Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B11/00—Making preforms
  • B29B11/14—Making preforms characterised by structure or composition
  • B29B11/16—Making preforms characterised by structure or composition comprising fillers or reinforcement
• • 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
  • B29C70/30—Shaping by lay-up, i.e. applying fibres, tape or broadsheet on a mould, former or core; Shaping by spray-up, i.e. spraying of fibres on a mould, former or core
  • B29C70/38—Automated lay-up, e.g. using robots, laying filaments according to predetermined patterns
  • B29C70/382—Automated fiber placement [AFP]
  • B29C70/384—Fiber placement heads, e.g. component parts, details or accessories
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B15/00—Pretreatment of the material to be shaped, not covered by groups B29B7/00 - B29B13/00
  • B29B15/08—Pretreatment of the material to be shaped, not covered by groups B29B7/00 - B29B13/00 of reinforcements or fillers
  • B29B15/10—Coating or impregnating independently of the moulding or shaping step
  • B29B15/12—Coating or impregnating independently of the moulding or shaping step of reinforcements of indefinite length

Definitions

• the present invention relates to a process for producing preforms by applying a binder to dry fibers and by draping said fibers.
• the present invention also relates to a method of making composite material parts from such preforms.
• Fiber applicator or draping machines are known for automatically draping on draping tools, such as a male or female mold, a broad band formed of one or more fibers, in particular continuous fibers.
• flat ribbon type commonly called wicks, including carbon fibers consisting of a multitude of carbon threads or filaments.
• These machines conventionally comprise a fiber application head comprising guiding means for guiding the fiber or fibers to the draping surface.
• These machines further comprise fiber storage means such as a remote creel, and routing means for conveying fibers from said storage means to the head, and possibly a displacement system of the drape head.
• the means for guiding the head make it possible to bring the fibers in the form of a strip to the draping surface, in which the fibers are arranged in parallel substantially edge to edge.
• these machines conventionally called fiber placement machines, comprise a head equipped with a compacting roller intended to come into contact against the draping surface to apply the strip, the guide means guiding the fibers. fibers to the roll in the form of a band.
• the fibers applied may be fibers pre-impregnated with a thermoplastic or thermosetting polymer, or dry fibers provided with a binder, conventionally called “binder", in order to impart stickiness to the fibers during draping.
• the preform In the case of a lay-up of fibers pre-impregnated with polymer, the preform, called pre-impregnated, obtained after draping, is subsequently cured or polymerized by passing through an oven to obtain a composite material part.
• Dry preforms with binder include a small amount of binder, generally less than 5% by weight, to maintain the cohesion of the preform, while allowing its subsequent impregnation.
• a first technique consists in using fibers already coated with a binder by the supplier of raw material. It is proposed to date such fibers, called powdered and / or veiled, packaged in coils, in which the binders are in the form of powder and / or a veil on one surface or on each surface of the fibers.
• the binder is applied over a wide band of fibers, the web is then slit into several calibrated fibers at the desired width for use in an automatic draping machine.
• This technique has the disadvantage of implementing an expensive product, difficult to use for certain applications, particularly in the automotive field.
• filaments are cut on the fiber edges, which causes significant fouling of the machines.
• a second solution consists in producing a coating of the binder in line on a dry fiber by means of a nozzle, in particular a lip nozzle, for example at the level of the head as described in the patent document FR2882681, or at the level of the creel as described in document FR3016827.
• a nozzle in particular a lip nozzle
• the object of the present invention is to propose an alternative solution to that proposed previously.
• the present invention proposes a process for producing preforms, by draping fibers on a draping surface, comprising applying a liquid or pasty binder to at least one continuous dry fiber, and the draping of said fiber provided with binder by means of a draping head to form a preform, characterized in that the application of binder to a fiber is carried out by means of at least one fiberization nozzle comprising a discharge orifice fed with liquid or pasty binder under pressure, and one or more injection orifices fed with pressurized gas, for example compressed air, so that said nozzle is able to deliver the binder in the form of a spiral filament, the filament turns being deposited on the fiber moving past the nozzle to obtain a fiber provided with binder filaments, said binder filaments providing a bond between the initial fibers, and thus the cohesion of the fiber.
• the binder is applied to dry fibers by means of a fiberization nozzle, the filament turns are deposited on the fiber arranged vis-à-vis the nozzle, in particular in the form of loops more or less regular overlapping.
• the method according to the invention makes it possible to drape dry fibers with binder starting from an inexpensive raw material.
• the use of fiberization nozzles allows a simple and precise binder application.
• the binder filaments form a kind of veil permitting the subsequent infusion of the preform.
• the application of binder according to the invention also makes it possible to ensure an assembly between the two initial fibers forming the fiber, and thus makes it possible to easily form fibers with the desired properties by combining different initial fibers.
• At least one of the initial fibers is a dry unidirectional continuous fiber, for example a carbon fiber, a glass fiber, an aramid fiber, a polyethylene fiber, and / or a natural fiber, such as, for example a flax fiber, formed of a multitude of threads or filaments, for example a fiber of 12 to 50 K in the case of carbon, or a fiber of 1200 to 9600 Tex for glass.
• These unidirectional continuous initial fibers may have widths of one-eighth, one-quarter or one-half inch (1/8 ", 1/4" or 1/2 "), or larger widths greater than half an inch.
• each fiber is formed from two initial fibers of the same nature, for example identical.
• each fiber is formed from two, three or four initial glass fibers of 2400 Tex or 4800 Tex.
• each fiber may be formed of initial fibers of different natures having different properties.
• Each fiber may be formed from unidirectional continuous initial fibers of different natures, for example one or more initial glass fibers and one or more initial carbon fibers.
• One or more second initial fibers may be added to one or more first fibers, in particular continuous unidirectional fibers, to modify one or more properties of the resulting preform, for example to increase its conductivity, or to increase its permeability, the second fiber or fibers initials serving as draining.
• One or more second initial fibers may be added to one or more first fibers, in particular continuous unidirectional, the said second or second initial fibers serving as a filler in the final composite material, for example to conferring volume in the final piece, the said second or second initial fibers being lighter and / or less expensive than the first initial fiber or fibers.
• One or more second initial fibers of polymer material may be added to one or more first fibers, in particular continuous unidirectional, the said second or second initial fibers being intended to form at least partly the polymer matrix of the final piece made of composite material.
• the binder used may comprise one or more thermosetting polymers, for example an epoxy, polyester, vinylester, phenolic, polyimide or bismaleimide polymer, or one or more thermoplastic polymers, for example a polyamide, thermoplastic polyester, polyethersulfone, polyetheretherketone, thermoplastic polyurethane, thermoplastic epoxide, or polyolefin.
• the binder is a thermoplastic copolyester.
• each fiber comprises initial fibers coming from fiber reels unwound from the center of the reel. or from outside the coil, without rotation of the coil, preferably unwound from the center of the coil.
• Obtaining fibers from unwound initial fibers makes it possible to propose a simple design creel.
• Each initial fiber from a reel of unwound fiber turns on itself for each turn unwound from the reel, the initial fiber thus having twisted filaments.
• Each initial fiber can turn on itself on less than one turn length or on more than one turn length.
• the resultant fiber passing at the nozzle may have a constant or non-constant section, particularly when each initial fiber turns on itself over a short fiber length.
• the resulting fiber may have a flat or flattened shape, with two opposite major faces, flat or non-planar, in particular concave, or a generally circular section.
• each fiber is formed from initial fibers from reels of fibers unwound in different directions, so that the initial fibers interlock, the fiber being formed of twisted initial fibers.
• the resulting fiber formed of twisted initial fibers has an elliptical or circular section.
• the filament turns are deposited on the fiber and go around the fiber so that the fiber is coated with binder filaments, ensuring a good maintenance of the initial fibers and different filaments constituting the fiber, facilitating draping operations and to obtain a good quality of draping.
• the use of a dry fiber thus provided with binder facilitates the bonding between two folds of the preform and ultimately improves the cohesion of the resulting preform.
• the method according to the invention makes it possible to apply the binder by means of a single nozzle, and thus simplifies and limits the bulk of the binder application device.
• portions of filament turns are pressed against the fiber in overlapping, thus improving the maintenance of the initial fibers, and therefore the different filaments of the fiber.
• the fiber after passing through the fiberization nozzle, the fiber passes into a calibration and / or calendering system to calibrate the fiber width, and / or compress the fiber thickness, the fiber being subjected to a pressure on each main face.
• the binder filaments applied to the fiber are crushed against the fiber and bind to the filaments constituting the fiber, thus ensuring a good bond of the binder to the fiber.
• This calibration and calendering just after application of the binder makes it possible to obtain a calibrated dry fiber, facilitating the routing of the fibers to the laying head, with little fouling and ensures a good quality of draping.
• the fiber after application of the binder, is provided with binder filaments having a diameter of between 0.02 mm and 0.10 mm, preferably between 0.04 and 0.06 mm.
• the fiber provided with binder filaments comprises 2 to 10% by weight of binder, the preform obtained after draping being able to be subjected to a polymer addition operation.
• the binder application is carried out online, the method comprising the routing of at least one dry fiber from a storage and distribution system to the draping head to drape said fiber on a draping surface, forming a fiber from initial fibers from fiber reels and applying binder to the fiber are performed during draping, the binder application to the fiber being performed in the storage system and distribution or when routing the fiber between the storage system and the head.
• the draping is made from dry fibers and a binder application is carried out in line, as draping progresses, by means of one or more nozzles actuated as a function of the speed as a function of the fibers.
• the application of binder on the fiber or fibers is carried out at the level of the fiber storage and distribution system, said method comprising conveying the binder-filled fiber or fibers to the lay-up head.
• the inventors have noticed that the draping of fibers provided with a binder applied in line allowed the lay-up to be carried out without the need for heating the binder to at the level of the head, the newly applied binder retaining a stickiness which is sufficient to allow said fiber to adhere to the drape surface and / or to one or more binder-bonded fibers previously draped over said drape surface .
• the routing is carried out by means of a flexible tube, in the inner passage from which the fiber passes.
• the fiber provided with the binder is rewound into a reel which will subsequently be loaded into the storage and distribution system of a draping machine to perform the draping operation.
• the method comprises draping strips formed of one or more fibers by means of a lay-up head, preferably provided with an application roll for draping on contact with said strip against the draping surface, the binder application being effected by a plurality of fiberization nozzles, each nozzle applying the binder independently on a single fiber, said nozzles being able to be fed by binding by a common supply system, each nozzle being actuated as a function of the running speed of the fiber moving under said nozzle.
• the fiber provided with the binder passes into a tension limiting system just before it is applied to contact on the application surface by means of an application roller, or compaction roller, in order to limit the tension.
• said tension limiter system comprises at least one cylinder on which the fiber is able to be partially wound, and drive means for rotating said cylinder, said means for The drive is controlled by the control unit of the machine, so that the peripheral speed of the cylinder is greater than the speed of travel of the fiber at the application roller.
• the draping comprises the production of superposed fiber folds in different orientations, folds comprising adjacent fibers, not edge to edge, with a spacing defined between them, in order to facilitate the subsequent infusion of the preform , the gaps between fibers of the folds being arranged to form infusion channels in the thickness of the preform for infusion.
• This spacing between adjacent fibers can be obtained during lay-up of a fiber web, by means of a suitable head and / or of a suitable calibration and calendering system, and / or obtained between two adjacent fiber strips, programming this spacing in the software before draping.
• This spacing is for example between 0.5 and 4 mm, preferably between 1 and 3 mm.
• the present invention also relates to a method for manufacturing composite material parts, characterized in that it comprises
• the heating of the preform for impregnating throughout the preform the polymer (s) forming the binder and / or one or more initial fibers ; and eventually
• the method according to the invention comprises the production of dry preforms, comprising the application of a binder to dry fibers, to form a dry preform comprising less than 10% by weight of binder, preferably less than 5% by weight of binder, said dry preform being thereafter subjected to an impregnation operation of a polymer to form a piece of composite material.
• the method is a process for producing pre-impregnated preforms, comprising the application of a binder formed of one or more polymers to form a pre-impregnated preform comprising at least 30% by weight.
• binder weight preferably at least 40% by weight of binder
• the pre-impregnated preform being subsequently subjected to an impregnation operation, for impregnation of the binder in the fibers in the core, and then a curing operation.
• the preform is formed from fibers each comprising one or more initial initial fibers, in particular unidirectional continuous fibers, and one or more second initial fibers made of polymer material, preferably thermoplastic material, or said second initial fibers. being intended to form at least partly the polymer matrix of the final piece of composite material.
• the preforms will preferably be draped flat at high speeds, and subjected to a forming step to form the preforms to their desired final shape.
• the present invention also relates to a fiber lay-up machine comprising
• a draping head comprising guide means for guiding one or more fibers to a draping surface and preferably an application roll intended to come into contact with the draping surface,
• a storage and distribution system for storing and dispensing at least one continuous fiber
• conveying means for conveying the fiber or fibers from said storage and distribution system to the draping head
• the binder application means comprise at least one fiberization nozzle comprising a discharge orifice fed with liquid or pasty binder under pressure and one or more injection orifices fed with gas under pressure, so that said nozzle is able to deliver the binder in the form of a spiral filament, said nozzle being controlled by a control system in a function of the speed of travel of the fiber opposite the nozzle, said nozzle being disposed upstream of the drape head, preferably in the fiber storage and distribution system, said storage and dispensing means, distribution being able to store initial fibers, identical or different, and to deliver said initial fibers so as to form at least one fiber from at least two initial fibers.
• the nozzle comprises, for example, a chamber supplied with pressurized binder via a supply orifice and provided with a discharge orifice and with a valve movably mounted in the chamber and actuated by actuating means between a closed position to close. the discharge port and an open position for delivering the binder under pressure through its discharge port.
• the machine comprises a system for calibrating and / or calendering the fibers disposed downstream of the application means, for calibrating the fiber in width and / or compressing the fiber in thickness.
• the drape head is equipped with a tension limiter system, upstream of the guide system, able to limit the tension of the fiber or fibers.
• the machine according to the invention can be:
• a fiber placement machine for application in contact with a single fiber or a broad band formed of several fibers, or
• a machine for the non-contact application for example a filament winding machine for the application of a fiber or a strip formed of one or more fibers.
• the head comprises an application roller for draping in contact with the fibers, said machine possibly further comprising a system for moving the draping head.
• the storage and dispensing system is disposed at a distance from the drape head, for example placed on the ground or is mounted on one of the elements of the head displacement system.
• FIG. 1 is a schematic side view of a fiber draping machine according to one embodiment
• FIG. 2 is an enlarged partial schematic view of the creel of the machine of FIG. 1, illustrating the means for applying binder to a fiber formed from three initial fibers;
• FIG. 3 is a schematic partial view of the fiberization nozzle of FIG. 2;
• FIG. 4 is a schematic sectional view of the fiber after application of the binder
• FIG. 5 is a schematic view of the fiber after calibration and calendering
• Figure 6 is a view similar to Figure 3 illustrating the application of binder on a fiber formed of two identical initial superimposed fibers
• FIG. 7 is a schematic sectional view of a fiber formed of a first initial fiber and two second initial fibers, before application of the binder;
• FIG. 8 is a schematic view of a fiber application head according to an alternative embodiment.
• Figure 1 schematically illustrates a fiber placement machine according to the invention, allowing draping in contact with a mold of a strip formed of several fibers.
• the machine comprises a displacement system 1 which is formed here of a poly-articulated arm 11, of the six-axis poly-articulated robot type, known per se, mounted movably on a linear rail 12 fixed to the ground.
• the poly-articulated arm 11 is fixed by its base 112 on a carriage 13 slidably mounted on the rail 12.
• a placement head 2 is mounted at the end wrist 11a of the poly-articulated arm.
• the head comprises, in a manner known per se, guiding means for guiding a plurality of fibers in the form of a strip towards an application roller or compaction roller 21, the compaction roller being able to come into contact with a mold to apply the tape.
• the head further comprises cutting means for individually cutting each fiber, re-routing means for rerouting each fiber that has just been cut, in order to be able to stop and resume at any time. applying a fiber, and choosing the width of the strip, and locking means to block a fiber just cut.
• the machine comprises a drape head as described in the patent document WO2008 / 132299.
• the machine is provided for draping dry fibers, each fiber being formed from three initial fibers, for example glass fibers, packaged in coils 8a, 8b, 8c.
• the storage and dispensing system comprises a creel 3, for receiving dry initial fiber coils, and delivering said fibers independently of one another.
• Each initial fiber coil 8a, 8b, 8c is disposed on a horizontal support 31 so that it can be unwound from the center of the coil.
• the creel is also mounted on a follower carriage 32, disposed on the rail 12 and mechanically connected to the carriage 13 carrying the robot.
• the machine is provided for draping a strip of four fibers 9, the creel comprising twelve bobbins of initial fiber.
• the conveying means for conveying the fibers of the creel to the placement head are here formed of flexible tubes, as described for example in the patent document WO2012 / 160270.
• the tubes are gathered in a bundle, shown schematically under the reference 40 and are placed in the internal passage of a flexible sheath 41, optionally cooled to cool the fibers.
• the machine is equipped with binder application means 5, arranged here at the level of the creel 3, and intended to spray-apply a binder in liquid or pasty form onto each dry fiber formed of three initial fibers 81a, 81b, 81c.
• binder application means 5 arranged here at the level of the creel 3, and intended to spray-apply a binder in liquid or pasty form onto each dry fiber formed of three initial fibers 81a, 81b, 81c.
• the initial fibers for forming a fiber 9 are unwound by the center of the coils, and the coils are here arranged one above the other, so that an initial fiber unwound by the center a lower spool passes through the center of the at least one upper spool, the horizontal supports 31 having apertures to allow these passages.
• the coils are arranged on the supports 31 so that they are diverted in opposite directions, the first coil 8a and the third coil 8c unwinding for example in the clockwise direction, while the second central coil 8b is unwound in the direction counterclockwise.
• the initial fibers unwound coils are passed over a first pulley 33 disposed above the three superimposed coils, then on a second pulley 34 disposed below the first pulley so as to guide a fiber 9 formed of said initial fibers towards the application means 5.
• each fiber passes into a first calibration system 61, for calibrating the fiber to a given section before the application of binder.
• the calibration system makes it possible to form a fiber 9 of generally circular section.
• This calibration system comprises for example for each fiber a frustoconical tube with a circular section which decreases from upstream to downstream, the diameter of the section of the tube at its downstream end corresponding to the desired fiber diameter.
• the application means comprise for each fiber 9 a fibering nozzle 50, the nozzle being connected to a supply system 71 supplying several nozzles by binding under pressure.
• a nozzle is disposed above each fiber 9 formed of three initial fibers.
• Each fiberization nozzle known per se, comprises a chamber 51 with a supply port 52 for its connection to the supply system 71 via a supply line 72, and a discharge port 53.
• a valve 54 is movably mounted in the chamber and is movable between a closed position in which the valve cooperates with the lower part of the chamber, shaped as a seat, to close the discharge orifice, and an open position in which the valve is away from the seat to open the discharge port.
• This valve is controlled in opening and closing by an actuating system comprising a rod 55 which extends substantially axially in the chamber and which carries at its free end the valve 54.
• This rod is adapted to be maneuvered in translation by actuating means 56 for moving the valve between its two positions.
• actuating means for example of electrical or pneumatic type, are controlled by a control system 73, as illustrated by the control line shown schematically under the reference 74.
• the power supply system 71 can feed each nozzle by binding under pressure, at a temperature at which the binder has a viscosity suitable for its application by means of the nozzle.
• the nozzle further comprises injection channels 57 fed with compressed air to form air flows towards the filament exiting the discharge orifice.
• the injection channels have injection orifices 57a distributed at regular angular space around the discharge orifice.
• the nozzle has, for example, eight injection channels.
• the injection channels open onto an annular chamber 58 connected to a source of compressed air 59 via a pipe 59a.
• the injection channels are arranged and oriented so that the binder filament exiting the discharge port is rotated in a circular motion and is drawn and shaped into a spiral, as illustrated in FIGS. reference 92.
• the nozzles apply by projection, without contact between the nozzles and the fibers, the binder on the fibers in the form of filaments.
• Each nozzle is adjusted so that the filament turns are around the fiber, said filament turns having end portions which overlap so that the binder filaments 93 form around the fiber a kind of sheath, such as which schematically illustrated in Figure 4 ensuring the assembly of the initial fibers 8a, 8b, 8c and in particular the maintenance of the various constituent filaments of the fiber.
• the nozzle has a discharge port of about 0.3 mm in diameter.
• the filament exiting the discharge port is drawn by the air streams from the injection channels, so that the fiber is provided with filaments of about 0.05 mm in diameter.
• the control system 73 is connected to sensors to receive information representative of the speed of travel of each fiber.
• Each fiber passes for example on a roller 76 equipped with a connected encoder, via a line shown schematically under the reference 77, the control system to communicate the speed of travel of the fiber.
• the control system controls the opening and closing of the nozzle valve associated with the fiber, as a function of the running speed of said fiber, in order to apply in line the quantity of binder desired as and when the advancement of the fiber and its application by the draping head.
• each fiber Downstream of the application means, each fiber passes into a calibration and calendering system 62 for calibrating the fiber in width and compressing the fiber thickness.
• This system includes for example for each fiber two calendering wheels between which the fiber passes.
• a first wheel 63 is provided with an annular groove of rectangular section, whose width corresponds to the desired fiber width.
• a second wheel 64 is provided with a rib inserted in the groove of the first wheel. The rib inserted into the groove forming a passage whose section corresponds to the desired fiber section.
• FIG. 5 schematically illustrates the fiber section obtained at the outlet of the calibration and calendering system 62.
• the fiber has a flat or flattened shape, the section of the fiber being generally elliptical, with two concave opposite main surfaces 91a, 91b .
• the binder filaments are crushed against the constituent filaments of the fiber, thus ensuring mechanical attachment of the binder filaments to those of the fiber.
• the binder filaments of 0.05 mm in diameter applied by the nozzle have, after calendering, a section of approximately 0.07 mm.
• binder filaments coating the fiber combined with this calendering step provides a calibrated dry fiber, which facilitates the transport of the fiber to the head and in the head, with little fouling, and ensures a quality of draping.
• the creel can also be equipped with a voltage limiter system 42 (FIG 1), as described in the patent document WO2006 / 092514, in which passes the fibers at the output of the application means, in order to limit the voltage in the the fiber before entering the transport tubes.
• a voltage limiter system 42 FIG 1
• the initial fibers placed in the creel are dry glass fibers, consisting of a multitude of glass filaments and a small amount of sizing resin, of the order of 0.2%. by weight, for example glass fibers of 2400 Tex or 4800 Tex.
• each fiber comprises about 5% by weight of binder.
• the binder comprises for example a thermoplastic copolyester.
• the binder may further comprise one or more functional agents or fillers, to give the preform various mechanical and / or electrical properties, for example agents or fillers improving its conduction. electric, permeability for infusion, formability, and / or shock resistance.
• a dry preform can be obtained by draping several superposed plies by means of the draping head, the binder being applied to the fibers as the fibers are applied by the head.
• the draping being done with the binder freshly applied to the fibers, the binder has not completely crystallized, and retains a sticky character. Thus, it is not necessary to heat the binder at the head to ensure the cohesion of the preform.
• the dry preform may be subjected to an infusion or injection operation of an infusion or injection polymer, thermoplastic or thermosetting, then a curing operation to obtain a composite part.
• This curing operation consisting of a so-called consolidation operation in the case of thermoplastic polymer, and a firing in the case of a thermosetting polymer.
• a preform in the form of a plate with the desired dimensions can be obtained by draping several plies.
• the preform can then be subjected to a forming operation, preferably hot, the binder applied to the fibers allowing deformation of the preform and its maintenance in shape.
• the preform may be placed in a forming tool corresponding to the final shape of the desired composite part in which the forming operation will be carried out and then the polymer impregnation operation by injection or infusion.
• the machine is used for producing pre-impregnated preforms comprising at least 40% by weight of binder, the binder then forming the polymer matrix of the final part.
• the preform obtained after draping can then be subjected to a heating and pressurizing operation to impregnate the polymer homogeneously throughout the preform, then a curing operation to obtain a composite part.
• FIG. 6 illustrates another embodiment in which each fiber 109 is formed from two superposed initial fibers 181a, 181b, the initial fibers are for example unwound from fiber reels mounted on creel chucks, motorized or non-motorized. motorized, so that the two initial fibers come flat against each other.
• each dry fiber passes into a first calibration system, making it possible to calibrate the fibers to a desired width before the application of binder.
• This calibration system comprises for example for each fiber a frustoconical tube with a rectangular section which decreases from upstream to downstream, the width of the section of the tube at its downstream end corresponding to the desired fiber width.
• each nozzle is set so that the filament turns on the first main face 109a opposite the nozzle have a width D2 greater than the width D1 of the fiber, such that FIG. 6.
• the filament turns thus projected on the first main face have portions of turn extending beyond the longitudinal edges 109c of the fiber which fold around said edges and press against the second main face 109b of the fiber.
• This application of binder on both sides is obtained by regulating, in particular, the injected air flow, the pressure and the binder temperature in the nozzle and the distance between the nozzle and the fiber.
• the portions of filament turns from a longitudinal edge are superimposed with those from the other longitudinal edge.
• the fiber is thus provided on each main face of binder in the form of filaments, the filaments of a main face extending on the other main face through the longitudinal edges.
• the initial fibers placed in the creel are dry carbon fibers, consisting of a multitude of carbon filaments and a small amount of sizing resin, of the order of 0.2%. in weight.
• Figure 7 illustrates another embodiment in which each fiber 209 before binder application is formed of a first fiber 281a having a flat shape, of generally elliptical section with two concave opposed surfaces, and two second fibers 281b, 281c.
• the first fiber 281a is, for example, a unidirectional continuous dry carbon fiber
• the two second initial fibers 281b, 281c are continuous fibers formed from discontinuous nonwoven filaments.
• the first initial fiber and / or the second fibers may be unwound or unwound from reels of fiber.
• FIG. 8 illustrates a fiber placement head according to an alternative embodiment.
• the placement head 102 comprises an application roll 121, a guide system 122 for guiding the fibers towards the roll in the form of two sheets of fibers 191a 191b arranged in two plane PI, P2 guide, to form a fiber web in which the fibers are disposed substantially edge to edge.
• This guidance system comprises for example guiding channels in which the fibers pass, formed at the assembly interface of a central piece 122a, wedge-shaped, and two side plates (not shown).
• the guidance system is mounted on a support structure (not shown) by which the head is assembled to the wrist of the robot described above. Alternatively, the head is fixed and the draping surface of the mold is adapted to be moved relative to the head to perform draping operations.
• the head further comprises, on either side of the guiding system, cutting means 123, locking means 124 and rerouting means 125.
• the head is equipped with a voltage limiter system 142 disposed upstream of the guiding system 122 in which the fibers entering the head pass in order to limit or even eliminate the tension in the fibers applied by the roller, and thus reduce or even eliminate the compaction force applied by the application roller.
• This tension limiter system is advantageously used in the case of thick preforms, comprising many folds and / or obtained from fibers having a large title, particularly in the case of fiberglass.
• the tension in the fibers at the roller is for example between 0 and 100 g, and the compaction force is between 0 and 10 N / mm, preferably between 0 and 5 N / mm.
• the voltage limiter system is for example of the type described in the patent document WO2006 / 092514 cited above.
• the tension limiter system comprises one or more cylinders 1421 parallel to each other, for example four in number, on which the fibers of the sheet are partially curl. Cylinders are driven positively rotated by drive means.
• the voltage limiter system is mounted on the support structure of the head. The fibers entering the head are directed towards the rolls via return pulleys 126. At the outlet of the rolls, the fibers enter the guiding system 122.
• Said drive means are slaved by the control unit of the machine, so that the peripheral speeds of the rolls are greater than the speeds of travel of the fibers at the level of the application roll, to exert a tensile stress on the fibers, and thus limit the tension of the fibers at the level of the roll of application to a substantially constant value, regardless of the speed of travel of the fibers.
• belts can be mounted around each cylinder, so that a belt comes to be interposed between each fiber and the cylinder, each belt being able to adhere to a fiber and to be driven more or less by the cylinder according to the pressure exerted by the fiber on the belt, said pressure being proportional to the call voltage on the fiber.
• the tension limiter system comprises for each sheet, a single motorized cylinder, with or without a belt.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Robotics (AREA)
• Chemical & Material Sciences (AREA)
• Composite Materials (AREA)
• Moulding By Coating Moulds (AREA)
• Reinforced Plastic Materials (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)

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• 2017
  • 2017-09-07 FR FR1770940A patent/FR3070625B1/fr active Active
• 2018
  • 2018-08-14 WO PCT/FR2018/000206 patent/WO2019048744A1/fr unknown
  • 2018-08-14 EP EP18762121.4A patent/EP3678826A1/de not_active Withdrawn

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