Patent Publication Number: US-10309043-B2

Title: Installation and a method for fabricating a fiber texture in the form of a strip presenting a profile that varies in cross-section

Description:
CROSS REFERNCE TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of PCT/FR2017/050470 filed Mar. 2, 2017, which in turn claims priority to French Application No. 1651741, filed Mar. 2, 2016. The contents of both applications are incorporated herein by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to using three-dimensional (3D) or multilayer weaving to fabricate fiber reinforcing structures for composite material parts. 
     More particularly, the invention relates to fiber structures that are to form reinforcement in a composite material part that is a body of revolution presenting, in radial section, a profile that varies (varying in shape and/or in thickness), such as for example an aeroengine fan casing. 
     Fiber structures that are to constitute the fiber reinforcement of a composite material part, e.g. such as an aeroengine fan casing, are made by 3D or multilayer weaving in a Jacquard type loom, the weaving consisting in inserting weft yarns to create a pattern between warp yarns. The warp yarns are organized in the harness of the loom as a plurality of layers and columns that are manipulated by the loom so as to enable the weft yarns to be inserted in compliance with the weaving pattern(s) programmed in the loom. The weft yarns are inserted between the warp yarns in columns. 
     In order to enable each column of weft yarns to the inserted while weaving the fiber structure, one or more take-up rollers are used between the outlet of the loom and a storage drum or mandrel onto which the woven fiber texture is wound for subsequent use in forming a fiber preform on an injection mold. The role of this or these take-up rollers located downstream from the loom is to take up the proper lengths of warp yarns after each weft column has been inserted. These rollers have outer surfaces that are covered in a material to which the weaving yarns adhere so as to exert a traction force on the warp yarns. 
     The fiber texture as woven in this way is to be wound onto an injection mold that is formed by a mandrel having a winding surface presenting, in radial section, a profile in relief corresponding to the profile of the part that is to be fabricated. In order to make a fiber texture that is adapted to the varying shape of the injection mold, use is made of a “contour” weaving technique, which consists in taking up different lengths of warp yarns depending on their positions across the width of the fiber texture that is being woven in the form of a strip. For this purpose, the take-up roller(s) present across their axial width a radius that varies so as to define an outer surface having a profile in relief for taking up different lengths of warp yarn as a function of the positions of the yarns across the width of the fiber texture, a greater length of warp yarn being taken up by the portion(s) of a take-up roller that is/are of radius greater than the remainder of the roller. Differential take-up of the warp yarns depends on the sums of the lengths of fiber texture that are in contact with the take-up rollers. The differential take-up performed by the take-up rollers has the effect, in the weaving cell of the loom, of causing the proper lengths of warp yarns to be pulled prior to inserting the next column of weft yarns. 
     However, while the fiber texture is being shaped on a mold prior to injection, it is wound to build up a plurality of layers. On each winding turn, the ratios between the various radii defining the profile in relief changes as a function of the number of layers of fiber texture that have already been wound. The magnitudes of these changes in profile increase with increasing shape and/or thickness ratios in the final part. Unfortunately, the above-described fabrication method is capable only of weaving a fiber texture with a profile in relief that is constant, i.e. matching radii for which the cross-section ratios do not change. While the fiber texture is being wound onto the injection mold, it comes out of register because of the differences between the profile as woven, which is constant over the entire length of the woven texture, and the real profile onto which the texture is being wound, thereby giving rise to losses of tension in certain axial positions in the texture. Such unbalances in tension across the width of the part can give rise to numerous defects such as waves, fibers buckling, pinched fibers, zones of unwanted extra thickness, and fiber volume contents that are out of specification. Such unbalances in tension also make the shaping of the fiber texture by winding more complicated, in particular by causing creases or misalignments to be formed, thereby making the shaping of the fiber texture more arduous and time-consuming. 
     OBJECT AND SUMMARY OF THE INVENTION 
     It is therefore desirable to be able to make 3D or multilayer fiber structures with a profile in relief that varies during weaving of the texture in such a manner as to avoid losses or unbalances of tension in the fiber texture. 
     For this purpose, the invention proposes an installation for fabricating a fiber texture in the form of a strip presenting a profile that varies at least in cross-section, the installation comprising a loom, one or more take-up rollers, and a storage mandrel, each take-up roller and the storage mandrel presenting a radius that varies across its axial width so as to define an outer surface having a profile in relief, the installation being characterized in that at least one take-up roller includes a plurality of sectors releasably fastened on the outer surface of said take-up roller, each sector extending over a fraction of the circumference of the take-up roller and over all or part of the axial width of said take-up roller, each sector also presenting at least one thickness that is determined in such a manner as to modify locally the thickness of the profile in relief of the outer surface of the take-up roller. 
     By making use of sectors that enable the thickness of the profile in relief on the outer surface of one or more take-up rollers to be modified locally during fabrication of a fiber texture of varying shape, the fabrication installation of the invention enables fiber textures to be fabricated in the form of a strip presenting a profile that varies in cross-section in which losses or nonuniformities in tension are significantly reduced. These effects can be seen while winding the texture on the injection mold in order to shape it. Specifically, while being wound on the injection mold, the fiber preform presents few defects (waves, fiber buckling and/or pinching, zones of unwanted extra thickness, fiber volume contents that are out of specification, creases, misalignments, etc.) compared with a fiber texture fabricated in accordance with the prior art in which tension unbalances are greater. This reduces the number of unwanted stops of the winding machine that are usually necessary for the purpose of correcting defects such as creases or collapses of portions of the texture, which defects also require the machine to be reversed and action to be taken by one or more technicians. 
     According to a first particular characteristic of the installation of the invention, each sector presents a thickness that varies in the axial direction. It is thus possible to conserve or to modify the variation in the radius of the take-up roller. 
     According to a second particular characteristic of the installation of the invention, each sector presents an inner surface having a shape corresponding to the portion of the outer surface of profile in relief of the take-up roller on which said sector is fastened. Under such circumstances, the increase in the take-up of warp yarns in contact with the sectors is adjusted relative to the take-up of warp yarns performed at the same location, but on the take-up roller without sectors. 
     According to a third particular characteristic of the installation of the invention, each sector includes a layer of grip material on its outer surface so as to entrain the yarns of the fiber texture in contact with the sectors. 
     According to a fourth particular characteristic of the installation of the invention, at least one sector of the plurality of sectors has an edge that is chamfered so as to avoid putting the preform into contact with a sharp edge on a first sector that has been added to the take-up roller and so as to cause the take-up force on the yarns to increase progressively. 
     According to a fifth particular characteristic of the installation of the invention, it comprises a first take-up roller placed in the proximity of the outlet from the loom, and at least one second take-up roller placed between the first take-up roller and the storage mandrel, the second take-up roller including a plurality of sectors releasably fastened on the outer surface of said second take-up roller, each sector extending over a fraction of the circumference of the second take-up roller and over all or part of the axial width of said second take-up roller, each sector also presenting a thickness that is determined in such a manner as to modify locally the thickness of the profile in relief of the outer surface of the take-up roller. 
     Sectors are thus preferably used with those take-up rollers that are referred to as “reverser” rollers and that present variations in radius that are greater than on the take-up roller(s) that are referred to as “puller” rollers, and that consequently take up greater lengths of warp yarn than the “puller” rollers situated upstream in the winding direction. 
     The invention also provides a method of fabricating a fiber structure in the form of a strip presenting a varying profile in cross-section by three-dimensional or multilayer weaving between a plurality of layers of warp yarns interlinked by weft yarns, the warp yarns being driven at the outlet from the loom by one or more take-up rollers, the fiber texture being wound onto a storage mandrel placed downstream from the take-up rollers, each take-up roller and the storage mandrel presenting across its axial width a radius that varies so as to define an outer surface having a profile in relief, the method being characterized in that, during weaving, it comprises adding a plurality of sectors on the outer surface of at least one take-up roller, each sector extending over a fraction of the circumference of the take-up roller and over all or part of the axial width of said take-up roller, each sector also presenting at least one thickness that is determined in such a manner as to modify locally the thickness of the profile in relief of the outer surface of the take-up roller. 
     According to a first particular characteristic of the method of the invention, each sector extends over a fraction of the circumference of the take-up roller, which fraction is determined as a function of the circumferential fraction of contact between the fiber texture and the outer surface of said take-up roller. 
     According to a second particular characteristic of the method of the invention, each sector presents a thickness that varies in the axial direction. 
     According to a third particular characteristic of the method of the invention, each sector presents an outer surface having a shape corresponding to the portion of the outer surface of profile in relief of the take-up roller on which said sector is fastened. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other characteristics and advantages of the invention appear from the following description of particular embodiments of the invention, given as nonlimiting examples, and with reference to the accompanying drawings, in which: 
         FIG. 1  is a diagrammatic perspective view of a Jacquard type loom; 
         FIG. 2  is a diagrammatic view of an installation for fabricating a fiber texture of varying shape, the installation constituting an embodiment of the invention; 
         FIG. 3  is a diagrammatic perspective view of a take-up roller of the  FIG. 2  installation; 
         FIG. 4  is an exploded a diagrammatic perspective view of the  FIG. 3  take-up roller; 
         FIG. 5  is a diagrammatic view of the take-up roller in radial section on plane V of  FIG. 3 ; 
         FIG. 6  is a diagrammatic view of the take-up roller in axial section on plane VI of  FIG. 5 ; 
         FIGS. 7 to 9  show a sequence of mounting sectors on a take-up roller of the  FIG. 2  installation; and 
         FIGS. 10 to 13  show a sequence of removing sectors from a take-up roller of the  FIG. 2  installation. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The invention applies in general manner to making fiber textures suitable for constituting fiber reinforcement, or “preforms”, for fabricating composite material parts in the form of bodies of revolution presenting, in radial section, a profile that varies and/or a thickness that varies, in particular in a radial section, where a radial section corresponds to a plane defined by the axial direction and by the radial direction of the mold on which the preform is shaped. The parts are obtained by winding a fiber texture on a mold and by injecting a matrix precursor into the shaped fiber texture, with the matrix typically being a resin. 
     The fiber texture of the invention, which is in the form of a strip presenting a profile of varying cross-section, is obtained by three-dimensional weaving or by multilayer weaving. 
     The term “three-dimensional weaving” or “3D weaving” is used herein to mean a weaving technique in which at least some of the weft yarns interlink warp yarns over a plurality of warp layers, or vice versa. The 3D weaving may be of the interlock type, as described in Document WO 2006/136755. 
     The term “multilayer weaving” is used herein to mean 3D weaving with a plurality of warp layers in which the base weave for each layer is equivalent to a conventional 2D weave, such as a weave of plain, satin, or twill type, but including certain points of the weave that interlink warp layers, or vice versa. 
     Fabricating the fiber structure by 3D or multilayer weaving makes it possible to obtain bonding between the layers, and thus to have good mechanical strength for the fiber structure and for the resulting composite material part, and to do so in a single textile operation. 
     In particular, the fiber structure may be woven using yarns made of fibers of carbon, of ceramic such as silicon carbide, of glass, or indeed of aramid. 
       FIG. 1  shows a loom  100  fitted with a Jacquard mechanism  101  supported by a superstructure that is not shown in  FIG. 1 . The loom  100  also has a harness  110  constituted by a harness board  111  and control yarns or “heddles”  113 , each heddle  113  being connected at one end to a control hook  1010  of the Jacquard mechanism  101  and at the other end to a spring of a set of return springs  102  fastened to the structure  103  of the loom  100 . Each heddle  113  has an eyelet  114  through which there passes a warp yarn  201 . The heddles  113  and their associated eyelets  114  extend in a zone in which the heddles  113  and the eyelets  114  are caused to perform substantially vertical reciprocating motion as represented by double headed arrow F. The heddles  113  are subjected to traction forces exerted respectively by the control hooks  1010  and by the return springs  102 . The heddles  113  enable certain warp yarns  201  to be raised in compliance with a defined weaving program. By raising certain warp yarns  201 , the heddles  113  thus create a shed  104  enabling weft yarns  202  to be inserted for 3D or multilayer weaving of a fiber structure  210  in the form of a strip or tape. The warp yarns  201  are organized as a plurality of layers of warp yarns C 1  to C n . 
     The warp yarns  201  are taken from spools arranged on a creel (not shown in  FIG. 1 ) upstream from the Jacquard mechanism  101  of the loom  100 . 
       FIG. 2  shows an installation  10  for fabricating a fiber texture of varying shape in accordance with an implementation of the invention. The installation  10  comprises the above-described loom  100  together with three take-up rollers  300 ,  400 , and  500  arranged downstream from the loom. The box  120  defines the outlet from the loom  100 , i.e. the zone beyond which the warp yarns  201  are no longer woven with weft yarns  202  and corresponding to the closure of the shed  104 . 
     The first take-up roller  300  that is situated closest to the outlet  120  of the loom  100  is said to be a “puller” roller. The take-up roller  300  is driven in a direction of rotation S 300  shown in  FIG. 2 . Across its axial width, it presents a radius that varies so as to define an outer surface  301  having a profile in relief corresponding to the weaving profile specified for the fiber texture  210  so as to have an angle between the warp and weft yarns that is as close as possible to 90°. The outer surface  301  is covered in a material, e.g. a tacking agent, to which the woven yarns adhere so as to exert a traction force on the warp yarns. 
     The other two take-up rollers  400  and  500  that are situated downstream from the first take-up roller  300  are referred to as “reverser” rollers, and they are driven in rotation in respective directions of rotation S 400  and S 500  shown in  FIG. 2 , which directions are both opposite to the direction of rotation the S 300  of the take-up roller  300 . Across their axial widths, the take-up rollers  400  and  500  likewise present varying radius so as to define respective outer surfaces  401  and  501 , each presenting a profile in relief. The variations in a radius on the take-up rollers  400  and  500  are greater than on the take-up roller  300 , with the rollers  400  and  500  taking up greater lengths of warp yarns than the take-up roller  300 . The outer surfaces  401  and  501  are covered in a material, e.g. a tacking agent, to which the woven yarns adhere so as to exert a traction force on the warp yarns. 
     The installation  10  also has a storage drum or mandrel  600 , also referred to as a “take-up” mandrel, that is driven in rotation in the direction of rotation S 600  and that likewise presents across its axial width a radius that varies so as to define an outer surface  601  having a profile in relief corresponding to the weaving profile specified for the fiber texture  210 , in order to limit deformation of the fiber texture  210 . The fiber texture  210  is wound onto the storage mandrel  600  on which it is stored for subsequent use in forming a fiber preform by winding the fiber texture onto an injection mold. 
     In accordance with the invention, at least one take-up roller is provided on its outer surface with a plurality of sectors that are removably attached, e.g. by means of nut-and-bolt type fastener members or by interfitting, each sector extending over a fraction of the circumference of the take-up roller and over all or part of the axial width of said take-up roller. In the presently described example, and as shown in  FIGS. 3 to 6 , the take-up roller  400  that extends axially along an axis X 400  and that has a radius R 400  that varies along the axis X 400  ( FIG. 6 ), has three sectors  410 ,  420 , and  430 , as shown in  FIGS. 3 and 4 . Still in the presently described example, the sectors  410 ,  420 , and  430  present are less than the axial width L 400  of the take-up roller  400 , with axial widths being measured along the direction of the axis of the roller such as the axis X 400  for the follower roller  400 . The sectors  410 ,  420 , and  430  are for placing on a portion  402  of the take-up roller  400  in which the radius R 400  varies across the axial width L 400  so as to define a profile in relief in radial section ( FIG. 6 ). For this purpose, the sectors  410 ,  420 , and  430  have respective inner surfaces  411 ,  421 , and  431  of shape corresponding to the portion  402  of the outer surface  401  of profile in relief of the take-up roller  400  onto which the sectors are to be fastened, and respective outer surfaces  412 ,  422 , and  432  of shape that is determined as a function of the tension adjustment that it is desired to achieve in the portion of the fiber texture that is in contact with the sectors. 
     The outer surfaces  412 ,  422 , and  432  are covered in a layer of grip material (not shown), e.g. a layer of elastomer (rubber), to which the woven yarns adhere so as to exert a traction force on the warp yarns. 
     In this example, the sectors  410 ,  420 , and  430  present respective thicknesses that vary across the axial widths L 410 , L 420 , and L 430  of the sectors  410 ,  420 , and  430 , as shown in  FIG. 6  for the thicknesses E 410  and E 420  of the sectors  410  and  420 . In the presently described example, the variation in the thicknesses of the sectors  410 ,  420 , and  430  mainly follows the variation in the radius R 400 , and consequently the shape of the profile in relief on the portion  402 , so as to modify locally the thickness of the roller  400  while following the profile in relief of the outer surface of the take-up roller in its portion  402 . The sectors can also add extra thickness that is independent of the shape of the profile in relief of the roller. 
     Once fitted with its sectors  410 ,  420 , and  430 , the roller  400  takes up greater lengths of the warp yarns where the warp yarns are in contact with the sectors. 
       FIGS. 7 and 9  show how the sectors  410 ,  420 , and  430  are mounted on the take-up roller  400  during fabrication of the fiber texture  210 . The sectors are fastened on the outer surface of the take-up roller, e.g. by fastener members such as screws that co-operate with tapping formed in the roller (not shown in figures). As shown in  FIG. 7 , a first sector, specifically the sector  410 , is mounted on the fraction of the portion  402  of the roller  400  that is not in contact with the fiber texture  210 . The sector  410 , which is the first to come into contact with the texture  210 , has a first edge  413  that is preferably chamfered towards the outer surface of the roller so as to avoid putting the preform into contact with a sharp edge on the sector and so as to cause the take-up force on the warp yarns to be increased progressively. The take-up roller  400  then continues to be turned in the direction S 400  until a new fraction of the portion  402  of the take-up roller  400  is moved out of the zone of contact with the texture  210 , thereby enabling the second sector  430  to be mounted ( FIG. 8 ). The edge  433  of the sector  430  is placed against the edge  414  of the sector  410 , which is partially in contact with the texture  210 . The take-up roller  400  continues to be turned in the direction S 400  until the last free fraction of the portion  402  of the take-up roller  400  is disengaged from the zone of contact with the texture  210 . The third sector  420  is then mounted on the roller  400  ( FIG. 9 ). The edge  424  of the sector  420  is placed against the chamfered edge  413  of the sector  410 , the edge  424  having a chamfered shape that is complementary to the shape of the edge  413 . The edge  423  of the sector  420  is placed against the edge  434  of the sector  420 . 
     The sectors  410 ,  420 , and  430  are added during fabrication of the fiber texture  210  when it is necessary to take up a greater length of warp yarn, e.g. because the difference between the woven profile and the real profile on which the texture is being wound is such that it can lead to losses of tension at certain axial positions across the texture. 
     The sectors  410 ,  420 , and  430  are removed in like manner, as shown in  FIGS. 10 to 13 . During fabrication of the fiber texture  210 , the first sector that is not in contact with the fiber texture is removed, this sector corresponding in this example to the sector  420  in  FIG. 10 . Thereafter, the other two sectors  410  and  430  are removed one after the other, as shown in  FIGS. 11 to 13  in such a manner as to reduce the thickness or the radius of the portion  402  of the take-up roller  400 . The sector  430 , which is the last sector to be removed, has an edge  434  that preferably presents a chamfer oriented towards the outer surface of the roller so as to avoid putting the preform into contact with a sharp edge on the sector, the edge  423  of the sector  420  presenting a chamfered shape that is complementary to the shape of the edge  434 . 
     Each sector extends over a fraction of the circumference of the roller. It presents a circularly arcuate length, such as the circularly arcuate length A 410  of the sector  410  shown in  FIG. 7 , which is defined as a function of the circularly arcuate length of the portion of the take-up roller  400  that is not in contact with the fiber texture  210 . Consequently, if the fiber texture is in contact with the take-up roller over a relatively short circularly arcuate length, it is possible to use sectors having a relatively long circularly arcuate length, and vice versa. The number of sectors needed to cover the entire circumference of the take-up roller is thus also determined as a function of the circularly arcuate length of the portion of the take-up roller that is not in contact with the fiber texture. 
     Sectors may be used on a single take-up roller, as described above for the roller  400 , or on a plurality of take-up rollers, such as the above-described rollers  300 ,  400 , and  500 , so as to modify locally the thickness of the profile in relief of the outer surface of each take-up roller in question. Nevertheless, the sectors are preferably used with the take-up rollers referred to as “reverser” rollers, since they present variations in radius that are greater than on the take-up roller(s) that are referred to as “puller” rollers, and that consequently take up greater lengths of warp yarn than the “puller” rollers. The “reverser” take-up rollers are placed between the “puller” take-up rollers and the storage mandrel in the installation for fabricating a fiber texture in the form of a strip presenting a cross-section of varying profile. 
     In the context of the invention it is also possible to mount a plurality of sectors on one another so as to increase or decrease progressively the thickness of the profile in relief of the outer surface of any take-up roller. 
     The sectors are made of rigid material or of material that withstands compression well, such as a metal or a plastics material. By way of example, the sectors may be made by molding, by machining, or by 3D printing. 
     By making use of sectors that enable the thickness of the profile in relief on the outer surface of one or more take-up rollers to be modified locally during fabrication of a fiber texture of varying shape, the fabrication installation and method of the invention enable fiber textures to be fabricated of varying shape in which losses or nonuniformities in tension are significantly reduced. The effects of the invention on a fiber texture fabricated with the installation and the method of the invention are visible while the texture is being wound onto the injection mold in order to be shaped. Specifically, while being wound onto the injection mold, the shaped fiber preform presents few defects (waves, fiber buckling and/or pinching, zones of unwanted extra thickness, fiber volume contents that are out of specification, creases, misalignments, etc.) compared with a fiber texture fabricated in accordance with the prior art in which tension unbalances are greater. This reduces the number of unwanted stops of the winding machine that are usually necessary for correcting defects such as creases or collapses of portions of the texture, which defects also require the machine to be reversed and action to be taken by one or more technicians.