FR3133334A1 - Roller for depositing by automatic placement of fibers - Google Patents

Abstract

Roller for depositing by automatic placement of fibers The invention relates to a roller for depositing (1) fibrous structures (7) comprising a non-deformable core (10) centered on the axis of rotation (A) of said roller (1), characterized in that the roller (1) further comprises a deformable outer skin (30) held concentrically around the core (10) by a layer of deformable material (20) interposed between said skin (30) and said core (10) in the absence of application of pressure by the roller (1), the roller (1) further comprising at least one sensor (100) capable of measuring the distance or a variation of the distance between the skin (30) and the core (10). Figure for abstract: Fig. 5

Description

Roller for depositing by automatic fiber placement

The present invention relates to the general field of draping methods by automatic fiber placement.

It is known to produce composite material parts by draping in the form of layers of dry or pre-impregnated fibrous structures. In certain current techniques, draping is carried out manually by an operator. These techniques can result in relatively high part production costs and risks of strata positioning errors. This leads to a certain variability in the mechanical performance of the parts obtained, or even to parts whose mechanical properties are insufficient.

Mechanized solutions have thus been developed to reduce the production cost of these composite material parts, such as the automatic fiber placement technique, also known as AFP for “Automated Fiber Placement”. Such a technique is described in particular in documents FR 3 062 336 A1 and FR 3 072 672 A1. In the prior art, pre-impregnated or dry fibrous structures are draped on a draping surface using an application head conventionally comprising at least one deposition roller. The compaction pressure applied by the deposit roller on the draping surface is generally controlled by means of a cylinder.

However, in the case where the draping surface is discontinuous or uneven, the pressure applied by the deposit roller on the draping surface is generally unsuitable, causing draping defects and altering the quality of the material obtained.

The main aim of the present invention is to enable the manufacture of parts made of composite material by draping using the automatic fiber placement technique, including when the draping surface is discontinuous, irregular or uneven.

For this purpose, the invention proposes a roller for depositing fibrous structures comprising a non-deformable core centered on the axis of rotation of said roller, characterized in that the roller further comprises a deformable outer skin held concentrically around the core by a layer of deformable material interposed between said skin and said core in the absence of application of pressure by the roller, the roller further comprising at least one sensor capable of measuring the distance or a variation of the distance between the skin and the nucleus.

The installation of such a sensor at the level of the deposit roller makes it possible to control the compaction pressure exerted by the roller according to the shape and irregularities of the draping surface. The compaction pressure applied by the roller can therefore be adjusted quickly in the event of irregularities on the draping surface, in order to obtain a good quality part. Indeed, too high or too low a compaction pressure could alter the quality of the draping, the mechanical properties of the part obtained or even the quality of the material.

In particular, the at least one sensor of the roller is capable of measuring the distance or a variation of the distance between the internal surface of the skin and the core.

In particular, the sensor is preferably capable of measuring the distance or the variation in distance between the skin and the core in all the radial directions included in a plane perpendicular to the axis of rotation of the roller.

According to a particular embodiment of the invention, the roller comprises a plurality of sensors spaced along the axis of rotation of said roller.

According to another particular embodiment of the invention, the roller comprises a single sensor comprising several sections distributed along the axis of rotation of the roller, each section being capable of measuring the local distance or a variation of the local distance between the skin and the core.

Thus, in each of the two previous embodiments, the roller comprises a plurality of sectors along its axis of rotation, for which different measurements can be obtained. This characteristic makes it possible to adapt to irregularities in the draping surface not only in the case of variations according to the direction of draping, but also in the case of variation according to the direction of the axis of rotation of the roller.

According to another particular embodiment of the invention, said at least one sensor is a capacitive sensor.

This type of sensor is very robust while being compact, and is therefore easily integrated into a deposit roller.

According to another particular embodiment of the invention, the internal face of the skin in contact with the layer of deformable material is conductive and in which the sensor comprises an internal electrode located in the core.

According to another particular embodiment of the invention, said at least one sensor is a resistive sensor, the layer of deformable material being conductive.

By “conductor”, we mean here “who conducts electricity”.

The invention also proposes an application head for the deposition of fibrous structures by automatic placement of fibers comprising at least one deposition roller according to the invention.

The invention further proposes an installation for applying fibrous structures to a surface by automatic placement of fibers comprising an application head according to the invention, and comprising a device for controlling the force applied to the surface by the head of application according to the distance(s) measured by the sensor(s).

The invention finally proposes a method of manufacturing a part made of composite material comprising the formation of a fibrous preform by deposition on a surface of a plurality of fibrous structures by automatic placement of fibers using the installation according to the invention, and the formation of a matrix in the porosities of the fibrous preform.

According to a particular embodiment of the invention, the surface on which the plurality of fibrous structures is deposited is discontinuous or irregular.

Indeed, the invention is of particular interest when the draping surface is not regular, because it is then necessary to control the compaction pressure applied by the depositing roller as a function of the irregularities of the draping surface.

There is a schematic view of a deposit roller according to the invention.

There is a schematic sectional view of the deposit roller of the according to a plane comprising the axis of rotation of said roller.

There is a schematic sectional view of the deposit roller of Figures 1 and 2 along a plane comprising the axis of rotation of said roller, said roller comprising a capacitive sensor having several sections along the axis of rotation.

There is a schematic sectional view of an installation according to the invention comprising the deposit roller of Figures 1 and 2 along a plane perpendicular to the axis of rotation of said roller.

There is a schematic sectional view of the installation of the according to a plane including the axis of rotation of the deposit roller.

There is a diagram of the closed-loop control of the compaction pressure applied by the roller of Figures 1 to 5 on a draping surface.

Figures 1 and 2 illustrate a deposit roller 1 according to the invention for draping fibrous structures by automatic placement of fibers. This deposition roller 1 is intended to roll, at least in part, on a draping surface in order to deposit fibrous structures on said draping surface. The deposit roller 1 comprises a non-deformable core 10 centered on the axis of rotation A of the roller.

The external surface 10e of the deformable core 10 may be metallic or made of a polymer material. Preferably, the deformable core 10 is made mainly from a foam whose Shore A hardness is preferably between 20 and 70, surrounded by a metal or polymer sheath.

Preferably, the non-deformable core 10 of the deposition roller 1 is an axisymmetric part, and preferably cylindrical or generally cylindrical. Preferably, the core 10 extends over the entire length of the deposit roller 1 defined in the direction of the axis of rotation A of said roller 1. Preferably, the core 10 has fixing elements 11 located on either side and d other of the deposit roller 1 allowing the deposit roller 1 to be fixed to the application head.

The deposition roller 1 also comprises a layer of deformable material 20 present around the core 10, made of a flexible and elastically deformable material. The layer of deformable material 20 can thus be made of an elastomeric material, in particular of silicone or polyurethane, or of a foam whose Shore A hardness is preferably between 20 and 70. The material chosen for the layer of deformable material 20 is preferably identical to the material chosen for the interior of the non-deformable core 10. The material chosen for the layer of deformable material 20 must be adapted to the temperatures experienced by the deposition roller 1.

The deposition roller 1 or more generally the application head may include thermal regulation means making it possible to lower the temperature experienced by the deposition roller 1, for example by injection or circulation of gas. Preferably, the layer of deformable material 20 extends over the entire length of the deposition roller 1 defined in the direction of the axis of rotation A of said roller 1.

The internal surface 20i of the layer of deformable material 20 is preferably directly in contact with the external surface 10e of the core 10. The deposition roller 1 illustrated in Figures 1 and 2 is in a rest state, that is to say say in a state where it exerts no draping or compaction pressure. In this rest state, the layer of deformable material 20 and the non-deformable core 10 are concentric, that is to say that the external surface 20e of the layer of deformable material 20 and the external surface 10e of the core 10 are concentric by relative to the axis of rotation A of the deposit roller 1.

The deposition roller 1 also comprises a deformable outer skin 30 present around the layer of deformable material 20, which is flexible and deformable. The internal surface 30i of the external skin 30 can be made of a material different from the rest of the external skin 30. The external part of the external skin 30 comprising the external surface 30e of said skin 30 can be made of elastomeric material, in particular silicone or polyurethane. Preferably the external part of the outer skin 30 comprising the external surface 30e of said skin 30 is made of the same material as the layer of deformable material 20. The material(s) chosen for the outer skin 30 must be adapted to the temperatures experienced by the deposit roller 1.

The internal surface 30i of the outer skin 30 is preferably directly in contact with the outer surface 20e of the layer of deformable material 20. Preferably, the outer skin 30 extends over the entire length of the deposition roller 1 defined in the direction of the axis of rotation of said roller 1.

The deposit roller 1 illustrated in Figures 1 and 2 is in a rest state, that is to say in a state where it does not exert any draping or compaction pressure. In this rest state, the outer skin 30 and the non-deformable core 10 are concentric, that is to say that the internal and external surfaces 30i and 30e of the outer skin 30 and the external surface 10e of the core 10 are concentric by relative to the axis of rotation A of the deposit roller 1.

The outer skin 30, and in particular its outer surface 30e, can optionally be covered by a non-stick film, for example a PTFE (polytetrafluoroethylene) film conventionally called Teflon film. This film limits adhesion between the deposit roller and the fibrous structures as well as general clogging of the deposit roller. This film must not harm the general deformability of the deposition roller 1, and in particular the deformability of the outer skin 30.

The deposition roller 1 further comprises at least one sensor 100 capable of measuring the distance, or a variation in distance, between the outer skin 30 and the non-deformable core 10 of the deposition roller 1. Preferably, said at least sensor 100 is capable of measuring the distance, or a variation of distance, between the outer skin 30 and the non-deformable core 10 in all radial directions belonging to a plane perpendicular to the axis of rotation A. Preferably, said at least sensor 100 is capable to measure the distance, or a variation of distance, between the internal surface 30i of the external skin 30 and the external surface 10e of the core 10. Preferably, the sensor(s) are capable of measuring locally along the axis of rotation A from the deposit roller 1 the distance, or a variation of distance, between the internal surface 30i of the external skin 30 and the external surface 10e of the core 10.

Preferably, said at least sensor 100 is a capacitive sensor. In this case, as illustrated in the , the internal face 30i of the external skin 30 is conductive and the sensor 100 comprises an internal electrode 110 located in the non-deformable core 10. Said electrode is thus configured to emit an electric field through the layer of deformable material 20, which allows in a well-known manner of measuring the distance between said electrode 110 and the internal face 30i of the external skin 30. The non-deformable core 10 can be constituted by the internal electrode 110, as in the example illustrated in the . If the deposit roller 1 comprises only a single capacitive sensor 100 comprising several sections 101 to 108 distributed along the axis of rotation A of the roller 1, as illustrated in the , the internal electrode 100 comprises several sections 111 to 118 distributed along the axis of rotation A of the roller 1 and electrically isolated from each other. Each section 111 to 118 of the internal electrode 110 belongs respectively to one of the sections 101 to 108 of the sensor 100. The internal face 30i of the external skin 30 can also include the same number of sections distributed along the axis of rotation A of roller 1 and electrically isolated from each other.

The sensor can also be a resistive sensor. In this case, the layer of deformable material 20 is conductive, which makes it possible, in a well-known manner, to measure the distance between said electrode 110 and the internal face 30i of the external skin 30. If the deposition roller only comprises a single resistive sensor comprising several sections distributed along the axis of rotation of the roller, the layer of deformable material 20 comprises several sections distributed along the axis of rotation of the roller and electrically isolated from each other.

Figures 4 and 5 schematically and partially illustrate an installation 1000 according to the invention, comprising the deposition roller 1, for draping fibrous structures 7 on a draping surface S by automatic placement of fibers, in order to form a preform fibrous.

The fibrous structures 7 may be in the form of fibrous strands or layers of fabric. By “wick” is meant a set of fibers or filaments substantially parallel to each other and united into a non-woven strip.

The fibrous structures 7 may be woven or not. The fibrous structures 7 can be dry, that is to say not impregnated with a resin, pre-impregnated or loaded with particles.

The fibrous structures 7 may comprise continuous, long or short fibers. The fibers of the fibrous structures 7 can be ceramic or carbon fibers. Ceramic fibers can be fibers made of non-oxide material, such as silicon carbide (SiC), or of oxide material, such as alumina.

The fibrous structures 7 can be impregnated with a thermoplastic or thermosetting material, which can include solid fillers. The fibrous structures 7 can also be impregnated with a thermoplastic or thermosetting material not comprising solid fillers. The fibrous structures 7 can be impregnated only with an organic phase consisting of a thermoplastic material.

The thermoplastic materials which can impregnate the fibrous structures 7 can be chosen from: polyaryletherketones (PAEK) such as polyetheretherketone (PEEK) and polyetherketoneketone (PEKK), polyetherimides (PEI), polyphenylene sulfide (PPS) and polysulfone ( PSU).

The prior impregnation of the fibrous structures 7 can be carried out by any conventional technique, for example by dipping, by roller application or even by spraying.

The dry or pre-impregnated fibrous structures 7 are intended to be draped on the draping surface S by application head. The draping surface S can be smooth and continuous, for example having the general shape of a plane, cylinder, cone or half-sphere. However, the present invention is particularly interesting in the case of a draping surface S that is discontinuous or uneven, for example for a draping surface S as illustrated in Figures 4 and 5, or for example for the draping of the upper face of a multicellular body of acoustic attenuation panel, in order to form an acoustic opening or closing skin.

The application head of the installation comprises at least one pressure application element in the form of a deposit roller 1, attached to the rest of the application head by hooking elements 2. This or these deposition rollers 1 each apply a compaction pressure P directed towards the draping surface S in order to deposit the fibrous structures 7 on said draping surface S.

During the draping operation, the application head is movable in a draping direction D in order to apply the fibrous structures 7 to a first determined area of the draping surface S. Once the application is carried out on the first zone, the cutting element 5 of the application head cuts the fibrous structures 7 so as to form a first strip 7a of fibrous structures 7 on the first zone of the draping surface S.

The formation of the preform is then continued by advancing the fibrous structures 7 in the application head to the roller by actuation of the conveying element(s) 3. The application head can be moved in order to deposit the fibrous structures 7 on a second zone of the surface S, distinct from the first zone, in order to form a second strip 7b of fibrous structures 7 in the draping direction D.

The production of the preform is then continued by depositing one or more other strips of fibrous structures in the same manner as described above.

During draping, the layer of deformable material 20 and the deformable outer skin 30 deform in order to adapt to the geometry of the draping surface S. The sensor 100 then measures the radial distances or the variations in radial distances between the skin deformable exterior 30 and the non-deformable core 10. These measurements are then processed by a device for controlling the force applied to the surface S, capable of controlling the compaction pressure P applied by the deposition roller(s) 1 on the surface S , so as to apply an optimal compaction pressure P and adapted at each moment to the geometry of the draping surface S present under the deposit roller(s) 1. The application of a compaction pressure P adapted to the irregularities of the surface S makes it possible to obtain a final part having good material quality and satisfactory mechanical properties. Preferably, the hooking elements 2 located on either side of the depositing roller 1 are controlled by a jack, so as to control the axis of rotation A of the roller in translation so as to apply the compaction pressure P desired.

When a plurality of sensors is arranged in the length of the deposit roller 1 along its axis of rotation A, or when the sensor comprises a plurality of sections arranged in the length of the deposit roller 1, it is also possible to adapt the compaction pressure P applied to the draping surface S from measurements of the distance or variation in distance between the outer skin 30 and the core 10 determined at different points along the length of the deposit roller 1 by the sensors or sensor sectors. Preferably, the sensors or sensor sectors are spaced evenly along the axis of rotation of the roller, so as to define sectors of equal size along the length of the roller, as illustrated in Figures 2, 3 and 5.

There represents an example diagram of closed loop control of the compaction pressure P applied by the depositing roller 1 on the draping surface S. Knowing on the one hand the measured position A _m of the axis of rotation A of the roller 1 and on the other hand _the local distances or local variations in distance _measured X _1m , real time the compaction pressure P applied by the roller 1 according to the roughness or irregularities of the draping surface S.

Using a measurement processing device 501, the measured position A _m of the axis of rotation A of the roller 1 is processed to obtain the overall force P _A applied by the roller 1. Using a measurement processing device 502, the local distances or _local variations _{in distance} measured X _{1m ,} … P _Xi applied by roller 1.

The overall force P _A and _the local forces P _{X1 , P} corrected value P _c of compaction pressure to the roller movement controller 505. Preferably, the roller movement controller 505 comprises a jack.

For example, if _the value of the global force _{P A} and the values of the local forces _{P X1} , _P On the contrary, if the value of the global force P _A and the values of the local forces P _X1 , P _X2 , ... P _Xi are greater than the desired value P ₀ , the comparator transmits a lower corrected value P _c .

Likewise, for example, if the value of the global force P _A is less than or equal to the desired value P ₀ , but the values of the local forces P _X1 , P _X2 , … P _Xi are greater than the desired value P ₀ , the comparator transmits a lower corrected value P _c .

Thus, we do not only use the overall force measured to control the compaction pressure P applied, but also a set of local forces measured using the deposit roller 1 of the invention, to allow better draping of the surface. draping S, particularly when it is irregular.

When the draping operation is completed, a matrix is then formed within the fibrous preform thus manufactured. The method of formation of the matrix within the fibrous preform depends in a well-known manner on the constitution of the fibrous structures used for draping.

For example, if the draped fibrous structures were dry or impregnated with a fugitive composition, the matrix can be formed in a well-known manner by infusion or by injection of a resin or a slip into the fibrous preform after removal of the possible fugitive composition. For example, we can cite injection molding techniques called “RTM” for “Resin Transfer Molding”, or injection techniques under flexible membrane. Such a technique is for example described in document FR 3 030 503 A1.

According to another example, if the draped fibrous structures were impregnated with a composition comprising a binder and ceramic or carbon fillers, the matrix can be formed in a well-known manner by sintering said fillers. Such a technique is for example described in document FR 3 072 672 A1.

Of course, the present invention is not simply limited to the embodiments described above but includes all the variants and equivalent means of implementing the methods described above concerning the manufacture of a preform by automatic placement of fibers.

Claims (10)

Roller for depositing (1) fibrous structures (7) comprising a non-deformable core (10) centered on the axis of rotation (A) of said roller (1), characterized in that the roller (1) further comprises an outer skin deformable (30) held concentrically around the core (10) by a layer of deformable material (20) interposed between said skin (30) and said core (10) in the absence of application of a pressure (P) by the roller (1), the roller (1) further comprising at least one sensor (100) capable of measuring the distance or a variation of the distance between the skin (30) and the core (10). Roller (1) according to claim 1, said roller (1) comprising a plurality of sensors spaced along the axis of rotation (A) of the roller (1). Roller (1) according to claim 1, said roller (1) comprising a single sensor (100) comprising several sections (101, 102, 103, 104, 105, 106, 107, 108) distributed along the axis of rotation (A) of the roller (1), each section (101, 102, 103, 104, 105, 106, 107, 108) being capable of measuring the local distance or a variation of the local distance between the skin (30) and the core (10). Roller (1) according to any one of claims 1 to 3, in which said at least one sensor (100) is a capacitive sensor. Roller (1) according to claim 4, in which the internal face (30i) of the skin (30) in contact with the layer of deformable material (20) is conductive and in which the sensor (100) comprises an internal electrode located in the core (10). Roller (1) according to any one of claims 1 to 3, in which said at least one sensor (100) is a resistive sensor, the layer of deformable material (20) being conductive. Application head for the deposition of fibrous structures (7) by automatic placement of fibers comprising at least one deposition roller (1) according to any one of claims 1 to 6. Installation (1000) for applying fibrous structures (7) to a surface (S) by automatic placement of fibers comprising an application head according to claim 7, and comprising a device for controlling the force applied to the surface ( S) by the application head according to the distance(s) measured by the sensor(s) (100). Method for manufacturing a part made of composite material comprising the formation of a fibrous preform by deposition on a surface (S) of a plurality of fibrous structures (7) by automatic placement of fibers using the installation ( 1000) according to claim 8, and the formation of a matrix in the porosities of the fibrous preform. Manufacturing method according to claim 9, in which the surface (S) on which the plurality of fibrous structures (7) is deposited is discontinuous or irregular.