EP3084343A1 - Method for determining the thickness of dry textile preforms - Google Patents

Method for determining the thickness of dry textile preforms

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Publication number
EP3084343A1
EP3084343A1 EP14802666.9A EP14802666A EP3084343A1 EP 3084343 A1 EP3084343 A1 EP 3084343A1 EP 14802666 A EP14802666 A EP 14802666A EP 3084343 A1 EP3084343 A1 EP 3084343A1
Authority
EP
European Patent Office
Prior art keywords
thickness
determining
dry textile
dry
calibration
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP14802666.9A
Other languages
German (de)
French (fr)
Inventor
Stéphane AUFFRAY
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Airbus SAS
Original Assignee
Airbus Group SAS
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Filing date
Publication date
Application filed by Airbus Group SAS filed Critical Airbus Group SAS
Publication of EP3084343A1 publication Critical patent/EP3084343A1/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
    • G01B7/06—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness
    • G01B7/10—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using magnetic means, e.g. by measuring change of reluctance
    • G01B7/105—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using magnetic means, e.g. by measuring change of reluctance for measuring thickness of coating

Definitions

  • the present invention relates to the field of characterization of fibrous preforms.
  • the present invention is more particularly applicable to LRI ("Liquid Resin Infusion” type) or RTM ("Resin Transfer Molding") injections.
  • the characterization is carried out after or during the preforming operation of the textile stack.
  • This compaction operation is fundamental since it is dedicated to the transformation of a semi-product without mechanical support (fibers, wicks or layers just joined after the draping operation) into a manipulable preform. Controlling the compaction parameters is the most influential element since it determines the future fiber volume ratio of the object to be injected / polymerized in accordance with the imposed specifications. In addition, too high fiber content can lead to inhomogeneous saturation and potential scrap.
  • the purpose is to precisely define the thickness of the preform and / or the success of the compacting operation by using a device without coupling and without contact dedicated to non-destructive analysis (vocation "health-matter” ) in the environmental products applied to the LRI-VAP process ("Liquid Resin Infusion / Vacuum Assisted Processing").
  • the thickness of the formed preforms is the first parameter of the manufacturing chronology that can alter an injected structure (LRI, RTM or generic).
  • the thickness of a preform conditions its future ability to be saturated with an impregnating liquid during the injection phases and after polymerization its fiber content and its mechanical characteristics. It is therefore appropriate to optimize the compaction protocol after deposition of the dry fibers in order to obtain the target fiber content and a volume homogeneity after impregnation / polymerization of the composite structure.
  • Figure 1 illustrates the different major stages of the development of a preform.
  • the preforms made by automatic deposition consist of wicks (carbon fibers), the draping is done in temperature in order to partially fuse a thermoplastic film (PA V800 for the example) and to ensure sufficient cohesion of the layer on the mold (removal of the first fold) or the following layers (constitution of a stack).
  • the object made has no mechanical strength.
  • the preform consists of fibers, the residual film of thermoplastic and air.
  • the distribution in thickness is random and unmeasurable. The structure is not degraded.
  • phase 2 and 3 starts the vacuum hot compaction operation and under specific environment, a flat caul is used for a homogeneous calibration (simple or curved form).
  • the applied temperature is related to the partial melting and diffusion of the thermoplastic in the carbon layers. It is observed a strong variation of thickness according to the temperature, the conditions of depression, the duration ...
  • This thickness determines the compactness, the compactness determining the fiber content. • In the final phase, it is observed after return to ambient temperature and at atmospheric pressure elastic return (deformability following "z"). The object is now manipulable towards the place or means of injection.
  • the present invention intends to overcome the drawbacks of the prior art by proposing a method for determining the thickness of dry textile preforms by implementing an eddy current inspection.
  • the present invention relates, in its most general sense, to a method for determining the thickness of dry textile preforms, characterized in that it comprises a step of generating eddy currents within a preform. dry textile, a step of calibrating a device capable of taking measurements, a step of acquiring said eddy currents by means of sensors, and a step of determining the thickness of said textile preform.
  • said calibration step is performed by means of a micrometric measurement column.
  • said method comprises a step of calibration by mechanical stop at the edge of the workpiece.
  • said calibration step is carried out after putting under vacuum.
  • the acquisition is multiplexed.
  • said calibration step is performed in real time by a limited number of apparatus on "caul plate”.
  • said calibration step is performed on the surface of a mold.
  • the method of the present invention is applied to end-stage estimates of large preforms at room temperature.
  • the method according to the present invention is applied to the deposition of dry locks.
  • Figure 1 illustrates the different major stages of the development of a preform
  • Figure 2 illustrates the method according to the present invention generally
  • Figure 4 illustrates results obtained with two probes of different nature: one with a strong sampling, and the other with a weak sampling;
  • Figure 5 shows a comparison between "true measurement” at the measurement column and eddy current estimation with thirty-six point calibration and five-point calibration
  • Figure 6 illustrates an application of the method according to the present invention.
  • Eddy currents are currents induced in conductive materials placed in an alternating magnetic field generated by an effector or probe. Any variations in the material in the field of the probe change the intensity and / or the path of the eddy currents, which induces field and impedance variations. As a result, in the bulk material, a resulting induction (or a resultant field) varies in modulus and phase, depending on the thickness traversed or the heterogeneities encountered. The eddy current inspection method is based on the measurement of these variations. In addition to the search for "crack or crack" type defects, eddy currents are used for sorting metallic materials (quenching effect, metallurgical grades, grinding burns, etc.).
  • eddy currents are anecdotal use on composites.
  • the starting assumption is that the conductivity of a dry textile preform is directly proportional to the inter-fiber and inter-layer contact ratio. These contacts must favor the eventual passage of the current.
  • the implantation of an eddy current detection / measurement means has three vocations:
  • Figure 2 illustrates the method according to the present invention generally.
  • the method according to the present invention combines "micrometer measuring column” and standard eddy equipment on simple preform.
  • a probe is integral with the TESA measuring column (direct digital display of the thickness).
  • the measured modules are manually retranslated for each measuring point.
  • a minimalist environment (sandwich A4000 / preform / Thermal imide) allows a correction of the measured thickness, the "0" lift-off being realized on the surface of the mold.
  • Figure 3 shows the acquisition configuration It should be noted that a synchronization of the two acquisitions is possible, RS232 on column and Labview program for the current Foucault smart device. It will also be noted that this environment configuration is also representative of an acquisition under "caul plate”.
  • the automatic removal of fibers is performed on a thermal-imide immobilized on the mold (aluminum). At the end of the layup sequence a fold protects the flat caul from any adhesions during the hot compaction operation.
  • the calibration is performed by combining micrometric measurement and acquisition of the Foucault current module.
  • Figure 4 illustrates results obtained with two probes of different nature: one with a strong sampling, and the other with a weak sampling.
  • the linear regression line obtained makes it possible to evaluate the thickness of two preforms made from two compaction cycles by the use of the solitary probe alone with solicitation parameter.
  • the tolerance range for the micrometric measurement is of the order of 0.3 mm.
  • Figure 5 shows a comparison between "true measurement” at the measurement column and eddy current estimation with thirty-six point calibration and five-point calibration.
  • the method of the present invention is applied to end-stage estimates of large preforms (at room temperature).
  • This variant is dedicated to industrial controls.
  • the number of sensors to be implanted depends on the dimensions of the structure and the internal variability of the stackings (current section consisting of "n" folds and reinforced zones of "n + m” folds.
  • This same principle can be applied during the development of the process window of a new material (thermoplastic film of bonding with different melting point, compressibility of the licks deposited higher or lower, case of a tissue with strong embossing, .. .).
  • This variant is applied during the compacting cycle, the calibration is then carried out in real time by a limited number of apparatus implanted on flat caul (LVDT contact, laser, others). Since the compacting operation causes the preform to overflow as a function of T ° C, -p, duration (loss of thickness for the reasons mentioned), the notion of calibration wedge remains at the end of the cycle. This delivers:
  • This application is dedicated to the validation of the implementation conditions.
  • the method according to the present invention is applied to the deposition of dry locks.
  • This last variant is applicable to the operations of depositing wicks on the mold.
  • the locks or layers are not undone, the use of a thermal stress associated with an application roller can generate adhesion with the mold or layers already deposited.
  • These half-products are not compacted and therefore very highly porous, the eddy currents are insensitive to this porosity but are highly proportionate by the contact rate.
  • the observation takes place dynamically during the removal of the first ply at the last layer, the effector can be mounted directly on the head or on remote plate (case of the removal of thermoplastic high performance at 400 ° C). This device makes it possible to trap any drift during removal (caused by the thermal variation of the dispensing member and the thermal leakage between layers of composite in place).
  • the method according to the present invention finds applications for any thickness verification of RTM ("Resin Transfer”) dry textile preforms. Molding "in Anglo-Saxon terminology). and LRI ("Liquid Resin Infusion” in English terminology):
  • Conductive preforms such as carbon structures (graphite)
  • Non-conductive preforms glass, Kevlar, .
  • the method according to the present invention is applicable in cases of deposit where the thickness by fold is an important parameter.
  • the method according to the present invention is also applicable to draping of "one shot” consolidation thermoplastic (consolidation in finished part directly during the removal operation).
  • Figure 6 illustrates an application of the method according to the present invention.

Abstract

The present invention relates to a method for determining the thickness of dry textile preforms, characterized in that it comprises a step of generating eddy currents within a dry textile preform (10), a step of calibrating a device (20) able to carry out measurements, a step of acquiring said eddy currents by means of sensors (30, 31), and a step of determining the thickness of said textile preform (10).

Description

PROCEDE DE DETERMINATION DE L'EPAISSEUR DE PREFORMES  METHOD FOR DETERMINING THE THICKNESS OF PREFORMS
TEXTILES SECHES  DRY TEXTILES
Domaine de l'invention Field of the invention
La présente invention se rapporte au domaine de la caractérisation de préformes fibreuses. La présente invention s'applique plus particulièrement aux injections de type LRI (« Liquid Resin Infusion » en terminologie anglo-saxonne) ou RTM (« Resin Transfer Molding » en terminologie anglo-saxonne). The present invention relates to the field of characterization of fibrous preforms. The present invention is more particularly applicable to LRI ("Liquid Resin Infusion" type) or RTM ("Resin Transfer Molding") injections.
La caractérisation s'effectue après ou pendant l'opération de préformage de l'empilement textile. Cette opération de compactage est fondamentale puisqu'elle est dédiée à la transformation d'un demi-produit sans maintien mécanique (fibres, mèches ou couches juste jointives après l'opération de drapage) en une préforme manipulable. La maîtrise des paramètres de compactage est l'élément le plus influent puisqu'il détermine le taux volumique de fibres futur de l'objet à injecter/polymériser en conformité avec les spécifications imposées. En outre, un taux de fibres trop élevé peut engendrer une saturation inhomogène donc un rebut potentiel. La finalité est de définir avec précision l'épaisseur de la préforme et/ou donc le succès de l'opération de compactage par l'utilisation d'un dispositif sans couplage et sans contact dédié aux analyses non destructives (vocation « santé-matière ») au sein des produits d'environnement appliquées au procédé LRI-VAP ( « Liquid Resin Infusion / Vacuum Assisted Processing » en terminologie anglo-saxonne). Etat de la technique The characterization is carried out after or during the preforming operation of the textile stack. This compaction operation is fundamental since it is dedicated to the transformation of a semi-product without mechanical support (fibers, wicks or layers just joined after the draping operation) into a manipulable preform. Controlling the compaction parameters is the most influential element since it determines the future fiber volume ratio of the object to be injected / polymerized in accordance with the imposed specifications. In addition, too high fiber content can lead to inhomogeneous saturation and potential scrap. The purpose is to precisely define the thickness of the preform and / or the success of the compacting operation by using a device without coupling and without contact dedicated to non-destructive analysis (vocation "health-matter" ) in the environmental products applied to the LRI-VAP process ("Liquid Resin Infusion / Vacuum Assisted Processing"). State of the art
L'épaisseur des préformes constituées est le premier paramètre de la chronologie de fabrication pouvant altérer une structure injectée (LRI, RTM ou génériques). L'épaisseur d'une préforme conditionne sa faculté future d'être saturée par un liquide d'imprégnation pendant les phases d'injection et après polymérisation son taux de fibres donc ses caractéristiques mécaniques. Il convient donc d'optimiser le protocole de compactage après dépose des fibres sèches afin d'obtenir le taux de fibres visé et une homogénéité volumique après imprégnation/polymérisation de la structure composite. The thickness of the formed preforms is the first parameter of the manufacturing chronology that can alter an injected structure (LRI, RTM or generic). The thickness of a preform conditions its future ability to be saturated with an impregnating liquid during the injection phases and after polymerization its fiber content and its mechanical characteristics. It is therefore appropriate to optimize the compaction protocol after deposition of the dry fibers in order to obtain the target fiber content and a volume homogeneity after impregnation / polymerization of the composite structure.
La Figure 1 illustre les différents stades majeurs de l'élaboration d'une préforme. Les préformes réalisées par dépose automatique sont constituées de mèches (fibres de carbone), le drapage est effectué en température afin de fusionner partiellement un film thermoplastique (PA V800 pour l'exemple) et d'assurer une cohésion suffisante de la couche sur le moule (dépose du premier pli) ou aux couches suivantes (constitution d'un empilage). L'objet réalisé n'a aucune tenue mécanique. Figure 1 illustrates the different major stages of the development of a preform. The preforms made by automatic deposition consist of wicks (carbon fibers), the draping is done in temperature in order to partially fuse a thermoplastic film (PA V800 for the example) and to ensure sufficient cohesion of the layer on the mold (removal of the first fold) or the following layers (constitution of a stack). The object made has no mechanical strength.
• En sortie de dépose (phase 1 ), la préforme est constituée de fibres, du film résiduel de thermoplastique et d'air. La répartition en épaisseur est aléatoire et non mesurable. La structure n'est pas défoisonnée.  • At the removal outlet (phase 1), the preform consists of fibers, the residual film of thermoplastic and air. The distribution in thickness is random and unmeasurable. The structure is not degraded.
• En phase 2 et 3 démarre l'opération de compactage à chaud sous vide et sous environnement spécifique, une caul plate est utilisée pour une calibration homogène (forme simple ou courbe). La température appliquée est en rapport avec la fusion partielle et diffusion du thermoplastique dans les couches de carbone. Il est observé une forte variation d'épaisseur en fonction de la température, des conditions de dépression, de la durée ... • In phase 2 and 3 starts the vacuum hot compaction operation and under specific environment, a flat caul is used for a homogeneous calibration (simple or curved form). The applied temperature is related to the partial melting and diffusion of the thermoplastic in the carbon layers. It is observed a strong variation of thickness according to the temperature, the conditions of depression, the duration ...
Cette épaisseur détermine la compacité, la compacité déterminant le taux de fibres. • En phase finale, il est observé après retour à la température ambiante et à pression atmosphérique un retour élastique (déformabilité suivant « z »). L'objet est désormais manipulable vers le lieu ou moyen d'injection. This thickness determines the compactness, the compactness determining the fiber content. • In the final phase, it is observed after return to ambient temperature and at atmospheric pressure elastic return (deformability following "z"). The object is now manipulable towards the place or means of injection.
On connaît dans l'état de la technique une norme de mesure d'épaisseur (ACI_EDSWCG_ME0820039_v1 Compaction Reforming Tests) dédiée aux applications aéronautiques. Celle-ci met en oeuvre de nombreuses mesures (palmer, comparateur, ...) successives avec corrections itératives des produits d'environnement comme du support (le moule). De par sa complexité, son application sur les structures composites de grandes dimensions simple ou double courbure semble compliquée à mettre en oeuvre. En outre, ceci n'est pas une mesure directe où les incertitudes sont difficilement quantifiables et le cycle de contrôle risque d'être rédhibitoire en production. Cette mesure n'est effectuée que sur une préforme compactée. In the state of the art is known a thickness measurement standard (ACI_EDSWCG_ME0820039_v1 Compaction Reforming Tests) dedicated to aeronautical applications. This one implements many successive measurements (palmer, comparator, ...) with iterative corrections of the environmental products as of the support (the mold). Due to its complexity, its application on large single or double curvature composite structures seems complicated to implement. In addition, this is not a direct measure where uncertainties are difficult to quantify and the control cycle may be prohibitive in production. This measurement is only performed on a compacted preform.
Exposé de l'invention Presentation of the invention
La présente invention entend remédier aux inconvénients de l'art antérieur en proposant un procédé permettant de déterminer l'épaisseur de préformes textiles sèches en mettant en œuvre une inspection par courants de Foucault. The present invention intends to overcome the drawbacks of the prior art by proposing a method for determining the thickness of dry textile preforms by implementing an eddy current inspection.
A cet effet, la présente invention concerne, dans son acception la plus générale, un procédé de détermination de l'épaisseur de préformes textiles sèches, caractérisé en ce qu'il comporte une étape de génération de courants de Foucault au sein d'une préforme textile sèche, une étape d'étalonnage d'un dispositif apte à réaliser des mesures, une étape d'acquisition desdits courants de Foucault au moyen de capteurs, et une étape consistant à déterminer l'épaisseur de ladite préforme textile. Selon un mode de réalisation, ladite étape d'étalonnage est réalisée au moyen d'une colonne de mesure micrométrique For this purpose, the present invention relates, in its most general sense, to a method for determining the thickness of dry textile preforms, characterized in that it comprises a step of generating eddy currents within a preform. dry textile, a step of calibrating a device capable of taking measurements, a step of acquiring said eddy currents by means of sensors, and a step of determining the thickness of said textile preform. According to one embodiment, said calibration step is performed by means of a micrometric measurement column.
Selon une variante, ledit procédé comporte une étape de calibration par butée mécanique en bordure de pièce. According to a variant, said method comprises a step of calibration by mechanical stop at the edge of the workpiece.
Selon un mode de mise en œuvre particulier, ladite étape d'étalonnage est réalisée après mise sous dépression. Selon un mode de réalisation, après ladite étape d'étalonnage, l'acquisition est multiplexée. According to a particular mode of implementation, said calibration step is carried out after putting under vacuum. According to one embodiment, after said calibration step, the acquisition is multiplexed.
Selon une variante, ladite étape d'étalonnage est réalisée en temps réel par un appareillage en nombre limité sur « caul plate ». According to a variant, said calibration step is performed in real time by a limited number of apparatus on "caul plate".
Selon une autre variante, ladite étape d'étalonnage est réalisée à la surface d'un moule. According to another variant, said calibration step is performed on the surface of a mold.
Selon une variante, le procédé selon la présente invention est appliqué aux estimations au stade terminal de grandes préformes à température ambiante. Alternatively, the method of the present invention is applied to end-stage estimates of large preforms at room temperature.
Selon une autre variante, le procédé selon la présente invention est appliqué à la dépose de mèches sèches. According to another variant, the method according to the present invention is applied to the deposition of dry locks.
Brève description des dessins Brief description of the drawings
On comprendra mieux l'invention à l'aide de la description, faite ci-après à titre purement explicatif, d'un mode de réalisation de l'invention, en référence aux Figures dans lesquelles : The invention will be better understood by means of the description, given below purely for explanatory purposes, of one embodiment of the invention, with reference to the figures in which:
• la Figure 1 illustre les différents stades majeurs de l'élaboration d'une préforme ; • la Figure 2 illustre le procédé selon la présente invention de façon générale ; et • Figure 1 illustrates the different major stages of the development of a preform; Figure 2 illustrates the method according to the present invention generally; and
• la Figure 3 représente la configuration d'acquisition ;  • Figure 3 shows the acquisition configuration;
• la Figure 4 illustre des résultats obtenus avec deux sondes de nature différente : l'une avec un échantillonnage fort, et l'autre avec un échantillonnage faible ;  • Figure 4 illustrates results obtained with two probes of different nature: one with a strong sampling, and the other with a weak sampling;
• la Figure 5 représente une comparaison entre « mesure vraie » à la colonne de mesure et estimation par courants de Foucault avec un étalonnage trente-six points et un étalonnage cinq points ; et  • Figure 5 shows a comparison between "true measurement" at the measurement column and eddy current estimation with thirty-six point calibration and five-point calibration; and
• la Figure 6 illustre une application du procédé selon la présente invention.  Figure 6 illustrates an application of the method according to the present invention.
Description détaillée des modes de réalisation de l'invention DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION
Les courants de Foucault sont des courants induits dans les matériaux conducteurs placés dans un champ magnétique alternatif généré par un effecteur ou sonde. Toutes variations affectant le matériau, dans le champ de la sonde, modifient l'intensité et/ou le parcours des courants de Foucault, ce qui induit des variations de champ et d'impédance. Il en découle, que dans le matériau massif, une induction résultante (ou un champ résultant) varie en module et en phase, en fonction de l'épaisseur traversée ou des hétérogénéités rencontrées. La méthode d'inspection par courant de Foucault est fondée sur la mesure de ces variations. Outre la recherche de défauts de type « fissures ou criques», les courants de Foucault sont utilisés pour le tri des matériaux métalliques (effet des trempes, nuances métallurgiques, brûlures de rectification,...). En dehors de la détection de ruptures de mèches carbone de peaux dédiées aux générateurs solaires de satellites, les courants de Foucault sont d'utilisation anecdotique sur composites. Le postulat de départ est que la conductivité d'une préforme textile sèche est directement proportionnée par le taux de contact inter fibres et inter couches. Ces contacts doivent favoriser le passage éventuel du courant. L'implantation d'un moyen de détection/mesure par courant de Foucault (méthode sans contact et sans couplage) possède trois vocations soient : Eddy currents are currents induced in conductive materials placed in an alternating magnetic field generated by an effector or probe. Any variations in the material in the field of the probe change the intensity and / or the path of the eddy currents, which induces field and impedance variations. As a result, in the bulk material, a resulting induction (or a resultant field) varies in modulus and phase, depending on the thickness traversed or the heterogeneities encountered. The eddy current inspection method is based on the measurement of these variations. In addition to the search for "crack or crack" type defects, eddy currents are used for sorting metallic materials (quenching effect, metallurgical grades, grinding burns, etc.). Apart from the detection of broken carbon wicks of skins dedicated to solar satellite generators, eddy currents are anecdotal use on composites. The starting assumption is that the conductivity of a dry textile preform is directly proportional to the inter-fiber and inter-layer contact ratio. These contacts must favor the eventual passage of the current. The implantation of an eddy current detection / measurement means (contactless and non-coupled method) has three vocations:
• Déterminer de l'épaisseur de préforme au stade terminal via un étalonnage pratiqué avec la combinaison d'une colonne de mesure micrométrique et d'un appareillage courants de Foucault (application aux acquisitions manuelles de structures d'encombrement restreint) ; · Détermination de l'épaisseur d'une préforme de grande dimension plane ou formée au stade terminal via un auto étalonnage d'un dispositif assurant la cohérence « mesure vraie » et acquisition courants de Foucault, intégré aux environnements de compactage sous caul plate, captation multipoints assurant un maillage de contrôle à température ambiante et dans les conditions réelles d'injection (la structure est sous dépression en configuration réelle d'injection) ;  • Determine the thickness of the end-stage preform through a calibration performed with the combination of a micrometric measuring column and a standard Foucault equipment (application to manual acquisitions of confined space structures); · Determination of the thickness of a large flat or end-stage shaped preform via self-calibration of a true eddy consistency and eddy current acquisition device, integrated in flat-bottom compaction environments, capture multipoints providing a control mesh at ambient temperature and under the actual injection conditions (the structure is under vacuum in the actual injection configuration);
• Suivre les évolutions du cycle de compactage (T°C, -p, durée,...) et son effet sur l'épaisseur de préforme finale. Cet aspect est directement lié au monitoring de cette opération. La Figure 2 illustre le procédé selon la présente invention de façon générale. • Follow the evolution of the compaction cycle (T ° C, -p, duration, ...) and its effect on the final preform thickness. This aspect is directly related to the monitoring of this operation. Figure 2 illustrates the method according to the present invention generally.
Dans un mode de réalisation, le procédé selon la présente invention combine « colonne de mesure micrométrique » et appareillage courants de Foucault sur préforme simple. Une sonde est solidaire de la colonne de mesure TESA (affichage digital direct de l'épaisseur). Les modules mesurés sont retraduits manuellement pour chaque point de mesure. Un environnement minimaliste (sandwich A4000/préforme/Thermal imide) autorise une correction de l'épaisseur mesurée, le « 0 » lift-off étant réalisé à la surface du moule. La Figure 3 représente la configuration d'acquisition On remarquera qu'une synchronisation des deux acquisitions est possible, RS232 sur colonne et programme Labview pour l'appareil smart courants de Foucault. On remarquera également que cette configuration d'environnement est également représentative d'une acquisition sous « caul plate ». La dépose automatique des fibres s'effectue sur un thermal-imide immobilisé sur le moule (en aluminium). En fin de séquence de drapage un pli protège la caul plate des éventuelles adhérences pendant l'opération de compactage à chaud. In one embodiment, the method according to the present invention combines "micrometer measuring column" and standard eddy equipment on simple preform. A probe is integral with the TESA measuring column (direct digital display of the thickness). The measured modules are manually retranslated for each measuring point. A minimalist environment (sandwich A4000 / preform / Thermal imide) allows a correction of the measured thickness, the "0" lift-off being realized on the surface of the mold. Figure 3 shows the acquisition configuration It should be noted that a synchronization of the two acquisitions is possible, RS232 on column and Labview program for the current Foucault smart device. It will also be noted that this environment configuration is also representative of an acquisition under "caul plate". The automatic removal of fibers is performed on a thermal-imide immobilized on the mold (aluminum). At the end of the layup sequence a fold protects the flat caul from any adhesions during the hot compaction operation.
Dans ce mode de réalisation, l'étalonnage est réalisé en combinant mesure micrométrique et acquisition du module courants de Foucault. In this embodiment, the calibration is performed by combining micrometric measurement and acquisition of the Foucault current module.
La Figure 4 illustre des résultats obtenus avec deux sondes de nature différente : l'une avec un échantillonnage fort, et l'autre avec un échantillonnage faible Figure 4 illustrates results obtained with two probes of different nature: one with a strong sampling, and the other with a weak sampling.
La droite de régression linéaire obtenue permet d'évaluer l'épaisseur de deux préformes réalisées à partir de deux cycles de compactage par l'utilisation de la sonde seule à iso paramètre de sollicitation. The linear regression line obtained makes it possible to evaluate the thickness of two preforms made from two compaction cycles by the use of the solitary probe alone with solicitation parameter.
On observe pour ce mode de réalisation : We observe for this embodiment:
• Des différences d'épaisseur (effet attendu) après deux cycles de compactages distincts « Du comparatif de la méthode de référence (colonne de mesure) par rapport aux résultats issus de la méthode inverse (même avec un étalonnage en cinq points) n'engendre qu'une erreur de 0.18mm et 0.09mm.  • Differences in thickness (expected effect) after two distinct compaction cycles "Comparison of the reference method (measurement column) with results from the inverse method (even with a five-point calibration) does not generate than an error of 0.18mm and 0.09mm.
• Pour cette gamme d'épaisseur, l'intervalle de tolérance pour la mesure micrométrique est de l'ordre de 0.3 mm. • For this thickness range, the tolerance range for the micrometric measurement is of the order of 0.3 mm.
La Figure 5 représente une comparaison entre « mesure vraie » à la colonne de mesure et estimation par courants de Foucault avec un étalonnage trente-six points et un étalonnage cinq points Dans un autre mode de réalisation, le procédé selon la présente invention est appliqué aux estimations au stade terminal de grandes préformes (à température ambiante). Figure 5 shows a comparison between "true measurement" at the measurement column and eddy current estimation with thirty-six point calibration and five-point calibration. In another embodiment, the method of the present invention is applied to end-stage estimates of large preforms (at room temperature).
Puisqu'il est question de mesurer le module de l'impédance de la sonde à un éloignement donné (lift off), dans le cas, il est possible de dédier un nombre de capteurs à l'étalonnage à proximité immédiate d'un calage calibré (cette dimension est l'épaisseur théorique fixée pour un taux de fibres visé). Cette calibration par butée mécanique en bordure de pièce (les préformes constituées sont des ébauches à détourer aux cotes pièces avant injection) détermine un espacement ou lift-off constant et reproductible. L'étalonnage s'effectue après la mise sous dépression (élimination du retour élastique). Après étalonnage, l'acquisition est multiplexée et le traitement des informations liée à la préforme sont disponibles (épaisseur, taux volumique de fibres, épaisseur par pli,...) sous forme de nuage de point ou cartographie. Since it is a question of measuring the module of the impedance of the probe at a given distance (lift off), in the case, it is possible to dedicate a number of sensors to the calibration in the immediate vicinity of a calibrated calibration. (This dimension is the theoretical thickness set for a target fiber rate). This calibration by mechanical stop at the edge of the workpiece (the formed preforms are blanks to be cut to the dimensions of the parts before injection) determines a constant or reproducible spacing or lift-off. Calibration is performed after putting under vacuum (elimination of springback). After calibration, the acquisition is multiplexed and information processing related to the preform are available (thickness, fiber volume ratio, thickness per fold, ...) in the form of a point cloud or mapping.
A ce stade, une sanction acceptable ou non acceptable est délivrée en fin d'opération. At this stage, an acceptable or unacceptable sanction is issued at the end of the operation.
Cette variante est dédiée aux contrôles industriels.  This variant is dedicated to industrial controls.
Le nombre de capteurs à implanter est en fonction des dimensions de la structure et de la variabilité interne des empilages (section courante constituée de « n » plis et zones renforcées de « n+m » plis.  The number of sensors to be implanted depends on the dimensions of the structure and the internal variability of the stackings (current section consisting of "n" folds and reinforced zones of "n + m" folds.
Ce même principe peut être appliqué lors de l'élaboration de la fenêtre procédé d'un nouveau matériau (film thermoplastique de liage à point de fusion différent, compressibilité des mèches déposée supérieure ou inférieure, cas d'un tissu à fort embuvage,...). Cette variante est appliquée pendant le cycle de compactage, l'étalonnage est alors réalisé en temps réel par un appareillage en nombre limité implanté sur caul plate (LVDT contact, laser, autres). Puisque l'opération de compactage engendre un dé foisonnement de la préforme en fonction de T°C, -p, durée (perte d'épaisseur pour les raisons évoquées), la notion de cale de calibration demeure en fin de cycle. Ceci délivre : This same principle can be applied during the development of the process window of a new material (thermoplastic film of bonding with different melting point, compressibility of the licks deposited higher or lower, case of a tissue with strong embossing, .. .). This variant is applied during the compacting cycle, the calibration is then carried out in real time by a limited number of apparatus implanted on flat caul (LVDT contact, laser, others). Since the compacting operation causes the preform to overflow as a function of T ° C, -p, duration (loss of thickness for the reasons mentioned), the notion of calibration wedge remains at the end of the cycle. This delivers:
• Une indication de la compressivité de la préforme en température ;  • An indication of the compressivity of the preform in temperature;
• Un constat quasi-immédiat de pertinence du cycle de préformage mis en oeuvre en conformité avec les spécifications • A near-immediate assessment of the relevance of the preforming cycle implemented in accordance with the specifications
Cette application est dédiée à la validation des conditions de mise en oeuvre. This application is dedicated to the validation of the implementation conditions.
On remarquera qu'en fonction des plages de température visée une correction de la réponse des sondes est impérative. It will be noted that, depending on the target temperature ranges, correction of the response of the probes is imperative.
Dans un autre mode de réalisation, le procédé selon la présente invention est appliqué à la dépose de mèches sèches. In another embodiment, the method according to the present invention is applied to the deposition of dry locks.
Cette dernière variante est applicable aux opérations de dépose de mèches sur le moule. Les mèches ou couches ne sont pas défoisonnées, l'utilisation d'une sollicitation thermique associée à un roller d'application permet de générer une adhérence avec le moule ou les couches déjà déposées. Ces demi-produits ne sont pas compactés donc très fortement poreux, les courants de Foucault son insensibles à cette porosité mais sont fortement proportionnés par le taux de contact. L'observation s'effectue en dynamique pendant la dépose de premier pli à la dernière couche, l'effecteur peut être monté directement sur la tête ou sur platine déportée (cas de la dépose de thermoplastique haute performance à 400°C). Ce dispositif permet de piéger toute dérive lors de la dépose (occasionnée par la variation thermique de l'organe de dépose et les fuites thermiques entres couche de composite en place).  This last variant is applicable to the operations of depositing wicks on the mold. The locks or layers are not undone, the use of a thermal stress associated with an application roller can generate adhesion with the mold or layers already deposited. These half-products are not compacted and therefore very highly porous, the eddy currents are insensitive to this porosity but are highly proportionate by the contact rate. The observation takes place dynamically during the removal of the first ply at the last layer, the effector can be mounted directly on the head or on remote plate (case of the removal of thermoplastic high performance at 400 ° C). This device makes it possible to trap any drift during removal (caused by the thermal variation of the dispensing member and the thermal leakage between layers of composite in place).
L'étalonnage s'effectue à la surface du moule, une correction en température de la réponse des sondes est également requise.  Calibration is performed on the surface of the mold, temperature correction of the probe response is also required.
Le procédé selon la présente invention trouve des applications pour toute vérification d'épaisseur de préformes textiles sèches RTM (« Resin Transfer Molding » en terminologie anglo-saxonne). et LRI (« Liquid Resin Infusion » en terminologie anglo-saxonne) : The method according to the present invention finds applications for any thickness verification of RTM ("Resin Transfer") dry textile preforms. Molding "in Anglo-Saxon terminology). and LRI ("Liquid Resin Infusion" in English terminology):
• Préformes conductrices telles que les structures en carbone (graphite) · Préformes non conductrices (verre, kevlar,...).  • Conductive preforms such as carbon structures (graphite) · Non-conductive preforms (glass, Kevlar, ...).
Le procédé selon la présente invention s'applique dans les cas de dépose où l'épaisseur par pli est un paramètre important. Le procédé selon la présente invention s'applique également aux drapages de thermoplastique de consolidation « one shot » (consolidation en pièce finie directement pendant l'opération de dépose). The method according to the present invention is applicable in cases of deposit where the thickness by fold is an important parameter. The method according to the present invention is also applicable to draping of "one shot" consolidation thermoplastic (consolidation in finished part directly during the removal operation).
La Figure 6 illustre une application du procédé selon la présente invention. Figure 6 illustrates an application of the method according to the present invention.
L'invention est décrite dans ce qui précède à titre d'exemple. Il est entendu que l'homme du métier est à même de réaliser différentes variantes de l'invention sans pour autant sortir du cadre du brevet. The invention is described in the foregoing by way of example. It is understood that the skilled person is able to realize different variants of the invention without departing from the scope of the patent.

Claims

REVENDICATIONS
1 . Procédé de détermination de l'épaisseur de préformes textiles sèches, comportant une étape de génération de courants de Foucault au sein d'une préforme (10) textile sèche, une étape d'étalonnage d'un dispositif (20) apte à réaliser des mesures, une étape d'acquisition desdits courants de Foucault au moyen de capteurs (30, 31 ), et une étape consistant à déterminer l'épaisseur de ladite préforme (10) textile, caractérisé en ce qu'après ladite étape d'étalonnage, l'acquisition est multiplexée. 1. Method for determining the thickness of dry textile preforms, comprising a step of generating eddy currents in a dry textile preform (10), a step of calibrating a device (20) capable of carrying out measurements , a step of acquiring said eddy currents by means of sensors (30, 31), and a step of determining the thickness of said textile preform (10), characterized in that after said calibration step, acquisition is multiplexed.
2. Procédé de détermination de l'épaisseur de préformes textiles sèches selon la revendication 1 , caractérisé en ce que ladite étape d'étalonnage est réalisée au moyen d'une colonne de mesure micrométrique 2. Method for determining the thickness of dry textile preforms according to claim 1, characterized in that said calibration step is performed by means of a micrometric measuring column.
3. Procédé de détermination de l'épaisseur de préformes textiles sèches selon la revendication 1 ou 2, caractérisé en ce qu'il comporte une étape de calibration par butée mécanique en bordure de pièce. 3. Method for determining the thickness of dry textile preforms according to claim 1 or 2, characterized in that it comprises a calibration step by mechanical stop at the edge of the workpiece.
4. Procédé de détermination de l'épaisseur de préformes textiles sèches selon la revendication 1 , 2 ou 3, caractérisé en ce que ladite étape d'étalonnage est réalisée après mise sous dépression. 4. Method for determining the thickness of dry textile preforms according to claim 1, 2 or 3, characterized in that said calibration step is carried out after placing under vacuum.
5. Procédé de détermination de l'épaisseur de préformes textiles sèches selon la revendication 1 , 2 ou 3, caractérisé en ce que ladite étape d'étalonnage est réalisée en temps réel par un appareillage en nombre limité sur « eau I plate ». 5. A method for determining the thickness of dry textile preforms according to claim 1, 2 or 3, characterized in that said calibration step is performed in real time by a limited number of apparatus on "flat water".
6. Procédé de détermination de l'épaisseur de préformes textiles sèches selon la revendication 1 , 2 ou 3, caractérisé en ce que ladite étape d'étalonnage est réalisée à la surface d'un moule. 6. Method for determining the thickness of dry textile preforms according to claim 1, 2 or 3, characterized in that said calibration step is performed on the surface of a mold.
7. Procédé de détermination de l'épaisseur de préformes textiles sèches selon l'une au moins des revendications 1 à 6, caractérisé en ce qu'il est appliqué aux estimations au stade terminal de grandes préformes à température ambiante. 7. Method for determining the thickness of dry textile preforms according to at least one of claims 1 to 6, characterized in that it is applied to the end-stage estimates of large preforms at room temperature.
8. Procédé de détermination de l'épaisseur de préformes textiles sèches selon l'une au moins des revendications 1 à 7, caractérisé en ce qu'il est appliqué à la dépose de mèches sèches. 8. Method for determining the thickness of dry textile preforms according to at least one of claims 1 to 7, characterized in that it is applied to the deposition of dry locks.
EP14802666.9A 2013-12-19 2014-11-25 Method for determining the thickness of dry textile preforms Withdrawn EP3084343A1 (en)

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FR1362999A FR3015658B1 (en) 2013-12-19 2013-12-19 METHOD FOR DETERMINING THE THICKNESS OF DRY TEXTILE PREFORMS
PCT/EP2014/075574 WO2015090864A1 (en) 2013-12-19 2014-11-25 Method for determining the thickness of dry textile preforms

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Citations (1)

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FR2548351A1 (en) * 1983-07-01 1985-01-04 Nippon Kokan Kk METHOD AND APPARATUS FOR NON-CONTACT MEASUREMENT OF A SOLIDIFIED SHELL OF A CAST-METALLIC PIECE

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FR2481445A1 (en) * 1980-04-23 1981-10-30 Thomson Csf Measuring geometrical dimensions of optical fibre - during mfr. automatically to obtain electrical signals for controlling operational parameters of mfr.
US4745809A (en) * 1986-08-12 1988-05-24 Grumman Aerospace Corporation Composite analyzer tester
US20080315462A1 (en) * 2007-06-25 2008-12-25 General Electric Company Systems and methods for monitoring a composite cure cycle
US8240210B2 (en) * 2009-02-18 2012-08-14 General Electric Company Method and system for multimodal inspection with a coordinate measuring device

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FR2548351A1 (en) * 1983-07-01 1985-01-04 Nippon Kokan Kk METHOD AND APPARATUS FOR NON-CONTACT MEASUREMENT OF A SOLIDIFIED SHELL OF A CAST-METALLIC PIECE

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