1 'or by modeling this configuration 1' coupled to a simulation of injection and impregnation of resin in these different sectors of the rectangular part "R" or advances A1 and A2 of this configuration. Such a modeling / simulation method is conducted in a digital unit driven by data processing. This method makes it possible to provide information on the dimensions and distributions of the elementary infusion zones, on the position of the resin injection inlets as well as on the quantities of resin to be provided.

In the example, the uniformity of the layers of fibers, the constancy of the thickness of the skin and the absence of stiffener makes it possible to illustrate the process in a simplified version. More generally, the permeabilities are elaborated according to the three axes in the different sectors, whether by test measurements or by modeling / simulation, from the input data of constitution and orientation of the layers of fibers, the thicknesses of skin, and the geometric and constituent characteristics of the stiffeners, in particular the characteristics of their stiffening interfaces.

Primary elementary strips 21 extend parallel from the resin injection inlets 30 formed in the supply sheath 3. Other secondary elementary bands 22 and tertiary 23 are cut in the advanced Al and A2 as well. only in the rectangle "R", extending perpendicularly to the elementary or primary elementary strips 21 and secondary 22. All the elementary strips 2 have, in this example, widths 2i substantially identical.

Primary injection channels 41 are positioned on the central lines 51 primary elementary infusion strips 21, the channels 41 extending, if necessary, by connection to the secondary channels 42 and tertiary 43 positioned respectively along the secondary median lines 52 and tertiary 53 of secondary elementary bands 22 and tertiary 23 (the median lines 51 to 53 appearing in dashed arrowed lines). More particularly, the primary channel 41a of the primary elementary band 21a, adjacent the secondary bands 22, is extended by the secondary channels 42 of the Al and A2 advances, one of these secondary channels 42a extending along the tertiary midlines 53 by tertiary channels 43. In addition, another primary channel 41b of the primary elementary band 21b is extended by connection to the secondary channels 42b of other secondary elementary bands 22 opening on the side C3 opposite the C1 side of the rectangle "R".

The successive extensions 42a and 43 and 42b of the primary channels 41a and 41b form, along the corresponding medians 51 to 53, paths having linear segments successively perpendicular. This results from the pluri-rectangular shape of the skin configuration 1. For other, more complex skin configurations, the segments may form injection channel paths that articulate at non-right angles.

In order to inject the resin into the secondary elementary bands 22 and tertiary 23, a single primary channel 41a or 41b is used to connect to the secondary channels 42, then a single secondary channel 42a is used to connect to the tertiary channels 43. This distribution from the same channel favors a balanced distribution of the channels according to the directions of permeability DI and D2 which are the basic directions of this configuration.

In the case where several directions are identified for a given skin configuration, this connection option on several channels from the same channel is preferred to balance the distribution of the channels in different directions. In addition, a grouping option is advantageously applied: the longest primary channels or having the longest path extensions, here the channels 41a to 41c, and therefore intended to carry larger quantities of resin than the others are preferably grouped in order to optimize the distribution of the resin.

Moreover, the choice between the primary channels 41b and 41c to connect to the secondary channels 42b is advantageously guided by the total length of the channels thus extended: in order not to form too long channels, beyond a Ceiling value Lm determined according to the surface of the configuration 1 ', it is advantageous to select the channel - here the channel 41b - which, after multiple connection with the secondary channels 42b, provides channel lengths below the ceiling value Lm. More generally, this option for limiting the length of channels intervenes for the choice of the connection of a channel to one of the secondary order channels with respect to this channel.

In general, when the thickness of the configuration is not constant or has curved parts, the determination of the mesh of the elementary zones of infusion, and the positioning of the resin injection channels by the choice connections between these channels first take into account the permeability estimates before applying the advantageous options mentioned above. Such options - multiple connections for a balanced distribution of the channels according to the main directions of the configuration, grouping by importance of the quantities of resin and limitation of the lengths of the channels - can be advantageously integrated with the boundary conditions in the processing of the data of the unit digital.

The upper view of FIG. 2b illustrates another example of a laminated skin configuration 1 ", here of a generally circular and non-planar shape, of the" spherical cap "type, having a central orifice 101 in connection with a delivery conduit. under vacuum. The mesh in elementary infusion zones is here in the form of concentric elementary rings 102. The laminate of the configuration 1 "consists of sheets of fibers uniformly distributed at a substantially identical density, as in the case of the multiple configuration. Rectangular plane illustrated in Figure 2a.

The permeability of the laminate is then substantially constant in the three basic directions described above. The resin injection inlets 103 are then distributed on each circular channel 104 axially symmetric about the axis Z'Z of the part to homogenize the impregnation of the resin in each elementary ring 102. The number of Injection entries per channel is a function of the permeability of the tissues to be impregnated.

When the surface is not of constant curvature but has local curvatures adapted to the functions of the configuration, and / or when the thickness of the configuration is not constant, the elementary infusion rings may have Variable widths based on permeability estimates in the three basic directions.

In the illustrated example, once the resin is injected into the injection inlets 103, it impregnates the laminate radially from the outside towards the inside (arrows Fr) from the channels 104. The radial orientation results the central position of the vacuum draw in connection with the central orifice 101, the depression controlling the impregnation of the resin being made from this orifice 101 forming the vent point.

Only the crown farthest from the orifice 101 has a portion 102e outwardly of its feed channel 104 due to the time of vacuuming and installation of the vacuum. The radial impregnation of the resin then takes place in the portion 102e centripetally (arrows Fc), from the inside to the outside, from the channels 104.

In order to illustrate the impregnation of resin, the (partial) top and side views of FIGS. 3a and 3b show an infusion channel 4 during the impregnation of resin 6 in an elementary infusion band 2 of the Figure 2a. It appears that during the advance (arrow V2) of the resin 6 in the channel 4, its partial impregnation in each elementary infusion band 2 defines, in top view (FIG. 3a), two impregnation fronts F3 and F4. progressing symmetrically inclined (arrows V3 and V4) with respect to the longitudinal direction D1 defined by the channel 4. The resin 6 is inserted between and in the fibers 7 formed of wicks. The longitudinal front impregnation advance Fl and the lateral edges VI in the longitudinal directions Dl and lateral De, appear in Figure 3b. In particular, the lateral edges F 1 come to align with the longitudinal boundaries 2f of the elementary infusion band 2 because of the progressive impregnation fronts Fa (shown in dashed lines) formed in the elementary strips adjacent to the band 2.

When the skin configuration includes stiffeners, the mesh of the elementary injection zones is cut taking into account the reinforcement interfaces formed by these stiffeners. The sectional views of FIGS. 4a to 4c illustrate the positioning of injection channels, respectively 4a to 4c, in elementary infusion zones 20a to 20c incorporating stiffeners, respectively Ra to Rc. The mesh of the skin configuration to be impregnated integrates the reinforcement interfaces, respectively 8a to 8c, induced by the presence of the stiffeners Ra to Rc, as boundaries between the elementary zones defined by this mesh (see also FIG. 5b).

In Figure 4a, the stiffener Ra is hollow and has in section a so-called "omega" rib shape, with a flat upper wall R10 surrounding two walls R11 and R12 symmetrically inclined relative to a plane of symmetry P1. The inclined walls R11, R12 are extended on the skin 1 by two soles, respectively R13 and R14. The injection channel 4a is positioned on the median line 5a of the upper wall R10.

In Figure 4b, the stiffener Rb is also hollow with, in section, a so-called "U-shaped" rib formed of a flat top wall R20 mounted, during a stamping in advance press, on two walls R21 and R22 perpendicular to the R20 advance. The injection channel 4b is positioned on the center line 5b of the upper face S20 of the upper wall R20 in the plane of symmetry P2 of the stiffener Rb.

Referring to Figure 4c, the stiffener Rc is full and formed by two walls in "L" R 31 and R 32 arranged on the skin 1 and contiguous back to back during a resin pre-impregnation followed by pre-cooking. The injection channel 4c is disposed on the center line 5c partially overlapping the upper edges S30 of the walls R31 and R32.

The resin injection channels 4a to 4c, 41a to 41c, more generally referenced 4 (see FIGS. 2a, 3a, 3b, 4a, 4b), are cut in a counterform 9 which bears on the skin configuration 1, as illustrated by the sectional views of the elementary infusion zones of FIGS. 5a and 5b.

In Figure 5a, the elementary infusion zone is a band 2 already shown in Figures 2, 3a or 3b. The skin 1 has a planar upper face 1s devoid of stiffener and a thickness "E" constant.

The channel 4 which is positioned on the center line 5 of the elementary strip 2 has an isosceles triangular section 4T with a base opening 4V resting on the face 1s. The triangular shape is preferred because it allows a regular and gradual infusion of the resin 6 into the skin 1 (see Figure 3a). Other shapes are possible: rectangular, semi-circular, semi-polygonal, semi-oblong, etc. Advantageously, the section 4T increases from the resin injection inlets 30 (see FIG. 2) in order to compensate the resin charge losses in each channel 4.

The top 4s of the channel 4 is connected to the upper face 9s of the counter-form 9 by a resin injection slot 4f, serving as a connecting orifice. Counter-form 9 rests on the flat face of skin 1s and has a substantially constant thickness 9e in the elementary infusion zone 2. This counterform 9 extends over the entire skin configuration 1.

Thus, in the presence of stiffeners, such as the stiffeners Ra and Rb of Figures 4a and 4b, the counter-form 9 fits the faces of the walls of these stiffeners. The sectional view of FIG. 5b illustrates such a counterform 9 resting on the elementary infusion zones 20a and 20b which integrate the stiffeners Ra and Rb (see FIGS. 4a and 4b) associated with the skin 1, the elementary zones. 20a and 20b being separated by the elementary infusion band 2 without a stiffener (as shown in FIG. 5a).

The injection channels 4 and the corresponding slots 4f are cut in the counter-form 9 to the right of the median lines 5a and 5b of the upper walls RIO and R20 of the stiffeners Ra and Rb (see also Figures 4a and 4b). ) and the right of the center line 5 of the elementary infusion band 2. The reinforcement interfaces 8a and 8b due to the stiffeners Ra and Rb define the boundaries of the elementary zones 20a, 20b, centered on the stiffeners Ra and Rb and integrated into the mesh (see also Figures 4a and 4b).

The againstform 9 is covered in a sealed manner over the entire extent of the skin configuration 1 by a flexible bladder 10 which allows a vacuum under an outlet located opposite the supply sheath 3 resin (see Figure 2a) and connected to vacuum means (see also Figure 1). The resin 6 (see FIGS. 3a and 3b) is then injected in proportion to the dimensions and the permeability of the elementary zones, referenced 2, 20a and 20b in FIG. 5b.

After the impregnation of the resin in the fiber webs of the skin 1, the atmospheric pressure is restored, then the bladder 10 and against the form 9 are removed with the channels 4. A final step of cooking the resin 6 (see FIGS. 3a and 3b) is operated, for example by steaming or under pressure.

Self-stiffened monoblock pieces can then be formed from a skin configuration obtained by the preceding steps with, beforehand for the stiffeners, a resin impregnation step and a pressure stamping. For example, Figure 6 shows a perspective view of a self-stiffening terrestrial antenna 100 formed of a skin having a substantially spherical curvature IA and provided with circular stiffeners Rs and radial Rd which intersect by bridging. FIG. 7 illustrates the perspective view of a self-stiffened aircraft fuselage panel 200 formed of a skin IB with a cylindrical curvature and equipped with longitudinal cross-braced cross-brace R1 and cross-braced stiffeners.

These parts have, at least partially, a stratified skin of variable curvature and can reach a few tens of meters in diameter or length, or even a hundred meters, and stiffeners such as Rs, Rd or Rt, Rl separated from each other. a dozen to a few tens of centimeters, for example up to 50 centimeters or more.

The invention is not limited to the embodiments described and shown. Thus, the method according to the invention can be totally or partially automated. Moreover, the laminated skin may have locally variable or left curvatures and the stiffeners may be of varied geometric section: semicircular, triangular, semi-polygonal, oblong, etc.

Claims (18)

1. A method for producing a self-stiffening structure of liquid composite material, comprising a step of forming a determined configuration (1 ', 1 ") of a skin (1; 1A; 1B) associated with stiffeners (Ra to Rc; Rs, Rd; Rl, Rt) disposed on skin, skin and stiffeners consisting of a laminate of fiber plies (7) superimposed in predetermined directions (D1, D2; D1), characterized in that it also comprises a step of estimating the permeabilities of the laminate (1) along three axes (D1, D2, D1, D1, De, Dj) in sectors of the laminate of different thicknesses (E), different orientations fiber webs (7) and boundaries formed by stiffening interfaces (8a; 8b) of the different stiffeners (Ra to Rc; Rs, Rd; Rl, Rt); a step of meshing this configuration (1 ', 1 ") into cut elementary zones (2; 21,22,23; 20a; 20b; 102), in proportion to the permeability estimates of the laminate, in elementary widths substantially equal {2ή in the sectors of skin (1) without stiffener and substantially greater widths in the stiffening sectors, in thicknesses (E) substantially equal to that of the corresponding sector, and in lengths and orientations by adapted segmentation said configuration (T, 1 "); a step of positioning resin injection channels (4; 41, 41a, 41b; 42, 42a, 42b; 43; 4a, 4b, 4c; 104) in each elementary zone (2; 21, 21a, 21b; , 23, 20a, 20b, 102), the channels (4; 41, 41a, 41b; 42, 42a, 42b; 43; 4a, 4b, 4c; 104) and the elementary areas (2; 21, 21a, 21b; 22, 23, 20a, 20b, 102) being sealed to the full extent of said configuration (R, Al, A2; 1 "); a step of pressure conditioning and resin injection (6) in proportion to the dimensions and permeability of the elementary zones (2; 21, 21a, 21b; 22, 23; 20a; 20b; injection (30; 130) in connection with said channels (4; 104); then, after the impregnation of resin (6) in the fiber sheets (7), a step of baking the resin (6) followed by a step of removing the channels (4; 104) after re-establishing the atmospheric pressure . 2. A method of producing a self-stiffened structure according to claim 1, wherein the step of estimating the permeabilities is conducted from measurements of the resin impregnation monitoring (6) in the sectors along three axes ( D 1, D 2, Dt, D 1, D 1, D 1). 3. A method of producing a self-stiffening structure according to claim 1, wherein the steps of estimating three-axis permeabilities (D1, D2, Dt: D1, D1, Dt) and mesh configuration (1). ', 1 ") in elementary infusion zones (2; 21, 22, 23; 20a; 20b; 102) are implemented by modeling the configuration and by simulation, in particular at the input-output boundary conditions, resin injections (6) into the resin inlets (30; 130) and resin impregnation monitoring. 4. A method of producing a self-stiffening structure according to any one of claims 1 to 3, wherein, in the case of a rectangular or multi-rectangular type configuration (1 '), the channel paths ( 4) are segmented with a balanced distribution of the channels (41; 42; 43;) according to principal directions (D1, D2) of the configuration (1 '), a grouping of the resin injection inlets (30) according to the quantities of resin to be injected and a limitation of the paths of the channels (4) in length. 5. A method of producing a self-stiffening structure according to the preceding claim, wherein the injection inlets (30) are aligned at one end of primary channels (41) forming a first segment of their path. 6. A method of producing a self-stiffening structure according to the preceding claim, wherein the channels have a section (4T) in increasing evolution from the resin injection inlets (30). 7. A method of producing a self-stiffened structure according to any one of the preceding claims, wherein each fiber web (7) is composed of elementary preforms stamped automatically in press. 8. A method of producing a self-stiffened structure according to any preceding claim, wherein the stiffeners (Ra, Rb, Rc, Rs, Rd, R1, Rt) are previously impregnated with resin (6) and embossed in press. 9. A method of producing a self-stiffening structure according to any one of the preceding claims, wherein the elementary zones (2; 21, 22, 23; 20a; 20b) form an impregnation network which is repeated sequentially for feeding a laminate that has a repetitive conformation. 10. A method of producing a self-stiffening structure according to any one of the preceding claims, wherein the means for setting pressure condition are vacuum means during the resin injection step ( 6). 11. A method of producing a self-stiffening structure according to any one of claims 1 to 9, wherein the pressure conditioning means exert a pressure of the configuration (1 ', 1 ") during the injection step of the resin (6). 12. A method of producing a self-stiffening structure according to any one of the preceding claims, wherein the final firing step is selected between molding or baking. 13. Equipment for implementing the method for producing a self-stiffening structure according to any one of the preceding claims, characterized in that it comprises a counter-form (9) in which the injection channels are cut out. of resin (4, 4a, 4b, 4c) in connection with injection inlets (3; 103) of the resin channels, the counter-form (9) being covered with a pressure-tight sealing envelope and the skin configuration (1 ') on which the counter-form (9) rests is supported on a mold support (Ml). 14. Equipment according to the preceding claim, wherein the casing consists of a flexible bladder (10) comprising sealing means to the mold support (Ml) to perform a vacuum, the bladder (10) having a output connected to vacuum means. 15. Equipment according to the preceding claim, wherein the vacuum outlet is located, in the case of a rectangular or multi-rectangular type configuration (1 '), opposite the resin supply inlets ( 3) aligned in a supply duct (3), and located centrally (101) in the case of a configuration of circular type (1 "). 16. Equipment according to claim 14, wherein the envelope consists of a pressure mold in connection with the support mold (Ml) to exert a determined pressure on the configuration (1 '). 17. Equipment according to any one of claims 14 to 16, wherein the channels (4, 4a, 4b, 4c) are connected to an upper face (9s) of the counter-form (9) by a connecting orifice ( 9f) by which the resin (6) is guided from the injection inlets (30; 130). 18. Monobloc piece formed from a structure made by the method according to any one of claims 1 to 12 with the aid of the equipment according to any one of claims 13 to 17, characterized in that it at least partially presents a skin surface (IA; IB) of variable curvature and dimensions of up to one hundred meters with stiffeners (Rc, Rd, Rt, Rl) separated by a distance adapted to the configuration to be impregnated , in particular between 50 and 500 mm.