WO2010089464A1 - Core for producing a stiffener in a composite panel - Google Patents

Core for producing a stiffener in a composite panel Download PDF

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Publication number
WO2010089464A1
WO2010089464A1 PCT/FR2009/000134 FR2009000134W WO2010089464A1 WO 2010089464 A1 WO2010089464 A1 WO 2010089464A1 FR 2009000134 W FR2009000134 W FR 2009000134W WO 2010089464 A1 WO2010089464 A1 WO 2010089464A1
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WO
WIPO (PCT)
Prior art keywords
core
core according
film
vacuum
heat
Prior art date
Application number
PCT/FR2009/000134
Other languages
French (fr)
Inventor
Fabrice Cot
Original Assignee
Aerovac Systemes France
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Aerovac Systemes France filed Critical Aerovac Systemes France
Priority to PCT/FR2009/000134 priority Critical patent/WO2010089464A1/en
Publication of WO2010089464A1 publication Critical patent/WO2010089464A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/44—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
    • B29C33/40—Plastics, e.g. foam or rubber
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28—Shaping operations therefor
    • B29C70/40—Shaping or impregnating by compression not applied
    • B29C70/42—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
    • B29C70/44—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using isostatic pressure, e.g. pressure difference-moulding, vacuum bag-moulding, autoclave-moulding or expanding rubber-moulding

Definitions

  • the present invention relates to a core for producing a cavity in a composite part obtained by vacuum molding.
  • composite parts are used in many areas and, given their mechanical properties, can replace metal parts.
  • composite material means any material comprising reinforcements impregnated with resin. Reinforcements may take the form of woven web, nonwoven, unidirectional son eg glass, carbon, aramid etc. impregnated with a thermosetting resin.
  • a known method for producing parts made of composite material is vacuum molding.
  • this process consists of depositing on a molding tool one or more pre-impregnated plies (fabric, mat, unidirectional layer).
  • a waterproof film is deposited on the textile projecting at the periphery; a sealing bead is disposed between the film and the molding tool.
  • a vacuum is then applied between the film and the molding tool. This creates a drainage of all the gas trapped in the superposed layers and in the resin matrix.
  • the parts thus obtained are devoid of gaseous inclusions and are therefore of excellent quality; this allows them in particular to be used in the aeronautical field.
  • stiffeners In this field, there is a need for large composite parts. It is necessary to stiffen these parts by stiffeners. These stiffeners according to the current state of the art can be reported by riveting or gluing.
  • one or more cores can be interposed between the reinforcing plies.
  • one or more elongated cores one or more elongate cavities of cross section in the form of P1 or ⁇ are thus created; these elongated cavities act as beams in the composite parts and increase their inertia.
  • the core must be accurately positioned on the tooling and must maintain its positioning during the draping operation. This operation can also be performed by robots that act quickly and can change the correct positioning of the core.
  • the core can be extracted from the finished part.
  • the section of the rib must remain constant. In other words, it is not conceivable to provide a kernel that would have a body in its longitudinal direction.
  • the core does not react with one of the constituents of the part and that it retains its geometry during pressurizing operations.
  • the present invention aims to overcome these disadvantages.
  • An object of the invention is to provide a core for producing a cavity, such as for example a stiffener, in a composite part obtained by vacuum molding which guarantees a precise geometry of the cavity, which is easily extractable and which is a low cost.
  • the present invention relates to a core intended to form a cavity in a piece of laminated composite material obtained by a vacuum molding process including in particular a vacuum phase and a temperature increase phase and pressurization under autoclave; in addition, the core has a core defining the geometry of the cavity formed of the part, said core being made of a material having a mechanical strength ensuring the geometry of the core during the vacuum phase of the workpiece and allowing the contraction of the core when raising the temperature of the room.
  • the invention provides a core which has a mechanical strength which allows it to maintain its geometry during draping and vacuuming phases and which contracts during the climb in temperature that occurs to ensure the polymerization of the composite part.
  • the core is made of a closed cell phenolic foam.
  • the closed cell phenolic foam has indeed a high mechanical strength at room temperature which allows the core to withstand draping and vacuuming operations. This is essential for the accuracy of the geometry of the cavity that is formed in the room.
  • the phenolic foam shrinks without melting during the temperature rise required for the polymerization of the room. The contraction of the core thus makes it possible to remove it at the end of the polymerization.
  • the core has an outer sheath made of a tight material with a low coefficient of friction so as to ensure good pressure transmission, especially during the autoclaving phase, and to facilitate extraction of the core at the end of the polymerization.
  • the outer sheath also serves to form a barrier between the core and the composite part to maintain the chemical integrity thereof.
  • the outer sheath may for example be a film of FEP.
  • the core is surrounded by a heat-shrinkable film which allows to accentuate the contraction of the core during the rise in temperature of the room.
  • the heat-shrinkable film may consist of a helical winding of a strip of prestressed polyester film.
  • a porous fabric sheath is superimposed on the heat-shrinkable film.
  • This porous fabric sheath has the main function of ensuring a good distribution and a good flow of pressure in the autoclave.
  • the porous fabric sheath may for example consist of a woven tube made of polyester yarns.
  • the core may have a density of between 40 and 100 kg / m 3 so as to have a mechanical strength that allows it to withstand draping and vacuuming operations.
  • the soul has at least one channel.
  • the core has an elongate shape of trapezoidal cross-section.
  • FIG. 1 shows schematically in cross section a core according to the invention
  • Figure 2 and Figure 3 show two vacuum molding variants incorporating the core according to the invention.
  • FIG. 2 we can see a molding tool 2 in which is formed a groove 3 which, in the example shown, has a trapezoidal section.
  • one or more resin prepreg plies 4 are optionally arranged with different orientations in the groove 3,
  • one or more resin prepreg plies form the composite part itself
  • a vacuum film 7 is then placed on the workpiece with a seal 8 at the periphery.
  • the plies 4 and 5 can be raw or cooked and that drainage felts can be interposed between the evacuation film and the workpiece.
  • a drainage device (not shown in the figures) allows, by depression, to extract the gases present between the molding tool and the sealed film, that is to say the gases and other air bubbles which are included in the room.
  • the drainage device can engage one or more vacuum taps 10 made in the vacuum film 7.
  • Figure 2 shows the problem of making a cavity in a composite part which is obtained by vacuum molding. It is, indeed, the core 1 which conditions the good dimensioning of the stiffener.
  • the core has an original structure as shown in FIG.
  • the core 1 comprises a core 12 of phenolic resin in the closed-cell foam state.
  • the density of the phenolic resin is of the order of 40 to 100 kg / m 3 .
  • a heat-shrinkable film 13 is wound helically over the core 12 of phenolic foam.
  • a draining porous fabric sheath such as a woven polyester tube surrounds the core 12 and the heat-shrinkable film 13 over the entire length of the core.
  • outer sheath 15 of impermeable material with a low coefficient of friction forms the skin of the core.
  • the outer sheath 15 may be, for example, made of FEP.
  • the core 1 provides a counter-support which makes it possible to form a stiffener. It is important that the core does not crush when the tablecloths are removed by an automatic draping machine or under the effect of the depression.
  • This mechanical strength is mainly due to the core 12 of phenolic resin whose density can counteract the vacuum required for drainage. It is also the core core 12 which essentially contributes to the dimensional accuracy and reproducibility of the stiffener, which is formed in the composite part.
  • the function of the porous fabric sheath is to distribute the pressure of the autoclave uniformly.
  • the outer sheath 15 ensures that the core does not react with the workpiece and therefore does not pollute the workpiece.
  • the vacuum phase is followed by a temperature rise phase under autoclave which ensures the polymerization of the resin.
  • a temperature rise phase which occurs at a temperature of the order of 80 0 C to 200 0 C the phenolic foam which constitutes the core 12 collapses on itself but does not melt.
  • the sagging of the core 12 is favored by the winding of heat-shrinkable film 13.
  • the core 1 thus has a cross section substantially smaller than that of the stiffener and can be extracted by pulling on it.
  • the extraction of the core 1 is, moreover, facilitated by the outer sheath 15 which is made of a material with a low coefficient of friction, for example FEP and by the sheath 14 of polyester fabric on which it is possible to exert traction .
  • the core is then processed for possible recycling.
  • Figure 3 shows an alternative embodiment of a stiffener obtained by vacuum molding in which the core is on the face of the part opposite to that which is in contact with the molding tool.
  • the core 1 according to the invention behaves and has the same advantages as when it is implemented as illustrated in FIG. 2.
  • the kernel can present an evolutionary section. It is, moreover, envisaged to make the core on the molding site from sections of phenolic foam which are placed end to end and sheathed by the heat-shrinkable film.

Abstract

The invention relates to a core (1) for making a recess in a part made of a laminated composite material obtained by a vacuum-moulding method that particularly includes an evacuation phase and then a temperature-raising and pressurising phase in an autoclave, wherein said core has a web (12) defining the shape of the recess formed in the part, said web (12) being made of a material ensuring the shape of the core (1) during the evacuation phase for the part and enabling the contraction of the core (1) upon raising the temperature of the part.

Description

NOYAU POUR REALISER UN RAIDISSEUR DANS UN PANNEAU COMPOSITE CORE FOR REALIZING A STIFFENER IN A COMPOSITE PANEL
La présente invention concerne un noyau pour réaliser une cavité dans une pièce composite obtenue par moulage sous vide.The present invention relates to a core for producing a cavity in a composite part obtained by vacuum molding.
Les pièces en matière composite sont utilisées dans de nombreux domaines et, compte tenu de leurs propriétés mécaniques, peuvent se substituer à des pièces métalliques. Au sens du présent document, on entend par matériau composite tout matériau comprenant des renforts imprégnés de résine. Les renforts peuvent prendre la forme de nappe tissée, non tissée, de fils unidirectionnels par exemple de verre, de carbone, d'aramide etc. imprégnés d'une résine thermodurcissable.Composite parts are used in many areas and, given their mechanical properties, can replace metal parts. As used herein, the term "composite material" means any material comprising reinforcements impregnated with resin. Reinforcements may take the form of woven web, nonwoven, unidirectional son eg glass, carbon, aramid etc. impregnated with a thermosetting resin.
Un procédé connu pour la réalisation de pièces en matériau composite est le moulage sous vide.A known method for producing parts made of composite material is vacuum molding.
Schématiquement ce procédé consiste à déposer sur un outillage de moulage une ou plusieurs nappes (tissu, mat, nappe unidirectionnelle) pré imprégnées. Un film étanche est déposé sur le textile en débordant en périphérie ; un cordon d'étanchéité est disposé entre le film et l'outillage de moulage. Une dépression est ensuite appliquée entre le film et l'outillage de moulage. Ceci crée un drainage de tout le gaz emprisonné dans les nappes superposées et dans la matrice de résine. Les pièces ainsi obtenues sont dépourvues d'inclusions gazeuses et sont donc d'excellente qualité ; ceci leur permet notamment d'être utilisées dans le domaine aéronautique.Schematically this process consists of depositing on a molding tool one or more pre-impregnated plies (fabric, mat, unidirectional layer). A waterproof film is deposited on the textile projecting at the periphery; a sealing bead is disposed between the film and the molding tool. A vacuum is then applied between the film and the molding tool. This creates a drainage of all the gas trapped in the superposed layers and in the resin matrix. The parts thus obtained are devoid of gaseous inclusions and are therefore of excellent quality; this allows them in particular to be used in the aeronautical field.
Dans ce domaine, il existe un besoin de pièces en matériau composite de grandes dimensions. Il s'avère nécessaire de raidir ces pièces par des raidisseurs. Ces raidisseurs selon l'état actuel de la technique peuvent être rapportés par rivetage ou collage.In this field, there is a need for large composite parts. It is necessary to stiffen these parts by stiffeners. These stiffeners according to the current state of the art can be reported by riveting or gluing.
On peut également réaliser des pièces composites de grande dimension intégrant un ou plusieurs raidisseurs. Pour cela, un ou plusieurs noyaux peuvent être interposés entre les nappes de renfort. Avec un ou plusieurs noyaux de forme allongée, il est ainsi crée une ou plusieurs cavités allongées de section transversale en forme Pl ou de Ω ; ces cavités allongées agissent comme des poutres dans les pièces composites et en augmentent l'inertie.It is also possible to produce large composite parts incorporating one or more stiffeners. For this, one or more cores can be interposed between the reinforcing plies. With one or more elongated cores, one or more elongate cavities of cross section in the form of P1 or Ω are thus created; these elongated cavities act as beams in the composite parts and increase their inertia.
Cependant la présence de ce ou ces noyaux présente certaines difficultés. Le noyau doit être positionné avec précision sur l'outillage et doit conserver son positionnement durant l'opération de drapage des nappes. Cette opération peut d'ailleurs être réalisée par des robots qui agissent de manière rapide et peuvent modifier le positionnement correct du noyau.However the presence of this or these nuclei presents some difficulties. The core must be accurately positioned on the tooling and must maintain its positioning during the draping operation. This operation can also be performed by robots that act quickly and can change the correct positioning of the core.
Il convient de plus que le noyau puisse être extrait de la pièce finie. A ce sujet, la section de la nervure doit restée constante. En d'autres termes, il n'est pas concevable de prévoir un noyau qui présenterait une dépouille dans sa direction longitudinale.It is also necessary that the core can be extracted from the finished part. In this regard, the section of the rib must remain constant. In other words, it is not conceivable to provide a kernel that would have a body in its longitudinal direction.
Il importe enfin que le noyau ne réagisse pas avec l'un des constituants de la pièce et qu'il conserve sa géométrie durant les opérations de mise sous pression.Finally, it is important that the core does not react with one of the constituents of the part and that it retains its geometry during pressurizing operations.
Il est connu d'utiliser une vessie gonflable en sîlicone pour réaliser le noyau. Ces vessies ont cependant de nombreux inconvénients. Elles sont d'un coût élevé. Elles sont certes réutilisables mais il est difficile de vérifier leur étanchéité. Or, au cours de l'extraction de la vessie, il se produit d'importants frottements dont la répétition finit par endommager la vessie. En outre, le stockage de ces vessies pose de nombreux problèmes de logistique.It is known to use an inflatable bladder in silicone to make the core. These bladders, however, have many disadvantages. They are expensive. They are certainly reusable but it is difficult to check their tightness. However, during the extraction of the bladder, there is significant friction which repetition eventually damage the bladder. In addition, the storage of these bladders poses many logistical problems.
La présente invention a pour objet de remédier à ces inconvénients.The present invention aims to overcome these disadvantages.
Un but de l'invention est de proposer un noyau pour réaliser une cavité, tel que par exemple un raidisseur, dans une pièce en matière composite obtenue par moulage sous vide qui garantisse une géométrie précise de la cavité, qui soit aisément extractible et qui soit d'un faible coût.An object of the invention is to provide a core for producing a cavity, such as for example a stiffener, in a composite part obtained by vacuum molding which guarantees a precise geometry of the cavity, which is easily extractable and which is a low cost.
La présente invention concerne un noyau destiné à former une cavité dans une pièce en matériau composite stratifié obtenue par un procédé de moulage sous vide comprenant notamment une phase de mise sous vide puis une phase d'élévation de température et de mise sous pression sous autoclave ; de plus, le noyau présente une âme définissant la géométrie de la cavité formée de la pièce, ladite âme étant réalisée dans un matériau ayant une tenue mécanique garantissant la géométrie du noyau lors de la phase de mise sous vide de la pièce et permettant la contraction du noyau lors de l'élévation de température de la pièce.The present invention relates to a core intended to form a cavity in a piece of laminated composite material obtained by a vacuum molding process including in particular a vacuum phase and a temperature increase phase and pressurization under autoclave; in addition, the core has a core defining the geometry of the cavity formed of the part, said core being made of a material having a mechanical strength ensuring the geometry of the core during the vacuum phase of the workpiece and allowing the contraction of the core when raising the temperature of the room.
Ainsi, l'invention fournit un noyau qui possède une tenue mécanique qui lui permet de maintenir sa géométrie lors des phases de drapage et de mise sous vide et qui se contracte lors de la montée en température qui se produit pour assurer la polymérisation de la pièce composite.Thus, the invention provides a core which has a mechanical strength which allows it to maintain its geometry during draping and vacuuming phases and which contracts during the climb in temperature that occurs to ensure the polymerization of the composite part.
De préférence, l'âme est constituée d'une mousse phénolique à cellule fermée. La mousse phénolique à cellule fermée possède en effet une tenue mécanique importante à température ambiante qui permet au noyau de résister aux opérations de drapage et de mise sous vide. Cela est essentiel pour la précision de la géométrie de la cavité qui est formée dans la pièce. De plus la mousse phénolique se contracte sans pour autant fondre au cours de l'élévation de température nécessaire à la polymérisation de la pièce. La contraction du noyau permet ainsi de le retirer en fin de polymérisation.Preferably, the core is made of a closed cell phenolic foam. The closed cell phenolic foam has indeed a high mechanical strength at room temperature which allows the core to withstand draping and vacuuming operations. This is essential for the accuracy of the geometry of the cavity that is formed in the room. In addition the phenolic foam shrinks without melting during the temperature rise required for the polymerization of the room. The contraction of the core thus makes it possible to remove it at the end of the polymerization.
Selon une disposition avantageuse le noyau présente une gaine extérieure réalisée dans un matériau étanche et à faible coefficient de frottement de façon à assurer une bonne transmission de la pression notamment durant la phase d'autoclavage et à faciliter l'extraction du noyau en fin de polymérisation. La gaine extérieure a également pour fonction de former une barrière entre le noyau et la pièce composite pour conserver l'intégrité chimique de celle-ci.According to an advantageous arrangement, the core has an outer sheath made of a tight material with a low coefficient of friction so as to ensure good pressure transmission, especially during the autoclaving phase, and to facilitate extraction of the core at the end of the polymerization. . The outer sheath also serves to form a barrier between the core and the composite part to maintain the chemical integrity thereof.
La gaine extérieure peut par exemple être un film de FEP.The outer sheath may for example be a film of FEP.
Il peut être, par ailleurs, prévu que l'âme soit entourée d'un film thermorétractable ce qui permet d'accentuer la contraction du noyau lors de l'élévation de température de la pièce.It may be, moreover, provided that the core is surrounded by a heat-shrinkable film which allows to accentuate the contraction of the core during the rise in temperature of the room.
Le film thermorétractable peut être constitué d'un enroulement hélicoïdal d'une bande d'un film polyester précontraint.The heat-shrinkable film may consist of a helical winding of a strip of prestressed polyester film.
Selon une autre disposition avantageuse, une gaine de tissu poreux est superposée sur le film thermorétractable. Cette gaine de tissu poreux a pour fonction principale d'assurer une bonne répartition et un bon cheminement de la pression dans l'autoclave.According to another advantageous arrangement, a porous fabric sheath is superimposed on the heat-shrinkable film. This porous fabric sheath has the main function of ensuring a good distribution and a good flow of pressure in the autoclave.
La gaine de tissu poreux peut être par exemple constituée par un tube tissé en fils_de polyester.The porous fabric sheath may for example consist of a woven tube made of polyester yarns.
En pratique, l'âme peut présenter une densité comprise entre 40 et 100 kg/m3 de façon à présenter une tenue mécanique qui lui permet de résister aux opérations de drapage et de mise sous vide.In practice, the core may have a density of between 40 and 100 kg / m 3 so as to have a mechanical strength that allows it to withstand draping and vacuuming operations.
Il peut être envisagé que l'âme présente au moins un canal.It can be envisaged that the soul has at least one channel.
De une forme de réalisation, le noyau présente une forme allongée de section transversale en trapèze. Pour sa bonne compréhension, l'invention sera décrite en référence au dessin schématique annexé représentant le noyau selon l'invention.In one embodiment, the core has an elongate shape of trapezoidal cross-section. For a good understanding, the invention will be described with reference to the attached schematic drawing showing the core according to the invention.
Figure 1 montre schématiquement en coupe transversale un noyau selon l'invention,FIG. 1 shows schematically in cross section a core according to the invention,
Figure 2 et Figure 3 montrent deux variantes de moulage sous vide intégrant le noyau selon l'invention.Figure 2 and Figure 3 show two vacuum molding variants incorporating the core according to the invention.
En se reportant tout d'abord à la figure 2, on peut voir un outillage de moulage 2 dans lequel est ménagée une rainure 3 qui, dans l'exemple illustré, présente une section en trapèze.Referring firstly to Figure 2, we can see a molding tool 2 in which is formed a groove 3 which, in the example shown, has a trapezoidal section.
Le principe de fabrication d'une pièce en matériau composite intégrant un raidisseur est le suivant :The principle of manufacturing a composite material part incorporating a stiffener is as follows:
- une ou plusieurs nappes 4 préimprégnées de résine sont disposées éventuellement avec des orientations différentes dans la rainure 3,one or more resin prepreg plies 4 are optionally arranged with different orientations in the groove 3,
- un noyau 1 est ensuite placé sur les nappes qui drapent la rainure 3,a core 1 is then placed on the sheets which drape the groove 3,
- enfin, une ou plusieurs nappes 5 préimprégnées de résine viennent former la pièce composite proprement dite,finally, one or more resin prepreg plies form the composite part itself,
- un film de mise sous vide 7 est ensuite placé sur la pièce avec un joint 8 d'étanchéité en périphérie.- A vacuum film 7 is then placed on the workpiece with a seal 8 at the periphery.
Il est précisé que les nappes 4 et 5 peuvent être crues ou cuites et que des feutres de drainage peuvent être interposés entre le film de mise sous vide et la pièce.It is specified that the plies 4 and 5 can be raw or cooked and that drainage felts can be interposed between the evacuation film and the workpiece.
Ensuite, un dispositif de drainage (non représenté sur les figures) permet, par dépression, d'extraire les gaz présents entre l'outillage du moulage et le film étanche, c'est-à-dire les gaz et autres bulles d'air qui sont inclus dans la pièce. Le dispositif de drainage peut venir s'engager sur une ou plusieurs prise de vide 10 pratiquée dans le film de mise sous vide 7.Then, a drainage device (not shown in the figures) allows, by depression, to extract the gases present between the molding tool and the sealed film, that is to say the gases and other air bubbles which are included in the room. The drainage device can engage one or more vacuum taps 10 made in the vacuum film 7.
La figure 2 fait apparaître la problématique de réalisation d'une cavité dans une pièce composite qui est obtenue par moulage sous vide. C'est, en effet, le noyau 1 qui conditionne le bon dimensionnement du raidisseur.Figure 2 shows the problem of making a cavity in a composite part which is obtained by vacuum molding. It is, indeed, the core 1 which conditions the good dimensioning of the stiffener.
Selon l'invention, le noyau présente une structure originale comme cela apparaît à la figure 1.According to the invention, the core has an original structure as shown in FIG.
En effet, le noyau 1 comprend une âme 12 de résine phénolique à l'état de mousse à cellules fermées. La densité de la résine phénolique est de l'ordre de 40 à 100 kg/m3. Un film thermorétractable 13 est enroulé de manière hélicoïdale sur l'âme 12 de mousse phénolique.Indeed, the core 1 comprises a core 12 of phenolic resin in the closed-cell foam state. The density of the phenolic resin is of the order of 40 to 100 kg / m 3 . A heat-shrinkable film 13 is wound helically over the core 12 of phenolic foam.
Une gaine de tissu poreux 14 drainant tel qu'un tube tissé de polyester entoure l'âme 12 et le film thermorétractable 13 sur toute la longueur du noyau.A draining porous fabric sheath such as a woven polyester tube surrounds the core 12 and the heat-shrinkable film 13 over the entire length of the core.
Enfin, la gaine externe 15 de matériau imperméable et à faible coefficient de frottement vient former la peau du noyau. La gaine externe 15 peut être, par exemple, réalisé en FEP.Finally, the outer sheath 15 of impermeable material with a low coefficient of friction forms the skin of the core. The outer sheath 15 may be, for example, made of FEP.
Le noyau 1 se comporte de la manière suivante.Core 1 behaves as follows.
Lors de la mise sous vide, le noyau 1 fournit un contre appui qui permet de former un raidisseur. Il est important que le noyau ne s'écrase pas lors de la dépose des nappes par une machine automatique de drapage ni sous l'effet de la dépression.During the evacuation, the core 1 provides a counter-support which makes it possible to form a stiffener. It is important that the core does not crush when the tablecloths are removed by an automatic draping machine or under the effect of the depression.
Cette tenue mécanique est essentiellement due à l'âme 12 de résine phénolique dont la densité permet de contrecarrer la mise sous vide nécessaire au drainage. C'est également l'âme 12 du noyau qui contribue essentiellement à la précision dimensionnelle et à la reproductivité du raidisseur, qui est formé dans la pièce de composite.This mechanical strength is mainly due to the core 12 of phenolic resin whose density can counteract the vacuum required for drainage. It is also the core core 12 which essentially contributes to the dimensional accuracy and reproducibility of the stiffener, which is formed in the composite part.
Au cours de cette phase, la gaine de tissu poreux a pour fonction de répartir uniformément la pression de l'autoclave.During this phase, the function of the porous fabric sheath is to distribute the pressure of the autoclave uniformly.
Il est à noter que la gaine externe 15 garantit que le noyau ne réagisse pas avec la pièce et donc ne pollue pas la pièce.It should be noted that the outer sheath 15 ensures that the core does not react with the workpiece and therefore does not pollute the workpiece.
Dans le process de fabrication d'une pièce moulée sous vide, la phase de dépression est suivie d'une phase de montée en température sous autoclave qui assure la polymérisation de la résine. Au cours de cette phase qui se produit à une température de l'ordre de 800C à 2000C la mousse phénolique qui constitue l'âme 12 s'affaisse sur elle-même mais ne fond pas.In the manufacturing process of a vacuum molded part, the vacuum phase is followed by a temperature rise phase under autoclave which ensures the polymerization of the resin. During this phase which occurs at a temperature of the order of 80 0 C to 200 0 C the phenolic foam which constitutes the core 12 collapses on itself but does not melt.
L'affaissement de l'âme 12 est favorisé par l'enroulement de film thermorétractable 13.The sagging of the core 12 is favored by the winding of heat-shrinkable film 13.
Au terme de la phase de montée en température, le noyau 1 présente donc une section transversale sensiblement inférieure à celle du raidisseur et peut être extrait en effectuant une traction sur celui-ci.At the end of the temperature rise phase, the core 1 thus has a cross section substantially smaller than that of the stiffener and can be extracted by pulling on it.
L'extraction du noyau 1 est, par ailleurs, facilitée par la gaine externe 15 qui est réalisée dans un matériau à faible coefficient de frottement, par exemple FEP et par la gaine 14 de tissu polyester sur laquelle il est possible d'exercer une traction. Le noyau est ensuite traité pour être éventuellement recyclé.The extraction of the core 1 is, moreover, facilitated by the outer sheath 15 which is made of a material with a low coefficient of friction, for example FEP and by the sheath 14 of polyester fabric on which it is possible to exert traction . The core is then processed for possible recycling.
Il est précisé que sur la figure 1 , les différentes couches qui apparaissent à distance les unes des autres pour faciliter la compréhension sont en réalité directement superposées.It is specified that in Figure 1, the different layers that appear at a distance from each other for ease of understanding are actually directly superimposed.
La figure 3 montre une variante de réalisation d'un raidisseur obtenu par moulage sous vide dans lequel le noyau se trouve sur la face de la pièce opposée à celle qui est en contact de l'outillage de moulage. Dans cette configuration, le noyau 1 selon l'invention se comporte et présente les mêmes avantages que lorsqu'il est mis en œuvre comme cela est illustré à la figure 2.Figure 3 shows an alternative embodiment of a stiffener obtained by vacuum molding in which the core is on the face of the part opposite to that which is in contact with the molding tool. In this configuration, the core 1 according to the invention behaves and has the same advantages as when it is implemented as illustrated in FIG. 2.
Bien entendu, l'invention n'est pas limitée à la forme de réalisation décrite ci-dessus à titre d'exemple non limitatif mais elle en embrasse au contraire toutes les variantes de réalisation.Of course, the invention is not limited to the embodiment described above by way of non-limiting example but it encompasses all variants.
Il est ainsi précisé que le noyau peut présenter une section évolutive. Il est,, par ailleurs, envisagé de réaliser le noyau sur le site de moulage à partir de tronçons de mousse phénolique qui sont mis bout à bout et gainés par le film thermorétractable. It is thus specified that the kernel can present an evolutionary section. It is, moreover, envisaged to make the core on the molding site from sections of phenolic foam which are placed end to end and sheathed by the heat-shrinkable film.

Claims

REVENDICATIONS
1. Noyau destiné à former une cavité dans une pièce en matériau composite stratifié obtenue par un procédé de moulage sous vide comprenant notamment une phase de mise sous vide puis une phase d'élévation de température et de mise sous pression sous autoclave, caractérisé en ce que le noyau (1) présente une âme (12) définissant la géométrie de la cavité formée de la pièce, ladite âme (12) étant réalisée dans un matériau garantissant la géométrie du noyau (1) lors de la phase de mise sous vide de la pièce et permettant la contraction du noyau (1) lors de l'élévation de température de la pièce et l'âme (12) est constituée d'une mousse phénolique à cellule fermée.1. Core intended to form a cavity in a laminated composite material part obtained by a vacuum molding process including in particular a vacuum phase and then a temperature rise and pressurization under autoclave stage, characterized in that that the core (1) has a core (12) defining the geometry of the cavity formed by the part, said core (12) being made of a material guaranteeing the geometry of the core (1) during the vacuum phase of the workpiece and allowing the contraction of the core (1) during the temperature rise of the workpiece and the core (12) consists of a closed cell phenolic foam.
2. Noyau selon la revendication 1, caractérisé en ce qu'il présente une gaine extérieure (15) réalisée dans un matériau étanche et à faible coefficient de frottement.2. Core according to claim 1, characterized in that it has an outer sheath (15) made of a tight material with a low coefficient of friction.
3. Noyau selon la revendication 2, caractérisé en ce que la gaine extérieure (15) est un film de FEP.3. Core according to claim 2, characterized in that the outer sheath (15) is a film of FEP.
4. Noyau selon l'une des revendications 1 à 3, caractérisé en ce que l'âme (12) est entourée d'un film thermorétractable (13).4. Core according to one of claims 1 to 3, characterized in that the core (12) is surrounded by a heat-shrinkable film (13).
5. Noyau selon la revendication 4, caractérisé en ce que le film thermorétractable (13) est constitué d'un enroulement hélicoïdal d'une bande d'un film polyester précontraint.5. Core according to claim 4, characterized in that the heat-shrinkable film (13) consists of a helical winding of a strip of a prestressed polyester film.
6. Noyau selon l'une des revendications 4 à 5, caractérisé en ce qu'une gaine de tissu poreux (14) est superposée sur le film thermorétractable (13).6. Core according to one of claims 4 to 5, characterized in that a porous fabric sheath (14) is superimposed on the heat-shrinkable film (13).
7. Noyau selon la revendication 6, caractérisé en ce que la gaine de tissu poreux (14) est constituée par un tube tissé de polyester.7. Core according to claim 6, characterized in that the porous fabric sheath (14) is constituted by a woven tube of polyester.
8. Noyau selon l'une des revendications 1 à 7, caractérisé en ce que l'âme (12) présente une densité comprise entre 40 et 100 kg/m3.8. Core according to one of claims 1 to 7, characterized in that the core (12) has a density of between 40 and 100 kg / m3.
9. Noyau selon l'une des revendications 1 à 8, caractérisé en ce que l'âme (12) présente au moins un canal.9. Core according to one of claims 1 to 8, characterized in that the core (12) has at least one channel.
10. Noyau selon l'une des revendications 1 à 9, caractérisé en ce qu'il présente une forme allongée de section transversale en trapèze. 10. Core according to one of claims 1 to 9, characterized in that it has an elongate shape of trapezoidal cross section.
PCT/FR2009/000134 2009-02-05 2009-02-05 Core for producing a stiffener in a composite panel WO2010089464A1 (en)

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Publication number Priority date Publication date Assignee Title
WO2015036940A1 (en) * 2013-09-10 2015-03-19 Short Brothers Plc Method of forming a composite member and assembly therefor
FR3044957A1 (en) * 2015-12-10 2017-06-16 Nimitech Etudes MOLDING CORE FOR MANUFACTURING A HOLLOW STIFFENER OF A STRUCTURAL PIECE OF COMPOSITE MATERIAL, AND METHOD FOR MANUFACTURING A STRUCTURAL PIECE OF SELF-ARRAYING COMPOSITE MATERIAL
EP3398759A3 (en) * 2017-05-03 2019-01-23 The Boeing Company Compacted stringer packages
WO2021076777A1 (en) * 2019-10-15 2021-04-22 Mag Aerospace Industries, Llc Hybrid mandrel for composite tanks and tubes
US11014315B2 (en) 2017-05-03 2021-05-25 The Boeing Company Compacted stringer packages

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WO2004011169A2 (en) * 2002-07-30 2004-02-05 Rocky Mountain Composites, Inc. Method of assembling a single piece co-cured structure

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EP0170178A2 (en) * 1984-08-01 1986-02-05 DEUTSCHE FORSCHUNGSANSTALT FÜR LUFT- UND RAUMFAHRT e.V. Removable core for producing tubular structures from fibre composites
US4681724A (en) * 1986-04-28 1987-07-21 United Technologies Corporation Removable irreversibly shrinking male mandrel
JPH04265714A (en) * 1991-02-21 1992-09-21 Kawasaki Heavy Ind Ltd Manufacture of hollow composite member
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WO2004011169A2 (en) * 2002-07-30 2004-02-05 Rocky Mountain Composites, Inc. Method of assembling a single piece co-cured structure

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015036940A1 (en) * 2013-09-10 2015-03-19 Short Brothers Plc Method of forming a composite member and assembly therefor
FR3044957A1 (en) * 2015-12-10 2017-06-16 Nimitech Etudes MOLDING CORE FOR MANUFACTURING A HOLLOW STIFFENER OF A STRUCTURAL PIECE OF COMPOSITE MATERIAL, AND METHOD FOR MANUFACTURING A STRUCTURAL PIECE OF SELF-ARRAYING COMPOSITE MATERIAL
EP3398759A3 (en) * 2017-05-03 2019-01-23 The Boeing Company Compacted stringer packages
US10926435B2 (en) 2017-05-03 2021-02-23 The Boeing Company Foam mandrel assembly
US11014315B2 (en) 2017-05-03 2021-05-25 The Boeing Company Compacted stringer packages
WO2021076777A1 (en) * 2019-10-15 2021-04-22 Mag Aerospace Industries, Llc Hybrid mandrel for composite tanks and tubes

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